Enforce Coverage Configuration Invariants (codex)

[numnx]

🧩 Task: Enforce Coverage Configuration Invariants

Automated task PR opened by Code UX for T01.

📋 Summary

Sprint: Sprint 144 · QS: Coverage Observability and CI Reliability Audit · Task: T01

Create a repeatable coverage, observability, security, and CI reliability quicksprint by adding enforceable tests, CI/Playwright hardening, structured logging guarantees, and aligned operational documentation without lowering coverage thresholds.

📝 Full Task Prompt

## Objective
Close the current verification gap where coverage policy can drift in `vitest.config.ts` without a focused failure. The desired guarantee is that global thresholds, `coverage.include`, exclusions, deterministic env defaults, and the `src/server/activity-cache-service.ts` 80% line gate remain enforceable and are never lowered silently.

## Scope
- Edit `tests/backend/scripts/quality-guardrails.test.ts` or create `tests/backend/ci/vitest-coverage-policy.test.ts`
- Verify `vitest.config.ts`
- Verify `package.json` scripts: `test:backend:coverage`, `test:coverage`, and `ci`
- Relevant symbols/settings: `process.env.VITEST_IN_MEMORY_DB`, `process.env.TZ`, `coverage.thresholds`, `coverage.include`, `src/server/activity-cache-service.ts`

## Implementation Requirements
1. Add a focused backend Vitest test that reads `vitest.config.ts` and asserts `VITEST_IN_MEMORY_DB=true`, `TZ=UTC`, `LANG=C.UTF-8`, and `LC_ALL=C.UTF-8` are set before the config export.
2. Assert `coverage.include` contains `src/**/*.ts`, dashboard files are not included in backend coverage, and the global thresholds are at least the current values: lines 77.4, functions 71.5, branches 66.1, statements 76.0.
3. Assert the file-specific threshold for `src/server/activity-cache-service.ts` exists and keeps `lines` at least 80.
4. Assert `package.json` keeps `test:backend:coverage` using `vitest run tests/backend --coverage` and `ci` includes `pnpm run test:backend:coverage` without replacing it with a non-coverage command.
5. Keep the test implementation robust against formatting changes by parsing or narrowly matching stable config fragments instead of depending on exact whitespace.

## Constraints
- Do not lower any coverage threshold.
- Do not expand coverage to dashboard files unless the repository intentionally changes coverage architecture.
- Do not make assertions that depend on generated coverage output existing locally.
- Keep this task limited to coverage policy tests and any small helper needed by those tests.

## Verification
- Run `pnpm run test:backend -- tests/backend/ci/vitest-coverage-policy.test.ts` or the exact focused file created for this policy.
- Run `pnpm run test:backend:coverage` and confirm coverage thresholds still pass, including the `src/server/activity-cache-service.ts` 80% line threshold.
- Run `pnpm run lint` and confirm TypeScript passes with zero new errors.

✅ QA Review

⏳ QA review runs after this PR is opened. Check the task card in the dashboard for the outcome once it lands.

🤖 Model & Provider

Provider	Codex CLI
Model	gpt-5.5

⏱️ Timing

Started	2026-07-06 20:09:40 UTC
Finished	2026-07-06 20:13:02 UTC
Duration	3m 22s

📊 Token Usage

Metric	Value
Input tokens	62,064
Cached input tokens	596,992
Output tokens	5,242
Total tokens	664,298
Invocations	1
Tool calls	28
Active time	2m 54s

Included usage estimate (subscription/local login): $0.77

🌿 Branch Info

Base: feature/CODUX-144-qs-coverage-observability-and-ci-reliability-audit-4
Head: task/feature-codux-144-qs-coverage-observability-and--t01-codex-mr9nlwcn

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🤖 Generated by Code UX