diff --git a/tests/core.test.cjs b/tests/core.test.cjs
index 368c1d801..3210ece34 100644
--- a/tests/core.test.cjs
+++ b/tests/core.test.cjs
@@ -247,3 +247,394 @@ describe('resolveModelInternal', () => {
     });
   });
 });
+
+// ─── escapeRegex ───────────────────────────────────────────────────────────────
+
+describe('escapeRegex', () => {
+  test('escapes dots', () => {
+    assert.strictEqual(escapeRegex('file.txt'), 'file\\.txt');
+  });
+
+  test('escapes all special regex characters', () => {
+    const input = '1.0 (alpha) [test] {ok} $100 ^start end$ a+b a*b a?b pipe|or back\\slash';
+    const result = escapeRegex(input);
+    // Verify each special char is escaped
+    assert.ok(result.includes('\\.'));
+    assert.ok(result.includes('\\('));
+    assert.ok(result.includes('\\)'));
+    assert.ok(result.includes('\\['));
+    assert.ok(result.includes('\\]'));
+    assert.ok(result.includes('\\{'));
+    assert.ok(result.includes('\\}'));
+    assert.ok(result.includes('\\$'));
+    assert.ok(result.includes('\\^'));
+    assert.ok(result.includes('\\+'));
+    assert.ok(result.includes('\\*'));
+    assert.ok(result.includes('\\?'));
+    assert.ok(result.includes('\\|'));
+    assert.ok(result.includes('\\\\'));
+  });
+
+  test('handles empty string', () => {
+    assert.strictEqual(escapeRegex(''), '');
+  });
+
+  test('returns plain string unchanged', () => {
+    assert.strictEqual(escapeRegex('hello'), 'hello');
+  });
+});
+
+// ─── generateSlugInternal ──────────────────────────────────────────────────────
+
+describe('generateSlugInternal', () => {
+  test('converts text to lowercase kebab-case', () => {
+    assert.strictEqual(generateSlugInternal('Hello World'), 'hello-world');
+  });
+
+  test('removes special characters', () => {
+    assert.strictEqual(generateSlugInternal('core.cjs Tests!'), 'core-cjs-tests');
+  });
+
+  test('trims leading and trailing hyphens', () => {
+    assert.strictEqual(generateSlugInternal('---hello---'), 'hello');
+  });
+
+  test('returns null for null input', () => {
+    assert.strictEqual(generateSlugInternal(null), null);
+  });
+
+  test('returns null for empty string', () => {
+    assert.strictEqual(generateSlugInternal(''), null);
+  });
+});
+
+// ─── normalizePhaseName ────────────────────────────────────────────────────────
+
+describe('normalizePhaseName', () => {
+  test('pads single digit', () => {
+    assert.strictEqual(normalizePhaseName('1'), '01');
+  });
+
+  test('preserves double digit', () => {
+    assert.strictEqual(normalizePhaseName('12'), '12');
+  });
+
+  test('handles letter suffix', () => {
+    assert.strictEqual(normalizePhaseName('1A'), '01A');
+  });
+
+  test('handles decimal phases', () => {
+    assert.strictEqual(normalizePhaseName('2.1'), '02.1');
+  });
+
+  test('handles multi-level decimals', () => {
+    assert.strictEqual(normalizePhaseName('1.2.3'), '01.2.3');
+  });
+
+  test('returns non-matching input unchanged', () => {
+    assert.strictEqual(normalizePhaseName('abc'), 'abc');
+  });
+});
+
+// ─── comparePhaseNum ───────────────────────────────────────────────────────────
+
+describe('comparePhaseNum', () => {
+  test('sorts integer phases numerically', () => {
+    assert.ok(comparePhaseNum('1', '2') < 0);
+    assert.ok(comparePhaseNum('10', '2') > 0);
+  });
+
+  test('sorts letter suffixes', () => {
+    assert.ok(comparePhaseNum('12', '12A') < 0);
+    assert.ok(comparePhaseNum('12A', '12B') < 0);
+  });
+
+  test('sorts decimal phases', () => {
+    assert.ok(comparePhaseNum('2', '2.1') < 0);
+    assert.ok(comparePhaseNum('2.1', '2.2') < 0);
+  });
+
+  test('handles multi-level decimals', () => {
+    assert.ok(comparePhaseNum('1.1', '1.1.2') < 0);
+    assert.ok(comparePhaseNum('1.1.2', '1.2') < 0);
+  });
+
+  test('returns 0 for equal phases', () => {
+    assert.strictEqual(comparePhaseNum('1', '1'), 0);
+    assert.strictEqual(comparePhaseNum('2.1', '2.1'), 0);
+  });
+});
+
+// ─── safeReadFile ──────────────────────────────────────────────────────────────
+
+describe('safeReadFile', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-core-test-'));
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  test('reads existing file', () => {
+    const filePath = path.join(tmpDir, 'test.txt');
+    fs.writeFileSync(filePath, 'hello world');
+    assert.strictEqual(safeReadFile(filePath), 'hello world');
+  });
+
+  test('returns null for missing file', () => {
+    assert.strictEqual(safeReadFile('/nonexistent/path/file.txt'), null);
+  });
+});
+
+// ─── pathExistsInternal ────────────────────────────────────────────────────────
+
+describe('pathExistsInternal', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-core-test-'));
+    fs.mkdirSync(path.join(tmpDir, '.planning'), { recursive: true });
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  test('returns true for existing path', () => {
+    assert.strictEqual(pathExistsInternal(tmpDir, '.planning'), true);
+  });
+
+  test('returns false for non-existing path', () => {
+    assert.strictEqual(pathExistsInternal(tmpDir, 'nonexistent'), false);
+  });
+
+  test('handles absolute paths', () => {
+    assert.strictEqual(pathExistsInternal(tmpDir, tmpDir), true);
+  });
+});
+
+// ─── getMilestoneInfo ──────────────────────────────────────────────────────────
+
+describe('getMilestoneInfo', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-core-test-'));
+    fs.mkdirSync(path.join(tmpDir, '.planning'), { recursive: true });
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  test('extracts version and name from roadmap', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '# Roadmap\n\n## Roadmap v1.2: My Cool Project\n\nSome content'
+    );
+    const info = getMilestoneInfo(tmpDir);
+    assert.strictEqual(info.version, 'v1.2');
+    assert.strictEqual(info.name, 'My Cool Project');
+  });
+
+  test('returns defaults when roadmap missing', () => {
+    const info = getMilestoneInfo(tmpDir);
+    assert.strictEqual(info.version, 'v1.0');
+    assert.strictEqual(info.name, 'milestone');
+  });
+});
+
+// ─── searchPhaseInDir ──────────────────────────────────────────────────────────
+
+describe('searchPhaseInDir', () => {
+  let tmpDir;
+  let phasesDir;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-core-test-'));
+    phasesDir = path.join(tmpDir, 'phases');
+    fs.mkdirSync(phasesDir, { recursive: true });
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  test('finds phase directory by normalized prefix', () => {
+    fs.mkdirSync(path.join(phasesDir, '01-foundation'));
+    const result = searchPhaseInDir(phasesDir, '.planning/phases', '01');
+    assert.strictEqual(result.found, true);
+    assert.strictEqual(result.phase_number, '01');
+    assert.strictEqual(result.phase_name, 'foundation');
+  });
+
+  test('returns plans and summaries', () => {
+    const phaseDir = path.join(phasesDir, '01-foundation');
+    fs.mkdirSync(phaseDir);
+    fs.writeFileSync(path.join(phaseDir, '01-01-PLAN.md'), '# Plan');
+    fs.writeFileSync(path.join(phaseDir, '01-01-SUMMARY.md'), '# Summary');
+    const result = searchPhaseInDir(phasesDir, '.planning/phases', '01');
+    assert.ok(result.plans.includes('01-01-PLAN.md'));
+    assert.ok(result.summaries.includes('01-01-SUMMARY.md'));
+    assert.strictEqual(result.incomplete_plans.length, 0);
+  });
+
+  test('identifies incomplete plans', () => {
+    const phaseDir = path.join(phasesDir, '01-foundation');
+    fs.mkdirSync(phaseDir);
+    fs.writeFileSync(path.join(phaseDir, '01-01-PLAN.md'), '# Plan 1');
+    fs.writeFileSync(path.join(phaseDir, '01-02-PLAN.md'), '# Plan 2');
+    fs.writeFileSync(path.join(phaseDir, '01-01-SUMMARY.md'), '# Summary 1');
+    const result = searchPhaseInDir(phasesDir, '.planning/phases', '01');
+    assert.strictEqual(result.incomplete_plans.length, 1);
+    assert.ok(result.incomplete_plans.includes('01-02-PLAN.md'));
+  });
+
+  test('detects research and context files', () => {
+    const phaseDir = path.join(phasesDir, '01-foundation');
+    fs.mkdirSync(phaseDir);
+    fs.writeFileSync(path.join(phaseDir, '01-RESEARCH.md'), '# Research');
+    fs.writeFileSync(path.join(phaseDir, '01-CONTEXT.md'), '# Context');
+    const result = searchPhaseInDir(phasesDir, '.planning/phases', '01');
+    assert.strictEqual(result.has_research, true);
+    assert.strictEqual(result.has_context, true);
+  });
+
+  test('returns null when phase not found', () => {
+    fs.mkdirSync(path.join(phasesDir, '01-foundation'));
+    const result = searchPhaseInDir(phasesDir, '.planning/phases', '99');
+    assert.strictEqual(result, null);
+  });
+
+  test('generates phase_slug from directory name', () => {
+    fs.mkdirSync(path.join(phasesDir, '01-core-cjs-tests'));
+    const result = searchPhaseInDir(phasesDir, '.planning/phases', '01');
+    assert.strictEqual(result.phase_slug, 'core-cjs-tests');
+  });
+});
+
+// ─── findPhaseInternal ─────────────────────────────────────────────────────────
+
+describe('findPhaseInternal', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-core-test-'));
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases'), { recursive: true });
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  test('finds phase in current phases directory', () => {
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-foundation'));
+    const result = findPhaseInternal(tmpDir, '1');
+    assert.strictEqual(result.found, true);
+    assert.strictEqual(result.phase_number, '01');
+  });
+
+  test('returns null for non-existent phase', () => {
+    const result = findPhaseInternal(tmpDir, '99');
+    assert.strictEqual(result, null);
+  });
+
+  test('returns null for null phase', () => {
+    const result = findPhaseInternal(tmpDir, null);
+    assert.strictEqual(result, null);
+  });
+
+  test('searches archived milestones when not in current', () => {
+    // Create archived milestone structure (no current phase match)
+    const archiveDir = path.join(tmpDir, '.planning', 'milestones', 'v1.0-phases', '01-foundation');
+    fs.mkdirSync(archiveDir, { recursive: true });
+    const result = findPhaseInternal(tmpDir, '1');
+    assert.strictEqual(result.found, true);
+    assert.strictEqual(result.archived, 'v1.0');
+  });
+});
+
+// ─── getRoadmapPhaseInternal ───────────────────────────────────────────────────
+
+describe('getRoadmapPhaseInternal', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-core-test-'));
+    fs.mkdirSync(path.join(tmpDir, '.planning'), { recursive: true });
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  // Bug: getRoadmapPhaseInternal was missing from module.exports
+  test('is exported from core.cjs (REG-02)', () => {
+    assert.strictEqual(typeof getRoadmapPhaseInternal, 'function');
+    // Also verify it works with a real roadmap (note: goal regex expects **Goal:** with colon inside bold)
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '### Phase 1: Foundation\n**Goal:** Build the base\n'
+    );
+    const result = getRoadmapPhaseInternal(tmpDir, '1');
+    assert.strictEqual(result.found, true);
+    assert.strictEqual(result.phase_name, 'Foundation');
+    assert.strictEqual(result.goal, 'Build the base');
+  });
+
+  test('extracts phase name and goal from roadmap', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '### Phase 2: API Layer\n**Goal:** Create REST endpoints\n**Depends on**: Phase 1\n'
+    );
+    const result = getRoadmapPhaseInternal(tmpDir, '2');
+    assert.strictEqual(result.phase_name, 'API Layer');
+    assert.strictEqual(result.goal, 'Create REST endpoints');
+  });
+
+  test('returns null goal when Goal uses colon-outside-bold format', () => {
+    // Actual ROADMAP.md uses **Goal**: (colon outside bold) which the regex does not match
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '### Phase 1: Foundation\n**Goal**: Build the base\n'
+    );
+    const result = getRoadmapPhaseInternal(tmpDir, '1');
+    assert.strictEqual(result.found, true);
+    assert.strictEqual(result.phase_name, 'Foundation');
+    assert.strictEqual(result.goal, null);
+  });
+
+  test('returns null when roadmap missing', () => {
+    const result = getRoadmapPhaseInternal(tmpDir, '1');
+    assert.strictEqual(result, null);
+  });
+
+  test('returns null when phase not in roadmap', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '### Phase 1: Foundation\n**Goal**: Build the base\n'
+    );
+    const result = getRoadmapPhaseInternal(tmpDir, '99');
+    assert.strictEqual(result, null);
+  });
+
+  test('returns null for null phase number', () => {
+    const result = getRoadmapPhaseInternal(tmpDir, null);
+    assert.strictEqual(result, null);
+  });
+
+  test('extracts full section text', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      '### Phase 1: Foundation\n**Goal**: Build the base\n**Requirements**: TEST-01\nSome details here\n\n### Phase 2: API\n**Goal**: REST\n'
+    );
+    const result = getRoadmapPhaseInternal(tmpDir, '1');
+    assert.ok(result.section.includes('Phase 1: Foundation'));
+    assert.ok(result.section.includes('Some details here'));
+    // Should not include Phase 2 content
+    assert.ok(!result.section.includes('Phase 2: API'));
+  });
+});