test(bedrock): restore invoke stream chunk coverage

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

@@ -2,15 +2,45 @@ 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)
+
+
 def test_transform_request_drops_internal_params():
     """LiteLLM-internal MCP params (e.g. skip_mcp_handler) are control flags used
     inside LiteLLM and are not valid Bedrock inference parameters. Leaking them