Related Issues

• fixes #issue-number

Proposed Changes:

• Fixed the schema-aware serialization helper used for pipeline snapshots and Agent State (_serialize_value_with_schema) so it no longer silently passes unsupported objects through as if they were serialized. Values such as datetime, bytes, complex and arbitrary objects without a to_dict method were previously stored unchanged and mislabeled as strings, which broke JSON storage and round-tripping of snapshots. Unsupported values now raise a SerializationError, and the callers that build snapshots (pipeline breakpoints and State.to_dict) catch it to omit only the offending field while keeping the rest of the payload resumable.

• Added support for serializing and deserializing frozenset values in _serialize_value_with_schema. A frozenset now round-trips back to a frozenset instead of being dropped.

How did you test it?

Updated existing tests and added new ones.

Notes for the reviewer

cc @marc-mrt

Checklist

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• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
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• I have run pre-commit hooks and fixed any issue.