litellm/litellm/passthrough
milan-berri f45909cb81
fix(proxy): Bedrock Knowledge Base pass-through: preserve SigV4 headers and signed request body (#27526)
* Fix Bedrock KB pass-through SigV4 headers and signed body

Coerce botocore HeadersDict to a dict for pass-through routes. When
forward_headers is true, drop request headers that collide case-insensitively
with signed headers so client Bearer auth does not shadow AWS SigV4.
Send prepped.body as raw content so the outbound payload matches the
signature after logging hooks mutate the parsed dict.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Simplify pass-through raw body handling

Read the SigV4-signed bytes directly from request.state inside
pass_through_request instead of threading a custom_raw_body argument
through three functions. Helper methods are restored to their original
signatures, and the new branch lives in one place at each httpx call site.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Harden pass-through raw body read from request.state

Guard missing request.state (test fixtures) and ignore non-bytes/str
values so MagicMock does not trigger the SigV4 raw-body path.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Test pass_through_request state_raw_body uses httpx content=

Cover non-streaming (async_client.request) and streaming (build_request)
paths so SigV4 bytes on request.state are not replaced by json= of a
hook-mutated dict.

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: Cursor <cursoragent@cursor.com>
2026-05-25 19:21:55 +05:30
..
__init__.py build(VLLM-Passthrough-with-loadbalancing-support-(enables-using-model-list-for-VLLM-/classify-endpoint)): Closes #11205 2025-05-31 09:00:04 -07:00
main.py fix(passthrough): log when streaming spend-tracking flush fails to schedule 2026-04-30 02:39:29 +00:00
README.md build(VLLM-Passthrough-with-loadbalancing-support-(enables-using-model-list-for-VLLM-/classify-endpoint)): Closes #11205 2025-05-31 09:00:04 -07:00
utils.py fix(proxy): Bedrock Knowledge Base pass-through: preserve SigV4 headers and signed request body (#27526) 2026-05-25 19:21:55 +05:30

This makes it easier to pass through requests to the LLM APIs.

E.g. Route to VLLM's /classify endpoint:

SDK (Basic)

import litellm


response = litellm.llm_passthrough_route(
    model="hosted_vllm/papluca/xlm-roberta-base-language-detection",
    method="POST",
    endpoint="classify",
    api_base="http://localhost:8090",
    api_key=None,
    json={
        "model": "swapped-for-litellm-model",
        "input": "Hello, world!",
    }
)

print(response)

SDK (Router)

import asyncio
from litellm import Router

router = Router(
    model_list=[
        {
            "model_name": "roberta-base-language-detection",
            "litellm_params": {
                "model": "hosted_vllm/papluca/xlm-roberta-base-language-detection",
                "api_base": "http://localhost:8090", 
            }
        }
    ]
)

request_data = {
    "model": "roberta-base-language-detection",
    "method": "POST",
    "endpoint": "classify",
    "api_base": "http://localhost:8090",
    "api_key": None,
    "json": {
        "model": "roberta-base-language-detection",
        "input": "Hello, world!",
    }
}

async def main():
    response = await router.allm_passthrough_route(**request_data)
    print(response)

if __name__ == "__main__":
    asyncio.run(main())

PROXY

  1. Setup config.yaml
model_list:
  - model_name: roberta-base-language-detection
    litellm_params:
      model: hosted_vllm/papluca/xlm-roberta-base-language-detection
      api_base: http://localhost:8090
  1. Run the proxy
litellm proxy --config config.yaml

# RUNNING on http://localhost:4000
  1. Use the proxy
curl -X POST http://localhost:4000/vllm/classify \
-H "Content-Type: application/json" \
-H "Authorization: Bearer <your-api-key>" \
-d '{"model": "roberta-base-language-detection", "input": "Hello, world!"}' \

How to add a provider for passthrough

See VLLMModelInfo for an example.

  1. Inherit from BaseModelInfo
from litellm.llms.base_llm.base_utils import BaseLLMModelInfo

class VLLMModelInfo(BaseLLMModelInfo):
    pass
  1. Register the provider in the ProviderConfigManager.get_provider_model_info
from litellm.utils import ProviderConfigManager
from litellm.types.utils import LlmProviders

provider_config = ProviderConfigManager.get_provider_model_info(
    model="my-test-model", provider=LlmProviders.VLLM
)

print(provider_config)