diff --git a/v2/src/lib/utils/attention-scorer.test.ts b/v2/src/lib/utils/attention-scorer.test.ts
new file mode 100644
index 0000000..0f61d7e
--- /dev/null
+++ b/v2/src/lib/utils/attention-scorer.test.ts
@@ -0,0 +1,139 @@
+import { describe, it, expect } from 'vitest';
+import { scoreAttention, type AttentionInput } from './attention-scorer';
+
+function makeInput(overrides: Partial<AttentionInput> = {}): AttentionInput {
+  return {
+    sessionStatus: undefined,
+    sessionError: undefined,
+    activityState: 'inactive',
+    idleDurationMs: 0,
+    contextPressure: null,
+    fileConflictCount: 0,
+    externalConflictCount: 0,
+    ...overrides,
+  };
+}
+
+describe('scoreAttention', () => {
+  it('returns zero score when no attention needed', () => {
+    const result = scoreAttention(makeInput());
+    expect(result.score).toBe(0);
+    expect(result.reason).toBeNull();
+  });
+
+  it('scores error highest after stalled', () => {
+    const result = scoreAttention(makeInput({
+      sessionStatus: 'error',
+      sessionError: 'Connection refused',
+    }));
+    expect(result.score).toBe(90);
+    expect(result.reason).toContain('Connection refused');
+  });
+
+  it('truncates long error messages to 60 chars', () => {
+    const longError = 'A'.repeat(100);
+    const result = scoreAttention(makeInput({
+      sessionStatus: 'error',
+      sessionError: longError,
+    }));
+    expect(result.reason!.length).toBeLessThanOrEqual(68); // "Error: " + 60 chars + null safety
+  });
+
+  it('scores stalled at 100', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'stalled',
+      idleDurationMs: 20 * 60_000,
+    }));
+    expect(result.score).toBe(100);
+    expect(result.reason).toContain('20 min');
+  });
+
+  it('scores critical context pressure (>90%) at 80', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'running',
+      contextPressure: 0.95,
+    }));
+    expect(result.score).toBe(80);
+    expect(result.reason).toContain('95%');
+  });
+
+  it('scores file conflicts at 70', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'running',
+      fileConflictCount: 3,
+    }));
+    expect(result.score).toBe(70);
+    expect(result.reason).toContain('3 file conflicts');
+  });
+
+  it('includes external conflict note when present', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'running',
+      fileConflictCount: 2,
+      externalConflictCount: 1,
+    }));
+    expect(result.reason).toContain('(1 external)');
+  });
+
+  it('scores high context pressure (>75%) at 40', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'running',
+      contextPressure: 0.80,
+    }));
+    expect(result.score).toBe(40);
+    expect(result.reason).toContain('80%');
+  });
+
+  it('error takes priority over stalled', () => {
+    const result = scoreAttention(makeInput({
+      sessionStatus: 'error',
+      sessionError: 'fail',
+      activityState: 'stalled',
+      idleDurationMs: 30 * 60_000,
+    }));
+    expect(result.score).toBe(90);
+  });
+
+  it('stalled takes priority over context pressure', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'stalled',
+      idleDurationMs: 20 * 60_000,
+      contextPressure: 0.95,
+    }));
+    expect(result.score).toBe(100);
+  });
+
+  it('critical context takes priority over file conflicts', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'running',
+      contextPressure: 0.92,
+      fileConflictCount: 5,
+    }));
+    expect(result.score).toBe(80);
+  });
+
+  it('file conflicts take priority over high context', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'running',
+      contextPressure: 0.78,
+      fileConflictCount: 1,
+    }));
+    expect(result.score).toBe(70);
+  });
+
+  it('singular file conflict uses singular grammar', () => {
+    const result = scoreAttention(makeInput({
+      activityState: 'running',
+      fileConflictCount: 1,
+    }));
+    expect(result.reason).toBe('1 file conflict');
+  });
+
+  it('handles undefined session error gracefully', () => {
+    const result = scoreAttention(makeInput({
+      sessionStatus: 'error',
+      sessionError: undefined,
+    }));
+    expect(result.reason).toContain('Unknown');
+  });
+});