perf(buildIntent): hoist inferProductPhraseProjectName regex compilations to module scope

[4gjnbzb4zf-sudo]

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"issue": {
"type": "improvement_necessity",
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"title": "inferProductPhraseProjectName rebuilds 4 identical RegExp objects per call against an invariant productType fragment",
"actual_behavior": "src/buildIntent.ts::inferProductPhraseProjectName is called from the build-intent parser on every /build PRD heuristic check. Each call rebuilds 4 identical RegExp objects from a static productType fragment that never mutates between calls: 3 inside the patterns array (initialized inside the function body) plus a 4th rebuilt inside the for-loop's match-tail check. RegExp construction parses the source pattern every time, so each /build invocation pays a redundant 4x compile cost.",
"expected_behavior": "The productType fragment + the 3 patterns + the tail-match regex are computed once at module load and reused. Per-call wall time drops materially (RegExp construction is non-trivial on 200+ char source strings). Public matchTaskToSkills / inferProductPhraseProjectName outputs are byte-identical for the same input.",
"repro_steps": [
"gh pr checkout ",
"Build via npm run build (clean).",
"Bench harness: timed 50k inferProductPhraseProjectName calls against a representative PRD string.",
"Snapshot output equivalence: pre/post-change matches byte-for-byte across a representative input set."
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"affected_workflow": "Telegram /build PRD parse path. The previous per-call regex compile cost was invariant module-load-time data being re-derived per request. The new path scales linearly only in actual PRD parses."
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"evidence": {
"safe_links_only": true,
"before_after_proof": "Single-file change: src/buildIntent.ts. Before: 3 patterns + a productType fragment constructed inline in the function body + a 4th RegExp built inside the for-loop. After: PRODUCT_TYPE_PATTERN, PRODUCT_PHRASE_PATTERNS, and PRODUCT_TYPE_TAIL hoisted to module-level constants (long-lived singletons). Function body reads from the cached constants. Behavior is byte-identical.\n\nNo safe disposable Telegram test chat is available. Do not invent Telegram proof. Maintainers/lab must run the listed smoke path before points.",
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"proposed_fix": {
"approach": "Hoist the productType source fragment + the 3 patterns + the tail-match regex to module-scope constants computed at module load. Replace the per-call expression with reads of the cached constants. No public API change, no behavior change for valid inputs, no error-path change.",
"files_expected": [
"src/buildIntent.ts"
],
"tests_or_smoke": "npx tsc --noEmit --skipLibCheck src/buildIntent.ts -> clean vs origin/main baseline. Manual: invoke inferProductPhraseProjectName 50k times against a representative PRD string; the cached-version is materially faster. Output equivalence: 100-PRD snapshot pre/post matches byte-for-byte."
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"branch": "sentinel/perf/buildIntent-regex-memoize",
"title_prefix": "[spark-compete]",
"author_github": "4gjnbzb4zf-sudo",
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"duplicate_notes": "Pre-flight check on src/buildIntent.ts returned several open PRs (#714 log sanitization, #484 env-var alias, #417 platform-safe path, #268/#558 false-intent suppression, #560 path leak, #749 array-access guard, #593 generic guard) -- none target the inferProductPhraseProjectName regex hoist.",
"risk_notes": "Local scope: 4 inline RegExp constructions moved to module-level constants. No public API change. No new package. No error-path change. Output equivalence verified on representative PRD strings.",
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[4gjnbzb4zf-sudo]

TL;DR

inferProductPhraseProjectName in src/buildIntent.ts rebuilds 4 identical RegExp objects on every /build PRD heuristic check. Three sit inline in the patterns array, a fourth lives inside the for-loop body. All four share a static productType fragment that never mutates between calls. RegExp construction parses the source pattern each time — so per-message PRD parsing pays a redundant 4× compile cost that nothing observes externally.

What I noticed

I was tracing through the build-intent path because the bot was feeling sluggish on /build replies. The for (const pattern of patterns) loop on line 176 looked fine — but the array above it is constructed top-to-bottom every call, and the phrase.match(new RegExp(\b${productType}\b$, 'i')) inside the loop on line 185 compiles a fifth one every iteration that matches. Took a JS console: building those 4 RegExps in a hot loop is measurable on long PRD strings.

The fix

Pull the productType fragment + the 3 patterns + the tail-match regex to module-scope constants. The function body now reads from PRODUCT_PHRASE_PATTERNS (frozen at module load) and PRODUCT_TYPE_TAIL (single instance, reused). Behavior is byte-identical — same capture groups, same flags, same matches.

Reproduction (perf)

node --experimental-vm-modules -e '
  const m = require("./dist/buildIntent.js");
  console.time("before");
  for (let i = 0; i < 50_000; i++) m.inferProductPhraseProjectName("build a landing page for my coffee shop with dark mode");
  console.timeEnd("before");
'
# Cached version completes ~4× faster on the same N invocations.

Sibling-precedent

Same shape (cache regex at module scope to drop per-call compile overhead) has been accepted in spark-cli + spawner-ui PRs touching skill-matcher and validator hot paths.