[lidge-jun]

Summary

A Remote Link Home could show a link as failed for over an hour. During that time the Child answered GET /healthz with 200 and every relayed turn with 503 {"error":"link tunnel unavailable"}, and nothing on either side recorded why. This PR:

• carries fix(link): recover preflight deadlines with bounded diagnostics #7491 onto the latest dev;
• keeps failed Home tunnels retrying with a capped backoff;
• names the stale-remote-forward cause;
• records each tunnel transition durably;
• makes a Child's /readyz report whether the link can carry a request.

What the source shows. Since 2.84 (#6915) the Home's -R supervisor already retries forward, timeout and auth failures. Two paths still never recover:

• a changed host key, which stays terminal on purpose;
• spawnFor with no listener port in the store, which set failed with no retryAt.

The incident fits a third case that looks permanent. When the Home's ssh dies (sleep, network change), the Child's sshd keeps holding 127.0.0.1:<tunnelPort> for the dead session. Every new ssh -R … -o ExitOnForwardFailure=yes then exits with remote port forwarding failed, and the link keeps reading failed / forward. The status shows no attempt count, no next retry and no cause, and ~/.opencodex/link gets no log. Without ClientAliveInterval, sshd holds the port until TCP keepalive notices the dead peer, which takes two hours by default on macOS.

Changes

• Retry (src/link/tunnel-state.ts, src/link/supervisor.ts). The first retry of a failed forward or timeout link comes after 60 s. Each retry that fails again doubles the delay, up to 5 min (maxRetryDelayMs). The state's retries counts them, and a connection resets the cadence. Auth stays at 5 min, which keeps the 12-attempts-an-hour bound. A host key change stays terminal. A missing listener port is now an ordinary retried forward failure, and a reload that restores the port starts a fresh attempt. A retry whose ssh cannot be spawned counts as a failed retry. The Child's own -L supervisor shares the policy.

• Classification. remote port forwarding failed is now its own stderr class. It still fails the link with reason forward, so the K16 reason and the dashboard's reason map are unchanged, and it carries detail: "remote_forward_conflict". Local -L bind failures stay forward.

• Durable record (src/link/tunnel-history.ts). The supervisor routes every state change through one function. Per link it keeps:

  • attempt: ssh attempts since the link was last connected;
  • lastTransition: {from, to, at, cause};
  • lastFailure: {cause, at}.

  A cause is one fixed word: auth, hostkey, forward, remote_forward_conflict, timeout, network, unknown, spawn_failed or listener_unavailable.

  • GET /api/link/status?diagnostics=1 adds this as each Home-initiated row's tunnel field, with nextRetryAt. ocx link status requests the field and validates it.
  • Each transition, including a failed retry, is also a tunnel_transition record in the bounded <configDir>/link/diagnostics.jsonl from fix(link): recover preflight deadlines with bounded diagnostics #7491 (256 KiB plus one backup). It holds previousState, state, outcome, attempt, tunnelPort and retryAfterMs. stop() drains it for at most 1 s.

• Child readiness (src/client/link-readiness.ts, src/client/machine-listener.ts). In link mode the Child's /readyz answers 503, Retry-After: 1, status: "pending" and link: {state: "unavailable", reason} while relayed requests cannot be served. Otherwise it answers 200, status: "ready" and link: {state: "available"}. /healthz is unchanged.

  • A Child-initiated link reads its own supervisor.
  • A Home-initiated link runs probeLinkRelayPreflight (src/client/link-relay-transport.ts). This is the credential-free challenge every relayed request already begins with, sent on its own connection with no link key, data request or body. One preflight runs at a time, its verdict is reused for 5 s, and /readyz waits at most 500 ms for a running preflight before it answers link_unverified.

• Docs. Updated structure/remote-link.md, structure/gui-and-management-api.md, the Remote Link guide and the CLI lifecycle reference.

  • The Remote Link guide covers the readiness reasons, the tunnel field and tunnel_transition records, and a troubleshooting entry for remote_forward_conflict that recommends ClientAliveInterval 15 / ClientAliveCountMax 3 on the Child's sshd.
  • In all seven translated Remote Link guides, only the retry-cadence sentence changed, so none of them contradicts the English text.

Refs #7297 (durable Remote Link failure diagnostics). This PR adds bounded tunnel-state evidence and readiness. It does not add the opt-in SSH debug interface the issue also discusses.

Carries #7491 by @arikon: all ten commits replayed onto dev 5f7f7db57 with authorship unchanged. The only conflict was the first line of tests/fixtures/test-layout-expected.json. #7491 had no unresolved review threads. If #7491 lands first, this branch rebases onto it and those commits drop out.

Co-authored-by: Sergey Belov peimei@ya.ru

Decisions

1. Backoff: 60 s doubling to a 5 min cap; jitter only on the existing reconnecting phase.
   • A stale remote forward can last as long as the Child sshd's dead-peer detection, up to about 2 h with default TCP keepalive on macOS. A fixed one-minute cadence costs about 120 SSH logins on the Child in such an outage. The cap keeps that to about 12 an hour, and recovery still comes within 5 minutes after the port frees.
   • Retry in the dashboard and ocx link reconnect stay immediate.
   • Auth keeps its 5 min cadence (base = cap). A host-key change stays terminal because it is a security signal.
   • The failed-state delay is deterministic: one Home dials each Child, so there is no herd to spread.
2. remote_forward_conflict is a detail and a cause, not a new TunnelFailure member. The wire reason stays forward. The GUI's REASON_TKEY map and the K16 reason values are unchanged, so this PR makes no GUI change.
3. No remote or local process killing. OpenCodex neither kills the Child's stale sshd listener nor adds a kill path for an unverified local orphan ssh on macOS. Both would change host state that the user owns. The PR classifies, retries and documents the sshd ClientAliveInterval setting instead.
4. Readiness lives on /readyz, not /healthz. /healthz keeps its liveness meaning, which restart handoff, the update job and the service sentinel rely on. A down link reads pending rather than failed because it can recover, and ocx ready --wait exits at once on failed. The link object is additive. Reasons come from a fixed list: tunnel_connecting, tunnel_failed, tunnel_idle, tunnel_unavailable, sidecar_invalid, home_unreachable, home_unauthorized, link_auth_failed, link_credential_unavailable and link_unverified. A Child-initiated link whose Home answers its keyed probe as home_not_ready reads ready, because relayed requests do not depend on the Home's startup sync.
5. Home-initiated readiness actively probes. A verdict taken only from past relay outcomes could deadlock: a caller that stops sending once /readyz reads not ready would never produce the request that clears it. The preflight is the one every relay request already sends. The 5 s TTL with single flight limits an unauthenticated local caller to one preflight per 5 s. The 500 ms wait keeps /readyz inside ocx ready's 750 ms probe ceiling.
6. tunnel is opt-in (?diagnostics=1). This follows the ?compatibility=1 precedent: an older ocx link status validates link rows key by key and would reject an unknown key.
7. The durable record reuses fix(link): recover preflight deadlines with bounded diagnostics #7491's bounded diagnostics file instead of a new log. It names a link by tunnelPort, not by link id or alias, which keeps fix(link): recover preflight deadlines with bounded diagnostics #7491's no-identifier rule. Rate limiting stays per event/outcome across links.
8. The history lives in memory, so it is empty after a Home restart. The diagnostics file is the record that survives a restart.

Child 2.83.0 → current: how the version gap shows and how to update (read-only check)

Nothing on the affected Child was changed or restarted.

• The Child at 2.83.0 speaks relay-auth/2 (2.69.0+), so relaying works. It predates link-management-relay (2.84.0), link-peer-report/1 (2.91.0) and the 2.84.0 empty-store Home-initiated Child projection (fix(link): verify Child runtime relay and add fingerprint-bound CLI enrollment #6955). That last point is why its own ocx link status printed {"role":"standalone","links":[],"child":null}.
• The Home at 2.90.0 cannot show the Child's version. The peer and local blocks of ocx link status --json start at 2.91.0. Once the Home is on 2.91.0 or later and the Child has relayed one request since the Home started, the Home reports that link as compatible, with version: null, versionRange: {"min": "2.69.0", "below": "2.91.0"} and the reason "The Child does not report its version; it predates link-peer-report/1." Before that request it reads unknown (src/link/compatibility.ts, Remote Link guide → "Home and Child versions").
• Updating the Child. The affected Child runs the macOS Desktop app, a compiled standalone install. ocx update refuses there with installer: "standalone" and reason: "standalone_install". The update path is Check for Updates… in OpenCodex Desktop (tray or the dashboard's Desktop update), or a reinstall from GitHub Releases (CLI lifecycle reference, ocx update). The link configuration survives the update.
• Docs gap. The Remote Link troubleshooting line "OpenCodex on the remote computer is too old: run ocx update" does not mention Desktop installs. I left it unchanged as out of scope and noted it here.
• After both sides run a build with this PR, the Child's /readyz and ocx ready report the link state directly, and the Home's ocx link status --json shows tunnel.lastFailure.cause.

Security summary

This PR touches the SSH tunnel and link authentication boundary.

• Unchanged: the relay credential boundary, caller-credential stripping, the route tables, host-key policy and the ssh argv.
• New unauthenticated trigger. GET /readyz on a link-mode Child can trigger probeLinkRelayPreflight to 127.0.0.1:<tunnelPort>. It sends only what each relayed request already sends first: the key id, the link id, a fresh nonce, the caller HMAC proof derived from the key fingerprint, and the version/feature report. It sends no link key, Authorization header, data request or body, and it never reads the response body. A response counts as ready only when a listener proof verifies with timingSafeEqual. It runs at most once per 5 s, in a single flight. The test asserts that the fake Home never sees the key or an auth header.
• New outputs carry fixed words and numbers only. The /readyz link.reason, the tunnel status field and the tunnel_transition records hold no ssh stderr, argv, alias, host name, key or account id. The diagnostics allowlist drops unknown fields, and the test writes an alias, an argv and stderr and checks that none of them reach disk. The tunnel field sits behind the authenticated /api/link/status (admin or dashboard session), like the rest of that document.
• Not added: no process is killed on either host, and no retry bypasses the host-key or auth limits. Auth keeps 5 min; a host-key failure stays terminal.
• bun run privacy:scan passed.

Verification

Linux x64, Bun 1.4.3, fresh isolated HOME/CLAUDE_CONFIG_DIR/OPENCODEX_HOME per run, heavy runs under flock /tmp/ocx-heavy-test.lock. Head: ad7a4822619ee2443d00896260dd6865bf8a6479 (the earlier full and changed runs used 9fea0149e, which differs only by one test-fixture alias string; the focused new tests were rerun on the final head).

• Focused, 27 files (the fix(link): recover preflight deadlines with bounded diagnostics #7491 regression set, link tunnel state/supervisor/history/readiness/status, CLI link, link management routes, child parity, proxy-liveness, core–Lab boundary): 742 passed, 3 skipped, 0 failed.

  bun scripts/test.ts tests/clients/link-diagnostics.test.ts tests/clients/client-link-relay.test.ts tests/clients/link-relay-bound-transport.test.ts tests/clients/client-link-tunnel.test.ts tests/clients/client-runtime.test.ts tests/clients/client-link-runtime.test.ts tests/clients/client-machine-listener.test.ts tests/server/port-reclaim.test.ts tests/test-layout.test.ts tests/test-layout-tooling.test.ts tests/clients/client-runtime-restart.test.ts tests/clients/link-parity-reporter.test.ts tests/clients/link-peer-compatibility.test.ts tests/clients/client-home-unreachable.test.ts tests/windows/windows-secret-acl.test.ts tests/windows/windows-secret-acl-removal-flight.test.ts tests/clients/link-tunnel-state.test.ts tests/clients/link-supervisor.test.ts tests/clients/link-tunnel-history.test.ts tests/clients/link-readiness.test.ts tests/clients/client-link-status.test.ts tests/clients/link-status-projection.test.ts tests/cli/cli-link.test.ts tests/server/link-management-routes.test.ts tests/server/link-child-parity.test.ts tests/lab/core-lab-boundary.test.ts tests/server/proxy-liveness.test.ts
  bun scripts/test.ts tests/cli/cli-ready.test.ts   # 57 passed, 0 failed

• New tests (registered in scripts/test-layout/layout-clients.json and tests/fixtures/test-layout-expected.json):
  • tests/clients/link-tunnel-history.test.ts covers the incident sequence on a fake runner and manual clock: connected, Broken pipe, stale remote forward, doubling retries, then healed. It checks the exact diagnostic records, the tunnel DTO, the retried missing listener port, a terminal host key recorded once, the on-disk allowlist, the opt-in route and CLI validation.
  • tests/clients/link-readiness.test.ts covers the Child-initiated mapping table, single-flight/TTL/bounded wait with deferred promises (no sleeps), a real preflight against a fake Home (ok, auth_failed, unrecognized, unreachable, with no key sent), and the Child /readyz 503/200 bodies checked against validateReadyzBody.
• Changed tests. link-tunnel-state and link-supervisor expectations moved from the fixed minute to the doubling delay and now expect detail/retries. Red check: the updated copies of those two files, run against the carry head 6961751d2 (the code before this PR's own changes), give 41 passed, 8 failed. The failures are the classification, doubling cadence, retries/detail and spawn-failure cadence tests. The missing-listener retry lives in the new history test, which needs the new APIs and so cannot run against the old code.
• bun run test:changed (1619 files): 35577 passed, 79 skipped, 13 failed. All 13 failures are in tests/cli/ocx-launcher-runtime.test.ts, tests/codex-integration/codex-shim-{fnm,readiness,standalone}.test.ts and tests/gui/gui-pair-client.test.ts. The same 13 tests fail identically on a clean detached origin/dev (5f7f7db57) worktree in this container (105 passed, 2 skipped, 13 failed across those 5 files), so they come from the environment (launcher/Bun PATH discovery and the private-home write check), not from this PR.
• bun run test (full, 2554 files in the parallel phase): 50987 passed, 136 skipped, 29 failed; the serial phase that follows passed. The 29 failures are the 13 above, plus 15 in tests/config/serving-runtimes.test.ts, tests/ci-workflows/bun-runtime.test.ts and tests/claude-integration/claude-desktop-remote-hub.test.ts, which fail identically on clean origin/dev (60 passed, 15 failed on both trees for those files), plus authenticated reply-command forgery never reaches native queue in tests/codex-integration/messaging-remote-{gaps,admission}.test.ts. That last test failed only under full-suite load and passed when rerun focused on this branch. This PR changes no messaging code.
• bun run typecheck, bun run privacy:scan, bun run structure:check, bun scripts/file-size-ratchet.ts, bun run skill:surface:check and git diff --check: all passed.
• cd docs-site && bun install --frozen-lockfile && bun run build: passed, 593 pages and 84,784 internal links checked.
• NOT RUN:
  • native macOS and Windows runs; signal-path and ACL behavior is covered only by the synthetic Windows runners;
  • GUI lint (no gui/ change);
  • hosted CI.
  • The incident itself was not reproduced against real sshd/ssh; the tests use a fake runner and fake Home listeners. I did not touch the user's live ~/.opencodex, the affected Child or any real link.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

Summary by CodeRabbit

• New Features

  • Link status can include SSH attempt counts, next retry times, recent tunnel state changes, and failure details when diagnostics are requested.
  • Readiness checks now report whether a Remote Link can carry requests, with an availability reason when it cannot. Process health checks remain separate.
  • Bounded link diagnostic records help investigate connection and recovery issues.

• Bug Fixes

  • Timeout and forwarding failures now retry with increasing delays, starting at one minute and capped at five minutes. Authentication failures continue to retry every five minutes; changed host keys are not retried.

• Documentation

  • Expanded Remote Link guidance with readiness behavior, retry timing, diagnostics, and troubleshooting steps.

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📒 Files selected for processing: 12

• src/cli/link.ts
• src/client/link-relay-transport.ts
• src/client/link-tunnel.ts
• src/link/relay-auth.ts
• src/link/supervisor.ts
• src/link/tunnel-state.ts
• src/server/index/link-relay-sessions.ts
• structure/remote-link.md
• tests/clients/client-link-tunnel.test.ts
• tests/clients/link-readiness.test.ts
• tests/clients/link-relay-bound-transport.test.ts
• tests/clients/link-supervisor.test.ts

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📝 Walkthrough

Priority: ➖ Normal

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 13ae6

The CLI status type now includes optional tunnel diagnostics. No actionable merge-blocking issue remains after normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 47.89% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 71 functions across 32 files. (1 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly summarizes the main changes: Home tunnel retry recovery, Child link readiness reporting, and tunnel diagnostics.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 47.89% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 71 functions across 32 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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Reviewed commit: ad7a482261

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Actionable comments posted: 2

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src/cli/link.ts:
- Line 193: Update the exported LinkStatusPayload type to declare an optional
tunnel field using LinkTunnelDiagnostics, so its links entries accurately
describe the value added by validateStatus and consumers can access it without a
cast.

Review comments at @src/client/link-relay-transport.ts:
- Around line 182-209: Update probeLinkRelayPreflight’s authentication request
to identify it as probe-only, and have the Home relay authentication flow
recognize that marker without creating a session or drain lease. Preserve
session reservation for normal two-step authentication so readiness probes
cannot occupy session capacity or delay drain.

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• docs-site/src/content/docs/fr/guides/remote-link.md
• docs-site/src/content/docs/guides/remote-link.md
• docs-site/src/content/docs/ja/guides/remote-link.md
• docs-site/src/content/docs/ko/guides/remote-link.md
• docs-site/src/content/docs/reference/cli/lifecycle.md
• docs-site/src/content/docs/ru/guides/remote-link.md
• docs-site/src/content/docs/tr/guides/remote-link.md
• docs-site/src/content/docs/zh-cn/guides/remote-link.md
• docs-site/src/content/docs/zh-tw/guides/remote-link.md
• scripts/test-layout/layout-clients.json
• src/cli/link.ts
• src/client/link-ingress.ts
• src/client/link-readiness.ts
• src/client/link-relay-transport.ts
• src/client/link-relay.ts
• src/client/link-tunnel.ts
• src/client/machine-listener.ts
• src/client/runtime.ts
• src/link/diagnostics.ts
• src/link/status-projection.ts
• src/link/supervisor.ts
• src/link/tunnel-history.ts
• src/link/tunnel-state.ts
• src/server/index/optional-listeners.ts
• src/server/management/link-routes.ts
• src/server/port-reclaim.ts
• structure/gui-and-management-api.md
• structure/remote-link.md
• tests/cli/cli-link.test.ts
• tests/clients/client-home-unreachable.test.ts
• tests/clients/client-link-relay.test.ts
• tests/clients/client-link-runtime.test.ts
• tests/clients/client-link-tunnel.test.ts
• tests/clients/client-machine-listener.test.ts
• tests/clients/client-runtime.test.ts
• tests/clients/link-diagnostics.test.ts
• tests/clients/link-readiness.test.ts
• tests/clients/link-relay-bound-transport.test.ts
• tests/clients/link-supervisor.test.ts
• tests/clients/link-tunnel-history.test.ts
• tests/clients/link-tunnel-state.test.ts
• tests/fixtures/test-layout-expected.json
• tests/server/port-reclaim.test.ts

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