diff --git a/.changeset/soft-jade-quartz.md b/.changeset/soft-jade-quartz.md
new file mode 100644
index 000000000..4be7e3bce
--- /dev/null
+++ b/.changeset/soft-jade-quartz.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 3371
+---
+**`gsd-tools validate health` and `validate consistency` no longer flag sentinel phase directories (999.x backlog/interim, 0.x drafts)** — the disk-vs-roadmap comparison now applies the `isSentinelPhaseId` guard that the phase commands already had. Sentinel ids are defined as never-on-roadmap, so a `999-interim` directory previously produced a permanent spurious W007 ("Phase 999 exists on disk but not in ROADMAP.md", advice to add it to the roadmap or delete it — both wrong) and a spurious "Gap in phase numbering: N → 999". Real (non-sentinel) orphans and genuine numbering gaps still warn. (#3225)
diff --git a/src/verify.cts b/src/verify.cts
index 011b9fcf3..a98ef09ce 100644
--- a/src/verify.cts
+++ b/src/verify.cts
@@ -46,7 +46,7 @@ import configLoaderMod = require('./config-loader.cjs');
 const { loadConfig, CONFIG_DEFAULTS } = configLoaderMod;
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import phaseIdMod = require('./phase-id.cjs');
-const { normalizePhaseName, phaseTokenMatches, escapeRegex, getMilestoneFromPhaseId, OPTIONAL_PHASE_TAG_SOURCE, PHASE_NUMBER_TOKEN_SOURCE, extractPhaseToken, comparePhaseNum } = phaseIdMod;
+const { normalizePhaseName, phaseTokenMatches, escapeRegex, getMilestoneFromPhaseId, OPTIONAL_PHASE_TAG_SOURCE, PHASE_NUMBER_TOKEN_SOURCE, extractPhaseToken, comparePhaseNum, isSentinelPhaseId } = phaseIdMod;
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import phaseLocatorMod = require('./phase-locator.cjs');
 const { findPhaseInternal } = phaseLocatorMod;
@@ -1442,12 +1442,17 @@ function cmdValidateConsistency(cwd: string, raw: boolean): void {
   const diskPhases = collectDiskPhases(planBase);
 
   for (const p of roadmapPhases) {
+    // #3225: sentinel phase ids are never-on-roadmap by convention.
+    if (isSentinelPhaseId(p)) continue;
     if (!diskPhases.has(p) && !diskPhases.has(normalizePhaseName(p))) {
       warnings.push(`Phase ${p} in ROADMAP.md but no directory on disk`);
     }
   }
 
   for (const p of diskPhases) {
+    // #3225: a sentinel dir on disk (999-interim, 0-drafts) is defined as
+    // never-on-roadmap; it must not warn here (same guard as cmdValidateHealth).
+    if (isSentinelPhaseId(p)) continue;
     const variants = phaseVariants(p);
     if (![...variants].some((v) => fullRoadmapPhaseVariants.has(v))) {
       warnings.push(`Phase ${p} exists on disk but not in ROADMAP.md`);
@@ -1457,7 +1462,10 @@ function cmdValidateConsistency(cwd: string, raw: boolean): void {
   const config = loadConfig(cwd);
   if (config.phase_naming !== 'custom') {
     const integerPhases = [...diskPhases]
-      .filter((p) => !p.includes('.'))
+      // #3225: exclude sentinel phase ids (999.x/0.x) — they are never part of the
+      // sequential numbering, so a 999-interim dir must not produce a spurious
+      // "Gap in phase numbering: N → 999".
+      .filter((p) => !p.includes('.') && !isSentinelPhaseId(p))
       .map((p) => parseInt(p, 10))
       .sort((a, b) => a - b);
 
@@ -1990,6 +1998,9 @@ function cmdValidateHealth(
     const notStartedPhases = buildNotStartedPhaseVariants(roadmapContent);
 
     for (const p of roadmapPhases) {
+      // #3225: sentinel phase ids (999.x/0.x) are never-on-roadmap by convention;
+      // a sentinel heading shouldn't demand a directory.
+      if (isSentinelPhaseId(p)) continue;
       const variants = phaseVariants(p);
       const existsOnDisk = [...variants].some((v) => diskPhases.has(v));
       if (!existsOnDisk) {
@@ -2005,6 +2016,11 @@ function cmdValidateHealth(
     }
 
     for (const p of activeDiskPhases) {
+      // #3225: a sentinel dir on disk (999-interim, 0-drafts) is defined as
+      // never-on-roadmap; it must not trigger W007 ("Add to roadmap or remove
+      // directory" — both wrong for a sentinel). Mirrors the isSentinelPhaseId
+      // guard phase.cts has at 10+ sites (#2786/#2949).
+      if (isSentinelPhaseId(p)) continue;
       const variants = phaseVariants(p);
       if (![...variants].some((v) => fullRoadmapPhaseVariants.has(v))) {
         addIssue(
diff --git a/tests/verify-health.test.cjs b/tests/verify-health.test.cjs
index b09f492a4..26c5fa612 100644
--- a/tests/verify-health.test.cjs
+++ b/tests/verify-health.test.cjs
@@ -977,6 +977,41 @@ describe('validate health command', () => {
     assert.strictEqual(output.errors.length, 0, 'should have no errors');
     assert.ok(output.warnings.length > 0, 'should have warnings');
   });
+
+  // #3225: sentinel phase dirs (999.x backlog/interim, 0.x drafts) are defined as
+  // never-on-roadmap (SENTINEL_RANGES=[0,999]). The W006/W007 disk↔roadmap loops
+  // never had the isSentinelPhaseId guard that phase.cts has, so every sentinel dir
+  // produced a spurious W007 with wrong fix advice ("Add to roadmap or remove
+  // directory"). Sentinels must be excluded; a real (non-sentinel) orphan must still warn.
+  test('#3225: sentinel phase dirs (999/0) do not trigger W007; real orphans still do', () => {
+    writeMinimalRoadmap(tmpDir, ['1']);
+    writeMinimalStateMd(tmpDir);
+    writeValidConfigJson(tmpDir);
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-a'), { recursive: true });
+    // Sentinel dirs — never-on-roadmap by convention.
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '999-interim'), { recursive: true });
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '0-drafts'), { recursive: true });
+    // A real orphan (non-sentinel) that SHOULD still trigger W007.
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '77-orphan'), { recursive: true });
+
+    const result = runGsdTools('validate health', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+    const output = JSON.parse(result.output);
+
+    const sentinelW007s = output.warnings.filter(
+      w => w.code === 'W007' && /\b(0|999)\b/.test(w.message)
+    );
+    assert.strictEqual(
+      sentinelW007s.length, 0,
+      `sentinel phase dirs must not trigger W007; got: ${JSON.stringify(sentinelW007s)}`
+    );
+
+    // Negative space: the non-sentinel orphan must still be flagged.
+    assert.ok(
+      output.warnings.some(w => w.code === 'W007' && /77\b/.test(w.message)),
+      `expected W007 for the real orphan 77; got: ${JSON.stringify(output.warnings.filter(w => w.code === 'W007'))}`
+    );
+  });
 });
 
 // ─────────────────────────────────────────────────────────────────────────────
diff --git a/tests/verify.test.cjs b/tests/verify.test.cjs
index d6e33bd89..0e45d74a0 100644
--- a/tests/verify.test.cjs
+++ b/tests/verify.test.cjs
@@ -102,6 +102,46 @@ describe('validate consistency command', () => {
     );
   });
 
+  test('#3225: sentinel phase dirs (999/0) do not warn; real orphans still do', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'ROADMAP.md'),
+      `# Roadmap\n### Phase 1: A\n`
+    );
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-a'), { recursive: true });
+    // Sentinel dirs — never-on-roadmap by convention (SENTINEL_RANGES=[0,999]).
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '999-interim'), { recursive: true });
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '0-drafts'), { recursive: true });
+    // A real orphan (non-sentinel) that SHOULD still warn.
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '02-orphan'), { recursive: true });
+
+    const result = runGsdTools('validate consistency', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+    const output = JSON.parse(result.output);
+
+    const sentinelWarnings = output.warnings.filter(
+      w => w.includes('disk but not in ROADMAP') && /\b(0|999)\b/.test(w)
+    );
+    assert.strictEqual(
+      sentinelWarnings.length, 0,
+      `sentinel phase dirs must not warn; got: ${JSON.stringify(sentinelWarnings)}`
+    );
+    // Negative space: the real orphan must still warn.
+    assert.ok(
+      output.warnings.some(w => w.includes('disk but not in ROADMAP') && /02\b/.test(w)),
+      `expected a warning for the real orphan 02; got: ${JSON.stringify(output.warnings)}`
+    );
+    // #3225 (review finding): a sentinel dir must NOT produce a spurious
+    // "Gap in phase numbering: N → 999" either (the gap check builds its integer
+    // sequence from diskPhases and would otherwise include 999).
+    const sentinelGaps = output.warnings.filter(
+      w => w.includes('Gap in phase numbering') && /999\b/.test(w)
+    );
+    assert.strictEqual(
+      sentinelGaps.length, 0,
+      `sentinel 999 must not create a spurious numbering gap; got: ${JSON.stringify(sentinelGaps)}`
+    );
+  });
+
   test('warns about gaps in phase numbering', () => {
     fs.writeFileSync(
       path.join(tmpDir, '.planning', 'ROADMAP.md'),