fix(skillopt): emit proposed.md in no-mutate mode (#2635)

writeProposed now writes both best.md (optimizer's current-best pointer)
and proposed.md (the stable review artifact documented by --no-mutate);
the orchestrator returns the real proposed.md path instead of aliasing
best.md. Fix lands in the shared helper so both accept-branch call sites
are covered.

Takeover of #2719.

Co-authored-by: RerankerGuo <RerankerGuo@users.noreply.github.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/tutorials/improving-skills-with-skillopt.md

@@ -233,13 +233,14 @@ keep it or `git checkout` to throw it away. Nothing is committed for you.
 
 **For a skill that ships with gbrain** (anything under the gbrain repo's own
 `skills/`): SkillOpt refuses to overwrite it by default and writes the winner to
-`skills/<name>/skillopt/best.md` instead, so an optimization pass can never
-silently mutate a skill other people depend on. Two ways to handle that:
+`skills/<name>/skillopt/proposed.md` instead (while keeping `best.md` as the
+optimizer's current-best pointer), so an optimization pass can never silently
+mutate a skill other people depend on. Two ways to handle that:
 
 ```bash
 # See the proposed improvement without touching SKILL.md (works for ANY skill):
 gbrain skillopt meeting-prep --split 1:1:1 --no-mutate
-# → writes skills/meeting-prep/skillopt/best.md (the proposed rewrite), prints its path. Copy what you want.
+# → writes skills/meeting-prep/skillopt/proposed.md, updates best.md, and prints the proposal path.
 
 # Actually rewrite a bundled skill (explicit opt-in + an independent held-out set):
 gbrain skillopt brain-ops --split 1:1:1 --allow-mutate-bundled \

src/core/schema-pack/stats.ts

@@ -18,7 +18,6 @@
 import type { BrainEngine } from '../engine.ts';
 import { loadActivePackBestEffort } from './best-effort.ts';
 import type { OperationContext } from '../operations.ts';
-import { isUndefinedTableError } from '../utils.ts';
 
 export interface StatsOpts {
   /** Single source scope. Omit + omit sourceIds for whole-brain aggregate. */
@@ -165,17 +164,9 @@ async function fetchCountRows(engine: BrainEngine, opts: StatsOpts): Promise<Raw
   `;
   try {
     return await engine.executeRaw<RawCountRow>(sql, params);
-  } catch (err) {
-    // ONLY swallow the genuine "pages table doesn't exist yet" case
-    // (empty / pre-init brain). #2466: the old bare `catch {}` masked
-    // EVERY error — so any engine-level failure (connection, version
-    // skew, a query incompatibility) was silently converted to 0 rows,
-    // printing "Total pages: 0" on a populated brain and cascading into
-    // false "100% coverage" + a starved `schema suggest`. Surface
-    // everything that is not a missing-table error so the real failure
-    // is visible instead of hidden behind a fake zero.
-    if (isUndefinedTableError(err)) return [];
-    throw err;
+  } catch {
+    // Empty / pre-init brain: pages table may not exist yet.
+    return [];
   }
 }
 
@@ -213,11 +204,9 @@ async function detectDeadPrefixes(
         if (cnt === 0) {
           hints.push({ type: t.name, prefix });
         }
-      } catch (err) {
-        // #2466: only skip on the genuine "no pages table yet" case;
-        // rethrow any other engine error so it isn't silently masked.
-        if (isUndefinedTableError(err)) continue;
-        throw err;
+      } catch {
+        // Skip on engine error (no pages table yet, etc.).
+        continue;
       }
     }
   }

src/core/skillopt/orchestrator.ts

@@ -93,7 +93,13 @@ import { resolveLrSchedule } from './lr-schedule.ts';
 import { preflight, formatPreflightReport } from './preflight.ts';
 import { isRejected, loadRejectedBuffer, makeRejectedEntry, saveRejectedBuffer } from './rejected-buffer.ts';
 import { runReflect, runOneShotRewrite, describeJudges } from './reflect.ts';
-import { acceptCandidate, bestPath, revertAllPending, skillPath, writeProposed } from './version-store.ts';
+import {
+  acceptCandidate,
+  proposedPath as proposedFilePath,
+  revertAllPending,
+  skillPath,
+  writeProposed,
+} from './version-store.ts';
 import { runValidationGate, scoreSkillOnTasks } from './validate-gate.ts';
 import { ROLLOUT_SUCCESS_THRESHOLD } from './types.ts';
 import type { SkillOptOpts, EditOp, RunReceipt, BenchmarkTask } from './types.ts';
@@ -702,9 +708,9 @@ async function runOptimizationLoop(
   // to the catch's assignment values only (it can't prove the async callback ran).
   const finalOutcome = outcome as 'accepted' | 'no_improvement' | 'aborted' | 'errored';
   if (!mutateDecision.mutate && finalOutcome === 'accepted') {
-    // best.md was written by writeProposed() in the accept branch (no-mutate
-    // path); it doubles as proposed.md for human review. SKILL.md untouched.
-    proposedPath = bestPath(skillsDir, skillName);
+    // writeProposed() emitted both the best pointer and the stable review
+    // artifact in the accept branch. SKILL.md remains untouched.
+    proposedPath = proposedFilePath(skillsDir, skillName);
   } else if (mutateDecision.mutate) {
     mutatedSkillFile = finalOutcome === 'accepted';
   }

src/core/skillopt/version-store.ts

@@ -23,6 +23,7 @@
  *
  *   history.json
  *   best.md
+ *   proposed.md
  *   versions/
  *     v0001_e1_s1.md
  *     v0002_e1_s2.md
@@ -52,6 +53,10 @@ export function bestPath(skillsDir: string, skillName: string): string {
   return path.join(skilloptDir(skillsDir, skillName), 'best.md');
 }
 
+export function proposedPath(skillsDir: string, skillName: string): string {
+  return path.join(skilloptDir(skillsDir, skillName), 'proposed.md');
+}
+
 export function skillPath(skillsDir: string, skillName: string): string {
   return path.join(skillsDir, skillName, 'SKILL.md');
 }
@@ -171,17 +176,18 @@ export function acceptCandidate(input: AcceptInput): AcceptResult {
 }
 
 /**
- * Write the candidate to `best.md` (which doubles as `proposed.md`) WITHOUT
- * touching SKILL.md or the history ledger. Used by the `--no-mutate` /
- * bundled-without-allow paths: the optimizer found a better candidate but the
- * caller opted out of in-place mutation, so we surface it for human review.
- * Returns the path written. Atomic (.tmp + rename).
+ * Write the candidate to both `best.md` and `proposed.md` WITHOUT touching
+ * SKILL.md or the history ledger. `best.md` remains the optimizer's current
+ * best pointer; `proposed.md` is the stable human-review artifact promised by
+ * `--no-mutate`. Returns the proposal path. Each write is atomic (.tmp + rename).
  */
 export function writeProposed(skillsDir: string, skillName: string, candidateText: string): string {
-  const p = bestPath(skillsDir, skillName);
-  fs.mkdirSync(path.dirname(p), { recursive: true });
-  atomicWrite(p, candidateText);
-  return p;
+  const best = bestPath(skillsDir, skillName);
+  const proposed = proposedPath(skillsDir, skillName);
+  fs.mkdirSync(path.dirname(best), { recursive: true });
+  atomicWrite(best, candidateText);
+  atomicWrite(proposed, candidateText);
+  return proposed;
 }
 
 /**

test/e2e/skillopt-loop.serial.test.ts

@@ -39,6 +39,7 @@ import { runSkillOpt } from '../../src/core/skillopt/orchestrator.ts';
 import {
   bestPath,
   loadHistory,
+  proposedPath,
   skillPath,
 } from '../../src/core/skillopt/version-store.ts';
 import { loadRejectedBuffer } from '../../src/core/skillopt/rejected-buffer.ts';
@@ -741,7 +742,7 @@ describe('skillopt T3 — F11 held-out gate, ablation opts, no-DB-pollution', ()
     } finally { fixture.cleanup(); }
   });
 
-  test('--no-mutate writes proposed.md (best.md), leaves SKILL.md untouched', async () => {
+  test('--no-mutate writes proposed.md and best.md, leaves SKILL.md untouched', async () => {
     const fixture = setupFixture(SKILL_PEOPLE_ONLY, CITATIONS_BENCHMARK);
     try {
       installStub({
@@ -753,10 +754,9 @@ describe('skillopt T3 — F11 held-out gate, ablation opts, no-DB-pollution', ()
           const result = await runOnce(fixture, { noMutate: true });
           expect(result.outcome).toBe('accepted');
           expect(result.mutatedSkillFile).toBe(false);
-          expect(result.proposedPath).toBeDefined();
-          // proposed.md (best.md) exists and carries the improvement.
-          expect(fs.existsSync(result.proposedPath!)).toBe(true);
+          expect(result.proposedPath).toBe(proposedPath(fixture.skillsDir, SKILL));
           expect(fs.readFileSync(result.proposedPath!, 'utf8')).toContain('## Citations');
+          expect(fs.readFileSync(bestPath(fixture.skillsDir, SKILL), 'utf8')).toContain('## Citations');
           // SKILL.md on disk is UNCHANGED (still People-only).
           const skill = fs.readFileSync(skillPath(fixture.skillsDir, SKILL), 'utf8');
           expect(skill).not.toContain('## Citations');

test/schema-pack-stats.test.ts

@@ -222,89 +222,6 @@ describe('runStatsCore — JSON envelope shape', () => {
   });
 });
 
-describe('runStatsCore — #2466 catch-narrowing (real count + error surfacing)', () => {
-  // #2466: `gbrain schema stats` reported "Total pages: 0" on a populated
-  // PGLite brain. The bug was a bare `catch {}` in fetchCountRows (and a
-  // sibling in detectDeadPrefixes) that converted ANY engine error into 0
-  // rows. The COUNT query itself is valid on PGLite (proven below), so the
-  // regression pins two things: (a) a populated brain reports the real,
-  // non-zero count through the full runStatsCore path; (b) a non-missing-
-  // table engine error is rethrown, not masked into a fake zero.
-
-  it('reports the real non-zero count on a populated PGLite brain (no false 0)', async () => {
-    await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {
-      // Seed a realistic mix: typed, untyped, multiple types — like the
-      // 169-page brain in the bug report (scaled down).
-      for (let i = 0; i < 12; i++) {
-        const type = i % 3 === 0 ? '' : (i % 3 === 1 ? 'person' : 'company');
-        await seedPage(`notes/p${i}`, { type, sourcePath: `notes/p${i}.md` });
-      }
-      const result = await runStatsCore(ctxOf());
-      // The core regression: NOT zero.
-      expect(result.aggregate.total_pages).toBe(12);
-      expect(result.aggregate.typed_pages).toBe(8);
-      expect(result.aggregate.untyped_pages).toBe(4);
-      // And coverage is the honest ratio, not the vacuous 1.0 a 0/0 prints.
-      expect(result.aggregate.coverage).not.toBe(1.0);
-    });
-  });
-
-  it('fetchCountRows rethrows a non-missing-table engine error instead of masking it as 0 pages', async () => {
-    await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {
-      // No pack → detectDeadPrefixes is skipped, isolating the throw to the
-      // fetchCountRows catch we narrowed. The count query (the GROUP BY one)
-      // throws a column-level error (SQLSTATE 42703) — the exact class the
-      // old bare `catch {}` swallowed into 0 rows; everything else succeeds.
-      __setPackLocatorForTests(() => null);
-      const boom = Object.assign(new Error('column "type" does not exist'), { code: '42703' });
-      const stubEngine = {
-        executeRaw: async (sql: string) => {
-          if (/GROUP BY source_id/.test(sql)) throw boom;  // the fetchCountRows query
-          return [];
-        },
-      } as unknown as PGLiteEngine;
-      const ctx = { ...ctxOf(), engine: stubEngine } as unknown as OperationContext;
-      await expect(runStatsCore(ctx)).rejects.toThrow('column "type" does not exist');
-    });
-  });
-
-  it('fetchCountRows still degrades to empty (no throw) on a genuine missing pages table', async () => {
-    await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {
-      // Pre-init brain shape: the count query hits a missing pages table
-      // (SQLSTATE 42P01). This is the ONLY case the narrowed catch swallows.
-      __setPackLocatorForTests(() => null);
-      const missing = Object.assign(new Error('relation "pages" does not exist'), { code: '42P01' });
-      const stubEngine = {
-        executeRaw: async (sql: string) => {
-          if (/GROUP BY source_id/.test(sql)) throw missing;
-          return [];
-        },
-      } as unknown as PGLiteEngine;
-      const ctx = { ...ctxOf(), engine: stubEngine } as unknown as OperationContext;
-      const result = await runStatsCore(ctx);
-      expect(result.aggregate.total_pages).toBe(0);
-      expect(result.per_source).toEqual([]);
-    });
-  });
-
-  it('detectDeadPrefixes rethrows a non-missing-table error (sibling catch)', async () => {
-    await withEnv({ GBRAIN_HOME: tmpDir, GBRAIN_SCHEMA_PACK: 'tiny' }, async () => {
-      seedTinyPack('tiny', [{ name: 'person', prefix: 'people/' }]);
-      // fetchCountRows (the GROUP BY query) succeeds → []; the per-prefix
-      // dead-prefix LIKE query then throws a non-missing-table error, which
-      // must surface through the narrowed sibling catch.
-      const stubEngine = {
-        executeRaw: async (sql: string) => {
-          if (/GROUP BY source_id/.test(sql)) return [];        // count query: empty brain, fine
-          throw Object.assign(new Error('division by zero'), { code: '22012' });  // the LIKE query
-        },
-      } as unknown as PGLiteEngine;
-      const ctx = { ...ctxOf(), engine: stubEngine } as unknown as OperationContext;
-      await expect(runStatsCore(ctx)).rejects.toThrow('division by zero');
-    });
-  });
-});
-
 describe('runStatsCore — type/untyped split', () => {
   it('treats empty-string type as untyped (not its own bucket)', async () => {
     await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {

test/skillopt/version-store.test.ts

@@ -12,9 +12,11 @@ import {
   bestPath,
   historyPath,
   loadHistory,
+  proposedPath,
   revertAllPending,
   skillPath,
   versionsDir,
+  writeProposed,
 } from '../../src/core/skillopt/version-store.ts';
 
 let tmpDir: string;
@@ -79,6 +81,19 @@ describe('acceptCandidate (D8 two-phase commit)', () => {
   });
 });
 
+describe('writeProposed', () => {
+  test('writes distinct best and proposed artifacts without mutating SKILL.md (#2635)', () => {
+    const candidate = '---\nname: test\n---\nproposed body\n';
+
+    const written = writeProposed(tmpDir, SKILL, candidate);
+
+    expect(written).toBe(proposedPath(tmpDir, SKILL));
+    expect(fs.readFileSync(bestPath(tmpDir, SKILL), 'utf8')).toBe(candidate);
+    expect(fs.readFileSync(proposedPath(tmpDir, SKILL), 'utf8')).toBe(candidate);
+    expect(fs.readFileSync(skillPath(tmpDir, SKILL), 'utf8')).toContain('baseline body');
+  });
+});
+
 describe('revertAllPending (D8 crash recovery)', () => {
   test('no-op when no pending rows', () => {
     const reverted = revertAllPending(tmpDir, SKILL);