Show backend reachability in the UI, fed by the server-list heartbeat (OPE-439)

[Celant]

Stacked on #5365 (base is its branch); will be rebased onto main once it merges.

OPE-439. The server-list heartbeat from #5365 already knows whether the API answers — backendReachable() is null until the first attempt settles, true when the API answered at all (a 404 included), false on a timeout or a network error, with every change announced on the document as backend-reachability. Nothing consumed it. This is the half a player can see.

What this adds

retryServerList() in src/client/ServerList.ts — one attempt right now, at the player's request, deliberately ignoring the retry interval. That interval exists to stop timer-driven callers hammering a down API between heartbeats, and a person pressing a button is not one of those; making them wait up to 10s for anything to happen would make the button look broken in exactly the situation it exists for. Still deduped through fetchOnce(), so a repeat-clicker — or a click landing on top of a heartbeat beat — costs one request.

An offline state on the desktop status bar, with that Retry. The bar's one slot now ranks session > reachability > update:

• above the update, because an update failure while the backend is unreachable is a symptom of it: "Couldn't download the update — Retry" points at a button that provably cannot work until the network is back, while "Offline" names the actual cause;
• below the session, which names a more specific remedy (restart Steam, sign in again).

Nothing is shown while reachability is unknown. The task allowed a "Checking…" only if the bar already had a neutral state to hang it on, and it does not — barSource returns none and the bar renders nothing — so adding one would have meant a permanent strip across the bottom of a perfectly healthy game for the sake of its first few hundred milliseconds. The last-checked time mentioned in the issue is left out for the same reason: it would mean a re-rendering clock on a bar whose whole point is that it disappears.

Gating, web and desktop. shouldBlockMultiplayerAction takes reachability as a third, required parameter (required rather than optional so an entry point that forgets it is a compile error, not a silent ungating), and shouldBlockDesktopJoin is renamed shouldBlockJoin — the update and session halves are still desktop-only, but an unreachable backend refuses a join on the web too. Consumers: GameModeSelector, DetailedGameViewModal (the lobby browser is the same kind of entry point and its gate already mirrored the selector's), and Main.blockedJoin, which is the funnel every join passes through — matchmaking, deep links and the host/join modals all dispatch join-lobby without passing a dimmed button.

Feedback for a refusal is now one helper. On desktop it wiggles the bar that is already naming the reason; on the web, where there is no bar, it shows a transient show-message. It keys on isDesktopShell() and not on whether the <desktop-status-bar> element exists, because index.html mounts that element on every build and it simply renders nothing on the web.

Two rules the tests pin

• null never gates. Every page is in that state for its first few hundred milliseconds. Blocking there would lock every player out of multiplayer on every load, over a suspicion we have not even tested yet.
• Single-player is never gated, whatever reachability says — bot games run entirely in-client, and refusing one would break the desktop build's core offline promise. Transport and the in-game flows are untouched: this affects starting and joining only, never a game in progress.

Consumers seed from backendReachable() before subscribing to the event, because the event is one-shot: a component mounting after the first attempt settles would otherwise gate on null forever. That is OPE-396's bug on a new signal, and there is a test that mounts only after the attempt has failed, with no event dispatched anywhere in it.

Out of scope, as asked: no circuit breaker. OPE-403 can consume this same signal.

New i18n keys (resources/lang/en.json only)

key	text
desktop_status.offline	Offline: can't reach the OpenFront servers
desktop_status.retry	Retry
error_modal.backend_unreachable	Can't reach the OpenFront servers. Check your connection and try again.

Tests

• tests/client/ServerList.test.ts — retryServerList() attempts inside the interval that holds ensureServerList back, joins an attempt already in flight rather than starting a second, applies a list the retry brings back, and never throws.
• tests/ReachabilityGating.test.ts (new) — the web build: nothing dims before the first attempt settles; every entry point dims and refuses on false; the message fires; everything re-enables on true; single-player is untouched; and a selector that mounts after a failed attempt still gates, seeded from the accessor alone.
• tests/DesktopStatusBar.test.ts — barSource precedence, plus a rendering test driven through the real ServerList module: the offline label and Retry appear, Retry attempts immediately, and the bar clears when the API answers.
• tests/client/MainInitialize.test.ts — a join-lobby on an unreachable backend is refused with the message and never reaches joinLobby; the same join goes through once the API answers.
• tests/GameModeSelectorGating.test.ts — the pure rules, including multiplayerAllowedForBackend.

Verified: npx tsc --noEmit, npm run lint, prettier, and a full npx vitest run.

Retry schedule and button

Asked for on review: back the automatic retries off, and stop the manual one being spammable.

Backoff. retryDelayMs(consecutiveFailures) is the schedule, pure so it can be tested without a clock: RETRY_BASE_MS = 10s after the first unanswered attempt, doubling on each further consecutive one (20s, 40s), capped at RETRY_MAX_MS = 60s. Any answer resets it to the base — a 404 included — so a page that recovers and then misses once waits 10s, not a minute. retryDue() and the heartbeat's scheduleNextPoll both read it; the 30s success cadence is unchanged, and so is the "confirmed after two consecutive failures" rule, which still lands inside the first 10s because the backoff only stretches once there is an outage to back off from.

The button. Retry is now disabled while any server-list attempt is in flight — automatic or manual, via a new attemptInFlight() accessor plus a server-list-attempt document event fired on start and on settle — and for RETRY_BUTTON_COOLDOWN_MS = 5s after a press, whichever ends later. A separate event from backend-reachability because that one fires only on a change, so a failure identical to the last announces nothing, which is exactly the case the button has to see. During an automatic attempt the label and title read desktop_status.retrying rather than greying out for no visible reason. The 1s floor inside retryServerList() stays as the last line of defence.

New i18n key: desktop_status.retrying — "Retrying…".

Tests: retryDelayMs for 1/2/3/many failures, the cap and the post-answer reset; the heartbeat's own 10s → 20s → back-to-base progression; attemptInFlight and the event across a joined attempt and a fetch that throws; and, on the bar, click → disabled through the cooldown → enabled, an automatic attempt in flight → disabled with the retrying label, a settle inside the cooldown → still disabled, and a rapid triple click → one attempt.

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Walkthrough

The change adds debounced backend outage detection, throttled manual retries, multiplayer gating on web and desktop, and confirmed-outage status feedback. Tests cover recovery, retry behavior, join handling, and component rendering.

Changes

Backend reachability and multiplayer gating

Layer / File(s)	Summary
Confirmed outage state and retry flow src/client/ServerList.ts, resources/lang/en.json, tests/client/ServerList.test.ts, docs/MultiServer.md	ServerList confirms an outage after two consecutive failed attempts. Manual retries use a one-second floor and share in-flight results. Reachability events include confirmed.
Multiplayer outage gating src/client/GameModeSelector.ts, src/client/Main.ts, src/client/components/DetailedGameViewModal.ts, tests/GameModeSelectorGating.test.ts, tests/ReachabilityGating.test.ts, tests/client/MainInitialize.test.ts, tests/DetailedGameViewModalGatingWiring.test.ts, tests/client/Matchmaking.test.ts	Multiplayer entry points block when an outage is confirmed. Web joins report common.backend_unreachable. Matchmaking closes after a refused matchmade join. Single-player actions remain available.
Desktop outage status and retry src/client/components/DesktopStatusBar.ts, tests/DesktopStatusBar.test.ts	The status bar consumes the confirmed outage signal. Retry is disabled while its request is active and re-enables after completion.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Client
  participant ServerList
  participant GameModeSelector
  participant Main
  participant DesktopStatusBar
  Client->>ServerList: start or retry server-list request
  ServerList->>ServerList: count consecutive failures
  ServerList->>GameModeSelector: dispatch confirmed outage
  ServerList->>Main: expose confirmed outage
  ServerList->>DesktopStatusBar: dispatch confirmed outage
  GameModeSelector->>GameModeSelector: block multiplayer action
  Main->>Main: refuse join and report outage
  DesktopStatusBar->>DesktopStatusBar: render offline status

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Suggested reviewers: neon0404

Merge Risk: 🔵 Low · up to db98f

Client teardown behavior is covered, but queue removal after disconnect is not validated against a repository-owned server handler. This is bounded test-coverage risk rather than a demonstrated production failure.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 28 functions across 12 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: exposing backend reachability in the UI through the server-list heartbeat.
Description check	✅ Passed	The description directly explains the reachability signal, retry behavior, UI changes, multiplayer gating, localization, and tests in the changeset.

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Inline comments:
In `@tests/client/MainInitialize.test.ts`:
- Around line 382-386: Update the recovery-path test around handleJoinLobby to
wait for mocks.joinLobby to have been called exactly once, rather than only
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• resources/lang/en.json
• src/client/GameModeSelector.ts
• src/client/Main.ts
• src/client/ServerList.ts
• src/client/components/DesktopStatusBar.ts
• src/client/components/DetailedGameViewModal.ts
• tests/DesktopStatusBar.test.ts
• tests/GameModeSelectorGating.test.ts
• tests/ReachabilityGating.test.ts
• tests/client/MainInitialize.test.ts
• tests/client/ServerList.test.ts

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[Celant]

Review findings addressed in a6bc839.

1 [High] One failed heartbeat locked multiplayer out — fixed

The finding is right, and it was the worst thing in the PR: backendReachable() flips on any failed attempt, so a single 4s timeout at t=30s dimmed every button and refused every join for at least a retry interval, while the cached list carried on serving and the next request would very likely have worked. On the web there was not even a Retry to escape with.

ServerList now counts consecutive unanswered attempts and exposes backendUnreachableConfirmed(), true only once two in a row have failed — a retry interval's worth of evidence. Any answer resets the count; a failed manual retry counts towards it (pressing Retry against a backend that is genuinely down should settle the question sooner, not reset it); it is never true before the first attempt settles.

backendReachable() and the event stay as the raw signal, as asked. The event detail is now { reachable, confirmed } and fires when either changes — the second failure moves only confirmed, and that is the transition every gate acts on, so comparing reachable alone would have swallowed it. All three gates (GameModeSelector, DetailedGameViewModal, Main.blockedJoin) and the status bar's offline state read the confirmed value. docs/MultiServer.md updated with both signals and the retry semantics.

Tests: one failure → nothing gated (asserted at the pure rule, at the selector, at the lobby browser and in the rendered bar); two → gated; a success → cleared, and the count restarts so a later single failure is a blip again, not a resumption.

2 [Medium] Unthrottled retry, no feedback — fixed

retryServerList() has a 1s floor. Inside it a second press is a no-op that hands back the same promise; past it, fetchOnce() still dedupes against an attempt in flight. The bar disables Retry while its own attempt is out — a button that keeps accepting clicks and visibly does nothing reads as broken whatever the throttle underneath is doing. The test that pinned the unthrottled behaviour now pins the throttle instead (same promise identity, no second fetch), and there is a new rendering test for the disabled window.

3 [Medium] DetailedGameViewModal untested — fixed

Four cases added to tests/DetailedGameViewModalGatingWiring.test.ts, driven through the real ServerList module: mount after a confirmed outage with no event dispatched → card click refused (the seed); the cards marked aria-disabled on that same seed; recovery through the event → allowed (the subscribe); and a single-failure control that asserts the join still goes through.

4 [Low] Refused matchmade join left the modal waiting — fixed

There is a clean hook: MatchmakingModal.close() is what its own Back button calls, and its onClose() shuts the queue socket, clears the watchdog and cancels the reconnect timers. Main.blockedJoin now calls it when lobby.source === "matchmaking" and the modal is open, so the player leaves the queue rather than holding a slot from a screen that is lying to them. Scoped to that source deliberately: a deep link refused while someone is legitimately queued must not cancel their queue.

5 [Low] Stale doc comment — fixed

It now says the bar renders nothing on the web, and that on a shell too old to expose the update bridge it still renders the session and outage states — both are the client's own signals — with only the update half going quiet. The "one bottom slot, two kinds of status" line is now three.

6 [Nit] Toast key — moved

error_modal.backend_unreachable → common.backend_unreachable. It is raised from three different features (the selector, the lobby browser and the join funnel) rather than owned by one, and common.* is where the other cross-feature show-message toasts live (common.copied, common.failed_copy); feature-owned toasts keep their own namespace, e.g. clan_modal.*.

Follow-up: bd88736

Fair catch on re-review — the source === "matchmaking" branch in blockedJoin had no test and would have survived a revert. Two now cover it in the boot harness, one per half: a refused matchmade join calls matchmakingModal.close(), and a refused join from any other source leaves a live queue alone (the scoping is the point, not an accident). The modal is spied rather than opened for real — opening it would open a queue WebSocket, and the claim under test is only which joins reach close(). The negative case waits for the refusal itself to land before asserting close() was not called, so it cannot pass by having tested nothing yet. Checked against an actual revert: deleting the branch fails "takes a refused matchmade join out of the queue", and nothing else.

Follow-up: db98fdd

The funnel test above spies on MatchmakingModal.close(), which is only sound if the real close() genuinely takes the player out of the queue — and nothing asserted that. tests/client/Matchmaking.test.ts now pins it, against a real modal and its socket: close() shuts the queue socket and cancels the watchdog (a watchdog left running reconnects at 15s and re-queues the player), and a close frame arriving afterwards does not trigger the "service restarted, rejoin" path. Both checked against a revert: dropping socket.close()/clearWatchdog() fails the first, dropping intentionalClose as well fails both.

Verification

npx tsc --noEmit clean, npm run lint clean, npx prettier --check src tests docs resources/lang/en.json clean. The requested test files plus GameModeSelectorGating, DesktopUpdateStateSeeding and EnJsonSorted: 10 files, 147 tests, all passing.

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Inline comments:
In `@tests/ReachabilityGating.test.ts`:
- Around line 117-121: Refactor the reachability tests in
ReachabilityGating.test.ts to use setup() from Setup.ts and real simulation
inputs instead of mocked fetch calls or PublicLobbySocket instances. Preserve
the existing scenarios and assertions while exercising the core integration path
through the configured simulation.

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• docs/MultiServer.md
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• src/client/GameModeSelector.ts
• src/client/Main.ts
• src/client/ServerList.ts
• src/client/components/DesktopStatusBar.ts
• src/client/components/DetailedGameViewModal.ts
• tests/DesktopStatusBar.test.ts
• tests/DetailedGameViewModalGatingWiring.test.ts
• tests/GameModeSelectorGating.test.ts
• tests/ReachabilityGating.test.ts
• tests/client/MainInitialize.test.ts
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Inline comments:
In `@tests/client/MainInitialize.test.ts`:
- Around line 386-387: Update the test around the modal spies to remove the
isOpen and close mocks. Configure the modal’s open state through setup(), then
exercise the core simulation directly and assert that the real close() teardown
removes the player from the queue.

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[Celant]

Rebased onto the new base (josh/multi-server-v2-client-list @ af8e4fc3d, "Keep the rollover feel: draining serves its own build, no redirect"). New head: 60e4271.

One real conflict, in tests/client/ServerList.test.ts: my retryServerList describe was anchored immediately before describe("when no open server runs the client's version"), which the base replaced wholesale with describe("picking between open, draining and fenced"). Resolved by keeping the base's new describe intact and re-seating my block ahead of it — the stale REDIRECT const and the /v/<latest>/ navigation cases went with the base's rewrite, as intended.

Two follow-ons the base required:

• retryServerList() now calls apply() — apply(false) was the old redirectIfOutOfDate argument, which no longer exists.
• ServerListStatus gained "outdated" and lost "redirecting". Nothing in this PR's UI ever referenced either: the gates and the status bar read backendUnreachableConfirmed(), not the list status, so the new "outdated" flows through untouched to the caller that raises the update prompt. (grep for "redirecting" in src/client only finds Payments.ts, unrelated.)

Everything else — the consecutive-failure/confirmed-outage logic, the 1s manual-retry floor, the { reachable, confirmed } event, all three gates, the status bar and the matchmaking teardown — carried over unchanged.

Verified on the rebased tree: npx tsc --noEmit clean, npm run lint clean, npx prettier --check src tests docs resources/lang/en.json clean; the reachability set (ReachabilityGating, DesktopStatusBar, DetailedGameViewModalGatingWiring, GameModeSelectorGatingWiring, GameModeSelectorGating, DesktopUpdateStateSeeding, client ServerList, MainInitialize, Matchmaking, core ServerList) 10 files / 168 tests green; and a full npx vitest run — 451 files, 5579 tests, 0 failures.

---

Rebased again onto 6780dc7b1 ("Prompt when the server goes away mid-session, and refuse to create"). New head: 046eae5.

No conflicts this time — that base commit touches Api.createLobby, LobbySocket and their tests, none of which this PR goes near: the gates read backendUnreachableConfirmed() rather than the list status, so Api.createLobby throwing on "outdated" and LobbySocket.promptIfOutdated() are orthogonal to the reachability gate and compose with it unchanged.

Re-verified on the new base: npx tsc --noEmit, npm run lint and npx prettier --check src tests docs resources/lang/en.json all clean; the reachability set plus that commit's own touched files (GameServerApiCallers, LobbySocket, core ServerList) — 12 files / 194 tests green.

The full run on this workstation came back with timeouts in tests/client/InventoryModal.test.ts and tests/client/MainInitialize.test.ts — all of them bare Test timed out / Hook timed out, no assertion failures, in a run whose transform and import times were roughly double a quiet one (several worktrees were running vitest at once). Both files pass on their own, 36/36, and the full run on the previous rebase of this same branch was 451 files / 5579 tests with zero failures. Noting it rather than hiding it; CI's 🔬 Test job is the cleaner signal.

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🤖 Claude Code Review

Verdict: No issues found — this PR is safe to proceed. Findings: 0 critical, 0 high, 0 medium, 0 low.

Reviewed the full diff (docs/MultiServer.md, resources/lang/en.json, src/client/GameModeSelector.ts, src/client/Main.ts, src/client/ServerList.ts, src/client/components/DesktopStatusBar.ts, src/client/components/DetailedGameViewModal.ts, and the associated test files) across four independent passes: two for CLAUDE.md compliance and two for bugs/security/logic issues.

• CLAUDE.md compliance: All three new user-visible strings (common.backend_unreachable, desktop_status.offline, desktop_status.retry) are routed through translateText() with matching entries in resources/lang/en.json; no other translation file was touched; no src/core files were modified.
• Bugs/logic: Verified every renamed symbol (shouldBlockDesktopJoin→shouldBlockJoin, blockedByUpdate→blockedFromMultiplayer, etc.) is updated consistently at all call sites and tests; the backend-reachability event shape ({ reachable, confirmed }) matches between dispatch and all three listeners; listeners are added/removed in pairs; every gate consistently reads the debounced backendUnreachableConfirmed() rather than the raw backendReachable(); the 2-failure debounce counter and event-dispatch-on-transition logic have no off-by-one; no XSS or unsafe DOM usage was introduced.
• One candidate issue was raised during review (a concern that gating multiplayer joins on server-list-API reachability could needlessly refuse joins/cancel a matchmaking queue when only the list API, and not the actual game server, was down) but was investigated against the live code and disproven: the list API and the matchmaking queue socket share the same api.<audience> origin, so that scenario cannot occur in practice.

No issues found. Checked for bugs and CLAUDE.md compliance.

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🤖 Claude Code Review

Verdict: Request changes — one high-confidence correctness bug found. No CLAUDE.md violations found.

Findings by severity: 1 High, 0 Medium, 0 Low

---

High

1. src/client/Main.ts:1203-1238 (blockedJoin, gate read at line 1208) — web join gate refuses re-entry to an already-running game (and any web join) during a server-list-API-only outage, even though the game server itself is confirmed reachable

blockedJoin now computes backendOutage = backendUnreachableConfirmed() unconditionally and passes it into shouldBlockJoin (src/client/GameModeSelector.ts:169-177) for both desktop and web — previously the function returned false immediately on web (if (!isDesktopShell()) return false;), so this gate never applied there.

backendUnreachableConfirmed() reflects the health of the server-list API (the separate Cloudflare Worker at serverListUrl()/api.<domain>), not the game servers. ServerList.ts is explicitly designed so a failed server-list fetch is survivable — ensureServerList() returns "fallback" and cached/bootstrap values keep serving.

Reachable failure path: if the server-list API has two consecutive failed heartbeats (~10s) while game servers stay healthy, and a player reloads a URL for a game they're already in, JoinLobbyModal.checkActiveLobby (src/client/JoinLobbyModal.ts:1326-1366) fetches gameInfo.exists from the game server itself (proof that service is up), then dispatches join-lobby with source: "private" and no gameRecord. joinIsGateable (GameModeSelector.ts) returns true for that shape (no singleplayer gameStartInfo, no gameRecord), so shouldBlockJoin blocks purely because the unrelated server-list API is down. blockedJoin then closes the join modal, which (via onClose) dispatches leave-lobby and resets the URL to /, ejecting the player from a game confirmed to be live only moments earlier.

This also contradicts the PR's own stated scope in docs/MultiServer.md ("Single-player is never gated, and nothing here touches a game already in progress") — this path does touch an in-progress game.

More broadly, every web join (public lobby, private code, matchmaking) is now refused during any transient server-list-API blip, a condition ServerList.ts was explicitly built to survive.

Suggested fix: Don't gate joins where the client has already confirmed the target game exists on its own game server (e.g. exempt the checkActiveLobby/gameInfo.exists path, or otherwise scope the backendOutage gate to lobby creation/matchmaking rather than every join-lobby dispatch), so rejoining a live game isn't refused because a different, non-critical service is temporarily unreachable.

---

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[Celant]

Fixed in 7547dec — you're right, and I took the broader fix rather than exempting one path: reachability is no longer an input to the join funnel at all. I confirmed all four join-lobby dispatch sites have already reached a server before they fire — private only after checkActiveLobby gets exists: true from the game's own server, host only after createLobby() resolves with a server-minted id, public only from a lobby card delivered over a live PublicLobbySocket, and matchmaking only after the queue socket (ClientEnv.jwtIssuer()) matches and checkGame probes /exists on the game server — so the server-list API's health can never say anything useful about a join in hand, and a refusal there could only reject one that is already under way. shouldBlockJoin drops its backendOutage parameter (its two remaining inputs are desktop-only) and Main.blockedJoin calls reportMultiplayerRefusal(false), so the web never refuses in the funnel; the status bar, the dimmed buttons in GameModeSelector/DetailedGameViewModal, shouldBlockMultiplayerAction's outage input and the web toast for a refused button press are all unchanged, and common.backend_unreachable is still used by those. Pinned by tests/GameModeSelectorGating.test.ts ("never blocks a join, whatever the reachability signal says") and by tests/client/MainInitialize.test.ts, whose funnel block now asserts the positive: with the outage confirmed a private join still reaches joinLobby with the dispatched gameID, no common.backend_unreachable toast is raised, and the matchmaking modal is not torn down — with the reachable case kept as the control. docs/MultiServer.md now states what the signal does and does not do. Full suite green: 468 files, 5819 tests.

[github-actions]

🤖 Claude Code Review

Verdict: No issues found — 0 findings (0 critical, 0 major, 0 minor).

Reviewed the diff for PR #5384 (backend reachability UI + multiplayer gating) across four independent passes: two CLAUDE.md compliance audits and two bug/security-focused scans (Opus). Checks included:

• All new user-visible strings (common.backend_unreachable, desktop_status.offline, desktop_status.retry) go through translateText() and have corresponding entries in resources/lang/en.json; no other translation files were touched.
• No src/core changes, so determinism rules don't apply.
• Rename fan-out (setReachable→recordAttempt, shouldBlockDesktopJoin→shouldBlockJoin, blockedDesktopJoin→blockedJoin, blockedByUpdate→blockedFromMultiplayer, barSource arity) is complete — no stale call sites.
• recordAttempt debounce/state machine, retryServerList() throttle/dedupe logic, event listener seed-then-subscribe ordering, and barSource precedence (session > reachability > update) all check out correctly.
• No compile errors, logic inversions, or leaked event listeners/timers found in the changed code.

No inline comments to post.

[github-actions]

🤖 Claude Code Review

Verdict: No issues found — this PR is ready as-is. Findings: 0 critical, 0 major, 0 minor.

Reviewed the diff for openfrontio/OpenFrontIO#5384 ("Show backend reachability in the UI, fed by the server-list heartbeat (OPE-439)") across four independent passes: two CLAUDE.md compliance checks and two focused bug/logic/security scans.

CLAUDE.md compliance: All new user-visible strings (common.backend_unreachable, desktop_status.offline, desktop_status.retry, desktop_status.retrying) go through translateText() with matching entries in resources/lang/en.json, and no other translation files were touched. No src/core/ changes are present, so the determinism/no-dependencies/tests-required rule for core doesn't apply. Testing patterns and Lit component conventions are followed consistently with the rest of the codebase.

Bugs/logic/security: Traced the two-tier reachability state machine (backendReachable/backendUnreachableConfirmed), the retry backoff schedule (retryDelayMs), in-flight/event-announcement ordering in fetchOnce, the seed-before-subscribe pattern in GameModeSelector/DetailedGameViewModal/DesktopStatusBar, the shouldBlockDesktopJoin → shouldBlockJoin rename and its required-backendOutage-param refactor, and the new matchmaking-modal teardown on refusal. No off-by-one errors, inverted conditions, missed call sites, race conditions, or unsafe DOM/string handling were found.

Two non-blocking observations surfaced during review (not flagged as defects, since both are either unreachable in current usage or explicitly documented/tested as intentional design):

• DesktopStatusBar's backend-reachability/server-list-attempt listeners are registered only inside the isDesktopShell() branch, unlike the always-registered desktop-session-state listener — a structural asymmetry the code already comments on, not a live bug given how Electron preload injection works today.
• The PR argues at length that join-time gating should exclude backend reachability (a live game-server socket already proves liveness), yet lobby-browsing UI (GameModeSelector/DetailedGameViewModal) still dims/refuses lobby cards during a confirmed server-list outage even though those cards are populated over the same live socket. This is documented and tested as intentional, so worth a maintainer's awareness rather than a required change.

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[github-actions]

🤖 Claude Code Review

Verdict: Solid, well-tested feature with good separation between the "twitchy" and "confirmed" reachability signals — but two real logic/design inconsistencies should be addressed before merge. Findings: 2 medium, 0 high, 0 low.

src/client/ServerList.ts / src/client/GameModeSelector.ts / src/client/components/DesktopStatusBar.ts

1. Web players who get gated out have no way to force a retry, and the new backoff makes the wait longer than before this PR.

retryServerList() — the only function that forces an immediate heartbeat probe — is called from exactly one place in production code: DesktopStatusBar.onRetryClick(). That status bar is desktop-only (connectedCallback gates the subscription and rendering behind isDesktopShell(); per the diff's own doc comment it "renders nothing on the web"). reportMultiplayerRefusal() (src/client/GameModeSelector.ts) only calls wiggle() and shows a toast (translateText("common.backend_unreachable"), i.e. "Check your connection and try again") — it never calls retryServerList() or triggers any new probe. So on web, once backendUnreachableConfirmed() flips true (after just 2 consecutive missed heartbeats), the only way it flips back is an automatic poll succeeding — and this PR replaces the old flat RETRY_INTERVAL_MS = 10_000 poll with an exponential backoff (retryDelayMs: 10s → 20s → 40s → 60s) that retryDue() now obeys too. Since gating triggers at 2 failures, the very first post-gate poll is already 20s away, growing to 60s.

Net effect: a short (~12s) connectivity blip can lock a web player out of all multiplayer entry points for up to 60s, with a message telling them to "try again" and no action that actually retries anything — a regression versus the flat 10s polling that existed before this PR.

Suggested fix: have the web branch of reportMultiplayerRefusal (or the refused click handler) call void retryServerList() so a refused click doubles as a manual probe, giving web users the same escape hatch the desktop Retry button provides.

2. The join-button gate contradicts the funnel gate's own stated rationale for the same category of lobby.

shouldBlockJoin's docblock (src/client/GameModeSelector.ts) explicitly argues backend-API reachability must not gate a join, because e.g. a "public" lobby "arriv[es] over a live server socket, so the server-list API's health says nothing about that server's availability — refusing here could only reject a join that is already under way." Consistent with that, shouldBlockJoin hardcodes false for the reachability argument (shouldBlockMultiplayerAction(update, session, false)), and Main.ts's blockedJoin follows the same rationale.

However, the click handlers that produce that very same "public" join — GameModeSelector.validateAndJoin(lobby) and DetailedGameViewModal.join(lobby) — do pass this.backendOutage/backendOutage into shouldBlockMultiplayerAction (both for the actual click-through and for dimming the lobby card), with no carve-out for lobby.source === "public" or any other socket-sourced lobby. So the exact category of lobby the docblock says "refusing here could only ever be wrong" is precisely what gets dimmed/refused one step earlier in the funnel, based on the health of an unrelated API (the server-list API, not the game server the lobby socket already proved was live).

Suggested fix: either exempt public/socket-sourced lobbies from the backendOutage check in validateAndJoin/DetailedGameViewModal.join (consistent with shouldBlockJoin's reasoning), or, if gating the initial click is intentional (e.g. as a coarse "the API might be having a bad day" signal), update the shouldBlockJoin docblock to explain why the same reasoning doesn't apply one step earlier.

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[Celant]

Both findings verified and fixed in one pass: 4577bb2.

The rule the code now follows, stated once at the top of GameModeSelector.ts and referenced from every call site: the reachability signal is the health of one thing, the server-list API. It gates only actions that cannot begin until that API answers.

• Gated (API-dependent): Create, Ranked, Join-by-code. These still dim and refuse.
• Not gated (socket-sourced): every public and hosted lobby card, in the homepage selector and in DetailedGameViewModal alike, plus every join reaching Main's funnel.

Finding 2 (true): validateAndJoin, DetailedGameViewModal.join and both cards' dimming passed backendOutage for exactly the "public" join shouldBlockJoin argued must never be refused on it. All four now call a new shouldBlockSocketSourcedAction(update, session) — the same predicate with the reachability input nailed shut — so dimming and click-through of a control cannot drift. DetailedGameViewModal no longer subscribes to backend-reachability at all.

Finding 1 (true): retryServerList() had one production caller, desktop-only. reportMultiplayerRefusal now probes on the web before raising the toast, so the refused click is the retry and "try again" is true. Throttled by a new ServerList.manualRetryAvailable() — nothing while an attempt is in flight, nothing for MANUAL_RETRY_COOLDOWN_MS (5s) after the last player-initiated one. That constant moved out of DesktopStatusBar so both shells' affordances share one number and one clock. Backoff, server-list-attempt and attemptInFlight() are unchanged; common.backend_unreachable needed no rewording.

Tests: 15 added/rewritten across ReachabilityGating, DetailedGameViewModalGatingWiring, GameModeSelectorGating and client/ServerList, each checked by mutation to fail against the old behaviour. docs/MultiServer.md updated. Full suite 5944 passing, tsc --noEmit and prettier clean.

[github-actions]

🤖 Claude Code Review

Verdict: No high-signal issues found. Findings by severity: 0 blocking, 0 major, 0 minor.

Reviewed for CLAUDE.md compliance and bugs/security issues across the diff (src/client/ServerList.ts, src/client/GameModeSelector.ts, src/client/Main.ts, src/client/components/DesktopStatusBar.ts, src/client/components/DetailedGameViewModal.ts, resources/lang/en.json, tests).

• All new user-visible strings (offline label, Retry/Retrying, backend-unreachable toast) go through translateText() with matching entries added only to resources/lang/en.json; no other translation files touched; no src/core files touched.
• Two candidate issues surfaced during review and were both investigated and ruled out:
  • A coolingDown flag in DesktopStatusBar.ts that's cleared via timer but not reset in disconnectedCallback/connectedCallback — not reachable in practice, since <desktop-status-bar> is a permanent index.html body child that's hidden via CSS in-game and never unmounted.
  • The API-dependent gate (multiplayerAllowedForBackend) blocking Create/Join-by-code even when a warm cached server list would let the action succeed — this is a deliberate, documented tradeoff (the 2-consecutive-failure confirmation debounce exists precisely for this case), the gate is soft and self-healing, and Ranked is genuinely API-dependent via the matchmaking websocket.
• The two invariants the PR calls out (reachability null never gates; single-player is never gated) were independently verified against the code and hold.

No issues found. Checked for bugs and CLAUDE.md compliance.