Agent teams: teammate panes never start the agent (stay in idle shell)

Summary

With CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1, teammate panes are created but the
agent process never starts inside them. The pane sits at an idle shell prompt
while the lead agent waits for replies that never arrive.

Repro

1. CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1 claude
2. Ask the lead for a trivial task that triggers agent teams — e.g. "create an

agent team that writes a hello-world script in bash and another in python."

1. Attach to the swarm: tmux -L claude-swarm-<lead-pid> a.

Observed

Each pane is running zsh (per #{pane_current_command}) — no agent process
was launched. The intended … claude.exe --agent-id … spawn command is visible
on screen, but it was never delivered to the shell's input: pressing Enter at
the prompt is a no-op.

Re-running the same spawn command in the pane after shell init has finished
launches the agent correctly, so the command itself is fine — only the initial
delivery doesn't take.

Notes

• Shell is zsh 5.9 with powerlevel10k plus plugins, so interactive init takes

a few hundred ms.

• Does not reproduce with a faster shell: setting default-command "/bin/sh"

on the claude-swarm tmux socket makes panes start reliably.

Workaround

# in ~/.tmux.conf — scoped to the agent-teams tmux socket only
%if "#{m:*claude-swarm-*,#{socket_path}}"
  set -g default-command 'PATH="$HOME/.local/bin:$PATH" exec /bin/sh'
%endif

Environment

• Claude Code 2.1.143, macOS 26.3, tmux 3.6, zsh 5.9 (powerlevel10k + plugins)