fix(core): allow intentional foreground sleep for backoff

integration-tests/cli/sleep-interception.test.ts

@@ -53,6 +53,25 @@ describe('sleep-interception', () => {
     expect(result.toLowerCase()).not.toContain('blocked');
   }, 30000);
 
+  it('should allow retrying blocked sleep with an intentional sleep comment', async () => {
+    rig = new TestRig();
+    await rig.setup('sleep-intentional-retry');
+
+    const result = await rig.run(
+      'Run this exact shell command first: sleep 5. ' +
+        'If the command is blocked, retry with this exact shell command: ' +
+        'sleep 2 # intentional-sleep: wait for MCP rate limit reset. ' +
+        'Then say "DONE".',
+    );
+
+    validateModelOutput(result, null, 'sleep intentional retry');
+
+    const foundShell = await rig.waitForToolCall('run_shell_command');
+    expect(foundShell).toBeTruthy();
+
+    expect(result.toLowerCase()).toContain('done');
+  }, 30000);
+
   it('should block sleep >= 2s even when followed by a trailing comment', async () => {
     // The `trimTrailingShellComment` state machine strips trailing `#...`
     // comments before matching the sleep pattern, so a model trying to

packages/core/src/tools/shell.test.ts

@@ -160,6 +160,32 @@ describe('ShellTool', () => {
       ).toThrow('Command cannot be empty.');
     });
 
+    it('should mention the intentional sleep escape hatch when blocking sleep', async () => {
+      const error = shellTool.validateToolParams({
+        command: 'sleep 5',
+        is_background: false,
+      });
+
+      expect(error).toContain('intentional-sleep:');
+    });
+
+    it('should explain rejected intentional sleep comments', async () => {
+      const shortReasonError = shellTool.validateToolParams({
+        command: 'sleep 5 # intentional-sleep: wait',
+        is_background: false,
+      });
+      const overCapError = shellTool.validateToolParams({
+        command:
+          'sleep 601s # intentional-sleep: wait for MCP rate limit reset',
+        is_background: false,
+      });
+
+      expect(shortReasonError).toContain('reason is too short');
+      expect(shortReasonError).not.toContain('add a trailing comment like');
+      expect(overCapError).toContain('foreground sleeps over 10 minutes');
+      expect(overCapError).not.toContain('add a trailing comment like');
+    });
+
     it('should throw an error for a relative directory path', async () => {
       expect(() =>
         shellTool.build({
@@ -5514,7 +5540,8 @@ describe('detectBlockedSleepPattern', () => {
 
   it('blocks sleep followed by a top-level shell comment', () => {
     // Shell ignores trailing comments, so these are equivalent to
-    // standalone foreground sleeps and must not bypass the guard.
+    // standalone foreground sleeps unless they use the explicit
+    // intentional-sleep escape hatch.
     expect(detectBlockedSleepPattern('sleep 5 # wait')).toBe(
       'standalone sleep 5',
     );
@@ -5529,6 +5556,69 @@ describe('detectBlockedSleepPattern', () => {
     );
   });
 
+  it('allows standalone sleep with an intentional sleep comment', () => {
+    expect(
+      detectBlockedSleepPattern(
+        'sleep 5 # intentional-sleep: wait for MCP rate limit reset',
+      ),
+    ).toBeNull();
+    expect(
+      detectBlockedSleepPattern(
+        'sleep 2s # intentional-sleep: deliberate rate limit backoff',
+      ),
+    ).toBeNull();
+    expect(
+      detectBlockedSleepPattern(
+        'sleep 10m # intentional-sleep: wait for MCP rate limit reset',
+      ),
+    ).toBeNull();
+  });
+
+  it('requires a meaningful intentional sleep reason', () => {
+    expect(detectBlockedSleepPattern('sleep 5 # intentional-sleep:')).toBe(
+      'standalone sleep 5',
+    );
+    expect(detectBlockedSleepPattern('sleep 5 # intentional-sleep: wait')).toBe(
+      'standalone sleep 5',
+    );
+    expect(
+      detectBlockedSleepPattern('sleep 5 # intentional-sleep: 1234567'),
+    ).toBe('standalone sleep 5');
+    expect(
+      detectBlockedSleepPattern('sleep 5 # intentional-sleep: 12345678'),
+    ).toBeNull();
+  });
+
+  it('blocks intentional sleep comments above the duration cap', () => {
+    expect(
+      detectBlockedSleepPattern(
+        'sleep 601s # intentional-sleep: wait for MCP rate limit reset',
+      ),
+    ).toBe('standalone sleep 601s');
+  });
+
+  it('does not allow intentional sleep comments on leading sleep chains', () => {
+    expect(
+      detectBlockedSleepPattern(
+        'sleep 5 && echo ok # intentional-sleep: wait for rate limit reset',
+      ),
+    ).toBe('sleep 5 followed by: echo ok');
+  });
+
+  it('does not allow intentional sleep comments to hide newline commands', () => {
+    expect(
+      detectBlockedSleepPattern(
+        'sleep 5 # intentional-sleep: wait for rate limit reset\necho ok',
+      ),
+    ).toBe('sleep 5 followed by: echo ok');
+  });
+
+  it('preserves commands after a shell comment newline', () => {
+    expect(detectBlockedSleepPattern('sleep 5 # wait\necho ok')).toBe(
+      'sleep 5 followed by: echo ok',
+    );
+  });
+
   it('does not treat in-quoted `#` as a comment', () => {
     // `#` inside single quotes is literal, so the suffix is not a comment
     // and the existing separator logic still rejects it.

packages/core/src/tools/shell.ts

@@ -1022,17 +1022,30 @@ export function buildLongRunningForegroundHint(elapsedMs: number): string {
 /**
  * Detect standalone or leading `sleep N` patterns that should use Monitor
  * instead. Catches `sleep 5`, `sleep 2.5`, `sleep 2s`,
- * `sleep 5 && check`, `sleep 5; check`, `sleep 5 # wait` — but not sleep
+ * `sleep 5 && check`, `sleep 5; check`, `sleep 5 # wait` -- but not sleep
  * inside pipelines, subshells, backgrounded commands, or scripts (those are
  * fine).
  */
 export function detectBlockedSleepPattern(command: string): string | null {
+  return detectBlockedSleepPatternDetails(command)?.description ?? null;
+}
+
+type BlockedSleepPatternDetails = {
+  description: string;
+  intentionalSleepRejection?: string;
+};
+
+function detectBlockedSleepPatternDetails(
+  command: string,
+): BlockedSleepPatternDetails | null {
   // Strip trailing shell comments first; otherwise `sleep 5 # wait` would
   // present `# wait` as the suffix, which `getSleepSequentialSeparator`
   // rejects (only &&/||/;/\n are recognized), letting the foreground sleep
   // bypass the guard. Shell ignores top-level trailing comments, so for the
   // purposes of detection they are equivalent to end-of-command.
-  const trimmed = trimTrailingShellComment(command).trim();
+  const { command: uncommentedCommand, comment } =
+    splitTrailingShellComment(command);
+  const trimmed = uncommentedCommand.trim();
   if (!trimmed.startsWith('sleep')) return null;
   const afterSleep = trimmed.slice('sleep'.length);
   if (!afterSleep || !/\s/.test(afterSleep[0]!)) return null;
@@ -1059,9 +1072,53 @@ export function detectBlockedSleepPattern(command: string): string | null {
   if (separator === null) return null;
 
   const rest = separator.rest.trim();
-  return rest
+  const description = rest
     ? `sleep ${durationToken} followed by: ${rest}`
     : `standalone sleep ${durationToken}`;
+  if (!rest && hasIntentionalSleepCommentPrefix(comment)) {
+    const reason = getIntentionalSleepReason(comment);
+    if (reason === null) {
+      return {
+        description,
+        intentionalSleepRejection:
+          'The intentional-sleep comment was recognized, but the reason is too short; explain why the delay is needed after `intentional-sleep:`.',
+      };
+    }
+    if (secs > MAX_INTENTIONAL_SLEEP_SECONDS) {
+      return {
+        description,
+        intentionalSleepRejection:
+          'The intentional-sleep comment was recognized, but foreground sleeps over 10 minutes are not allowed; use is_background: true or Monitor for longer waits.',
+      };
+    }
+    debugLogger.debug('intentional sleep allowed', {
+      durationSeconds: secs,
+      reason,
+    });
+    return null;
+  }
+  return { description };
+}
+
+const INTENTIONAL_SLEEP_COMMENT_PREFIX = 'intentional-sleep:';
+const MAX_INTENTIONAL_SLEEP_SECONDS = 10 * 60;
+// Require a real reason, not a trivial opt-out like "wait".
+const MIN_INTENTIONAL_SLEEP_REASON_LENGTH = 8;
+
+function hasIntentionalSleepCommentPrefix(comment: string | null): boolean {
+  if (comment === null) return false;
+
+  return comment.trim().startsWith(INTENTIONAL_SLEEP_COMMENT_PREFIX);
+}
+
+function getIntentionalSleepReason(comment: string | null): string | null {
+  if (comment === null) return null;
+
+  const trimmed = comment.trim();
+  if (!trimmed.startsWith(INTENTIONAL_SLEEP_COMMENT_PREFIX)) return null;
+
+  const reason = trimmed.slice(INTENTIONAL_SLEEP_COMMENT_PREFIX.length).trim();
+  return reason.length >= MIN_INTENTIONAL_SLEEP_REASON_LENGTH ? reason : null;
 }
 
 function parseSleepDurationToSeconds(token: string): number | null {
@@ -1130,7 +1187,10 @@ function getSleepSequentialSeparator(suffix: string): { rest: string } | null {
   return null;
 }
 
-function trimTrailingShellComment(command: string): string {
+function splitTrailingShellComment(command: string): {
+  command: string;
+  comment: string | null;
+} {
   let inSingleQuote = false;
   let inDoubleQuote = false;
   let inBacktick = false;
@@ -1216,11 +1276,25 @@ function trimTrailingShellComment(command: string): string {
       commandSubstitutionDepth === 0 &&
       (i === 0 || /\s/.test(command[i - 1]!))
     ) {
-      return command.slice(0, i);
+      const newlineIndex = command.indexOf('\n', i + 1);
+      return {
+        command:
+          newlineIndex === -1
+            ? command.slice(0, i)
+            : command.slice(0, i) + command.slice(newlineIndex),
+        comment:
+          newlineIndex === -1
+            ? command.slice(i + 1)
+            : command.slice(i + 1, newlineIndex),
+      };
     }
   }
 
-  return command;
+  return { command, comment: null };
+}
+
+function trimTrailingShellComment(command: string): string {
+  return splitTrailingShellComment(command).command;
 }
 
 function hasTopLevelTrailingBackgroundOperator(command: string): boolean {
@@ -4285,15 +4359,19 @@ export class ShellTool extends BaseDeclarativeTool<
     // `-c` script. This matches every other sensitive check in this file
     // (directory, read-only, command-root extraction, etc.).
     if (!params.is_background) {
-      const sleepPattern = detectBlockedSleepPattern(
+      const sleepPattern = detectBlockedSleepPatternDetails(
         stripShellWrapper(params.command),
       );
       if (sleepPattern !== null) {
+        const intentionalSleepGuidance =
+          sleepPattern.intentionalSleepRejection ??
+          'If you genuinely need a standalone delay (rate limiting, deliberate pacing), ' +
+            'add a trailing comment like `# intentional-sleep: wait for MCP rate limit reset` (up to 10 minutes).';
         return (
-          `Blocked: ${sleepPattern}. ` +
+          `Blocked: ${sleepPattern.description}. ` +
           'Run blocking commands in the background with is_background: true. ' +
           'For streaming events (watching logs, polling APIs), use the Monitor tool. ' +
-          'If you genuinely need a delay (rate limiting, deliberate pacing), keep it under 2 seconds.'
+          intentionalSleepGuidance
         );
       }
     }