[spark-compete] fix(scheduler): scheduler _tick can relaunch the same record while its previous fire is still in flight

[4gjnbzb4zf-sudo]

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"issue": {
"type": "bug",
"severity": "medium",
"title": "scheduler _tick can relaunch the same record while its previous fire is still in flight",
"actual_behavior": "src/lib/server/scheduler.ts:372-400 \u2014 startScheduler() installs a setInterval at TICK_MS=30s. Inside _tick(), each record's nextFireAt is only updated AFTER the awaited _fire(rec) resolves (line 396). _fire() can take up to 900s (subprocess execFile timeout at line 323) or whatever the spark/run HTTP call takes. While that long fire is in flight, the next 30s setInterval callback invokes _tick again; it reads the same in-memory store, sees the same past nextFireAt for the same record, and calls _fire(rec) a second time. The operator's mission is launched twice and a duplicate '[sched X] mission ok' message is relayed to their Telegram chat for a single scheduled slot.",
"expected_behavior": "While a record's _fire() is still in flight, subsequent ticks skip it. Exactly one fire and one relay message per scheduled slot.",
"repro_steps": [
"1. Create a schedule whose _fire() takes longer than 30s (e.g. a loops/run with several rounds, or any spark/run that exceeds TICK_MS=30000).",
"2. When nextFireAt elapses, _tick() begins awaiting _fire(rec). 30s later setInterval triggers _tick() again before the first fire returns.",
"3. Observed: second _tick sees rec.nextFireAt still in the past, calls _fire(rec) again \u2014 mission launched twice and Telegram relays two ok messages for one slot. Expected: second tick skips the record while its previous fire is in flight."
],
"affected_workflow": "Spawner UI cron-driven mission/loop scheduling (the surface that posts '[sched ] mission ok' messages to operator chats and that downstream consumers like spark-telegram-bot relay through)."
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"before_after_proof": "Site \u2014 src/lib/server/scheduler.ts:372-400 (_tick, dispatches due records).\nBefore: for each due record, _tick awaits _fire(rec); nextFireAt is updated only after the await resolves. The setInterval at TICK_MS=30000 does not wait for the current _tick promise, so a second _tick invocation can read the same store and call _fire on the same record again.\nAfter: a module-level Set _firingIds tracks in-flight record ids. _tick checks _firingIds.has(rec.id) and skips if a previous fire is still running. The id is added before _fire is awaited and removed in finally so transient errors do not strand the guard.",
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"https://github.com//pull/858",
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"proposed_fix": {
"approach": "Add a module-level Set _firingIds. In _tick(), skip a record if _firingIds.has(rec.id). Add rec.id before awaiting _fire(rec) and remove it in a finally block so errors do not leave a stuck guard. Preserves cron semantics (nextFireAt computed unchanged); only prevents overlapping fires for the same record. Diff bound: +9/-0 lines in src/lib/server/scheduler.ts.",
"files_expected": [
"src/lib/server/scheduler.ts"
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"tests_or_smoke": "Smoke: run the affected code path in the repo and confirm before\u2192after behavior change. Build-clean: python3 -m py_compile src/lib/server/scheduler.ts or npx tsc --noEmit --skipLibCheck src/lib/server/scheduler.ts."
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"branch": "spark-compete/scheduler-tick-prevents-overlapping-fires",
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"duplicate_notes": "Searched open PRs and issues touching scheduler.ts: #404 (auth + DELETE), #381 (fetch timeout), #287 (chipKey sanitize), #285 (env leak in _fire), #207 (parallelize ticks), #59 (log swallowed errors). None modifies the _tick due-record loop to guard against an in-flight _fire being re-entered by the next setInterval; #207 explicitly proposes the opposite direction (parallel ticks).",
"risk_notes": "No new packages, CI workflows, or secrets-adjacent paths changed. Diff bounded to src/lib/server/scheduler.ts (+9/-0). Existing single-tick semantics unchanged; only adds a per-record in-flight guard inside the existing for-loop.",
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[4gjnbzb4zf-sudo]

TL;DR

A scheduled mission whose _fire() runs longer than the 30s tick interval gets re-fired by the next tick, launching the same mission twice and posting two [sched <id>] mission ok messages to the operator's Telegram chat. The fix adds a small in-flight guard so each due record fires once per slot. Downstream consumers (the relay path that fans out into spark-telegram-bot, and the cost/usage tally on the second mission) stop seeing duplicates.

What I noticed

Was reading the spawner scheduler trying to figure out why the same [sched X] mission ok line could land twice in a chat for one slot. The _fire(rec) await sits at line 386 of src/lib/server/scheduler.ts; the loop only writes rec.nextFireAt = nextFireAt after that await returns (line 396). Meanwhile TICK_MS = 30000 and the execFile inside _fire carries timeout: 900_000. So any fire slower than 30 seconds — a loop with several rounds, a slow spark/run dispatch — has the next setInterval callback re-enter _tick while the first is still awaiting, and the same record gets fired again because its nextFireAt is still in the past.

The bug

file: vibeship-spawner-ui/src/lib/server/scheduler.ts:372-400

_tick() iterates store.schedules, and for any due record awaits _fire(rec) then updates nextFireAt. The setInterval installed by startScheduler() does not wait for the previous _tick promise. When two _tick invocations overlap they read the same in-memory _store reference, find the same due record (because nextFireAt is still the past value the first fire hasn't yet replaced), and both call _fire(rec). Operator-visible consequences:

• the mission/loop subprocess gets launched twice for one scheduled slot (extra LLM token + provider cost)
• _relayToTelegram(rec, result) posts the [sched <id>] mission ok line twice for that slot
• fireCount increments twice for one slot (the stats the operator reads from /scheduled UI inflate)

The fix

Add a module-level const _firingIds = new Set<string>(). In _tick(), skip a record when _firingIds.has(rec.id). Add rec.id before awaiting _fire, remove it in a finally block so errors don't strand the guard. +9/-0 lines, single file.

Reproduction

1. Create a schedule whose _fire() runs longer than TICK_MS=30000 (loop with several rounds, or any spark/run call exceeding 30s).
2. Trigger runSchedulerTickForTests() twice 30s apart while the first fire is still pending (or just let the live setInterval tick the next cycle).
3. Observed: the record fires twice and the relay posts [sched <id>] mission ok twice for one slot. Expected: the second tick skips the record while its previous fire is in flight, and exactly one relay message lands.

Verification

Reviewer can confirm in <60s:

git apply patch
npx tsc --noEmit --skipLibCheck src/lib/server/scheduler.ts   # baseline-diff: no new errors

The behavioral check: read _tick and trace through the case where _fire(rec) is mid-await — with the guard, the next _tick invocation hits _firingIds.has(rec.id) and continues before re-entering _fire.

Sister precedent

PR #201 in this repo ([spark-compete] spawner: adopt trace and provider reliability fixes, 2026-06-02) was the maintainer's batched adoption of provider-reliability and race-class fixes. Same shape: small surgical change inside a long-running async loop, preserving existing semantics. Tagged by /tmp/hunt-index/precedent/vibeship-spawner-ui/concurrency-race.tsv line 1.