A hook that cannot run its program now reports a plain explanation

A hook is a command you set up to run automatically at certain moments while Claude Code works. Every command ends with an exit code, a number that reports how it went. A shell uses 126 and 127 when it could not run a program, for example because the program is missing.

When a hook exits with 126 or 127, Claude Code now replaces the hook's error output with a message saying the exit code is a shell's code for a program it could not run and that the hook's error output is left out. This applies only when the hook carries a command label. Before, the hook's output and error output were passed on unchanged.