Attempt first bounded rust-hybrid performance A/B optimization

[jununfly]

This was generated by AI during triage.

Parent

#165

What to build

Implement the first bounded A/B optimization candidate selected by the segmented opportunity map. The slice should preserve default user behavior and produce before/after evidence against baseline-indexing-performance-v1.

Source plan: docs/plans/2026-06-24-rust-hybrid-performance-optimization-plan.md

Acceptance criteria

• Implement only the selected bounded candidate from the opportunity map.
• Preserve default user behavior and do not change reference disambiguation semantics unless the selected issue explicitly includes a prior decision allowing it.
• Add deterministic tests at the highest reliable seam for the changed behavior.
• Produce before/after result artifacts against baseline-indexing-performance-v1.
• Compare graphStats and fallback taxonomy.
• Run baseline-agent-sufficiency-v1 only if the selected candidate touches graph semantics, resolver/finalization behavior, Explore output, MCP tools, language/framework extraction, or user-facing sufficiency claims.
• Classify the result as keep, no-go, diagnostic-only, or prerequisite.

Blocked by

• Map rust-hybrid performance opportunities by indexing-chain segment #490

[jununfly]

This was generated by AI during triage.

Completed and kept. Implemented bounded candidate lookup reuse for the default rust-hybrid path by pre-batching more name-matcher candidate-producer lookups while preserving fail-closed TypeScript baseline equivalence checks.

Evidence: docs/benchmarks/tmp-rust-hybrid-performance-ab-name-matching-candidate-lookup-reuse-decision.md and docs/benchmarks/tmp-rust-hybrid-performance-ab-name-matching-candidate-lookup-reuse-result.json. Current-repo median wall time moved from 41661 ms to 26625 ms; nameMatchingMs moved from 32729 ms to 17725 ms. RSS remained unavailable due sandboxed process-list access.

Verification: npm run build; npx vitest run __tests__/candidate-protocol.test.ts __tests__/rust-name-matcher.test.ts __tests__/rust-index-engine-cli.test.ts -t "candidate|Rust name matcher|candidate protocol diagnostics|routing"; npx vitest run __tests__/rust-hybrid-baseline.test.ts __tests__/process-tree-rss.test.ts; git diff --check.

[jununfly]

This was generated by AI during triage.

Closing as implemented with A/B evidence and keep decision recorded.