`_parse_edit` reads `operation` straight from hand-edited YAML and then
does `if operation not in VALID_OPERATIONS`. `VALID_OPERATIONS` is a
frozenset, so that membership test hashes the value — and an unhashable
one raises:
operation={'insert_after': 'a'} -> TypeError: unhashable type: 'dict'
operation=['insert_after'] -> TypeError: unhashable type: 'list'
`validate_overlay_yaml`'s docstring promises "validation never raises",
and nothing upstream catches TypeError (layer_sources wraps only
YAMLError/OSError/UnicodeDecodeError; _commands catches only ValueError),
so the CLI dies with a raw traceback instead of reporting the error.
The trigger is an ordinary authoring mistake: nesting the recommended
shorthand form under the explicit key.
Every other field in the same function is isinstance-guarded first
(`anchor`, `step`, `step["id"]`); `operation` was the outlier. Check the
type first and return the message the function already uses for
`operation: None` / `operation: 7`.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Ali jawwad
3451a21277