# Schema compatibility
The `0.1.18` reliability contract is additive. Existing action names and
legacy result fields remain available; new fields use camelCase at the CLI JSON
and MCP boundaries while Rust field names remain idiomatic.
Compatibility rules:
- `expectedRevision` is optional on every supported mutation. Omitting it keeps
the unguarded compatibility path.
- `executionId` is present on successful action outcomes and bounded traces.
- `verify` accepts only documented finite predicate forms and bounded
deadlines.
- Batch `mode` defaults to `unguarded`; `fixed` and `chain` require an
explicit initial `expectedRevision`.
- Unknown fields are ignored where the existing parser is permissive; unknown
action names, invalid types, and unbounded values are rejected.
The Rust library, CLI, MCP server, TypeScript client, and Python client use the
same argument names and result vocabulary. Removing or renaming a published
field requires a major contract decision rather than a patch release.