B5: learnings and timeline reads fail loudly when bun is missing

gstack-learnings-search and gstack-timeline-read ended in
'2>/dev/null || exit 0', so a missing bun or a crashed embedded script
printed nothing and exited 0, identical to 'nothing recorded'. Both now
exit 127 with '<script>: bun not found on PATH, so ... could not be
read. Fix: install Bun (https://bun.sh), then re-run ./setup.' and let
an embedded-script failure exit non-zero with its stderr. A successful
run with no matches still exits 0 with empty output. The generated
callers that print 'LEARNINGS: unavailable (...)' belong to the
generator lane.

Co-authored-by: loulanyue <260355617@qq.com>

bin/gstack-learnings-search

@@ -4,7 +4,9 @@
 #
 # Reads ~/.gstack/projects/$SLUG/learnings.jsonl, applies confidence decay,
 # resolves duplicates (latest winner per key+type), and outputs formatted text.
-# Exit 0 silently if no learnings file exists.
+# Exit 0 silently if no learnings file exists or nothing matches. Missing bun
+# exits 127 and a failed read exits non-zero with its stderr (#2790): "could
+# not read" must never look like "nothing recorded".
 set -euo pipefail
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 eval "$("$SCRIPT_DIR/gstack-slug" 2>/dev/null)"
@@ -45,6 +47,11 @@ if [ ! -f "$LEARNINGS_FILE" ] && [ ${#CROSS_FILES[@]} -eq 0 ]; then
   exit 0
 fi
 
+command -v bun >/dev/null 2>&1 || {
+  echo "gstack-learnings-search: bun not found on PATH, so learnings could not be read. Fix: install Bun (https://bun.sh), then re-run ./setup." >&2
+  exit 127
+}
+
 emit_tagged_file() {
   local tag="$1"
   local file="$2"
@@ -161,4 +168,4 @@ for (const [t, arr] of Object.entries(byType)) {
   }
   console.log('');
 }
-" 2>/dev/null || exit 0
+"

bin/gstack-timeline-read

@@ -4,7 +4,8 @@
 #
 # Session timeline: local-only, never sent anywhere.
 # Reads ~/.gstack/projects/$SLUG/timeline.jsonl, filters, formats.
-# Exit 0 silently if no timeline file exists.
+# Exit 0 silently if no timeline file exists or nothing matches. Missing bun
+# exits 127 and a failed read exits non-zero with its stderr (#2790).
 set -euo pipefail
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 eval "$("$SCRIPT_DIR/gstack-slug" 2>/dev/null)"
@@ -31,7 +32,12 @@ if [ ! -f "$TIMELINE_FILE" ]; then
   exit 0
 fi
 
-cat "$TIMELINE_FILE" 2>/dev/null | GSTACK_TIMELINE_SINCE="$SINCE" GSTACK_TIMELINE_BRANCH="$BRANCH" GSTACK_TIMELINE_LIMIT="$LIMIT" bun -e "
+command -v bun >/dev/null 2>&1 || {
+  echo "gstack-timeline-read: bun not found on PATH, so the timeline could not be read. Fix: install Bun (https://bun.sh), then re-run ./setup." >&2
+  exit 127
+}
+
+cat "$TIMELINE_FILE" | GSTACK_TIMELINE_SINCE="$SINCE" GSTACK_TIMELINE_BRANCH="$BRANCH" GSTACK_TIMELINE_LIMIT="$LIMIT" bun -e "
 const lines = (await Bun.stdin.text()).trim().split('\n').filter(Boolean);
 const since = process.env.GSTACK_TIMELINE_SINCE || '';
 const branch = process.env.GSTACK_TIMELINE_BRANCH || '';
@@ -95,4 +101,4 @@ for (const e of recent) {
   const outcome = e.outcome ? ' [' + e.outcome + ']' : '';
   console.log('- ' + ts + ' /' + e.skill + ' ' + e.event + outcome + dur + (e.branch ? ' on ' + e.branch : ''));
 }
-" 2>/dev/null || exit 0
+"

test/gstack-learnings-search.test.ts

@@ -2,7 +2,7 @@ import { describe, test, expect, beforeAll, afterAll } from 'bun:test';
 import * as fs from 'fs';
 import * as path from 'path';
 import * as os from 'os';
-import { execFileSync } from 'child_process';
+import { execFileSync, spawnSync } from 'child_process';
 
 const ROOT = path.resolve(import.meta.dir, '..');
 const BIN = path.join(ROOT, 'bin', 'gstack-learnings-search');
@@ -91,3 +91,53 @@ describe('gstack-learnings-search cross-project trust gating', () => {
     expect(out).not.toContain('foreign-legacy');
   });
 });
+
+// B5 (#2790): both query scripts ended in `2>/dev/null || exit 0`, so a
+// missing bun or a crashed embedded script printed nothing and exited 0,
+// exactly like "nothing recorded".
+describe('B5: query scripts never report a failed read as an empty result', () => {
+  const TOOLS = ['bash', 'sh', 'env', 'dirname', 'basename', 'git', 'tr', 'sed', 'cat', 'head', 'tail', 'grep', 'find',
+    'ls', 'mkdir', 'mktemp', 'mv', 'rm', 'cp', 'awk', 'wc', 'sort', 'uname', 'date', 'cut', 'readlink', 'realpath', 'stat', 'touch', 'id', 'printf'];
+  const shimDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-nobun-'));
+  const failDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-failbun-'));
+  for (const tool of TOOLS) {
+    const r = spawnSync('bash', ['-c', `command -v ${tool}`], { encoding: 'utf-8', timeout: 5000 });
+    const where = (r.stdout || '').trim();
+    if (where.startsWith('/')) fs.symlinkSync(where, path.join(shimDir, tool));
+  }
+  fs.writeFileSync(path.join(failDir, 'bun'), '#!/bin/sh\necho "embedded script exploded" >&2\nexit 3\n', { mode: 0o755 });
+  const timelineDir = path.join(tmpHome, 'projects', slug);
+  afterAll(() => {
+    fs.rmSync(shimDir, { recursive: true, force: true });
+    fs.rmSync(failDir, { recursive: true, force: true });
+  });
+
+  function runWith(script: string, pathValue: string, args: string[] = []) {
+    return spawnSync('bash', [path.join(ROOT, 'bin', script), ...args], {
+      timeout: 30_000, env: { ...process.env, GSTACK_HOME: tmpHome, PATH: pathValue }, cwd: tmpCwd, encoding: 'utf-8',
+    });
+  }
+
+  for (const script of ['gstack-learnings-search', 'gstack-timeline-read']) {
+    test(`${script}: bun missing exits 127 with the fix line`, () => {
+      fs.writeFileSync(path.join(timelineDir, 'timeline.jsonl'), JSON.stringify({ ts: '2026-05-01T00:00:00Z', skill: 'ship', event: 'started', branch: 'main' }) + '\n');
+      const r = runWith(script, shimDir);
+      expect(r.status).toBe(127);
+      expect(r.stdout).toBe('');
+      expect(r.stderr).toContain(`${script}: bun not found on PATH`);
+      expect(r.stderr).toContain('Fix: install Bun (https://bun.sh), then re-run ./setup.');
+    });
+
+    test(`${script}: a failing embedded script exits non-zero and keeps its stderr`, () => {
+      const r = runWith(script, `${failDir}:${process.env.PATH}`);
+      expect(r.status).not.toBe(0);
+      expect(r.stderr).toContain('embedded script exploded');
+    });
+  }
+
+  test('a successful search with no matches still exits 0 with empty output', () => {
+    const r = runWith('gstack-learnings-search', process.env.PATH!, ['--query', 'zzz-no-such-token']);
+    expect(r.status).toBe(0);
+    expect(r.stdout).toBe('');
+  });
+});