[BUG] Session keeps sending "waiting for task" messages autonomously, consuming tokens

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

After completing a task, the Claude Code session continues sending unprompted
messages autonomously ("Waiting for a task.", "Paused — won't continue without
a specific task.", etc.) roughly every few minutes — without any user input.

This happened while I was asleep with the session left open. The session consumed
~40% of the context window token budget sending ~15+ identical "waiting" messages.

Actual messages from session log:

Waiting for a task. Waiting for a task — won't continue without one. Paused. Waiting for your instructions. Waiting for a task.

(repeated ~15 times over several hours)

What Should Happen?

After completing a task and sending a final summary, Claude should go completely
silent and wait without sending any additional messages until the user writes something.

Error Messages/Logs

No error messages. The session silently consumed ~40% of context window tokens 
with zero useful work while the user was away.

Steps to Reproduce

1. Open Claude Code (web or desktop app on macOS)
2. Complete a multi-step coding task
3. Claude sends final summary: "Done, waiting for next task"
4. Leave the session open without interacting (computer may enter sleep mode)
5. Return after several hours — observe that Claude sent 10-15+ unprompted

"waiting for task" messages with no user input

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

unknown

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Claude Code desktop app + Claude Code web (claude.ai/code)

Reproduced on two separate platforms:

• Claude Code web (claude.ai/code) — browser tab left open
• Claude Code desktop app (Mac mini M4, macOS) — app left open

This suggests the issue is in the core session loop, not platform-specific.

Impact: significant token waste, session becomes unusable when context fills up,
happens silently while user is away with no way to prevent it without manually
closing every session after each task.