Jshell

JShell

Run JShell in an agent-controlled terminal and own its lifecycle. Record its pid when it starts, keep the terminal session, and do not finish the task until that session has exited.

Resolve the executable

Run jshell --version before the first evaluation. On macOS, /usr/bin/jshell can be a launcher that reports no Java runtime even when an SDK-managed JDK is installed. In that case, resolve an installed JDK and use its absolute bin/jshell path for the rest of the task.

If a requested JShell option is uncertain, inspect that executable's --help or --help-extra.

Start and use JShell

Start this command in a terminal with TTY enabled, replacing the final argument with the resolved absolute path:

/bin/sh -c 'printf "JSHELL_PID=%s\n" "$$" >&2; exec "$1" --execution local --feedback concise' sh /absolute/path/to/jshell

Save both the returned terminal-session id and the printed JSHELL_PID. exec replaces the shell with JShell without changing the pid, while --execution local keeps evaluation in that tracked process.

Send Java snippets to the terminal session with a trailing newline. Poll a running session with an empty write. A returned live-session id only means the command is still running; it does not prove that JShell is waiting at a prompt.

Finish the session

Never send /exit. When no more evaluation is needed:

1. From a separate terminal command, send TERM to the recorded numeric pid. For example, if JShell printed JSHELL_PID=16438, run kill -TERM 16438.
2. Poll the original terminal session with empty writes for at most five seconds.
3. If it has not exited after those five seconds, confirm that the same pid is still the tracked JShell process, send KILL to that pid, and poll the original session again until it exits.

Never abandon a live JShell terminal session. Do not use pkill jshell or killall; terminate only the pid recorded for the current task.