Semantic Kernel Bedrock Claude Error

[Alex-Wenner-FHR (Alex-Wenner-FHR)]

I am using the SKChatCompletionAdapter with various AWS Bedrock Claude models.

I intermittently see the following error:

botocore.errorfactory.ValidationException: An error occurred (ValidationException) when calling 
the Converse operation: The content field in the Message object at messages.5 is empty. Add a 
ContentBlock object to the content field and try again.

I am implementing this exactly as the docs show here just with bedrock.

It is not consistent but troublesome enough. I see what seems related issues, discussions related to this topic but can't find it verbatim. Seems like someone else surely has ran into this before. Please let me know any suggestions you have. Thanks!

[Alex-Wenner-FHR (Alex-Wenner-FHR)]

Eric Zhu (@ekzhu) any thoughts on this?

[Eric Zhu (ekzhu)]

I think we currently don't have a very good support for Bedrock via semantic kernel adapter... It doesn't help that I don't have AWS account. Would appreciate some help here.

[amardeepjaiman]

I am facing similar issues with SemanticKernelAdapter implementation for Bedrock models. and there are multiple issue not one. and all are intermittent, it seems not usable right now.

I have raised more issues here :
#6480
#6479

[Clara Israel Chocron (claraisrael)]

hi all - facing the same issue. has there been any updates? For reference langchain had also faced this issue and resolved it. See below the issue and the fix implemented.

langchain-ai/langchain-aws#403 (comment)
langchain-ai/langchainjs#6043

[Lucas Kim (kimnamu)]

Thanks for pasting the exact ValidationException text, and thanks to amardeepjaiman for the trace in #6479: its completion_tokens: 0, content: '' line right before the 400 is the key.

Two steps, and #6479 is the same failure. Claude on Converse sometimes returns content: []; the adapter stores that as an empty AssistantMessage (teammates get an empty UserMessage). On the next call it becomes a ChatMessageContent with no items and SK's Bedrock connector sends {"role": "assistant", "content": []}, which Converse rejects with this message.

Runs on autogen main @ 027ecf0, semantic-kernel 1.36.0 (SK main formats messages the same way), boto3 1.40, us-east-1, us.anthropic.claude-haiku-4-5-20251001-v1:0:

Step	Result
Raw converse: prefilled full answer / stopSequences hit on the first token / "output two newlines only"	content: [], outputTokens 3 / 1 / 3
AssistantAgent (no system message), turn 1 "output two newlines only"	TextMessage content='', completion_tokens=4
Same agent, turn 2 "Say hi."	ValidationException ... messages.1 is empty
RoundRobinGroupChat of two agents, same task	second agent fails with the same 400
create() on [user, AssistantMessage(""), user], stock adapter	request {"role": "assistant", "content": []}, same 400
Same, blank messages dropped before SK (below)	200, 'Hi!\n\nHi again!'

[main] turn1 TextMessage content='' usage=RequestUsage(prompt_tokens=20, completion_tokens=4)
[main] turn2 ValidationException: An error occurred (ValidationException) when calling the Converse operation: The content field in the Message object at messages.1 is empty. Add a ContentBlock object to the content field and try again.

Drop-in until the adapter has a guard:

from autogen_ext.models.semantic_kernel import SKChatCompletionAdapter


class BedrockSafeSKAdapter(SKChatCompletionAdapter):
    def _convert_to_chat_history(self, messages):
        # Converse rejects messages with no content blocks and blank text blocks.
        kept = [m for m in messages if not (isinstance(m.content, str) and not m.content.strip())]
        return super()._convert_to_chat_history(kept)

Where each step happens

Step	Code
content: [] reply becomes content == ""	bedrock_chat_completion.py _create_chat_message_content maps only text / image / toolUse blocks
"" reaches SK	_sk_chat_completion_adapter.py:305 add_user_message(msg.content), :336 add_assistant_message(msg.content)
Zero items	chat_message_content.py:171 appends a TextContent only if content:
"content": [] on the wire	bedrock/services/model_provider/utils.py _format_user_message (line 48), _format_assistant_message (line 82)
Whitespace-only text	raw converse with {"text": "\n\n"} gives ValidationException: ... text content blocks must contain non-whitespace text, hence .strip()

The same filter at the top of the loop at _sk_chat_completion_adapter.py:299 would cover create and create_stream for every SK connector; langchain-ai/langchainjs#6043 did the equivalent for Converse. If a small PR with a no-network test would be useful, I can open one. Dropping the turn leaves two consecutive user messages, which Claude 4.x accepted here; on a Claude 3 model with strict role alternation, merge the neighbouring texts instead. The empty reply is nondeterministic in normal use, hence the intermittent look; the first table row makes it reproducible.