fix: handle dict response in Responses API streaming and logging

[Ericcwang23]

Fixes #34754

Three code paths assumed response is a Pydantic object but some upstream providers return a plain dict, causing AttributeError: 'dict' object has no attribute 'usage'.

• router.py: add isinstance(completed.response, dict) guard before .usage access
• litellm_logging.py: add isinstance(result.response, dict) guard before .usage access
• transformation.py: add or [] fallback for None output_items

[greptile-apps]

Greptile Summary

This PR adds defensive handling for dictionary-backed Responses API streaming events and nullable output collections.

• Extracts usage from dictionary responses in the Router fallback path.
• Allows logging to assemble dictionary-backed completed responses.
• Treats absent response output collections as empty while transforming responses.

Confidence Score: 4/5

The PR appears safe to merge, with only a non-blocking return-type annotation mismatch in the logging helper.

The changed runtime paths safely avoid attribute access on dictionary responses and handle absent output collections; the remaining issue is that _get_assembled_streaming_response now returns a dictionary excluded by its annotation.

Files Needing Attention: litellm/litellm_core_utils/litellm_logging.py

Important Files Changed

Filename	Overview
litellm/completion_extras/litellm_responses_transformation/transformation.py	Safely skips nullable output collections in non-streaming and terminal streaming transformations without changing established empty-output behavior.
litellm/litellm_core_utils/litellm_logging.py	Adds runtime support for dictionary-backed completed responses, but the helper's return annotation no longer describes every returned type.
litellm/router.py	Defensively extracts nested usage from dictionary responses while preserving the existing typed response path.

_{Reviews (1): Last reviewed commit: "fix: handle dict response in Responses A..." | Re-trigger Greptile}

[greptile-apps]

Return annotation excludes dictionaries

This branch returns a plain dictionary even though _get_assembled_streaming_response declares only model response types or None, making the type contract inaccurate and preventing callers from correctly inferring dictionary handling requirements.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
litellm/litellm_core_utils/litellm_logging.py	0.00%	2 Missing ⚠️
litellm/router.py	0.00%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!

[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing Ericcwang23:fix-responses-v2 (97aa248) with main (0cd588a)}