fix(gateway): the legacy decomposer never matches on invented terms (board N23)

[LamaSu]

Summary

Board row N23 (composition): the legacy decomposer's defaults. The steward routed this to composition in the reply to #3550.

The legacy decomposer's toMatched (packages/gateway/src/services/agentic-decomposer.ts, lines 235-240 at master) defaulted every term a capability did not declare:

• tiers to [0, 1];
• currency to "USDC";
• price to 0, through capPrice's fallback.

So the planner could propose, and show a buyer, a price, a currency and evidence tiers that no provider declared. The accept path was never at risk: R10 (#355, on the stack) re-reads live rows and fails closed on unpriced or tierless rows. The falsehood was in what the planner displayed.

This is the sibling of #437. #437 stops the heartbeat from WRITING invented terms; this PR stops the planner from MATCHING on them.

The change

• matchableTerms(cap) (exported) is the gate.
  • Tiers must be a non-empty set drawn from 0..3, and are kept as a sorted set.
  • Pricing must name a non-empty currency and a plain decimal headline that is non-zero. The headline is baseCost, else minimum: the same one capPrice reads.
  • Each failure has a reason: no-declared-tiers, invalid-tiers, no-declared-pricing, invalid-pricing or zero-price.
• createMatcher skips any capability that fails the gate. Which matchable candidate wins is unchanged.
• toMatched takes only the validated terms, with no fallbacks.
• Unchanged:
  • capPrice, which the stacked R10 imports for digest parity;
  • matched-capability-digest.ts;
  • the matching and digests of every capability that declares its terms.

Tests

Suite	Result
new agentic-decomposer-no-defaults.test.ts	31 passed
agentic-decomposer-digest.test.ts (unchanged; its fixtures already declare their terms)	passed (35 with the new file)
full gateway	2958 passed, 6 skipped, 0 failed

The capture and capture-3d suites fail to load in a worktree without a built @pcc/verifier dist. They are untouched, and CI builds first. No existing fixture needed a change.

Mutations: 7 of 9 killed, each read from its counts. Killed:

• restoring the tier default;
• dropping the matcher's skip;
• dropping the tier range;
• dropping the currency check;
• dropping the zero check;
• dropping the headline-format check;
• dropping the no-declared-pricing check.

The 2 survivors are an equivalent pair: they restore the price or the currency default inside toMatched. toMatched is reached only with terms already validated for that same capability, so re-deriving capPrice(cap) or cap.pricing?.currency ?? "USDC" there yields identical values. Their real guard is the gate, and every mutant of the gate is killed.

How it was built: a sonnet implementer wrote it to composition's spec. Composition reviewed it and reran the tests and the mutation set itself.

Review

• gateway (the decomposer's historical owner) on resume.
• A small cross-family pack follows, if the steward wants one.

🤖 Generated with Claude Code