[BUG] Background task .output file grew to 1.4TB filling entire disk

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?

A background Bash task in Claude Code wrote an unbounded .output file that grew to 1.4TB overnight, consuming nearly
all available disk space on a 2TB drive (went from 1.5TB free to 15GB free).

Description:

A background Bash task in Claude Code wrote an unbounded .output file that grew to 1.4TB overnight, consuming nearly
all available disk space on a 2TB drive (went from 1.5TB free to 15GB free).

What happened:

A previous Claude Code session ran a background command (likely a dev server) in the project project-project-fe. The
task output was captured to a .output file in /private/tmp/claude-501/ with no size cap. The process ran from March
15 to March 18 and the file grew to 1.4TB before I noticed.

File location:
/private/tmp/claude-501/-Users-userxx-Desktop-Work-xx-xx-fe/d718ea19-4a72-4943-89ec-fadb04f4e3d7/tasks
/bj5c1wjbo.output

File details:
-rw-r--r-- 1 userxx wheel 1.4T Mar 15 09:32 bj5c1wjbo.output

Environment:

• macOS Darwin 25.2.0 (Apple Silicon)
• 2TB APFS disk
• Claude Code with Opus 4.6

Actual behavior:

No size limit exists on .output files. Long-running background tasks (dev servers, watch commands, etc.) that produce
continuous stdout output can fill the entire disk unnoticed.

Suggested fix:

• Add a max file size limit for task output files
• Truncate or rotate output when the limit is reached
• Optionally warn the user when a background task's output exceeds a threshold
• Auto-cleanup stale task output files from previous sessions

What Should Happen?

Expected behavior:

Background task .output files should have a maximum size cap (e.g., 50-100MB) with rotation or truncation to prevent
filling the user's disk.

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code in a project that has a dev server (e.g., Next.js, Vite, etc.)
2. Ask Claude to run something like "start the dev server" or "run npm run dev" — or have Claude run any long-lived

command using run_in_background: true in the Bash tool

1. The command starts running in the background, with stdout/stderr piped to a .output file under

/private/tmp/claude-501/<project>/<session>/tasks/<task-id>.output

1. Close or leave the Claude Code session without stopping the background task
2. The process continues running indefinitely, writing output (e.g., HMR updates, request logs) to the .output file

with no size limit

1. Over hours/days, the file grows unbounded until disk is full

Key issue: There is no size cap, rotation, or auto-cleanup on background task .output files. The process also isn't
killed when the Claude Code session ends.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Version: 2.1.78

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_