v1.5.7

What's Changed

Other Changes

• fix: preflight model reachability (#546) + enforce typed response_schema (#547) by @claude-dataviking in #548
• v1.5.7: synthesis provider routing (#549) + fail-loud on empty attachments (#550) + release bump by @claude-dataviking in #551

Full Changelog: v1.5.6...v1.5.7