Per-check deltas treat the 100/A placeholder of skipped/unavailable checks as a real score — removing a tool reads as an improvement #107

Problem

Since #52, a check that did not run (disabled, not applicable, Pro key missing, tool missing) is written with a placeholder score: 100, grade: "A" (src/core.ts:326-327; rationale at src/runners/toolchain.ts:51-55). The composite excludes it (score.ts:19) and the check tables render it as skipped (cli.ts:213-220, :644-646; pr-comment.ts:113). The per-check deltas do not:

• delta.ts:52-54, :117-122 and trend.ts:34-41 subtract raw scores, then pr-comment.ts:92-96, cli.ts:187-191 and report/pages.ts:1004 print them.
• Dart SDK installed between scans → PR comment "⚠️ lint: 100 → 72 (-28)".
• Dart SDK removed (or a Pro key dropped) → "✅ lint: 64 → 100 (+36)": uninstalling a tool is reported as a quality improvement.
• analyzer-snapshot.ts:9 writes score: 100 into meta.analyzerSnapshots for not-run checks, although AnalyzerSnapshot.score is optional (schema/src/report-schema.ts:52).

What to do

1. delta.ts / trend.ts: when either side's status is skipped or unavailable (fall back to details.skipped/unavailable/comingSoon for older reports, as github-app/src/metric-history.ts:250-260 does), emit no numeric delta; report a status transition instead ("lint: unavailable → 72").
2. Renderers (pr-comment.ts, cli.ts, report/pages.ts) list status transitions separately from score changes.
3. analyzer-snapshot.ts: omit score for not-run checks.
4. Schema: CheckResult.status is declared in schema 0.6.0 (Reports don't say which commit, branch, CI run or producer they describe — declare scan provenance in VibeReport.meta (0.6.0) schema#6) — the CLI already writes it (core.ts:347); today it survives only via .passthrough().

Alternatives rejected

• score: null / grade: null. Breaking: CheckResultSchema requires z.number() and GradeSchema (report-schema.ts:32-39); consumers pin ^0.5.0; mcp does arithmetic on it (mcp/src/index.ts:415); stored history already holds 100s. github-app#9 already settled "read status, not score". Revisit only for a v2 report contract.

Acceptance criteria

• Delta between a report with lint unavailable and one where it scored 72 shows no "100 → 72" line in markdown, PR comment or HTML, and does show the status transition.
• The reverse direction shows no "+N" improvement.
• meta.analyzerSnapshots has no score for skipped/unavailable checks.

Related

#52 (introduced the placeholder), github-app#9 (consumer-side fix). Siblings: vibecodeqa/mcp#8, vibecodeqa/app#78.

🤖 Filed with Claude Code