Phase 3.4: Production Instrumentation Isolation

Status: ✅ Implementation and built-dist runtime validation complete
Issue: #119
PR: #122

Result

Standard ESM and CJS builds compile out all Cell, Text/Wrap, and Grapheme instrumentation hot-path dispatches. Source-mode profiling through Vitest/tsx remains available.

Structural evidence

pnpm run check:production-instrumentation-strip reads first-build metafiles emitted by tsdown/Rolldown and esbuild. It requires both modules to contribute zero output bytes:

• src/core/perf/instrumentation.ts: 0 bytes
• src/core/perf/instrumentation-noop.ts: 0 bytes

The same command runs a build-level control:

• B-style instrumentation-enabled build: real collector contributes 9,090 bytes and the control fails.
• C-style stripped build: real collector and no-op stub contribute 0 bytes and the control passes.

Missing ESM or CJS metafiles are hard failures.

Built-dist A/B/C runtime evidence

scripts/validate-built-dist-abc.ts uses isolated worktrees and actual built dist/vue.js, dist/core.js, dist/vue.cjs, and dist/core.cjs artifacts:

• A: 697472b0cc5c000fb46baf16e85c60d84ee22471
• B: 4d543ff7042f9c2400fa50a9dff921a0f36f77a3
• Built-dist C: ff1f2820c9d41893afc3af426a807afd3694f2af
• Packed-consumer C: 359896331846b254a82315d4f829a43ea30b2ac8
• Reviewed production/release-tooling head: ecf60023198e0353739273c168d5fb4012c4ea00

Commits after the two audit points changed validation/release tooling, result metadata, and build-metadata placement; they did not change production hot-path source behavior. The final branch head is independently covered by the first-build structural gates and current packed-package closure check.

Each measurement runs in a fresh Node child process. All six A/B/C permutations are used, timed batches calibrate toward 3 ms, and the primary C/A gate is the seeded bootstrap 95% CI of paired p50 ratios with upper bound <= 1.05.

All twelve ESM/CJS gates passed. After correcting the cycling-working-set scenario names, the widest passing upper bound is 1.0450 for the ESM CJK cycling working set.

Detailed raw observations and analysis: docs/perf/phase3.4-built-dist-abc.json.

Permanent release gates

release:check runs, after build:checked:

1. check:production-instrumentation-strip
2. check:consumer-bundle

The permanent check:consumer-bundle command is read-only and checks only the current packed package for instrumentation closure and forbidden temporary/metafile entries. The one-time validate:consumer-bundle-abc audit command compares independently packed historical A/B/C worktrees, reports minified raw/gzip/brotli sizes and module closure, and writes an audit file only when explicitly passed --output.

Source-mode correctness

The existing instrumentation API and tests continue to use the real collector when source files are loaded directly. Production stripping is deterministic and does not depend on environment variables.

Non-goals

This work does not change Cell cache capacity, eviction, long-text admission, provider caches, or virtual scrolling. Future optimization remains dependent on a real application workload profile.