Python: Add OpenAI types to default checkpoint encoding allow list

[Tao Chen (TaoChenOSU)]

Motivation and Context

When a workflow using OpenAI services get checkpointed, the file-based checkpoint storage raises the following warning:

Failed to decode pickled checkpoint data: Checkpoint deserialization blocked for type 'openai.types.responses.response_output_text:ResponseOutputText'. To allow this type, either include its 'module:qualname' key in the 'allowed_types' set passed to 'decode_checkpoint_value', or add it to 'allowed_checkpoint_types' on your checkpoint storage (for example, 'FileCheckpointStorage.allowed_checkpoint_types').

Description

Common types should be automatically included. This PR adds OpenAI types.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Evan Mattson (moonbox3)]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/_workflows
_checkpoint.py	158	1	99%	299
_checkpoint_encoding.py	64	0	100%
TOTAL	27671	3200	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
5597	20 💤	0 ❌	0 🔥	1m 28s ⏱️

[Copilot]

Pull request overview

Adds OpenAI SDK model types to the “always allowed” set for restricted checkpoint deserialization, so workflows using OpenAI objects can be checkpointed/restored without requiring users to manually extend allowed_checkpoint_types.

Changes:

• Expands restricted unpickling allow-list to include OpenAI SDK modules by prefix match.
• Updates FileCheckpointStorage docs to mention OpenAI SDK types are allowed by default.
• Adds tests asserting OpenAI Chat Completions and Responses usage types can round-trip through restricted checkpoint encoding.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
python/packages/core/agent_framework/_workflows/_checkpoint_encoding.py	Adds OpenAI module-prefix allowance to restricted unpickling logic.
python/packages/core/agent_framework/_workflows/_checkpoint.py	Updates FileCheckpointStorage docstring to describe OpenAI types as implicitly allowed.
python/packages/core/tests/workflow/test_checkpoint_unrestricted_pickle.py	Adds regression tests validating restricted decode accepts OpenAI SDK type instances.