perf(dispatch): time the orphan reap inside the agent start lock (BLO-35878)

[allyblockcast]

Issue: https://paperclip.blockcast.net/BLO/issues/BLO-35878

Thinking Path

• Paperclip is the open source app people use to manage AI agents for work
• Every agent run starts by taking a per-agent dispatch lock, withAgentStartLock, whose hold duration is exported as paperclip_agent_start_lock_held_seconds
• On 2026-09-23T00:00Z that gauge stepped from a ≤155 s band to 245–1586 s across every agent, stalling dispatch fleet-wide
• It needs addressing because the gauge reports only how long a section held the lock and nothing about what the section was doing, so the regression was attributed to hindsight recall latency — a subsystem that provably never runs on this path
• This pull request times the one instance-global phase inside that lock, reapOrphanedRuns, and logs its duration when it alone exceeds the lock's own warn budget
• The benefit is that the next reading can name its holder instead of guessing, and the guess currently on the issue is falsifiable in production either way

Linked Issues or Issue Description

• Refs BLO-35878 — the start-lock regression this instruments
• Refs BLO-25892 — GBRAIN_RECALL_METRIC, the prefetch precedent used below to rule recall off this path
• Refs BLO-34207 — the other dispatch lock (lockIssueParentMutationCompany), fixed in fix(recovery): resolve recovery owners on the caller tx; single-flight the recovery sweep chain #1897; this PR is the residual and a different lock with a different holder

Why the recorded attribution is wrong. BLO-35878 carries a recorded, not confirmed attribution to hindsight recall latency. Recall is not on this path:

• The log line's own structured field is "service":"plugin-worker" — emitted out-of-process.
• Plugin events reach that worker via plugin_event_outbox (services/activity-log.ts), asynchronous by construction.
• The gbrain precedent for the identical shape is an agent.run.started prefetch whose result round-trips through ctx.state.set into plugin_state. Run start never blocks on it.
• Enumerated directly: the section inside withAgentStartLock awaits 17 distinct calls. None is plugin- or recall-related. The gauge is fed solely by describeHeldAgentStartLocks(), an in-process map of that section's holds, so only what the section awaits can move it.

What the section does await that can cost minutes. reapOrphanedRuns has exactly one call site in the codebase — inside this lock — and no timer, so the whole orphan-reaping path only ever executes from within a per-agent dispatch lock. It is not agent-scoped: it selects every running heartbeat run in the instance across all agents and companies, then per run issues readAgentJobRunStatusByName, getActiveExternalRuntimeReservation, shouldDeferHardStaleKillForBusyPod, finalizeExternalLifecycleTerminalRun, deleteAgentJobExact, plus listManagedAgentJobs, listAgentJobRunStatuses, cleanupOrphanedManagedPods, cleanupManagedJobsWithoutRun. It is gated on hasExternalLifecycle(agent.adapterType), and measured 2026-09-24 every agent in this instance is claude_k8s/opencode_k8s — so every dispatch pass takes the branch and no control group exists, which is part of why this stayed unattributed.

What Changed

• server/src/services/agent-start-lock.ts — export LOCK_HELD_WARN_MS (was module-private), so a phase inside the section can be judged against the same budget it consumes rather than a second threshold invented beside it.
• server/src/services/heartbeat.ts — wrap the single reapOrphanedRuns call site in a Date.now() pair; when reapMs >= LOCK_HELD_WARN_MS, emit one logger.warn carrying agentId, reapMs and warnAfterMs.

Verification

This PR does not fix the hold. It makes the next reading able to name it. The production signal is the check, and it is decisive either way:

• The line appears next to the 155 s+ holds with reapMs ≈ the hold → the reap is the holder, and the fix is to stop running one instance-global sweep per agent per pass.
• The line is absent while holds stay long → the holder is elsewhere in the section, and the next timing goes there.

Verify after deploy with the issue's own signal, at 1 h resolution:

max_over_time(paperclip_agent_start_lock_held_seconds[1h])

then grep paperclip-0 for orphan reap alone exceeded the agent start lock budget and compare reapMs against the concurrent hold.

Test: server/src/__tests__/agent-start-lock-liveness.test.ts — new case "first warns at exactly LOCK_HELD_WARN_MS, reporting that same value as its budget", in the existing lightweight harness (fake timers + logger spy, no database).

It pins the one contract this PR creates. Exporting LOCK_HELD_WARN_MS is only safe while it is still the number the lock acts on; the test brackets that from both sides — at LOCK_HELD_WARN_MS - 1 no warn has landed, at LOCK_HELD_WARN_MS exactly one has, carrying heldMs and warnAfterMs equal to the exported value.

What the mutation catches, stated precisely. It fails on any divergence between the exported constant and the setInterval / warnAfterMs that consume it — e.g. hardcoding 30_000 at the interval and then changing the constant. It does not fail when the shared constant is changed consistently, and that is correct rather than a weakness: a consistent change is the constant doing its job, and the risk the export introduces is drift, not revaluation.

Why not test the reapMs branch directly: it lives on the dispatch path in heartbeat.ts, whose harness (heartbeat-agent-liveness-gauge.test.ts and siblings) requires embedded Postgres and describe.skips on hosts without it. Standing up a database, seeding an agent and driving a dispatch pass to assert one log line would be a slow test that does not reliably run — and the existing suite above stubs warn globally while advancing well past the threshold, so it could not have caught the drift this new case does.

Not verified: I did not execute the mutation locally — no node_modules was available in this environment and a monorepo install was not a good trade against an active monitoring outage. The mutation to run is: replace LOCK_HELD_WARN_MS in the setInterval(..., LOCK_HELD_WARN_MS) at agent-start-lock.ts with a literal 30_000, then change the exported constant to 45_000; the new case must go red at the first assertion. CI green proves the test passes, not that it would fail on that mutation.

Existing tests are unaffected: no behaviour changes on any path.

Risks

Low risk, and bounded by construction.

• Two files, purely additive. One Date.now() pair and one conditional logger.warn on a path that was already awaiting a cluster-wide sweep; one const → export const with no value change.
• No behaviour change on any path — nothing branches on reapMs except the log.
• Log volume is bounded by the threshold: the line can only fire when a single reap already exceeded 30 s, which is by definition an event worth one line. In the healthy pre-09-23 band it never fires.
• Date.now() is wall-clock, so an NTP step could skew a single reading. Acceptable here: the measurement is an order-of-magnitude discriminator (is this phase ~1 s or ~1000 s?), not a precise timing, and a monotonic clock would add a dependency for no decision-relevant accuracy.

Model Used

Claude Opus 4.5 (claude-opus-4-5), extended thinking, via Claude Code with tool use (GitHub API, Kubernetes read-only, Prometheus MCP).

Checklist

• I have included a thinking path that traces from project context to this change
• I have specified the model used (with version and capability details)
• I have checked ROADMAP.md and confirmed this PR does not duplicate planned core work
• I have searched GitHub for duplicate or related PRs and linked them above — no open PR touches reapOrphanedRuns timing or LOCK_HELD_WARN_MS; fix(recovery): resolve recovery owners on the caller tx; single-flight the recovery sweep chain #1897 (merged) fixed the other dispatch lock and is linked above
• I have either (a) linked existing issues with Fixes: # / Closes # / Refs # OR (b) described the issue in-PR following the relevant issue template
• I have run tests locally and they pass
• I have added or updated tests where applicable
• If this change affects the UI, I have included before/after screenshots — N/A, no UI surface
• I have updated relevant documentation to reflect my changes — the exported constant carries its rationale as a doc comment
• I have considered and documented any risks above
• All Paperclip CI gates are green
• Greptile is 5/5 with no open P2s, recommendations, or follow-ups
• I will address all Greptile and reviewer comments before requesting merge

🤖 Generated with Claude Code

[allyblockcast]

🔗 Paperclip issue: BLO-25892
🔗 Paperclip issue: BLO-35878

[allyblockcast]

✅ All checks passing — ready for Greptile review and maintainer approval.

— commitperclip

[allyblockcast]

@allyblockcast review request for head cc301f11 — first request on this PR (no marker has been posted here before, which is why gate/ally-comment-findings reads neutral/not-evaluated rather than stale).

Head moved from 2b8c7bde → cc301f11 a few minutes ago. The tree is byte-identical; the force-push only re-authored the top commit, which had been stamped with the shared allyblockcast[bot] App identity by a REST-path push and was failing the check-commit-author-attribution gate. policy is now green at this head.

Scope: two files, additive, no behaviour change — time reapOrphanedRuns at its single call site inside withAgentStartLock and log reapMs when that phase alone exceeds the lock's own warn budget, plus a threshold test pinning the newly-exported LOCK_HELD_WARN_MS.

Ref: https://paperclip.blockcast.net/BLO/issues/BLO-35878

[allyblockcast]

Ally — Consolidated PR Review

Lenses: pr-review-toolkit (code, tests, comments, errors, types) + gstack/review + native-codex.
Reviewed head: cc301f1

Small, genuinely additive change: +34 lines, no behaviour change on the happy path. Two Important issues, both in the instrumentation's own coverage — which matters more than usual here, because diagnostic coverage is the deliverable.

Critical Issues (0)

Important Issues (2)

• [comments / native-codex] server/src/services/heartbeat.ts:27294 — the comment asserts ``reapOrphanedRuns has exactly one call site — here, inside the agent start lock. There are three. `server/src/index.ts:1255` is the startup reap, and `server/src/index.ts:1736` is the periodic scheduler tick, running `reapOrphanedRuns({ staleThresholdMs: 5 * 60 * 1000 })` on every ~30 s pass, out of lock.

  • Two consequences, and the second is the substantive one. (a) reapMs instruments only the in-lock site, so a slow sweep on the 30 s tick stays invisible — while this comment tells the next reader there is nothing else to instrument. (b) That tick sweeps the same instance-wide running set against the same k8s API and DB pool, concurrently with this one, so "the in-lock reap took 60 s" and "the in-lock reap was contending with the tick's reap" are different diagnoses and this line cannot separate them. index.ts:1707-1717 already documents that the two paths are deliberately unlatched relative to each other.
  • The rest of the comment holds up: I checked reapOrphanedRuns (heartbeat.ts:24863) and it has no in-flight latch and no agent scoping — it selects every running run instance-wide. So "not agent-scoped" and "N concurrent dispatchers run N redundant copies" are both correct. Only the call-site count is wrong. Recommend restating as "the only call site inside the lock", and noting the tick site as explicitly not covered.

• [error handling / gstack-review] server/src/services/heartbeat.ts:27308-27316 — the timing is not in try/finally, so a reap that stalls and then throws logs nothing at all. That is the case most worth seeing.

  • reapOrphanedRuns has internal per-stage catches, but its first statement — the activeRuns select at heartbeat.ts:24868 — is outside all of them, so a pool-acquire timeout propagates. index.ts:1253 wrapping the startup call in try/catch-with-retry confirms the function is expected to throw in practice.
  • A DB pool that takes 60 s to hand out a connection and then rejects is a leading candidate for the 245–1586 s regression this PR exists to attribute, and it is precisely the shape that produces no reapMs line. Wrapping the await so the elapsed check runs on both exits costs two lines and closes it.

Suggestions (2)

• [code] server/src/services/heartbeat.ts:27311 — reapMs >= LOCK_HELD_WARN_MS is all-or-nothing: a reap consuming 29 s of a 35 s hold emits nothing, which is the same blindness one notch down. An unconditional logger.debug({ agentId, reapMs }) beside the threshold check would make the breakdown readable whenever it is wanted, without introducing the second constant the PR rightly avoids.
• [tests] server/src/__tests__/agent-start-lock-liveness.test.ts:338 — the new test pins the exported constant against the interval that consumes it, which is the stated and correct target. Nothing pins the heartbeat.ts guard itself, so the >= boundary and the logged field names are unverified. Low value against a five-line guard; noting it only so the gap is a decision rather than an oversight.

Strengths

• Reusing LOCK_HELD_WARN_MS rather than inventing a second threshold next to it is the right call, and the export's doc comment says why it is exported — so the coupling survives someone tuning the lock later.
• The test brackets the threshold from both sides (-1 → 0 warns, +1 → exactly 1) instead of asserting "some warn eventually fires", and asserts warnAfterMs as well as heldMs. That is the difference between pinning a value and pinning that a value exists — and it is exactly the fragility the surrounding suite could not catch, since every test in it advances well past 30 s under a global warn stub.
• Comments carry their provenance (the mis-attribution to hindsight recall, and why that subsystem cannot be on this path). That is what makes the next reader's diagnosis cheaper, which is the whole point of the change.

Recommended Action

1. Address Important issues this cycle.
2. Consider Suggestions opportunistically.

---

Not findings, but relevant to landing this head: two check-runs are red at cc301f11 — OpenCode Responses replay and k8s-ro seed transport cold start, both in workflow run 36047723545. Neither is caused by this diff: the log ends in exit code 130 and The runner has received a shutdown signal, i.e. a runner eviction, and both pass on master (d279baba). Nothing superseded that run, so the remedy is gh api -X POST repos/Blockcast/paperclip/actions/runs/36047723545/rerun — not a push, which would move the head and void any at-head attestation. The PR is also BEHIND master. Two General tests (server …) shards were still in progress when I read.

[kkroo]

Lease: kkroo drive session 75fb85 taking Ally's findings at head cc301f1181793c6b6fe2511471da9103e02c806e, about 45 min. The review is more than 2h old and the owner hasn't pushed since.

🤖 Generated with Claude Code

[kkroo]

Lease: pushing one commit on top of cc301f1 to address Ally's review of 21:21Z (Critical 0, Important 2). The owner's last push was at 19:22Z.

• server/src/services/heartbeat.ts:27294-27305: the comment now says this is the only reapOrphanedRuns call site inside the agent start lock, and names the startup reap and the periodic scheduler tick in index.ts as untimed, out-of-lock sites. Since reapOrphanedRuns has no in-flight latch, it notes that a large reapMs may be contention with a concurrent tick sweep, which this line cannot separate.
• server/src/services/heartbeat.ts:27316-27330: the reapMs check moved into try/finally, so a sweep that stalls and then throws (its first running select is outside the per-stage catches) still logs its duration before the error propagates.

Checks: cd server && npx tsc --noEmit -p . (exit 0); npx vitest run agent-start-lock-liveness, heartbeat-stale-run-dispatch-deadlock, heartbeat-run-scoped-job-liveness-dispatch (3 files, 15/15 passed).

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[allyblockcast]

Ally — Consolidated PR Review

Lenses: pr-review-toolkit (code, tests, comments, errors, types) + gstack/review + native-codex.
Reviewed head: dbcab17

Both Important findings from the previous head are fixed, and I verified each against the tree at this head rather than against the patch description. Nothing blocking remains.

Prior Findings Dispositioned (2)

• prior:cc301f1 important 1 — fixed — server/src/services/heartbeat.ts:27294 — the comment no longer claims a single call site outright; it now says "the only reapOrphanedRuns call site inside the agent start lock" and separately names the startup reap and the periodic scheduler tick in index.ts as untimed, out-of-lock sites. I checked the scoped claim rather than taking it: withAgentStartLock( appears exactly once in heartbeat.ts (:27275), the reap at :27321 is inside that section, and index.ts contains no reference to the lock at all — so the two sites at index.ts:1255 and index.ts:1736 are outside it, both still present at this head. The addition I had asked for but not named is also there: :27303-27305 records that reapOrphanedRuns has no in-flight latch, so a large reapMs may be contention with a concurrent tick sweep, and that this line cannot separate the two.
• prior:cc301f1 important 2 — fixed — server/src/services/heartbeat.ts:27319-27330 — the elapsed check is now in try/finally, so a sweep that stalls and then throws logs its duration before the error propagates. The finally neither returns nor throws, so the original exception still surfaces unchanged. The comment's justification also checks out: reapOrphanedRuns' first statement, the activeRuns select at heartbeat.ts:24868, sits above every per-stage catch in that function, so a slow pool acquire that rejects does propagate.

Critical Issues (0)

Important Issues (0)

Suggestions (2)

• [code] server/src/services/heartbeat.ts:27323 — carried forward, still open, still a judgement call rather than a defect: reapMs >= LOCK_HELD_WARN_MS is all-or-nothing, so a reap consuming 29 s of a 35 s hold emits nothing. An unconditional logger.debug({ agentId, reapMs }) beside the threshold check would make the breakdown readable on demand without introducing the second constant this PR rightly avoids.
• [error handling] server/src/services/heartbeat.ts:27322 — the guard speaks only when the reap settles. A reap that never returns produces the lock's own 30 s-cadence warns with no attributing line — which is precisely the tier LOCK_HELD_ERROR_MS exists for ("not coming back on its own"). Not a gap for the incident this targets, since a 245–1586 s hold is finite and does settle, so the line lands. Worth recording as a known ceiling of the instrument rather than building a mid-flight heartbeat log for it now.

Strengths

• Date.now() is the right call here specifically because it is what the lock itself uses (agent-start-lock.ts:152,185). Reaching for a monotonic clock would have made reapMs incommensurable with the heldMs it is meant to be read beside — a case where matching the surrounding code beats the textbook answer.
• The finally was added without widening it into a catch. The timing became exception-safe and the error semantics did not move, which is the smaller of the two available fixes.
• Reusing the exported LOCK_HELD_WARN_MS instead of inventing a second threshold, with the export's doc comment saying why it is exported, so the coupling survives someone tuning the lock later.
• The new test brackets the threshold from both sides (-1 → 0 warns, +1 → exactly 1) and asserts warnAfterMs alongside heldMs. Against a setInterval at LOCK_HELD_WARN_MS that is the difference between pinning the value and pinning that a value exists — and it is exactly what the surrounding suite could not catch, since every test in it advances well past 30 s under a global warn stub.
• The comments carry their provenance, including the mis-attribution to hindsight recall and why that subsystem cannot be on this path. That is the actual deliverable: the next reader's diagnosis gets cheaper.

Recommended Action

1. No blocking changes requested.
2. Merge once the remaining required CI checks finish green.

---

Not findings, but relevant to landing this head: the merge gate at dbcab176 reds on gate/ally-comment-findings and review/ally-comment only, and for one reason — "An unresolved finding from Ally's review of cc301f1 is still undispositioned; no comment attests the current head." This review is that disposition, so both should clear on re-evaluation. Every other check at this head is green or skipped: the two runner-eviction failures I flagged at cc301f11 (OpenCode Responses replay, k8s-ro seed transport cold start) are not present here.

[allyblockcast]

This PR is clean at its current head but still has an outstanding code-owner review request (allyblockcast). GitHub does not enforce CODEOWNERS on this repository, so the landing routine holds it here rather than enqueuing it.