diff --git a/packages/squad-cli/src/cli/core/nap.ts b/packages/squad-cli/src/cli/core/nap.ts
index 6466879a9..9685ddebd 100644
--- a/packages/squad-cli/src/cli/core/nap.ts
+++ b/packages/squad-cli/src/cli/core/nap.ts
@@ -31,7 +31,7 @@ export interface NapMetrics {
 }
 
 export interface NapAction {
-  type: 'compress' | 'prune' | 'archive' | 'merge' | 'cleanup';
+  type: 'compress' | 'prune' | 'archive' | 'merge' | 'cleanup' | 'warning';
   target: string;
   description: string;
   bytesSaved: number;
@@ -97,6 +97,19 @@ function humanTokens(bytes: number): string {
   return `${(tokens / 1000).toFixed(0)}K`;
 }
 
+/** Build a warning action when decisions.md is oversized but nothing was archivable. */
+function oversizedDecisionsWarning(squadDir: string): NapAction | null {
+  const decisionsPath = path.join(squadDir, 'decisions.md');
+  const decisionsSize = fileSize(decisionsPath);
+  if (decisionsSize <= DECISION_THRESHOLD) return null;
+  return {
+    type: 'warning',
+    target: decisionsPath,
+    description: `⚠️ decisions.md is ${humanBytes(decisionsSize)} but no entries could be archived (all recent or undated). Consider manual cleanup or adding dates to undated entries.`,
+    bytesSaved: 0,
+  };
+}
+
 function daysAgoFromLine(line: string): number | null {
   // Match dates like 2026-02-28 or ### 2026-02-28
   const m = line.match(/(\d{4}-\d{2}-\d{2})/);
@@ -472,7 +485,12 @@ export async function runNap(options: NapOptions): Promise<NapResult> {
 
     // Decision archival
     const archiveAction = archiveDecisions(squadDir, dryRun);
-    if (archiveAction) actions.push(archiveAction);
+    if (archiveAction) {
+      actions.push(archiveAction);
+    } else {
+      const warning = oversizedDecisionsWarning(squadDir);
+      if (warning) actions.push(warning);
+    }
 
   } finally {
     if (!dryRun) removeJournal(squadDir);
@@ -524,7 +542,12 @@ export function runNapSync(options: NapOptions): NapResult {
     actions.push(...cleanInbox(squadDir, dryRun));
 
     const archiveAction = archiveDecisions(squadDir, dryRun);
-    if (archiveAction) actions.push(archiveAction);
+    if (archiveAction) {
+      actions.push(archiveAction);
+    } else {
+      const warning = oversizedDecisionsWarning(squadDir);
+      if (warning) actions.push(warning);
+    }
   } finally {
     if (!dryRun) removeJournal(squadDir);
   }
diff --git a/test/nap.test.ts b/test/nap.test.ts
index 437b5a3f2..3422c6b3e 100644
--- a/test/nap.test.ts
+++ b/test/nap.test.ts
@@ -510,6 +510,52 @@ describe('Nap — Decision archival', () => {
     expect(archiveActions).toHaveLength(0);
     expect(existsSync(join(squadDir, 'decisions-archive.md'))).toBe(false);
   });
+  it('warns when decisions.md is over threshold but nothing is archivable', async () => {
+    // decisions.md >20KB with ONLY header content — no ### entries at all.
+    // archiveDecisions() finds no entries and returns null, but the file is oversized.
+    const headerOnly = '# Decisions\n\n' + 'x'.repeat(21 * 1024);
+    expect(Buffer.byteLength(headerOnly)).toBeGreaterThan(20 * 1024);
+
+    const squadDir = createTestSquadDir({ 'decisions.md': headerOnly });
+    const result = await runNap({ squadDir, dryRun: true });
+
+    const warnActions = result.actions.filter(
+      (a) => a.type === 'warning' && a.target.includes('decisions'),
+    );
+    expect(warnActions).toHaveLength(1);
+    expect(warnActions[0]!.bytesSaved).toBe(0);
+    expect(warnActions[0]!.description).toContain('no entries could be archived');
+  });
+
+  it('no warning when decisions.md is under threshold', async () => {
+    const smallContent = '# Decisions\n\n' + 'x'.repeat(5 * 1024);
+    expect(Buffer.byteLength(smallContent)).toBeLessThan(20 * 1024);
+
+    const squadDir = createTestSquadDir({ 'decisions.md': smallContent });
+    const result = await runNap({ squadDir });
+
+    const warnActions = result.actions.filter((a) => a.type === 'warning');
+    expect(warnActions).toHaveLength(0);
+  });
+
+  it('no warning when archival succeeds', async () => {
+    // decisions.md >20KB with old entries that DO get archived
+    let bigOldDecisions = '# Decisions\n\n';
+    for (let i = 0; i < 30; i++) {
+      bigOldDecisions += `### 2024-01-${String(i + 1).padStart(2, '0')}: Decision ${i + 1}\n`;
+      bigOldDecisions += 'w'.repeat(800) + '\n\n';
+    }
+    expect(Buffer.byteLength(bigOldDecisions)).toBeGreaterThan(20 * 1024);
+
+    const squadDir = createTestSquadDir({ 'decisions.md': bigOldDecisions });
+    const result = await runNap({ squadDir });
+
+    const archiveActions = result.actions.filter((a) => a.type === 'archive');
+    expect(archiveActions.length).toBeGreaterThan(0);
+
+    const warnActions = result.actions.filter((a) => a.type === 'warning');
+    expect(warnActions).toHaveLength(0);
+  });
 });
 
 // ============================================================================