[Ran Shemtov (ranst91)]

Motivation & Context

This change addresses three persistence gaps in the Python AG-UI adapter:

• When incoming history omits or changes an earlier message, reconciliation can append later user messages whose IDs already exist in the saved snapshot.
• A provider failure before the first snapshot checkpoint can leave submitted user input unsaved.
• Converting multimodal input into snapshot binary parts drops attachment filenames.

Our original duplication case was triggered by a CopilotKit wrapper that removed historical tool messages. We fixed that wrapper separately. The reconciliation change here provides additional protection when incoming history differs from saved history.

Description & Review Guide

• Exclude already-stored message IDs from the incoming history suffix, preserving authoritative saved content and order.
• Checkpoint input before provider execution for configured stateless snapshot sessions. Preserve the existing behavior for provider-managed sessions.
• Retain filenames during binary-part normalization.

Existing duplicated snapshots are not rewritten. Unfinished assistant output is not committed by the input checkpoint.

Please review the checkpoint boundary, approval continuation behavior, and preservation of message identity and attachment metadata.

Validation

At commit bf82841e7:

• AG-UI test suite: 1,787 passed, with existing dependency/deprecation warnings.
• Changed source passed Pyright, Ruff, and formatting checks.
• Real-provider checks verified input preservation after rejection and tool-result persistence through cold snapshot hydration.

These checks used a custom JSON snapshot store. They do not establish coverage for every storage implementation or browser/Intelligence workflow.

Related Issue

This contribution was initiated by the AG-UI team. An agreed Microsoft issue has not yet been linked.

AI Assistance

Implementation, tests, investigation, and this description were AI-assisted. Human contributor review and responsibility acknowledgement remain pending.

[Copilot]

🟡 Changes recommended

Checkpoint persistence can lose recoverable input after session-ID rebinding and prematurely clear unresolved interrupt prompts, leaving hydration incomplete after a failure or disconnect.

2 open issues

• On an ordinary turn with an unresolved stored interrupt such as confirm_changes,… · New
• When threadId is omitted, this checkpoint uses a generated UUID, but the first provider update… · New

What changed in this PR

This PR strengthens persistence in the Python AG-UI adapter so failed runs retain submitted input and differing client history does not duplicate saved messages.

Changes:

• Filter already-stored message IDs from reconciled incoming history.
• Checkpoint input before provider execution for configured stateless snapshot sessions.
• Preserve attachment filenames during multimodal snapshot normalization and add regression coverage.

File	Description
python/​packages/​ag-ui/​tests/​ag_ui/​test_run.py	Expect submitted input to survive response invalidation.
python/​packages/​ag-ui/​tests/​ag_ui/​test_run_common.py	Test deduplication when client history differs from saved history.
python/​packages/​ag-ui/​tests/​ag_ui/​test_message_adapters.py	Test filename preservation across normalization.
python/​packages/​ag-ui/​tests/​ag_ui/​test_endpoint.py	Cover failed-run persistence, cancellation, media, and approval-history replay.
python/​packages/​ag-ui/​agent_framework_ag_ui/​_run_common.py	Exclude stored IDs from incoming history suffixes.
python/​packages/​ag-ui/​agent_framework_ag_ui/​_message_adapters.py	Retain filenames in normalized binary parts.
python/​packages/​ag-ui/​agent_framework_ag_ui/​_agent_run.py	Add an input checkpoint before provider execution.

_{Review effort: Balanced}