fix(ci): smoke through service namespace (#1)

.gitea/workflows/ci.yml

@@ -21,7 +21,9 @@ jobs:
       - name: Install .NET SDK
         uses: actions/setup-dotnet@67a3573c9a986a3f9c594539f4ab511d57bb3ce9 # v4.3.1
         with:
-          dotnet-version: 10.0.301
+          dotnet-version: |
+            8.0.128
+            10.0.301
 
       - name: Restore locked dependencies
         run: dotnet restore Rendezvous.slnx --locked-mode
@@ -45,6 +47,12 @@ jobs:
       - name: Verify formatting and analyzers
         run: dotnet format Rendezvous.slnx --verify-no-changes --no-restore
 
+      - name: Test dependency-free diagnostic dashboard
+        run: ./scripts/test-diagnostic-dashboard.sh
+
+      - name: Test observability dashboard provisioning
+        run: ./scripts/test-observability-assets.sh
+
       - name: Build
         run: dotnet build Rendezvous.slnx --configuration Release --no-restore
 
@@ -121,7 +129,9 @@ jobs:
       - name: Install .NET SDK
         uses: actions/setup-dotnet@67a3573c9a986a3f9c594539f4ab511d57bb3ce9 # v4.3.1
         with:
-          dotnet-version: 10.0.301
+          dotnet-version: |
+            8.0.128
+            10.0.301
 
       - name: Build deployment diagnostic
         run: |
@@ -140,12 +150,29 @@ jobs:
             rm -f "$secret"
           }
           trap cleanup EXIT
+          umask 077
           install -d -m 0700 deploy/compose/secrets
           openssl rand -out "$secret" 32
+          chmod 0600 "$secret"
+          publisher_credential="$(RENDEZVOUS_SMOKE_LOCAL_KEY="$secret" \
+            ./scripts/mint-local-publisher-credential.sh)"
+          export RENDEZVOUS_PUBLISHER_CREDENTIAL="$publisher_credential"
           chmod 0444 "$secret"
           export RENDEZVOUS_UID=1654
           export RENDEZVOUS_GID=1654
+          port_suffix="$(( ${GITHUB_RUN_ID:-$$} % 10000 ))"
+          export RENDEZVOUS_HTTP_HOST_PORT="$(( 20000 + port_suffix ))"
+          export RENDEZVOUS_UDP_HOST_PORT="$(( 40000 + port_suffix ))"
+          runner_workspace_source="$(docker inspect "$HOSTNAME" | jq -er \
+            --arg destination "$GITHUB_WORKSPACE" \
+            '.[0].Mounts[] | select(.Destination == $destination) | .Source')"
+          export RENDEZVOUS_CONFIG_SOURCE="$runner_workspace_source/deploy/compose/appsettings.Production.json"
+          export RENDEZVOUS_SECRET_SOURCE="$runner_workspace_source/deploy/compose/secrets/signing-key"
           export SOURCE_REVISION_ID="$GITHUB_SHA"
+          smoke_client_image="rendezvous-smoke-client:${GITHUB_SHA}"
+          docker build --file eng/release-builder.Dockerfile \
+            --target release-builder \
+            --tag "$smoke_client_image" .
           docker compose -f "$compose_file" build \
             --build-arg SOURCE_REVISION_ID="$SOURCE_REVISION_ID"
           docker compose -f "$compose_file" up --no-build --detach
@@ -153,19 +180,28 @@ jobs:
           test -n "$container_id"
           test "$(docker inspect --format '{{.Config.User}}' "$container_id")" = "1654:1654"
           test "$(docker inspect --format '{{.HostConfig.ReadonlyRootfs}}' "$container_id")" = "true"
-          test "$(docker inspect --format '{{range .Mounts}}{{if eq .Destination \"/app/appsettings.Production.json\"}}{{.RW}}{{end}}{{end}}' "$container_id")" = "false"
+          test "$(docker inspect --format '{{range .Mounts}}{{if eq .Destination "/app/appsettings.Production.json"}}{{.RW}}{{end}}{{end}}' "$container_id")" = "false"
-          test "$(docker inspect --format '{{range .Mounts}}{{if eq .Destination \"/run/secrets/rendezvous-signing-key\"}}{{.RW}}{{end}}{{end}}' "$container_id")" = "false"
+          test "$(docker inspect --format '{{range .Mounts}}{{if eq .Destination "/run/secrets/rendezvous-signing-key"}}{{.RW}}{{end}}{{end}}' "$container_id")" = "false"
-          for attempt in {1..100}; do
+          docker run --rm \
-            if curl --fail --silent http://127.0.0.1:8080/health/ready >/dev/null 2>&1; then
+            --network "container:${container_id}" \
-              break
+            --user "$(id -u):$(id -g)" \
-            fi
+            --env HOME=/tmp \
-            if (( attempt == 100 )); then
+            --env RENDEZVOUS_SMOKE_HTTP_URL=http://127.0.0.1:8080/ \
+            --env RENDEZVOUS_SMOKE_UDP_ENDPOINT=127.0.0.1:9050 \
+            --env RENDEZVOUS_PUBLISHER_CREDENTIAL \
+            --volume "$runner_workspace_source:/source:ro" \
+            --workdir /source \
+            "$smoke_client_image" \
+            bash -lc '
+              for attempt in {1..180}; do
+                curl --fail --silent "${RENDEZVOUS_SMOKE_HTTP_URL%/}/health/ready" >/dev/null 2>&1 && exec ./scripts/smoke-deployment.sh
+                sleep 1
+              done
+              exit 1
+            ' || {
               docker compose -f "$compose_file" logs rendezvous
               exit 1
-            fi
+            }
-            sleep 0.1
-          done
-          ./scripts/smoke-deployment.sh
           docker compose -f "$compose_file" stop --timeout 40 rendezvous
           test "$(docker inspect --format '{{.State.Running}}' "$container_id")" = "false"
           test "$(docker inspect --format '{{.State.ExitCode}}' "$container_id")" = "0"

.gitea/workflows/release.yml

@@ -20,10 +20,12 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Install pinned .NET SDK
+      - name: Install pinned .NET SDKs
         uses: actions/setup-dotnet@67a3573c9a986a3f9c594539f4ab511d57bb3ce9 # v4.3.1
         with:
-          dotnet-version: 10.0.301
+          dotnet-version: |
+            8.0.128
+            10.0.301
 
       - name: Install pinned Buildx and BuildKit
         uses: docker/setup-buildx-action@e468171a9de216ec08956ac3ada2f0791b6bd435 # v3.11.1
@@ -116,22 +118,48 @@ jobs:
             rm -f "$secret"
           }
           trap cleanup EXIT
+          umask 077
           install -d -m 0700 deploy/compose/secrets
           openssl rand -out "$secret" 32
+          chmod 0600 "$secret"
+          publisher_credential="$(RENDEZVOUS_SMOKE_LOCAL_KEY="$secret" \
+            ./scripts/mint-local-publisher-credential.sh)"
+          export RENDEZVOUS_PUBLISHER_CREDENTIAL="$publisher_credential"
           chmod 0444 "$secret"
           export RENDEZVOUS_UID=1654
           export RENDEZVOUS_GID=1654
+          port_suffix="$(( ${GITHUB_RUN_ID:-$$} % 10000 ))"
+          export RENDEZVOUS_HTTP_HOST_PORT="$(( 20000 + port_suffix ))"
+          export RENDEZVOUS_UDP_HOST_PORT="$(( 40000 + port_suffix ))"
+          runner_workspace_source="$(docker inspect "$HOSTNAME" | jq -er \
+            --arg destination "$GITHUB_WORKSPACE" \
+            '.[0].Mounts[] | select(.Destination == $destination) | .Source')"
+          export RENDEZVOUS_CONFIG_SOURCE="$runner_workspace_source/deploy/compose/appsettings.Production.json"
+          export RENDEZVOUS_SECRET_SOURCE="$runner_workspace_source/deploy/compose/secrets/signing-key"
           export RENDEZVOUS_IMAGE="git.finalfactory.de/heikyu/rendezvous:${RENDEZVOUS_VERSION}"
           docker compose -f deploy/compose/compose.yaml up --detach --no-build
-          for attempt in {1..100}; do
+          container_id="$(docker compose -f deploy/compose/compose.yaml ps -q rendezvous)"
-            curl --fail --silent http://127.0.0.1:8080/health/ready >/dev/null 2>&1 && break
+          test -n "$container_id"
-            if (( attempt == 100 )); then
+          docker run --rm \
+            --network "container:${container_id}" \
+            --user "$(id -u):$(id -g)" \
+            --env HOME=/tmp \
+            --env RENDEZVOUS_SMOKE_HTTP_URL=http://127.0.0.1:8080/ \
+            --env RENDEZVOUS_SMOKE_UDP_ENDPOINT=127.0.0.1:9050 \
+            --env RENDEZVOUS_PUBLISHER_CREDENTIAL \
+            --volume "$runner_workspace_source:/source:ro" \
+            --workdir /source \
+            "$RENDEZVOUS_RELEASE_BUILDER" \
+            bash -lc '
+              for attempt in {1..180}; do
+                curl --fail --silent "${RENDEZVOUS_SMOKE_HTTP_URL%/}/health/ready" >/dev/null 2>&1 && exec ./scripts/smoke-deployment.sh
+                sleep 1
+              done
+              exit 1
+            ' || {
               docker compose -f deploy/compose/compose.yaml logs rendezvous
               exit 1
-            fi
+            }
-            sleep 0.1
-          done
-          ./scripts/smoke-deployment.sh
 
       - name: Scan candidate for high and critical vulnerabilities
         uses: aquasecurity/trivy-action@57a97c7e7821a5776cebc9bb87c984fa69cba8f1 # v0.35.0, post-incident safe SHA

README.md

@@ -84,10 +84,10 @@ directory leases, authenticated join attempts, LiteNetLib mediator, caller-owned
 SDK coordination, typed connection outcomes, thin public-SDK diagnostic client,
 deterministic NAT topology harness, hostile-input controls,
 observability/operator surface, secure single-active Linux deployment, and
-numeric capacity/resilience gates, and reproducible signed release pipeline are
+numeric capacity/resilience gates, reproducible signed release pipeline, consumer
-implemented. Consumer pilots and final production-readiness gates remain in progress;
+pilot integrations, and production-readiness decision framework are implemented.
-participating games must not treat the current repository as a finished production
+Deployment-specific external canaries and optional roadmap follow-ups remain;
-service until those gates land.
+participating games must not treat a checkout alone as production approval.
 
 The ratified v1 boundaries, trust decisions, privacy rules, safety budgets, and
 threat model are indexed in [the architecture documentation](docs/architecture/README.md).
@@ -100,6 +100,8 @@ defined in [hostile-input and overload protection](docs/security/abuse-protectio
 Health semantics, bounded telemetry, alerting, audit privacy, and the authenticated
 operator controls are defined in the
 [observability and operator runbook](docs/operations/observability-and-operator-runbook.md).
+The optional public session diagnostic and the private provisioned Grafana stack
+are described in [diagnostic dashboards](docs/operations/diagnostic-dashboards.md).
 Concrete detect/contain/recover/verify procedures are in the
 [incident and change runbooks](docs/operations/incident-runbooks.md).
 The pinned non-root container, production topology, graceful drain, Linux
@@ -113,6 +115,9 @@ signing, staged promotion, rollback, and migration are defined in
 [releases and compatibility](docs/releases/README.md).
 The scriptable host/browser/join diagnostic and its stable automation contract are
 documented in the [TestClient integration guide](docs/integration/test-client.md).
+Optional bounded SSE deltas, reconnect/reset semantics, proxy requirements, and
+polling fallback are documented in
+[live session-list updates](docs/integration/live-session-updates.md).
 The package, gameplay-socket, host-admission, provisioning, metadata, key rotation,
 versioning, and secure rollout seams are in the
 [game integration guide](docs/integration/sdk-seams.md).
@@ -129,8 +134,10 @@ external-network procedure are in
 
 ## Development
 
-The repository pins .NET SDK 10.0.301. From a clean clone, run the same gates as
+The repository pins .NET SDK 10.0.301. The full process-test gate also requires
-CI from the repository root:
+the .NET 8 runtime because the public TestClient deliberately targets `net8.0`;
+CI installs SDK 8.0.128 to supply the pinned 8.0.28 runtime. From a clean clone,
+run the same gates as CI from the repository root:
 
 ```bash
 dotnet restore Rendezvous.slnx --locked-mode

deploy/compose/appsettings.Production.json

@@ -14,6 +14,29 @@
       "ListenAddress": "0.0.0.0",
       "Port": 9050
     },
+    "Diagnostics": {
+      "Enabled": false,
+      "PollIntervalSeconds": 10,
+      "MaximumRenderedSessions": 100,
+      "Scopes": [
+        {
+          "GameId": "space-game",
+          "EnvironmentId": "smoke",
+          "ProtocolVersions": [1, 2],
+          "Regions": ["local"]
+        },
+        {
+          "GameId": "unscouted",
+          "EnvironmentId": "smoke",
+          "ProtocolVersions": [1],
+          "Regions": ["local"]
+        }
+      ]
+    },
+    "Metrics": {
+      "Enabled": false,
+      "BearerTokenSecretReference": "file:/run/secrets/rendezvous-metrics-token"
+    },
     "AbuseProtection": {
       "TrustedProxyAddresses": ["127.0.0.1"],
       "OperatorAllowedAddresses": ["127.0.0.1"]

deploy/compose/compose.yaml

@@ -27,9 +27,11 @@ services:
     environment:
       ASPNETCORE_ENVIRONMENT: Production
       ASPNETCORE_HTTP_PORTS: "8080"
+      Rendezvous__Diagnostics__Enabled: "${RENDEZVOUS_DIAGNOSTICS_ENABLED:-false}"
+      Rendezvous__Metrics__Enabled: "${RENDEZVOUS_METRICS_ENABLED:-false}"
     volumes:
-      - ./appsettings.Production.json:/app/appsettings.Production.json:ro
+      - ${RENDEZVOUS_CONFIG_SOURCE:-./appsettings.Production.json}:/app/appsettings.Production.json:ro
-      - ./secrets/signing-key:/run/secrets/rendezvous-signing-key:ro
+      - ${RENDEZVOUS_SECRET_SOURCE:-./secrets/signing-key}:/run/secrets/rendezvous-signing-key:ro
     ports:
-      - "127.0.0.1:8080:8080/tcp"
+      - "127.0.0.1:${RENDEZVOUS_HTTP_HOST_PORT:-8080}:8080/tcp"
-      - "9050:9050/udp"
+      - "${RENDEZVOUS_UDP_HOST_PORT:-9050}:9050/udp"

deploy/observability/compose.yaml

@@ -0,0 +1,71 @@
+services:
+  rendezvous:
+    environment:
+      Rendezvous__Metrics__Enabled: "true"
+    volumes:
+      - ../observability/secrets/rendezvous-metrics-token:/run/secrets/rendezvous-metrics-token:ro
+
+  prometheus:
+    image: prom/prometheus:v3.13.1@sha256:3c42b892cf723fa54d2f262c37a0e1f80aa8c8ddb1da7b9b0df9455a35a7f893
+    user: "65534:65534"
+    read_only: true
+    init: true
+    cap_drop:
+      - ALL
+    security_opt:
+      - no-new-privileges:true
+    pids_limit: 128
+    mem_limit: 512m
+    cpus: 1.0
+    restart: unless-stopped
+    command:
+      - --config.file=/etc/prometheus/prometheus.yml
+      - --storage.tsdb.path=/prometheus
+      - --storage.tsdb.retention.time=15d
+    volumes:
+      - ../observability/prometheus/prometheus.yml:/etc/prometheus/prometheus.yml:ro
+      - ../observability/secrets/rendezvous-metrics-token:/run/secrets/rendezvous-metrics-token:ro
+      - prometheus-data:/prometheus
+    depends_on:
+      - rendezvous
+
+  grafana:
+    image: grafana/grafana:13.1.0@sha256:121a7a9ece6dc10b969f1f96eed64b4f07dfac0d0b8abc070f7cb83bbde86f63
+    user: "472:472"
+    read_only: true
+    init: true
+    cap_drop:
+      - ALL
+    security_opt:
+      - no-new-privileges:true
+    pids_limit: 128
+    mem_limit: 512m
+    cpus: 1.0
+    restart: unless-stopped
+    environment:
+      GF_ANALYTICS_REPORTING_ENABLED: "false"
+      GF_ANALYTICS_CHECK_FOR_UPDATES: "false"
+      GF_PLUGINS_PREINSTALL_DISABLED: "true"
+      GF_PLUGINS_PREINSTALL_AUTO_UPDATE: "false"
+      GF_SECURITY_ADMIN_USER: "rendezvous-admin"
+      GF_SECURITY_ADMIN_PASSWORD__FILE: /run/secrets/grafana-admin-password
+      GF_USERS_ALLOW_SIGN_UP: "false"
+      GF_AUTH_ANONYMOUS_ENABLED: "false"
+      GF_SERVER_DOMAIN: localhost
+      GF_SERVER_ROOT_URL: http://localhost:3000
+    tmpfs:
+      - /tmp:rw,noexec,nosuid,nodev,size=32m,uid=472,gid=472,mode=0700
+    volumes:
+      - ../observability/grafana/provisioning/datasources:/etc/grafana/provisioning/datasources:ro
+      - ../observability/grafana/provisioning/dashboards:/etc/grafana/provisioning/dashboards:ro
+      - ../observability/grafana/dashboards:/var/lib/grafana/dashboards:ro
+      - ../observability/secrets/grafana-admin-password:/run/secrets/grafana-admin-password:ro
+      - grafana-data:/var/lib/grafana
+    ports:
+      - "127.0.0.1:3000:3000/tcp"
+    depends_on:
+      - prometheus
+
+volumes:
+  prometheus-data:
+  grafana-data:

deploy/observability/grafana/dashboards/rendezvous-overview.json

@@ -0,0 +1,292 @@
+{
+  "annotations": {"list": []},
+  "description": "Privacy-safe operational view of the single-active Rendezvous service. Capacity percentages use the approved 25,000 listing and 10,000 active-attempt launch envelope.",
+  "editable": false,
+  "fiscalYearStartMonth": 0,
+  "graphTooltip": 1,
+  "id": null,
+  "links": [],
+  "liveNow": false,
+  "panels": [
+    {
+      "id": 1,
+      "title": "Service",
+      "description": "Prometheus can authenticate to and scrape the Rendezvous process.",
+      "type": "stat",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 4, "w": 4, "x": 0, "y": 0},
+      "fieldConfig": {"defaults": {"mappings": [{"options": {"0": {"color": "red", "text": "DOWN"}, "1": {"color": "green", "text": "UP"}}, "type": "value"}], "thresholds": {"mode": "absolute", "steps": [{"color": "red", "value": null}, {"color": "green", "value": 1}]}}, "overrides": []},
+      "options": {"colorMode": "background", "graphMode": "none", "justifyMode": "center", "orientation": "auto", "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": false}, "textMode": "auto", "wideLayout": true},
+      "targets": [{"editorMode": "code", "expr": "up{job=\"rendezvous\"}", "legendFormat": "Rendezvous", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 2,
+      "title": "Store",
+      "type": "stat",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 4, "w": 4, "x": 4, "y": 0},
+      "fieldConfig": {"defaults": {"mappings": [{"options": {"0": {"color": "red", "text": "UNAVAILABLE"}, "1": {"color": "green", "text": "AVAILABLE"}}, "type": "value"}], "thresholds": {"mode": "absolute", "steps": [{"color": "red", "value": null}, {"color": "green", "value": 1}]}}, "overrides": []},
+      "options": {"colorMode": "background", "graphMode": "none", "justifyMode": "center", "orientation": "auto", "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": false}, "textMode": "auto", "wideLayout": true},
+      "targets": [{"editorMode": "code", "expr": "rendezvous_store_available", "legendFormat": "Store", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 3,
+      "title": "Drain",
+      "type": "stat",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 4, "w": 4, "x": 8, "y": 0},
+      "fieldConfig": {"defaults": {"mappings": [{"options": {"0": {"color": "green", "text": "ACCEPTING"}, "1": {"color": "orange", "text": "DRAINING"}}, "type": "value"}], "thresholds": {"mode": "absolute", "steps": [{"color": "green", "value": null}, {"color": "orange", "value": 1}]}}, "overrides": []},
+      "options": {"colorMode": "background", "graphMode": "none", "justifyMode": "center", "orientation": "auto", "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": false}, "textMode": "auto", "wideLayout": true},
+      "targets": [{"editorMode": "code", "expr": "rendezvous_store_draining", "legendFormat": "Drain", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 4,
+      "title": "Listings",
+      "description": "Percentage of the approved 25,000-listing single-process envelope.",
+      "type": "gauge",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 4, "w": 6, "x": 12, "y": 0},
+      "fieldConfig": {"defaults": {"max": 100, "min": 0, "unit": "percent", "thresholds": {"mode": "absolute", "steps": [{"color": "green", "value": null}, {"color": "orange", "value": 70}, {"color": "red", "value": 90}]}}, "overrides": []},
+      "options": {"minVizHeight": 75, "minVizWidth": 75, "orientation": "auto", "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": false}, "showThresholdLabels": false, "showThresholdMarkers": true, "sizing": "auto"},
+      "targets": [{"editorMode": "code", "expr": "100 * rendezvous_store_active_listings / 25000", "legendFormat": "Listings", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 5,
+      "title": "Join attempts",
+      "description": "Percentage of the approved 10,000 active-attempt single-process envelope.",
+      "type": "gauge",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 4, "w": 6, "x": 18, "y": 0},
+      "fieldConfig": {"defaults": {"max": 100, "min": 0, "unit": "percent", "thresholds": {"mode": "absolute", "steps": [{"color": "green", "value": null}, {"color": "orange", "value": 70}, {"color": "red", "value": 90}]}}, "overrides": []},
+      "options": {"minVizHeight": 75, "minVizWidth": 75, "orientation": "auto", "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": false}, "showThresholdLabels": false, "showThresholdMarkers": true, "sizing": "auto"},
+      "targets": [{"editorMode": "code", "expr": "100 * rendezvous_store_active_attempts / 10000", "legendFormat": "Attempts", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 6,
+      "title": "HTTP request rate by operation",
+      "description": "Registration, renewal, browse, and join issuance appear as bounded operation names.",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 8, "w": 8, "x": 0, "y": 4},
+      "fieldConfig": {"defaults": {"unit": "reqps"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (operation) (rate(rendezvous_http_requests_total[5m]))", "legendFormat": "{{operation}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 7,
+      "title": "HTTP p95 latency",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 8, "w": 8, "x": 8, "y": 4},
+      "fieldConfig": {"defaults": {"unit": "ms", "custom": {"thresholdsStyle": {"mode": "line"}}, "thresholds": {"mode": "absolute", "steps": [{"color": "green", "value": null}, {"color": "red", "value": 200}]}}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "histogram_quantile(0.95, sum by (le, operation) (rate(rendezvous_http_duration_milliseconds_bucket[5m])))", "legendFormat": "{{operation}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 8,
+      "title": "HTTP error and shedding rate",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 8, "w": 8, "x": 16, "y": 4},
+      "fieldConfig": {"defaults": {"unit": "reqps"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (status_code) (rate(rendezvous_http_requests_total{status_code=~\"4..|5..\"}[5m]))", "legendFormat": "HTTP {{status_code}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 9,
+      "title": "Browser live-update load",
+      "description": "Active public SSE clients, tenant scopes, and bounded replay entries.",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 0, "y": 12},
+      "fieldConfig": {"defaults": {"unit": "short"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [
+        {"editorMode": "code", "expr": "rendezvous_browser_sse_subscribers", "legendFormat": "Subscribers", "range": true, "refId": "A"},
+        {"editorMode": "code", "expr": "rendezvous_browser_sse_tenants", "legendFormat": "Tenant scopes", "range": true, "refId": "B"},
+        {"editorMode": "code", "expr": "rendezvous_browser_replay_entries", "legendFormat": "Replay entries", "range": true, "refId": "C"}
+      ]
+    },
+    {
+      "id": 10,
+      "title": "UDP mediation results",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 8, "y": 12},
+      "fieldConfig": {"defaults": {"unit": "pps"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (operation, result) (rate(rendezvous_udp_results_total[5m]))", "legendFormat": "{{operation}} · {{result}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 11,
+      "title": "UDP p95 processing latency",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 16, "y": 12},
+      "fieldConfig": {"defaults": {"unit": "ms", "custom": {"thresholdsStyle": {"mode": "line"}}, "thresholds": {"mode": "absolute", "steps": [{"color": "green", "value": null}, {"color": "red", "value": 100}]}}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "histogram_quantile(0.95, sum by (le, operation) (rate(rendezvous_udp_duration_milliseconds_bucket[5m])))", "legendFormat": "{{operation}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 12,
+      "title": "UDP ingress and admitted response budget",
+      "description": "Traffic bytes observed by the process and the conservative maximum response budget admitted for successful introductions; this is not actual egress.",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 0, "y": 19},
+      "fieldConfig": {"defaults": {"unit": "Bps"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [
+        {"editorMode": "code", "expr": "sum by (operation) (rate(rendezvous_udp_received_bytes_total[5m]))", "legendFormat": "Ingress · {{operation}}", "range": true, "refId": "A"},
+        {"editorMode": "code", "expr": "sum by (operation) (rate(rendezvous_udp_response_budget_bytes_total[5m]))", "legendFormat": "Response budget · {{operation}}", "range": true, "refId": "B"}
+      ]
+    },
+    {
+      "id": 13,
+      "title": "Admission-control drops",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 8, "y": 19},
+      "fieldConfig": {"defaults": {"unit": "ops"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (transport, partition) (rate(rendezvous_limiter_drops_total[5m]))", "legendFormat": "{{transport}} · {{partition}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 14,
+      "title": "Direct-connect outcomes",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 16, "y": 19},
+      "fieldConfig": {"defaults": {"unit": "ops"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (outcome, elapsed_bucket) (rate(rendezvous_connection_outcomes_total[5m]))", "legendFormat": "{{outcome}} · {{elapsed_bucket}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 15,
+      "title": "Pairing p95 latency",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 0, "y": 26},
+      "fieldConfig": {"defaults": {"unit": "ms", "custom": {"thresholdsStyle": {"mode": "line"}}, "thresholds": {"mode": "absolute", "steps": [{"color": "green", "value": null}, {"color": "red", "value": 100}]}}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "histogram_quantile(0.95, rate(rendezvous_pairing_latency_milliseconds_bucket[5m]))", "legendFormat": "Pairing p95", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 16,
+      "title": "Presence and expiry state",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 8, "y": 26},
+      "fieldConfig": {"defaults": {"unit": "short"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [
+        {"editorMode": "code", "expr": "rendezvous_store_fresh_presence_bindings", "legendFormat": "Fresh presence", "range": true, "refId": "A"},
+        {"editorMode": "code", "expr": "rendezvous_store_awaiting_presence_listings", "legendFormat": "Awaiting presence", "range": true, "refId": "B"},
+        {"editorMode": "code", "expr": "rate(rendezvous_store_expiry_churn_total[5m])", "legendFormat": "Expiry churn/s", "range": true, "refId": "C"}
+      ]
+    },
+    {
+      "id": 17,
+      "title": "Signing key state",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 16, "y": 26},
+      "fieldConfig": {"defaults": {"unit": "short"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "rendezvous_signing_keys", "legendFormat": "{{state}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 18,
+      "title": "Minimum signing window",
+      "description": "Page below seven days; escalate below 24 hours.",
+      "type": "stat",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 5, "w": 6, "x": 0, "y": 33},
+      "fieldConfig": {"defaults": {"unit": "s", "thresholds": {"mode": "absolute", "steps": [{"color": "red", "value": null}, {"color": "orange", "value": 86400}, {"color": "green", "value": 604800}]}}, "overrides": []},
+      "options": {"colorMode": "background", "graphMode": "area", "justifyMode": "center", "orientation": "auto", "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": false}, "textMode": "auto", "wideLayout": true},
+      "targets": [{"editorMode": "code", "expr": "rendezvous_signing_key_sign_seconds_remaining", "legendFormat": "Signing window", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 19,
+      "title": "Operator authentication",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 5, "w": 6, "x": 6, "y": 33},
+      "fieldConfig": {"defaults": {"unit": "ops"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (result) (rate(rendezvous_operator_authentication_total[5m]))", "legendFormat": "{{result}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 20,
+      "title": "Privileged audit outcomes",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 5, "w": 6, "x": 12, "y": 33},
+      "fieldConfig": {"defaults": {"unit": "ops"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (action, result) (rate(rendezvous_audit_events_total[5m]))", "legendFormat": "{{action}} · {{result}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 21,
+      "title": "Metrics access",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 5, "w": 6, "x": 18, "y": 33},
+      "fieldConfig": {"defaults": {"unit": "ops"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [{"editorMode": "code", "expr": "sum by (result) (rate(rendezvous_metrics_scrapes_total[5m]))", "legendFormat": "{{result}}", "range": true, "refId": "A"}]
+    },
+    {
+      "id": 22,
+      "title": "Process memory",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 0, "y": 38},
+      "fieldConfig": {"defaults": {"unit": "bytes", "custom": {"thresholdsStyle": {"mode": "line"}}, "thresholds": {"mode": "absolute", "steps": [{"color": "green", "value": null}, {"color": "orange", "value": 1073741824}, {"color": "red", "value": 1610612736}]}}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [
+        {"editorMode": "code", "expr": "process_resident_memory_bytes", "legendFormat": "Resident", "range": true, "refId": "A"},
+        {"editorMode": "code", "expr": "dotnet_gc_heap_size_bytes", "legendFormat": "Managed heap", "range": true, "refId": "B"}
+      ]
+    },
+    {
+      "id": 23,
+      "title": "Process CPU and threads",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 8, "y": 38},
+      "fieldConfig": {"defaults": {"unit": "short"}, "overrides": [{"matcher": {"id": "byName", "options": "CPU cores"}, "properties": [{"id": "unit", "value": "cores"}]}]},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [
+        {"editorMode": "code", "expr": "rate(process_cpu_seconds_total[5m])", "legendFormat": "CPU cores", "range": true, "refId": "A"},
+        {"editorMode": "code", "expr": "process_threads", "legendFormat": "Process threads", "range": true, "refId": "B"},
+        {"editorMode": "code", "expr": "dotnet_thread_pool_threads", "legendFormat": "Thread-pool threads", "range": true, "refId": "C"}
+      ]
+    },
+    {
+      "id": 24,
+      "title": "Descriptor and GC pressure",
+      "type": "timeseries",
+      "datasource": {"type": "prometheus", "uid": "rendezvous-prometheus"},
+      "gridPos": {"h": 7, "w": 8, "x": 16, "y": 38},
+      "fieldConfig": {"defaults": {"unit": "short"}, "overrides": []},
+      "options": {"legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table", "placement": "bottom", "showLegend": true}, "tooltip": {"mode": "multi", "sort": "desc"}},
+      "targets": [
+        {"editorMode": "code", "expr": "process_open_file_descriptors", "legendFormat": "Open descriptors", "range": true, "refId": "A"},
+        {"editorMode": "code", "expr": "sum(rate(dotnet_gc_collections_total[5m]))", "legendFormat": "GC collections/s", "range": true, "refId": "B"},
+        {"editorMode": "code", "expr": "dotnet_thread_pool_available_worker_threads", "legendFormat": "Available workers", "range": true, "refId": "C"}
+      ]
+    }
+  ],
+  "refresh": "15s",
+  "schemaVersion": 41,
+  "tags": ["rendezvous", "operations", "privacy-safe"],
+  "templating": {"list": []},
+  "time": {"from": "now-1h", "to": "now"},
+  "timepicker": {},
+  "timezone": "browser",
+  "title": "Rendezvous operational overview",
+  "uid": "rendezvous-overview",
+  "version": 1,
+  "weekStart": ""
+}

deploy/observability/grafana/provisioning/dashboards/rendezvous.yaml

@@ -0,0 +1,13 @@
+apiVersion: 1
+
+providers:
+  - name: Rendezvous
+    orgId: 1
+    folder: Rendezvous
+    type: file
+    disableDeletion: true
+    allowUiUpdates: false
+    updateIntervalSeconds: 30
+    options:
+      path: /var/lib/grafana/dashboards
+      foldersFromFilesStructure: false

deploy/observability/grafana/provisioning/datasources/prometheus.yaml

@@ -0,0 +1,17 @@
+apiVersion: 1
+
+deleteDatasources:
+  - name: Rendezvous Prometheus
+    orgId: 1
+
+datasources:
+  - name: Rendezvous Prometheus
+    uid: rendezvous-prometheus
+    type: prometheus
+    access: proxy
+    url: http://prometheus:9090
+    isDefault: true
+    editable: false
+    jsonData:
+      httpMethod: POST
+      timeInterval: 15s

deploy/observability/prometheus/prometheus.yml

@@ -0,0 +1,14 @@
+global:
+  scrape_interval: 15s
+  evaluation_interval: 15s
+  external_labels:
+    service: rendezvous
+
+scrape_configs:
+  - job_name: rendezvous
+    scheme: http
+    metrics_path: /metrics
+    bearer_token_file: /run/secrets/rendezvous-metrics-token
+    static_configs:
+      - targets:
+          - rendezvous:8080

deploy/observability/secrets/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore

docs/api/rendezvous-v1.json

@@ -1177,6 +1177,159 @@
         }
       }
     },
+    "/v1/sessions/stream": {
+      "get": {
+        "tags": [
+          "Sessions"
+        ],
+        "operationId": "StreamSessions",
+        "parameters": [
+          {
+            "name": "contractVersion",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "type": "integer",
+              "format": "int32"
+            }
+          },
+          {
+            "name": "gameId",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "environmentId",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "protocolVersion",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "type": "integer",
+              "format": "uint32"
+            }
+          },
+          {
+            "name": "regionId",
+            "in": "query",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "excludeFull",
+            "in": "query",
+            "schema": {
+              "type": "boolean"
+            }
+          },
+          {
+            "name": "streamCursor",
+            "in": "query",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "Last-Event-ID",
+            "in": "header",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "headers": {
+              "X-Rendezvous-Correlation-ID": {
+                "description": "Safe request correlation identifier generated by the service.",
+                "schema": {
+                  "type": "string"
+                }
+              }
+            },
+            "content": {
+              "text/event-stream": {
+                "schema": {
+                  "$ref": "#/components/schemas/SessionStreamEvent"
+                }
+              }
+            }
+          },
+          "400": {
+            "description": "Bad Request",
+            "headers": {
+              "X-Rendezvous-Correlation-ID": {
+                "description": "Safe request correlation identifier generated by the service.",
+                "schema": {
+                  "type": "string"
+                }
+              }
+            },
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ApiError"
+                }
+              }
+            }
+          },
+          "429": {
+            "description": "Too Many Requests",
+            "headers": {
+              "X-Rendezvous-Correlation-ID": {
+                "description": "Safe request correlation identifier generated by the service.",
+                "schema": {
+                  "type": "string"
+                }
+              },
+              "Retry-After": {
+                "description": "Whole seconds before the caller should retry (1-60).",
+                "schema": {
+                  "type": "integer",
+                  "format": "int32"
+                }
+              }
+            },
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ApiError"
+                }
+              }
+            }
+          },
+          "503": {
+            "description": "Service Unavailable",
+            "headers": {
+              "X-Rendezvous-Correlation-ID": {
+                "description": "Safe request correlation identifier generated by the service.",
+                "schema": {
+                  "type": "string"
+                }
+              }
+            },
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ApiError"
+                }
+              }
+            }
+          }
+        }
+      }
+    },
     "/v1/sessions/{listingId}/join-attempts": {
       "get": {
         "tags": [
@@ -2657,7 +2810,8 @@
       "BrowseSessionsResponse": {
         "required": [
           "contractVersion",
-          "items"
+          "items",
+          "streamCursor"
         ],
         "type": "object",
         "properties": {
@@ -2676,6 +2830,9 @@
               "null",
               "string"
             ]
+          },
+          "streamCursor": {
+            "type": "string"
           }
         }
       },
@@ -3545,6 +3702,54 @@
         "type": "string",
         "format": "uuid"
       },
+      "SessionStreamEvent": {
+        "required": [
+          "contractVersion",
+          "kind",
+          "cursor"
+        ],
+        "type": "object",
+        "properties": {
+          "contractVersion": {
+            "type": "integer",
+            "format": "int32"
+          },
+          "kind": {
+            "$ref": "#/components/schemas/SessionStreamEventKind"
+          },
+          "cursor": {
+            "type": "string"
+          },
+          "session": {
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/SessionListing"
+              }
+            ]
+          },
+          "listingId": {
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/SessionListingId"
+              }
+            ]
+          }
+        }
+      },
+      "SessionStreamEventKind": {
+        "enum": [
+          "sessionUpsert",
+          "sessionRemove",
+          "reset",
+          "keepalive"
+        ]
+      },
       "UpdateSessionRequest": {
         "required": [
           "contractVersion",
@@ -3563,6 +3768,33 @@
           "leaseToken": {
             "type": "string"
           },
+          "regionId": {
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/RegionId"
+              }
+            ]
+          },
+          "protocolVersion": {
+            "type": [
+              "null",
+              "integer"
+            ],
+            "format": "uint32"
+          },
+          "visibility": {
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/ListingVisibility"
+              }
+            ]
+          },
           "buildVersion": {
             "type": "string"
           },

docs/architecture/project-boundaries.md

@@ -29,6 +29,8 @@ engine, transport, or server dependency therefore fails the normal test gate.
 ## Supported toolchain
 
 - Build SDK: .NET SDK 10.0.301, pinned by `global.json`.
+- Verification runtime: .NET SDK 8.0.128 supplies the pinned .NET 8.0.28
+  runtime used by TestClient process tests and release verification.
 - Server runtime: .NET 10 LTS.
 - Client/contracts compatibility target: .NET Standard 2.1, consumable by the
   .NET 8-or-later runtime used by current Godot 4 C# projects.

docs/deployment/linux.md

@@ -42,6 +42,22 @@ test "$RENDEZVOUS_UID" -ne 0
 docker compose -f deploy/compose/compose.yaml up --build --detach
 ```
 
+The example defaults to host TCP 8080 and UDP 9050. On a shared host, set
+`RENDEZVOUS_HTTP_HOST_PORT` and `RENDEZVOUS_UDP_HOST_PORT` before starting
+Compose, then point `RENDEZVOUS_SMOKE_HTTP_URL` and
+`RENDEZVOUS_SMOKE_UDP_ENDPOINT` at those published ports. The container ports
+and production-advertised service ports remain 8080/9050. Sibling-container CI
+runners may also set `RENDEZVOUS_CONFIG_SOURCE` and
+`RENDEZVOUS_SECRET_SOURCE` to host-visible absolute bind-source paths; local
+operators should normally keep the checked-in relative defaults. CI runs its
+ephemeral smoke client as a sidecar in the service container's network namespace
+to avoid runner-specific bridge and host-routing policy; it does not widen the
+default loopback HTTP publication. It mints the disposable publisher credential
+while the generated key is still owner-private, then makes the key read-only for
+the non-root service container. Automation probes readiness once per second and
+allows up to three minutes for a cold, resource-constrained image to become
+ready; the protocol smoke retains its separate, stricter scenario timeout.
+
 `deploy/compose/appsettings.Production.json` is a local/private-bridge smoke
 profile, not an Internet template: TCP is published only on host loopback, the
 explicit `rendezvous` host name serves isolated clients on the Compose network,

docs/integration/live-session-updates.md

@@ -0,0 +1,114 @@
+# Live session-list updates
+
+Tracking: #26
+
+Live updates are an optional acceleration for an open server browser. The
+bounded `GET /v1/sessions` snapshot remains the source of truth, and join
+authorization still revalidates current capacity, presence, policy, and
+compatibility. A displayed player count is advisory, never an admission promise.
+
+## Snapshot, stream, reset
+
+Every `BrowseSessionsResponse` includes `streamCursor` in addition to its normal
+pagination cursor. Connect to `GET /v1/sessions/stream` with the same game,
+environment, protocol, optional region, and `excludeFull` filter. Send the most
+recent stream cursor as `Last-Event-ID`.
+
+| SSE event | Contract kind | UI action |
+| --- | --- | --- |
+| `session_upsert` | `sessionUpsert` | Add or replace the complete public projection by listing ID. |
+| `session_remove` | `sessionRemove` | Remove the listing ID. |
+| `reset` | `reset` | Discard local state, fetch a fresh snapshot, then reconnect with its cursor. |
+| `keepalive` | `keepalive` | Preserve the cursor and connection; do not change UI state. |
+
+Each SSE `id` equals the opaque cursor inside its JSON event. Cursors are signed,
+short-lived, monotonically ordered, and bound to the complete filter. A missing,
+expired, corrupted, foreign, future, or replay-gapped cursor produces `reset`
+instead of a potentially incomplete view. Do not parse or retain it as a stable
+identifier.
+
+Updates cover creation after fresh UDP presence, public-field/capacity changes,
+presence staleness and recovery, lease expiry, deregistration, operator or
+principal revocation, and visibility/region/protocol changes. Events contain the
+same bounded public `SessionListing` as snapshots. They never contain raw peer
+endpoints, lease tokens, punch capabilities, tickets, publisher subjects, or
+internal store identifiers.
+
+## SDK and polling fallback
+
+```csharp
+BrowseSessionsRequest filter = new()
+{
+    GameId = new("space-game"),
+    EnvironmentId = new("production"),
+    ProtocolVersion = 7,
+    RegionId = new("eu-central"),
+    ExcludeFull = true,
+};
+RendezvousClientResult<BrowseSessionsResponse> snapshot =
+    await browser.BrowseAsync(filter, cancellationToken);
+
+await foreach (RendezvousClientResult<SessionStreamEvent> update in
+    browser.StreamAsync(filter, snapshot.Value!.StreamCursor, cancellationToken))
+{
+    if (!update.IsSuccess)
+    {
+        // Switch to bounded polling with jittered backoff.
+        break;
+    }
+    // Apply upsert/remove by listing ID. On reset, discard and browse again.
+}
+```
+
+Cancellation or enumerator disposal closes the response and releases the server
+subscription. A normal connection-duration close is a reconnect signal: use the
+last applied event cursor. Repeated failures, unsupported platform HTTP stacks,
+and restrictive proxies fall back to snapshots with exponential jittered
+backoff, a capped interval, and `Retry-After`. Never open parallel streams to
+compensate for a slow UI.
+
+## TestClient
+
+```bash
+dotnet run --project src/FinalFactory.Rendezvous.TestClient \
+  --configuration Release --no-build -- \
+  watch --service https://rendezvous.example.invalid/ \
+  --game space-game --environment production --region eu-central --protocol 7 \
+  --run-seconds 60 --json
+```
+
+`watch.snapshot`, `watch.session-upsert`, `watch.session-remove`,
+`watch.keepalive`, and `watch.reconnect` are stable diagnostics. Add
+`--exercise-reset --script` to corrupt the snapshot cursor deliberately and
+verify a typed reset plus snapshot refresh. Use `--exercise-reconnect --script`
+while producing one update to close the first stream deliberately, reconnect
+from its prior cursor, and verify that the same ordered event is replayed.
+Polished list diffing, selection retention, animation, and accessibility remain
+in each game.
+
+## Bounds and slow consumers
+
+The v1 journal retains at most 4,096 public-only changes. It admits at most 256
+subscribers total and 64 per tenant, reads at most 128 changes per batch,
+waits a configurable 50 milliseconds after a live change and coalesces the
+resulting batch to the final change per listing, sends a keepalive every 15
+seconds, and closes a connection after five minutes. A consumer behind the
+replay window receives `reset`; it never acquires an unbounded queue.
+
+Normal optional-work concurrency and per-source/tenant rate controls apply for
+the stream lifetime. Exhaustion returns typed HTTP `429` before streaming.
+Shutdown cancels streams; reconnect only after readiness returns and expect a
+reset after a single-active restart because listings and replay are ephemeral.
+
+## Reverse proxy
+
+- Disable response buffering (`X-Accel-Buffering: no` is also emitted),
+  compression, transformation, and caching for `text/event-stream`.
+- Preserve `Last-Event-ID`; set upstream/read timeouts above the 15-second
+  keepalive and around six minutes for the five-minute connection ceiling.
+- Flush events promptly and use HTTP/2 only when streaming semantics survive.
+- Preserve the source-IP trust boundary and abuse controls; do not add a bypass.
+
+Verify the deployed proxy with an idle keepalive, update, reconnect, invalid
+cursor reset, slow reader, and graceful shutdown. An in-process pass does not
+prove that a production proxy is non-buffering.

docs/integration/test-client.md

@@ -146,7 +146,14 @@ Never use an unbounded sleep to orchestrate processes. Wait for versioned events
 such as `host.ready` and apply a deadline. Useful success events are
 `host.registered`, `host.ready`, `host.direct-traffic`, `host.deregistered`,
 `browse.completed`, `browse.session`, `join.connected`, `join.direct-traffic`,
-and `join.outcome-report`.
+`join.outcome-report`, `watch.snapshot`, `watch.session-upsert`,
+`watch.session-remove`, `watch.reset`, `watch.reconnect`, and `watch.complete`.
+
+For a bounded live-directory diagnostic, use `watch --run-seconds 60`. Add
+`--exercise-reset --script` to prove fail-closed cursor recovery, or
+`--exercise-reconnect --script` while changing one listing to prove ordered
+`Last-Event-ID` replay after a deliberate disconnect. The full event and proxy
+contract is in [live session-list updates](live-session-updates.md).
 
 | Exit | Meaning |
 | ---: | --- |

docs/operations/diagnostic-dashboards.md

@@ -0,0 +1,123 @@
+# Diagnostic dashboards
+
+Tracking: #27
+
+Rendezvous provides two deliberately separate, optional views. The public
+session diagnostic helps a player or integration operator understand safe
+session-list state using only the public browse contract. The private Grafana
+dashboard exposes aggregate operational health through authenticated metrics.
+Neither view grants operator privileges or exposes player identity, endpoints,
+credentials, capabilities, or raw session metadata beyond the explicitly
+allowlisted public browse fields.
+
+## Public read-only session diagnostic
+
+The static diagnostic is disabled by default. Enable it only for approved
+game/environment scopes and keep the allowlist narrow:
+
+```json
+"Diagnostics": {
+  "Enabled": true,
+  "PollIntervalSeconds": 10,
+  "MaximumRenderedSessions": 100,
+  "Scopes": [
+    {
+      "GameId": "space-game",
+      "EnvironmentId": "smoke",
+      "ProtocolVersions": [1, 2],
+      "Regions": ["local"]
+    }
+  ]
+}
+```
+
+Open `/diagnostics` on the same origin as Rendezvous. The page cannot choose a
+different backend, request private visibility, join a session, or call the
+operator surface. It renders a bounded snapshot, then applies ordered SSE
+updates. A replay reset, corrupt cursor, incomplete snapshot, transport failure,
+or deliberate reconnect returns to a fresh authoritative snapshot and bounded
+polling. Apply filter changes explicitly; **Reset filters** restores the
+configured defaults, while **Reconnect now** tests recovery without changing
+the selection.
+
+The page uses semantic HTML, labelled controls, visible keyboard focus, status
+text in addition to color, a reduced-motion mode, and a 320-pixel reflow. It
+creates untrusted content with `textContent` only. The endpoint sets a restrictive
+same-origin content-security policy, denies framing, disables MIME sniffing and
+browser capabilities, and marks every asset/config response `no-store`.
+
+This is a diagnostics convenience, not a game browser, management console, or
+availability monitor. Disable it independently by setting `Enabled` to `false`;
+all diagnostic paths then return `404` without affecting game traffic, metrics,
+or health endpoints.
+
+## Private Prometheus and Grafana view
+
+The observability overlay pins Prometheus 3.13.1 and Grafana 13.1.0 by immutable
+multi-platform image digest. Prometheus is not published to the host. Grafana is
+bound to host loopback, disables anonymous access and sign-up, and reads its
+administrator password from a file. The service and Prometheus share only the
+metrics bearer-token file. All three secrets remain ignored by Git.
+
+Create independent random secrets, then start the base service and overlay:
+
+```bash
+install -d -m 0700 deploy/compose/secrets deploy/observability/secrets
+umask 077
+openssl rand -out deploy/compose/secrets/signing-key 32
+openssl rand -hex 32 >deploy/observability/secrets/rendezvous-metrics-token
+openssl rand -base64 36 >deploy/observability/secrets/grafana-admin-password
+export RENDEZVOUS_UID="$(id -u)"
+export RENDEZVOUS_GID="$(id -g)"
+test "$RENDEZVOUS_UID" -ne 0
+docker compose \
+  -f deploy/compose/compose.yaml \
+  -f deploy/observability/compose.yaml \
+  up --build --detach
+```
+
+Visit `http://127.0.0.1:3000`, sign in as `rendezvous-admin`, and open the
+**Rendezvous operational overview** folder/dashboard. The provisioned panels
+cover scrape/store/drain health, listing and join capacity, HTTP volume/errors
+and p95, browse/SSE load, lease and join operations, UDP results/latency/bytes,
+admission drops, connection outcomes, pairing latency, presence/expiry state,
+signing windows, security/audit results, and process/GC/descriptor pressure.
+Capacity gauges use the approved single-process envelope of 25,000 listings and
+10,000 active attempts, with 70% warning and 90% critical thresholds. The UDP
+response series is a conservative admitted maximum, not observed egress.
+
+Validate merged configuration and checked-in dashboard structure before every
+rollout:
+
+```bash
+RENDEZVOUS_UID="$(id -u)" RENDEZVOUS_GID="$(id -g)" \
+  docker compose \
+    -f deploy/compose/compose.yaml \
+    -f deploy/observability/compose.yaml \
+    config --quiet
+./scripts/test-observability-assets.sh
+```
+
+For a real deployment, keep Grafana on a private authenticated management
+network instead of host loopback, replace the local admin login with the
+organization's supported identity boundary, enforce TLS at the edge, and set
+retention to the approved operational period. Do not make Prometheus public.
+Provisioning is read-only so local UI edits cannot silently drift from source.
+
+## Verify, rotate, and disable
+
+After startup, verify the dashboard shows `UP`, store `AVAILABLE`, a nonzero
+signing window, and changing request/UDP panels during a smoke run. Confirm an
+unauthenticated `/metrics` request returns `404`, the bearer-authenticated
+collector target is healthy, Prometheus is not bound on a host port, Grafana is
+not anonymously accessible, and dashboard query labels contain no identifiers.
+
+Rotate metrics access by writing a new 32-128 character token to the secret file
+with private permissions and restarting Rendezvous and Prometheus together.
+Rotate the Grafana administrator password through the same protected secret
+workflow. Delete both secret files after a disposable local run.
+
+To disable aggregate observability independently, stop/remove the overlay and
+set `Rendezvous:Metrics:Enabled` to `false`; `/metrics` returns `404` and the
+core service continues. To disable only the public session diagnostic, leave the
+overlay running and set `Rendezvous:Diagnostics:Enabled` to `false`.

docs/operations/observability-and-operator-runbook.md

@@ -2,9 +2,10 @@
 
 This runbook defines the production signals and privileged controls for the
 Rendezvous service. The service emits `System.Diagnostics.Metrics` instruments
-from the `FinalFactory.Rendezvous` meter and distributed-tracing activities from
+from the `FinalFactory.Rendezvous` meter, distributed-tracing activities from
-`FinalFactory.Rendezvous.Server`. Connect those sources to the deployment's
+`FinalFactory.Rendezvous.Server`, and an optional bearer-protected Prometheus
-OpenTelemetry or equivalent collector. Do not add identifiers to metric labels.
+endpoint. Connect only a private collector network. Do not add identifiers to
+metric labels.
 
 Concrete detect/contain/recover/verify procedures for abuse, key compromise,
 targeted revocation, restart, rollback, saturation, privacy incidents, and
@@ -38,6 +39,25 @@ dependency upgrades are in the [incident and change runbooks](incident-runbooks.
 | `rendezvous.store.expiry_churn` | Cumulative natural expiry activity | none |
 | `rendezvous.store.available` | Store health (`1` available, `0` unavailable) | none |
 
+The Prometheus exporter additionally exposes active/fresh/awaiting store state,
+drain state, SSE subscriber/tenant/replay gauges, bounded HTTP and UDP
+histograms, UDP ingress and conservative admitted-response budgets, signing-key
+state/window gauges, and process/.NET pressure. Its only labels are the fixed
+operation, status, result, transport, partition, action, outcome, elapsed-bucket,
+key-state, and GC-generation dimensions. Unknown or unsafe values normalize to
+`other`; identifiers, metadata, addresses, endpoints, tokens, and capabilities
+are never labels.
+
+The exporter is disabled by default. Enabling `Rendezvous:Metrics:Enabled`
+requires `BearerTokenSecretReference` to be an external `env:` or absolute
+`file:` secret containing 32-128 visible ASCII bytes. Unauthorized requests get
+the same `404` as a disabled endpoint, and accepted responses are `no-store`.
+Expose `/metrics` only to the private collector network, rotate its token as a
+deployment secret, and never place the token in a URL, Compose environment
+value, dashboard, log, or issue. The checked-in Prometheus/Grafana provisioning
+and its verification procedure are in
+[diagnostic dashboards](diagnostic-dashboards.md).
+
 HTTP responses include `X-Rendezvous-Correlation-ID`. It is a generated trace ID
 or random value, never a caller-supplied session or player identifier. UDP and
 HTTP activities contain operation-level data only. Logs and traces must not add

eng/release-builder.Dockerfile

@@ -1,11 +1,14 @@
 # syntax=docker/dockerfile:1.7@sha256:a57df69d0ea827fb7266491f2813635de6f17269be881f696fbfdf2d83dda33e
 FROM python:3.12.11-slim-bookworm@sha256:c00fc7b44d844b6da22861ec24af43968a5200eac4ec607b4725d585165d6b49 AS release-python
 FROM ghcr.io/jqlang/jq:1.8.1@sha256:95de8f005ca027686a1ca3b0853e2bb219062438015862816159f3f25a4d4230 AS release-jq
+FROM mcr.microsoft.com/dotnet/runtime:8.0.28-noble@sha256:19a311642eb7ee9c985bd71b9e5618123879df4e8d948f7388a41b0ee4788e25 AS dotnet-runtime-8
 
 FROM mcr.microsoft.com/dotnet/sdk:10.0.301-noble@sha256:ea8bde36c11b6e7eec2656d0e59101d4462f6bd630730f2c8201ed0572b295d5 AS release-builder
 COPY --from=release-python /usr/local/ /usr/local/
 COPY --from=release-jq /jq /usr/local/bin/jq
+COPY --from=dotnet-runtime-8 /usr/share/dotnet/shared/Microsoft.NETCore.App/8.0.28/ /usr/share/dotnet/shared/Microsoft.NETCore.App/8.0.28/
 RUN dotnet --version \
+    && dotnet --list-runtimes \
     && python3 --version \
     && git --version \
     && tar --version \

scripts/smoke-deployment.sh

@@ -58,6 +58,14 @@ temp_dir="$(mktemp -d)"
 host_log="$temp_dir/host.jsonl"
 join_log="$temp_dir/join.jsonl"
 host_pid=''
+sanitize_log() {
+    jq -Rrc 'fromjson? | {
+        event: (.event // "unknown"),
+        status: (.status // "unknown"),
+        phase: (.phase // "unknown"),
+        hasListingId: (((.listingId // "") | length) > 0)
+    }' "$1"
+}
 cleanup() {
     local status="$?"
     if [[ -n "$host_pid" ]] && kill -0 "$host_pid" 2>/dev/null; then
@@ -66,8 +74,8 @@ cleanup() {
     fi
     if [[ "$status" -ne 0 ]]; then
         printf 'Deployment smoke failed; sanitized diagnostic events follow.\n' >&2
-        [[ -f "$host_log" ]] && jq -c . "$host_log" >&2 || true
+        [[ -f "$host_log" ]] && sanitize_log "$host_log" >&2 || true
-        [[ -f "$join_log" ]] && jq -c . "$join_log" >&2 || true
+        [[ -f "$join_log" ]] && sanitize_log "$join_log" >&2 || true
     fi
     rm -rf "$temp_dir"
     return "$status"
@@ -84,26 +92,24 @@ dotnet run --project "$PROJECT" --configuration "$BUILD_CONFIGURATION" --no-buil
 host_pid="$!"
 
 ready=false
+listing_id=''
 for ((iteration = 0; iteration < TIMEOUT_SECONDS * 4; iteration++)); do
-    if jq -e 'select(.event == "host.ready")' "$host_log" >/dev/null 2>&1; then
+    if listing_id="$(jq -er '
+        select(.event == "host.ready" and .status == "ready")
+        | .listingId // empty
+    ' "$host_log" 2>/dev/null | tail -n 1)" && [[ -n "$listing_id" ]]; then
         ready=true
         break
     fi
     if ! kill -0 "$host_pid" 2>/dev/null; then
         printf 'Host diagnostic stopped before it became ready.\n' >&2
-        jq -c . "$host_log" >&2 || true
+        sanitize_log "$host_log" >&2 || true
         exit 1
     fi
     sleep 0.25
 done
 if [[ "$ready" != true ]]; then
-    printf 'Host diagnostic did not become ready within %s seconds.\n' "$TIMEOUT_SECONDS" >&2
+    printf 'Host diagnostic did not report a ready listing within %s seconds.\n' "$TIMEOUT_SECONDS" >&2
-    exit 1
-fi
-
-listing_id="$(jq -r 'select(.event == "host.registered") | .listingId' "$host_log" | tail -n 1)"
-if [[ -z "$listing_id" || "$listing_id" == null ]]; then
-    printf 'Host diagnostic did not report a listing ID.\n' >&2
     exit 1
 fi
 
@@ -115,9 +121,19 @@ dotnet run --project "$PROJECT" --configuration "$BUILD_CONFIGURATION" --no-buil
 wait "$host_pid"
 host_pid=''
 
-jq -e 'select(.event == "host.direct-traffic" and .status == "verified")' "$host_log" >/dev/null
+if ! jq -s -e '
-jq -e 'select(.event == "host.deregistered" and .status == "complete")' "$host_log" >/dev/null
+    any(.[]; .event == "host.direct-traffic" and .status == "verified")
-jq -e 'select(.event == "join.direct-traffic" and .status == "verified")' "$join_log" >/dev/null
+    and any(.[]; .event == "host.deregistered" and .status == "complete")
-jq -e 'select(.event == "join.outcome-report" and .status == "accepted")' "$join_log" >/dev/null
+' "$host_log" >/dev/null; then
+    printf 'Host diagnostic did not complete authenticated traffic and deregistration.\n' >&2
+    exit 1
+fi
+if ! jq -s -e '
+    any(.[]; .event == "join.direct-traffic" and .status == "verified")
+    and any(.[]; .event == "join.outcome-report" and .status == "accepted")
+' "$join_log" >/dev/null; then
+    printf 'Join diagnostic did not complete authenticated traffic and outcome reporting.\n' >&2
+    exit 1
+fi
 
 printf 'Rendezvous deployment smoke passed: HTTP live/ready and authenticated UDP mediation/direct traffic.\n'

scripts/test-diagnostic-dashboard.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$root"
+node --test tests/Diagnostics/*.test.mjs

scripts/test-observability-assets.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+node --test tests/Observability/observability-assets.test.mjs

src/FinalFactory.Rendezvous.Client/RendezvousClientAbstractions.cs

@@ -144,6 +144,11 @@ public interface IRendezvousSessionBrowserClient
         EnvironmentId environmentId,
         uint protocolVersion,
         CancellationToken cancellationToken = default);
+
+    IAsyncEnumerable<RendezvousClientResult<SessionStreamEvent>> StreamAsync(
+        BrowseSessionsRequest request,
+        string streamCursor,
+        CancellationToken cancellationToken = default);
 }
 
 public interface IRendezvousJoinClient

src/FinalFactory.Rendezvous.Client/RendezvousHttpTransport.cs

@@ -114,6 +114,49 @@ internal sealed class RendezvousHttpTransport
         }
     }
 
+    internal async Task<RendezvousClientResult<HttpResponseMessage>> OpenStreamAsync(
+        Func<HttpRequestMessage> requestFactory,
+        CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        using CancellationTokenSource requestTimeout =
+            CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+        requestTimeout.CancelAfter(_options.RequestTimeout);
+        CancellationToken requestCancellation = requestTimeout.Token;
+        using HttpRequestMessage request = requestFactory();
+        HttpResponseMessage? response = null;
+        try
+        {
+            response = await _httpClient.SendAsync(
+                request,
+                HttpCompletionOption.ResponseHeadersRead,
+                requestCancellation).ConfigureAwait(false);
+            if (response.IsSuccessStatusCode)
+            {
+                HttpResponseMessage ownedResponse = response;
+                response = null;
+                return RendezvousClientResult.Success(ownedResponse);
+            }
+
+            ApiError error = await ReadErrorAsync(response, requestCancellation).ConfigureAwait(false);
+            int? retryAfter = error.RetryAfterSeconds ?? GetRetryAfterSeconds(response.Headers.RetryAfter);
+            return RendezvousClientResult.Failure<HttpResponseMessage>(
+                error.Code,
+                error.Message,
+                retryAfter);
+        }
+        catch (Exception exception) when (IsTransientTransportFailure(exception, cancellationToken))
+        {
+            return RendezvousClientResult.Failure<HttpResponseMessage>(
+                RendezvousErrorCode.ServiceUnavailable,
+                "The Rendezvous event stream could not be opened.");
+        }
+        finally
+        {
+            response?.Dispose();
+        }
+    }
+
     internal static HttpRequestMessage JsonRequest<T>(
         HttpMethod method,
         string uri,

src/FinalFactory.Rendezvous.Client/RendezvousPublisherClient.cs

@@ -84,6 +84,9 @@ public sealed class RendezvousPublisherClient : IRendezvousPublisherClient
         {
             ContractVersion = request.ContractVersion,
             LeaseToken = session.LeaseToken,
+            RegionId = request.RegionId,
+            ProtocolVersion = request.ProtocolVersion,
+            Visibility = request.Visibility,
             BuildVersion = request.BuildVersion,
             DisplayName = request.DisplayName,
             Capacity = CopyCapacity(request.Capacity),

src/FinalFactory.Rendezvous.Client/RendezvousSessionBrowserClient.cs

@@ -1,3 +1,7 @@
+using System.Net.Http.Headers;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Text.Json;
 using FinalFactory.Rendezvous.Contracts;
 
 namespace FinalFactory.Rendezvous.Client;
@@ -106,5 +110,264 @@ public sealed class RendezvousSessionBrowserClient : IRendezvousSessionBrowserCl
             cancellationToken);
     }
 
-    private static string Escape(string value) => Uri.EscapeDataString(value ?? string.Empty);
+    public async IAsyncEnumerable<RendezvousClientResult<SessionStreamEvent>> StreamAsync(
+        BrowseSessionsRequest request,
+        string streamCursor,
+        [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        if (request is null)
+        {
+            throw new ArgumentNullException(nameof(request));
+        }
+        if (string.IsNullOrWhiteSpace(streamCursor)
+            || !ContractValidation.IsCursorValid(streamCursor))
+        {
+            throw new ArgumentException("A valid snapshot stream cursor is required.", nameof(streamCursor));
+        }
+
+        string query = $"v1/sessions/stream?contractVersion={request.ContractVersion}"
+            + $"&gameId={Escape(request.GameId.Value)}"
+            + $"&environmentId={Escape(request.EnvironmentId.Value)}"
+            + $"&protocolVersion={request.ProtocolVersion}"
+            + $"&excludeFull={request.ExcludeFull.ToString().ToLowerInvariant()}"
+            + (request.RegionId.HasValue ? $"&regionId={Escape(request.RegionId.Value.Value)}" : string.Empty);
+        RendezvousClientResult<HttpResponseMessage> opened = await _transport.OpenStreamAsync(
+            () =>
+            {
+                HttpRequestMessage message = new(HttpMethod.Get, query);
+                message.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("text/event-stream"));
+                message.Headers.TryAddWithoutValidation("Last-Event-ID", streamCursor);
+                return message;
+            },
+            cancellationToken).ConfigureAwait(false);
+        if (!opened.IsSuccess || opened.Value is null)
+        {
+            yield return RendezvousClientResult.Failure<SessionStreamEvent>(
+                opened.Error,
+                opened.Message,
+                opened.RetryAfterSeconds);
+            yield break;
+        }
+
+        using HttpResponseMessage response = opened.Value;
+        if (!string.Equals(
+                response.Content.Headers.ContentType?.MediaType,
+                "text/event-stream",
+                StringComparison.OrdinalIgnoreCase))
+        {
+            yield return RendezvousClientResult.Failure<SessionStreamEvent>(
+                RendezvousErrorCode.InternalError,
+                "The service returned an invalid event-stream content type.");
+            yield break;
+        }
+
+        using Stream source = await response.Content.ReadAsStreamAsync().ConfigureAwait(false);
+        using SseLineReader reader = new(source);
+        while (true)
+        {
+            SseReadResult? read = null;
+            RendezvousClientResult<SessionStreamEvent>? readFailure = null;
+            bool cancelled = false;
+            try
+            {
+                read = await ReadEventAsync(reader, cancellationToken).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
+            {
+                cancelled = true;
+            }
+            catch (Exception exception) when (exception is IOException or JsonException or InvalidDataException)
+            {
+                readFailure = RendezvousClientResult.Failure<SessionStreamEvent>(
+                    RendezvousErrorCode.InternalError,
+                    "The service returned an invalid or oversized event stream.");
+            }
+            if (cancelled)
+            {
+                yield break;
+            }
+            if (readFailure is not null)
+            {
+                yield return readFailure;
+                yield break;
+            }
+
+            if (read!.EndOfStream)
+            {
+                yield break;
+            }
+            yield return read.Result!;
+            if (!read.Result!.IsSuccess)
+            {
+                yield break;
+            }
+        }
+    }
+
+    private static async Task<SseReadResult> ReadEventAsync(
+        SseLineReader reader,
+        CancellationToken cancellationToken)
+    {
+        string? eventName = null;
+        string? id = null;
+        string? data = null;
+        int bytes = 0;
+        while (true)
+        {
+            string? line = await reader.ReadLineAsync(cancellationToken).ConfigureAwait(false);
+            if (line is null)
+            {
+                return eventName is null && id is null && data is null
+                    ? SseReadResult.End
+                    : throw new InvalidDataException("The final SSE event was incomplete.");
+            }
+            bytes += Encoding.UTF8.GetByteCount(line) + 1;
+            if (bytes > ContractLimits.SessionStreamEventMaxBytes)
+            {
+                throw new InvalidDataException("The SSE event exceeded the contract limit.");
+            }
+            if (line.Length == 0)
+            {
+                break;
+            }
+            if (line.StartsWith("event: ", StringComparison.Ordinal))
+            {
+                eventName = line[7..];
+            }
+            else if (line.StartsWith("id: ", StringComparison.Ordinal))
+            {
+                id = line[4..];
+            }
+            else if (line.StartsWith("data: ", StringComparison.Ordinal))
+            {
+                data = line[6..];
+            }
+        }
+
+        SessionStreamEvent? item = data is null
+            ? null
+            : JsonSerializer.Deserialize<SessionStreamEvent>(data, ContractJson.Options);
+        if (item is null
+            || !string.Equals(item.Cursor, id, StringComparison.Ordinal)
+            || !string.Equals(eventName, EventName(item.Kind), StringComparison.Ordinal)
+            || !IsValidShape(item))
+        {
+            return new(false, RendezvousClientResult.Failure<SessionStreamEvent>(
+                RendezvousErrorCode.InternalError,
+                "The service returned an invalid event envelope."));
+        }
+        return new(false, RendezvousClientResult.Success(item));
+    }
+
+    private static string EventName(SessionStreamEventKind kind) => kind switch
+    {
+        SessionStreamEventKind.SessionUpsert => "session_upsert",
+        SessionStreamEventKind.SessionRemove => "session_remove",
+        SessionStreamEventKind.Reset => "reset",
+        SessionStreamEventKind.Keepalive => "keepalive",
+        _ => string.Empty,
+    };
+
+    private static bool IsValidShape(SessionStreamEvent item) =>
+        item.ContractVersion == ContractLimits.ContractVersion
+        && !string.IsNullOrWhiteSpace(item.Cursor)
+        && ContractValidation.IsCursorValid(item.Cursor)
+        && (item.Kind == SessionStreamEventKind.SessionUpsert
+            && item.Session is not null
+            && IsValidListing(item.Session)
+            && item.ListingId is null
+            || item.Kind == SessionStreamEventKind.SessionRemove
+            && item.Session is null
+            && item.ListingId.HasValue
+            && item.ListingId.Value.Value != Guid.Empty
+            || item.Kind is SessionStreamEventKind.Reset or SessionStreamEventKind.Keepalive
+            && item.Session is null
+            && item.ListingId is null);
+
+    private static bool IsValidListing(SessionListing listing) =>
+        listing.ContractVersion == ContractLimits.ContractVersion
+        && listing.ListingId.Value != Guid.Empty
+        && !string.IsNullOrWhiteSpace(listing.GameId.Value)
+        && !string.IsNullOrWhiteSpace(listing.EnvironmentId.Value)
+        && !string.IsNullOrWhiteSpace(listing.RegionId.Value)
+        && listing.ProtocolVersion != 0
+        && ContractValidation.IsBuildVersionValid(listing.BuildVersion)
+        && ContractValidation.IsDisplayNameValid(listing.DisplayName)
+        && listing.Visibility == ListingVisibility.Public
+        && Enum.IsDefined(typeof(PublisherTrustMode), listing.PublisherTrustMode)
+        && ContractValidation.IsCapacityValid(listing.Capacity)
+        && ContractValidation.IsMetadataValid(listing.Metadata)
+        && (listing.DedicatedFallback is null
+            || ContractValidation.IsNetworkEndpointValid(listing.DedicatedFallback));
+
+    private static string Escape(string value) => Uri.EscapeDataString(value ?? string.Empty);
+
+    private sealed class SseReadResult
+    {
+        public SseReadResult(
+            bool endOfStream,
+            RendezvousClientResult<SessionStreamEvent>? result)
+        {
+            EndOfStream = endOfStream;
+            Result = result;
+        }
+
+        public bool EndOfStream { get; }
+        public RendezvousClientResult<SessionStreamEvent>? Result { get; }
+        public static SseReadResult End { get; } = new(true, null);
+    }
+
+    private sealed class SseLineReader(Stream source) : IDisposable
+    {
+        private static readonly UTF8Encoding Utf8 = new(false, true);
+        private readonly byte[] _buffer = new byte[4096];
+        private readonly MemoryStream _line = new();
+        private int _offset;
+        private int _count;
+
+        public async Task<string?> ReadLineAsync(CancellationToken cancellationToken)
+        {
+            while (true)
+            {
+                if (_offset >= _count)
+                {
+                    _count = await source.ReadAsync(
+                        _buffer.AsMemory(),
+                        cancellationToken).ConfigureAwait(false);
+                    _offset = 0;
+                    if (_count == 0)
+                    {
+                        if (_line.Length == 0)
+                        {
+                            return null;
+                        }
+                        return TakeLine();
+                    }
+                }
+
+                byte value = _buffer[_offset++];
+                if (value == (byte)'\n')
+                {
+                    return TakeLine();
+                }
+                if (_line.Length >= ContractLimits.SessionStreamEventMaxBytes)
+                {
+                    throw new InvalidDataException("An SSE line exceeded the contract limit.");
+                }
+                _line.WriteByte(value);
+            }
+        }
+
+        public void Dispose() => _line.Dispose();
+
+        private string TakeLine()
+        {
+            byte[] bytes = _line.ToArray();
+            _line.SetLength(0);
+            int length = bytes.Length > 0 && bytes[^1] == (byte)'\r'
+                ? bytes.Length - 1
+                : bytes.Length;
+            return Utf8.GetString(bytes, 0, length);
+        }
+    }
 }

src/FinalFactory.Rendezvous.Contracts/ContractLimits.cs

@@ -5,6 +5,7 @@ public static class ContractLimits
     public const int ContractVersion = 1;
     public const int HttpRequestMaxBytes = 16 * 1024;
     public const int BrowserResponseMaxBytes = 256 * 1024;
+    public const int SessionStreamEventMaxBytes = 32 * 1024;
     public const int UdpDatagramMaxBytes = 1_200;
     public const int MetadataMaxBytes = 4 * 1024;
     public const int MetadataMaxKeys = 32;

src/FinalFactory.Rendezvous.Contracts/Http/SessionContracts.cs

@@ -140,6 +140,10 @@ public sealed class UpdateSessionRequest
     [JsonRequired]
     public string LeaseToken { get; set; } = string.Empty;
 
+    public RegionId? RegionId { get; set; }
+    public uint? ProtocolVersion { get; set; }
+    public ListingVisibility? Visibility { get; set; }
+
     [JsonRequired]
     public string BuildVersion { get; set; } = string.Empty;
 
@@ -194,6 +198,32 @@ public sealed class BrowseSessionsResponse
     public List<SessionListing> Items { get; set; } = [];
 
     public string? NextCursor { get; set; }
+
+    [JsonRequired]
+    public string StreamCursor { get; set; } = string.Empty;
+}
+
+public enum SessionStreamEventKind
+{
+    SessionUpsert = 1,
+    SessionRemove = 2,
+    Reset = 3,
+    Keepalive = 4,
+}
+
+public sealed class SessionStreamEvent
+{
+    [JsonRequired]
+    public int ContractVersion { get; set; } = ContractLimits.ContractVersion;
+
+    [JsonRequired]
+    public SessionStreamEventKind Kind { get; set; }
+
+    [JsonRequired]
+    public string Cursor { get; set; } = string.Empty;
+
+    public SessionListing? Session { get; set; }
+    public SessionListingId? ListingId { get; set; }
 }
 
 public sealed class GetSessionResponse

src/FinalFactory.Rendezvous.Server/Browser/SessionBrowserService.cs

@@ -12,6 +12,8 @@ internal sealed record BrowserServiceResult<T>(RendezvousErrorCode Error, T? Val
 internal sealed class SessionBrowserService(
     IEphemeralRendezvousStore store,
     SessionBrowserCursorCodec cursors,
+    SessionStreamCursorCodec streamCursors,
+    SessionChangeJournal changes,
     IWallClock clock)
 {
     public BrowserServiceResult<BrowseSessionsResponse> Browse(
@@ -45,9 +47,25 @@ internal sealed class SessionBrowserService(
             request.PageSize + 1,
             after,
             request.ExcludeFull);
-        StoreResult<IReadOnlyList<StoredListing>> found = store.BrowseVisibleListings(
+        StoreResult<IReadOnlyList<StoredListing>> found = default!;
-            query,
+        long streamRevision = 0;
-            cancellationToken);
+        bool stableSnapshot = false;
+        for (int attempt = 0; attempt < 3; attempt++)
+        {
+            long before = changes.CurrentRevision;
+            found = store.BrowseVisibleListings(query, cancellationToken);
+            long afterRevision = changes.CurrentRevision;
+            if (before == afterRevision)
+            {
+                streamRevision = afterRevision;
+                stableSnapshot = true;
+                break;
+            }
+        }
+        if (!stableSnapshot)
+        {
+            return new(RendezvousErrorCode.ServiceUnavailable);
+        }
         if (!found.Succeeded || found.Value is null)
         {
             return new(found.Code == StoreResultCode.ServiceUnavailable
@@ -65,7 +83,12 @@ internal sealed class SessionBrowserService(
             string? nextCursor = hasMore
                 ? cursors.Encode(query, items[^1].ListingId, clock.UtcNow)
                 : null;
-            BrowseSessionsResponse response = new() { Items = items, NextCursor = nextCursor };
+            BrowseSessionsResponse response = new()
+            {
+                Items = items,
+                NextCursor = nextCursor,
+                StreamCursor = streamCursors.Encode(query, streamRevision, clock.UtcNow),
+            };
             if (JsonSerializer.SerializeToUtf8Bytes(response, ContractJson.Options).Length
                 <= ContractLimits.BrowserResponseMaxBytes)
             {
@@ -76,7 +99,10 @@ internal sealed class SessionBrowserService(
             hasMore = true;
         }
 
-        return new(RendezvousErrorCode.None, new BrowseSessionsResponse());
+        return new(RendezvousErrorCode.None, new BrowseSessionsResponse
+        {
+            StreamCursor = streamCursors.Encode(query, streamRevision, clock.UtcNow),
+        });
     }
 
     public BrowserServiceResult<GetSessionResponse> Get(

src/FinalFactory.Rendezvous.Server/Browser/SessionChangeJournal.cs

@@ -0,0 +1,309 @@
+using FinalFactory.Rendezvous.Contracts;
+using FinalFactory.Rendezvous.Server.State;
+
+namespace FinalFactory.Rendezvous.Server.Browser;
+
+internal sealed record SessionChangeJournalOptions
+{
+    public int ReplayCapacity { get; init; } = 4096;
+    public int MaximumSubscribers { get; init; } = 256;
+    public int MaximumSubscribersPerTenant { get; init; } = 64;
+    public int MaximumBatchSize { get; init; } = 128;
+    public TimeSpan CoalesceInterval { get; init; } = TimeSpan.FromMilliseconds(50);
+    public TimeSpan KeepaliveInterval { get; init; } = TimeSpan.FromSeconds(15);
+    public TimeSpan MaximumConnectionDuration { get; init; } = TimeSpan.FromMinutes(5);
+
+    public void Validate()
+    {
+        if (ReplayCapacity is < 64 or > 65_536
+            || MaximumSubscribers is < 1 or > 4096
+            || MaximumSubscribersPerTenant < 1
+            || MaximumSubscribersPerTenant > MaximumSubscribers
+            || MaximumBatchSize is < 1 or > 1024
+            || CoalesceInterval < TimeSpan.Zero
+            || CoalesceInterval > TimeSpan.FromSeconds(1)
+            || KeepaliveInterval < TimeSpan.FromSeconds(1)
+            || KeepaliveInterval > TimeSpan.FromMinutes(1)
+            || MaximumConnectionDuration < KeepaliveInterval
+            || MaximumConnectionDuration > TimeSpan.FromMinutes(30))
+        {
+            throw new ArgumentOutOfRangeException(nameof(SessionChangeJournalOptions));
+        }
+    }
+}
+
+internal sealed record SessionChange(
+    long Revision,
+    SessionListingProjection? Before,
+    SessionListingProjection? After)
+{
+    public SessionListingId ListingId => (After ?? Before)!.Listing.ListingId;
+}
+
+internal sealed record SessionChangeBatch(
+    long CurrentRevision,
+    bool RequiresReset,
+    IReadOnlyList<SessionChange> Changes);
+
+internal sealed class SessionListingProjection
+{
+    private SessionListingProjection(SessionListing listing, bool visible)
+    {
+        Listing = listing;
+        Visible = visible;
+    }
+
+    public SessionListing Listing { get; }
+    public bool Visible { get; }
+
+    public static SessionListingProjection From(StoredListing stored) => new(
+        new SessionListing
+        {
+            ListingId = stored.Definition.ListingId,
+            GameId = stored.Definition.Scope.GameId,
+            EnvironmentId = stored.Definition.Scope.EnvironmentId,
+            RegionId = stored.Definition.RegionId,
+            ProtocolVersion = stored.Definition.ProtocolVersion,
+            BuildVersion = stored.Definition.BuildVersion,
+            DisplayName = stored.Definition.DisplayName,
+            Visibility = stored.Definition.Visibility,
+            PublisherTrustMode = stored.Definition.TrustMode,
+            Capacity = new SessionCapacity
+            {
+                CurrentPlayers = stored.Definition.CurrentPlayers,
+                MaximumPlayers = stored.Definition.MaximumPlayers,
+            },
+            Metadata = new Dictionary<string, string>(stored.Definition.Metadata, StringComparer.Ordinal),
+            DedicatedFallback = StoredListing.CopyEndpoint(stored.Definition.DedicatedFallback),
+        },
+        stored.HasFreshPresence && stored.Definition.Visibility == ListingVisibility.Public);
+
+    public bool Matches(VisibleListingQuery query) => Visible
+        && Listing.GameId == query.Scope.GameId
+        && Listing.EnvironmentId == query.Scope.EnvironmentId
+        && Listing.ProtocolVersion == query.ProtocolVersion
+        && (!query.RegionId.HasValue || Listing.RegionId == query.RegionId.Value)
+        && (!query.ExcludeFull
+            || Listing.Capacity.CurrentPlayers < Listing.Capacity.MaximumPlayers);
+
+    public static bool Equivalent(SessionListingProjection? left, SessionListingProjection? right)
+    {
+        if (ReferenceEquals(left, right))
+        {
+            return true;
+        }
+        if (left is null || right is null || left.Visible != right.Visible)
+        {
+            return false;
+        }
+
+        SessionListing a = left.Listing;
+        SessionListing b = right.Listing;
+        return a.ListingId == b.ListingId
+            && a.GameId == b.GameId
+            && a.EnvironmentId == b.EnvironmentId
+            && a.RegionId == b.RegionId
+            && a.ProtocolVersion == b.ProtocolVersion
+            && string.Equals(a.BuildVersion, b.BuildVersion, StringComparison.Ordinal)
+            && string.Equals(a.DisplayName, b.DisplayName, StringComparison.Ordinal)
+            && a.Visibility == b.Visibility
+            && a.PublisherTrustMode == b.PublisherTrustMode
+            && a.Capacity.CurrentPlayers == b.Capacity.CurrentPlayers
+            && a.Capacity.MaximumPlayers == b.Capacity.MaximumPlayers
+            && a.Metadata.Count == b.Metadata.Count
+            && a.Metadata.All(item => b.Metadata.TryGetValue(item.Key, out string? value)
+                && string.Equals(item.Value, value, StringComparison.Ordinal))
+            && EndpointEquals(a.DedicatedFallback, b.DedicatedFallback);
+    }
+
+    private static bool EndpointEquals(NetworkEndpoint? left, NetworkEndpoint? right) =>
+        left is null && right is null
+        || left is not null && right is not null
+        && left.AddressFamily == right.AddressFamily
+        && string.Equals(left.Address, right.Address, StringComparison.Ordinal)
+        && left.Port == right.Port;
+}
+
+internal sealed class SessionChangeJournal
+{
+    private readonly object _gate = new();
+    private readonly SessionChangeJournalOptions _options;
+    private readonly Queue<SessionChange> _changes = [];
+    private TaskCompletionSource<long> _changed = NewSignal();
+    private long _revision;
+    private int _subscribers;
+    private readonly Dictionary<TenantScope, int> _subscribersByTenant = [];
+
+    public SessionChangeJournal(SessionChangeJournalOptions options)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+        options.Validate();
+        _options = options;
+    }
+
+    public SessionChangeJournalOptions Options => _options;
+
+    public int ReplayCount
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _changes.Count;
+            }
+        }
+    }
+
+    public int SubscriberCount
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _subscribers;
+            }
+        }
+    }
+
+    public int SubscribedTenantCount
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _subscribersByTenant.Count;
+            }
+        }
+    }
+
+    public long CurrentRevision
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _revision;
+            }
+        }
+    }
+
+    public void Publish(StoredListing? before, StoredListing? after)
+    {
+        SessionListingProjection? previous = before is null ? null : SessionListingProjection.From(before);
+        SessionListingProjection? current = after is null ? null : SessionListingProjection.From(after);
+        if (SessionListingProjection.Equivalent(previous, current)
+            || previous is { Visible: false } && current is null
+            || previous is null && current is { Visible: false })
+        {
+            return;
+        }
+
+        TaskCompletionSource<long> signal;
+        long revision;
+        lock (_gate)
+        {
+            revision = ++_revision;
+            _changes.Enqueue(new SessionChange(revision, previous, current));
+            while (_changes.Count > _options.ReplayCapacity)
+            {
+                _changes.Dequeue();
+            }
+            signal = _changed;
+            _changed = NewSignal();
+        }
+        signal.TrySetResult(revision);
+    }
+
+    public SessionChangeBatch ReadAfter(long revision)
+    {
+        lock (_gate)
+        {
+            long oldest = _changes.TryPeek(out SessionChange? first)
+                ? first.Revision
+                : _revision + 1;
+            if (revision < oldest - 1 || revision > _revision)
+            {
+                return new(_revision, true, []);
+            }
+
+            SessionChange[] changes = _changes
+                .Where(change => change.Revision > revision)
+                .Take(_options.MaximumBatchSize)
+                .ToArray();
+            return new(_revision, false, changes);
+        }
+    }
+
+    public async Task<bool> WaitForChangeAsync(
+        long revision,
+        TimeSpan timeout,
+        CancellationToken cancellationToken)
+    {
+        Task<long> signal;
+        lock (_gate)
+        {
+            if (_revision > revision)
+            {
+                return true;
+            }
+            signal = _changed.Task;
+        }
+
+        try
+        {
+            await signal.WaitAsync(timeout, cancellationToken).ConfigureAwait(false);
+            return true;
+        }
+        catch (TimeoutException)
+        {
+            return false;
+        }
+    }
+
+    public bool TrySubscribe(TenantScope scope, out IDisposable? lease)
+    {
+        lock (_gate)
+        {
+            if (_subscribers >= _options.MaximumSubscribers
+                || _subscribersByTenant.GetValueOrDefault(scope)
+                    >= _options.MaximumSubscribersPerTenant)
+            {
+                lease = null;
+                return false;
+            }
+            _subscribers++;
+            _subscribersByTenant[scope] = _subscribersByTenant.GetValueOrDefault(scope) + 1;
+            lease = new Subscription(this, scope);
+            return true;
+        }
+    }
+
+    private void Release(TenantScope scope)
+    {
+        lock (_gate)
+        {
+            _subscribers--;
+            int remaining = _subscribersByTenant[scope] - 1;
+            if (remaining == 0)
+            {
+                _subscribersByTenant.Remove(scope);
+            }
+            else
+            {
+                _subscribersByTenant[scope] = remaining;
+            }
+        }
+    }
+
+    private static TaskCompletionSource<long> NewSignal() => new(
+        TaskCreationOptions.RunContinuationsAsynchronously);
+
+    private sealed class Subscription(
+        SessionChangeJournal owner,
+        TenantScope scope) : IDisposable
+    {
+        private SessionChangeJournal? _owner = owner;
+
+        public void Dispose() => Interlocked.Exchange(ref _owner, null)?.Release(scope);
+    }
+}

src/FinalFactory.Rendezvous.Server/Browser/SessionStreamCursorCodec.cs

@@ -0,0 +1,108 @@
+using System.Security.Cryptography;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using FinalFactory.Rendezvous.Contracts;
+using FinalFactory.Rendezvous.Server.State;
+
+namespace FinalFactory.Rendezvous.Server.Browser;
+
+internal sealed class SessionStreamCursorCodec : IDisposable
+{
+    private const string Prefix = "rvs1";
+    private readonly EphemeralCursorProtector _protector = new();
+
+    public string Encode(VisibleListingQuery query, long revision, DateTimeOffset now)
+    {
+        ArgumentOutOfRangeException.ThrowIfNegative(revision);
+        SessionStreamCursorPayload payload = new()
+        {
+            GameId = query.Scope.GameId.Value,
+            EnvironmentId = query.Scope.EnvironmentId.Value,
+            ProtocolVersion = query.ProtocolVersion,
+            RegionId = query.RegionId?.Value,
+            ExcludeFull = query.ExcludeFull,
+            Revision = revision,
+            ExpiresAtUnixSeconds = now.AddMinutes(10).ToUnixTimeSeconds(),
+        };
+        byte[] encoded = JsonSerializer.SerializeToUtf8Bytes(payload, ContractJson.Options);
+        try
+        {
+            return _protector.Protect(Prefix, encoded);
+        }
+        finally
+        {
+            CryptographicOperations.ZeroMemory(encoded);
+        }
+    }
+
+    public bool TryDecode(
+        string? cursor,
+        VisibleListingQuery query,
+        DateTimeOffset now,
+        out long revision)
+    {
+        revision = 0;
+        if (cursor is null || !_protector.TryUnprotect(Prefix, cursor, out byte[] encodedPayload))
+        {
+            return false;
+        }
+
+        SessionStreamCursorPayload? payload;
+        try
+        {
+            payload = JsonSerializer.Deserialize<SessionStreamCursorPayload>(
+                encodedPayload,
+                ContractJson.Options);
+        }
+        catch (JsonException)
+        {
+            payload = null;
+        }
+        finally
+        {
+            CryptographicOperations.ZeroMemory(encodedPayload);
+        }
+
+        if (payload is null
+            || payload.Revision < 0
+            || payload.ExpiresAtUnixSeconds <= now.ToUnixTimeSeconds()
+            || !string.Equals(payload.GameId, query.Scope.GameId.Value, StringComparison.Ordinal)
+            || !string.Equals(payload.EnvironmentId, query.Scope.EnvironmentId.Value, StringComparison.Ordinal)
+            || payload.ProtocolVersion != query.ProtocolVersion
+            || !string.Equals(payload.RegionId, query.RegionId?.Value, StringComparison.Ordinal)
+            || payload.ExcludeFull != query.ExcludeFull)
+        {
+            return false;
+        }
+
+        revision = payload.Revision;
+        return true;
+    }
+
+    public void Dispose() => _protector.Dispose();
+
+    public override string ToString() => "[SessionStreamCursorCodec: key and cursors redacted]";
+}
+
+internal sealed class SessionStreamCursorPayload
+{
+    [JsonRequired]
+    public string GameId { get; set; } = string.Empty;
+
+    [JsonRequired]
+    public string EnvironmentId { get; set; } = string.Empty;
+
+    [JsonRequired]
+    public uint ProtocolVersion { get; set; }
+
+    public string? RegionId { get; set; }
+
+    [JsonRequired]
+    public bool ExcludeFull { get; set; }
+
+    [JsonRequired]
+    public long Revision { get; set; }
+
+    [JsonRequired]
+    public long ExpiresAtUnixSeconds { get; set; }
+}

src/FinalFactory.Rendezvous.Server/Browser/SessionStreamService.cs

@@ -0,0 +1,172 @@
+using FinalFactory.Rendezvous.Contracts;
+using FinalFactory.Rendezvous.Server.State;
+
+namespace FinalFactory.Rendezvous.Server.Browser;
+
+internal sealed record SessionStreamReadResult(
+    bool RequiresReset,
+    IReadOnlyList<SessionStreamEvent> Events);
+
+internal sealed class SessionStreamSubscription : IDisposable
+{
+    private IDisposable? _lease;
+
+    public SessionStreamSubscription(
+        VisibleListingQuery query,
+        long revision,
+        bool requiresReset,
+        IDisposable lease)
+    {
+        Query = query;
+        Revision = revision;
+        RequiresReset = requiresReset;
+        _lease = lease;
+    }
+
+    public VisibleListingQuery Query { get; }
+    public long Revision { get; set; }
+    public bool RequiresReset { get; set; }
+
+    public void Dispose() => Interlocked.Exchange(ref _lease, null)?.Dispose();
+}
+
+internal sealed class SessionStreamService(
+    SessionChangeJournal changes,
+    SessionStreamCursorCodec cursors,
+    IWallClock clock)
+{
+    public BrowserServiceResult<SessionStreamSubscription> Subscribe(
+        BrowseSessionsRequest request,
+        string? cursor)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        RendezvousErrorCode validation = Validate(request);
+        if (validation != RendezvousErrorCode.None)
+        {
+            return new(validation);
+        }
+        VisibleListingQuery query = new(
+            new TenantScope(request.GameId, request.EnvironmentId),
+            request.ProtocolVersion,
+            request.RegionId,
+            ContractLimits.BrowserPageMaxItems,
+            ExcludeFull: request.ExcludeFull);
+        if (!changes.TrySubscribe(query.Scope, out IDisposable? lease) || lease is null)
+        {
+            return new(RendezvousErrorCode.CapacityExceeded);
+        }
+        bool validCursor = cursors.TryDecode(cursor, query, clock.UtcNow, out long revision);
+        if (!validCursor)
+        {
+            revision = changes.CurrentRevision;
+        }
+        return new(RendezvousErrorCode.None, new SessionStreamSubscription(
+            query,
+            revision,
+            requiresReset: !validCursor,
+            lease));
+    }
+
+    public SessionStreamReadResult Read(SessionStreamSubscription subscription)
+    {
+        ArgumentNullException.ThrowIfNull(subscription);
+        if (subscription.RequiresReset)
+        {
+            subscription.RequiresReset = false;
+            return new(true, []);
+        }
+
+        SessionChangeBatch batch = changes.ReadAfter(subscription.Revision);
+        if (batch.RequiresReset)
+        {
+            subscription.Revision = batch.CurrentRevision;
+            return new(true, []);
+        }
+        if (batch.Changes.Count == 0)
+        {
+            return new(false, []);
+        }
+
+        Dictionary<SessionListingId, PendingDelta> coalesced = [];
+        foreach (SessionChange change in batch.Changes)
+        {
+            bool beforeMatches = change.Before?.Matches(subscription.Query) == true;
+            bool afterMatches = change.After?.Matches(subscription.Query) == true;
+            if (!beforeMatches && !afterMatches)
+            {
+                continue;
+            }
+            coalesced[change.ListingId] = afterMatches
+                ? new(change.Revision, SessionStreamEventKind.SessionUpsert, change.After!.Listing)
+                : new(change.Revision, SessionStreamEventKind.SessionRemove, null);
+        }
+
+        subscription.Revision = batch.Changes[^1].Revision;
+        SessionStreamEvent[] events = coalesced
+            .OrderBy(static item => item.Value.Revision)
+            .Select(item => ToEvent(item.Key, item.Value, subscription.Query))
+            .ToArray();
+        return new(false, events);
+    }
+
+    public async Task<bool> WaitForChangeAsync(
+        SessionStreamSubscription subscription,
+        CancellationToken cancellationToken)
+    {
+        bool changed = await changes.WaitForChangeAsync(
+            subscription.Revision,
+            changes.Options.KeepaliveInterval,
+            cancellationToken).ConfigureAwait(false);
+        if (changed && changes.Options.CoalesceInterval > TimeSpan.Zero)
+        {
+            await Task.Delay(changes.Options.CoalesceInterval, cancellationToken)
+                .ConfigureAwait(false);
+        }
+        return changed;
+    }
+
+    public SessionStreamEvent ResetEvent(SessionStreamSubscription subscription) => new()
+    {
+        Kind = SessionStreamEventKind.Reset,
+        Cursor = cursors.Encode(subscription.Query, subscription.Revision, clock.UtcNow),
+    };
+
+    public SessionStreamEvent KeepaliveEvent(SessionStreamSubscription subscription) => new()
+    {
+        Kind = SessionStreamEventKind.Keepalive,
+        Cursor = cursors.Encode(subscription.Query, subscription.Revision, clock.UtcNow),
+    };
+
+    public TimeSpan MaximumConnectionDuration => changes.Options.MaximumConnectionDuration;
+
+    private SessionStreamEvent ToEvent(
+        SessionListingId listingId,
+        PendingDelta delta,
+        VisibleListingQuery query) => new()
+        {
+            Kind = delta.Kind,
+            Cursor = cursors.Encode(query, delta.Revision, clock.UtcNow),
+            Session = delta.Session,
+            ListingId = delta.Kind == SessionStreamEventKind.SessionRemove ? listingId : null,
+        };
+
+    private static RendezvousErrorCode Validate(BrowseSessionsRequest request)
+    {
+        RendezvousErrorCode version = ContractValidation.ValidateContractVersion(request.ContractVersion);
+        if (version != RendezvousErrorCode.None)
+        {
+            return version;
+        }
+        return string.IsNullOrEmpty(request.GameId.Value)
+            || string.IsNullOrEmpty(request.EnvironmentId.Value)
+            || request.ProtocolVersion == 0
+            || request.RegionId.HasValue && string.IsNullOrEmpty(request.RegionId.Value.Value)
+            ? RendezvousErrorCode.InvalidRequest
+            : RendezvousErrorCode.None;
+    }
+
+    private sealed record PendingDelta(
+        long Revision,
+        SessionStreamEventKind Kind,
+        SessionListing? Session);
+}

src/FinalFactory.Rendezvous.Server/Diagnostics/Assets/app.mjs

@@ -0,0 +1,615 @@
+const CONTRACT_VERSION = 1;
+const BROWSER_PAGE_LIMIT = 100;
+const REQUEST_TIMEOUT_MS = 10_000;
+const STREAM_FAILURE_LIMIT = 3;
+
+export class SessionProjection {
+  constructor(maximumSessions = 100) {
+    if (!Number.isInteger(maximumSessions) || maximumSessions < 1 || maximumSessions > 500) {
+      throw new RangeError("maximumSessions must be between 1 and 500");
+    }
+    this.maximumSessions = maximumSessions;
+    this.entries = new Map();
+    this.cursor = "";
+    this.hasMore = false;
+  }
+
+  replace(items, cursor, hasMore = false, updatedAt = Date.now()) {
+    if (!Array.isArray(items) || items.length > this.maximumSessions) {
+      return "overflow";
+    }
+    const next = new Map();
+    for (const session of items) {
+      if (!isPublicSession(session) || next.has(session.listingId)) {
+        return "invalid";
+      }
+      next.set(session.listingId, { session, updatedAt });
+    }
+    this.entries = next;
+    this.cursor = validCursor(cursor) ? cursor : "";
+    this.hasMore = Boolean(hasMore);
+    return "applied";
+  }
+
+  apply(event, updatedAt = Date.now()) {
+    if (!event || event.contractVersion !== CONTRACT_VERSION || !validCursor(event.cursor)) {
+      return "invalid";
+    }
+    if (event.kind === "sessionUpsert" && isPublicSession(event.session) && event.listingId == null) {
+      if (!this.entries.has(event.session.listingId)
+          && this.entries.size >= this.maximumSessions) {
+        return "overflow";
+      }
+      this.entries.set(event.session.listingId, { session: event.session, updatedAt });
+      this.cursor = event.cursor;
+      return "applied";
+    }
+    if (event.kind === "sessionRemove"
+        && typeof event.listingId === "string"
+        && event.listingId.length > 0
+        && event.session == null) {
+      this.entries.delete(event.listingId);
+      this.cursor = event.cursor;
+      return this.hasMore ? "refresh" : "applied";
+    }
+    if (event.kind === "keepalive" && event.session == null && event.listingId == null) {
+      this.cursor = event.cursor;
+      return "keepalive";
+    }
+    if (event.kind === "reset" && event.session == null && event.listingId == null) {
+      this.cursor = event.cursor;
+      return "reset";
+    }
+    return "invalid";
+  }
+
+  sessions() {
+    return [...this.entries.values()]
+      .sort((left, right) => left.session.listingId.localeCompare(right.session.listingId));
+  }
+}
+
+export function safeText(value, maximumLength = 160) {
+  const text = typeof value === "string" ? value : String(value ?? "");
+  const visible = text.replace(/[\u0000-\u001f\u007f]/gu, "�");
+  return visible.length <= maximumLength
+    ? visible
+    : `${visible.slice(0, Math.max(0, maximumLength - 1))}…`;
+}
+
+export function buildBrowseUrl(filter) {
+  validateFilter(filter);
+  const query = new URLSearchParams({
+    contractVersion: String(CONTRACT_VERSION),
+    gameId: filter.gameId,
+    environmentId: filter.environmentId,
+    protocolVersion: String(filter.protocolVersion),
+    regionId: filter.regionId,
+    pageSize: String(Math.min(BROWSER_PAGE_LIMIT, filter.pageSize ?? BROWSER_PAGE_LIMIT)),
+    excludeFull: String(Boolean(filter.excludeFull)),
+  });
+  return `/v1/sessions?${query}`;
+}
+
+export function buildStreamUrl(filter, cursor) {
+  validateFilter(filter);
+  if (!validCursor(cursor)) {
+    throw new TypeError("A bounded stream cursor is required");
+  }
+  const query = new URLSearchParams({
+    contractVersion: String(CONTRACT_VERSION),
+    gameId: filter.gameId,
+    environmentId: filter.environmentId,
+    protocolVersion: String(filter.protocolVersion),
+    regionId: filter.regionId,
+    excludeFull: String(Boolean(filter.excludeFull)),
+    streamCursor: cursor,
+  });
+  return `/v1/sessions/stream?${query}`;
+}
+
+export function chooseSnapshotTransport(hasMore, pollingOnly) {
+  if (pollingOnly) {
+    return "pollingOnly";
+  }
+  return hasMore ? "boundedPolling" : "stream";
+}
+
+function validCursor(value) {
+  return typeof value === "string"
+    && value.length > 0
+    && value.length <= 1024
+    && /^[\x21-\x7e]+$/u.test(value);
+}
+
+function isPublicSession(session) {
+  return session != null
+    && session.contractVersion === CONTRACT_VERSION
+    && typeof session.listingId === "string"
+    && session.listingId.length > 0
+    && typeof session.gameId === "string"
+    && typeof session.environmentId === "string"
+    && typeof session.regionId === "string"
+    && Number.isInteger(session.protocolVersion)
+    && session.protocolVersion > 0
+    && typeof session.buildVersion === "string"
+    && typeof session.displayName === "string"
+    && session.visibility === "public"
+    && session.capacity != null
+    && Number.isInteger(session.capacity.currentPlayers)
+    && Number.isInteger(session.capacity.maximumPlayers)
+    && session.capacity.currentPlayers >= 0
+    && session.capacity.maximumPlayers >= 1
+    && session.capacity.currentPlayers <= session.capacity.maximumPlayers
+    && session.metadata != null
+    && typeof session.metadata === "object"
+    && !Array.isArray(session.metadata);
+}
+
+function validateFilter(filter) {
+  if (!filter
+      || typeof filter.gameId !== "string"
+      || typeof filter.environmentId !== "string"
+      || typeof filter.regionId !== "string"
+      || !Number.isInteger(filter.protocolVersion)
+      || filter.protocolVersion <= 0) {
+    throw new TypeError("The selected diagnostic filter is invalid");
+  }
+}
+
+function startDashboard() {
+  const elements = {
+    form: document.querySelector("#filters"),
+    game: document.querySelector("#game-filter"),
+    environment: document.querySelector("#environment-filter"),
+    protocol: document.querySelector("#protocol-filter"),
+    region: document.querySelector("#region-filter"),
+    capacity: document.querySelector("#capacity-filter"),
+    error: document.querySelector("#filter-error"),
+    reconnect: document.querySelector("#reconnect-button"),
+    reset: document.querySelector("#reset-button"),
+    poll: document.querySelector("#poll-button"),
+    streamStatus: document.querySelector("#stream-status"),
+    transportState: document.querySelector("#transport-state"),
+    projectionState: document.querySelector("#projection-state"),
+    lastUpdate: document.querySelector("#last-update"),
+    sessionCount: document.querySelector("#session-count"),
+    results: document.querySelector(".results-panel"),
+    resultsSummary: document.querySelector("#results-summary"),
+    list: document.querySelector("#session-list"),
+    empty: document.querySelector("#empty-state"),
+  };
+
+  const state = {
+    configuration: null,
+    projection: null,
+    activeFilter: null,
+    source: null,
+    pollingTimer: null,
+    requestController: null,
+    streamFailures: 0,
+    pollingOnly: false,
+    renderPending: false,
+    lastSuccess: 0,
+  };
+
+  function setStatus(kind, message, transport = message) {
+    document.body.dataset.streamState = kind;
+    elements.streamStatus.textContent = message;
+    elements.transportState.textContent = transport;
+  }
+
+  function setFormError(message = "") {
+    elements.error.textContent = message;
+    elements.error.hidden = message.length === 0;
+  }
+
+  function populate(select, values, previous) {
+    select.replaceChildren();
+    for (const value of values) {
+      const option = document.createElement("option");
+      option.value = String(value);
+      option.textContent = safeText(value, 80);
+      select.append(option);
+    }
+    if (values.some((value) => String(value) === previous)) {
+      select.value = previous;
+    }
+  }
+
+  function selectedScope() {
+    return state.configuration?.scopes.find((scope) =>
+      scope.gameId === elements.game.value
+      && scope.environmentId === elements.environment.value) ?? null;
+  }
+
+  function updateEnvironmentOptions() {
+    const prior = elements.environment.value;
+    const environments = state.configuration.scopes
+      .filter((scope) => scope.gameId === elements.game.value)
+      .map((scope) => scope.environmentId);
+    populate(elements.environment, environments, prior);
+    updateScopeOptions();
+  }
+
+  function updateScopeOptions() {
+    const scope = selectedScope();
+    populate(elements.protocol, scope?.protocolVersions ?? [], elements.protocol.value);
+    populate(elements.region, scope?.regions ?? [], elements.region.value);
+  }
+
+  function currentFilter() {
+    const scope = selectedScope();
+    const protocolVersion = Number(elements.protocol.value);
+    if (!scope
+        || !scope.protocolVersions.includes(protocolVersion)
+        || !scope.regions.includes(elements.region.value)) {
+      throw new TypeError("Choose one of the configured game, environment, protocol, and region combinations.");
+    }
+    return {
+      gameId: scope.gameId,
+      environmentId: scope.environmentId,
+      protocolVersion,
+      regionId: elements.region.value,
+      excludeFull: elements.capacity.value === "open",
+      pageSize: Math.min(BROWSER_PAGE_LIMIT, state.configuration.maximumRenderedSessions),
+    };
+  }
+
+  function stopLiveWork() {
+    if (state.source) {
+      state.source.close();
+      state.source = null;
+    }
+    if (state.pollingTimer) {
+      clearTimeout(state.pollingTimer);
+      state.pollingTimer = null;
+    }
+    if (state.requestController) {
+      state.requestController.abort();
+      state.requestController = null;
+    }
+  }
+
+  function markSuccess(message) {
+    state.lastSuccess = Date.now();
+    elements.lastUpdate.dateTime = new Date(state.lastSuccess).toISOString();
+    elements.lastUpdate.textContent = "Just now";
+    elements.resultsSummary.textContent = message;
+  }
+
+  function scheduleRender() {
+    if (state.renderPending) {
+      return;
+    }
+    state.renderPending = true;
+    requestAnimationFrame(() => {
+      state.renderPending = false;
+      renderProjection();
+    });
+  }
+
+  function appendDetail(list, term, description) {
+    const dt = document.createElement("dt");
+    dt.textContent = term;
+    const dd = document.createElement("dd");
+    dd.textContent = safeText(description, 160);
+    list.append(dt, dd);
+  }
+
+  function sessionCard(entry) {
+    const session = entry.session;
+    const article = document.createElement("article");
+    article.className = "session-card";
+    article.setAttribute("role", "listitem");
+    article.dataset.updatedAt = String(entry.updatedAt);
+
+    const heading = document.createElement("div");
+    heading.className = "card-heading";
+    const title = document.createElement("h3");
+    title.textContent = safeText(session.displayName, 120);
+    const region = document.createElement("span");
+    region.className = "region-badge";
+    region.textContent = safeText(session.regionId, 48);
+    heading.append(title, region);
+
+    const details = document.createElement("dl");
+    details.className = "session-detail";
+    appendDetail(details, "Build", session.buildVersion);
+    appendDetail(details, "Protocol", session.protocolVersion);
+    appendDetail(details, "Visibility", "Public");
+    appendDetail(details, "Presence", "Recently verified");
+
+    const capacity = document.createElement("div");
+    capacity.className = "capacity-row";
+    const capacityCopy = document.createElement("div");
+    capacityCopy.className = "capacity-copy";
+    const capacityLabel = document.createElement("span");
+    capacityLabel.textContent = "Advisory capacity";
+    const capacityValue = document.createElement("span");
+    capacityValue.textContent = `${session.capacity.currentPlayers} / ${session.capacity.maximumPlayers}`;
+    capacityCopy.append(capacityLabel, capacityValue);
+    const meter = document.createElement("meter");
+    meter.min = 0;
+    meter.max = session.capacity.maximumPlayers;
+    meter.value = session.capacity.currentPlayers;
+    meter.setAttribute("aria-label", `Advisory capacity ${capacityValue.textContent}`);
+    capacity.append(capacityCopy, meter);
+
+    const metadata = document.createElement("ul");
+    metadata.className = "metadata-list";
+    for (const [key, value] of Object.entries(session.metadata).slice(0, 16)) {
+      const item = document.createElement("li");
+      item.textContent = `${safeText(key, 48)}: ${safeText(value, 96)}`;
+      metadata.append(item);
+    }
+    if (metadata.childElementCount === 0) {
+      const item = document.createElement("li");
+      item.textContent = "No public metadata";
+      metadata.append(item);
+    }
+
+    const updated = document.createElement("p");
+    updated.className = "updated-age";
+    updated.textContent = "Updated just now";
+    article.append(heading, details, capacity, metadata, updated);
+    return article;
+  }
+
+  function renderProjection() {
+    const entries = state.projection?.sessions() ?? [];
+    const fragment = document.createDocumentFragment();
+    for (const entry of entries) {
+      fragment.append(sessionCard(entry));
+    }
+    elements.list.replaceChildren(fragment);
+    elements.sessionCount.textContent = String(entries.length);
+    elements.empty.hidden = entries.length !== 0;
+    elements.projectionState.textContent = state.projection?.hasMore
+      ? "Bounded snapshot; polling"
+      : "Snapshot plus ordered deltas";
+    elements.results.setAttribute("aria-busy", "false");
+  }
+
+  function updateAges() {
+    const now = Date.now();
+    if (state.lastSuccess > 0) {
+      const age = Math.max(0, Math.floor((now - state.lastSuccess) / 1000));
+      elements.lastUpdate.textContent = age < 5 ? "Just now" : `${age} seconds ago`;
+    }
+    for (const card of elements.list.querySelectorAll(".session-card")) {
+      const age = Math.max(0, Math.floor((now - Number(card.dataset.updatedAt)) / 1000));
+      const copy = card.querySelector(".updated-age");
+      copy.textContent = age < 5 ? "Updated just now" : `Updated ${age} seconds ago`;
+    }
+  }
+
+  async function readJson(url) {
+    const controller = new AbortController();
+    state.requestController = controller;
+    const timeout = setTimeout(() => controller.abort(), REQUEST_TIMEOUT_MS);
+    try {
+      const response = await fetch(url, {
+        cache: "no-store",
+        credentials: "same-origin",
+        headers: { Accept: "application/json" },
+        signal: controller.signal,
+      });
+      if (!response.ok) {
+        throw new Error(`The service returned HTTP ${response.status}.`);
+      }
+      return await response.json();
+    } finally {
+      clearTimeout(timeout);
+      if (state.requestController === controller) {
+        state.requestController = null;
+      }
+    }
+  }
+
+  function schedulePolling() {
+    if (state.pollingTimer) {
+      clearTimeout(state.pollingTimer);
+    }
+    state.pollingTimer = setTimeout(
+      () => fetchSnapshot("poll").catch(showServiceError),
+      state.configuration.pollIntervalSeconds * 1000,
+    );
+  }
+
+  function usePolling(message = "Polling fallback active") {
+    if (state.source) {
+      state.source.close();
+      state.source = null;
+    }
+    setStatus("polling", message, "Polling fallback");
+    schedulePolling();
+  }
+
+  function showServiceError(error) {
+    const message = error?.name === "AbortError"
+      ? "The service did not answer within the request deadline."
+      : safeText(error?.message || "The service is unavailable.", 200);
+    setStatus("error", "Service unavailable", "Unavailable");
+    elements.resultsSummary.textContent = `${message} Retrying with bounded polling.`;
+    elements.results.setAttribute("aria-busy", "false");
+    usePolling("Service unavailable; polling retry scheduled");
+  }
+
+  async function fetchSnapshot(reason = "manual") {
+    if (!state.activeFilter) {
+      return;
+    }
+    if (state.requestController) {
+      state.requestController.abort();
+    }
+    elements.results.setAttribute("aria-busy", "true");
+    if (reason !== "poll") {
+      setStatus("reconnecting", "Loading a fresh snapshot", "Snapshot request");
+    }
+    const response = await readJson(buildBrowseUrl(state.activeFilter));
+    if (response.contractVersion !== CONTRACT_VERSION
+        || !Array.isArray(response.items)
+        || !validCursor(response.streamCursor)) {
+      throw new Error("The service returned an invalid browser snapshot.");
+    }
+    const outcome = state.projection.replace(
+      response.items,
+      response.streamCursor,
+      Boolean(response.nextCursor),
+    );
+    if (outcome !== "applied") {
+      throw new Error("The bounded browser snapshot could not be applied safely.");
+    }
+    scheduleRender();
+    markSuccess(`${response.items.length} public session${response.items.length === 1 ? "" : "s"} in the fresh snapshot.`);
+    const transport = chooseSnapshotTransport(Boolean(response.nextCursor), state.pollingOnly);
+    if (transport !== "stream") {
+      if (transport === "pollingOnly") {
+        usePolling("Polling only selected");
+        return;
+      }
+      usePolling("More sessions exist than this bounded view; polling keeps it authoritative");
+      return;
+    }
+    connectStream(response.streamCursor);
+  }
+
+  function handleStreamEvent(serialized, expectedKind) {
+    let event;
+    try {
+      event = JSON.parse(serialized);
+    } catch {
+      usePolling("Invalid stream data; polling fallback active");
+      return;
+    }
+    if (event.kind !== expectedKind) {
+      usePolling("Unexpected stream event; polling fallback active");
+      return;
+    }
+    const outcome = state.projection.apply(event);
+    if (outcome === "invalid" || outcome === "overflow" || outcome === "refresh") {
+      fetchSnapshot("stream-recovery").catch(showServiceError);
+      return;
+    }
+    if (outcome === "reset") {
+      setStatus("reset", "Cursor reset; refreshing snapshot", "Cursor reset");
+      fetchSnapshot("reset").catch(showServiceError);
+      return;
+    }
+    if (outcome === "keepalive") {
+      markSuccess("Live connection healthy; no listing changes.");
+      return;
+    }
+    state.streamFailures = 0;
+    scheduleRender();
+    markSuccess(expectedKind === "sessionUpsert"
+      ? "Applied a live session add or update."
+      : "Applied a live session removal.");
+  }
+
+  function connectStream(cursor, corrupt = false) {
+    if (state.pollingTimer) {
+      clearTimeout(state.pollingTimer);
+      state.pollingTimer = null;
+    }
+    if (state.source) {
+      state.source.close();
+    }
+    const selectedCursor = corrupt
+      ? `${cursor.slice(0, -1)}${cursor.endsWith("a") ? "b" : "a"}`
+      : cursor;
+    setStatus(corrupt ? "reset" : "reconnecting",
+      corrupt ? "Testing cursor reset" : "Connecting live updates",
+      corrupt ? "Cursor reset test" : "SSE reconnecting");
+    const source = new EventSource(buildStreamUrl(state.activeFilter, selectedCursor));
+    state.source = source;
+    source.addEventListener("open", () => {
+      if (state.source !== source) {
+        return;
+      }
+      state.streamFailures = 0;
+      setStatus("connected", "Live updates connected", "SSE live");
+    });
+    for (const [name, kind] of [
+      ["session_upsert", "sessionUpsert"],
+      ["session_remove", "sessionRemove"],
+      ["reset", "reset"],
+      ["keepalive", "keepalive"],
+    ]) {
+      source.addEventListener(name, (message) => {
+        if (state.source === source) {
+          handleStreamEvent(message.data, kind);
+        }
+      });
+    }
+    source.addEventListener("error", () => {
+      if (state.source !== source) {
+        return;
+      }
+      state.streamFailures += 1;
+      if (state.streamFailures >= STREAM_FAILURE_LIMIT || source.readyState === EventSource.CLOSED) {
+        usePolling("Live stream unavailable; polling fallback active");
+      } else {
+        setStatus("reconnecting", "Live stream interrupted; reconnecting", "SSE reconnecting");
+      }
+    });
+  }
+
+  async function loadConfiguration() {
+    const configuration = await readJson("/diagnostics/config.json");
+    if (configuration.contractVersion !== CONTRACT_VERSION
+        || !Array.isArray(configuration.scopes)
+        || configuration.scopes.length < 1
+        || !Number.isInteger(configuration.pollIntervalSeconds)
+        || !Number.isInteger(configuration.maximumRenderedSessions)) {
+      throw new Error("The diagnostic configuration is invalid.");
+    }
+    state.configuration = configuration;
+    state.projection = new SessionProjection(configuration.maximumRenderedSessions);
+    populate(elements.game, [...new Set(configuration.scopes.map((scope) => scope.gameId))], "");
+    updateEnvironmentOptions();
+    state.activeFilter = currentFilter();
+    await fetchSnapshot("startup");
+  }
+
+  elements.game.addEventListener("change", updateEnvironmentOptions);
+  elements.environment.addEventListener("change", updateScopeOptions);
+  elements.form.addEventListener("submit", (event) => {
+    event.preventDefault();
+    try {
+      setFormError();
+      stopLiveWork();
+      state.pollingOnly = false;
+      state.activeFilter = currentFilter();
+      state.projection = new SessionProjection(state.configuration.maximumRenderedSessions);
+      fetchSnapshot("filter").catch(showServiceError);
+    } catch (error) {
+      setFormError(safeText(error.message, 200));
+    }
+  });
+  elements.reconnect.addEventListener("click", () => {
+    if (state.projection?.cursor) {
+      state.pollingOnly = false;
+      connectStream(state.projection.cursor);
+    }
+  });
+  elements.reset.addEventListener("click", () => {
+    if (state.projection?.cursor) {
+      state.pollingOnly = false;
+      connectStream(state.projection.cursor, true);
+    }
+  });
+  elements.poll.addEventListener("click", () => {
+    state.pollingOnly = true;
+    usePolling("Polling only selected deliberately");
+    fetchSnapshot("poll").catch(showServiceError);
+  });
+  window.addEventListener("pagehide", stopLiveWork, { once: true });
+  setInterval(updateAges, 5000);
+  loadConfiguration().catch(showServiceError);
+}
+
+if (typeof document !== "undefined") {
+  startDashboard();
+}

src/FinalFactory.Rendezvous.Server/Diagnostics/Assets/index.html

@@ -0,0 +1,120 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <meta name="color-scheme" content="dark">
+  <title>Session diagnostics — Rendezvous</title>
+  <link rel="stylesheet" href="/diagnostics/styles.css">
+  <script type="module" src="/diagnostics/app.mjs"></script>
+</head>
+<body>
+  <a class="skip-link" href="#main-content">Skip to session results</a>
+  <header class="site-header">
+    <div>
+      <p class="eyebrow">Final Factory infrastructure</p>
+      <h1>Rendezvous session diagnostics</h1>
+      <p class="lede">A read-only view of public session discovery. Capacity is advisory; joining always revalidates current state.</p>
+    </div>
+    <div class="connection-state" aria-live="polite" aria-atomic="true">
+      <span class="status-dot" aria-hidden="true"></span>
+      <span id="stream-status">Loading configuration</span>
+    </div>
+  </header>
+
+  <main id="main-content" tabindex="-1">
+    <section class="filter-panel" aria-labelledby="filter-heading">
+      <div class="section-heading">
+        <div>
+          <p class="eyebrow">Public browser scope</p>
+          <h2 id="filter-heading">Choose a configured session view</h2>
+        </div>
+        <p class="boundary-note">This page has no join, publish, or operator authority.</p>
+      </div>
+
+      <form id="filters" novalidate>
+        <div class="filter-grid">
+          <label>
+            <span>Game</span>
+            <select id="game-filter" name="game" required></select>
+          </label>
+          <label>
+            <span>Environment</span>
+            <select id="environment-filter" name="environment" required></select>
+          </label>
+          <label>
+            <span>Protocol</span>
+            <select id="protocol-filter" name="protocol" required></select>
+          </label>
+          <label>
+            <span>Region</span>
+            <select id="region-filter" name="region" required></select>
+          </label>
+          <label>
+            <span>Availability</span>
+            <select id="capacity-filter" name="capacity">
+              <option value="open">Open slots only</option>
+              <option value="all">Include full sessions</option>
+            </select>
+          </label>
+          <label>
+            <span>Visibility</span>
+            <select id="visibility-filter" name="visibility" disabled>
+              <option value="public">Public only</option>
+            </select>
+          </label>
+        </div>
+        <p id="filter-error" class="form-error" role="alert" hidden></p>
+        <div class="button-row">
+          <button class="button primary" type="submit">Apply filters</button>
+          <button class="button" id="reconnect-button" type="button">Reconnect now</button>
+          <button class="button" id="reset-button" type="button">Test reset recovery</button>
+          <button class="button" id="poll-button" type="button">Use polling only</button>
+        </div>
+      </form>
+    </section>
+
+    <section class="summary-panel" aria-labelledby="summary-heading">
+      <h2 id="summary-heading" class="visually-hidden">Current diagnostic state</h2>
+      <dl class="summary-grid">
+        <div>
+          <dt>Sessions shown</dt>
+          <dd id="session-count">0</dd>
+        </div>
+        <div>
+          <dt>Transport</dt>
+          <dd id="transport-state">Starting</dd>
+        </div>
+        <div>
+          <dt>Last successful update</dt>
+          <dd><time id="last-update">Not yet</time></dd>
+        </div>
+        <div>
+          <dt>Projection</dt>
+          <dd id="projection-state">Waiting for snapshot</dd>
+        </div>
+      </dl>
+    </section>
+
+    <section class="results-panel" aria-labelledby="results-heading" aria-busy="true">
+      <div class="section-heading results-heading">
+        <div>
+          <p class="eyebrow">Bounded public projection</p>
+          <h2 id="results-heading">Available sessions</h2>
+        </div>
+        <p id="results-summary" role="status" aria-live="polite">Loading a fresh snapshot…</p>
+      </div>
+      <div id="session-list" class="session-grid" role="list"></div>
+      <div id="empty-state" class="empty-state" hidden>
+        <h3>No compatible public sessions</h3>
+        <p>The service answered successfully, but this configured filter currently has no listings.</p>
+      </div>
+    </section>
+  </main>
+
+  <footer>
+    <p>Read-only diagnostics · no credentials stored · no gameplay or administration</p>
+  </footer>
+  <noscript>This diagnostic requires JavaScript to consume the public snapshot and event stream.</noscript>
+</body>
+</html>

src/FinalFactory.Rendezvous.Server/Diagnostics/Assets/styles.css

@@ -0,0 +1,505 @@
+:root {
+  color-scheme: dark;
+  --bg: #071019;
+  --surface: #101c28;
+  --surface-raised: #172737;
+  --border: #375066;
+  --text: #f2f7fb;
+  --muted: #b6c8d6;
+  --accent: #55d7b5;
+  --accent-strong: #7ce9cc;
+  --accent-ink: #04231c;
+  --warning: #ffd479;
+  --danger: #ff9f9f;
+  --focus: #ffd479;
+  --radius: 0.75rem;
+  --space-1: 0.5rem;
+  --space-2: 0.75rem;
+  --space-3: 1rem;
+  --space-4: 1.5rem;
+  --space-5: 2rem;
+  --space-6: 3rem;
+  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
+  font-size: 100%;
+  line-height: 1.55;
+}
+
+* {
+  box-sizing: border-box;
+}
+
+html {
+  min-width: 20rem;
+  background: var(--bg);
+}
+
+body {
+  min-height: 100vh;
+  margin: 0;
+  color: var(--text);
+  background:
+    radial-gradient(circle at 10% -10%, rgb(36 103 104 / 35%), transparent 32rem),
+    linear-gradient(180deg, #09141f 0%, var(--bg) 50%);
+}
+
+button,
+select {
+  font: inherit;
+}
+
+button,
+select,
+a {
+  -webkit-tap-highlight-color: transparent;
+}
+
+:focus-visible {
+  outline: 0.2rem solid var(--focus);
+  outline-offset: 0.2rem;
+}
+
+.skip-link {
+  position: fixed;
+  z-index: 10;
+  top: var(--space-2);
+  left: var(--space-2);
+  padding: var(--space-2) var(--space-3);
+  color: #071019;
+  background: var(--focus);
+  border-radius: 0.4rem;
+  font-weight: 800;
+  transform: translateY(-200%);
+}
+
+.skip-link:focus {
+  transform: translateY(0);
+}
+
+.site-header,
+main,
+footer {
+  width: min(80rem, calc(100% - 2rem));
+  margin-inline: auto;
+}
+
+.site-header {
+  display: flex;
+  align-items: end;
+  justify-content: space-between;
+  gap: var(--space-5);
+  padding-block: var(--space-6) var(--space-5);
+}
+
+h1,
+h2,
+h3,
+p {
+  margin-top: 0;
+}
+
+h1 {
+  max-width: 18ch;
+  margin-bottom: var(--space-2);
+  font-size: clamp(2rem, 6vw, 4.25rem);
+  line-height: 1.02;
+  letter-spacing: -0.045em;
+}
+
+h2 {
+  margin-bottom: var(--space-1);
+  font-size: clamp(1.35rem, 3vw, 2rem);
+  line-height: 1.2;
+}
+
+h3 {
+  margin-bottom: var(--space-1);
+  font-size: 1.1rem;
+}
+
+.eyebrow {
+  margin-bottom: var(--space-1);
+  color: var(--accent-strong);
+  font-size: 0.78rem;
+  font-weight: 800;
+  letter-spacing: 0.14em;
+  text-transform: uppercase;
+}
+
+.lede {
+  max-width: 65ch;
+  margin-bottom: 0;
+  color: var(--muted);
+  font-size: 1.05rem;
+}
+
+.connection-state {
+  display: inline-flex;
+  min-height: 2.75rem;
+  align-items: center;
+  gap: var(--space-2);
+  padding: var(--space-2) var(--space-3);
+  border: 1px solid var(--border);
+  border-radius: 999px;
+  background: rgb(16 28 40 / 88%);
+  color: var(--muted);
+  font-weight: 700;
+  white-space: nowrap;
+}
+
+.status-dot {
+  width: 0.7rem;
+  height: 0.7rem;
+  border: 2px solid currentColor;
+  border-radius: 50%;
+  background: currentColor;
+}
+
+body[data-stream-state="connected"] .connection-state {
+  color: var(--accent-strong);
+}
+
+body[data-stream-state="reconnecting"] .connection-state,
+body[data-stream-state="polling"] .connection-state,
+body[data-stream-state="reset"] .connection-state {
+  color: var(--warning);
+}
+
+body[data-stream-state="error"] .connection-state {
+  color: var(--danger);
+}
+
+main {
+  display: grid;
+  gap: var(--space-4);
+}
+
+.filter-panel,
+.summary-panel,
+.results-panel {
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  background: rgb(16 28 40 / 94%);
+  box-shadow: 0 1rem 3rem rgb(0 0 0 / 18%);
+}
+
+.filter-panel,
+.results-panel {
+  padding: clamp(1rem, 4vw, 2rem);
+}
+
+.section-heading {
+  display: flex;
+  align-items: start;
+  justify-content: space-between;
+  gap: var(--space-4);
+  margin-bottom: var(--space-4);
+}
+
+.boundary-note,
+#results-summary {
+  max-width: 34rem;
+  margin-bottom: 0;
+  color: var(--muted);
+}
+
+.filter-grid {
+  display: grid;
+  grid-template-columns: repeat(3, minmax(0, 1fr));
+  gap: var(--space-3);
+}
+
+label {
+  display: grid;
+  gap: 0.35rem;
+  color: var(--muted);
+  font-size: 0.9rem;
+  font-weight: 750;
+}
+
+select {
+  width: 100%;
+  min-height: 2.75rem;
+  padding: 0.6rem 2.4rem 0.6rem 0.75rem;
+  border: 1px solid #587189;
+  border-radius: 0.45rem;
+  color: var(--text);
+  background: #0b1722;
+}
+
+select:disabled {
+  color: #9fb0bd;
+  border-style: dashed;
+  opacity: 1;
+}
+
+.button-row {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--space-2);
+  margin-top: var(--space-4);
+}
+
+.button {
+  min-height: 2.75rem;
+  padding: 0.65rem 1rem;
+  border: 1px solid #6a8298;
+  border-radius: 0.45rem;
+  color: var(--text);
+  background: var(--surface-raised);
+  cursor: pointer;
+  font-weight: 800;
+}
+
+.button:hover {
+  border-color: var(--accent-strong);
+  background: #21384a;
+}
+
+.button:active {
+  transform: translateY(1px);
+}
+
+.button.primary {
+  color: var(--accent-ink);
+  border-color: var(--accent);
+  background: var(--accent);
+}
+
+.button.primary:hover {
+  background: var(--accent-strong);
+}
+
+.form-error {
+  margin: var(--space-3) 0 0;
+  color: var(--danger);
+  font-weight: 750;
+}
+
+.summary-panel {
+  padding: 0;
+  overflow: hidden;
+}
+
+.summary-grid {
+  display: grid;
+  grid-template-columns: repeat(4, minmax(0, 1fr));
+  margin: 0;
+}
+
+.summary-grid > div {
+  min-width: 0;
+  padding: var(--space-3) var(--space-4);
+  border-right: 1px solid var(--border);
+}
+
+.summary-grid > div:last-child {
+  border-right: 0;
+}
+
+.summary-grid dt {
+  color: var(--muted);
+  font-size: 0.78rem;
+  font-weight: 700;
+}
+
+.summary-grid dd {
+  margin: 0.25rem 0 0;
+  overflow-wrap: anywhere;
+  font-size: 1.05rem;
+  font-weight: 800;
+}
+
+.results-heading {
+  align-items: end;
+}
+
+.session-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(min(100%, 19rem), 1fr));
+  gap: var(--space-3);
+}
+
+.session-card {
+  min-width: 0;
+  padding: var(--space-3);
+  border: 1px solid #496177;
+  border-radius: 0.6rem;
+  background: #0b1722;
+}
+
+.card-heading {
+  display: flex;
+  align-items: start;
+  justify-content: space-between;
+  gap: var(--space-2);
+}
+
+.card-heading h3 {
+  overflow-wrap: anywhere;
+}
+
+.region-badge {
+  flex: 0 0 auto;
+  padding: 0.15rem 0.5rem;
+  border: 1px solid #597187;
+  border-radius: 999px;
+  color: var(--muted);
+  font-size: 0.75rem;
+  font-weight: 750;
+}
+
+.session-detail {
+  display: grid;
+  grid-template-columns: minmax(5rem, auto) 1fr;
+  gap: 0.25rem var(--space-2);
+  margin: var(--space-3) 0 0;
+  font-size: 0.9rem;
+}
+
+.session-detail dt {
+  color: var(--muted);
+}
+
+.session-detail dd {
+  min-width: 0;
+  margin: 0;
+  overflow-wrap: anywhere;
+}
+
+.capacity-row {
+  margin-top: var(--space-3);
+}
+
+.capacity-copy {
+  display: flex;
+  justify-content: space-between;
+  gap: var(--space-2);
+  margin-bottom: 0.35rem;
+  color: var(--muted);
+  font-size: 0.85rem;
+}
+
+meter {
+  width: 100%;
+  height: 0.65rem;
+  accent-color: var(--accent);
+}
+
+.metadata-list {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.35rem;
+  margin: var(--space-3) 0 0;
+  padding: 0;
+  list-style: none;
+}
+
+.metadata-list li {
+  max-width: 100%;
+  padding: 0.2rem 0.45rem;
+  overflow-wrap: anywhere;
+  border-radius: 0.3rem;
+  color: #d6e4ed;
+  background: #1b2b39;
+  font-size: 0.78rem;
+}
+
+.updated-age {
+  margin: var(--space-3) 0 0;
+  color: var(--muted);
+  font-size: 0.78rem;
+}
+
+.empty-state {
+  padding: var(--space-6) var(--space-3);
+  text-align: center;
+  border: 1px dashed #587189;
+  border-radius: 0.6rem;
+  color: var(--muted);
+}
+
+.empty-state h3 {
+  color: var(--text);
+}
+
+footer {
+  padding-block: var(--space-5);
+  color: var(--muted);
+  font-size: 0.85rem;
+  text-align: center;
+}
+
+.visually-hidden {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  padding: 0;
+  overflow: hidden;
+  clip: rect(0, 0, 0, 0);
+  white-space: nowrap;
+  border: 0;
+}
+
+[hidden] {
+  display: none !important;
+}
+
+@media (max-width: 56rem) {
+  .site-header,
+  .section-heading {
+    align-items: start;
+    flex-direction: column;
+  }
+
+  .filter-grid,
+  .summary-grid {
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+  }
+
+  .summary-grid > div:nth-child(2) {
+    border-right: 0;
+  }
+
+  .summary-grid > div:nth-child(-n + 2) {
+    border-bottom: 1px solid var(--border);
+  }
+}
+
+@media (max-width: 36rem) {
+  .site-header,
+  main,
+  footer {
+    width: min(100% - 1rem, 80rem);
+  }
+
+  .site-header {
+    padding-block: var(--space-5) var(--space-4);
+  }
+
+  .filter-grid,
+  .summary-grid {
+    grid-template-columns: 1fr;
+  }
+
+  .summary-grid > div {
+    border-right: 0;
+    border-bottom: 1px solid var(--border);
+  }
+
+  .summary-grid > div:last-child {
+    border-bottom: 0;
+  }
+
+  .button {
+    width: 100%;
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  *,
+  *::before,
+  *::after {
+    scroll-behavior: auto !important;
+    transition-duration: 0.01ms !important;
+  }
+}

src/FinalFactory.Rendezvous.Server/Diagnostics/DiagnosticDashboardEndpoints.cs

@@ -0,0 +1,111 @@
+using System.Reflection;
+using FinalFactory.Rendezvous.Contracts;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Options;
+
+namespace FinalFactory.Rendezvous.Server.Diagnostics;
+
+internal static class DiagnosticDashboardEndpoints
+{
+    private const string ContentSecurityPolicy =
+        "default-src 'none'; base-uri 'none'; connect-src 'self'; "
+        + "font-src 'self'; form-action 'none'; frame-ancestors 'none'; "
+        + "img-src 'self'; manifest-src 'none'; object-src 'none'; "
+        + "script-src 'self'; style-src 'self'";
+    private static readonly byte[] Index = ReadAsset("index.html");
+    private static readonly byte[] Script = ReadAsset("app.mjs");
+    private static readonly byte[] Styles = ReadAsset("styles.css");
+
+    public static IEndpointRouteBuilder MapDiagnosticDashboardEndpoints(
+        this IEndpointRouteBuilder endpoints)
+    {
+        RouteGroupBuilder dashboard = endpoints.MapGroup("/diagnostics")
+            .ExcludeFromDescription();
+        dashboard.MapGet("", ServeIndex);
+        dashboard.MapGet("/app.mjs", ServeScript);
+        dashboard.MapGet("/styles.css", ServeStyles);
+        dashboard.MapGet("/config.json", ServeConfiguration);
+        return endpoints;
+    }
+
+    private static IResult ServeIndex(
+        HttpContext context,
+        [FromServices] IOptions<DiagnosticDashboardOptions> configured) =>
+        ServeAsset(context, configured.Value, Index, "text/html; charset=utf-8");
+
+    private static IResult ServeScript(
+        HttpContext context,
+        [FromServices] IOptions<DiagnosticDashboardOptions> configured) =>
+        ServeAsset(context, configured.Value, Script, "text/javascript; charset=utf-8");
+
+    private static IResult ServeStyles(
+        HttpContext context,
+        [FromServices] IOptions<DiagnosticDashboardOptions> configured) =>
+        ServeAsset(context, configured.Value, Styles, "text/css; charset=utf-8");
+
+    private static IResult ServeConfiguration(
+        HttpContext context,
+        [FromServices] IOptions<DiagnosticDashboardOptions> configured)
+    {
+        DiagnosticDashboardOptions options = configured.Value;
+        if (!options.Enabled)
+        {
+            return Results.NotFound();
+        }
+
+        ApplySecurityHeaders(context.Response);
+        return Results.Json(new
+        {
+            contractVersion = ContractLimits.ContractVersion,
+            pollIntervalSeconds = options.PollIntervalSeconds,
+            maximumRenderedSessions = options.MaximumRenderedSessions,
+            scopes = options.Scopes.Select(static scope => new
+            {
+                gameId = scope.GameId,
+                environmentId = scope.EnvironmentId,
+                protocolVersions = scope.ProtocolVersions,
+                regions = scope.Regions,
+                visibility = "public",
+            }),
+        });
+    }
+
+    private static IResult ServeAsset(
+        HttpContext context,
+        DiagnosticDashboardOptions options,
+        byte[] content,
+        string contentType)
+    {
+        if (!options.Enabled)
+        {
+            return Results.NotFound();
+        }
+
+        ApplySecurityHeaders(context.Response);
+        return Results.Bytes(content, contentType);
+    }
+
+    private static void ApplySecurityHeaders(HttpResponse response)
+    {
+        response.Headers.CacheControl = "no-store";
+        response.Headers["Content-Security-Policy"] = ContentSecurityPolicy;
+        response.Headers["X-Content-Type-Options"] = "nosniff";
+        response.Headers["X-Frame-Options"] = "DENY";
+        response.Headers["Cross-Origin-Opener-Policy"] = "same-origin";
+        response.Headers["Cross-Origin-Resource-Policy"] = "same-origin";
+        response.Headers["Permissions-Policy"] =
+            "camera=(), geolocation=(), microphone=(), payment=(), usb=()";
+        response.Headers["Referrer-Policy"] = "no-referrer";
+    }
+
+    private static byte[] ReadAsset(string fileName)
+    {
+        Assembly assembly = typeof(DiagnosticDashboardEndpoints).Assembly;
+        string resourceName = $"FinalFactory.Rendezvous.Server.Diagnostics.Assets.{fileName}";
+        using Stream source = assembly.GetManifestResourceStream(resourceName)
+            ?? throw new InvalidOperationException($"Missing embedded dashboard asset {fileName}.");
+        using MemoryStream destination = new();
+        source.CopyTo(destination);
+        return destination.ToArray();
+    }
+}

src/FinalFactory.Rendezvous.Server/Diagnostics/DiagnosticDashboardOptions.cs

@@ -0,0 +1,81 @@
+using FinalFactory.Rendezvous.Contracts;
+
+namespace FinalFactory.Rendezvous.Server.Diagnostics;
+
+internal sealed record DiagnosticDashboardOptions
+{
+    public const string SectionName = "Rendezvous:Diagnostics";
+
+    public bool Enabled { get; init; }
+    public int PollIntervalSeconds { get; init; } = 10;
+    public int MaximumRenderedSessions { get; init; } = 100;
+    public DiagnosticDashboardScope[] Scopes { get; init; } = [];
+
+    public IReadOnlyList<string> Validate()
+    {
+        List<string> errors = [];
+        if (PollIntervalSeconds is < 5 or > 60)
+        {
+            errors.Add($"{SectionName}:PollIntervalSeconds must be between 5 and 60.");
+        }
+        if (MaximumRenderedSessions is < 10 or > 500)
+        {
+            errors.Add($"{SectionName}:MaximumRenderedSessions must be between 10 and 500.");
+        }
+        if (!Enabled)
+        {
+            return errors;
+        }
+        if (Scopes is null || Scopes.Length is < 1 or > 32)
+        {
+            errors.Add($"{SectionName}:Scopes must contain between 1 and 32 allow-listed scopes when enabled.");
+            return errors;
+        }
+
+        HashSet<string> identities = new(StringComparer.Ordinal);
+        foreach (DiagnosticDashboardScope? scope in Scopes)
+        {
+            if (scope is null)
+            {
+                errors.Add($"{SectionName}:Scopes cannot contain null entries.");
+                continue;
+            }
+            string gameId = scope.GameId ?? string.Empty;
+            string environmentId = scope.EnvironmentId ?? string.Empty;
+            uint[] protocolVersions = scope.ProtocolVersions ?? [];
+            string[] regions = scope.Regions ?? [];
+            if (!GameId.TryParse(gameId, out _)
+                || !EnvironmentId.TryParse(environmentId, out _))
+            {
+                errors.Add($"{SectionName}:Scopes contains an invalid game or environment identifier.");
+            }
+            if (protocolVersions.Length is < 1 or > 16
+                || protocolVersions.Any(static version => version == 0)
+                || protocolVersions.Distinct().Count() != protocolVersions.Length)
+            {
+                errors.Add($"{SectionName}:Scopes protocol versions must contain 1-16 unique positive values.");
+            }
+            if (regions.Length is < 1 or > 16
+                || regions.Any(static region => !RegionId.TryParse(region ?? string.Empty, out _))
+                || regions.Distinct(StringComparer.Ordinal).Count() != regions.Length)
+            {
+                errors.Add($"{SectionName}:Scopes regions must contain 1-16 unique valid identifiers.");
+            }
+
+            string identity = $"{gameId}\n{environmentId}";
+            if (!identities.Add(identity))
+            {
+                errors.Add($"{SectionName}:Scopes contains a duplicate game/environment pair.");
+            }
+        }
+        return errors;
+    }
+}
+
+internal sealed record DiagnosticDashboardScope
+{
+    public string GameId { get; init; } = string.Empty;
+    public string EnvironmentId { get; init; } = string.Empty;
+    public uint[] ProtocolVersions { get; init; } = [];
+    public string[] Regions { get; init; } = [];
+}

src/FinalFactory.Rendezvous.Server/FinalFactory.Rendezvous.Server.csproj

@@ -47,9 +47,14 @@
     <Compile Include="Browser/EphemeralCursorProtector.cs" />
     <Compile Include="Browser/SessionBrowserCursorCodec.cs" />
     <Compile Include="Browser/SessionBrowserService.cs" />
+    <Compile Include="Browser/SessionChangeJournal.cs" />
+    <Compile Include="Browser/SessionStreamCursorCodec.cs" />
+    <Compile Include="Browser/SessionStreamService.cs" />
     <Compile Include="ConnectionOutcomes/ConnectionOutcomeService.cs" />
     <Compile Include="Deployment/DeploymentOptions.cs" />
     <Compile Include="Deployment/GracefulDrainService.cs" />
+    <Compile Include="Diagnostics/DiagnosticDashboardEndpoints.cs" />
+    <Compile Include="Diagnostics/DiagnosticDashboardOptions.cs" />
     <Compile Include="Http/ContractEndpoints.cs" />
     <Compile Include="Http/RendezvousExceptionHandler.cs" />
     <Compile Include="JoinAttempts/JoinAttemptCursorCodec.cs" />
@@ -57,6 +62,7 @@
     <Compile Include="Observability/AuditOptions.cs" />
     <Compile Include="Observability/AuditTrail.cs" />
     <Compile Include="Observability/HealthEndpoints.cs" />
+    <Compile Include="Observability/PrometheusMetricsEndpoint.cs" />
     <Compile Include="Observability/RendezvousReadiness.cs" />
     <Compile Include="Observability/RendezvousTelemetry.cs" />
     <Compile Include="Observability/TelemetryMiddleware.cs" />
@@ -85,4 +91,15 @@
     <Compile Include="Transport/UdpMediatorOptions.cs" />
     <Compile Include="Transport/UdpMediatorService.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Diagnostics/Assets/app.mjs">
+      <LogicalName>FinalFactory.Rendezvous.Server.Diagnostics.Assets.app.mjs</LogicalName>
+    </EmbeddedResource>
+    <EmbeddedResource Include="Diagnostics/Assets/index.html">
+      <LogicalName>FinalFactory.Rendezvous.Server.Diagnostics.Assets.index.html</LogicalName>
+    </EmbeddedResource>
+    <EmbeddedResource Include="Diagnostics/Assets/styles.css">
+      <LogicalName>FinalFactory.Rendezvous.Server.Diagnostics.Assets.styles.css</LogicalName>
+    </EmbeddedResource>
+  </ItemGroup>
 </Project>

src/FinalFactory.Rendezvous.Server/Http/ContractEndpoints.cs

@@ -1,4 +1,5 @@
 using System.Net;
+using System.Text.Json;
 using FinalFactory.Rendezvous.Contracts;
 using FinalFactory.Rendezvous.Server.Abuse;
 using FinalFactory.Rendezvous.Server.Browser;
@@ -69,6 +70,12 @@ internal static class ContractEndpoints
             .Produces<ApiError>(StatusCodes.Status429TooManyRequests)
             .Produces<ApiError>(StatusCodes.Status503ServiceUnavailable)
             .WithName("BrowseSessions");
+        sessions.MapGet("/stream", StreamSessions)
+            .Produces<SessionStreamEvent>(StatusCodes.Status200OK, contentType: "text/event-stream")
+            .Produces<ApiError>(StatusCodes.Status400BadRequest)
+            .Produces<ApiError>(StatusCodes.Status429TooManyRequests)
+            .Produces<ApiError>(StatusCodes.Status503ServiceUnavailable)
+            .WithName("StreamSessions");
         sessions.MapGet("/{listingId}", GetSession)
             .Produces<GetSessionResponse>()
             .Produces<ApiError>(StatusCodes.Status400BadRequest)
@@ -349,6 +356,123 @@ internal static class ContractEndpoints
         }
     }
 
+    private static async Task<IResult> StreamSessions(
+        [FromQuery] int contractVersion,
+        [FromQuery] string gameId,
+        [FromQuery] string environmentId,
+        [FromQuery] uint protocolVersion,
+        [FromQuery] string? regionId,
+        [FromQuery] bool? excludeFull,
+        [FromQuery] string? streamCursor,
+        [FromHeader(Name = "Last-Event-ID")] string? lastEventId,
+        [FromServices] SessionStreamService streams,
+        [FromServices] AbuseProtectionService abuseProtection,
+        HttpContext httpContext,
+        CancellationToken cancellationToken)
+    {
+        if (!GameId.TryParse(gameId, out GameId parsedGameId)
+            || !EnvironmentId.TryParse(environmentId, out EnvironmentId parsedEnvironmentId)
+            || regionId is not null && !RegionId.TryParse(regionId, out _))
+        {
+            return Error(RendezvousErrorCode.InvalidRequest);
+        }
+        if (!TryAcquireIdentity(
+                abuseProtection,
+                httpContext,
+                "StreamSessions",
+                Tenant(parsedGameId, parsedEnvironmentId),
+                null,
+                null,
+                out AbuseProtectionService.AbuseLease? abuseLease))
+        {
+            return RateLimited(httpContext);
+        }
+
+        using (abuseLease)
+        {
+            BrowserServiceResult<SessionStreamSubscription> subscribed = streams.Subscribe(new()
+            {
+                ContractVersion = contractVersion,
+                GameId = parsedGameId,
+                EnvironmentId = parsedEnvironmentId,
+                ProtocolVersion = protocolVersion,
+                RegionId = regionId is null ? null : new RegionId(regionId),
+                ExcludeFull = excludeFull ?? false,
+            }, string.IsNullOrEmpty(lastEventId) ? streamCursor : lastEventId);
+            if (!subscribed.Succeeded || subscribed.Value is null)
+            {
+                return Error(subscribed.Error);
+            }
+
+            using SessionStreamSubscription subscription = subscribed.Value;
+            using CancellationTokenSource duration = CancellationTokenSource.CreateLinkedTokenSource(
+                cancellationToken);
+            duration.CancelAfter(streams.MaximumConnectionDuration);
+            HttpResponse response = httpContext.Response;
+            response.StatusCode = StatusCodes.Status200OK;
+            response.ContentType = "text/event-stream";
+            response.Headers.CacheControl = "no-cache, no-store";
+            response.Headers["X-Accel-Buffering"] = "no";
+            await response.StartAsync(duration.Token).ConfigureAwait(false);
+            try
+            {
+                while (!duration.IsCancellationRequested)
+                {
+                    SessionStreamReadResult read = streams.Read(subscription);
+                    if (read.RequiresReset)
+                    {
+                        await WriteSseAsync(response, streams.ResetEvent(subscription), duration.Token)
+                            .ConfigureAwait(false);
+                        await response.Body.FlushAsync(duration.Token).ConfigureAwait(false);
+                        break;
+                    }
+                    if (read.Events.Count > 0)
+                    {
+                        foreach (SessionStreamEvent item in read.Events)
+                        {
+                            await WriteSseAsync(response, item, duration.Token).ConfigureAwait(false);
+                        }
+                        await response.Body.FlushAsync(duration.Token).ConfigureAwait(false);
+                        continue;
+                    }
+
+                    bool changed = await streams.WaitForChangeAsync(subscription, duration.Token)
+                        .ConfigureAwait(false);
+                    if (!changed)
+                    {
+                        await WriteSseAsync(
+                            response,
+                            streams.KeepaliveEvent(subscription),
+                            duration.Token).ConfigureAwait(false);
+                        await response.Body.FlushAsync(duration.Token).ConfigureAwait(false);
+                    }
+                }
+            }
+            catch (OperationCanceledException) when (duration.IsCancellationRequested)
+            {
+            }
+            return Results.Empty;
+        }
+    }
+
+    private static async Task WriteSseAsync(
+        HttpResponse response,
+        SessionStreamEvent item,
+        CancellationToken cancellationToken)
+    {
+        string eventName = item.Kind switch
+        {
+            SessionStreamEventKind.SessionUpsert => "session_upsert",
+            SessionStreamEventKind.SessionRemove => "session_remove",
+            SessionStreamEventKind.Reset => "reset",
+            _ => "keepalive",
+        };
+        string data = JsonSerializer.Serialize(item, ContractJson.Options);
+        await response.WriteAsync(
+            $"id: {item.Cursor}\nevent: {eventName}\ndata: {data}\n\n",
+            cancellationToken).ConfigureAwait(false);
+    }
+
     private static IResult GetSession(
         SessionListingId listingId,
         [FromQuery] int contractVersion,

src/FinalFactory.Rendezvous.Server/Observability/PrometheusMetricsEndpoint.cs

@@ -0,0 +1,148 @@
+using System.Security.Cryptography;
+using System.Text;
+using FinalFactory.Rendezvous.Server.Provisioning;
+
+namespace FinalFactory.Rendezvous.Server.Observability;
+
+internal sealed record PrometheusMetricsOptions
+{
+    public const string SectionName = "Rendezvous:Metrics";
+
+    public bool Enabled { get; init; }
+    public string BearerTokenSecretReference { get; init; } = string.Empty;
+
+    public IReadOnlyList<string> Validate()
+    {
+        if (!Enabled)
+        {
+            return [];
+        }
+        string reference = BearerTokenSecretReference ?? string.Empty;
+        bool environmentReference = reference.StartsWith("env:", StringComparison.Ordinal)
+            && reference.Length > "env:".Length;
+        bool absoluteFileReference = reference.StartsWith("file:", StringComparison.Ordinal)
+            && Path.IsPathFullyQualified(reference["file:".Length..]);
+        return reference.Length is < 5 or > 512
+            || !(environmentReference || absoluteFileReference)
+            ? [$"{SectionName}:BearerTokenSecretReference must be a bounded env: or absolute file: secret reference when metrics are enabled."]
+            : [];
+    }
+}
+
+internal sealed class MetricsAccessCredential : IDisposable
+{
+    private byte[]? _token;
+
+    private MetricsAccessCredential(byte[] token) => _token = token;
+
+    public static bool TryCreate(
+        PrometheusMetricsOptions options,
+        ISecretProvider secrets,
+        out MetricsAccessCredential? credential)
+    {
+        credential = null;
+        if (!options.Enabled
+            || !secrets.TryGetSecret(options.BearerTokenSecretReference, out SecretMaterial? material)
+            || material is null)
+        {
+            return false;
+        }
+
+        using (material)
+        {
+            byte[] bytes = material.CopyBytes();
+            int length = bytes.Length;
+            while (length > 0 && bytes[length - 1] is (byte)'\r' or (byte)'\n')
+            {
+                length--;
+            }
+            bool valid = length is >= 32 and <= 128
+                && bytes.AsSpan(0, length).IndexOfAnyExceptInRange((byte)0x21, (byte)0x7e) < 0;
+            if (!valid)
+            {
+                CryptographicOperations.ZeroMemory(bytes);
+                return false;
+            }
+
+            byte[] token = bytes.AsSpan(0, length).ToArray();
+            CryptographicOperations.ZeroMemory(bytes);
+            credential = new(token);
+            return true;
+        }
+    }
+
+    public bool Authorizes(HttpRequest request)
+    {
+        byte[]? expected = _token;
+        string authorization = request.Headers.Authorization.ToString();
+        const string prefix = "Bearer ";
+        if (expected is null
+            || !authorization.StartsWith(prefix, StringComparison.Ordinal)
+            || authorization.Length - prefix.Length is < 32 or > 128)
+        {
+            return false;
+        }
+
+        byte[] supplied = Encoding.UTF8.GetBytes(authorization[prefix.Length..]);
+        try
+        {
+            return supplied.Length == expected.Length
+                && CryptographicOperations.FixedTimeEquals(supplied, expected);
+        }
+        finally
+        {
+            CryptographicOperations.ZeroMemory(supplied);
+        }
+    }
+
+    public void Dispose()
+    {
+        byte[]? token = Interlocked.Exchange(ref _token, null);
+        if (token is not null)
+        {
+            CryptographicOperations.ZeroMemory(token);
+        }
+    }
+
+    public override string ToString() => "[MetricsAccessCredential: REDACTED]";
+}
+
+internal static class PrometheusMetricsEndpoint
+{
+    public static IEndpointRouteBuilder MapPrometheusMetricsEndpoint(
+        this IEndpointRouteBuilder endpoints,
+        PrometheusMetricsOptions options,
+        MetricsAccessCredential? credential)
+    {
+        endpoints.MapGet("/metrics", (HttpContext context, RendezvousTelemetry telemetry) =>
+            Export(context, telemetry, options, credential))
+            .WithName("MetricsScrape")
+            .ExcludeFromDescription();
+        return endpoints;
+    }
+
+    private static IResult Export(
+        HttpContext context,
+        RendezvousTelemetry telemetry,
+        PrometheusMetricsOptions options,
+        MetricsAccessCredential? credential)
+    {
+        if (!options.Enabled)
+        {
+            return Results.NotFound();
+        }
+        if (credential is null || !credential.Authorizes(context.Request))
+        {
+            telemetry.RecordMetricsScrape("rejected");
+            return Results.NotFound();
+        }
+
+        telemetry.RecordMetricsScrape("accepted");
+        context.Response.Headers.CacheControl = "no-store";
+        context.Response.Headers["X-Content-Type-Options"] = "nosniff";
+        return Results.Text(
+            telemetry.RenderPrometheus(),
+            "text/plain; version=0.0.4; charset=utf-8",
+            Encoding.UTF8);
+    }
+}

src/FinalFactory.Rendezvous.Server/Observability/RendezvousTelemetry.cs

@@ -1,5 +1,10 @@
+using System.Collections.Concurrent;
 using System.Diagnostics;
 using System.Diagnostics.Metrics;
+using System.Globalization;
+using System.Text;
+using FinalFactory.Rendezvous.Server.Browser;
+using FinalFactory.Rendezvous.Server.Provisioning;
 using FinalFactory.Rendezvous.Server.State;
 
 namespace FinalFactory.Rendezvous.Server.Observability;
@@ -10,6 +15,10 @@ internal sealed class RendezvousTelemetry : IDisposable
     public const string ActivitySourceName = "FinalFactory.Rendezvous.Server";
 
     private readonly InMemoryEphemeralRendezvousStore _store;
+    private readonly SessionChangeJournal? _sessionChanges;
+    private readonly ProvisioningRuntime? _provisioning;
+    private readonly ConcurrentDictionary<MetricSeriesKey, long> _prometheusCounters = new();
+    private readonly ConcurrentDictionary<MetricSeriesKey, PrometheusHistogram> _prometheusHistograms = new();
     private readonly Meter _meter = new(MeterName, "1.0.0");
     private readonly ActivitySource _activities = new(ActivitySourceName, "1.0.0");
     private readonly Counter<long> _httpRequests;
@@ -22,9 +31,14 @@ internal sealed class RendezvousTelemetry : IDisposable
     private readonly Counter<long> _operatorAuthentication;
     private readonly Histogram<double> _pairingLatency;
 
-    public RendezvousTelemetry(InMemoryEphemeralRendezvousStore store)
+    public RendezvousTelemetry(
+        InMemoryEphemeralRendezvousStore store,
+        SessionChangeJournal? sessionChanges = null,
+        ProvisioningRuntime? provisioning = null)
     {
         _store = store;
+        _sessionChanges = sessionChanges;
+        _provisioning = provisioning;
         _httpRequests = _meter.CreateCounter<long>("rendezvous.http.requests");
         _httpDuration = _meter.CreateHistogram<double>(
             "rendezvous.http.duration",
@@ -75,9 +89,21 @@ internal sealed class RendezvousTelemetry : IDisposable
         };
         _httpRequests.Add(1, tags);
         _httpDuration.Record(elapsedMilliseconds, tags);
+        IncrementPrometheus(
+            "rendezvous_http_requests_total",
+            Labels(("operation", operation), ("status_code", statusCode.ToString(CultureInfo.InvariantCulture))));
+        ObservePrometheus(
+            "rendezvous_http_duration_milliseconds",
+            elapsedMilliseconds,
+            Labels(("operation", operation), ("status_code", statusCode.ToString(CultureInfo.InvariantCulture))));
     }
 
-    public void RecordUdp(string operation, string result, double elapsedMilliseconds)
+    public void RecordUdp(
+        string operation,
+        string result,
+        double elapsedMilliseconds,
+        int receivedBytes = 0,
+        int responseBudgetBytes = 0)
     {
         TagList tags = new()
         {
@@ -86,41 +112,315 @@ internal sealed class RendezvousTelemetry : IDisposable
         };
         _udpResults.Add(1, tags);
         _udpDuration.Record(elapsedMilliseconds, tags);
+        IncrementPrometheus(
+            "rendezvous_udp_results_total",
+            Labels(("operation", operation), ("result", result)));
+        ObservePrometheus(
+            "rendezvous_udp_duration_milliseconds",
+            elapsedMilliseconds,
+            Labels(("operation", operation), ("result", result)));
+        AddPrometheus(
+            "rendezvous_udp_received_bytes_total",
+            Math.Max(0, receivedBytes),
+            Labels(("operation", operation)));
+        AddPrometheus(
+            "rendezvous_udp_response_budget_bytes_total",
+            Math.Max(0, responseBudgetBytes),
+            Labels(("operation", operation)));
     }
 
-    public void RecordLimiterDrop(string transport, string partition) =>
+    public void RecordLimiterDrop(string transport, string partition)
+    {
         _limiterDrops.Add(1, new TagList
         {
             { "transport", transport },
             { "partition", partition },
         });
+        IncrementPrometheus(
+            "rendezvous_limiter_drops_total",
+            Labels(("transport", transport), ("partition", partition)));
+    }
 
-    public void RecordAudit(string action, string result) =>
+    public void RecordAudit(string action, string result)
+    {
         _auditEvents.Add(1, new TagList
         {
             { "action", action },
             { "result", result },
         });
+        IncrementPrometheus(
+            "rendezvous_audit_events_total",
+            Labels(("action", action), ("result", result)));
+    }
 
-    public void RecordConnectionOutcome(string outcome, string elapsedBucket) =>
+    public void RecordConnectionOutcome(string outcome, string elapsedBucket)
+    {
         _connectionOutcomes.Add(1, new TagList
         {
             { "outcome", outcome },
             { "elapsed_bucket", elapsedBucket },
         });
+        IncrementPrometheus(
+            "rendezvous_connection_outcomes_total",
+            Labels(("outcome", outcome), ("elapsed_bucket", elapsedBucket)));
+    }
 
-    public void RecordOperatorAuthentication(string result) =>
+    public void RecordOperatorAuthentication(string result)
+    {
         _operatorAuthentication.Add(1, new TagList
         {
             { "result", result },
         });
+        IncrementPrometheus(
+            "rendezvous_operator_authentication_total",
+            Labels(("result", result)));
+    }
 
-    public void RecordPairingLatency(double elapsedMilliseconds) =>
+    public void RecordPairingLatency(double elapsedMilliseconds)
+    {
         _pairingLatency.Record(elapsedMilliseconds);
+        ObservePrometheus("rendezvous_pairing_latency_milliseconds", elapsedMilliseconds, string.Empty);
+    }
+
+    public void RecordMetricsScrape(string result) => IncrementPrometheus(
+        "rendezvous_metrics_scrapes_total",
+        Labels(("result", result)));
+
+    public string RenderPrometheus()
+    {
+        StringBuilder output = new(16 * 1024);
+        foreach (IGrouping<string, KeyValuePair<MetricSeriesKey, long>> family in _prometheusCounters
+                     .OrderBy(static item => item.Key.Name, StringComparer.Ordinal)
+                     .ThenBy(static item => item.Key.Labels, StringComparer.Ordinal)
+                     .GroupBy(static item => item.Key.Name, StringComparer.Ordinal))
+        {
+            output.Append("# TYPE ").Append(family.Key).Append(" counter\n");
+            foreach (KeyValuePair<MetricSeriesKey, long> series in family)
+            {
+                AppendValue(output, series.Key.Name, series.Key.Labels, series.Value);
+            }
+        }
+        foreach (IGrouping<string, KeyValuePair<MetricSeriesKey, PrometheusHistogram>> family in
+                 _prometheusHistograms
+                     .OrderBy(static item => item.Key.Name, StringComparer.Ordinal)
+                     .ThenBy(static item => item.Key.Labels, StringComparer.Ordinal)
+                     .GroupBy(static item => item.Key.Name, StringComparer.Ordinal))
+        {
+            output.Append("# TYPE ").Append(family.Key).Append(" histogram\n");
+            foreach (KeyValuePair<MetricSeriesKey, PrometheusHistogram> series in family)
+            {
+                series.Value.Append(output, series.Key.Name, series.Key.Labels);
+            }
+        }
+
+        EphemeralStoreSnapshot store = _store.GetMetricsSnapshot();
+        AppendGauge(output, "rendezvous_store_active_listings", store.ActiveListings);
+        AppendGauge(output, "rendezvous_store_fresh_presence_bindings", store.FreshPresenceBindings);
+        AppendGauge(
+            output,
+            "rendezvous_store_awaiting_presence_listings",
+            Math.Max(0, store.ActiveListings - store.FreshPresenceBindings));
+        AppendGauge(output, "rendezvous_store_active_leases", store.ActiveListings);
+        AppendGauge(output, "rendezvous_store_active_attempts", store.ActiveJoinAttempts);
+        AppendGauge(output, "rendezvous_queue_depth", store.ActiveJoinAttempts);
+        AppendGauge(output, "rendezvous_store_replay_markers", store.ReplayMarkers);
+        AppendGauge(output, "rendezvous_store_available", store.IsAvailable ? 1 : 0);
+        AppendGauge(output, "rendezvous_store_draining", store.IsDraining ? 1 : 0);
+        AppendCounter(output, "rendezvous_store_expiry_churn_total", store.ExpiryChurn);
+        if (_sessionChanges is not null)
+        {
+            AppendGauge(output, "rendezvous_browser_sse_subscribers", _sessionChanges.SubscriberCount);
+            AppendGauge(output, "rendezvous_browser_sse_tenants", _sessionChanges.SubscribedTenantCount);
+            AppendGauge(output, "rendezvous_browser_replay_entries", _sessionChanges.ReplayCount);
+        }
+        AppendProcessMetrics(output);
+        AppendSigningKeyMetrics(output);
+        return output.ToString();
+    }
+
+    private void AppendSigningKeyMetrics(StringBuilder output)
+    {
+        if (_provisioning is null)
+        {
+            return;
+        }
+        DateTimeOffset now = DateTimeOffset.UtcNow;
+        SigningKeyStatus[] statuses = _provisioning.SigningKeys.GetStatuses(now).ToArray();
+        output.Append("# TYPE rendezvous_signing_keys gauge\n");
+        foreach (IGrouping<string, SigningKeyStatus> state in statuses.GroupBy(
+                     static status => status.Status,
+                     StringComparer.Ordinal))
+        {
+            AppendValue(
+                output,
+                "rendezvous_signing_keys",
+                Labels(("state", state.Key)),
+                state.Count());
+        }
+        double seconds = statuses
+            .Where(static status => status.Status == "signing")
+            .Select(status => Math.Max(0, (status.SignUntil - now).TotalSeconds))
+            .DefaultIfEmpty(0)
+            .Min();
+        AppendGauge(output, "rendezvous_signing_key_sign_seconds_remaining", seconds);
+    }
+
+    private static void AppendProcessMetrics(StringBuilder output)
+    {
+        using Process process = Process.GetCurrentProcess();
+        process.Refresh();
+        AppendCounter(output, "process_cpu_seconds_total", process.TotalProcessorTime.TotalSeconds);
+        AppendGauge(output, "process_resident_memory_bytes", process.WorkingSet64);
+        AppendGauge(output, "process_virtual_memory_bytes", process.VirtualMemorySize64);
+        AppendGauge(output, "process_threads", process.Threads.Count);
+        try
+        {
+            AppendGauge(
+                output,
+                "process_open_file_descriptors",
+                Directory.EnumerateFileSystemEntries("/proc/self/fd").Count());
+        }
+        catch (Exception exception) when (exception is IOException
+                                           or UnauthorizedAccessException)
+        {
+        }
+        AppendGauge(output, "dotnet_gc_heap_size_bytes", GC.GetTotalMemory(forceFullCollection: false));
+        output.Append("# TYPE dotnet_gc_collections_total counter\n");
+        AppendValue(output, "dotnet_gc_collections_total", Labels(("generation", "0")), GC.CollectionCount(0));
+        AppendValue(output, "dotnet_gc_collections_total", Labels(("generation", "1")), GC.CollectionCount(1));
+        AppendValue(output, "dotnet_gc_collections_total", Labels(("generation", "2")), GC.CollectionCount(2));
+        AppendGauge(output, "dotnet_thread_pool_threads", ThreadPool.ThreadCount);
+        ThreadPool.GetAvailableThreads(out int workerThreads, out int completionThreads);
+        AppendGauge(output, "dotnet_thread_pool_available_worker_threads", workerThreads);
+        AppendGauge(output, "dotnet_thread_pool_available_completion_threads", completionThreads);
+    }
+
+    private void IncrementPrometheus(string name, string labels) =>
+        _prometheusCounters.AddOrUpdate(new(name, labels), 1, static (_, current) => current + 1);
+
+    private void AddPrometheus(string name, long value, string labels)
+    {
+        if (value <= 0)
+        {
+            return;
+        }
+        _prometheusCounters.AddOrUpdate(new(name, labels), value, (_, current) => current + value);
+    }
+
+    private void ObservePrometheus(string name, double value, string labels) =>
+        _prometheusHistograms.GetOrAdd(new(name, labels), static _ => new()).Observe(value);
+
+    private static string Labels(params (string Name, string Value)[] labels)
+    {
+        if (labels.Length == 0)
+        {
+            return string.Empty;
+        }
+        return "{" + string.Join(',', labels.Select(static label =>
+            $"{label.Name}=\"{EscapeLabel(NormalizeLabel(label.Value))}\"")) + "}";
+    }
+
+    private static string NormalizeLabel(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value) || value.Length > 64)
+        {
+            return "other";
+        }
+        return value.All(static character => char.IsAsciiLetterOrDigit(character)
+            || character is '-' or '_' or '.')
+            ? value
+            : "other";
+    }
+
+    private static string EscapeLabel(string value) => value
+        .Replace("\\", "\\\\", StringComparison.Ordinal)
+        .Replace("\"", "\\\"", StringComparison.Ordinal)
+        .Replace("\n", "\\n", StringComparison.Ordinal);
+
+    private static void AppendCounter(
+        StringBuilder output,
+        string name,
+        double value,
+        string labels = "")
+    {
+        output.Append("# TYPE ").Append(name).Append(" counter\n");
+        AppendValue(output, name, labels, value);
+    }
+
+    private static void AppendGauge(
+        StringBuilder output,
+        string name,
+        double value,
+        string labels = "")
+    {
+        output.Append("# TYPE ").Append(name).Append(" gauge\n");
+        AppendValue(output, name, labels, value);
+    }
+
+    private static void AppendValue(StringBuilder output, string name, string labels, double value) =>
+        output.Append(name)
+            .Append(labels)
+            .Append(' ')
+            .Append(value.ToString("R", CultureInfo.InvariantCulture))
+            .Append('\n');
 
     public void Dispose()
     {
         _activities.Dispose();
         _meter.Dispose();
     }
+
+    private readonly record struct MetricSeriesKey(string Name, string Labels);
+
+    private sealed class PrometheusHistogram
+    {
+        private static readonly double[] Bounds = [1, 5, 10, 25, 50, 100, 250, 500, 1000, 5000];
+        private readonly object _gate = new();
+        private readonly long[] _buckets = new long[Bounds.Length];
+        private long _count;
+        private double _sum;
+
+        public void Observe(double value)
+        {
+            if (!double.IsFinite(value) || value < 0)
+            {
+                return;
+            }
+            lock (_gate)
+            {
+                _count++;
+                _sum += value;
+                for (int index = 0; index < Bounds.Length; index++)
+                {
+                    if (value <= Bounds[index])
+                    {
+                        _buckets[index]++;
+                    }
+                }
+            }
+        }
+
+        public void Append(StringBuilder output, string name, string labels)
+        {
+            lock (_gate)
+            {
+                for (int index = 0; index < Bounds.Length; index++)
+                {
+                    AppendValue(
+                        output,
+                        name + "_bucket",
+                        AddLabel(labels, "le", Bounds[index].ToString("R", CultureInfo.InvariantCulture)),
+                        _buckets[index]);
+                }
+                AppendValue(output, name + "_bucket", AddLabel(labels, "le", "+Inf"), _count);
+                AppendValue(output, name + "_sum", labels, _sum);
+                AppendValue(output, name + "_count", labels, _count);
+            }
+        }
+
+        private static string AddLabel(string labels, string name, string value) =>
+            string.IsNullOrEmpty(labels)
+                ? $"{{{name}=\"{value}\"}}"
+                : labels[..^1] + $",{name}=\"{value}\"}}";
+    }
 }

src/FinalFactory.Rendezvous.Server/Program.cs

@@ -4,6 +4,7 @@ using FinalFactory.Rendezvous.Server.Abuse;
 using FinalFactory.Rendezvous.Server.Browser;
 using FinalFactory.Rendezvous.Server.ConnectionOutcomes;
 using FinalFactory.Rendezvous.Server.Deployment;
+using FinalFactory.Rendezvous.Server.Diagnostics;
 using FinalFactory.Rendezvous.Server.Http;
 using FinalFactory.Rendezvous.Server.JoinAttempts;
 using FinalFactory.Rendezvous.Server.Observability;
@@ -251,10 +252,42 @@ if (!builder.Environment.IsDevelopment() && !isOpenApiGeneration)
 }
 
 builder.Services.AddSingleton(Microsoft.Extensions.Options.Options.Create(deploymentOptions));
+DiagnosticDashboardOptions diagnosticDashboardOptions = builder.Configuration
+    .GetSection(DiagnosticDashboardOptions.SectionName)
+    .Get<DiagnosticDashboardOptions>() ?? new DiagnosticDashboardOptions();
+IReadOnlyList<string> diagnosticErrors = diagnosticDashboardOptions.Validate();
+if (diagnosticErrors.Count > 0)
+{
+    throw new DeploymentConfigurationException(diagnosticErrors);
+}
+builder.Services.AddSingleton(
+    Microsoft.Extensions.Options.Options.Create(diagnosticDashboardOptions));
+PrometheusMetricsOptions metricsOptions = builder.Configuration
+    .GetSection(PrometheusMetricsOptions.SectionName)
+    .Get<PrometheusMetricsOptions>() ?? new PrometheusMetricsOptions();
+IReadOnlyList<string> metricsErrors = metricsOptions.Validate();
+if (metricsErrors.Count > 0)
+{
+    throw new DeploymentConfigurationException(metricsErrors);
+}
+builder.Services.AddSingleton(Microsoft.Extensions.Options.Options.Create(metricsOptions));
+MetricsAccessCredential? metricsCredential = null;
+if (metricsOptions.Enabled && !isOpenApiGeneration)
+{
+    EnvironmentSecretProvider metricsSecrets = new();
+    if (!MetricsAccessCredential.TryCreate(metricsOptions, metricsSecrets, out metricsCredential)
+        || metricsCredential is null)
+    {
+        throw new DeploymentConfigurationException(
+            [$"{PrometheusMetricsOptions.SectionName}:BearerTokenSecretReference did not resolve to 32-128 visible ASCII bytes."]);
+    }
+    builder.Services.AddSingleton(metricsCredential);
+}
 builder.Services.Configure<HostOptions>(options =>
     options.ShutdownTimeout = TimeSpan.FromSeconds(deploymentOptions.DrainDeadlineSeconds + 10));
 
 SystemRendezvousClock rendezvousClock = new();
+SessionChangeJournal sessionChanges = new(new SessionChangeJournalOptions());
 EphemeralStoreOptions stateOptions = new()
 {
     GracefulDrainLifetime = TimeSpan.FromSeconds(deploymentOptions.DrainDeadlineSeconds),
@@ -262,8 +295,10 @@ EphemeralStoreOptions stateOptions = new()
 InMemoryEphemeralRendezvousStore stateStore = new(
     stateOptions,
     rendezvousClock,
-    rendezvousClock);
+    rendezvousClock,
+    sessionChanges);
 builder.Services.AddSingleton(stateStore);
+builder.Services.AddSingleton(sessionChanges);
 builder.Services.AddSingleton<IEphemeralRendezvousStore>(stateStore);
 builder.Services.AddSingleton<IWallClock>(rendezvousClock);
 builder.Services.AddSingleton<IMonotonicClock>(rendezvousClock);
@@ -297,7 +332,9 @@ else
     builder.Services.AddSingleton(SessionLeaseTiming.From(stateOptions));
     builder.Services.AddSingleton<SessionLeaseService>();
     builder.Services.AddSingleton<SessionBrowserCursorCodec>();
+    builder.Services.AddSingleton<SessionStreamCursorCodec>();
     builder.Services.AddSingleton<SessionBrowserService>();
+    builder.Services.AddSingleton<SessionStreamService>();
     builder.Services.AddSingleton<JoinAttemptCursorCodec>();
     builder.Services.AddSingleton<JoinAttemptService>();
     builder.Services.AddSingleton<ConnectionOutcomeMetrics>();
@@ -344,6 +381,8 @@ app.MapOpenApi();
 app.MapRendezvousContractEndpoints();
 app.MapOperatorEndpoints();
 app.MapRendezvousHealthEndpoints();
+app.MapDiagnosticDashboardEndpoints();
+app.MapPrometheusMetricsEndpoint(metricsOptions, metricsCredential);
 
 await app.RunAsync();
 

src/FinalFactory.Rendezvous.Server/Sessions/SessionLeaseService.cs

@@ -240,7 +240,15 @@ internal sealed class SessionLeaseService(
         }
 
         StoredListing ownedListing = listing!;
-        PublisherAuthorizationResult authorized = AuthorizeExisting(principal, ownedListing, request.Metadata);
+        PublisherAuthorizationResult authorized = authorization.Authorize(
+            principal,
+            ownedListing.Definition.Scope.GameId,
+            ownedListing.Definition.Scope.EnvironmentId,
+            request.RegionId ?? ownedListing.Definition.RegionId,
+            request.ProtocolVersion ?? ownedListing.Definition.ProtocolVersion,
+            request.Visibility ?? ownedListing.Definition.Visibility,
+            request.Metadata,
+            clock.UtcNow);
         if (!authorized.IsAllowed || authorized.Context is null)
         {
             return new(MapAuthorization(authorized.Error));
@@ -261,7 +269,10 @@ internal sealed class SessionLeaseService(
             request.Capacity.CurrentPlayers,
             request.Capacity.MaximumPlayers,
             request.Metadata,
-            request.DedicatedFallback), cancellationToken);
+            request.DedicatedFallback,
+            request.RegionId,
+            request.ProtocolVersion,
+            request.Visibility), cancellationToken);
         return updated.Succeeded
             ? new(RendezvousErrorCode.None, true)
             : new(updated.Code.ToContractError());
@@ -391,6 +402,9 @@ internal sealed class SessionLeaseService(
             || !ContractValidation.IsDisplayNameValid(request.DisplayName)
             || !ContractValidation.IsCapacityValid(request.Capacity)
             || !ContractValidation.IsMetadataValid(request.Metadata)
+            || request.RegionId.HasValue && string.IsNullOrEmpty(request.RegionId.Value.Value)
+            || request.ProtocolVersion.HasValue && request.ProtocolVersion.Value == 0
+            || request.Visibility.HasValue && !Enum.IsDefined(request.Visibility.Value)
             || request.DedicatedFallback is not null
                 && !ContractValidation.IsNetworkEndpointValid(request.DedicatedFallback)
             ? RendezvousErrorCode.InvalidRequest

src/FinalFactory.Rendezvous.Server/State/EphemeralStateContracts.cs

@@ -228,7 +228,10 @@ internal sealed record UpdateListingCommand(
     int CurrentPlayers,
     int MaximumPlayers,
     IReadOnlyDictionary<string, string> Metadata,
-    NetworkEndpoint? DedicatedFallback);
+    NetworkEndpoint? DedicatedFallback,
+    RegionId? RegionId = null,
+    uint? ProtocolVersion = null,
+    ListingVisibility? Visibility = null);
 
 internal sealed record DeleteListingCommand(
     SessionListingId ListingId,

src/FinalFactory.Rendezvous.Server/State/InMemoryEphemeralRendezvousStore.cs

@@ -1,4 +1,5 @@
 using FinalFactory.Rendezvous.Contracts;
+using FinalFactory.Rendezvous.Server.Browser;
 
 namespace FinalFactory.Rendezvous.Server.State;
 
@@ -8,6 +9,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
     private readonly object _gate = new();
     private readonly EphemeralStoreOptions _options;
     private readonly IMonotonicClock _monotonicClock;
+    private readonly SessionChangeJournal? _sessionChanges;
     private readonly DateTimeOffset _wallOrigin;
     private readonly TimeSpan _monotonicOrigin;
     private readonly Dictionary<SessionListingId, ListingEntry> _listings = [];
@@ -45,7 +47,8 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
     public InMemoryEphemeralRendezvousStore(
         EphemeralStoreOptions options,
         IWallClock wallClock,
-        IMonotonicClock monotonicClock)
+        IMonotonicClock monotonicClock,
+        SessionChangeJournal? sessionChanges = null)
     {
         ArgumentNullException.ThrowIfNull(options);
         ArgumentNullException.ThrowIfNull(wallClock);
@@ -53,6 +56,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
         options.Validate();
         _options = options;
         _monotonicClock = monotonicClock;
+        _sessionChanges = sessionChanges;
         _wallOrigin = wallClock.UtcNow;
         _monotonicOrigin = monotonicClock.Elapsed;
         InstanceId = Guid.NewGuid();
@@ -225,7 +229,9 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             now + _options.IdempotencyLifetime);
         _idempotency.Add(idempotencyKey, idempotency);
         EnqueueDeadline(_idempotencyExpiries, idempotencyKey, idempotency.Deadline);
-        return new(StoreResultCode.Success, Snapshot(entry));
+        StoredListing created = Snapshot(entry);
+        _sessionChanges?.Publish(null, created);
+        return new(StoreResultCode.Success, created);
     }, cancellationToken);
 
     public StoreResult<StoredListing> RenewLease(
@@ -277,6 +283,9 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             || command.MaximumPlayers is <= 0 or > ContractLimits.SessionCapacityMaxPlayers
             || command.CurrentPlayers < 0
             || command.CurrentPlayers > command.MaximumPlayers
+            || command.RegionId.HasValue && string.IsNullOrEmpty(command.RegionId.Value.Value)
+            || command.ProtocolVersion.HasValue && command.ProtocolVersion.Value == 0
+            || command.Visibility.HasValue && !Enum.IsDefined(command.Visibility.Value)
             || !ContractValidation.IsMetadataValid(command.Metadata)
             || command.DedicatedFallback is not null
                 && !ContractValidation.IsNetworkEndpointValid(command.DedicatedFallback))
@@ -302,8 +311,12 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             return new(StoreResultCode.NotFound);
         }
 
+        StoredListing before = Snapshot(entry);
         entry.Definition = StoredListing.Freeze(entry.Definition with
         {
+            RegionId = command.RegionId ?? entry.Definition.RegionId,
+            ProtocolVersion = command.ProtocolVersion ?? entry.Definition.ProtocolVersion,
+            Visibility = command.Visibility ?? entry.Definition.Visibility,
             BuildVersion = command.BuildVersion,
             DisplayName = command.DisplayName,
             CurrentPlayers = command.CurrentPlayers,
@@ -312,7 +325,9 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             DedicatedFallback = command.DedicatedFallback,
         });
         entry.Version++;
-        return new(StoreResultCode.Success, Snapshot(entry));
+        StoredListing after = Snapshot(entry);
+        _sessionChanges?.Publish(before, after);
+        return new(StoreResultCode.Success, after);
     }, cancellationToken);
 
     public StoreResult<bool> DeleteListing(
@@ -382,6 +397,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             return new(StoreResultCode.CapacityExceeded);
         }
 
+        StoredListing before = Snapshot(entry);
         bool isNewPresence = !_presence.ContainsKey(command.Handle);
         PresenceEntry presence = new(
             command.PublicEndpoint,
@@ -396,7 +412,9 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
                 command.Handle,
                 presence.Deadline);
         }
-        return new(StoreResultCode.Success, Snapshot(entry));
+        StoredListing after = Snapshot(entry);
+        _sessionChanges?.Publish(before, after);
+        return new(StoreResultCode.Success, after);
     }, cancellationToken, eagerCleanup: false);
 
     public StoreResult<IReadOnlyList<StoredListing>> BrowseVisibleListings(
@@ -996,6 +1014,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
 
     private void ClearActiveState()
     {
+        StoredListing[] removedListings = _listings.Values.Select(Snapshot).ToArray();
         _listings.Clear();
         _listingCountsByOwner.Clear();
         _listingExpiries.Clear();
@@ -1017,6 +1036,10 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
         _idempotencyExpiries.Clear();
         _replay.Clear();
         _replayExpiries.Clear();
+        foreach (StoredListing listing in removedListings)
+        {
+            _sessionChanges?.Publish(listing, null);
+        }
     }
 
     private void RemoveListing(SessionListingId listingId)
@@ -1026,6 +1049,7 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             return;
         }
 
+        StoredListing removed = Snapshot(listing);
         _leases.Remove(listing.Definition.LeaseId);
         DecrementCount(_listingCountsByOwner, listing.Definition.OwnerSubject);
         _presenceHandles.Remove(listing.Definition.HostPresenceHandle);
@@ -1045,6 +1069,8 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
                 RemoveOutcome(attemptId);
             }
         }
+
+        _sessionChanges?.Publish(removed, null);
     }
 
     private void RemoveAttempt(JoinAttemptId attemptId)
@@ -1186,6 +1212,12 @@ internal sealed class InMemoryEphemeralRendezvousStore : IEphemeralRendezvousSto
             }
             else if (_presence.Remove(candidate.Key))
             {
+                if (_presenceHandles.TryGetValue(candidate.Key, out SessionListingId listingId)
+                    && _listings.TryGetValue(listingId, out ListingEntry? listing))
+                {
+                    StoredListing after = Snapshot(listing);
+                    _sessionChanges?.Publish(after with { HasFreshPresence = true }, after);
+                }
                 removed++;
             }
         }

src/FinalFactory.Rendezvous.Server/Transport/NatMediationProcessor.cs

@@ -82,7 +82,9 @@ internal sealed class NatMediationProcessor(
         telemetry?.RecordUdp(
             "frozen",
             result.ToString(),
-            Stopwatch.GetElapsedTime(started).TotalMilliseconds);
+            Stopwatch.GetElapsedTime(started).TotalMilliseconds,
+            encoded.Length,
+            result == NatMediationResult.Introduced ? 2 * ContractLimits.UdpDatagramMaxBytes : 0);
         return result;
     }
 
@@ -157,7 +159,7 @@ internal sealed class NatMediationProcessor(
             observedPublicEndpoint,
             token,
             introductionSink,
-            cancellationToken);
+            cancellationToken: cancellationToken);
     }
 
     internal NatMediationResult ProcessRequestAfterIngress(
@@ -165,6 +167,7 @@ internal sealed class NatMediationProcessor(
         IPEndPoint observedPublicEndpoint,
         string token,
         INatIntroductionSink introductionSink,
+        int receivedBytes = 0,
         CancellationToken cancellationToken = default)
     {
         long started = Stopwatch.GetTimestamp();
@@ -178,7 +181,9 @@ internal sealed class NatMediationProcessor(
         telemetry?.RecordUdp(
             "litenet",
             result.ToString(),
-            Stopwatch.GetElapsedTime(started).TotalMilliseconds);
+            Stopwatch.GetElapsedTime(started).TotalMilliseconds,
+            receivedBytes,
+            result == NatMediationResult.Introduced ? 2 * ContractLimits.UdpDatagramMaxBytes : 0);
         return result;
     }
 

src/FinalFactory.Rendezvous.Server/Transport/UdpMediatorService.cs

@@ -201,7 +201,7 @@ internal sealed class UdpMediatorService : BackgroundService
                      && token is not null)
             {
                 _ = processor.ProcessRequestAfterIngress(
-                    claimedLocalEndpoint, endPoint, token, sink);
+                    claimedLocalEndpoint, endPoint, token, sink, length);
             }
 
             // Every inbound packet is consumed here. NatPunchModule is used only for outbound introductions.

src/FinalFactory.Rendezvous.TestClient/RendezvousCommandRunner.cs

@@ -21,6 +21,7 @@ internal sealed class RendezvousCommandRunner : ITestClientCommandRunner
         {
             TestClientMode.Host => RunHostAsync(options, output, cancellationToken),
             TestClientMode.Browse => RunBrowseAsync(options, output, cancellationToken),
+            TestClientMode.Watch => RunWatchAsync(options, output, cancellationToken),
             TestClientMode.Join => RunJoinAsync(options, output, input, cancellationToken),
             _ => Task.FromResult(TestClientExitCode.Usage),
         };
@@ -553,6 +554,178 @@ internal sealed class RendezvousCommandRunner : ITestClientCommandRunner
         }
     }
 
+    private static async Task<TestClientExitCode> RunWatchAsync(
+        TestClientOptions options,
+        TestClientOutput output,
+        CancellationToken cancellationToken)
+    {
+        using CancellationTokenSource watch = CancellationTokenSource.CreateLinkedTokenSource(
+            cancellationToken);
+        watch.CancelAfter(options.RunDuration ?? options.OperationTimeout);
+        using HttpClient http = CreateHttpClient(options);
+        RendezvousSessionBrowserClient browser = new(http, ClientOptions(options));
+        BrowseSessionsRequest request = BrowseRequest(options);
+        RendezvousClientResult<BrowseSessionsResponse> snapshot = await browser.BrowseAsync(
+            request,
+            watch.Token).ConfigureAwait(false);
+        if (!snapshot.IsSuccess || snapshot.Value is null)
+        {
+            WriteServiceFailure(output, "watch.snapshot", "directory", snapshot);
+            return TestClientExitCode.ServiceFailure;
+        }
+        output.Write(
+            "watch.snapshot",
+            "complete",
+            phase: "directory",
+            count: snapshot.Value.Items.Count);
+        string cursor = options.ExerciseReset
+            ? CorruptCursor(snapshot.Value.StreamCursor)
+            : snapshot.Value.StreamCursor;
+        output.Write("watch.stream", "started", phase: "live-directory");
+        SessionStreamEvent? expectedReplay = null;
+        bool reconnectExerciseCompleted = false;
+        int emptyConnections = 0;
+        try
+        {
+            while (true)
+            {
+                string connectionCursor = cursor;
+                bool receivedEvent = false;
+                bool deliberateReconnect = false;
+                await foreach (RendezvousClientResult<SessionStreamEvent> result in browser
+                                   .StreamAsync(request, cursor, watch.Token)
+                                   .ConfigureAwait(false))
+                {
+                    if (!result.IsSuccess || result.Value is null)
+                    {
+                        WriteServiceFailure(output, "watch.stream", "live-directory", result);
+                        return TestClientExitCode.ServiceFailure;
+                    }
+                    receivedEvent = true;
+                    SessionStreamEvent item = result.Value;
+                    if (expectedReplay is not null)
+                    {
+                        if (!SameStreamEvent(expectedReplay, item))
+                        {
+                            output.WriteError(
+                                "watch.reconnect",
+                                "failed",
+                                "The reconnect did not replay the expected ordered event.",
+                                phase: "live-directory");
+                            return TestClientExitCode.ServiceFailure;
+                        }
+                        output.Write("watch.reconnect", "verified", phase: "live-directory");
+                        expectedReplay = null;
+                        reconnectExerciseCompleted = true;
+                        cursor = item.Cursor;
+                        if (options.Script)
+                        {
+                            return TestClientExitCode.Success;
+                        }
+                    }
+                    else
+                    {
+                        cursor = item.Cursor;
+                    }
+
+                    switch (item.Kind)
+                    {
+                        case SessionStreamEventKind.SessionUpsert when item.Session is not null:
+                            output.Write(
+                                "watch.session-upsert",
+                                "available",
+                                phase: "live-directory",
+                                listingId: item.Session.ListingId.ToString(),
+                                displayName: item.Session.DisplayName);
+                            break;
+                        case SessionStreamEventKind.SessionRemove when item.ListingId.HasValue:
+                            output.Write(
+                                "watch.session-remove",
+                                "removed",
+                                phase: "live-directory",
+                                listingId: item.ListingId.Value.ToString());
+                            break;
+                        case SessionStreamEventKind.Reset:
+                            output.Write("watch.reset", "required", phase: "live-directory");
+                            RendezvousClientResult<BrowseSessionsResponse> refreshed = await browser.BrowseAsync(
+                                request,
+                                watch.Token).ConfigureAwait(false);
+                            if (!refreshed.IsSuccess || refreshed.Value is null)
+                            {
+                                WriteServiceFailure(output, "watch.snapshot", "directory", refreshed);
+                                return TestClientExitCode.ServiceFailure;
+                            }
+                            output.Write(
+                                "watch.snapshot",
+                                "refreshed",
+                                phase: "directory",
+                                count: refreshed.Value.Items.Count);
+                            return TestClientExitCode.Success;
+                        case SessionStreamEventKind.Keepalive:
+                            output.Write("watch.keepalive", "alive", phase: "live-directory");
+                            break;
+                    }
+
+                    bool listingDelta = item.Kind is SessionStreamEventKind.SessionUpsert
+                        or SessionStreamEventKind.SessionRemove;
+                    if (options.ExerciseReconnect
+                        && !reconnectExerciseCompleted
+                        && listingDelta
+                        && expectedReplay is null)
+                    {
+                        expectedReplay = item;
+                        cursor = connectionCursor;
+                        deliberateReconnect = true;
+                        output.Write("watch.reconnect", "started", phase: "live-directory");
+                        break;
+                    }
+                    if (options.Script && listingDelta)
+                    {
+                        return TestClientExitCode.Success;
+                    }
+                }
+
+                if (deliberateReconnect)
+                {
+                    continue;
+                }
+                emptyConnections = receivedEvent ? 0 : emptyConnections + 1;
+                if (emptyConnections >= 3)
+                {
+                    output.WriteError(
+                        "watch.reconnect",
+                        "failed",
+                        "The stream closed repeatedly without an event; use bounded polling fallback.",
+                        phase: "live-directory");
+                    return TestClientExitCode.ServiceFailure;
+                }
+                output.Write("watch.reconnect", "required", phase: "live-directory");
+                await Task.Delay(TimeSpan.FromMilliseconds(250), watch.Token).ConfigureAwait(false);
+            }
+        }
+        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
+        {
+            output.Write("watch.complete", "complete", phase: "lifecycle");
+            return TestClientExitCode.Success;
+        }
+    }
+
+    private static bool SameStreamEvent(SessionStreamEvent expected, SessionStreamEvent actual) =>
+        expected.Kind == actual.Kind
+        && string.Equals(expected.Cursor, actual.Cursor, StringComparison.Ordinal)
+        && expected.ListingId == actual.ListingId
+        && expected.Session?.ListingId == actual.Session?.ListingId;
+
+    private static string CorruptCursor(string cursor)
+    {
+        if (string.IsNullOrEmpty(cursor))
+        {
+            return "invalid-stream-cursor";
+        }
+        char replacement = cursor[^1] == 'a' ? 'b' : 'a';
+        return cursor[..^1] + replacement;
+    }
+
     private static async Task<SessionSelection> SelectListingAsync(
         TestClientOptions options,
         TestClientOutput output,

src/FinalFactory.Rendezvous.TestClient/TestClientOptions.cs

@@ -8,6 +8,7 @@ internal enum TestClientMode
 {
     Host,
     Browse,
+    Watch,
     Join,
 }
 
@@ -34,6 +35,8 @@ internal sealed class TestClientOptions
     internal bool Script { get; init; }
     internal bool Json { get; init; }
     internal bool ExitAfterEcho { get; init; }
+    internal bool ExerciseReconnect { get; init; }
+    internal bool ExerciseReset { get; init; }
 }
 
 internal sealed class TestClientParseResult
@@ -63,6 +66,7 @@ internal static class TestClientOptionParser
         Usage:
           rendezvous-test-client host [options]
           rendezvous-test-client browse [options]
+          rendezvous-test-client watch [options]
           rendezvous-test-client join [options]
 
         Common options:
@@ -88,6 +92,11 @@ internal static class TestClientOptionParser
           --run-seconds NUMBER          Stop after 1-86400 seconds
           --exit-after-echo             Stop after an authenticated ping/echo/ack exchange
 
+        Watch options:
+          --run-seconds NUMBER          Stop after 1-86400 seconds
+          --exercise-reconnect          Disconnect after an update and verify ordered replay
+          --exercise-reset              Corrupt the snapshot cursor and verify reset/refresh
+
         Join options:
           --listing UUID                Join an exact listing; otherwise browse/select
 
@@ -129,6 +138,8 @@ internal static class TestClientOptionParser
         bool script = false;
         bool json = false;
         bool exitAfterEcho = false;
+        bool exerciseReconnect = false;
+        bool exerciseReset = false;
         HashSet<string> seen = new(StringComparer.Ordinal);
 
         for (int index = 1; index < args.Length; index++)
@@ -138,7 +149,8 @@ internal static class TestClientOptionParser
             {
                 return TestClientParseResult.Help();
             }
-            if (option is "--script" or "--json" or "--exit-after-echo")
+            if (option is "--script" or "--json" or "--exit-after-echo"
+                or "--exercise-reconnect" or "--exercise-reset")
             {
                 if (!seen.Add(option))
                 {
@@ -147,6 +159,8 @@ internal static class TestClientOptionParser
                 script |= option == "--script";
                 json |= option == "--json";
                 exitAfterEcho |= option == "--exit-after-echo";
+                exerciseReconnect |= option == "--exercise-reconnect";
+                exerciseReset |= option == "--exercise-reset";
                 continue;
             }
             if (!option.StartsWith("--", StringComparison.Ordinal)
@@ -279,8 +293,11 @@ internal static class TestClientOptionParser
             return TestClientParseResult.Failure("One or more game, environment, region, build, or display values violate v1 limits.");
         }
         if (listingId.HasValue && mode != TestClientMode.Join
-            || runSeconds.HasValue && mode != TestClientMode.Host
+            || runSeconds.HasValue && mode is not (TestClientMode.Host or TestClientMode.Watch)
             || exitAfterEcho && mode != TestClientMode.Host
+            || exerciseReconnect && mode != TestClientMode.Watch
+            || exerciseReset && mode != TestClientMode.Watch
+            || exerciseReconnect && exerciseReset
             || metadata.Count > 0 && mode != TestClientMode.Host
             || dedicatedFallback is not null && mode != TestClientMode.Host
             || seen.Contains("--publisher-credential-env") && mode != TestClientMode.Host
@@ -316,6 +333,8 @@ internal static class TestClientOptionParser
             Script = script,
             Json = json,
             ExitAfterEcho = exitAfterEcho,
+            ExerciseReconnect = exerciseReconnect,
+            ExerciseReset = exerciseReset,
         });
     }
 

tests/Diagnostics/diagnostic-dashboard.test.mjs

@@ -0,0 +1,135 @@
+import assert from "node:assert/strict";
+import { readFile } from "node:fs/promises";
+import test from "node:test";
+import {
+  SessionProjection,
+  buildBrowseUrl,
+  buildStreamUrl,
+  chooseSnapshotTransport,
+  safeText,
+} from "../../src/FinalFactory.Rendezvous.Server/Diagnostics/Assets/app.mjs";
+
+const cursor = "rvs1.test-cursor";
+
+function session(id, name = `Host ${id}`) {
+  return {
+    contractVersion: 1,
+    listingId: `00000000-0000-0000-0000-${String(id).padStart(12, "0")}`,
+    gameId: "space-game",
+    environmentId: "smoke",
+    regionId: "local",
+    protocolVersion: 1,
+    buildVersion: "1.0.0",
+    displayName: name,
+    visibility: "public",
+    publisherTrustMode: "managedDedicated",
+    capacity: { currentPlayers: 1, maximumPlayers: 8 },
+    metadata: { mode: "online-coop" },
+  };
+}
+
+function event(kind, values = {}) {
+  return {
+    contractVersion: 1,
+    kind,
+    cursor: values.cursor ?? cursor,
+    session: values.session ?? null,
+    listingId: values.listingId ?? null,
+  };
+}
+
+test("snapshot and ordered deltas match the final public projection", () => {
+  const projection = new SessionProjection(10);
+  assert.equal(projection.replace([session(1)], cursor), "applied");
+  assert.equal(projection.apply(event("sessionUpsert", {
+    cursor: `${cursor}-2`,
+    session: session(2),
+  })), "applied");
+  assert.equal(projection.apply(event("sessionUpsert", {
+    cursor: `${cursor}-3`,
+    session: session(1, "Updated host"),
+  })), "applied");
+  assert.equal(projection.apply(event("sessionRemove", {
+    cursor: `${cursor}-4`,
+    listingId: session(2).listingId,
+  })), "applied");
+
+  assert.deepEqual(
+    projection.sessions().map((entry) => entry.session.displayName),
+    ["Updated host"],
+  );
+  assert.equal(projection.cursor, `${cursor}-4`);
+});
+
+test("reset, malformed events, and a partial snapshot fail closed", () => {
+  const projection = new SessionProjection(2);
+  assert.equal(projection.replace([session(1)], cursor, true), "applied");
+  assert.equal(projection.apply(event("sessionRemove", {
+    listingId: session(1).listingId,
+  })), "refresh");
+  assert.equal(projection.apply(event("reset")), "reset");
+  assert.equal(projection.apply({ kind: "sessionUpsert" }), "invalid");
+  assert.equal(projection.replace([session(1), session(2), session(3)], cursor), "overflow");
+});
+
+test("bursts coalesce by listing identity and memory stays bounded", () => {
+  const projection = new SessionProjection(2);
+  assert.equal(projection.replace([], cursor), "applied");
+  for (let index = 0; index < 1_000; index += 1) {
+    assert.equal(projection.apply(event("sessionUpsert", {
+      cursor: `${cursor}-${index}`,
+      session: session(1, `Host ${index}`),
+    })), "applied");
+  }
+  assert.equal(projection.sessions().length, 1);
+  assert.equal(projection.sessions()[0].session.displayName, "Host 999");
+  assert.equal(projection.apply(event("sessionUpsert", { session: session(2) })), "applied");
+  assert.equal(projection.apply(event("sessionUpsert", { session: session(3) })), "overflow");
+  assert.equal(projection.sessions().length, 2);
+});
+
+test("requests are fixed same-origin paths with an exact configured filter", () => {
+  const filter = {
+    gameId: "space-game",
+    environmentId: "smoke",
+    protocolVersion: 1,
+    regionId: "local",
+    excludeFull: true,
+  };
+  const browse = buildBrowseUrl(filter);
+  const stream = buildStreamUrl(filter, cursor);
+  assert.match(browse, /^\/v1\/sessions\?/u);
+  assert.match(stream, /^\/v1\/sessions\/stream\?/u);
+  assert.match(browse, /gameId=space-game/u);
+  assert.match(browse, /environmentId=smoke/u);
+  assert.match(stream, /streamCursor=rvs1.test-cursor/u);
+  assert.doesNotMatch(browse, /https?:/u);
+  assert.doesNotMatch(stream, /https?:/u);
+});
+
+test("snapshot transport preserves deliberate polling and bounds partial snapshots", () => {
+  assert.equal(chooseSnapshotTransport(false, false), "stream");
+  assert.equal(chooseSnapshotTransport(true, false), "boundedPolling");
+  assert.equal(chooseSnapshotTransport(false, true), "pollingOnly");
+  assert.equal(chooseSnapshotTransport(true, true), "pollingOnly");
+});
+
+test("hostile display data remains literal text and no unsafe DOM sink exists", async () => {
+  const payload = `<img src=x onerror=alert(1)><style>body{display:none}</style><a href=//evil>go</a>`;
+  assert.equal(safeText(payload, 200), payload);
+  const source = await readFile(new URL(
+    "../../src/FinalFactory.Rendezvous.Server/Diagnostics/Assets/app.mjs",
+    import.meta.url,
+  ), "utf8");
+  for (const forbidden of [
+    "innerHTML",
+    "outerHTML",
+    "insertAdjacentHTML",
+    "document.write",
+    "eval(",
+    "new Function",
+    "window.location",
+  ]) {
+    assert.equal(source.includes(forbidden), false, `unsafe browser sink: ${forbidden}`);
+  }
+});

tests/FinalFactory.Rendezvous.Tests/Browser/SessionBrowserTestData.cs

@@ -7,18 +7,25 @@ namespace FinalFactory.Rendezvous.Tests.Browser;
 
 internal sealed class SessionBrowserFixture : IDisposable
 {
-    private readonly EphemeralStateFixture _state = new();
+    private readonly EphemeralStateFixture _state;
 
     public SessionBrowserFixture()
     {
+        Changes = new(new SessionChangeJournalOptions());
+        _state = new(changes: Changes);
         Cursors = new();
-        Browser = new(_state.Store, Cursors, _state.Clock);
+        StreamCursors = new();
+        Browser = new(_state.Store, Cursors, StreamCursors, Changes, _state.Clock);
+        Streams = new(Changes, StreamCursors, _state.Clock);
     }
 
     public InMemoryEphemeralRendezvousStore Store => _state.Store;
     public ManualRendezvousClock Clock => _state.Clock;
     public SessionBrowserCursorCodec Cursors { get; }
+    public SessionStreamCursorCodec StreamCursors { get; }
+    public SessionChangeJournal Changes { get; }
     public SessionBrowserService Browser { get; }
+    public SessionStreamService Streams { get; }
     public TenantScope Scope => _state.Scope;
 
     public StoredListing Add(
@@ -67,5 +74,9 @@ internal sealed class SessionBrowserFixture : IDisposable
         PageSize = pageSize,
     };
 
-    public void Dispose() => Cursors.Dispose();
+    public void Dispose()
+    {
+        Cursors.Dispose();
+        StreamCursors.Dispose();
+    }
 }

tests/FinalFactory.Rendezvous.Tests/Browser/SessionStreamServiceTests.cs

@@ -0,0 +1,325 @@
+using FinalFactory.Rendezvous.Contracts;
+using FinalFactory.Rendezvous.Server.Browser;
+using FinalFactory.Rendezvous.Server.State;
+using FinalFactory.Rendezvous.Tests.State;
+
+namespace FinalFactory.Rendezvous.Tests.Browser;
+
+public sealed class SessionStreamServiceTests
+{
+    [Fact]
+    public void SnapshotPlusUpdateMatchesFreshProjection()
+    {
+        using SessionBrowserFixture fixture = new();
+        StoredListing listing = fixture.Add();
+        BrowseSessionsRequest request = fixture.Request();
+        BrowseSessionsResponse snapshot = AssertSuccess(fixture.Browser.Browse(request));
+        using SessionStreamSubscription subscription = AssertSuccess(
+            fixture.Streams.Subscribe(request, snapshot.StreamCursor));
+
+        StoreResult<StoredListing> updated = fixture.Store.UpdateListing(Update(
+            listing,
+            displayName: "Updated host",
+            currentPlayers: 4));
+        Assert.True(updated.Succeeded);
+        SessionStreamEvent delta = Assert.Single(fixture.Streams.Read(subscription).Events);
+        Assert.Equal(SessionStreamEventKind.SessionUpsert, delta.Kind);
+        Assert.Equal("Updated host", delta.Session!.DisplayName);
+        Assert.Equal(4, delta.Session.Capacity.CurrentPlayers);
+
+        BrowseSessionsResponse fresh = AssertSuccess(fixture.Browser.Browse(request));
+        SessionListing expected = Assert.Single(fresh.Items);
+        Assert.Equal(expected.DisplayName, delta.Session.DisplayName);
+        Assert.Equal(expected.Capacity.CurrentPlayers, delta.Session.Capacity.CurrentPlayers);
+        Assert.DoesNotContain("lease", System.Text.Json.JsonSerializer.Serialize(delta, ContractJson.Options), StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void PresenceStalenessRecoveryAndRevocationProduceRemoveUpsertRemove()
+    {
+        using SessionBrowserFixture fixture = new();
+        StoredListing listing = fixture.Add();
+        BrowseSessionsRequest request = fixture.Request();
+        BrowseSessionsResponse snapshot = AssertSuccess(fixture.Browser.Browse(request));
+        using SessionStreamSubscription subscription = AssertSuccess(
+            fixture.Streams.Subscribe(request, snapshot.StreamCursor));
+
+        fixture.Clock.Advance(TimeSpan.FromSeconds(21));
+        AssertSuccess(fixture.Browser.Browse(request));
+        SessionStreamEvent stale = Assert.Single(fixture.Streams.Read(subscription).Events);
+        Assert.Equal(SessionStreamEventKind.SessionRemove, stale.Kind);
+        Assert.Equal(listing.Definition.ListingId, stale.ListingId);
+
+        StoreResult<StoredListing> rebound = fixture.Store.BindHostPresence(new(
+            listing.Definition.HostPresenceHandle,
+            listing.Definition.HostPresenceFingerprint,
+            new ObservedEndpoint(AddressFamilyKind.Ipv4, "203.0.113.20", 40_020),
+            null));
+        Assert.True(rebound.Succeeded);
+        Assert.Equal(
+            SessionStreamEventKind.SessionUpsert,
+            Assert.Single(fixture.Streams.Read(subscription).Events).Kind);
+
+        Assert.True(fixture.Store.RevokeListing(listing.Definition.ListingId).Succeeded);
+        Assert.Equal(
+            SessionStreamEventKind.SessionRemove,
+            Assert.Single(fixture.Streams.Read(subscription).Events).Kind);
+    }
+
+    [Fact]
+    public void CreationAndLeaseExpiryProduceUpsertThenRemove()
+    {
+        using SessionBrowserFixture fixture = new();
+        BrowseSessionsRequest request = fixture.Request();
+        BrowseSessionsResponse snapshot = AssertSuccess(fixture.Browser.Browse(request));
+        using SessionStreamSubscription subscription = AssertSuccess(
+            fixture.Streams.Subscribe(request, snapshot.StreamCursor));
+
+        StoredListing listing = fixture.Add();
+        SessionStreamEvent created = Assert.Single(fixture.Streams.Read(subscription).Events);
+        Assert.Equal(SessionStreamEventKind.SessionUpsert, created.Kind);
+        Assert.Equal(listing.Definition.ListingId, created.Session!.ListingId);
+
+        for (int refresh = 0; refresh < 3; refresh++)
+        {
+            fixture.Clock.Advance(TimeSpan.FromSeconds(19));
+            Assert.True(fixture.Store.BindHostPresence(new(
+                listing.Definition.HostPresenceHandle,
+                listing.Definition.HostPresenceFingerprint,
+                new ObservedEndpoint(AddressFamilyKind.Ipv4, "203.0.113.20", 40_020),
+                null)).Succeeded);
+        }
+        fixture.Clock.Advance(TimeSpan.FromSeconds(4));
+        AssertSuccess(fixture.Browser.Browse(request));
+
+        SessionStreamEvent expired = Assert.Single(fixture.Streams.Read(subscription).Events);
+        Assert.Equal(SessionStreamEventKind.SessionRemove, expired.Kind);
+        Assert.Equal(listing.Definition.ListingId, expired.ListingId);
+        Assert.Equal(
+            StoreResultCode.NotFound,
+            fixture.Store.GetListing(listing.Definition.ListingId, requireFreshPresence: false).Code);
+    }
+
+    [Fact]
+    public void ScopeProtocolRegionAndFullFiltersNeverLeak()
+    {
+        using SessionBrowserFixture fixture = new();
+        BrowseSessionsRequest request = fixture.Request();
+        request.ExcludeFull = true;
+        BrowseSessionsResponse snapshot = AssertSuccess(fixture.Browser.Browse(request));
+        using SessionStreamSubscription subscription = AssertSuccess(
+            fixture.Streams.Subscribe(request, snapshot.StreamCursor));
+
+        fixture.Add(scope: new(new("other-game"), fixture.Scope.EnvironmentId));
+        fixture.Add(protocolVersion: 99);
+        fixture.Add(regionId: new("other-region"));
+        fixture.Add(currentPlayers: 8, maximumPlayers: 8);
+        Assert.Empty(fixture.Streams.Read(subscription).Events);
+    }
+
+    [Fact]
+    public void VisibilityCompatibilityAndRegionChangesEnterAndLeaveTheFilter()
+    {
+        using SessionBrowserFixture fixture = new();
+        StoredListing listing = fixture.Add();
+        BrowseSessionsRequest request = fixture.Request();
+        BrowseSessionsResponse snapshot = AssertSuccess(fixture.Browser.Browse(request));
+        using SessionStreamSubscription subscription = AssertSuccess(
+            fixture.Streams.Subscribe(request, snapshot.StreamCursor));
+
+        listing = fixture.Store.UpdateListing(Update(
+            listing,
+            listing.Definition.DisplayName,
+            1,
+            visibility: ListingVisibility.Unlisted)).Value!;
+        Assert.Equal(SessionStreamEventKind.SessionRemove, SingleKind(fixture, subscription));
+        listing = fixture.Store.UpdateListing(Update(
+            listing,
+            listing.Definition.DisplayName,
+            1,
+            visibility: ListingVisibility.Public)).Value!;
+        Assert.Equal(SessionStreamEventKind.SessionUpsert, SingleKind(fixture, subscription));
+        listing = fixture.Store.UpdateListing(Update(
+            listing,
+            listing.Definition.DisplayName,
+            1,
+            protocolVersion: 99)).Value!;
+        Assert.Equal(SessionStreamEventKind.SessionRemove, SingleKind(fixture, subscription));
+        listing = fixture.Store.UpdateListing(Update(
+            listing,
+            listing.Definition.DisplayName,
+            1,
+            protocolVersion: 7)).Value!;
+        Assert.Equal(SessionStreamEventKind.SessionUpsert, SingleKind(fixture, subscription));
+        listing = fixture.Store.UpdateListing(Update(
+            listing,
+            listing.Definition.DisplayName,
+            1,
+            regionId: new RegionId("other-region"))).Value!;
+        Assert.Equal(SessionStreamEventKind.SessionRemove, SingleKind(fixture, subscription));
+    }
+
+    [Fact]
+    public void ReplayGapAndForeignCursorForceResetAndSubscriberLimitFailsClosed()
+    {
+        ManualRendezvousClock clock = new();
+        SessionChangeJournal changes = new(new SessionChangeJournalOptions
+        {
+            ReplayCapacity = 64,
+            MaximumSubscribers = 1,
+            MaximumSubscribersPerTenant = 1,
+        });
+        using SessionStreamCursorCodec cursors = new();
+        SessionStreamService streams = new(changes, cursors, clock);
+        EphemeralStateFixture state = new(changes: changes);
+        StoredListing listing = state.CreateVisibleListing(out _);
+        BrowseSessionsRequest request = new()
+        {
+            GameId = state.Scope.GameId,
+            EnvironmentId = state.Scope.EnvironmentId,
+            ProtocolVersion = listing.Definition.ProtocolVersion,
+        };
+        VisibleListingQuery query = new(state.Scope, listing.Definition.ProtocolVersion, null);
+        string initial = cursors.Encode(query, changes.CurrentRevision, clock.UtcNow);
+        using SessionStreamSubscription subscription = AssertSuccess(streams.Subscribe(request, initial));
+        Assert.Equal(
+            RendezvousErrorCode.CapacityExceeded,
+            streams.Subscribe(request, initial).Error);
+
+        for (int index = 0; index < 65; index++)
+        {
+            listing = state.Store.UpdateListing(Update(
+                listing,
+                displayName: $"Host {index}",
+                currentPlayers: index % 8)).Value!;
+        }
+        Assert.True(streams.Read(subscription).RequiresReset);
+        subscription.Dispose();
+
+        using SessionStreamSubscription foreign = AssertSuccess(streams.Subscribe(
+            request,
+            "not-a-valid-cursor"));
+        Assert.True(streams.Read(foreign).RequiresReset);
+    }
+
+    [Fact]
+    public void BurstIsBoundedAndCoalescedWithoutLosingFinalState()
+    {
+        ManualRendezvousClock clock = new();
+        SessionChangeJournal changes = new(new SessionChangeJournalOptions
+        {
+            ReplayCapacity = 1024,
+            MaximumBatchSize = 128,
+        });
+        using SessionStreamCursorCodec cursors = new();
+        SessionStreamService streams = new(changes, cursors, clock);
+        EphemeralStateFixture state = new(changes: changes);
+        StoredListing listing = state.CreateVisibleListing(out _);
+        BrowseSessionsRequest request = new()
+        {
+            GameId = state.Scope.GameId,
+            EnvironmentId = state.Scope.EnvironmentId,
+            ProtocolVersion = listing.Definition.ProtocolVersion,
+        };
+        VisibleListingQuery query = new(state.Scope, listing.Definition.ProtocolVersion, null);
+        using SessionStreamSubscription subscription = AssertSuccess(streams.Subscribe(
+            request,
+            cursors.Encode(query, changes.CurrentRevision, clock.UtcNow)));
+
+        for (int index = 0; index < 1000; index++)
+        {
+            listing = state.Store.UpdateListing(Update(
+                listing,
+                displayName: $"Host {index}",
+                currentPlayers: index % 8)).Value!;
+        }
+
+        List<SessionStreamEvent> emitted = [];
+        while (subscription.Revision < changes.CurrentRevision)
+        {
+            SessionStreamReadResult read = streams.Read(subscription);
+            Assert.False(read.RequiresReset);
+            emitted.AddRange(read.Events);
+        }
+
+        Assert.Equal(8, emitted.Count);
+        SessionStreamEvent final = emitted[^1];
+        Assert.Equal(SessionStreamEventKind.SessionUpsert, final.Kind);
+        Assert.Equal("Host 999", final.Session!.DisplayName);
+        Assert.Equal(7, final.Session.Capacity.CurrentPlayers);
+    }
+
+    [Fact]
+    public void SubscriberLimitIsEnforcedPerTenantAndReleasedOnDispose()
+    {
+        ManualRendezvousClock clock = new();
+        SessionChangeJournal changes = new(new SessionChangeJournalOptions
+        {
+            MaximumSubscribers = 2,
+            MaximumSubscribersPerTenant = 1,
+        });
+        using SessionStreamCursorCodec cursors = new();
+        SessionStreamService streams = new(changes, cursors, clock);
+        TenantScope firstScope = new(new("first-game"), new("production"));
+        TenantScope secondScope = new(new("second-game"), new("production"));
+        BrowseSessionsRequest firstRequest = Request(firstScope);
+        BrowseSessionsRequest secondRequest = Request(secondScope);
+        string firstCursor = cursors.Encode(
+            new VisibleListingQuery(firstScope, 7, null),
+            changes.CurrentRevision,
+            clock.UtcNow);
+        string secondCursor = cursors.Encode(
+            new VisibleListingQuery(secondScope, 7, null),
+            changes.CurrentRevision,
+            clock.UtcNow);
+
+        SessionStreamSubscription first = AssertSuccess(streams.Subscribe(firstRequest, firstCursor));
+        Assert.Equal(
+            RendezvousErrorCode.CapacityExceeded,
+            streams.Subscribe(firstRequest, firstCursor).Error);
+        using SessionStreamSubscription second = AssertSuccess(
+            streams.Subscribe(secondRequest, secondCursor));
+        first.Dispose();
+        using SessionStreamSubscription replacement = AssertSuccess(
+            streams.Subscribe(firstRequest, firstCursor));
+    }
+
+    private static BrowseSessionsRequest Request(TenantScope scope) => new()
+    {
+        GameId = scope.GameId,
+        EnvironmentId = scope.EnvironmentId,
+        ProtocolVersion = 7,
+    };
+
+    private static UpdateListingCommand Update(
+        StoredListing listing,
+        string displayName,
+        int currentPlayers,
+        RegionId? regionId = null,
+        uint? protocolVersion = null,
+        ListingVisibility? visibility = null) => new(
+        listing.Definition.ListingId,
+        listing.Definition.LeaseId,
+        listing.Definition.LeaseFingerprint,
+        listing.Definition.OwnerSubject,
+        listing.Definition.BuildVersion,
+        displayName,
+        currentPlayers,
+        listing.Definition.MaximumPlayers,
+        listing.Definition.Metadata,
+        listing.Definition.DedicatedFallback,
+        regionId,
+        protocolVersion,
+        visibility);
+
+    private static SessionStreamEventKind SingleKind(
+        SessionBrowserFixture fixture,
+        SessionStreamSubscription subscription) =>
+        Assert.Single(fixture.Streams.Read(subscription).Events).Kind;
+
+    private static T AssertSuccess<T>(BrowserServiceResult<T> result)
+    {
+        Assert.True(result.Succeeded, result.Error.ToString());
+        return Assert.IsType<T>(result.Value);
+    }
+}

tests/FinalFactory.Rendezvous.Tests/Client/RendezvousClientBehaviorTests.cs

@@ -167,6 +167,88 @@ public sealed class RendezvousClientBehaviorTests
         Assert.Contains("gameId=space-game", handler.RequestUris[0].Query, StringComparison.Ordinal);
     }
 
+    [Fact]
+    public async Task StreamRejectsMalformedAndOversizedEventEnvelopes()
+    {
+        string[] bodies =
+        [
+            "event: session_upsert\nid: valid-cursor\ndata: {}\n\n",
+            "data: " + new string('x', ContractLimits.SessionStreamEventMaxBytes + 1) + "\n\n",
+        ];
+        foreach (string body in bodies)
+        {
+            StringContent content = new(body, Encoding.UTF8, "text/event-stream");
+            ScriptedHandler handler = new(Response(HttpStatusCode.OK, content));
+            using HttpClient httpClient = new(handler)
+            {
+                BaseAddress = new("http://rendezvous.test/"),
+            };
+            RendezvousSessionBrowserClient browser = new(httpClient);
+            await using IAsyncEnumerator<RendezvousClientResult<SessionStreamEvent>> events = browser
+                .StreamAsync(new BrowseSessionsRequest
+                {
+                    GameId = new("space-game"),
+                    EnvironmentId = new("production"),
+                    ProtocolVersion = 7,
+                }, "valid-stream-cursor")
+                .GetAsyncEnumerator();
+
+            Assert.True(await events.MoveNextAsync());
+            Assert.False(events.Current.IsSuccess);
+            Assert.Equal(RendezvousErrorCode.InternalError, events.Current.Error);
+        }
+    }
+
+    [Fact]
+    public async Task StreamRequiresANonEmptySnapshotCursor()
+    {
+        using HttpClient httpClient = new(new ScriptedHandler())
+        {
+            BaseAddress = new("http://rendezvous.test/"),
+        };
+        RendezvousSessionBrowserClient browser = new(httpClient);
+        await Assert.ThrowsAsync<ArgumentException>(async () =>
+        {
+            await foreach (RendezvousClientResult<SessionStreamEvent> _ in browser.StreamAsync(
+                               new BrowseSessionsRequest
+                               {
+                                   GameId = new("space-game"),
+                                   EnvironmentId = new("production"),
+                                   ProtocolVersion = 7,
+                               },
+                               string.Empty))
+            {
+            }
+        });
+    }
+
+    [Fact]
+    public async Task StreamOpeningIsBoundedByTheConfiguredRequestTimeout()
+    {
+        using HttpClient httpClient = new(new SilentHandler())
+        {
+            BaseAddress = new("http://rendezvous.test/"),
+        };
+        RendezvousSessionBrowserClient browser = new(
+            httpClient,
+            new RendezvousClientOptions
+            {
+                MaximumSafeRetries = 0,
+                RequestTimeout = TimeSpan.FromMilliseconds(20),
+            });
+        await using IAsyncEnumerator<RendezvousClientResult<SessionStreamEvent>> events = browser
+            .StreamAsync(new BrowseSessionsRequest
+            {
+                GameId = new("space-game"),
+                EnvironmentId = new("production"),
+                ProtocolVersion = 7,
+            }, "valid-stream-cursor")
+            .GetAsyncEnumerator();
+
+        Assert.True(await events.MoveNextAsync().AsTask().WaitAsync(TimeSpan.FromSeconds(2)));
+        Assert.Equal(RendezvousErrorCode.ServiceUnavailable, events.Current.Error);
+    }
+
     [Fact]
     public async Task LeaseMaintainerReportsLeaseLoss()
     {

tests/FinalFactory.Rendezvous.Tests/Client/RendezvousClientIntegrationTests.cs

@@ -142,6 +142,82 @@ public sealed class RendezvousClientIntegrationTests
         }
     }
 
+    [Fact]
+    public async Task BrowserStreamResetsInvalidCursorReplaysReconnectAndReleasesConnections()
+    {
+        await using ClientTestHost host = await ClientTestHost.StartAsync();
+        RendezvousPublisherClient publisher = new(host.HttpClient);
+        RendezvousSessionBrowserClient browser = new(
+            host.HttpClient,
+            new RendezvousClientOptions
+            {
+                RequestTimeout = TimeSpan.FromSeconds(15),
+            });
+        PublishedSession session = AssertSuccess(await publisher.RegisterAsync(
+            CreateRegistration(200),
+            host.PublisherCredential));
+        BindPresence(host, session, 41_200);
+        BrowseSessionsRequest request = BrowseRequest();
+        BrowseSessionsResponse snapshot = AssertSuccess(await browser.BrowseAsync(request));
+        Assert.False(string.IsNullOrWhiteSpace(snapshot.StreamCursor));
+
+        using CancellationTokenSource timeout = new(TimeSpan.FromSeconds(30));
+        await using (IAsyncEnumerator<RendezvousClientResult<SessionStreamEvent>> invalid = browser
+                         .StreamAsync(request, CorruptCursor(snapshot.StreamCursor), timeout.Token)
+                         .GetAsyncEnumerator(timeout.Token))
+        {
+            Assert.True(await invalid.MoveNextAsync());
+            Assert.Equal(SessionStreamEventKind.Reset, AssertSuccess(invalid.Current).Kind);
+            Assert.False(await invalid.MoveNextAsync());
+        }
+        await using IAsyncEnumerator<RendezvousClientResult<SessionStreamEvent>> events = browser
+            .StreamAsync(request, snapshot.StreamCursor, timeout.Token)
+            .GetAsyncEnumerator(timeout.Token);
+        Task<bool> upsertPending = events.MoveNextAsync().AsTask();
+        Assert.True((await publisher.UpdateAsync(
+            session,
+            new UpdateSessionRequest
+            {
+                BuildVersion = "2.0.0",
+                DisplayName = "Live update",
+                Capacity = new() { CurrentPlayers = 3, MaximumPlayers = 8 },
+                Metadata = new() { ["mode"] = "online-coop" },
+            },
+            host.PublisherCredential,
+            timeout.Token)).IsSuccess);
+        Assert.True(await upsertPending);
+        SessionStreamEvent upsert = AssertSuccess(events.Current);
+        Assert.Equal(SessionStreamEventKind.SessionUpsert, upsert.Kind);
+        Assert.Equal("Live update", upsert.Session!.DisplayName);
+
+        await using (IAsyncEnumerator<RendezvousClientResult<SessionStreamEvent>> replay = browser
+                         .StreamAsync(request, snapshot.StreamCursor, timeout.Token)
+                         .GetAsyncEnumerator(timeout.Token))
+        {
+            Assert.True(await replay.MoveNextAsync());
+            SessionStreamEvent replayed = AssertSuccess(replay.Current);
+            Assert.Equal(SessionStreamEventKind.SessionUpsert, replayed.Kind);
+            Assert.Equal(upsert.Cursor, replayed.Cursor);
+            Assert.Equal("Live update", replayed.Session!.DisplayName);
+        }
+
+        Task<bool> removePending = events.MoveNextAsync().AsTask();
+        Assert.True((await publisher.DeregisterAsync(
+            session,
+            host.PublisherCredential,
+            timeout.Token)).IsSuccess);
+        Assert.True(await removePending);
+        SessionStreamEvent remove = AssertSuccess(events.Current);
+        Assert.Equal(SessionStreamEventKind.SessionRemove, remove.Kind);
+        Assert.Equal(session.ListingId, remove.ListingId);
+    }
+
+    private static string CorruptCursor(string cursor)
+    {
+        char replacement = cursor[^1] == 'a' ? 'b' : 'a';
+        return cursor[..^1] + replacement;
+    }
+
     private static T AssertSuccess<T>(RendezvousClientResult<T> result)
     {
         Assert.True(result.IsSuccess, result.Message);
@@ -210,7 +286,8 @@ public sealed class RendezvousClientIntegrationTests
         {
             ManualRendezvousClock clock = new(ProvisioningTestData.Now);
             EphemeralStoreOptions stateOptions = new();
-            InMemoryEphemeralRendezvousStore store = new(stateOptions, clock, clock);
+            SessionChangeJournal changes = new(new SessionChangeJournalOptions());
+            InMemoryEphemeralRendezvousStore store = new(stateOptions, clock, clock, changes);
             EphemeralCapabilityIssuer capabilities = new();
             ProvisioningRuntime provisioning = ProvisioningRuntime.Create(
                 ProvisioningTestData.CreateOptions(),
@@ -239,7 +316,10 @@ public sealed class RendezvousClientIntegrationTests
             builder.Services.AddSingleton(SessionLeaseTiming.From(stateOptions));
             builder.Services.AddSingleton<SessionLeaseService>();
             builder.Services.AddSingleton<SessionBrowserCursorCodec>();
+            builder.Services.AddSingleton<SessionStreamCursorCodec>();
+            builder.Services.AddSingleton(changes);
             builder.Services.AddSingleton<SessionBrowserService>();
+            builder.Services.AddSingleton<SessionStreamService>();
 
             WebApplication app = builder.Build();
             app.UseExceptionHandler();

tests/FinalFactory.Rendezvous.Tests/Contracts/OpenApiCompatibilityTests.cs

@@ -17,6 +17,7 @@ public sealed class OpenApiCompatibilityTests
         "/v1/operator/principals/revoke",
         "/v1/operator/status",
         "/v1/sessions",
+        "/v1/sessions/stream",
         "/v1/sessions/{listingId}",
         "/v1/sessions/{listingId}/join-attempts",
         "/v1/sessions/{listingId}/renew",
@@ -68,6 +69,25 @@ public sealed class OpenApiCompatibilityTests
         Assert.DoesNotContain(listingProperties, static property =>
             property.Contains("token", StringComparison.OrdinalIgnoreCase)
             || property.Contains("playerId", StringComparison.OrdinalIgnoreCase));
+        JsonElement streamProperties = schemas.GetProperty("SessionStreamEvent")
+            .GetProperty("properties");
+        Assert.True(streamProperties.TryGetProperty("contractVersion", out _));
+        Assert.True(streamProperties.TryGetProperty("kind", out _));
+        Assert.True(streamProperties.TryGetProperty("cursor", out _));
+        Assert.True(streamProperties.TryGetProperty("session", out _));
+        Assert.True(streamProperties.TryGetProperty("listingId", out _));
+        Assert.DoesNotContain(streamProperties.EnumerateObject(), static property =>
+            property.Name.Contains("token", StringComparison.OrdinalIgnoreCase)
+            || property.Name.Contains("capability", StringComparison.OrdinalIgnoreCase)
+            || property.Name.Contains("ticket", StringComparison.OrdinalIgnoreCase)
+            || property.Name.Contains("endpoint", StringComparison.OrdinalIgnoreCase));
+        Assert.True(root.GetProperty("paths")
+            .GetProperty("/v1/sessions/stream")
+            .GetProperty("get")
+            .GetProperty("responses")
+            .GetProperty("200")
+            .GetProperty("content")
+            .TryGetProperty("text/event-stream", out _));
         JsonElement dedicatedFallback = schemas.GetProperty("SessionListing")
             .GetProperty("properties")
             .GetProperty("dedicatedFallback");
@@ -205,7 +225,7 @@ public sealed class OpenApiCompatibilityTests
             }
         }
 
-        Assert.Equal(17, overloadContracts);
+        Assert.Equal(18, overloadContracts);
         (string Path, string Method)[] bodyOperations =
         [
             ("/v1/sessions", "post"),

tests/FinalFactory.Rendezvous.Tests/Diagnostics/DiagnosticDashboardTests.cs

@@ -0,0 +1,205 @@
+using System.Net;
+using System.Net.Sockets;
+using System.Text.Json;
+using FinalFactory.Rendezvous.Server.Diagnostics;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+namespace FinalFactory.Rendezvous.Tests.Diagnostics;
+
+public sealed class DiagnosticDashboardTests
+{
+    [Fact]
+    public void ConfigurationRequiresBoundedUniqueAllowListedScopes()
+    {
+        Assert.Empty(ValidOptions().Validate());
+        Assert.Empty(new DiagnosticDashboardOptions().Validate());
+
+        DiagnosticDashboardOptions invalid = ValidOptions() with
+        {
+            PollIntervalSeconds = 1,
+            MaximumRenderedSessions = 501,
+            Scopes =
+            [
+                new DiagnosticDashboardScope
+                {
+                    GameId = "INVALID",
+                    EnvironmentId = "smoke",
+                    ProtocolVersions = [0, 0],
+                    Regions = ["INVALID", "INVALID"],
+                },
+                new DiagnosticDashboardScope
+                {
+                    GameId = "INVALID",
+                    EnvironmentId = "smoke",
+                    ProtocolVersions = [1],
+                    Regions = ["local"],
+                },
+            ],
+        };
+
+        IReadOnlyList<string> errors = invalid.Validate();
+        Assert.Contains(errors, error => error.Contains("PollIntervalSeconds", StringComparison.Ordinal));
+        Assert.Contains(errors, error => error.Contains("MaximumRenderedSessions", StringComparison.Ordinal));
+        Assert.Contains(errors, error => error.Contains("invalid game", StringComparison.Ordinal));
+        Assert.Contains(errors, error => error.Contains("protocol versions", StringComparison.Ordinal));
+        Assert.Contains(errors, error => error.Contains("regions", StringComparison.Ordinal));
+        Assert.Contains(errors, error => error.Contains("duplicate", StringComparison.Ordinal));
+
+        DiagnosticDashboardOptions nullBound = ValidOptions() with
+        {
+            Scopes = null!,
+        };
+        Assert.Contains(
+            nullBound.Validate(),
+            error => error.Contains("Scopes must contain", StringComparison.Ordinal));
+        DiagnosticDashboardOptions nullScope = ValidOptions() with
+        {
+            Scopes = [null!],
+        };
+        Assert.Contains(
+            nullScope.Validate(),
+            error => error.Contains("null entries", StringComparison.Ordinal));
+        DiagnosticDashboardOptions nullCollections = ValidOptions() with
+        {
+            Scopes =
+            [
+                new DiagnosticDashboardScope
+                {
+                    GameId = null!,
+                    EnvironmentId = null!,
+                    ProtocolVersions = null!,
+                    Regions = null!,
+                },
+            ],
+        };
+        Assert.True(nullCollections.Validate().Count >= 3);
+    }
+
+    [Fact]
+    public async Task DisabledDashboardHasNoPublicAssetOrConfigurationSurface()
+    {
+        await using DashboardHost host = await DashboardHost.StartAsync(new());
+
+        Assert.Equal(HttpStatusCode.NotFound, (await host.Client.GetAsync("diagnostics/")).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await host.Client.GetAsync("diagnostics/app.mjs")).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await host.Client.GetAsync("diagnostics/config.json")).StatusCode);
+    }
+
+    [Fact]
+    public async Task EnabledDashboardServesOnlyHardenedSameOriginReadOnlyAssets()
+    {
+        await using DashboardHost host = await DashboardHost.StartAsync(ValidOptions());
+        using HttpRequestMessage request = new(HttpMethod.Get, "diagnostics/");
+        request.Headers.Add("Origin", "https://hostile.example");
+        using HttpResponseMessage response = await host.Client.SendAsync(request);
+        string html = await response.Content.ReadAsStringAsync();
+
+        Assert.True(response.IsSuccessStatusCode, html);
+        Assert.Equal("text/html", response.Content.Headers.ContentType?.MediaType);
+        Assert.Equal("DENY", Header(response, "X-Frame-Options"));
+        Assert.Equal("nosniff", Header(response, "X-Content-Type-Options"));
+        Assert.Equal("no-referrer", Header(response, "Referrer-Policy"));
+        Assert.Contains("default-src 'none'", Header(response, "Content-Security-Policy"), StringComparison.Ordinal);
+        Assert.Contains("connect-src 'self'", Header(response, "Content-Security-Policy"), StringComparison.Ordinal);
+        Assert.Contains("frame-ancestors 'none'", Header(response, "Content-Security-Policy"), StringComparison.Ordinal);
+        Assert.False(response.Headers.Contains("Access-Control-Allow-Origin"));
+        Assert.Contains("<html lang=\"en\">", html, StringComparison.Ordinal);
+        Assert.Contains("href=\"#main-content\"", html, StringComparison.Ordinal);
+        Assert.Contains("aria-live=\"polite\"", html, StringComparison.Ordinal);
+        Assert.Contains("type=\"module\" src=\"/diagnostics/app.mjs\"", html, StringComparison.Ordinal);
+        Assert.DoesNotContain("<script src=\"http", html, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("/v1/operator", html, StringComparison.OrdinalIgnoreCase);
+
+        using HttpResponseMessage scriptResponse = await host.Client.GetAsync("diagnostics/app.mjs");
+        string script = await scriptResponse.Content.ReadAsStringAsync();
+        Assert.Equal("text/javascript", scriptResponse.Content.Headers.ContentType?.MediaType);
+        Assert.DoesNotContain("/v1/operator", script, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("Authorization", script, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("innerHTML", script, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public async Task BrowserConfigurationContainsOnlyTheExplicitPublicAllowList()
+    {
+        await using DashboardHost host = await DashboardHost.StartAsync(ValidOptions());
+        using HttpResponseMessage response = await host.Client.GetAsync("diagnostics/config.json");
+        using JsonDocument document = JsonDocument.Parse(await response.Content.ReadAsStringAsync());
+        JsonElement root = document.RootElement;
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(1, root.GetProperty("contractVersion").GetInt32());
+        Assert.Equal(10, root.GetProperty("pollIntervalSeconds").GetInt32());
+        JsonElement scope = Assert.Single(root.GetProperty("scopes").EnumerateArray());
+        Assert.Equal("space-game", scope.GetProperty("gameId").GetString());
+        Assert.Equal("smoke", scope.GetProperty("environmentId").GetString());
+        Assert.Equal("public", scope.GetProperty("visibility").GetString());
+        string json = root.GetRawText();
+        Assert.DoesNotContain("http", json, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("credential", json, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("token", json, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain("endpoint", json, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static string Header(HttpResponseMessage response, string name) =>
+        Assert.Single(response.Headers.GetValues(name));
+
+    private static DiagnosticDashboardOptions ValidOptions() => new()
+    {
+        Enabled = true,
+        PollIntervalSeconds = 10,
+        MaximumRenderedSessions = 100,
+        Scopes =
+        [
+            new DiagnosticDashboardScope
+            {
+                GameId = "space-game",
+                EnvironmentId = "smoke",
+                ProtocolVersions = [1, 2],
+                Regions = ["local"],
+            },
+        ],
+    };
+
+    private sealed class DashboardHost : IAsyncDisposable
+    {
+        private readonly WebApplication _application;
+
+        private DashboardHost(WebApplication application, HttpClient client)
+        {
+            _application = application;
+            Client = client;
+        }
+
+        public HttpClient Client { get; }
+
+        public static async Task<DashboardHost> StartAsync(DiagnosticDashboardOptions options)
+        {
+            int port = ReserveTcpPort();
+            string address = $"http://127.0.0.1:{port}";
+            WebApplicationBuilder builder = WebApplication.CreateBuilder();
+            builder.WebHost.UseUrls(address);
+            builder.Services.AddSingleton(Options.Create(options));
+            WebApplication application = builder.Build();
+            application.MapDiagnosticDashboardEndpoints();
+            await application.StartAsync();
+            return new(application, new HttpClient { BaseAddress = new Uri(address) });
+        }
+
+        public async ValueTask DisposeAsync()
+        {
+            Client.Dispose();
+            await _application.StopAsync();
+            await _application.DisposeAsync();
+        }
+
+        private static int ReserveTcpPort()
+        {
+            using TcpListener listener = new(IPAddress.Loopback, 0);
+            listener.Start();
+            return ((IPEndPoint)listener.LocalEndpoint).Port;
+        }
+    }
+}

tests/FinalFactory.Rendezvous.Tests/Documentation/DocumentationContractTests.cs

@@ -61,6 +61,10 @@ public sealed partial class DocumentationContractTests
         Assert.Contains("metadata.st_mode & 0o077", helper, StringComparison.Ordinal);
         Assert.Contains("metadata.st_nlink != 1", helper, StringComparison.Ordinal);
         Assert.Contains("mint-local-publisher-credential.sh", smoke, StringComparison.Ordinal);
+        Assert.Contains("select(.event == \"host.ready\" and .status == \"ready\")", smoke, StringComparison.Ordinal);
+        Assert.Contains("hasListingId", smoke, StringComparison.Ordinal);
+        Assert.Contains("jq -s -e", smoke, StringComparison.Ordinal);
+        Assert.DoesNotContain("jq -c .", smoke, StringComparison.Ordinal);
         Assert.DoesNotContain("hexkey:", smoke, StringComparison.Ordinal);
         Assert.DoesNotContain("openssl dgst", smoke, StringComparison.Ordinal);
     }

tests/FinalFactory.Rendezvous.Tests/JoinAttempts/JoinAttemptHttpEndpointTests.cs

@@ -288,7 +288,8 @@ public sealed class JoinAttemptHttpEndpointTests
         {
             ManualRendezvousClock clock = new(ProvisioningTestData.Now);
             EphemeralStoreOptions stateOptions = new();
-            InMemoryEphemeralRendezvousStore store = new(stateOptions, clock, clock);
+            SessionChangeJournal changes = new(new SessionChangeJournalOptions());
+            InMemoryEphemeralRendezvousStore store = new(stateOptions, clock, clock, changes);
             EphemeralCapabilityIssuer capabilities = new();
             ProvisioningRuntime provisioning = ProvisioningRuntime.Create(
                 ProvisioningTestData.CreateOptions(),
@@ -318,7 +319,10 @@ public sealed class JoinAttemptHttpEndpointTests
             builder.Services.AddSingleton(SessionLeaseTiming.From(stateOptions));
             builder.Services.AddSingleton<SessionLeaseService>();
             builder.Services.AddSingleton<SessionBrowserCursorCodec>();
+            builder.Services.AddSingleton<SessionStreamCursorCodec>();
+            builder.Services.AddSingleton(changes);
             builder.Services.AddSingleton<SessionBrowserService>();
+            builder.Services.AddSingleton<SessionStreamService>();
             builder.Services.AddSingleton<JoinAttemptCursorCodec>();
             builder.Services.AddSingleton<JoinAttemptService>();
             ConnectionOutcomeMetrics outcomeMetrics = new();

tests/FinalFactory.Rendezvous.Tests/Observability/PrometheusMetricsTests.cs

@@ -0,0 +1,165 @@
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using FinalFactory.Rendezvous.Server.Browser;
+using FinalFactory.Rendezvous.Server.Observability;
+using FinalFactory.Rendezvous.Server.Provisioning;
+using FinalFactory.Rendezvous.Server.State;
+using FinalFactory.Rendezvous.Tests.State;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace FinalFactory.Rendezvous.Tests.Observability;
+
+[Collection(RendezvousTelemetryIsolation.Name)]
+public sealed class PrometheusMetricsTests
+{
+    private const string Token = "0123456789abcdef0123456789abcdef";
+
+    [Fact]
+    public void EnabledExporterRequiresAnExternalBoundedSecretReference()
+    {
+        Assert.Empty(new PrometheusMetricsOptions().Validate());
+        Assert.Empty(new PrometheusMetricsOptions
+        {
+            Enabled = true,
+            BearerTokenSecretReference = "file:/run/secrets/rendezvous-metrics-token",
+        }.Validate());
+        Assert.NotEmpty(new PrometheusMetricsOptions { Enabled = true }.Validate());
+        Assert.NotEmpty(new PrometheusMetricsOptions
+        {
+            Enabled = true,
+            BearerTokenSecretReference = "literal-secret",
+        }.Validate());
+        Assert.NotEmpty(new PrometheusMetricsOptions
+        {
+            Enabled = true,
+            BearerTokenSecretReference = "file:relative-token",
+        }.Validate());
+        Assert.NotEmpty(new PrometheusMetricsOptions
+        {
+            Enabled = true,
+            BearerTokenSecretReference = null!,
+        }.Validate());
+    }
+
+    [Fact]
+    public async Task ExporterIsDisabledByDefaultAndConcealsRejectedAuthentication()
+    {
+        await using MetricsHost disabled = await MetricsHost.StartAsync(
+            new PrometheusMetricsOptions(),
+            credential: null);
+        Assert.Equal(HttpStatusCode.NotFound, (await disabled.Client.GetAsync("metrics")).StatusCode);
+
+        PrometheusMetricsOptions options = EnabledOptions();
+        using MetricsAccessCredential credential = Credential(options);
+        await using MetricsHost enabled = await MetricsHost.StartAsync(options, credential);
+        Assert.Equal(HttpStatusCode.NotFound, (await enabled.Client.GetAsync("metrics")).StatusCode);
+        using HttpRequestMessage wrong = new(HttpMethod.Get, "metrics");
+        wrong.Headers.Authorization = new("Bearer", new string('x', 32));
+        Assert.Equal(HttpStatusCode.NotFound, (await enabled.Client.SendAsync(wrong)).StatusCode);
+    }
+
+    [Fact]
+    public async Task AuthenticatedExporterReturnsBoundedPrivacySafePrometheusFamilies()
+    {
+        PrometheusMetricsOptions options = EnabledOptions();
+        using MetricsAccessCredential credential = Credential(options);
+        await using MetricsHost host = await MetricsHost.StartAsync(options, credential);
+        host.Telemetry.RecordHttp("BrowseSessions", 200, 3.5);
+        host.Telemetry.RecordHttp("listing-id/canary", 500, 4.5);
+        host.Telemetry.RecordUdp("frozen", "Introduced", 1.25, 128, 2400);
+        host.Telemetry.RecordLimiterDrop("udp", "rate-or-concurrency");
+        host.Telemetry.RecordConnectionOutcome("Connected", "UnderOneSecond");
+        host.Telemetry.RecordPairingLatency(12.5);
+        using HttpRequestMessage request = new(HttpMethod.Get, "metrics");
+        request.Headers.Authorization = new("Bearer", Token);
+        using HttpResponseMessage response = await host.Client.SendAsync(request);
+        string body = await response.Content.ReadAsStringAsync();
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal("text/plain", response.Content.Headers.ContentType?.MediaType);
+        Assert.Equal("no-store", response.Headers.CacheControl?.ToString());
+        Assert.Contains("rendezvous_http_requests_total{operation=\"BrowseSessions\",status_code=\"200\"} 1", body, StringComparison.Ordinal);
+        Assert.Contains("rendezvous_http_duration_milliseconds_bucket", body, StringComparison.Ordinal);
+        Assert.Contains("rendezvous_udp_received_bytes_total{operation=\"frozen\"} 128", body, StringComparison.Ordinal);
+        Assert.Contains("rendezvous_udp_response_budget_bytes_total{operation=\"frozen\"} 2400", body, StringComparison.Ordinal);
+        Assert.Contains("rendezvous_store_active_listings", body, StringComparison.Ordinal);
+        Assert.Contains("rendezvous_browser_sse_subscribers", body, StringComparison.Ordinal);
+        Assert.Contains("process_resident_memory_bytes", body, StringComparison.Ordinal);
+        Assert.Contains("dotnet_gc_heap_size_bytes", body, StringComparison.Ordinal);
+        Assert.Contains("operation=\"other\"", body, StringComparison.Ordinal);
+        Assert.DoesNotContain("listing-id", body, StringComparison.OrdinalIgnoreCase);
+        Assert.DoesNotContain(Token, body, StringComparison.Ordinal);
+    }
+
+    private static PrometheusMetricsOptions EnabledOptions() => new()
+    {
+        Enabled = true,
+        BearerTokenSecretReference = "file:/metrics-token",
+    };
+
+    private static MetricsAccessCredential Credential(PrometheusMetricsOptions options)
+    {
+        using DictionarySecretProvider secrets = new(new Dictionary<string, byte[]>
+        {
+            [options.BearerTokenSecretReference] = Encoding.ASCII.GetBytes(Token + "\n"),
+        });
+        Assert.True(MetricsAccessCredential.TryCreate(options, secrets, out MetricsAccessCredential? credential));
+        return Assert.IsType<MetricsAccessCredential>(credential);
+    }
+
+    private sealed class MetricsHost : IAsyncDisposable
+    {
+        private readonly WebApplication _application;
+
+        private MetricsHost(
+            WebApplication application,
+            HttpClient client,
+            RendezvousTelemetry telemetry)
+        {
+            _application = application;
+            Client = client;
+            Telemetry = telemetry;
+        }
+
+        public HttpClient Client { get; }
+        public RendezvousTelemetry Telemetry { get; }
+
+        public static async Task<MetricsHost> StartAsync(
+            PrometheusMetricsOptions options,
+            MetricsAccessCredential? credential)
+        {
+            ManualRendezvousClock clock = new();
+            SessionChangeJournal changes = new(new SessionChangeJournalOptions());
+            InMemoryEphemeralRendezvousStore store = new(new(), clock, clock, changes);
+            RendezvousTelemetry telemetry = new(store, changes);
+            int port = ReserveTcpPort();
+            string address = $"http://127.0.0.1:{port}";
+            WebApplicationBuilder builder = WebApplication.CreateBuilder();
+            builder.WebHost.UseUrls(address);
+            builder.Services.AddSingleton(telemetry);
+            WebApplication application = builder.Build();
+            application.MapPrometheusMetricsEndpoint(options, credential);
+            await application.StartAsync();
+            return new(application, new HttpClient { BaseAddress = new Uri(address) }, telemetry);
+        }
+
+        public async ValueTask DisposeAsync()
+        {
+            Client.Dispose();
+            await _application.StopAsync();
+            await _application.DisposeAsync();
+            // This test supplies an existing singleton instance, so the host does not own it.
+            Telemetry.Dispose();
+        }
+
+        private static int ReserveTcpPort()
+        {
+            using TcpListener listener = new(IPAddress.Loopback, 0);
+            listener.Start();
+            return ((IPEndPoint)listener.LocalEndpoint).Port;
+        }
+    }
+}

tests/FinalFactory.Rendezvous.Tests/Release/ReleaseCompatibilityTests.cs

@@ -149,6 +149,68 @@ public sealed class ReleaseCompatibilityTests
         Assert.Contains("<PackageReference Remove=\"FinalFactory.Rendezvous.Contracts\" />", realConsumerGate, StringComparison.Ordinal);
     }
 
+    [Fact]
+    public void AutomationProvidesNet8RuntimeForProcessVerification()
+    {
+        string root = FindRepositoryRoot();
+        string qualityWorkflow = File.ReadAllText(Path.Combine(root, ".gitea/workflows/ci.yml"));
+        Assert.Equal(2, qualityWorkflow.Split("8.0.128", StringSplitOptions.None).Length - 1);
+
+        string releaseWorkflow = File.ReadAllText(Path.Combine(root, ".gitea/workflows/release.yml"));
+        Assert.Contains("8.0.128", releaseWorkflow, StringComparison.Ordinal);
+
+        string releaseBuilder = File.ReadAllText(Path.Combine(root, "eng/release-builder.Dockerfile"));
+        Assert.Contains("runtime:8.0.28-noble@sha256:", releaseBuilder, StringComparison.Ordinal);
+        Assert.Contains("Microsoft.NETCore.App/8.0.28", releaseBuilder, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void AutomationUsesPerRunContainerPorts()
+    {
+        string root = FindRepositoryRoot();
+        string compose = File.ReadAllText(Path.Combine(root, "deploy/compose/compose.yaml"));
+        Assert.Contains("${RENDEZVOUS_HTTP_HOST_PORT:-8080}:8080/tcp", compose, StringComparison.Ordinal);
+        Assert.Contains("${RENDEZVOUS_UDP_HOST_PORT:-9050}:9050/udp", compose, StringComparison.Ordinal);
+        Assert.Contains("${RENDEZVOUS_CONFIG_SOURCE:-./appsettings.Production.json}", compose, StringComparison.Ordinal);
+        Assert.Contains("${RENDEZVOUS_SECRET_SOURCE:-./secrets/signing-key}", compose, StringComparison.Ordinal);
+
+        foreach (string workflowName in new[] { "ci.yml", "release.yml" })
+        {
+            string workflow = File.ReadAllText(Path.Combine(root, ".gitea/workflows", workflowName));
+            Assert.Contains("GITHUB_RUN_ID", workflow, StringComparison.Ordinal);
+            Assert.Contains("--network \"container:${container_id}\"", workflow, StringComparison.Ordinal);
+            Assert.Contains("publisher_credential", workflow, StringComparison.Ordinal);
+            Assert.Contains("RENDEZVOUS_PUBLISHER_CREDENTIAL", workflow, StringComparison.Ordinal);
+            Assert.Contains("for attempt in {1..180}", workflow, StringComparison.Ordinal);
+            Assert.Contains("sleep 1", workflow, StringComparison.Ordinal);
+            Assert.Contains("http://127.0.0.1:8080/", workflow, StringComparison.Ordinal);
+            Assert.Contains("127.0.0.1:9050", workflow, StringComparison.Ordinal);
+            Assert.Contains("RENDEZVOUS_HTTP_HOST_PORT", workflow, StringComparison.Ordinal);
+            Assert.Contains("RENDEZVOUS_UDP_HOST_PORT", workflow, StringComparison.Ordinal);
+            Assert.Contains("RENDEZVOUS_SMOKE_HTTP_URL", workflow, StringComparison.Ordinal);
+            Assert.Contains("RENDEZVOUS_SMOKE_UDP_ENDPOINT", workflow, StringComparison.Ordinal);
+            Assert.Contains("runner_workspace_source", workflow, StringComparison.Ordinal);
+            Assert.Contains("RENDEZVOUS_CONFIG_SOURCE", workflow, StringComparison.Ordinal);
+            Assert.Contains("RENDEZVOUS_SECRET_SOURCE", workflow, StringComparison.Ordinal);
+        }
+    }
+
+    [Fact]
+    public void ContainerGateUsesValidInspectTemplates()
+    {
+        string root = FindRepositoryRoot();
+        string workflow = File.ReadAllText(Path.Combine(root, ".gitea/workflows/ci.yml"));
+        Assert.Contains(
+            "eq .Destination \"/app/appsettings.Production.json\"",
+            workflow,
+            StringComparison.Ordinal);
+        Assert.Contains(
+            "eq .Destination \"/run/secrets/rendezvous-signing-key\"",
+            workflow,
+            StringComparison.Ordinal);
+        Assert.DoesNotContain("eq .Destination \\\"", workflow, StringComparison.Ordinal);
+    }
+
     [Fact]
     public void ServerSourceManifestIsCompleteSortedAndDeterministic()
     {

tests/FinalFactory.Rendezvous.Tests/Sessions/SessionHttpEndpointTests.cs

@@ -28,7 +28,8 @@ public sealed class SessionHttpEndpointTests
     {
         ManualRendezvousClock clock = new(ProvisioningTestData.Now);
         EphemeralStoreOptions stateOptions = new();
-        InMemoryEphemeralRendezvousStore store = new(stateOptions, clock, clock);
+        SessionChangeJournal changes = new(new SessionChangeJournalOptions());
+        InMemoryEphemeralRendezvousStore store = new(stateOptions, clock, clock, changes);
         EphemeralCapabilityIssuer capabilities = new();
         ProvisioningRuntime provisioning = ProvisioningRuntime.Create(
             ProvisioningTestData.CreateOptions(),
@@ -57,7 +58,10 @@ public sealed class SessionHttpEndpointTests
         builder.Services.AddSingleton(SessionLeaseTiming.From(stateOptions));
         builder.Services.AddSingleton<SessionLeaseService>();
         builder.Services.AddSingleton<SessionBrowserCursorCodec>();
+        builder.Services.AddSingleton<SessionStreamCursorCodec>();
+        builder.Services.AddSingleton(changes);
         builder.Services.AddSingleton<SessionBrowserService>();
+        builder.Services.AddSingleton<SessionStreamService>();
         await using WebApplication app = builder.Build();
         app.UseExceptionHandler();
         app.UseMiddleware<HttpAbuseProtectionMiddleware>();

tests/FinalFactory.Rendezvous.Tests/State/EphemeralStateTestData.cs

@@ -1,4 +1,5 @@
 using FinalFactory.Rendezvous.Contracts;
+using FinalFactory.Rendezvous.Server.Browser;
 using FinalFactory.Rendezvous.Server.State;
 
 namespace FinalFactory.Rendezvous.Tests.State;
@@ -24,10 +25,12 @@ internal sealed class EphemeralStateFixture
 {
     private int _sequence;
 
-    public EphemeralStateFixture(EphemeralStoreOptions? options = null)
+    public EphemeralStateFixture(
+        EphemeralStoreOptions? options = null,
+        SessionChangeJournal? changes = null)
     {
         Clock = new();
-        Store = new(options ?? new EphemeralStoreOptions(), Clock, Clock);
+        Store = new(options ?? new EphemeralStoreOptions(), Clock, Clock, changes);
     }
 
     public ManualRendezvousClock Clock { get; }

tests/FinalFactory.Rendezvous.Tests/TestClient/TestClientCommandTests.cs

@@ -59,6 +59,29 @@ public sealed class TestClientCommandTests
         Assert.Equal(130, (int)TestClientExitCode.Cancelled);
     }
 
+    [Fact]
+    public void WatchModeSupportsBoundedRuntimeAndDeliberateRecoveryExercisesOnly()
+    {
+        TestClientParseResult reset = TestClientOptionParser.Parse(
+            ["watch", "--run-seconds", "30", "--exercise-reset", "--script", "--json"]);
+        Assert.True(reset.Succeeded, reset.Error);
+        TestClientOptions resetOptions = Assert.IsType<TestClientOptions>(reset.Options);
+        Assert.Equal(TestClientMode.Watch, resetOptions.Mode);
+        Assert.Equal(TimeSpan.FromSeconds(30), resetOptions.RunDuration);
+        Assert.True(resetOptions.ExerciseReset);
+
+        TestClientParseResult reconnect = TestClientOptionParser.Parse(
+            ["watch", "--exercise-reconnect", "--script"]);
+        Assert.True(reconnect.Succeeded, reconnect.Error);
+        Assert.True(Assert.IsType<TestClientOptions>(reconnect.Options).ExerciseReconnect);
+
+        Assert.False(TestClientOptionParser.Parse(["browse", "--exercise-reconnect"]).Succeeded);
+        Assert.False(TestClientOptionParser.Parse(["browse", "--exercise-reset"]).Succeeded);
+        Assert.False(TestClientOptionParser.Parse(
+            ["watch", "--exercise-reconnect", "--exercise-reset"]).Succeeded);
+        Assert.False(TestClientOptionParser.Parse(["join", "--run-seconds", "30"]).Succeeded);
+    }
+
     [Fact]
     public void HostFailureBudgetStopsAuthorityLossAndBoundsTransientRetries()
     {

tests/FinalFactory.Rendezvous.Tests/TestData/Contracts/v1/browse-sessions.json

@@ -1 +1 @@
-{"contractVersion":1,"items":[{"contractVersion":1,"listingId":"00112233-4455-6677-8899-aabbccddeeff","gameId":"space-game","environmentId":"production","regionId":"eu-central","protocolVersion":7,"buildVersion":"1.4.2","displayName":"Europa Relay","visibility":"public","publisherTrustMode":"managedDedicated","capacity":{"currentPlayers":2,"maximumPlayers":8},"metadata":{"mode":"co-op","map":"europa"}}],"nextCursor":"cursor-002"}
+{"contractVersion":1,"items":[{"contractVersion":1,"listingId":"00112233-4455-6677-8899-aabbccddeeff","gameId":"space-game","environmentId":"production","regionId":"eu-central","protocolVersion":7,"buildVersion":"1.4.2","displayName":"Europa Relay","visibility":"public","publisherTrustMode":"managedDedicated","capacity":{"currentPlayers":2,"maximumPlayers":8},"metadata":{"mode":"co-op","map":"europa"}}],"nextCursor":"cursor-002","streamCursor":"stream-cursor-002"}

tests/FinalFactory.Rendezvous.Tests/TestData/Contracts/v1/client-public-api.txt

@@ -40,6 +40,7 @@ TYPE FinalFactory.Rendezvous.Client.IRendezvousSessionBrowserClient
   METHOD System.Threading.Tasks.Task<FinalFactory.Rendezvous.Client.RendezvousClientResult<System.Collections.Generic.IReadOnlyList<FinalFactory.Rendezvous.Contracts.SessionListing>>> BrowseAllAsync(FinalFactory.Rendezvous.Contracts.BrowseSessionsRequest request, System.Int32 maximumPages, System.Threading.CancellationToken cancellationToken)
   METHOD System.Threading.Tasks.Task<FinalFactory.Rendezvous.Client.RendezvousClientResult<FinalFactory.Rendezvous.Contracts.BrowseSessionsResponse>> BrowseAsync(FinalFactory.Rendezvous.Contracts.BrowseSessionsRequest request, System.Threading.CancellationToken cancellationToken)
   METHOD System.Threading.Tasks.Task<FinalFactory.Rendezvous.Client.RendezvousClientResult<FinalFactory.Rendezvous.Contracts.GetSessionResponse>> GetAsync(FinalFactory.Rendezvous.Contracts.SessionListingId listingId, FinalFactory.Rendezvous.Contracts.GameId gameId, FinalFactory.Rendezvous.Contracts.EnvironmentId environmentId, System.UInt32 protocolVersion, System.Threading.CancellationToken cancellationToken)
+  METHOD System.Collections.Generic.IAsyncEnumerable<FinalFactory.Rendezvous.Client.RendezvousClientResult<FinalFactory.Rendezvous.Contracts.SessionStreamEvent>> StreamAsync(FinalFactory.Rendezvous.Contracts.BrowseSessionsRequest request, System.String streamCursor, System.Threading.CancellationToken cancellationToken)
 TYPE FinalFactory.Rendezvous.Client.LeaseMaintenanceResult
   PROP FinalFactory.Rendezvous.Contracts.RendezvousErrorCode Error {get;}
   PROP FinalFactory.Rendezvous.Client.LeaseMaintenanceStopReason Reason {get;}
@@ -212,6 +213,7 @@ TYPE FinalFactory.Rendezvous.Client.RendezvousSessionBrowserClient
   METHOD System.Threading.Tasks.Task<FinalFactory.Rendezvous.Client.RendezvousClientResult<System.Collections.Generic.IReadOnlyList<FinalFactory.Rendezvous.Contracts.SessionListing>>> BrowseAllAsync(FinalFactory.Rendezvous.Contracts.BrowseSessionsRequest request, System.Int32 maximumPages, System.Threading.CancellationToken cancellationToken)
   METHOD System.Threading.Tasks.Task<FinalFactory.Rendezvous.Client.RendezvousClientResult<FinalFactory.Rendezvous.Contracts.BrowseSessionsResponse>> BrowseAsync(FinalFactory.Rendezvous.Contracts.BrowseSessionsRequest request, System.Threading.CancellationToken cancellationToken)
   METHOD System.Threading.Tasks.Task<FinalFactory.Rendezvous.Client.RendezvousClientResult<FinalFactory.Rendezvous.Contracts.GetSessionResponse>> GetAsync(FinalFactory.Rendezvous.Contracts.SessionListingId listingId, FinalFactory.Rendezvous.Contracts.GameId gameId, FinalFactory.Rendezvous.Contracts.EnvironmentId environmentId, System.UInt32 protocolVersion, System.Threading.CancellationToken cancellationToken)
+  METHOD System.Collections.Generic.IAsyncEnumerable<FinalFactory.Rendezvous.Client.RendezvousClientResult<FinalFactory.Rendezvous.Contracts.SessionStreamEvent>> StreamAsync(FinalFactory.Rendezvous.Contracts.BrowseSessionsRequest request, System.String streamCursor, System.Threading.CancellationToken cancellationToken)
 TYPE FinalFactory.Rendezvous.Client.SessionLeaseMaintainer
   EVENT System.EventHandler LeaseLost
   METHOD System.Threading.Tasks.ValueTask DisposeAsync()

tests/FinalFactory.Rendezvous.Tests/TestData/Contracts/v1/contracts-public-api.txt

@@ -28,6 +28,7 @@ TYPE FinalFactory.Rendezvous.Contracts.BrowseSessionsResponse
   PROP System.Int32 ContractVersion {get;set;}
   PROP System.Collections.Generic.List<FinalFactory.Rendezvous.Contracts.SessionListing> Items {get;set;}
   PROP System.String NextCursor {get;set;}
+  PROP System.String StreamCursor {get;set;}
 TYPE FinalFactory.Rendezvous.Contracts.ConnectionElapsedBucket
   ENUM UnderOneSecond=1
   ENUM OneToFiveSeconds=2
@@ -84,6 +85,7 @@ TYPE FinalFactory.Rendezvous.Contracts.ContractLimits
   FIELD System.Int32 OpaqueHttpCredentialMaxCharacters=1024
   FIELD System.Int32 RegionIdMaxCharacters=32
   FIELD System.Int32 SessionCapacityMaxPlayers=10000
+  FIELD System.Int32 SessionStreamEventMaxBytes=32768
   FIELD System.Int32 UdpCapabilityMaxCharacters=192
   FIELD System.Int32 UdpDatagramMaxBytes=1200
 TYPE FinalFactory.Rendezvous.Contracts.ContractValidation
@@ -345,6 +347,18 @@ TYPE FinalFactory.Rendezvous.Contracts.SessionListingId
   METHOD System.Boolean TryParse(System.String value, FinalFactory.Rendezvous.Contracts.SessionListingId& id)
   METHOD System.Boolean op_Equality(FinalFactory.Rendezvous.Contracts.SessionListingId left, FinalFactory.Rendezvous.Contracts.SessionListingId right)
   METHOD System.Boolean op_Inequality(FinalFactory.Rendezvous.Contracts.SessionListingId left, FinalFactory.Rendezvous.Contracts.SessionListingId right)
+TYPE FinalFactory.Rendezvous.Contracts.SessionStreamEvent
+  CTOR ()
+  PROP System.Int32 ContractVersion {get;set;}
+  PROP System.String Cursor {get;set;}
+  PROP FinalFactory.Rendezvous.Contracts.SessionStreamEventKind Kind {get;set;}
+  PROP System.Nullable<FinalFactory.Rendezvous.Contracts.SessionListingId> ListingId {get;set;}
+  PROP FinalFactory.Rendezvous.Contracts.SessionListing Session {get;set;}
+TYPE FinalFactory.Rendezvous.Contracts.SessionStreamEventKind
+  ENUM SessionUpsert=1
+  ENUM SessionRemove=2
+  ENUM Reset=3
+  ENUM Keepalive=4
 TYPE FinalFactory.Rendezvous.Contracts.UdpDecodeError
   ENUM None=0
   ENUM DatagramTooLarge=1
@@ -371,3 +385,6 @@ TYPE FinalFactory.Rendezvous.Contracts.UpdateSessionRequest
   PROP System.String DisplayName {get;set;}
   PROP System.String LeaseToken {get;set;}
   PROP System.Collections.Generic.Dictionary<System.String,System.String> Metadata {get;set;}
+  PROP System.Nullable<System.UInt32> ProtocolVersion {get;set;}
+  PROP System.Nullable<FinalFactory.Rendezvous.Contracts.RegionId> RegionId {get;set;}
+  PROP System.Nullable<FinalFactory.Rendezvous.Contracts.ListingVisibility> Visibility {get;set;}

tests/Observability/observability-assets.test.mjs

@@ -0,0 +1,89 @@
+import assert from "node:assert/strict";
+import { readFile } from "node:fs/promises";
+import test from "node:test";
+
+const root = new URL("../../", import.meta.url);
+const dashboardPath = new URL(
+  "deploy/observability/grafana/dashboards/rendezvous-overview.json",
+  root,
+);
+
+test("dashboard is provisionable, broad, and uses privacy-safe bounded series", async () => {
+  const dashboard = JSON.parse(await readFile(dashboardPath, "utf8"));
+  assert.equal(dashboard.uid, "rendezvous-overview");
+  assert.equal(dashboard.editable, false);
+  assert.ok(dashboard.panels.length >= 20);
+  assert.equal(new Set(dashboard.panels.map((panel) => panel.id)).size, dashboard.panels.length);
+  assert.equal(new Set(dashboard.panels.map((panel) => panel.title)).size, dashboard.panels.length);
+
+  const expressions = dashboard.panels
+    .flatMap((panel) => panel.targets ?? [])
+    .map((target) => target.expr ?? "")
+    .join("\n");
+  for (const metric of [
+    "rendezvous_http_requests_total",
+    "rendezvous_http_duration_milliseconds_bucket",
+    "rendezvous_udp_results_total",
+    "rendezvous_udp_received_bytes_total",
+    "rendezvous_limiter_drops_total",
+    "rendezvous_connection_outcomes_total",
+    "rendezvous_browser_sse_subscribers",
+    "rendezvous_store_active_listings",
+    "rendezvous_store_active_attempts",
+    "rendezvous_signing_keys",
+    "process_resident_memory_bytes",
+    "process_open_file_descriptors",
+    "dotnet_gc_heap_size_bytes",
+  ]) {
+    assert.match(expressions, new RegExp(`\\b${metric}\\b`));
+  }
+  assert.doesNotMatch(
+    expressions,
+    /listing_?id|session_?id|player|subject|token|capability|endpoint|address|metadata|credential/i,
+  );
+
+  for (const panel of dashboard.panels) {
+    assert.ok(panel.title?.trim());
+    assert.ok(panel.gridPos?.w > 0 && panel.gridPos?.h > 0);
+    for (const target of panel.targets ?? []) {
+      assert.equal(target.editorMode, "code");
+      assert.ok(target.expr?.trim());
+    }
+  }
+});
+
+test("Compose overlay pins hardened services and keeps telemetry private", async () => {
+  const compose = await readFile(new URL("deploy/observability/compose.yaml", root), "utf8");
+  assert.match(compose, /prom\/prometheus:v3\.13\.1@sha256:[a-f0-9]{64}/);
+  assert.match(compose, /grafana\/grafana:13\.1\.0@sha256:[a-f0-9]{64}/);
+  assert.match(compose, /Rendezvous__Metrics__Enabled: "true"/);
+  assert.match(compose, /rendezvous-metrics-token:\/run\/secrets\/rendezvous-metrics-token:ro/);
+  assert.match(compose, /GF_AUTH_ANONYMOUS_ENABLED: "false"/);
+  assert.match(compose, /GF_PLUGINS_PREINSTALL_DISABLED: "true"/);
+  assert.match(compose, /"127\.0\.0\.1:3000:3000\/tcp"/);
+  assert.doesNotMatch(compose, /9090:9090/);
+  assert.ok((compose.match(/read_only: true/g) ?? []).length >= 2);
+  assert.ok((compose.match(/no-new-privileges:true/g) ?? []).length >= 2);
+});
+
+test("Prometheus and Grafana provisioning use server-side authenticated access", async () => {
+  const prometheus = await readFile(
+    new URL("deploy/observability/prometheus/prometheus.yml", root),
+    "utf8",
+  );
+  const datasource = await readFile(
+    new URL("deploy/observability/grafana/provisioning/datasources/prometheus.yaml", root),
+    "utf8",
+  );
+  const provider = await readFile(
+    new URL("deploy/observability/grafana/provisioning/dashboards/rendezvous.yaml", root),
+    "utf8",
+  );
+  assert.match(prometheus, /bearer_token_file: \/run\/secrets\/rendezvous-metrics-token/);
+  assert.match(prometheus, /- rendezvous:8080/);
+  assert.match(datasource, /uid: rendezvous-prometheus/);
+  assert.match(datasource, /access: proxy/);
+  assert.match(datasource, /url: http:\/\/prometheus:9090/);
+  assert.match(provider, /allowUiUpdates: false/);
+  assert.match(provider, /path: \/var\/lib\/grafana\/dashboards/);
+});