[adityasingh2400]

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Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: BaseTool.from_config drops T | None arguments on Python 3.11-3.13 #7840

Problem:
BaseTool.from_config unwraps Optional[T] with if get_origin(param_type) is Union. Before Python 3.14, a PEP 604 optional (T | None) has origin types.UnionType, so the unwrap was skipped, no branch matched, and the argument was dropped with an "Unsupported parsing for argument" warning. Built-in tools that use the default from_config and annotate their arguments this way silently lost them from YAML configs. That includes VertexAiRagRetrieval (rag_corpora, similarity_top_k, …), GoogleSearchTool (model) and ExecuteBashTool (workspace).

Solution:
Treat types.UnionType like typing.Union when unwrapping the optional, so T | None maps exactly like Optional[T]. On Python 3.14, where the two are the same type, nothing changes.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Added to tests/unittests/tools/test_base_tool.py:

• test_from_config_unwraps_pep604_optional_args: int | None, list[str] | None and float | None arguments are passed through, and Optional[str] still works.
• test_vertex_ai_rag_retrieval_from_config_keeps_pep604_args: rag_corpora, similarity_top_k and vector_distance_threshold reach the tool's VertexRagStore.

# On main (before the fix, Python 3.11)
AssertionError: assert None == 5
AssertionError: assert None == ['projects/p/locations/us-central1/ragCorpora/123']

# With the fix
$ pytest tests/unittests/tools tests/unittests/agents
4389 passed, 1 xfailed

pre-commit run passes on the changed files, and mypy reports no issues in base_tool.py.

Manual End-to-End (E2E) Tests:

I loaded a YAML agent config through config_agent_utils.from_config. The config holds a VertexAiRagRetrieval tool with rag_corpora, similarity_top_k and vector_distance_threshold, and I inspected agent.tools[0].vertex_rag_store (Python 3.11):

=== BEFORE (main) ===
Unsupported parsing for argument: rag_corpora.
Unsupported parsing for argument: similarity_top_k.
Unsupported parsing for argument: vector_distance_threshold.
rag_corpora: None
similarity_top_k: None
vector_distance_threshold: None
=== AFTER (this PR) ===
rag_corpora: ['projects/p/locations/us-central1/ragCorpora/123']
similarity_top_k: 5
vector_distance_threshold: 0.4

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

Additional context

#4371 / #4406 dealt with PEP 604 unions in function-declaration parsing. This is the separate tool-config path.