[fix] extra_headers in messages api bedrock invoke

[colinlin-stripe]

extra_headers in messages api bedrock invoke

Relevant issues

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Type

🐛 Bug Fix
✅ Test

Changes

Extra_headers from litellm config were not being propagated for messages api -> bedrock invoke
the are present in the kwargs but are not being extracted.

motivation is to pass anthropic beta headers to bedrock see docs

Testing

ran poetry run pytest tests/test_litellm/llms/custom_httpx/test_llm_http_handler.py -v

example litellm_config.yaml

- model_name: claude-sonnet-4.5-1m
    litellm_params:
      model: bedrock/us.anthropic.claude-sonnet-4-5-20250929-v1:0
      extra_headers:
        anthropic-beta: "context-1m-2025-08-07"

example curl

curl -v http://localhost:4000/v1/messages \
  -H 'Authorization: Bearer sk-master' \
  -H 'Content-Type: application/json' \
  -d '{"model": "claude-sonnet-4-5-1m", "max_tokens": 10, "messages": [{"role": "user", "content": "200k+ tokens of content"}]}' \

if request succeeds then anthropic beta header was propagated successfully

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