Tty

I built a Claude Code permission gate that holds an HTTP response open until a Stream Deck key is pressed. Then I needed to inject a keystroke into Claude Code's own TTY so a key press could write `1\r` straight into Claude's stdin. Bun can hold HTTP open all day. Bun cannot reliably wrap a child PTY through `node-pty` and capture the parent shell's PID. So I split my daemon: HTTP and WebSocket stay on Bun, and a Node CommonJS subprocess owns the PTY that runs Claude. (Quick grounding before the story: a PTY — pseudo-terminal — is the kernel object every interactive shell talks to. It’s a pair of file descriptors, master and slave; the program reads/writes the slave end as if it were a real terminal, and anything you write to the master end looks to that program like a human typing. The TTY is the slave end seen from the child’s side. node-pty is Microsoft’s library that gives a JavaScript parent process a writable handle to the master. Bun is a JavaScript runtime — Node’s faster sibling — and Node CommonJS is plain old require()-based Node, no transpile step. The story below is about which runtime owns the PTY.)