Browser fetch-streaming layers close response bodies they consider
idle after roughly 15-30 s without incoming bytes. Safari is the
most aggressive, but the symptom matters everywhere: a quiet
SubscribeEvents stream (lobby, between turns, mailbox empty) gets
torn down by the browser, the EventStream singleton reconnects with
backoff, and any push event that fires inside the reconnect window
is lost because `push.Hub` queues are not persisted across
subscription closes. The user-visible failure mode is the
intermittent "Fetch API cannot load … due to access control checks"
console error (a misleading WebKit symptom — CORS headers are
actually present) plus missed turn-ready / mail-received toasts.
Server-side fix: a silence-based heartbeat at the
`authenticatedPushStreamService` wrapper layer. After the signed
`gateway.server_time` bootstrap event, gateway wraps the bound
stream with `heartbeatingStream`. Every tail Send (fan-out, future
variants) resets the silence timer; when the timer elapses, a
goroutine emits `gateway.heartbeat` with only `EventType` set —
everything else stays at proto3 defaults, so the wire frame is
~45 bytes amortised. A `sendMu` serialises the heartbeat goroutine
with tail Sends because grpc.ServerStream.Send is not goroutine-safe.
The heartbeat is intentionally UNSIGNED: heartbeats carry no
payload, dispatch to no handler on the client, and an injected
heartbeat trivially causes no user-visible state change. TLS still
protects the wire and real events keep the signed envelope
unchanged. Documented in `docs/ARCHITECTURE.md` § 15 alongside the
per-scale bandwidth projection (100…100 000 clients × 15…60 s).
Config: new `GATEWAY_PUSH_HEARTBEAT_INTERVAL` (default `15s`,
`0s` disables). Telemetry: new
`gateway.push.heartbeats_sent{outcome}` counter so operators can
budget bandwidth and spot a sudden `outcome=error` bump as an
upstream-failing-before-flush signal.
Client (`ui/frontend/src/api/events.svelte.ts`): early `continue`
on `event.eventType === "gateway.heartbeat"` before `verifyEvent`,
`verifyPayloadHash`, or dispatch — empty signature would otherwise
trip SignatureError and reconnect. A leading heartbeat still flips
`connectionStatus` to `connected` and resets backoff, because
receiving one is proof the stream is healthy.
Tests:
- `push_heartbeat_test.go`: unit tests for the wrapper — zero
interval returns nil, heartbeat fires after silence, real Send
resets the timer, Stop / context-cancel halt the goroutine,
Send errors propagate.
- `server_test.go`: integration tests through the full gateway
pipeline — heartbeat fires after the configured silence window,
zero interval keeps the stream silent.
- `config_test.go`: default applied, env-override parsed,
negative value rejected.
- `events.test.ts`: heartbeat skipped before verification + not
dispatched to handlers; leading heartbeat still flips
`connectionStatus` to `connected`.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Backend now owns the turn-cutoff and pause guards the order tab
relies on: the scheduler flips runtime_status between
generation_in_progress and running around every engine tick, a
failed tick auto-pauses the game through OnRuntimeSnapshot, and a
new game.paused notification kind fans out alongside
game.turn.ready. The user-games handlers reject submits with
HTTP 409 turn_already_closed or game_paused depending on the
runtime state.
UI delegates auto-sync to a new OrderQueue: offline detection,
single retry on reconnect, conflict / paused classification.
OrderDraftStore surfaces conflictBanner / pausedBanner runes,
clears them on local mutation or on a game.turn.ready push via
resetForNewTurn. The order tab renders the matching banners and
the new conflict per-row badge; i18n bundles cover en + ru.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Wires the gateway's signed SubscribeEvents stream end-to-end:
- backend: emit game.turn.ready from lobby.OnRuntimeSnapshot on every
current_turn advance, addressed to every active membership, push-only
channel, idempotency key turn-ready:<game_id>:<turn>;
- ui: single EventStream singleton replaces revocation-watcher.ts and
carries both per-event dispatch and revocation detection; toast
primitive (store + host) lives in lib/; GameStateStore gains
pendingTurn/markPendingTurn/advanceToPending and a persisted
lastViewedTurn so a return after multiple turns surfaces the same
"view now" affordance as a live push event;
- mandatory event-signature verification through ui/core
(verifyPayloadHash + verifyEvent), full-jitter exponential backoff
1s -> 30s on transient failure, signOut("revoked") on
Unauthenticated or clean end-of-stream;
- catalog and migration accept the new kind; tests cover producer
(testcontainers + capturing publisher), consumer (Vitest event
stream, toast, game-state extensions), and a Playwright e2e
delivering a signed frame to the live UI.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Ilia Denisov