claude -w <name> --tmux parent process does not exit after the spawned tmux Claude session ends

What happened

Launching Claude in a worktree with a tmux session via:

claude -w refactor --tmux

correctly blocks the launching shell while the new Claude session runs in the
new tmux session. However, after I exit the inner Claude session, the original
claude command in the launching terminal does not exit. It hangs until I
manually interrupt it with Ctrl-C.

Expected behavior

When the spawned tmux Claude session exits, the parent claude -w … --tmux
command should detect the child's termination and exit cleanly on its own,
returning control to the launching shell — without requiring a manual Ctrl-C.

Actual behavior

The parent command remains blocked after the child session ends. Pressing
Ctrl-C in the launching terminal unblocks it and returns to the shell prompt,
but it never exits on its own.

Reproduction

Reproduced in a brand new, empty git repo. The flags -w + --tmux alone are
sufficient — no --permission-mode needed.

1. Create and enter a fresh git repo:

mkdir repro && cd repro && git init && git commit --allow-empty -m init

1. Run:

claude -w repro --tmux

1. Wait for the new tmux session/Claude session to start.
2. Exit the inner Claude session (e.g. /exit or Ctrl-C twice).
3. Observe: the original terminal's claude command is still blocked and does

not return to the shell prompt until you press Ctrl-C.

Environment

• Claude Code: 2.1.156
• tmux: 3.6b
• OS: Linux WSL2 (6.6.87.2-microsoft-standard-WSL2, x86_64)
• Shell: zsh (/home/linuxbrew/.linuxbrew/bin/zsh)
• TERM: tmux-256color

Notes

• Possibly related to process-lifecycle/SIGCHLD handling issues such as #52544

(parent not reacting to child exit) and #62659 (orphaned child processes),
though neither is tmux+worktree specific.

• The CLI reference does not document the expected exit/cleanup behavior for

--tmux sessions, so this may be an unspecified edge case.

Workaround

Press Ctrl-C in the launching terminal after exiting the inner session to
unblock the parent command.