New global plugin with one SessionStart hook running all checks in-process
(hooks/checks.py, check(ctx) -> CheckResult, single registry). Three states:
ok (silent), note (near-zero-token line, never suppressed), warn (one
aggregated banner, once-per-day snooze + permanent suppress in gitignored
per-project .cc-os/). Initial checks: subagent-model-env-override (catches
the WS1 Cluster 1 incident deterministically), adr-system-present (verbatim
port of os-adr's hook, legacy .os-adr/suppress honored), vault-hub-note-present.
os-adr's own SessionStart hook moved here atomically (its hooks.json now
empty; session_start.py stays as wording source of record). Built via
OpenSpec change add-os-status-plugin; 36 model-free tests; smoke-tested
2026-07-06 incl. env-override canary.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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