fix(cron): resilient file watcher + periodic reconciler (closes #15)

[nyem69]

Closes #15

Fixes the silent file-watcher drop where cron/jobs.json edits stopped being picked up by the live scheduler — leaving newly-enabled jobs with a sensible nextRun in /api/cron but lastRun: null forever (because the API computes nextRun via cron-parser independently of the live node-cron scheduler state).

Root cause

The single-file chokidar watch on cron/jobs.json:

• Watched a single inode → atomic-rename writes (vim, git checkout, many editors) unlink the inode and the underlying fs handle becomes invalid; chokidar silently stops emitting events.
• Only listened to change (atomic replaces emit unlink + add, not change).
• No error handler → any chokidar error was swallowed.
• Reload callback wasn't wrapped in try/catch → a throw inside would orphan the debounced chain.

Fix — two layers of defense

1. Resilient single-file watcher (gateway/watcher.ts)

New watchSingleFile() helper that watches the parent directory filtered to one file via ignored, with depth: 0. Directory watches persist across inode replacements. Listens to change and add, registers an error handler, wraps the callback in try/catch with logging. Applied to both config.yaml and cron/jobs.json — org/ and skills/ already watch directories and are naturally resilient.

2. Periodic reconciler (cron/reconciler.ts, new)

Every 5 min: loadJobs() → signatureOfJobs(jobs) compared to getScheduledSignature() (the sig of the last successful scheduleJobs pass, tracked in scheduler.ts). On divergence → reloadScheduler(jobs). Signature hashes id + schedule + timezone + engine + model + employee + prompt of enabled jobs only.

Why prompt is in the signature: runCronJob captures the job into its closure at schedule time, so a prompt-only edit must trigger reschedule for the live closure to pick it up. The reconciler relies on this — without it, prompt changes would be invisible until the next restart.

Timer .unref()s so it doesn't keep the process alive. Wired alongside startScheduler / stopScheduler in server.ts.

Verification

• typecheck: pnpm typecheck clean.
• tests: 7 new unit tests in cron/__tests__/reconciler.test.ts cover signature stability, order independence, disabled-job exclusion, schedule/prompt change detection, enable/disable transitions.
• full suite: 741/741 pass across 52 files — no regressions.

Test Files  52 passed (52)
     Tests  741 passed (741)

Files

Path	Change
packages/jimmy/src/cron/scheduler.ts	+ signatureOfJobs(), + getScheduledSignature(), track lastScheduledSig in scheduleJobs
packages/jimmy/src/cron/reconciler.ts	new — startCronReconciler() / stopCronReconciler() / tickReconciler()
packages/jimmy/src/cron/__tests__/reconciler.test.ts	new — 7 unit tests
packages/jimmy/src/gateway/watcher.ts	new watchSingleFile() helper; applied to config + cron watchers
packages/jimmy/src/gateway/server.ts	wire start/stop of the reconciler

Operational note

The PR doesn't remove the existing PUT /api/cron/:id workaround — that's still a valid per-job lever. The reconciler is the background safety net; the watcher fix should make manual reloads rarely necessary even on macOS+atomic writes.

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