diff --git a/lib/review-depth.ts b/lib/review-depth.ts
index bce1fffef..6914a39c3 100644
--- a/lib/review-depth.ts
+++ b/lib/review-depth.ts
@@ -273,6 +273,7 @@ const forcedBy = (i: PlanInput) => (n: string) => i.force === 'all' || (Array.is
 /** The specialists a full pass selects for a class: class sets the eligible set, hit-rate gating applies inside it, gate class ignores gating. */
 export function specialistsFor(cls: DiffClass, i: PlanInput, skipped: string[] = []): Specialist[] {
   const s = i.scope ?? {};
+  const unknown = !!s.SCOPE_ERROR;
   const forced = forcedBy(i);
   if (cls === 'docs') { skipped.push('specialists (docs class)'); return SPECIALISTS.filter(forced); }
   if (cls === 'tests') { skipped.push('specialists except testing (tests class)'); return SPECIALISTS.filter(n => n === 'testing' || forced(n)); }
@@ -282,9 +283,9 @@ export function specialistsFor(cls: DiffClass, i: PlanInput, skipped: string[] =
     if (i.diffLines < SMALL_DIFF_LINES) return false;
     switch (n) {
       case 'testing': case 'maintainability': return true;
-      case 'security': return s.SCOPE_AUTH === 'true' || (s.SCOPE_BACKEND === 'true' && i.diffLines > LARGE_DIFF_LINES);
+      case 'security': return unknown || s.SCOPE_AUTH === 'true' || (s.SCOPE_BACKEND === 'true' && i.diffLines > LARGE_DIFF_LINES);
       case 'simplification': return i.diffLines > LARGE_DIFF_LINES;
-      default: return scopeWants[n]!(s);
+      default: return unknown || scopeWants[n]!(s);
     }
   };
   return SPECIALISTS.filter(n => {
diff --git a/lib/review-plan-live.ts b/lib/review-plan-live.ts
index 712beee09..3d04c072b 100644
--- a/lib/review-plan-live.ts
+++ b/lib/review-plan-live.ts
@@ -8,7 +8,7 @@
 import * as path from 'node:path';
 import { spawnSync } from 'node:child_process';
 import { runScriptSync } from './script-invocation';
-import { collectCommit, collectLive, type Collected } from './review-collect';
+import { collectCommit, collectLive, resolveBaseRef, type Collected } from './review-collect';
 import { classifyDiff, planReview, scanNumbers, SCOPED_RANGE_LINES, type Depth, type History, type ReviewPlan } from './review-depth';
 
 export interface PlanFlags {
@@ -90,7 +90,7 @@ export function livePlan(f: PlanFlags, binDir: string, bin: string): LivePlan |
     const m = /GATE_SUMMARY: .*?tagged=\{([^}]*)\}/.exec(g.stdout ?? '');
     return g.status === 0 && m ? m[1]!.split(',').reduce((n, kv) => n + (Number(kv.split(':')[1]) || 0), 0) : null;
   };
-  const scope = scopeOf([f.base]);
+  const scope = scopeOf([resolveBaseRef(root, f.base)]);
   let gateTagged = f.gateTagged !== undefined ? f.gateTagged : gateTagsOf([f.base]);
   if (gateTagged !== null && !Number.isFinite(gateTagged)) gateTagged = null;
   const tiersSetting = runScriptSync(path.join(binDir, 'gstack-config'), ['get', 'review_effort_tiers'], { encoding: 'utf8', timeout: 15_000 });
diff --git a/test/review-depth.test.ts b/test/review-depth.test.ts
index d7f10c1ab..323175d21 100644
--- a/test/review-depth.test.ts
+++ b/test/review-depth.test.ts
@@ -11,6 +11,15 @@ const none = scanNumbers({});
 const base = (o: Partial<PlanInput>): PlanInput => ({ paths: ['src/app.ts'], scope: { SCOPE_BACKEND: 'true', SCOPE_STATE_MACHINE: 'false' }, gateTagged: 0, diffLines: 120, history: { fullPasses: 0, last: 'none' }, numbers: none, ...o });
 const roles = (p: ReturnType<typeof planReview>) => p.dispatches.map(d => `${d.role}:${d.name}:${d.effort}`);
 
+describe('a scope error fails the specialist selection closed', () => {
+  // Value: protects=an unreadable diff scope selects every scope-gated specialist instead of none; fails_when=SCOPE_ERROR leaves all SCOPE_* false and security/performance drop silently;
+  //   why_new=GSTA-167 dogfood on #3633 (no local main); seam=none; no_claim=the scope tool's own errors
+  test('SCOPE_ERROR=no_base keeps security, performance, api-contract, data-migration and design', () => {
+    const names = planReview(base({ scope: { SCOPE_ERROR: 'no_base' }, diffLines: 1000 })).dispatches.filter(d => d.role === 'specialist').map(d => d.name);
+    for (const n of ['security', 'performance', 'api-contract', 'data-migration', 'design']) expect(names).toContain(n);
+  });
+});
+
 describe('classifyPath: agent-read markdown is code', () => {
   test.each([
     ['README.md', 'docs'], ['CHANGELOG.md', 'docs'], ['docs/howto-x.md', 'docs'], ['TODOS.md', 'docs'],
diff --git a/test/review-plan-cli.test.ts b/test/review-plan-cli.test.ts
index 1f7bc9128..ed804d350 100644
--- a/test/review-plan-cli.test.ts
+++ b/test/review-plan-cli.test.ts
@@ -41,6 +41,16 @@ describe('gstack-review-plan', () => {
     expect(plan.audit_effort).toBe('light');
     expect(JSON.parse(run(r, ['--json', '--no-tiers']).stdout).audit_effort).toBe('host');
   });
+  // Value: protects=the plan reads diff scope from origin/<base> like collectLive, so a clone with no local base branch keeps its scope-gated specialists; fails_when=gstack-diff-scope <base> fails on a missing local ref and security/performance silently drop;
+  //   why_new=GSTA-167 dogfood on #3633: a Capy checkout has no local main; seam=gstack-diff-scope; no_claim=which specialists a scope selects
+  test('no local base branch: scope comes from origin/<base> and the scope-gated specialists stay', () => {
+    const r = repo({ 'src/a.ts': Array.from({ length: 80 }, (_, i) => `export const v${i} = ${i};`).join('\n') + '\n' });
+    const git = (...a: string[]) => spawnSync('git', a, { cwd: r.dir, encoding: 'utf8', timeout: 10_000 });
+    git('update-ref', 'refs/remotes/origin/main', 'main'); git('branch', '-D', 'main');
+    const out = run(r, []).stdout;
+    expect(out).not.toContain('scope_error');
+    expect(out).toContain('DISPATCH: specialist performance');
+  });
   test('a below-floor fix after pass 1 plans one fix-check', () => {
     const r = run(repo({ 'src/a.ts': 'export const a = 1;\n' }), ['--pass', '1', '--last', 'full', '--fixed-below']);
     expect(r.stdout).toContain('next=fix-check dispatches=1');