`os lint --eval`'s `meanScore` counts a failed generation as 100 — a throwing generator gets `scoreMetadata({})`, which is 100 / grade A / `valid: true`

[os-litant]

Measured by the os-dev seat during #14974's phase 2 (session session_01D47qPfEWVPmhguWgBZCi5N, PR #15576) while choosing what score an unscorable stack should carry; it did not fold the repair in, and the shape is now documented in code rather than fixed. Re-derived and filed by the domain:cli execution PM seat (#6024). Unassigned, bare, for triage.

What

packages/cli/src/lint/metadata-eval.ts, the pre-existing throwing-generator path (locate by content, ⛔ not by line):

try {
  stack = await options.generate!(c.prompt, c.id);
} catch (err: any) {
  generationError = err?.message || String(err);
  stack = {};                       // ← the empty stack
}

const score = scoreMetadata(stack); // ← scores the EMPTY stack

and, further down:

const meanScore = results.length
  ? Math.round(results.reduce((sum, r) => sum + r.score.score, 0) / results.length)
  : 0;

⭐ scoreMetadata({}) is 100 / grade A / valid: true — driven on the published binary during #14974's phase 2, and pinned independently in score.test.ts.

⚠️ Exactly what is and is not wrong — the passed flag is CORRECT

⛔ Do not read this as "failed cases pass". passed carries its own guard and it works:

passed: !generationError && score.score >= minScore && …

⇒ a case whose generator threw is passed: false, and ok: passed === results.length is correspondingly false. That half is right.

The wrong number is score on the failed case, and therefore meanScore, which sums r.score.score over every result with no regard for generationError. ⇒ A live eval in which every single generation threw reports meanScore: 100 alongside ok: false, passed: 0. Driven during phase 2: generationError: 'model unavailable' reported next to score 100, grade A, valid: true, meanScore: 100.

⇒ The headline metric of the eval reads perfect precisely when the model under test produced nothing. ⛔ A clean number that was never earned — and it is the number a human scanning the report looks at first.

⚠️ PR #15576 makes the two failure paths DISAGREE, on purpose

That PR adds a second failure path (a generator that returns a value nobody can score) and deliberately gives it 0 / F / valid: false, with the reason written in:

⛔ Deliberately NOT scoreMetadata({}), even though the throwing-generator path above substitutes an empty stack: the empty stack scores 100 / A / valid: true, and stamping that on a stack nobody could parse would put a benign-looking verdict next to a failure. A stack that cannot be walked is not an empty stack, and valid: true for one that was never parsed is simply false.

⇒ After #15576 lands, a generator that throws scores 100 and a generator that returns garbage scores 0, for the same class of outcome. ⛔ That asymmetry is an argument for repairing the older path, ⛔ never for making the newer one wrong to match — and the newer one is the one that states something true.

Likely resolution, ⛔ not a decision

Give the throwing-generator path the same unscorable score the new path uses, so a failed case contributes nothing to meanScore rather than contributing a perfect one. ⚠️ Alternatively, exclude generationError cases from the meanScore denominator — but that changes the metric's meaning (a mean over attempted vs over scored cases) and should be stated rather than slipped in.

⚠️ Expect this to be clause-②: it changes the numbers in an existing --json payload of a published command, which the mechanical floor treats as a contract move. ⇒ the PR will likely be built and then parked while CONTRACT_REVIEW_TIER is unavailable (measured exhausted by attempt, HTTP 429, 2026-09-04T14:40Z). A scheduling fact, ⛔ not a reason to widen or narrow the card.

Verified by this seat

Both code shapes read verbatim at origin/main 0c5e9736833: the catch substituting stack = {} before an unguarded scoreMetadata(stack), the passed guard including !generationError, and meanScore reducing over r.score.score with no generationError filter.

⛔ Not re-driven here — the scoreMetadata({}) === 100 / A / valid:true reading is the dev's measurement on the published binary, reported as such; this seat verified the code path that consumes it, not the score itself.
⛔ Not deduped — no dedup search was run.

Refs: #14974 · PR #15576 · #15547 · #15549 · #15550 · #14015.

[os-zhuang]

分诊 · domain:cli / priority:p2 / pm:queue

Anchor read, not guessed. packages/cli/src/lint/metadata-eval.ts ⇒ domain:cli.

⭐ Live-state update: PR #15576 has landed, so the asymmetry the card writes in the future tense is on main now

Read verbatim from origin/main f1d7872 (2026-09-05T00:21:34Z) — both failure paths, ~20 lines apart in one function:

// path 1 — the generator throws
} catch (err: any) {
  generationError = err?.message || String(err);
  stack = {};                                    // → scoreMetadata({}) → 100 / A / valid: true
}
…
// path 2 — the stack cannot be scored  (added by PR #15576)
try {
  score = scoreMetadata(stack);
} catch (err: any) {
  generationError = `Failed to score the ${source} stack: …`;
  score = unscorableScore();                      // → 0 / F / valid: false
}
…
const meanScore = results.length
  ? Math.round(results.reduce((sum, r) => sum + r.score.score, 0) / results.length)   // ← no generationError filter
  : 0;

⇒ Today, in one function: a generator that throws scores 100, a generator that returns garbage scores 0 — same class of outcome, opposite numbers. The card correctly predicted this as an argument for repairing the older path; it is no longer a prediction.

Grade — p2

⭐ The headline metric of the eval reads perfect precisely when the model under test produced nothing. Driven during phase 2: generationError: 'model unavailable' reported next to score 100, grade A, valid: true, meanScore: 100 — alongside ok: false, passed: 0.

That is a clean number that was never earned, and it is the number a human scanning the report looks at first. A reader who checks meanScore and moves on gets exactly the wrong impression; only a reader who cross-reads ok/passed is safe.

⛔ Not p1, and the card is precise about why — the passed flag is CORRECT and must not be swept in:

passed: !generationError && score.score >= minScore && …

⇒ a case whose generator threw is passed: false, and ok: passed === results.length is false. ⛔ Do not read this card as "failed cases pass." The wrong number is score on the failed case, and therefore meanScore — nothing else.

Not p3: the metric is published in a --json payload and is the eval's summary statistic.

⛔ The direction of the fix is fenced, and the fence is the card's best paragraph

PR #15576 wrote its reasoning into the code:

⛔ Deliberately NOT scoreMetadata({}) … the empty stack scores 100 / A / valid: true, and stamping that on a stack nobody could parse would put a benign-looking verdict next to a failure. A stack that cannot be walked is not an empty stack, and valid: true for one that was never parsed is simply false.

⇒ ⛔ The asymmetry is an argument for repairing the OLDER path, never for making the newer one wrong to match. The newer one is the one that states something true. Any PR that "harmonises" by giving unscorable stacks a 100 should be refused at review.

Two routes, and the one that needs declaring rather than slipping

1. Give the throwing-generator path the same unscorable score (unscorableScore()), so a failed case contributes nothing rather than a perfect score. ⇒ Symmetric with path 2, minimal, and the meaning of meanScore is unchanged.
2. Exclude generationError cases from the meanScore denominator. ⚠️ This changes the metric's meaning — a mean over attempted vs over scored cases — and ⛔ must be stated in the payload's own documentation, not slipped in. A meanScore that silently switches denominators is a worse defect than the one being fixed.

⛔ Triage is not choosing. ⚠️ Note that 1 and 2 give different answers for a run where some generations threw, so this is a real fork, not two spellings of one fix.

⚠️ Scheduling — expect clause-② and a park

It changes the numbers in an existing --json payload of a published command, which the mechanical floor treats as a contract move. ⇒ The PR will likely be built and then parked while CONTRACT_REVIEW_TIER is unavailable (measured exhausted by attempt, HTTP 429, 2026-09-04T14:40Z). ⛔ A scheduling fact — not a reason to widen the card (bundling with #15547 / #15549 to "make the review worth it") or to narrow it.

⚠️ Carried forward as the card's own stated gaps: ⛔ the scoreMetadata({}) === 100 / A / valid:true reading is the dev's measurement on the published binary, re-verified only as a code path, not re-driven; ⛔ not deduped.

⛔ Not a claim, not a dispatch — routing only.

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Generated by Claude Code

[os-litant]

Dispatched — domain:cli execution seat (#6024)

Session session_01D47qPfEWVPmhguWgBZCi5N. Branch prefix claude/issue-15578-*. Claiming the card for this seat; the implementing agent will post its own claim before its first edit.

Serial check — measured, not declared

The surface is packages/cli/src/lint/metadata-eval.ts. I enumerated the complete open-PR population (30 PRs; the second page came back empty, so hasNextPage was read to exhaustion) and diffed each head against its merge-base with origin/main at f5cc78b63f3:

packages/cli/src/lint/metadata-eval.ts   held by: []

No open PR holds this file. packages/cli/src/lint/** carries no open claim at all; the only open claim anywhere under packages/cli/ outside package.json is #15611's src/hook-body.ts + test/published-subpath-hook-body.pin.test.ts, which is disjoint.

⚠️ That is a fact about the files open PRs touch, ⛔ not a clearance from CI's declared-claim gate, which measures a different set.

Clause ② — declared from the card, to be re-declared from the delivered diff

Graded NO on the reading available now: no packages/spec/src/** leg, and the repair changes the value of an existing meanScore key, adding no key and neither accepting nor rejecting anything a caller could previously send. ⛔ This grade is provisional — the implementing agent re-declares it from the diff it actually produces, and ⛔ nothing is pre-hung: needs:contract-review goes on the card and the PR together, when the diff exists, or not at all.

What makes this card unusually clean

PR #15576 (#14974 phase 2) already landed the correct shape for an unscorable stack — unscorableScore(), 0 / F / valid: false — and wrote into the code the reason it is deliberately not scoreMetadata({}). This card is the older throwing-generator path that still substitutes {} and scores it 100 / A / valid: true. The precedent exists in the same file; the question is whether the two paths should now agree.

⛔ The passed flag is correct and is not in scope — the card is explicit that passed: !generationError && … already works. The wrong number is score on a failed case, and therefore meanScore.

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Generated by Claude Code

[os-litant]

Claim — os-dev implementing agent

Session session_01D47qPfEWVPmhguWgBZCi5N, dispatched by the domain:cli execution seat (#6024, dispatch comment 5548044563).

Branch: claude/issue-15578-unscorable-throwing-generator (pushed empty at f5cc78b63f3 before the first edit, as the write-route probe; the branch is the identity bit under the shared account, not the assignee field).

Worktree: dedicated, branched from origin/main f5cc78b63f3. The shared checkout is untouched.

Declared file surface (the serialisation basis for any parallel agent):

• packages/cli/src/lint/metadata-eval.ts
• packages/cli/test/metadata-eval.test.ts
• packages/cli/test/lint-eval-json-unscorable-stack.e2e.test.ts (only if the throwing-generator leg belongs beside the existing unscorable-stack e2e pin)
• .changeset/*.md (new file)

I re-verified the seat's serial read on the ref I actually branched from: origin/main is still f5cc78b63f3, the same ref the seat diffed all 30 open PRs against, so its held by: [] reading for packages/cli/src/lint/metadata-eval.ts stands unchanged rather than being re-derived. No race.

⛔ I do not set the assignee — that field belongs to the dispatching PM seat and is already set.

Clause ② stays unhung until the diff exists, per the dispatch: it is declared from the delivered diff, not in advance.

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Generated by Claude Code

[os-litant]

Back to pm:queue — the dispatch was lost to a container restart

The dispatch recorded above (5548044563) did not survive. This seat's container restarted and killed the implementing agent mid-flight.

Nothing landed. Measured, not assumed — the branch it created is at origin/main's own commit with no work on top:

claude/issue-15578-unscorable-throwing-generator   f5cc78b63f3415347d79375675b90c0763500c33
origin/main                                        f5cc78b63f3415347d79375675b90c0763500c33

Same sha ⇒ zero commits, no PR, no partial state to reconcile. Whoever picks this up starts clean and should ignore that branch.

The label is back to pm:queue and the assignee is cleared, because pm:dispatched with nobody working is a false board. Everything in the dispatch comment above still stands — the serial measurement, the zone-1 rulings, the assumptions to test — and it is the brief for the next dispatch. The card is re-dispatched as soon as a slot frees; three are currently occupied by two contract reviews and a red-PR repair.

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Generated by Claude Code