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fix(tmux): fix argument ordering that breaks spawned sessions #899

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fix(tmux): fix argument ordering that breaks spawned sessions #899

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32 changes: 26 additions & 6 deletions packages/happy-cli/src/utils/tmux.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -445,16 +445,33 @@ export class TmuxUtilities {
return this.executeCommand(fullCmd);
} else {
// Non-send-keys commands
const fullCmd = [...baseCmd, ...cmd];
// IMPORTANT: Insert -t target BEFORE positional arguments (e.g. shell-command).
// tmux follows POSIX-style parsing: once a non-option positional argument is
// encountered, all subsequent arguments are treated as positional — so flags
// like -t placed after the shell-command are passed INTO the shell command
// rather than being interpreted by tmux. This caused spawned processes to
// receive "-t <session>" as extra argv, leading to immediate exit.
const fullCmd = [...baseCmd, cmd[0]];

// Add target specification for commands that support it
// Add target specification for commands that support it (before remaining args)
if (cmd.length > 0 && COMMANDS_SUPPORTING_TARGET.has(cmd[0])) {
let target = targetSession;
if (window) target += `:${window}`;
if (window) {
target += `:${window}`;
} else if (cmd[0] === 'new-window') {
// For new-window, append ':' so tmux interprets the target as a
// session (auto-assigning the next window index) rather than as a
// window index. Without this, a purely numeric session name like "0"
// is mistaken for window index 0 and fails with "index in use".
target += ':';
}
if (pane) target += `.${pane}`;
fullCmd.push('-t', target);
}

// Now add the rest of the arguments (options and positional args like shell-command)
fullCmd.push(...cmd.slice(1));

return this.executeCommand(fullCmd);
}
}
Expand Down Expand Up @@ -824,13 +841,16 @@ export class TmuxUtilities {
logger.debug(`[TMUX] Setting ${Object.keys(env).length} environment variables in tmux window`);
}

// Add the command to run in the window (runs immediately when window is created)
createWindowArgs.push(fullCommand);

// Add -P flag to print the pane PID immediately
// IMPORTANT: -P and -F must come BEFORE the shell-command argument.
// tmux treats everything after the first positional arg as part of the
// shell command, so flags placed after it are passed to the shell, not tmux.
createWindowArgs.push('-P');
createWindowArgs.push('-F', '#{pane_pid}');

// Add the command to run in the window (must be last — it's a positional arg)
createWindowArgs.push(fullCommand);

// Create window with command and get PID immediately
const createResult = await this.executeTmuxCommand(createWindowArgs, sessionName);

Expand Down