diff --git a/src/planning-snapshot.cts b/src/planning-snapshot.cts
index f7a5bba11..30219461a 100644
--- a/src/planning-snapshot.cts
+++ b/src/planning-snapshot.cts
@@ -135,6 +135,27 @@ interface PlanningSnapshot {
     scope: Scope;
   };
   planningRootFiles: { value: string[]; scope: Scope };
+  // W006/W007 (ROADMAP/disk consistency group) fidelity fix, found while
+  // implementing `src/health-diagnostic-rules/roadmap-disk-consistency.cts`:
+  // `phaseDirs` (Phase 10) is deliberately WINDOWED to the phases
+  // `listMilestonePhaseDirs`'s `inWindow` filter (`getMilestonePhaseFilter`,
+  // `src/roadmap-parser.cts:1220`) resolves as belonging to the CURRENT
+  // milestone window — a directory whose phase id is NOT declared anywhere
+  // in ROADMAP.md is EXCLUDED from `phaseDirs.value` by construction
+  // (`isDirInMilestone` membership test). That is exactly the directory
+  // W007 exists to find ("an on-disk phase dir has no matching ROADMAP
+  // entry"), so sourcing W007 from `phaseDirs.value` would make it
+  // structurally unable to fire on the very case it names: an orphan
+  // directory can never be a member of the set that is itself defined as
+  // "directories the roadmap already declares." `allPhaseDirNames` is the
+  // un-windowed twin — every directory actually present under the active
+  // `phases/` root, unfiltered by roadmap declaration (sentinel-id
+  // exclusion is left to the RULE, mirroring `verify.cts:2091`'s own
+  // per-entry `isSentinelPhaseId` guard rather than baking it into the
+  // field). Archived-milestone directories are out of scope here exactly as
+  // they already are for `phaseDirs` (see this batch's own disclosed
+  // fidelity reduction for that).
+  allPhaseDirNames: { value: string[]; scope: Scope };
 }
 
 /**
@@ -607,6 +628,29 @@ function buildPlanningRootFilesField(cwd: string): { value: string[]; scope: Sco
   }
 }
 
+/**
+ * Resolve `allPhaseDirNames` — every directory name directly under the
+ * active `phases/` root, UNFILTERED by `listMilestonePhaseDirs`'s
+ * current-milestone-window membership test (unlike `phaseDirs`). Backs
+ * W007 (see the field's own doc comment on `PlanningSnapshot` for why
+ * `phaseDirs` cannot). An absent `phases/` root is a real empty, not a
+ * failure (mirrors `listMilestonePhaseDirs`'s own treatment); a present but
+ * unreadable root degrades to `UNREADABLE` with an empty list.
+ */
+function buildAllPhaseDirNamesField(phasesDir: string): { value: string[]; scope: Scope } {
+  if (!fs.existsSync(phasesDir)) return { value: [], scope: SCOPE.COMPLETE };
+  try {
+    const value = fs
+      .readdirSync(phasesDir, { withFileTypes: true })
+      .filter((e) => e.isDirectory())
+      .map((e) => e.name)
+      .sort();
+    return { value, scope: SCOPE.COMPLETE };
+  } catch {
+    return { value: [], scope: SCOPE.UNREADABLE };
+  }
+}
+
 /**
  * Build the full `.planning/` projection for `cwd`. Composes the six §7
  * owners named in the design doc's "Owners consumed" table, plus (Phase 11,
@@ -642,6 +686,7 @@ function buildPlanningSnapshot(cwd: string): PlanningSnapshot {
     researchValidationStatus: buildResearchValidationStatusField(paths.phases, phaseDirs.value, phaseDirs.scope),
     milestoneArchiveStatus: buildMilestoneArchiveStatusField(cwd),
     planningRootFiles: buildPlanningRootFilesField(cwd),
+    allPhaseDirNames: buildAllPhaseDirNamesField(paths.phases),
   };
 }
 
diff --git a/tests/planning-snapshot.test.cjs b/tests/planning-snapshot.test.cjs
index ab9f9549b..50525f1b3 100644
--- a/tests/planning-snapshot.test.cjs
+++ b/tests/planning-snapshot.test.cjs
@@ -1048,3 +1048,45 @@ describe('planningRootFiles field (Phase 11, #3309)', () => {
     assert.deepStrictEqual(snap.planningRootFiles, { value: [], scope: SCOPE.UNREADABLE });
   });
 });
+
+describe('allPhaseDirNames field (Phase 11, #3309 — health-diagnostic-rules/roadmap-disk-consistency batch)', () => {
+  // Found while implementing W007 (`src/health-diagnostic-rules/
+  // roadmap-disk-consistency.cts`): `phaseDirs` is windowed to directories
+  // the ROADMAP already declares, so it can never expose a genuine orphan
+  // directory. `allPhaseDirNames` is the unwindowed twin.
+
+  test('happy: lists every directory under phases/, including one NOT declared anywhere in ROADMAP.md', (t) => {
+    const cwd = createTempDir('gsd-3309-apdn1-');
+    t.after(() => cleanup(cwd));
+    writeRoadmap(cwd, ['## v1.0 Current 🚧', '', '### Phase 1: Foo'].join('\n'));
+    fs.mkdirSync(path.join(planningDirOf(cwd), 'phases', '01-foo'), { recursive: true });
+    fs.mkdirSync(path.join(planningDirOf(cwd), 'phases', '04-extra'), { recursive: true }); // undeclared
+
+    const snap = buildPlanningSnapshot(cwd);
+    assert.deepStrictEqual(snap.allPhaseDirNames.value.slice().sort(), ['01-foo', '04-extra']);
+    assert.strictEqual(snap.allPhaseDirNames.scope, SCOPE.COMPLETE);
+    // Sanity: `phaseDirs` (windowed) must NOT include the undeclared dir —
+    // this is the exact gap `allPhaseDirNames` exists to close.
+    assert.ok(!snap.phaseDirs.value.includes('04-extra'));
+  });
+
+  test('absence: no phases/ directory at all is a real empty, not a failure', (t) => {
+    const cwd = createTempDir('gsd-3309-apdn2-');
+    t.after(() => cleanup(cwd));
+    writeRoadmap(cwd, ['## v1.0 Current 🚧', ''].join('\n'));
+
+    const snap = buildPlanningSnapshot(cwd);
+    assert.deepStrictEqual(snap.allPhaseDirNames, { value: [], scope: SCOPE.COMPLETE });
+  });
+
+  test('hostile: an unreadable phases/ directory degrades to an empty list, scope UNREADABLE, without throwing', (t) => {
+    const cwd = createTempDir('gsd-3309-apdn3-');
+    t.after(() => cleanup(cwd));
+    const phasesDir = path.join(planningDirOf(cwd), 'phases');
+    fs.mkdirSync(phasesDir, { recursive: true });
+    injectPhaseDirFault(t, phasesDir);
+
+    const snap = buildPlanningSnapshot(cwd);
+    assert.deepStrictEqual(snap.allPhaseDirNames, { value: [], scope: SCOPE.UNREADABLE });
+  });
+});