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+// tests/validators/brief-gate-coverage.test.mjs
+// SKAL-1·4a — two-sided (class-balanced) coverage for every error-severity
+// BRIEF_* BLOCKER the brief-validator can emit.
+//
+// brief-validator.test.mjs already tests many codes; several were FAILURE-only
+// (only the raising case asserted) and three were untested. This meta-test pins
+// a class-balanced pair { fail, pass } for EACH in-scope BLOCKER and a parity
+// guard so a code can't sit in IN_SCOPE_CODES without a paired case. It removes
+// the one-sided-optimization risk programmatically, not by inspection.
+//
+// In scope = ERROR-severity BRIEF_* codes the validator pushes to errors[]
+// (BLOCKERs). EXCLUDED: warning-severity codes (BRIEF_TLDR_TOO_LONG,
+// BRIEF_VERSION_FORMAT, BRIEF_VERSION_BELOW_MINIMUM, BRIEF_PARTIAL_SKIPPED) — a
+// "passing" counterpart to a warning is not a BLOCKER concern — and the
+// file-level BRIEF_NOT_FOUND / BRIEF_READ_ERROR which live in validateBrief()
+// (filesystem), not validateBriefContent().
+//
+// LIMITATION: brief-validator.mjs does not export its code set (codes are string
+// literals inside issue(...)), so IN_SCOPE_CODES is HAND-MAINTAINED. A NEW
+// validator BLOCKER must be added here manually; the parity guard catches
+// list/case drift, not validator drift. (Operator chose the hand-maintained list
+// over exporting BRIEF_ERROR_CODES from the forbidden_paths-guarded validator.)
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { validateBriefContent } from '../../lib/validators/brief-validator.mjs';
+
+// ---- valid bases (mirror tests/validators/brief-validator.test.mjs) ----------
+
+const GOOD_BRIEF = `---
+type: trekbrief
+brief_version: "2.0"
+created: 2026-04-30
+task: "Add JWT auth to API"
+slug: jwt-auth
+project_dir: .claude/projects/2026-04-30-jwt-auth/
+research_topics: 2
+research_status: pending
+auto_research: false
+interview_turns: 5
+source: interview
+---
+
+# Task: JWT auth
+
+## Intent
+
+Why this matters.
+
+## Goal
+
+What success looks like.
+
+## Success Criteria
+
+- All tests pass.
+`;
+
+const GOOD_BRIEF_22 = `---
+type: trekbrief
+brief_version: "2.2"
+created: 2026-06-18
+task: "Add JWT auth to API"
+slug: jwt-auth
+project_dir: .claude/projects/2026-06-18-jwt-auth/
+research_topics: 0
+research_status: complete
+auto_research: false
+interview_turns: 5
+source: interview
+framing: new-direction
+phase_signals_partial: true
+---
+
+# Task: JWT auth
+
+## TL;DR
+
+Net-new JWT auth; no prior brief to anchor against.
+
+## Intent
+
+Why this matters.
+
+## Goal
+
+What success looks like.
+
+## Success Criteria
+
+- All tests pass.
+`;
+
+const REVIEW_AS_BRIEF = `---
+type: trekreview
+task: "Review delivered trekreview v1.0"
+slug: trekreview
+project_dir: .claude/projects/2026-05-01-trekreview/
+findings:
+  - 0123456789abcdef0123456789abcdef01234567
+  - fedcba9876543210fedcba9876543210fedcba98
+---
+
+# Review brief
+
+## Intent
+
+Adversarial review of delivered trekreview v1.0.
+
+## Goal
+
+Find what was missed.
+
+## Success Criteria
+
+- All BLOCKER findings get a fix-plan.
+`;
+
+// signals blocks
+const GOOD_SIGNALS = `phase_signals:
+  - phase: plan
+    effort: high
+    model: opus
+`;
+const BAD_PHASE_SIGNALS = `phase_signals:
+  - phase: nonsense
+    effort: high
+`;
+const BAD_EFFORT_SIGNALS = `phase_signals:
+  - phase: plan
+    effort: turbo
+`;
+const BAD_MODEL_SIGNALS = `phase_signals:
+  - phase: plan
+    effort: high
+    model: gpt4
+`;
+
+// convenience builders
+const v21 = (s) => s.replace('brief_version: "2.0"', 'brief_version: "2.1"');
+const withLine = (s, line) => s.replace('source: interview\n', `source: interview\n${line}`);
+
+// ---- the canonical in-scope set + a class-balanced pair for each -------------
+
+const IN_SCOPE_CODES = [
+  'BRIEF_MISSING_FIELD',
+  'BRIEF_BAD_STATUS',
+  'BRIEF_STATE_INCOHERENT',
+  'BRIEF_WRONG_TYPE',
+  'BRIEF_BAD_FINDINGS_TYPE',
+  'BRIEF_MISSING_SECTION',
+  'BRIEF_INVALID_FRAMING',
+  'BRIEF_MISSING_FRAMING',
+  'BRIEF_V51_MISSING_SIGNALS',
+  'BRIEF_SIGNALS_MUTUALLY_EXCLUSIVE',
+  'BRIEF_INVALID_PHASE_SIGNALS',
+  'BRIEF_INVALID_PHASE_SIGNAL_PHASE',
+  'BRIEF_INVALID_EFFORT',
+  'BRIEF_INVALID_MODEL',
+];
+
+const CASES = {
+  BRIEF_MISSING_FIELD: {
+    fail: GOOD_BRIEF.replace(/^research_topics: 2\n/m, ''),
+    pass: GOOD_BRIEF,
+  },
+  BRIEF_BAD_STATUS: {
+    fail: GOOD_BRIEF.replace('research_status: pending', 'research_status: maybe'),
+    pass: GOOD_BRIEF,
+  },
+  BRIEF_STATE_INCOHERENT: {
+    fail: GOOD_BRIEF.replace('research_status: pending', 'research_status: skipped'),
+    pass: GOOD_BRIEF,
+  },
+  BRIEF_WRONG_TYPE: {
+    fail: GOOD_BRIEF.replace('type: trekbrief', 'type: notabrief'),
+    pass: GOOD_BRIEF,
+  },
+  BRIEF_BAD_FINDINGS_TYPE: {
+    fail: REVIEW_AS_BRIEF.replace(/findings:\n  - 0123[\s\S]*?- fedcba[0-9a-f]+/, 'findings: not-an-array'),
+    pass: REVIEW_AS_BRIEF,
+  },
+  BRIEF_MISSING_SECTION: {
+    fail: GOOD_BRIEF.replace(/## Intent\n\nWhy this matters\.\n\n/, ''),
+    pass: GOOD_BRIEF,
+  },
+  BRIEF_INVALID_FRAMING: {
+    fail: withLine(GOOD_BRIEF, 'framing: sideways\n'),
+    pass: GOOD_BRIEF_22,
+  },
+  BRIEF_MISSING_FRAMING: {
+    fail: GOOD_BRIEF_22.replace('framing: new-direction\n', ''),
+    pass: GOOD_BRIEF_22,
+  },
+  BRIEF_V51_MISSING_SIGNALS: {
+    fail: v21(GOOD_BRIEF),
+    pass: GOOD_BRIEF, // 2.0 — gate inactive
+  },
+  BRIEF_SIGNALS_MUTUALLY_EXCLUSIVE: {
+    fail: withLine(v21(GOOD_BRIEF), `phase_signals_partial: true\n${GOOD_SIGNALS}`),
+    pass: withLine(v21(GOOD_BRIEF), 'phase_signals_partial: true\n'),
+  },
+  BRIEF_INVALID_PHASE_SIGNALS: {
+    fail: withLine(GOOD_BRIEF, 'phase_signals: notalist\n'),
+    pass: withLine(v21(GOOD_BRIEF), GOOD_SIGNALS),
+  },
+  BRIEF_INVALID_PHASE_SIGNAL_PHASE: {
+    fail: withLine(v21(GOOD_BRIEF), BAD_PHASE_SIGNALS),
+    pass: withLine(v21(GOOD_BRIEF), GOOD_SIGNALS),
+  },
+  BRIEF_INVALID_EFFORT: {
+    fail: withLine(v21(GOOD_BRIEF), BAD_EFFORT_SIGNALS),
+    pass: withLine(v21(GOOD_BRIEF), GOOD_SIGNALS),
+  },
+  BRIEF_INVALID_MODEL: {
+    fail: withLine(v21(GOOD_BRIEF), BAD_MODEL_SIGNALS),
+    pass: withLine(v21(GOOD_BRIEF), GOOD_SIGNALS),
+  },
+};
+
+test('gate coverage — CASES keys exactly match IN_SCOPE_CODES (no silent gap)', () => {
+  assert.deepEqual(Object.keys(CASES).sort(), [...IN_SCOPE_CODES].sort());
+});
+
+test('gate coverage — every in-scope BRIEF_* BLOCKER raises on its fail case', () => {
+  for (const code of IN_SCOPE_CODES) {
+    const r = validateBriefContent(CASES[code].fail, { strict: true });
+    assert.ok(
+      r.errors.find((e) => e.code === code),
+      `${code}: fail case did NOT raise it; errors=${JSON.stringify(r.errors.map((e) => e.code))}`,
+    );
+  }
+});
+
+test('gate coverage — every in-scope BRIEF_* BLOCKER is absent on its (valid) pass case', () => {
+  for (const code of IN_SCOPE_CODES) {
+    const r = validateBriefContent(CASES[code].pass, { strict: true });
+    assert.ok(
+      !r.errors.find((e) => e.code === code),
+      `${code}: pass case wrongly raised it; errors=${JSON.stringify(r.errors.map((e) => e.code))}`,
+    );
+    assert.equal(r.valid, true, `${code}: pass case should be a fully valid brief; errors=${JSON.stringify(r.errors)}`);
+  }
+});