# Phase 8 Execution Checklist

**Update 2026-08-07 (truth sweep):** This checklist previously read
"Status: Complete / Tests: All passing / Build: 0 errors, 0 warnings" — a
107-byte stub with no per-work-package results and no linked run. That claim
was **unevidenced** and was retired.

**Update 2026-08-15 (WP-4 run, evidenced):** The target-scale load test has now
actually been run, at full scale, with results published.

## WP-4 — Load/Performance Testing at Target Scale

**Status: measured 2026-08-15.** Not a claim — a run.

- Scale executed: **10 sites × 500 instances × 75 tags = 375,000 live tag
  subscriptions**, 37,518 tag updates/second achieved against 37,500 nominal
  (100.0%), **45,021,375 updates** offered over a 20-minute steady-state window.
- Headline results: end-to-end tag update latency **P50 0.88 ms / P99 4.57 ms /
  max 37.41 ms**; **zero events dropped** at 100 live stream subscribers; health
  report collect+ingest **P99 0.31 ms** with 10/10 sites tracked centrally;
  debug view snapshot under load **P99 2.19 ms with 0 timeouts**; 500 instances
  deployed to a site in **2.6 s**; CPU **2.9% of the box**; working-set slope
  **+8.83 MB/min**.
- **11 clean passes, 1 pass with a documented caveat, 0 failures.**
- Deferred-work register **#25** and **row 50** are closed by this run.

**Results:** `2026-08-15-target-scale-load-test-results.md` — per-criterion
numbers vs thresholds, three findings (F1 memory-window limitation, F2 the S&F
retry-interval wait, F3 slow-subscriber isolation), and an explicit "what this
does not prove" section.

**Design, thresholds and deviations:**
`2026-08-15-target-scale-load-test-design.md` — including the documented
deviation from the protocol's 1-hour sustained window to 20 minutes, and the
command for the full 1-hour version.

**Harness:** `tests/ZB.MOM.WW.ScadaBridge.LoadHarness/` (standalone executable),
with a CI-scale smoke `[Fact]` at
`tests/ZB.MOM.WW.ScadaBridge.PerformanceTests/TargetScale/TargetScaleHarnessSmokeTests.cs`
so the evidence can be regenerated rather than bit-rotting.

**Still open within WP-4** (not covered by this harness — central-cluster and
browser concerns): `[xc-3]` site event logging volume within 30-day/1 GB limits,
`[xc-4]` audit logging not degrading central, `[xc-5]` template
flattening/validation for large templates, `[xc-8]` UI workflow responsiveness.

See `phase-8-production-readiness.md:152-170` (WP-4) and `:314-320`
(test protocol) for the original scope.