Claude desktop app leaks PTY file descriptors (/dev/ptmx), exhausting macOS system limit and blocking new terminal windows

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?

The Claude desktop app (macOS) leaks PTY file descriptors by opening /dev/ptmx for each Bash tool call but never closing them. After extended use with many Bash tool invocations, the number of open PTY handles grows to 500+, exhausting the macOS system limit of 511 (kern.tty.ptmx_max).

Once the limit is hit, macOS Terminal.app can no longer open new windows and reports:

[forkpty: Device not configured]
[未能创建新的进程和打开伪终端(pseudo-tty)。]

Diagnosis via lsof /dev/ptmx | awk '{print $1}' | sort | uniq -c | sort -rn:

 505 Claude
   2 Electron
   1 Terminal

kern.tty.ptmx_max: 511 — 505 of 511 PTY slots consumed by the Claude process.

What Should Happen?

PTY file descriptors should be released when each Bash tool call completes. The Claude app should not accumulate hundreds of open /dev/ptmx handles across tool calls in a session.

Error Messages/Logs

macOS Terminal.app when trying to open a new window:

[forkpty: Device not configured]
[未能创建新的进程和打开伪终端(pseudo-tty)。]


`lsof /dev/ptmx` output (505 entries, all Claude PID 89280):

Claude   89280 yunasun   37u   CHR 15,291      0t0  605 /dev/ptmx
Claude   89280 yunasun  106u   CHR 15,387      0t0  605 /dev/ptmx
Claude   89280 yunasun  114u   CHR 15,383      0t0  605 /dev/ptmx
... (502 more identical lines)


`sysctl kern.tty.ptmx_max` → 511 (system limit)

Steps to Reproduce

1. Open the Claude desktop app
2. Start a conversation and run many Bash tool calls (e.g. run dozens of shell commands over an extended session)
3. Check PTY usage: lsof /dev/ptmx | awk '{print $1}' | sort | uniq -c
4. Observe Claude accumulating hundreds of /dev/ptmx file descriptors
5. Once count reaches ~508+, try to open a new macOS Terminal.app window
6. Terminal shows [forkpty: Device not configured] and fails to open

Workaround: Quit and restart the Claude desktop app — all leaked PTYs are released immediately.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.185 (Claude Code)

Claude Code Version

Claude 1.14271.0 (c8f4d8) 2026-06-18T05:47:57.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

• System: macOS Darwin 25.3.0
• Reproduced after one long session with many Bash tool calls
• The PTY count grows monotonically — never drops between tool calls
• Restarting Claude fully resolves the issue until PTYs accumulate again
• Other apps (Electron/VSCode) only hold 2 PTY handles under the same usage