diff --git a/test/autoplan-scope-diagnostic.test.ts b/test/autoplan-scope-diagnostic.test.ts
new file mode 100644
index 000000000..b48a59397
--- /dev/null
+++ b/test/autoplan-scope-diagnostic.test.ts
@@ -0,0 +1,51 @@
+/**
+ * /autoplan Phase 0 scope-detection diagnostic (gate tier)
+ *
+ * Phase 0 decides whether to run the Design (Phase 2) and DX (Phase 3.5)
+ * reviews by grepping the plan for scope terms with a 2-match threshold.
+ * Before #1957 a below-threshold result silently dropped the phase: no count,
+ * no near-miss warning, no way to override. These static checks pin the
+ * generated skill so the diagnostic can't quietly regress.
+ */
+
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'fs';
+import * as path from 'path';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+const AUTOPLAN = fs.readFileSync(path.join(ROOT, 'autoplan', 'SKILL.md'), 'utf-8');
+const AUTOPLAN_TMPL = fs.readFileSync(path.join(ROOT, 'autoplan', 'SKILL.md.tmpl'), 'utf-8');
+
+describe('autoplan Phase 0 scope diagnostic', () => {
+  test('detection reports the match count, not just yes/no', () => {
+    expect(AUTOPLAN).toContain('match COUNT');
+    // The skip-visibility instruction must be present.
+    expect(AUTOPLAN).toMatch(/never skip a phase\s+silently/);
+  });
+
+  test('a below-threshold scope is surfaced as a near-miss, not a clean no', () => {
+    expect(AUTOPLAN).toContain('near-miss');
+    // The known false-negative triggers from the issue are named so the agent
+    // knows what to look for.
+    expect(AUTOPLAN).toContain('form-control');
+  });
+
+  test('an exactly-at-threshold scope is flagged as borderline', () => {
+    expect(AUTOPLAN).toMatch(/exactly 2 matches is borderline/);
+  });
+
+  test('the user is offered an override to force a skipped phase', () => {
+    expect(AUTOPLAN).toContain('tell me to force');
+  });
+
+  test('the Phase 0 output line surfaces the counts and the override note', () => {
+    expect(AUTOPLAN).toMatch(/UI scope: \[yes\/no\] \(\[N\] matches\)/);
+    expect(AUTOPLAN).toMatch(/DX scope: \[yes\/no\] \(\[N\] matches\)/);
+  });
+
+  test('template and generated skill stay in sync on the diagnostic', () => {
+    for (const needle of ['match COUNT', 'near-miss', 'tell me to force']) {
+      expect(AUTOPLAN_TMPL).toContain(needle);
+    }
+  });
+});