Merge pull request 'R7: final stress run + tuning' (#38) from feature/r7-final-stress-tuning into development

CLAUDE.md

@@ -128,7 +128,7 @@ gateway/  ui/  pkg/              # added by their stages
 platform/telegram/               # Telegram connector side-service (Stage 9): bot + gRPC API
 loadtest/                        # module scrabble/loadtest: the pre-release stress harness (R2)
 backend/Dockerfile gateway/Dockerfile platform/telegram/Dockerfile loadtest/Dockerfile  # multi-stage distroless (Stage 16; loadtest R2); gateway/Dockerfile also has the `landing` target (R3)
-deploy/                          # docker-compose + caddy + landing + otelcol/prometheus/tempo/grafana (+ cAdvisor/postgres_exporter, R2)
+deploy/                          # docker-compose (per-service limits, R7) + caddy + landing + otelcol (OTLP + docker_stats per-container metrics) + prometheus/tempo/grafana + postgres_exporter
 ```
 
 ## Build & test

PRERELEASE.md

@@ -23,7 +23,7 @@ the edge before prod. Each phase maps back to the owner's raw pre-release TODO l
 | R4 | Push enrichment + kill the last poll | 4 + 5 | **done** |
 | R5 | Bundle slimming | 6 | **done** |
 | R6 | Refactor + docs reconciliation + de-staging | 7 | **done** |
-| R7 | Final stress run + tuning | 9b | todo |
+| R7 | Final stress run + tuning | 9b | **done** |
 | → | Stage 18 — prod contour deploy | — | see [`PLAN.md`](PLAN.md) |
 
 ## Key findings (these reshaped the raw list — read before starting a phase)
@@ -168,7 +168,7 @@ regression gate. Incorporates the early-run (R2) bug fixes not already shipped.
 - Open details: the structural-changes list itself (owner-approved before applying); the test
   consolidation targets.
 
-### R7 — Final stress run + tuning *(TODO 9, part 2)* — before Stage 18
+### R7 — Final stress run + tuning *(TODO 9, part 2)* — done
 Re-run the R2 harness against the final, refactored system on a clean contour; analyse
 resource consumption across **all** components (gateway, backend, Postgres, the
 metrics/observability stack, docker log volume) and agree the tuning (pool sizes, rate
@@ -380,3 +380,36 @@ Then Stage 18.
     10 files) into `backend/internal/inttest/helpers.go`; single-file helpers stay local. Pure relocation.
   - **No schema change → no contour DB wipe.** Regression gate: the full unit + integration + UI suites plus
     the R7 stress run.
+
+- **R7** (interview + implementation):
+  - **Locked decisions:** run the harness **same-host** (one-shot container on `scrabble-internal`, capped
+    `--cpus=3` so the contour keeps spare cores); **apply container limits + `GOMAXPROCS` now** (not just a
+    prod recommendation); **replace cAdvisor with the otelcol `docker_stats` receiver** (it resolved only the
+    root cgroup on this host); keep rate-limit / h2c knobs **compiled-in** (change values only if the data
+    demands — it did not).
+  - **Harness refinements (pre-run):** each virtual player builds its **own `edge.Client`** (its own h2c
+    connection for its Subscribe stream + Execute calls) instead of all players sharing one `http2.Transport` —
+    the R2 `transport_error` artifact; and `playTurn` now reports a **finished** game so the player drops it
+    from rotation. Effect, measured: `game.state` `transport_error` 14 % (R2) → **2.49 %**; `game_finished` on
+    chat ≈ 3 900 → **35**.
+  - **Observability:** added the `docker_stats` receiver to `otelcol` (`api_version: "1.44"` — the daemon's
+    minimum is 1.40; the receiver defaults to 1.25 and crash-looped until pinned), mounted the docker socket
+    read-only with `group_add` (the contrib image runs as UID 10001), dropped the cAdvisor service + its
+    Prometheus job, and retargeted the **Scrabble — Resources** dashboard to the docker_stats metric names
+    (`container_cpu_utilization`/100 == cores). Cross-checked against `docker stats` within sampling error.
+  - **Profile (final run, 500 players, limits in force):** the **gateway is the binding constraint** — with
+    one connection per player it bursts into its 2-core cap (the residual 2.49 % `transport_error`); backend
+    ~0.85 core and postgres ~1.4 cores had headroom; **tempo reached its 1 GiB cap**; the backend pool sat at
+    its `MaxOpenConns=25` cap (28 backends); docker logs were unbounded (~14 MiB / 30 min on the backend at
+    info). Full write-up in [`../loadtest/REPORT-R7.md`](../loadtest/REPORT-R7.md).
+  - **Round-2 tuning (owner-agreed, all in `deploy/docker-compose.yml`, no code change):** gateway **2 → 3
+    cores + `GOMAXPROCS=3`**; tempo memory **1 → 2 GiB**; backend `MAX_OPEN_CONNS` **25 → 40**; a json-file
+    **log-rotation** default (10m × 3) applied contour-wide via a YAML anchor (level stays info).
+    backend/postgres kept at 2 cores / 512 MiB (headroom is cheap on the shared host).
+  - **Validation:** the same gradual ramp on the tuned contour cut `game.state` `transport_error` to **0.72 %**
+    (gateway ~2 cores, now under the 3-core cap, no throttle; tempo ~1.27 GiB, under 2 GiB). A separate
+    **burst** run (a single 100 → 500 jump) pegged the gateway at 3 cores (≈296 % sustained, 9.27 % error),
+    confirming it is **connection-CPU-bound** — a true arrival spike is a **horizontal-scaling** lever, not
+    more cores per node (recorded in the prod-sizing recommendation).
+  - **No schema change → no contour DB wipe.** Bake-back: `loadtest/REPORT-R7.md` (new), `loadtest/README.md`,
+    `docs/TESTING.md`, the telemetry/observability section of `docs/ARCHITECTURE.md`, the repo-layout line in `CLAUDE.md`.

deploy/docker-compose.yml

@@ -23,11 +23,22 @@
 #     (network_mode: service:vpn); it answers internal gRPC at `telegram:9091`.
 name: scrabble
 
+# Bound every container's json-file logs. R7 measured the backend emitting a
+# per-request latency line at info (~14 MiB / 30 min under the 500-player stress
+# peak); without rotation the volume grows unbounded. 10 MiB x 3 files caps each
+# container at 30 MiB. Applied to every service via the *default-logging alias.
+x-logging: &default-logging
+  driver: json-file
+  options:
+    max-size: "10m"
+    max-file: "3"
+
 services:
   postgres:
     container_name: scrabble-postgres
     image: postgres:17-alpine
     restart: unless-stopped
+    logging: *default-logging
     environment:
       POSTGRES_DB: ${POSTGRES_DB:-scrabble}
       POSTGRES_USER: ${POSTGRES_USER:-scrabble}
@@ -39,6 +50,13 @@ services:
       retries: 30
     volumes:
       - postgres-data:/var/lib/postgresql/data
+    # R7 starting limits: 512M leaves headroom over the default 128 MB shared_buffers +
+    # per-connection memory (R2 peaked at 28 backends / 69 MiB RSS); tighten after the run.
+    deploy:
+      resources:
+        limits:
+          cpus: "2.0"
+          memory: 512M
     networks: [internal]
 
   backend:
@@ -50,12 +68,16 @@ services:
       args:
         DICT_VERSION: ${DICT_VERSION:-v1.0.0}
     restart: unless-stopped
+    logging: *default-logging
     depends_on:
       postgres:
         condition: service_healthy
     environment:
       # search_path=backend matches the migrations (00001 creates the schema).
       BACKEND_POSTGRES_DSN: postgres://${POSTGRES_USER:-scrabble}:${POSTGRES_PASSWORD}@postgres:5432/${POSTGRES_DB:-scrabble}?sslmode=disable&search_path=backend
+      # R7 tuned: the pool sat at its 25-conn cap (28 backends total) at 500 players;
+      # 40 gives headroom for bursts. Postgres (2 cores / 512 MiB) handles it.
+      BACKEND_POSTGRES_MAX_OPEN_CONNS: "40"
       BACKEND_HTTP_ADDR: ":8080"
       BACKEND_GRPC_ADDR: ":9090"
       BACKEND_CONNECTOR_ADDR: telegram:9091
@@ -65,8 +87,19 @@ services:
       BACKEND_OTEL_METRICS_EXPORTER: otlp
       OTEL_EXPORTER_OTLP_ENDPOINT: http://otelcol:4317
       OTEL_EXPORTER_OTLP_INSECURE: "true"
+      # GOMAXPROCS matches the CPU limit below so the Go scheduler aligns with the
+      # cgroup quota (the runtime otherwise sees all of the host's cores).
+      GOMAXPROCS: "2"
     # No container healthcheck: the distroless image has no shell/wget. Readiness
     # is covered by the CI post-deploy probe (GET / through caddy).
+    # R7 starting limits (generous over the R2 ~1-core / <=100 MiB peak); tightened to
+    # the agreed prod values after the final stress run. deploy.resources.limits is
+    # honoured by `docker compose up` (Compose v2), not only by swarm.
+    deploy:
+      resources:
+        limits:
+          cpus: "2.0"
+          memory: 512M
     networks: [internal]
 
   gateway:
@@ -84,6 +117,7 @@ services:
         VITE_GATEWAY_URL: ${VITE_GATEWAY_URL:-}
         VITE_APP_VERSION: ${APP_VERSION:-dev}
     restart: unless-stopped
+    logging: *default-logging
     depends_on: [backend]
     environment:
       GATEWAY_HTTP_ADDR: ":8081"
@@ -97,8 +131,18 @@ services:
       GATEWAY_OTEL_METRICS_EXPORTER: otlp
       OTEL_EXPORTER_OTLP_ENDPOINT: http://otelcol:4317
       OTEL_EXPORTER_OTLP_INSECURE: "true"
+      # GOMAXPROCS matches the CPU limit below (see backend).
+      GOMAXPROCS: "3"
       # GATEWAY_ADMIN_* intentionally unset: in the deployed contour the front
       # caddy owns the /_gm Basic-Auth and routes /_gm to the backend directly.
+    # R7 tuned: the gateway holds one h2c connection per player, so at 500 players it
+    # bursts into a 2-core cap (~2.49% transport_error on game.state); 3 cores absorbs
+    # the bursts. Per-connection overhead is the realistic prod cost — size for it.
+    deploy:
+      resources:
+        limits:
+          cpus: "3.0"
+          memory: 512M
     networks: [internal]
 
   # --- Landing (static) -------------------------------------------------------
@@ -121,6 +165,11 @@ services:
         VITE_GATEWAY_URL: ${VITE_GATEWAY_URL:-}
         VITE_APP_VERSION: ${APP_VERSION:-dev}
     restart: unless-stopped
+    logging: *default-logging
+    deploy:
+      resources:
+        limits:
+          memory: 128M
     networks: [internal]
 
   # --- Telegram connector (egress via the VPN sidecar) -----------------------
@@ -128,6 +177,7 @@ services:
     container_name: scrabble-telegram-vpn
     image: docker.iliadenisov.ru/developer/amneziawg-sidecar:latest
     restart: unless-stopped
+    logging: *default-logging
     privileged: true
     environment:
       AWG_CONF: ${AWG_CONF:?set AWG_CONF}
@@ -142,6 +192,7 @@ services:
       context: ..
       dockerfile: platform/telegram/Dockerfile
     restart: unless-stopped
+    logging: *default-logging
     depends_on: [vpn]
     network_mode: "service:vpn"
     environment:
@@ -167,6 +218,13 @@ services:
       TELEGRAM_OTEL_METRICS_EXPORTER: otlp
       OTEL_EXPORTER_OTLP_ENDPOINT: http://otelcol:4317
       OTEL_EXPORTER_OTLP_INSECURE: "true"
+      # The connector is light (the stress run does not drive Telegram); one P suffices.
+      GOMAXPROCS: "1"
+    deploy:
+      resources:
+        limits:
+          cpus: "1.0"
+          memory: 256M
 
   # --- Edge reverse proxy (single /_gm Basic-Auth; SPA + Connect -> gateway;
   #     the catch-all incl. the landing -> the static landing container) -------
@@ -174,6 +232,7 @@ services:
     container_name: scrabble-caddy
     image: caddy:2-alpine
     restart: unless-stopped
+    logging: *default-logging
     depends_on: [gateway, backend, grafana, landing]
     environment:
       # Test: ":80" (host caddy terminates TLS). Prod: a domain for own ACME.
@@ -183,6 +242,10 @@ services:
     volumes:
       - ${SCRABBLE_CONFIG_DIR:-.}/caddy/Caddyfile:/etc/caddy/Caddyfile:ro
       - caddy-data:/data
+    deploy:
+      resources:
+        limits:
+          memory: 128M
     networks:
       internal: {}
       edge:
@@ -193,37 +256,62 @@ services:
     container_name: scrabble-otelcol
     image: otel/opentelemetry-collector-contrib:0.119.0
     restart: unless-stopped
+    logging: *default-logging
     command: ["--config=/etc/otelcol/config.yaml"]
+    # The docker_stats receiver reads per-container metrics from the Docker API, so the
+    # collector (image UID 10001) joins the host's docker group to read the socket —
+    # DOCKER_GID defaults to the contour host's 989; set it for other hosts (prod). The
+    # socket is mounted read-only. This replaces cAdvisor, whose per-container metrics
+    # are empty on this host (separate-XFS /var/lib/docker).
+    group_add: ["${DOCKER_GID:-989}"]
     volumes:
       - ${SCRABBLE_CONFIG_DIR:-.}/otelcol/config.yaml:/etc/otelcol/config.yaml:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+    deploy:
+      resources:
+        limits:
+          memory: 512M
     networks: [internal]
 
   prometheus:
     container_name: scrabble-prometheus
     image: prom/prometheus:v2.55.1
     restart: unless-stopped
+    logging: *default-logging
     command:
       - --config.file=/etc/prometheus/prometheus.yml
       - --storage.tsdb.retention.time=15d
     volumes:
       - ${SCRABBLE_CONFIG_DIR:-.}/prometheus/prometheus.yml:/etc/prometheus/prometheus.yml:ro
       - prometheus-data:/prometheus
+    deploy:
+      resources:
+        limits:
+          memory: 512M
     networks: [internal]
 
   tempo:
     container_name: scrabble-tempo
     image: grafana/tempo:2.7.1
     restart: unless-stopped
+    logging: *default-logging
     command: ["-config.file=/etc/tempo/tempo.yaml"]
     volumes:
       - ${SCRABBLE_CONFIG_DIR:-.}/tempo/tempo.yaml:/etc/tempo/tempo.yaml:ro
       - tempo-data:/var/tempo
+    # R7 tuned: tempo reached the 1 GiB cap during the final run (446 MiB in R2);
+    # raised to 2 GiB for headroom against OOM under sustained tracing load.
+    deploy:
+      resources:
+        limits:
+          memory: 2G
     networks: [internal]
 
   grafana:
     container_name: scrabble-grafana
     image: grafana/grafana:11.4.0
     restart: unless-stopped
+    logging: *default-logging
     depends_on: [prometheus, tempo]
     environment:
       # Served under /_gm/grafana behind caddy's Basic-Auth; anonymous Admin so a
@@ -247,26 +335,10 @@ services:
       # provider logs "no such file or directory").
       - ${SCRABBLE_CONFIG_DIR:-.}/grafana/dashboards:/etc/grafana/dashboards:ro
       - grafana-data:/var/lib/grafana
-    networks: [internal]
-
-  # cAdvisor exports per-container resource metrics (CPU / memory / network / disk)
-  # for the R2/R7 stress runs' resource baseline. Prometheus scrapes it at :8080
-  # over the internal network. It needs read access to the host's cgroup and
-  # container state; --docker_only trims non-container cgroup series.
-  cadvisor:
-    container_name: scrabble-cadvisor
-    image: gcr.io/cadvisor/cadvisor:v0.49.1
-    restart: unless-stopped
-    privileged: true
-    command: ["--docker_only=true", "--housekeeping_interval=15s"]
-    devices:
-      - /dev/kmsg
-    volumes:
-      - /:/rootfs:ro
-      - /var/run:/var/run:ro
-      - /sys:/sys:ro
-      - /var/lib/docker/:/var/lib/docker:ro
-      - /dev/disk/:/dev/disk:ro
+    deploy:
+      resources:
+        limits:
+          memory: 512M
     networks: [internal]
 
   # postgres_exporter exports Postgres server metrics (connections, cache hit ratio,
@@ -276,9 +348,14 @@ services:
     container_name: scrabble-postgres-exporter
     image: prometheuscommunity/postgres-exporter:v0.16.0
     restart: unless-stopped
+    logging: *default-logging
     depends_on: [postgres]
     environment:
       DATA_SOURCE_NAME: postgresql://${POSTGRES_USER:-scrabble}:${POSTGRES_PASSWORD}@postgres:5432/${POSTGRES_DB:-scrabble}?sslmode=disable
+    deploy:
+      resources:
+        limits:
+          memory: 128M
     networks: [internal]
 
 networks:

deploy/grafana/dashboards/resources.json

@@ -4,7 +4,7 @@
   "tags": ["scrabble"],
   "timezone": "",
   "schemaVersion": 39,
-  "version": 1,
+  "version": 2,
   "refresh": "30s",
   "time": { "from": "now-1h", "to": "now" },
   "panels": [
@@ -43,30 +43,30 @@
     {
       "type": "timeseries",
       "title": "Container CPU (cores) by container",
-      "description": "cAdvisor container_cpu_usage_seconds_total rate, per scrabble-* container (the load harness appears when run as --name scrabble-loadtest). Verify the metric name against live Prometheus if empty.",
+      "description": "docker_stats container.cpu.utilization (a gauge where 100 == one core) / 100, per scrabble-* container; the load harness appears when run as --name scrabble-loadtest. Verify the scaling against live Prometheus.",
       "gridPos": { "h": 8, "w": 12, "x": 0, "y": 5 },
       "datasource": { "type": "prometheus", "uid": "prometheus" },
-      "targets": [{ "refId": "A", "expr": "sum(rate(container_cpu_usage_seconds_total{name=~\"scrabble-.+\"}[5m])) by (name)", "legendFormat": "{{name}}" }]
+      "targets": [{ "refId": "A", "expr": "max(container_cpu_utilization{container_name=~\"scrabble-.+\"}) by (container_name) / 100", "legendFormat": "{{container_name}}" }]
     },
     {
       "type": "timeseries",
-      "title": "Container memory (working set) by container",
-      "description": "cAdvisor container_memory_working_set_bytes, per scrabble-* container.",
+      "title": "Container memory (usage) by container",
+      "description": "docker_stats container.memory.usage.total bytes, per scrabble-* container.",
       "gridPos": { "h": 8, "w": 12, "x": 12, "y": 5 },
       "fieldConfig": { "defaults": { "unit": "bytes" }, "overrides": [] },
       "datasource": { "type": "prometheus", "uid": "prometheus" },
-      "targets": [{ "refId": "A", "expr": "max(container_memory_working_set_bytes{name=~\"scrabble-.+\"}) by (name)", "legendFormat": "{{name}}" }]
+      "targets": [{ "refId": "A", "expr": "max(container_memory_usage_total{container_name=~\"scrabble-.+\"}) by (container_name)", "legendFormat": "{{container_name}}" }]
     },
     {
       "type": "timeseries",
       "title": "Container network I/O by container",
-      "description": "cAdvisor receive (+) and transmit (-) byte rates per scrabble-* container.",
+      "description": "docker_stats receive (+) and transmit (-) byte rates per scrabble-* container (summed across interfaces).",
       "gridPos": { "h": 8, "w": 12, "x": 0, "y": 13 },
       "fieldConfig": { "defaults": { "unit": "Bps" }, "overrides": [] },
       "datasource": { "type": "prometheus", "uid": "prometheus" },
       "targets": [
-        { "refId": "A", "expr": "sum(rate(container_network_receive_bytes_total{name=~\"scrabble-.+\"}[5m])) by (name)", "legendFormat": "rx {{name}}" },
-        { "refId": "B", "expr": "-sum(rate(container_network_transmit_bytes_total{name=~\"scrabble-.+\"}[5m])) by (name)", "legendFormat": "tx {{name}}" }
+        { "refId": "A", "expr": "sum(rate(container_network_io_usage_rx_bytes{container_name=~\"scrabble-.+\"}[5m])) by (container_name)", "legendFormat": "rx {{container_name}}" },
+        { "refId": "B", "expr": "-sum(rate(container_network_io_usage_tx_bytes{container_name=~\"scrabble-.+\"}[5m])) by (container_name)", "legendFormat": "tx {{container_name}}" }
       ]
     },
     {

deploy/otelcol/config.yaml

@@ -6,6 +6,22 @@ receivers:
     protocols:
       grpc:
         endpoint: 0.0.0.0:4317
+  # Per-container resource metrics (CPU / memory / network) read straight from the
+  # Docker API. This replaces cAdvisor, which on the contour host resolves only the
+  # root cgroup (its /var/lib/docker is a separate XFS mount), and works the same in
+  # prod. The collector reaches the socket via group_add in docker-compose.yml.
+  # collection_interval matches Prometheus' 30s scrape. container.cpu.utilization is a
+  # gauge where 100 == one core (it mirrors `docker stats` CPU%).
+  docker_stats:
+    endpoint: unix:///var/run/docker.sock
+    # The receiver defaults to Docker API 1.25, but the daemon's minimum is 1.40
+    # (server speaks up to 1.54); pin a version both the receiver's client and the
+    # daemon accept, else the receiver fails to start ("client version too old").
+    api_version: "1.44"
+    collection_interval: 30s
+    metrics:
+      container.cpu.utilization:
+        enabled: true
 
 processors:
   batch: {}
@@ -33,6 +49,6 @@ service:
       processors: [batch]
       exporters: [otlp/tempo]
     metrics:
-      receivers: [otlp]
+      receivers: [otlp, docker_stats]
       processors: [batch]
       exporters: [prometheus]

deploy/prometheus/prometheus.yml

@@ -6,17 +6,14 @@ global:
   evaluation_interval: 30s
 
 scrape_configs:
+  # otelcol exposes both the services' OTLP metrics and the docker_stats receiver's
+  # per-container resource metrics (CPU/memory/network) on one endpoint.
   - job_name: otelcol
     static_configs:
       - targets: ["otelcol:9464"]
   - job_name: prometheus
     static_configs:
       - targets: ["localhost:9090"]
-  # Container resource metrics (CPU/memory/network/disk) for every contour
-  # container, for the R2/R7 stress runs' resource baseline.
-  - job_name: cadvisor
-    static_configs:
-      - targets: ["cadvisor:8080"]
   # Postgres server metrics (connections, cache hit ratio, transactions, db size).
   - job_name: postgres_exporter
     static_configs:

docs/ARCHITECTURE.md

@@ -561,11 +561,13 @@ promotions) is future work and would deliver short markdown messages (text + lin
   metrics + Tempo traces), **Prometheus** (15d), **Tempo** (72h) and **Grafana**
   (provisioned datasources + dashboards, behind the caddy `/_gm/grafana` Basic-Auth)
   are stood up with the deploy (`deploy/`); the default exporter stays
-  `none`, so CI needs no collector. The contour also runs **cAdvisor** (per-container
-  CPU/memory/network) and **postgres_exporter** (connections, cache-hit ratio,
-  transactions, db size), scraped by Prometheus and surfaced on the **Scrabble —
-  Resources** Grafana dashboard, which captures a resource
-  baseline; these export directly in Prometheus format (not through the collector).
+  `none`, so CI needs no collector. The collector also runs a **`docker_stats`**
+  receiver (per-container CPU/memory/network read from the Docker API and exported
+  through its Prometheus endpoint), and the contour runs **postgres_exporter**
+  (connections, cache-hit ratio, transactions, db size, scraped directly by Prometheus);
+  both are surfaced on the **Scrabble — Resources** Grafana dashboard, which captures the
+  stress-run resource profile. (`docker_stats` replaced cAdvisor, which on the contour
+  host resolved only the root cgroup — a separate-XFS `/var/lib/docker`.)
 - Per-request server-side timing via gin middleware from day one (the access log
   carries method, route, status, latency and the active trace id). A
   client-measured RTT piggybacked on the next request is a later enhancement.

docs/TESTING.md

@@ -127,8 +127,10 @@ tests or touching CI.
   selection, the report); the DAWG-backed move test runs under `BACKEND_DICT_DIR` (as the
   engine tests do). It is **not** part of the per-PR suite's behavioural assertions: it
   runs ad hoc as a one-shot container against the contour, producing a trip report (bugs
-  + a resource baseline) read off the **cAdvisor + postgres_exporter** Grafana dashboard
-  on the contour. See [`../loadtest/README.md`](../loadtest/README.md).
+  + a per-container resource profile) read off the **otelcol `docker_stats` +
+  postgres_exporter** Grafana dashboard on the contour. Two passes are recorded — the
+  early [`REPORT-R2.md`](../loadtest/REPORT-R2.md) and the final, tuned
+  [`REPORT-R7.md`](../loadtest/REPORT-R7.md). See [`../loadtest/README.md`](../loadtest/README.md).
 
 ## Principles
 

loadtest/README.md

@@ -36,17 +36,21 @@ container on the contour's docker network (this bypasses the host→gateway hair
 # from the repo root
 docker build -f loadtest/Dockerfile -t scrabble-loadtest .
 
-docker run --rm --name scrabble-loadtest --network scrabble-internal \
+docker run --rm --cpus=3 --name scrabble-loadtest --network scrabble-internal \
   -e POSTGRES_PASSWORD="$TEST_POSTGRES_PASSWORD" \
   scrabble-loadtest run
 ```
 
-Defaults assume the contour service names: `postgres:5432` and `gateway:8081`. The
-DAWGs are baked into the image (`/opt/dawg`, pinned to the dictionary release). Run with
+Each virtual player gets its own `edge.Client` (its own h2c connection), mirroring real
+clients rather than multiplexing every player over one transport. Defaults assume the
+contour service names: `postgres:5432` and `gateway:8081`. The DAWGs are baked into the
+image (`/opt/dawg`, pinned to the dictionary release). On a host shared with the contour,
+cap the harness (`--cpus=3`) so the contour keeps the spare cores. Run with
 `--name scrabble-loadtest` so the harness's own CPU/memory show up as a `scrabble-*`
-series in cAdvisor (keeping it separable from the system under test). Capture the
-resource baseline from the Grafana **Scrabble — Resources** dashboard
-(cAdvisor + postgres_exporter) while the run is in progress.
+series in the metrics (keeping it separable from the system under test). Capture the
+resource baseline from the Grafana **Scrabble — Resources** dashboard (the otelcol
+`docker_stats` receiver + postgres_exporter), or from `docker stats` directly, while the
+run is in progress.
 
 ## Commands & flags
 
@@ -80,15 +84,25 @@ DB wipe (`DROP SCHEMA backend CASCADE` + backend restart).
 ```sh
 go build ./loadtest/...
 go vet ./loadtest/...
-BACKEND_DICT_DIR=../scrabble-solver/dawg go test -count=1 ./loadtest/...
+BACKEND_DICT_DIR="$PWD/../scrabble-solver/dawg" go test -count=1 ./loadtest/...
 ```
 
 The DAWG-backed `moves` test runs only when `BACKEND_DICT_DIR` is set (as the engine
 tests use); the pure logic (hashing, board replay, rack build, move selection, report)
-runs unconditionally.
+runs unconditionally. Use an **absolute** path (here via `$PWD`): `go test ./loadtest/...`
+runs each package from its own directory, so a relative `BACKEND_DICT_DIR` would not
+resolve.
+
+## Trip reports
+
+The two stress passes are written up in the repo: the early pass in
+[`REPORT-R2.md`](REPORT-R2.md) and the final, tuned pass in
+[`REPORT-R7.md`](REPORT-R7.md).
 
 ## Caveat
 
-The harness shares the host CPU with the contour, so the early-pass resource baseline
-is read with the harness's own container series in mind; a cleaner number on separate
-hardware is future work. The moderate ramp keeps the generator from being the bottleneck.
+The harness shares the host CPU with the contour, so its own `scrabble-loadtest`
+container series is read alongside the system under test; capping it with `--cpus`
+keeps the contour's quota. Per-player transports (R7) removed the shared-transport
+artifact that inflated R2's `transport_error`, so the figures reflect the system. A
+fully isolated ceiling on separate hardware remains future work.

loadtest/REPORT-R7.md

@@ -0,0 +1,212 @@
+# R7 — final stress-run trip report
+
+The final pre-release stress pass for [`PRERELEASE.md`](../PRERELEASE.md) R7. It re-runs
+the R2 harness (`scrabble/loadtest`) against the **final, refactored system** on a
+freshly redeployed contour, to confirm the system holds at scale and to settle the
+resource sizing (container limits, `GOMAXPROCS`, pools, rate limits, log levels) before
+the Stage 18 prod cutover. Pass bar: **diagnostic + a tuning decision** — the run
+"passes" by completing cleanly; the per-container resource profile drives the tuning
+recorded below. Companion to the early pass, [`REPORT-R2.md`](REPORT-R2.md).
+
+## What changed since the R2 pass
+
+- **Harness — per-player transports.** Each virtual player now owns its `edge.Client`
+  (its own `http2.Transport` / h2c connection carrying both its `Subscribe` stream and
+  its `Execute` calls), instead of all players multiplexing over one shared transport.
+  R2 traced the ~14 % `transport_error` on `game.state` at 500 players to that single
+  shared connection's stream limit; per-player connections mirror real clients and
+  remove the artifact, so this pass measures the system, not the harness.
+- **Harness — drop finished games.** `playTurn` reports a finished game and the player
+  drops it from its rotation, so secondary ops stop hitting `game_finished` on ended
+  games (the other R2 harness finding).
+- **Observability — otelcol `docker_stats`.** cAdvisor (which resolves only the root
+  cgroup on this host — separate-XFS `/var/lib/docker`) is replaced by the otelcol
+  `docker_stats` receiver, reading per-container CPU/memory/network from the Docker API.
+  Per-container panels now populate on the contour host. (`api_version` pinned to 1.44;
+  the daemon's minimum is 1.40.)
+- **Contour — container limits + `GOMAXPROCS`.** `deploy.resources.limits` now bound
+  every service; the Go services pin `GOMAXPROCS` to their CPU limit so the runtime
+  matches the cgroup quota. Starting values were generous over the R2 peak; this pass
+  validates them and settles the agreed sizing (below).
+
+## Method
+
+Unchanged from R2 except for the per-player transports and the dropped-finished-games
+refinement above:
+
+- **Driver:** the `scrabble/loadtest` module, run as a one-shot container on the
+  `scrabble-internal` docker network (reaching `postgres:5432` / `gateway:8081`
+  directly), capped at `--cpus 3` so the contour keeps the host's spare cores.
+- **Seed:** 10 000 durable + 1 000 guest accounts with pre-created sessions written
+  straight to Postgres (token hash matches `backend/internal/session`).
+- **Games:** assembled through the real **invitation** flow, 2–4 players each, no
+  robots; variants over scrabble_en / scrabble_ru / erudit_ru.
+- **Play:** each player holds a live `Subscribe` stream and, per tick, polls
+  `game.state`, replays `game.history` and submits a **mid-ranked** legal move generated
+  locally by the embedded `scrabble-solver`, or passes / exchanges; a fraction exercise
+  nudge / chat / check-word / draft / profile / stats. A separate **gateway-hammer**
+  floods `games.list` from one account.
+- **Scale:** the same moderate ramp **50 → 200 → 500** concurrent players, 10 min/step.
+- **Resource capture:** `docker stats` (docker API) sampled every ~20 s for per-container
+  CPU/memory; the otelcol **`docker_stats`** receiver → Prometheus → the Grafana
+  **Scrabble — Resources** dashboard for the same per-container series; `postgres_exporter`
+  internals and per-service Go runtime metrics.
+
+## Run configuration
+
+```
+docker run --rm --cpus=3 --name scrabble-loadtest --network scrabble-internal \
+  -e POSTGRES_PASSWORD=… scrabble-loadtest \
+  run --durable 10000 --guest 1000 --steps 50,200,500 --step-dur 10m \
+      --tick 800ms --hammer-workers 20 --hammer-dur 15s --reset --cleanup
+```
+
+Date: 2026-06-10. Contour: the R1-baseline schema, freshly redeployed with the R7
+container limits / `GOMAXPROCS` (backend/gateway/postgres capped at 2 cores + 512 MiB,
+`GOMAXPROCS=2`) and the `docker_stats` observability. Seeded population removed by
+`--cleanup` afterwards.
+
+## Findings
+
+The ramp ran clean to 500 players — no harness crash, no deadlock, `stream errors: 0` —
+and cleanup removed all 11 000 seeded accounts.
+
+- **Volume (1827 s):** 821 680 edge calls (449.7 req/s incl. the hammer). Real gameplay
+  at scale: **50 916 committed plays**, 4 817 passes, 2 931 games finished; 165 755
+  `opponent_moved` + 54 864 `your_turn` events.
+- **The per-player transport fix worked.** `game.state` returned `transport_error` on
+  **3 173 / 127 403 = 2.49 %** of calls — down from R2's ~14 % on the same step. Other
+  ops were lower still (`game.history` 0.43 %, `game.submit_play` 0.28 %). The residual
+  is the gateway bursting into its 2-core cap (see the profile below), not the harness.
+- **Dropping finished games worked.** `game_finished` on `chat.nudge` / `chat.post` fell
+  to **35 / 36** (R2: ≈ 3 900 each) — secondary ops no longer hammer ended games.
+- **The limiter holds.** The gateway-hammer sent 565 152 `games.list`; **564 979
+  (99.97 %) were `rate_limited`** (154 ok burst, 19 deadline), p99 = 2 ms, ~309 req/s of
+  rejections sustained — unchanged from R2.
+- **Latency (peak):** `game.state` p50 ≈ 100 ms, p99 in the 2000 ms bucket (max 2549 ms);
+  `game.submit_play` p50 100 / p99 1000 ms bucket. Lobby ops stayed fast
+  (invitation / games.list p99 ≤ 10 ms). The p99 tail correlates with the gateway
+  burst-throttling, not the backend (which stayed at ~0.85 core).
+
+## Resource profile
+
+Per-container peak during step 3 (500 players), with the R7 starting limits in force
+(backend/gateway/postgres capped at 2 cores / 512 MiB). Two CPU columns: `docker stats`
+samples a ~1 s window (catches bursts); the otelcol `docker_stats` receiver averages over
+its 30 s collection interval (smooths them) — they agree within sampling error, which
+validates the new observability path.
+
+| container | CPU burst (1 s) | CPU sustained (30 s) | CPU cap | mem peak | mem cap |
+|-----------|----------------:|---------------------:|--------:|---------:|--------:|
+| scrabble-gateway | **217 %** (at cap) | ~145 % | 200 % | 167 MiB | 512 MiB |
+| scrabble-postgres | 138 % | ~153 % | 200 % | 117 MiB | 512 MiB |
+| scrabble-backend | 85 % | ~89 % | 200 % | 116 MiB | 512 MiB |
+| scrabble-tempo | 33 % | — | (none) | **1024 MiB** (at cap) | 1024 MiB |
+| scrabble-otelcol | 11 % | — | (none) | 131 MiB | 512 MiB |
+| scrabble-loadtest (harness) | 157 % | — | 300 % | 369 MiB | — |
+
+- **The gateway is the binding constraint.** With one h2c connection per player it draws
+  ~1.45 cores sustained and **bursts to its 2-core cap** at 500 players, throttling
+  briefly — the source of the 2.49 % `transport_error`. R2 saw only ~0.93 core because
+  all 500 players shared one connection; the +~0.5 core is the realistic per-connection
+  overhead (500 separate HTTP/2 connections). This is a sizing fact, not a regression.
+- **backend is over-provisioned** (~0.85 core vs a 2-core cap); **postgres** (~1.4 cores)
+  has headroom; both stayed ≤ 120 MiB.
+- **tempo reached its 1 GiB memory cap** (R2: 446 MiB) — an OOM risk under sustained
+  tracing.
+- **Postgres backends peaked at 28**, with the backend pool at its `MaxOpenConns=25` cap.
+  Cache hit stayed ~100 % (no disk reads); CPU, not I/O, is the limit.
+- **docker log volume (30 min):** backend 14.2 MiB, gateway 4.6 MiB, postgres 0.04 MiB —
+  the backend's per-request latency line at info dominates, and json-file logs had no
+  rotation.
+
+## Tuning applied
+
+Agreed from the profile (all in `deploy/docker-compose.yml`; no code change — the pool
+is already env-driven):
+
+| knob | from | to | why |
+|------|------|----|-----|
+| gateway CPU + `GOMAXPROCS` | 2 cores / 2 | **3 cores / 3** | it bursts into the 2-core cap at 500 players (the 2.49 % `transport_error`); 3 absorbs the bursts |
+| tempo memory | 1 GiB | **2 GiB** | it reached the 1 GiB cap (OOM risk) |
+| backend `MAX_OPEN_CONNS` | 25 | **40** | the pool sat at its 25-conn cap at peak; headroom trims the p99 tail |
+| docker logs | unbounded | **json-file 10m × 3** | bound the ~14 MiB / 30 min backend log; level stays `info` |
+
+Left as-is: backend / postgres at 2 cores / 512 MiB (peak ~0.85 / ~1.4 cores — headroom
+is cheap on the shared host); the per-user rate limiter and `h2cMaxConcurrentStreams=250`
+(per-connection now, ~1 stream each — ample) and cache TTLs (no pressure observed).
+
+### Validation re-run
+
+Re-running the **same gradual ramp** (50 → 200 → 500) on the tuned contour confirms the
+fix:
+
+- **`game.state` `transport_error` fell to 0.72 %** (853 / 119 051), down from 2.49 % at
+  2 cores. The latency tail also improved — p99 in the 1000 ms bucket, max 1220 ms (was
+  the 2000 ms bucket, max 2549 ms).
+- The **gateway peaked at ~2 cores** (≈196 % on the 30 s gauge) — now comfortably **under
+  the 3-core cap**, so it no longer throttles. backend ~1 core, postgres ~1.3 cores.
+- **tempo peaked at ~1.27 GiB** — under the new 2 GiB cap (it would have OOM-ed at 1 GiB).
+- Drop-finished still holds (`game_finished` on chat 41/42); the limiter still rejects
+  99.97 % of the hammer at p99 2 ms; `stream errors: 0`.
+
+A separate **burst stress** (a single 100 → 500 jump — 400 players connecting at once)
+**pegged the gateway at 3 cores** (≈296 % sustained) and pushed `game.state`
+`transport_error` to 9.27 %. The gateway is **connection-CPU-bound and bursty**: average
+load is ~1 core, but a mass-simultaneous connection storm saturates whatever single-node
+cap it is given. Real arrivals are gradual (the canonical run), where 3 cores has
+headroom; the lever for a true arrival spike is **horizontal scaling**, not more cores per
+node — carried into the prod recommendation below.
+
+## Prod-sizing recommendation (Stage 18)
+
+The contour is **CPU-bound and gateway-led** at 500 concurrent players. Carry these to the
+prod contour env (the same compose, `PROD_*` values):
+
+- **gateway: ≥ 3 cores** per ~500 concurrent players, `GOMAXPROCS` pinned to the limit —
+  it scales with the **connection count**, not just the request rate; beyond one node's
+  worth, scale the gateway **horizontally** rather than vertically.
+- **backend: ~1–2 cores**, pool 40 — comfortable; the work is light per request.
+- **postgres: ~2 cores / ≥ 512 MiB** — ~1.4 cores at 500 players, 100 % cache hit.
+- **tempo: ≥ 2 GiB**; the Go services run under ~170 MiB (256 MiB would suffice, 512 is
+  safe); pin `GOMAXPROCS` to each CPU limit; keep json-file rotation.
+- Memory is not the constraint anywhere; CPU is.
+
+### VPS / VDS sizing (single-host contour)
+
+The whole contour (the app + the observability stack) runs on one host via
+`docker-compose`. The tiers below are grounded in the R7 profile (**≈5.5 cores / ≈2.5 GiB
+RAM peak at 500 concurrent players**; ≈0.5 GiB idle) and the **measured** on-disk
+footprint: prod images ≈2.4 GB; the Tempo volume **3.1 GB at 72 h** retention; Prometheus
+≈1–2 GB at 15 d; the game DB 23 MiB and growing with history. CPU and disk grow; RAM has
+the most slack.
+
+| tier | CPU | RAM | disk | handles |
+|------|-----|-----|------|---------|
+| **Minimum** | 2 cores | 2 GiB | 20 GiB | ~up to ~150 concurrent; lower the compose limits (gateway 1.5 / backend·postgres 1 / tempo 1 GiB) to fit the box |
+| **Average** (reasonable load) | 4 cores | 4 GiB | 40 GiB | ~300–400 concurrent comfortably; the tested 500 with occasional gateway burst-throttling |
+| **Maximum** (worry-free) | 8 cores | 8 GiB | 80 GiB | 500+ concurrent with full gateway burst headroom (its 3-core cap) + room to grow; the compose limits fit as-is |
+
+- The per-service limits in `docker-compose.yml` are tuned for the **Average/Maximum**
+  target (the gateway alone caps at 3 cores). On the **Minimum** tier, scale them down to
+  match the host or the caps over-subscribe it.
+- **Disk is dominated by observability retention + DB growth.** Tempo (72 h traces) and
+  Prometheus (15 d metrics) are the main levers — shorten the windows (or move Tempo to
+  object storage) to cut disk; Postgres grows with game history, so budget for months of
+  it; container logs are already capped (json-file 10m × 3 ≈ 30 MiB each).
+- **RAM** rarely binds: the contour peaks ≈2.5 GiB at 500 players and the sum of all
+  configured limits is ≈5.6 GiB, so 8 GiB never strains.
+- Beyond one host's worth of players, scale the **gateway horizontally** (it is
+  connection-CPU-bound) rather than ordering an ever-bigger box.
+
+## Re-running
+
+See [`README.md`](README.md). Briefly, from the repo root:
+
+```sh
+docker build -f loadtest/Dockerfile -t scrabble-loadtest .
+docker run --rm --cpus=3 --name scrabble-loadtest --network scrabble-internal \
+  -e POSTGRES_PASSWORD=… scrabble-loadtest run --reset --cleanup
+```
+
+The harness stays in the repo for future repeats.

loadtest/cmd/loadtest/main.go

@@ -24,7 +24,6 @@ import (
 	"syscall"
 	"time"
 
-	"scrabble/loadtest/internal/edge"
 	"scrabble/loadtest/internal/moves"
 	"scrabble/loadtest/internal/report"
 	"scrabble/loadtest/internal/scenario"
@@ -114,7 +113,7 @@ func cmdRun(ctx context.Context, log *slog.Logger, args []string) error {
 	log.Info("seeded", "durable", len(pool.Durables), "guest", len(pool.Guests))
 
 	rec := report.New()
-	drv := scenario.NewDriver(edge.New(*gateway), reg, rec, log)
+	drv := scenario.NewDriver(*gateway, reg, rec, log)
 	cfg := scenario.RealisticConfig{
 		Steps: steps, StepDur: *stepDur, GamesPerPlayer: *gpp,
 		Tick: *tick, SecondaryProb: *secProb,

loadtest/internal/edge/client.go

@@ -41,16 +41,18 @@ const (
 	msgEnqueue    = "lobby.enqueue"
 )
 
-// Client speaks the edge protocol to a single gateway base URL over h2c. It is safe
-// for concurrent use by many virtual players (the underlying http2.Transport pools
-// and multiplexes connections).
+// Client speaks the edge protocol to a single gateway base URL over h2c. The harness
+// builds one Client per virtual player, so each player owns its h2c connection (its
+// Subscribe stream and Execute calls share it) the way a real client does; a single
+// Client is safe for that player's own concurrent goroutines.
 type Client struct {
 	rpc edgev1connect.GatewayClient
 }
 
 // New builds a Client for baseURL (for example http://gateway:8081). The transport
 // speaks HTTP/2 cleartext (h2c) to match the gateway, dialling plaintext TCP rather
-// than TLS.
+// than TLS. Each virtual player gets its own Client (hence its own connection), so the
+// load mirrors real clients instead of multiplexing every player over one transport.
 func New(baseURL string) *Client {
 	hc := &http.Client{
 		Transport: &http2.Transport{

loadtest/internal/scenario/assemble.go

@@ -37,6 +37,7 @@ func (d *Driver) assembleCohort(ctx context.Context, cohort []seed.Account, game
 	if len(cohort) < 2 {
 		return nil
 	}
+	c := edge.New(d.gateway) // one client for the assembly burst; players play on their own
 	gamesOf := make(map[string]int, len(cohort))
 	var games []*Game
 	for i := range cohort {
@@ -51,7 +52,7 @@ func (d *Driver) assembleCohort(ctx context.Context, cohort []seed.Account, game
 				break
 			}
 			variant := moves.Variants()[rng.Intn(len(moves.Variants()))]
-			g, err := d.assemble(ctx, members, variant)
+			g, err := d.assemble(ctx, c, members, variant)
 			if err != nil {
 				d.log.Debug("assemble game", "err", err)
 				break
@@ -85,7 +86,7 @@ func pickMembers(cohort []seed.Account, inviter seed.Account, rng *rand.Rand) []
 // assemble runs the invitation flow for one game: the inviter (members[0]) invites
 // the rest, each invitee accepts the pending invitation, and the completing accept
 // starts the game, which is then located in the inviter's game list.
-func (d *Driver) assemble(ctx context.Context, members []seed.Account, variant string) (*Game, error) {
+func (d *Driver) assemble(ctx context.Context, c *edge.Client, members []seed.Account, variant string) (*Game, error) {
 	inviter := members[0]
 	inviteeIDs := make([]string, len(members)-1)
 	for i, m := range members[1:] {
@@ -93,7 +94,7 @@ func (d *Driver) assemble(ctx context.Context, members []seed.Account, variant s
 	}
 
 	t0 := time.Now()
-	code, err := d.edge.CreateInvitation(ctx, inviter.Token, inviteeIDs, variant)
+	code, err := c.CreateInvitation(ctx, inviter.Token, inviteeIDs, variant)
 	d.rec.Record("invitation.create", code, time.Since(t0))
 	if err != nil || code != "ok" {
 		return nil, fmt.Errorf("invitation.create: %s", code)
@@ -101,7 +102,7 @@ func (d *Driver) assemble(ctx context.Context, members []seed.Account, variant s
 
 	for _, invitee := range members[1:] {
 		t0 = time.Now()
-		list, lc, err := d.edge.ListInvitations(ctx, invitee.Token)
+		list, lc, err := c.ListInvitations(ctx, invitee.Token)
 		d.rec.Record("invitation.list", lc, time.Since(t0))
 		if err != nil || lc != "ok" {
 			return nil, fmt.Errorf("invitation.list: %s", lc)
@@ -111,7 +112,7 @@ func (d *Driver) assemble(ctx context.Context, members []seed.Account, variant s
 			return nil, fmt.Errorf("no pending invitation from %s", inviter.ID)
 		}
 		t0 = time.Now()
-		ac, err := d.edge.AcceptInvitation(ctx, invitee.Token, invID)
+		ac, err := c.AcceptInvitation(ctx, invitee.Token, invID)
 		d.rec.Record("invitation.accept", ac, time.Since(t0))
 		if err != nil || ac != "ok" {
 			return nil, fmt.Errorf("invitation.accept: %s", ac)
@@ -119,7 +120,7 @@ func (d *Driver) assemble(ctx context.Context, members []seed.Account, variant s
 	}
 
 	t0 = time.Now()
-	games, gc, err := d.edge.GamesList(ctx, inviter.Token)
+	games, gc, err := c.GamesList(ctx, inviter.Token)
 	d.rec.Record("games.list", gc, time.Since(t0))
 	if err != nil || gc != "ok" {
 		return nil, fmt.Errorf("games.list: %s", gc)

loadtest/internal/scenario/hammer.go

@@ -5,6 +5,7 @@ import (
 	"sync"
 	"time"
 
+	"scrabble/loadtest/internal/edge"
 	"scrabble/loadtest/internal/seed"
 )
 
@@ -29,6 +30,7 @@ func (d *Driver) Hammer(ctx context.Context, acc seed.Account, cfg HammerConfig)
 	runCtx, cancel := context.WithTimeout(ctx, cfg.Duration)
 	defer cancel()
 	d.log.Info("gateway-hammer", "workers", cfg.Workers, "duration", cfg.Duration)
+	c := edge.New(d.gateway)
 	var wg sync.WaitGroup
 	for w := 0; w < cfg.Workers; w++ {
 		wg.Add(1)
@@ -36,7 +38,7 @@ func (d *Driver) Hammer(ctx context.Context, acc seed.Account, cfg HammerConfig)
 			defer wg.Done()
 			for runCtx.Err() == nil {
 				t0 := time.Now()
-				_, code, _ := d.edge.GamesList(runCtx, acc.Token)
+				_, code, _ := c.GamesList(runCtx, acc.Token)
 				d.rec.Record("hammer:games.list", code, time.Since(t0))
 			}
 		}()

loadtest/internal/scenario/scenario.go

@@ -9,6 +9,7 @@ import (
 	"context"
 	"log/slog"
 	"math/rand"
+	"slices"
 	"sync"
 	"time"
 
@@ -18,18 +19,20 @@ import (
 	"scrabble/loadtest/internal/seed"
 )
 
-// Driver ties the edge client, the local move generator and the run recorder
-// together. All three are safe for concurrent use by many player goroutines.
+// Driver ties the gateway endpoint, the local move generator and the run recorder
+// together. It builds one edge client per virtual player, so each player owns its
+// h2c connection (its Subscribe stream and Execute calls share it) the way a real
+// client does, rather than multiplexing every player over a single shared transport.
 type Driver struct {
-	edge  *edge.Client
-	moves *moves.Registry
-	rec   *report.Recorder
-	log   *slog.Logger
+	gateway string // gateway base URL, e.g. http://gateway:8081
+	moves   *moves.Registry
+	rec     *report.Recorder
+	log     *slog.Logger
 }
 
-// NewDriver builds a Driver.
-func NewDriver(c *edge.Client, m *moves.Registry, rec *report.Recorder, log *slog.Logger) *Driver {
-	return &Driver{edge: c, moves: m, rec: rec, log: log}
+// NewDriver builds a Driver targeting the gateway base URL.
+func NewDriver(gateway string, m *moves.Registry, rec *report.Recorder, log *slog.Logger) *Driver {
+	return &Driver{gateway: gateway, moves: m, rec: rec, log: log}
 }
 
 // RealisticConfig parameterises the under-the-limit ramp.
@@ -98,11 +101,16 @@ func (d *Driver) RunRealistic(ctx context.Context, pool *seed.Pool, cfg Realisti
 	return nil
 }
 
-// playerLoop runs one virtual player: a live-event subscription (loads the push hub,
-// counts events) plus a round-robin turn loop over the player's games.
+// playerLoop runs one virtual player over its own edge client (its own h2c
+// connection): a live-event subscription (loads the push hub, counts events) plus a
+// round-robin turn loop over the player's games. A game that has finished is dropped
+// from the rotation so secondary ops stop hitting an ended game; once no active game
+// remains the player idles, still holding its stream, until the run ends.
 func (d *Driver) playerLoop(ctx context.Context, p seed.Account, games []*Game, cfg RealisticConfig, rng *rand.Rand) {
-	go d.subscribeLoop(ctx, p)
-	if len(games) == 0 {
+	c := edge.New(d.gateway)
+	go d.subscribeLoop(ctx, c, p)
+	active := games
+	if len(active) == 0 {
 		<-ctx.Done()
 		return
 	}
@@ -114,22 +122,30 @@ func (d *Driver) playerLoop(ctx context.Context, p seed.Account, games []*Game,
 		case <-ctx.Done():
 			return
 		case <-ticker.C:
-			g := games[gi%len(games)]
+			g := active[gi%len(active)]
 			gi++
 			if rng.Float64() < cfg.SecondaryProb {
-				d.secondaryOp(ctx, p, g, rng)
+				d.secondaryOp(ctx, c, p, g, rng)
 				continue
 			}
-			d.playTurn(ctx, p, g, rng)
+			if d.playTurn(ctx, c, p, g, rng) {
+				active = slices.DeleteFunc(active, func(x *Game) bool { return x == g })
+				gi = 0
+				if len(active) == 0 {
+					<-ctx.Done()
+					return
+				}
+			}
 		}
 	}
 }
 
-// subscribeLoop holds the player's live-event stream open, counting events and
-// reconnecting with a brief backoff after a drop, until the run ends.
-func (d *Driver) subscribeLoop(ctx context.Context, p seed.Account) {
+// subscribeLoop holds the player's live-event stream open on the player's client,
+// counting events and reconnecting with a brief backoff after a drop, until the run
+// ends.
+func (d *Driver) subscribeLoop(ctx context.Context, c *edge.Client, p seed.Account) {
 	for ctx.Err() == nil {
-		err := d.edge.Subscribe(ctx, p.Token, func(e edge.Event) { d.rec.Event(e.Kind) })
+		err := c.Subscribe(ctx, p.Token, func(e edge.Event) { d.rec.Event(e.Kind) })
 		if ctx.Err() != nil {
 			return
 		}
@@ -144,80 +160,90 @@ func (d *Driver) subscribeLoop(ctx context.Context, p seed.Account) {
 	}
 }
 
-// playTurn plays one turn in g when it is the player's move: fetch state, replay
-// history, pick a legal move and submit it (or exchange / pass).
-func (d *Driver) playTurn(ctx context.Context, p seed.Account, g *Game, rng *rand.Rand) {
+// playTurn plays one turn in g over the player's client when it is the player's
+// move: fetch state, replay history, pick a legal move and submit it (or exchange /
+// pass). It reports whether the game has finished, so the caller can drop it from the
+// rotation.
+func (d *Driver) playTurn(ctx context.Context, c *edge.Client, p seed.Account, g *Game, rng *rand.Rand) (finished bool) {
 	seat := g.seatOf(p.ID.String())
 	if seat < 0 {
-		return
+		return false
 	}
 	t0 := time.Now()
-	st, code, err := d.edge.State(ctx, p.Token, g.ID)
+	st, code, err := c.State(ctx, p.Token, g.ID)
 	d.rec.Record("game.state", code, time.Since(t0))
-	if err != nil || code != "ok" || !st.Game.Active() || st.Game.ToMove != seat {
-		return
+	if err != nil || code != "ok" {
+		return false
+	}
+	if !st.Game.Active() {
+		return true
+	}
+	if st.Game.ToMove != seat {
+		return false
 	}
 
 	t0 = time.Now()
-	hist, hc, err := d.edge.History(ctx, p.Token, g.ID)
+	hist, hc, err := c.History(ctx, p.Token, g.ID)
 	d.rec.Record("game.history", hc, time.Since(t0))
 	if err != nil || hc != "ok" {
-		return
+		return false
 	}
 
 	action, err := d.moves.Pick(g.Variant, hist, st.Rack, st.BagLen, rng)
 	if err != nil {
 		d.log.Debug("pick move", "variant", g.Variant, "err", err)
-		return
+		return false
 	}
 	switch action.Kind {
 	case "play":
 		t0 = time.Now()
-		_, c, _ := d.edge.SubmitPlay(ctx, p.Token, g.ID, action.Dir, action.Tiles)
-		d.rec.Record("game.submit_play", c, time.Since(t0))
+		_, code, _ := c.SubmitPlay(ctx, p.Token, g.ID, action.Dir, action.Tiles)
+		d.rec.Record("game.submit_play", code, time.Since(t0))
 	case "exchange":
 		t0 = time.Now()
-		_, c, _ := d.edge.Exchange(ctx, p.Token, g.ID, action.Exchange)
-		d.rec.Record("game.exchange", c, time.Since(t0))
+		_, code, _ := c.Exchange(ctx, p.Token, g.ID, action.Exchange)
+		d.rec.Record("game.exchange", code, time.Since(t0))
 	default:
 		t0 = time.Now()
-		_, c, _ := d.edge.Pass(ctx, p.Token, g.ID)
-		d.rec.Record("game.pass", c, time.Since(t0))
+		_, code, _ := c.Pass(ctx, p.Token, g.ID)
+		d.rec.Record("game.pass", code, time.Since(t0))
 	}
+	return false
 }
 
 // secondaryOp exercises one of the non-move edge operations the plan calls out, so
-// the run touches nudge / chat / check-word / draft / profile / stats too.
-func (d *Driver) secondaryOp(ctx context.Context, p seed.Account, g *Game, rng *rand.Rand) {
+// the run touches nudge / chat / check-word / draft / profile / stats too, over the
+// player's own client.
+func (d *Driver) secondaryOp(ctx context.Context, c *edge.Client, p seed.Account, g *Game, rng *rand.Rand) {
 	t0 := time.Now()
 	switch rng.Intn(7) {
 	case 0:
-		c, _ := d.edge.Nudge(ctx, p.Token, g.ID)
-		d.rec.Record("chat.nudge", c, time.Since(t0))
+		code, _ := c.Nudge(ctx, p.Token, g.ID)
+		d.rec.Record("chat.nudge", code, time.Since(t0))
 	case 1:
-		c, _ := d.edge.ChatPost(ctx, p.Token, g.ID, "gg")
-		d.rec.Record("chat.post", c, time.Since(t0))
+		code, _ := c.ChatPost(ctx, p.Token, g.ID, "gg")
+		d.rec.Record("chat.post", code, time.Since(t0))
 	case 2:
-		c, _ := d.edge.CheckWord(ctx, p.Token, g.ID, []byte{0, 1, 2})
-		d.rec.Record("game.check_word", c, time.Since(t0))
+		code, _ := c.CheckWord(ctx, p.Token, g.ID, []byte{0, 1, 2})
+		d.rec.Record("game.check_word", code, time.Since(t0))
 	case 3:
 		// rack_order is an opaque string and board_tiles a (here empty) array, per the
 		// backend draft DTO; a malformed shape is rejected as bad_request.
-		c, _ := d.edge.DraftSave(ctx, p.Token, g.ID, `{"rack_order":"","board_tiles":[]}`)
-		d.rec.Record("draft.save", c, time.Since(t0))
+		code, _ := c.DraftSave(ctx, p.Token, g.ID, `{"rack_order":"","board_tiles":[]}`)
+		d.rec.Record("draft.save", code, time.Since(t0))
 	case 4:
-		c, _ := d.edge.DraftGet(ctx, p.Token, g.ID)
-		d.rec.Record("draft.get", c, time.Since(t0))
+		code, _ := c.DraftGet(ctx, p.Token, g.ID)
+		d.rec.Record("draft.get", code, time.Since(t0))
 	case 5:
 		lang := "en"
 		if rng.Intn(2) == 1 {
 			lang = "ru"
 		}
-		c, _ := d.edge.ProfileUpdate(ctx, p.Token, p.Name, lang)
-		d.rec.Record("profile.update", c, time.Since(t0))
+		code, _ := c.ProfileUpdate(ctx, p.Token, p.Name, lang)
+		d.rec.Record("profile.update", code, time.Since(t0))
 	default:
-		c, _ := d.edge.Stats(ctx, p.Token)
-		d.rec.Record("stats.get", c, time.Since(t0))
+		code, _ := c.Stats(ctx, p.Token)
+		d.rec.Record("stats.get", code, time.Since(t0))
 	}
 }