## Summary
Addresses the remaining acceptance gap on #1120: a true **5-minute
rolling-baseline anomaly detector** for the Perf-page Write Sources
table. The endpoints + ingestor wiring + UI scaffolding landed in #1123
(partial); this PR replaces the ad-hoc tx-rate comparison with the
rolling baseline the issue actually asks for, and adds a JS unit test
that proves the ⚠️ flag fires at 11× baseline.
## What changed
- **`public/perf.js`** — new pure helper `detectPerfAnomalies(history,
current, opts)`. Computes per-component current rate and rolling
baseline rate over a window (default 5 min). Flags components whose
current rate > 10× baseline. Includes a 0.05/s floor so a stale `0`
baseline doesn't false-positive at startup.
- **UI** — Write Sources table now shows `Rate/s`, `Baseline/s`, and
`Anomaly` columns. Operators can sanity-check the ⚠️ rather than
trusting opaque output. History is kept on `window` and pruned to a
6-min sliding ring.
- **`test-perf-anomaly.js`** — new VM-sandbox test asserting:
- ⚠️ fires when one component runs at 11× its 5-min baseline
- No ⚠️ at 5× (under threshold)
- No ⚠️ until ≥30s of history has accumulated
## TDD evidence (red → green)
- Red commit `590f04d3`: introduces the stub `detectPerfAnomalies`
(returns empty `{flags:{}}`) + the test. Test FAILS on the
`assert(r.flags.backfill_path_json === true, ...)` assertion — not a
build error.
```
❌⚠️ fires when backfill rate hits 11× the 5-minute baseline:
expected backfill_path_json flagged at 11× baseline, got flags={}
2 passed, 1 failed
```
- Green commit `726a5e78`: implements the rolling-baseline detector. All
3 tests pass; existing `test-packet-filter.js` (79 tests) still green;
`cmd/server` Go tests for `/api/perf/*` still green.
## What is NOT in this PR (deferred / out of scope per brief)
- **SQLite-stats subsection** (WAL size + cache hit rate + pending
checkpoint) — `/api/perf/sqlite` already exists (landed in #1123). Issue
body lists it as a metric category, brief explicitly marks it OPTIONAL.
Not regressed; no changes needed.
- **Ingestor `/proc/self/io` bridge** — already lives in the ingestor
stats file (`ProcIO` field, `internal/perfio`) and is rendered on the
Perf page. No change.
- **Issue #1340** (SQLite write-lock instrumentation) — separate PR in
flight, not piggybacked.
- **No new metrics backend** (no Prometheus, no OpenTelemetry). Pure
JSON over `/api/perf/*`.
## Hard-rule compliance
- Files changed: 2 (`public/perf.js`, `test-perf-anomaly.js`) — well
inside the 3-files-outside-allowed-set cap.
- `Stats` struct unchanged.
- All colors via CSS variables — no hex literals introduced (grep
clean).
- TDD: red commit fails on assertion, green commit passes — visible in
branch history.
- PII preflight: clean on both commits.
Partial fix language deliberately not used — this completes the issue's
UI acceptance criterion. Leaving `Fixes #1120` off so the user can
verify on the staging deploy before closing.
---------
Co-authored-by: meshcore-bot <bot@meshcore>
