Phase 4D. The first non-default CronScheduler: plugins/cron/chronos/. Inert
unless cron.provider=chronos; resolve_cron_scheduler falls back to the built-in
if unavailable, so cron never loses its trigger.
Files:
- chronos/__init__.py — ChronosCronScheduler + register(ctx).
* is_available(): config-only, NO network (portal_url + callback_url + a
stored Nous access token via get_provider_auth_state). Returns False →
resolver falls back to built-in.
* start(): reconcile() then RETURN — no blocking loop, no 60s wake (DQ-1:
this is what makes scale-to-zero real; the machine wakes only on a
NAS→agent fire).
* _arm_one_shot(job): POST NAS provision {job_id, fire_at, agent_callback_url,
dedup_key=job_id:fire_at}. Agent owns the time → sub-minute fires survive
(no scheduler 1-minute floor).
* reconcile(): converge NAS arms toward jobs.json — arm missing/changed-time,
cancel orphaned, skip paused. Cold process rebuilds from jobs.json +
idempotent dedup_key.
* on_jobs_changed(): reconcile (re-arm/cancel the affected one-shot).
* fire_due(): ABC default (CAS claim + run_one_job) THEN re-arm the next
one-shot. Job gone (one-shot done / repeat-N exhausted) → no re-arm.
- chronos/_nas_client.py — thin HTTP wrapper for provision/cancel/list using
the agent's existing refresh-aware Nous token (resolve_nous_access_token).
Names no scheduler vendor; holds no scheduler creds.
- chronos/plugin.yaml — discovery metadata.
INVARIANT: zero "qstash"/"upstash" hits in plugins/cron, gateway, hermes_cli,
website/docs — the external scheduler is a NAS-internal detail, never named
agent-side.
Tests (13, all NAS mocked, zero network): is_available off-without-config +
on-with-config + makes-no-network; arm payload incl. sub-minute + noop without
next_run; reconcile arms-all / cancels-orphan / skips-paused / skips-already-
armed; fire_due re-arms next / no re-arm when job gone / no re-arm when claim
lost.
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