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Python: [Bug]: get_latest raises TypeError when a storage holds naive and timezone-aware checkpoint timestamps #9941
Description
Observed Behavior
WorkflowCheckpoint.timestamp is documented as an "ISO 8601 timestamp", and both 2026-01-01T00:00:00 and 2026-01-02T00:00:00+00:00 are. get_latest compares them with datetime.fromisoformat, so a storage holding one of each raises TypeError, on InMemoryCheckpointStorage and FileCheckpointStorage alike. The default timestamp is aware, so this takes a checkpoint whose timestamp was supplied, for example one written by another tool.
Expected Behavior
get_latest returns the newest checkpoint, for example reading a naive timestamp as UTC, or the save rejects a naive timestamp.
Steps to Reproduce
pip install agent-framework-core==1.23.0- Run the script below.
Minimal Reproduction
import asyncio
from agent_framework import InMemoryCheckpointStorage
from agent_framework._workflows._checkpoint import WorkflowCheckpoint
async def main():
storage = InMemoryCheckpointStorage()
for name, stamp in [("a", "2026-01-01T00:00:00"), ("b", "2026-01-02T00:00:00+00:00")]:
await storage.save(WorkflowCheckpoint(workflow_name="w", graph_signature_hash="h", checkpoint_id=name, timestamp=stamp))
print((await storage.get_latest(workflow_name="w")).checkpoint_id)
asyncio.run(main())Error Messages and Stack Traces
TypeError: can't compare offset-naive and offset-aware datetimes
Package Versions
agent-framework-core 1.23.0, and main at b7884ad.
Python Version
3.12
Operating System
Linux
Regression
Unknown
Additional Context
On main the comparison is in the max(datetime.fromisoformat(cp.timestamp) for cp in checkpoints) of _workflows/_checkpoint.py. The open #9902 changes how get_latest handles a decode failure; its diff adds no timezone handling.
Acknowledgements
- I searched existing issues and did not find a duplicate.
- I personally verified this behavior and the reproduction details are authentic.
- I will wait for explicit maintainer agreement before starting implementation of a non-trivial change.
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github-actions commentedon Nov 1, 2026
🤖 Automated triage reproduction notes (agent-authored — trust but verify)
Agent analysis
The bug reproduces in
python/packages/core/agent_framework/_workflows/_checkpoint.py::_select_latest_checkpointat line 217 when one workflow contains both naive and timezone-aware ISO 8601 checkpoint timestamps. Minimal repro: save checkpoints timestamped2026-01-01T00:00:00and2026-01-02T00:00:00+00:00to either core storage implementation, then callget_latest(workflow_name="w").python/packages/core/tests/workflow/test_checkpoint.py::test_get_latest_compares_naive_and_aware_timestamps1.23.01.24.0eavanvalkenburg commentedon Nov 2, 2026
/plan Resolve the confirmed mixed naive/aware checkpoint timestamp failure on current main before selecting the policy in #9944. Compare treating offset-naive ISO timestamps as UTC with rejecting them at a supported boundary; document compatibility for existing checkpoints and externally supplied timestamps. Preserve aware-offset ordering and existing lineage/tie-break semantics, and cover both InMemoryCheckpointStorage and FileCheckpointStorage, mixed/all-naive/all-aware values, equivalent instants, and invalid timestamp behavior. Coordinate with the existing #9944 implementation and the distinct #9902 decode-error work rather than creating a parallel fix. This is scoped planning, not implementation approval or a request to change assignments.