fix(openai): import Union so litellm is importable again

[Classic298]

TLDR

Problem this solves:

• import litellm raises NameError on Python 3.10 to 3.13
• Union is used in an annotation but never imported
• ruff check litellm reports it as F821

How it solves it:

• add Union to the existing typing import

Relevant issues

Linear ticket

Pre-Submission checklist

• I have added meaningful tests
• My PR passes all CI/CD checks (e.g., lint, format, unit tests)
• My PR's scope is as isolated as possible; it only solves 1 specific problem
• I have received a Greptile Confidence Score of at least 4/5 before requesting a maintainer review

No test added on purpose: any test that imports litellm is the regression test, and there are thousands of them. The gap is that something is letting a red ruff check litellm through, since F821 already names this exact line

Screenshots / Proof of Fix

owns_wrapped_http_client, added in #35492, annotates its parameter Optional[Union[httpx.Client, httpx.AsyncClient]]. The annotation is evaluated when the class body runs, so the missing name is not a typing nit, it kills the import outright on every version that evaluates annotations eagerly

Before, on litellm_internal_staging at 9d5984b:

python -c "import litellm"

  File "litellm/llms/openai/common_utils.py", line 138, in BaseOpenAILLM
    def owns_wrapped_http_client(http_client: Optional[Union[httpx.Client, httpx.AsyncClient]]) -> bool:
                                                       ^^^^^
NameError: name 'Union' is not defined

ruff check litellm

F821 Undefined name `Union`
   --> litellm/llms/openai/common_utils.py:138:56
Found 1 error.

After, same commands on this branch: ruff check litellm prints All checks passed!, import litellm succeeds, and a completion round trips

Type

🐛 Bug Fix

Changes

Union joins the existing from typing import (...) block in litellm/llms/openai/common_utils.py

Final Attestation

• The tests check the right things, including the edge cases, and regressions in the respective real-world customer use-cases are not possible after this PR

[Classic298]

Relates to : #35709 #35703

[greptile-apps]

Greptile Summary

This PR restores LiteLLM imports by adding the missing typing.Union import used by an eagerly evaluated OpenAI adapter annotation

• Adds Union to the existing typing import list in common_utils.py
• Resolves the import-time NameError and Ruff F821 violation

Confidence Score: 5/5

The PR appears safe to merge because it supplies the missing standard-library typing symbol without changing runtime behavior beyond restoring module importability

The isolated import addition resolves the existing annotation lookup failure and introduces no new execution, state, dependency, or security behavior

Important Files Changed

Filename	Overview
litellm/llms/openai/common_utils.py	Adds the missing Union typing import required by an existing annotation; no issues identified

_{Reviews (1): Last reviewed commit: "fix(openai): import Union so litellm is ..." | Re-trigger Greptile}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing Classic298:fix_missing_union_import (a62d6c0) with litellm_internal_staging (a6d4654)¹}

Footnotes

1. No successful run was found on litellm_internal_staging (32eb072) during the generation of this report, so a6d4654 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩