Task .output files in /private/tmp grow unbounded (95GB+)

Description

Subagent task .output files in /private/tmp/claude-501/<project>/<session>/tasks/ can grow to tens of gigabytes without any size cap, filling up disk space silently.

Observed behavior

Found 95GB consumed by three .output files:

| Project | File | Size | Cause |
|---------|------|------|-------|
| Headband | bpnv8d8um.output | 46.1 GB | Subagent output aggregation — all child agent JSON messages concatenated into one file |
| AnnasTeech | bx09ukqis.output | 43.5 GB | Same — unbounded agent output aggregation |
| time-guy | b95uphkyk.output | 5.0 GB | sentry-cli login interactive prompt looped infinitely printing invalid input! |

All other .output files in the same directories were normal size (10KB–100KB).

Expected behavior

Task output files should have a size cap (e.g., 50MB or 100MB) to prevent unbounded growth. When a cap is hit, either truncate with a warning or stop capturing.

Steps to reproduce

1. Run a Claude Code session with multiple subagents (e.g., 5+ parallel agents via worktrees)
2. One agent runs a command that produces infinite or very large output (interactive prompt in non-interactive shell, verbose build loop, etc.)
3. The corresponding .output file in /private/tmp/claude-501/ grows without limit

Environment

• macOS (Darwin 25.3.0)
• Claude Code with heavy subagent usage (product-review, product-sprint workflows with parallel agents)
• Files located at: /private/tmp/claude-501/<project-path>/<session-uuid>/tasks/<task-id>.output

Workaround

rm -rf /private/tmp/claude-501 — these are ephemeral task output captures and safe to delete. Directory is also cleared on reboot.