TUI stays alive with EOF stdin and no TTY

Reproduction

docker run -d --name opencode-eof node:22-bookworm-slim sleep infinity
docker exec opencode-eof npm install -g opencode-ai@1.18.18
timeout -s KILL 8s docker exec opencode-eof opencode </dev/null
docker top opencode-eof -eo pid,ppid,tty,stat,etime,args

Actual

opencode does not exit. After the docker exec client is killed, the TUI process remains in the container with no TTY.

Expected

Exit with a clear error when the TUI has EOF stdin and no prompt. Otherwise the process can hold an active exec session indefinitely and prevent auto-sleep for idle environments.