feat(challenge): D5 stemmed prereq matcher + D9 cache removal (0.21.0)

[klappy]

Closes the last two vodka anti-pattern remnants in oddkit_challenge per P1.3.3, mirroring the matchers and the no-microsecond-caching discipline gate shipped in 0.20.0. Ships as 0.21.0.

Three items

Item 1 — D5 split-by-fit applied to challenge

Migrates evaluatePrerequisiteCheck from regex-per-check to stemmed set intersection over a parse-time PrereqMatchVocab struct.

• New parseCheckColumn(check: string): PrereqMatchVocab helper at canon-fetch time:
  • Extracts quoted keywords via /"([^"]+)"/g
  • Tokenizes each into stems via the existing Porter-style tokenize() from bm25.ts
  • Detects the four structural-test hints (URL / numeric / proper-noun / citation) as boolean flags
• New interface PrereqMatchVocab mixed into both BasePrerequisite and ChallengeTypeDef.prerequisiteOverlays[] via intersection — keeps the per-type and base-prereq structs structurally compatible (DRY)
• Both parsers (discoverChallengeTypes + fetchBasePrerequisites) populate via ...parseCheckColumn(cols[1]) spread
• Runtime: tokenize(input) hoisted out of the per-prereq loop; per-prereq cost is now a Set lookup, not a regex compile
• Strictly additive: every input that matched the prior regex still matches; stemmed variations newly match (problems identified → problem + identif, considered alternatives → consid + altern); structural side-tests preserved verbatim

Item 2 — D9 applied to cachedChallengeTypeIndex

Removes the BM25 type-detection index cache per klappy://canon/principles/cache-fetches-and-parses.

• cachedChallengeTypeIndex + cachedChallengeTypeIndexKnowledgeBaseUrl module-level fields deleted
• getOrBuildChallengeTypeIndex function deleted
• cleanup_storage resets deleted
• runChallengeAction call site rebuilds the BM25 index inline per request via buildBM25Index(types.map(t => ({id: t.slug, text: t.detectionText})), vocab.stopWords) — same pattern gate shipped in 0.20.0

Removes the four-cost plumbing tax the new canon principle enumerates.

Item 3 — Canon principle (already merged)

klappy://canon/principles/cache-fetches-and-parses shipped first in klappy.dev#125 (3726073). Third deciding-argument recurrence satisfies the graduation test.

Verification (Option A — smoke-heavy)

Check	Result
npx tsc --noEmit (workers)	clean
node workers/test/governance-parser.test.mjs	105/105 pass
Preview smoke @ challenge-d5-d9-parity-oddkit.klappy.workers.dev × 3 consecutive	170/170 pass × 3

Initial cold-start run had 1 flaky failure (network-timing class), then 3 consecutive 170/170 runs at steady state. +12 assertions over P1.3.2's 158-assertion baseline (the 9 P1.3.3 assertion blocks expand to 12 individual ok() invocations).

New smoke coverage (workers/test/canon-tool-envelope.smoke.mjs)

• Stemmed base-prereq match for 3 inflected variants of evidence-cited vocab
• Per-type proposal alternatives-considered + risk-acknowledged via stemmed match
• Non-match input surfaces evidence-cited gap correctly
• URL structural test preservation (input with no keyword overlap passes via URL path)
• Proper-noun structural test preservation
• Citation structural test preservation (according to triggers citation path)
• Inline rebuild stability across consecutive identical-input calls (D9 attestation)
• Backward-compat: literal canon keyword observed still passes (pre-refactor regex semantics preserved)
• Confidence-signaled stemmed match on believe → believ

Diff stat

 CHANGELOG.md                               |  18 +++
 package.json                               |   2 +-
 workers/package-lock.json                  |   4 +-
 workers/package.json                       |   2 +-
 workers/src/orchestrate.ts                 | 194 +++++++++++++++++++----------
 workers/test/canon-tool-envelope.smoke.mjs | 133 ++++++++++++++++++++
 6 files changed, 284 insertions(+), 69 deletions(-)

Lockfile re-synced from stale 0.18.0 → 0.21.0 (was unchanged through 0.19.0 and 0.20.0 releases — pre-existing drift).

Sweep status after this lands

Tool	Version	Envelope	Matcher	BM25 index cached?
oddkit_encode	0.18.0	governance_uri (singular)	regex (separate beat — P8)	parse product cached
oddkit_challenge	0.21.0	governance_uris × 4	stemmed set intersection + structural	rebuild inline
oddkit_gate	0.20.0	governance_uris × 2	BM25 + stemmed set intersection	rebuild inline

Challenge now has full canon parity with gate's matcher and caching discipline.

References

• PRD: /home/claude/work/prd-p1-3-3.md (working dir, ephemeral per P1.3.2 precedent)
• Handoff: klappy://odd/handoffs/2026-04-20-p1-3-3-challenge-revisit
• Inheritance: P1.3.2 ledger klappy://odd/ledger/2026-04-20-p1-3-2-gate-canary-landed (D5 + D9 origin)
• Canon principle: klappy://canon/principles/cache-fetches-and-parses (klappy.dev#125)

---

Note

Medium Risk
Changes oddkit_challenge prerequisite evaluation and type-detection indexing behavior, which can alter when prerequisites are considered met and when types are detected. While intended to be additive, regressions could affect challenge output consistency and performance under load.

Overview
Bumps release to 0.21.0 and updates the changelog to document the new challenge matcher and caching principle.

oddkit_challenge prerequisite checks now use stemmed token set intersection computed at canon-parse time (via new PrereqMatchVocab + parseCheckColumn) with tokenize(input) hoisted out of the per-prereq loop, while preserving the prior structural checks (URL/numeric/proper-noun/citation) and the non-trivial-input fallback.

Removes the cached BM25 index used for challenge type detection (cachedChallengeTypeIndex/getOrBuildChallengeTypeIndex) and instead rebuilds the BM25 index inline per request. Adds new smoke-test coverage asserting stemmed prereq matching, structural-check preservation, and deterministic results across consecutive calls.

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

Bugbot Autofix prepared fixes for both issues found in the latest run.

• ✅ Fixed: Stop-word filtering silently drops quoted canon keywords
  • Passed an empty stop-words Set to tokenize() in parseCheckColumn so canon vocab like "from" is preserved and the length>=20 fallback is no longer triggered by all-stop-word vocabularies.
• ✅ Fixed: BasePrerequisite duplicates PrereqMatchVocab fields instead of reusing
  • Redefined BasePrerequisite as a type alias intersecting its own fields with PrereqMatchVocab so future field additions to the shared shape propagate automatically.

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[cursor]

Stop-word filtering silently drops quoted canon keywords

Medium Severity

parseCheckColumn calls tokenize(m[1]) on each quoted keyword, which applies default STOP_WORDS filtering. Canon vocabulary words that are English stop words — notably "from", explicitly listed in the CHANGELOG as source-named vocab — are silently dropped from stemmedTokens. The old regex evaluator matched these literally against raw input with no stop-word filtering. This creates two behavioral changes: (1) when a stop word is the only matching keyword for an input, the old code passes but the new code fails (false negative); (2) when all quoted keywords are stop words, stemmedTokens is empty, causing the length >= 20 fallback to trigger inappropriately (false positive). This violates the documented "strictly additive" guarantee. Passing an empty Set as the second argument to tokenize in parseCheckColumn would preserve the old matching semantics.

Additional Locations (1)

• workers/src/orchestrate.ts#L2374-L2383

 

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[cursor]

BasePrerequisite duplicates PrereqMatchVocab fields instead of reusing

Low Severity

PrereqMatchVocab was introduced as a "shared shape" to keep BasePrerequisite and ChallengeTypeDef.prerequisiteOverlays in sync (per the PR description and the interface's own doc comment). However, BasePrerequisite manually declares the same five fields rather than using & PrereqMatchVocab intersection or extending PrereqMatchVocab. Only prerequisiteOverlays actually uses the shared interface. This defeats the stated DRY purpose — the two interfaces can drift independently if PrereqMatchVocab is later updated.

Additional Locations (1)

• workers/src/orchestrate.ts#L120-L129

 

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