fix(bedrock): stop stream_chunk_size leaking into invoke request bodies (#30240)

stream_chunk_size is a LiteLLM-internal knob for re-chunking the HTTP
response stream. The invoke transformations splat optional_params into the
provider request body without dropping it, and Bedrock rejects unknown
fields, so any bedrock/invoke request that sets the parameter fails with
ValidationException: stream_chunk_size: Extra inputs are not permitted.
Drop it in the invoke dispatcher (covers cohere, titan, mistral, meta,
ai21) and in the Claude messages-format request builder (the route used
for bedrock/invoke Anthropic models)

litellm/llms/bedrock/chat/invoke_transformations/anthropic_claude3_transformation.py

@@ -215,6 +215,7 @@ class AmazonAnthropicClaudeConfig(AmazonInvokeConfig, AnthropicConfig):
 
         anthropic_request.pop("model", None)
         anthropic_request.pop("stream", None)
+        anthropic_request.pop("stream_chunk_size", None)
         output_format = anthropic_request.pop("output_format", None)
         output_config_format = pop_bedrock_invoke_output_config_format(
             anthropic_request

litellm/llms/bedrock/chat/invoke_transformations/base_invoke_transformation.py

@@ -150,6 +150,7 @@ class AmazonInvokeConfig(BaseConfig, BaseAWSLLM):
     ) -> dict:
         ## SETUP ##
         stream = optional_params.pop("stream", None)
+        optional_params.pop("stream_chunk_size", None)
         custom_prompt_dict: dict = litellm_params.pop("custom_prompt_dict", None) or {}
         hf_model_name = litellm_params.get("hf_model_name", None)
 

tests/test_litellm/llms/bedrock/chat/invoke_transformations/test_base_invoke_transformation.py

@@ -0,0 +1,41 @@
+import json
+import os
+import sys
+
+import pytest
+
+sys.path.insert(
+    0, os.path.abspath("../../../../../..")
+)  # Adds the parent directory to the system path
+
+from litellm.llms.bedrock.chat.invoke_transformations.anthropic_claude3_transformation import (
+    AmazonAnthropicClaudeConfig,
+)
+from litellm.llms.bedrock.chat.invoke_transformations.base_invoke_transformation import (
+    AmazonInvokeConfig,
+)
+
+
+@pytest.mark.parametrize(
+    "config,model",
+    [
+        (AmazonInvokeConfig, "anthropic.claude-3-sonnet-20240229-v1:0"),
+        (AmazonInvokeConfig, "amazon.titan-text-express-v1"),
+        (AmazonInvokeConfig, "mistral.mistral-7b-instruct-v0:2"),
+        (AmazonAnthropicClaudeConfig, "anthropic.claude-sonnet-4-6"),
+    ],
+)
+def test_transform_request_drops_stream_chunk_size(config, model):
+    """stream_chunk_size is a LiteLLM-internal knob for re-chunking the HTTP
+    response stream. Leaking it into the provider request body makes Bedrock
+    reject the whole request: ValidationException 'stream_chunk_size: Extra
+    inputs are not permitted'."""
+    request_body = config().transform_request(
+        model=model,
+        messages=[{"role": "user", "content": "hi"}],
+        optional_params={"stream": True, "stream_chunk_size": 2048, "max_tokens": 10},
+        litellm_params={},
+        headers={},
+    )
+
+    assert "stream_chunk_size" not in json.dumps(request_body)