send-keys race condition: command sent before shell finishes initializing

[andrew-t-james-wc]

Bug Description

When dmux creates a new tmux session, it immediately sends the startup command via tmux send-keys without waiting for the shell in the pane to finish initializing. If the user has a heavy shell init (e.g., antigen, mise, starship, zoxide, atuin, direnv), the send-keys command fires before the shell is ready, causing the PATH='...' '/path/to/dmux' command to be echoed as raw text into the terminal instead of being executed.

The result is that dmux appears to silently fail — the user just sees the PATH string dumped to the terminal with no dmux TUI.

Steps to Reproduce

1. Have a shell with heavy initialization (e.g., zsh with antigen, mise, starship, zoxide, atuin, direnv)
2. Run dmux — it creates a new tmux session and immediately sends keys
3. Observe that the PATH='...' command string is printed as raw text rather than executed

Relevant Code Path

In dist/index.js:

• Line 232: execSync('tmux new-session -d -s ${sessionName}', { stdio: 'inherit' }) — creates the session
• Line 248: sendTmuxShellCommand(this.sessionName, dmuxCommand, 'inherit') — fires immediately after with no wait for shell readiness

sendTmuxShellCommand simply calls spawnSync('tmux', ['send-keys', '-t', target, command, 'Enter'], { stdio }).

The command sent is built by buildDmuxCommand in dist/utils/dmuxCommand.js and looks like PATH='...' '/path/to/dmux'.

There is no mechanism between session creation and send-keys to verify the shell has finished initializing and is ready to accept input.

Suggested Fix

A few possible approaches:

1. Poll for shell readiness — after tmux new-session, poll the pane (e.g., check for a prompt character via tmux capture-pane) before sending keys
2. Use tmux wait-for — have the shell signal readiness via tmux wait-for -S at the end of init, and wait on it before sending keys
3. Use tmux respawn-pane -k — instead of send-keys, use respawn-pane with the command directly, which replaces the shell process entirely and avoids the race
4. Use tmux set-option remain-on-exit + respawn-pane — start the pane with the dmux command directly rather than starting a shell and then injecting a command into it

Option 3 (respawn-pane) is likely the simplest and most robust, as it sidesteps the race entirely by not relying on shell readiness at all.