Phase 3.3: Instrumentation Overhead Validation

Status: ✅ Complete — production strip validated and merged Related: #119 (closed), #122 (merged), #123 (real workload closure) Type: Performance validation (complete)

Objective

Validate that Phase 3 instrumentation hooks do not introduce unacceptable runtime or bundle-size overhead in the disabled state (production mode).

Comparison Points

Baseline (Commit A): 697472b0cc5c000fb46baf16e85c60d84ee22471

PR #115 merge (Phase 2 complete, before Phase 3)

Current (Commit B): 4d543ff7042f9c2400fa50a9dff921a0f36f77a3

PR #117 merge (Phase 3.1 + 3.2 complete, instrumentation disabled)

Methodology

Runtime Performance

Approach: Paired AB/BA benchmarks with bootstrap CI

Execution:

bash

pnpm run bench:overhead  # 30-60min

Method:

10 paired AB/BA runs in alternating order
Full Phase 2 baseline per run (warmup=50, samples=500)
Extract p50 and p95 from each run
Compute paired ratios per metric (B/A)
Bootstrap 95% CI on paired ratios (10,000 iterations, seeded)
Point estimate: median of paired ratios

Gating scenarios (9 pre-registered):

terminal_write_supplementary_cjk_hot
terminal_write_supplementary_cjk_cycling_rows
textCellWidth_ascii_long_fast_path
textCellWidth_cjk_long_hot
textCellWidth_cjk_unique
textCellWidth_complex_grapheme_hot
textCellWidth_complex_grapheme_unique (grapheme instrumentation)
wrapByCells_cjk_long_hot
wrapByCells_cjk_unique

Decision gate (non-inferiority, p95-based):

FAIL: p95 CI lower bound > 1.05 (proven regression > 5%)
PASS: p95 CI upper bound <= 1.05 (proven regression <= 5%)
INCONCLUSIVE: p95 CI crosses 1.05 threshold

Exit codes:

0: All gating scenarios PASS
1: Any gating scenario FAIL
2: Any gating scenario INCONCLUSIVE (no FAIL)

p50 analysis: Reported but not used for gate decision

Informational scenarios: Reported but don't determine exit code

Bundle Size

Approach: Complete dist/ file comparison

Execution:

bash

pnpm run bench:bundle-size  # 5-10min

Measured:

All emitted JS/CJS files in dist/
Public exports (from package.json)
Non-export runtime files (if any)
Aggregate total size

Decision gate (per export entry):

ACCEPTABLE: Δ <= +2KB gzip
WARNING: +2KB < Δ <= +5KB gzip
FAIL: Δ > +5KB gzip

Note: Negative deltas (size reductions) are always acceptable.

Audit Trail

Complete data preserved for reproducibility:

Runtime results:

All 10 paired runs (index, order, timestamps)
Raw p50/p95 values per scenario per pair
Bootstrap seed and iterations
Gating scenario list
Environment metadata

Bundle results:

Per-export comparisons
Aggregate totals
Non-export files (if any)

Remediation Options (If Fails)

Per #119, if runtime regression > 5% proven:

Reduce hooks: Remove from hottest paths
Compile-time strip: Build flag to remove instrumentation
Separate build: @simon_he/vue-tui-profiling package
Rollback: Revert Phase 3 instrumentation

Results

Historical run status (2026-07-10): Inconclusive; acceptance criteria were not yet met.

Initial validation executed: 2026-07-10

Formal result: INCONCLUSIVE

p95 gate: 8/9 scenarios INCONCLUSIVE (wide CIs), 1 PASS, 0 FAIL
Bundle: INCONCLUSIVE (transitive closure not measured)

Exploratory findings (post-hoc):

Two stable Node/tsx source-path p50 signals detected
ASCII fast path: +14.5% / ~38 ns/op (workload-dependent)
Wrap hot path: +3.8%

Critical limitation: Measured tsx executing src/*, NOT published dist or real workloads.

Detailed analysis: See docs/PHASE3.3_RESULTS.mdRaw data: docs/perf/phase3.3-overhead-results.json, docs/perf/phase3.3-bundle-sizes.json

Historical next-required list (resolved by #122/#123):

Remediate instrumentation overhead
Validate built dist artifacts
Proper consumer bundle measurement
Integration workload benchmarks

Issue status: #119 closed after #122 production strip and built-artifact validation.

Execution Log

Environment (Initial Run)

Node: v24.18.0
V8: 13.6
OS: macOS arm64
CPU: Apple M1 Pro
Date: 2026-07-10

Steps

[x] Framework validated
[x] Benchmarks executed
[x] Results analyzed
[x] Decision made (#122 production strip accepted; #123 real-workload closure complete)

Conclusion

Final status: ✅ Complete — #122 removed production instrumentation overhead; #123 completed the production real-workload profile.

[x] Historical source-path experiment: INCONCLUSIVE
[x] Final engineering resolution: PASS / CLOSED BY REMEDIATION (#122 production strip + #123 production workload)
[x] ✅ PASS — final engineering resolution
[ ] ❌ FAIL

Decision: Production strip accepted. No cache/long-text/provider/renderer-architecture/virtual-scroll change is justified by the measured workload.

Closure: Current performance initiative complete; retain the profiler for evidence-driven future regressions.

References

Issue: #119 (Phase 3.3 overhead validation)
Phase 4.0: #118 (identified this as required)
Phase 3.1: #116, Phase 3.2: #117
Phase 2: #115 (baseline harness)

Final closure (2026-07-11)

PR #122 validated that standard ESM/CJS and packed consumers contain no instrumentation collector, no no-op stub, and no hot-path dispatch. PR #123 then exercised the production Agent Console package in CLI and Chromium. The two accepted Agent Console application-level optimizations are mutable shallow replay-history backing and lazy Markdown-block publication in Log mode. No cache, long-text, provider, renderer-architecture, or virtual-scroll change is justified by this workload.

Phase 3.3: Instrumentation Overhead Validation ​

Objective ​

Comparison Points ​

Methodology ​

Runtime Performance ​

Bundle Size ​

Audit Trail ​

Remediation Options (If Fails) ​

Results ​

Execution Log ​

Environment (Initial Run) ​

Steps ​

Conclusion ​

References ​

Final closure (2026-07-11) ​