BerriAI/litellm · error · BedrockError

Error converting to valid response block=

Error message

Error converting to valid response block={e}. File an issue if litellm error - https://github.com/BerriAI/litellm/issues

What it means

After a successful HTTP 200, the Bedrock Converse response JSON is validated into the typed ConverseResponseBlock model. Any mismatch — missing required fields, wrong types, or new AWS fields the installed LiteLLM schema does not know — raises BedrockError 422 with a message asking you to file an issue. The network call succeeded; this is a schema mismatch between AWS output and LiteLLM's response model.

Solutions

1. Upgrade LiteLLM to the latest release — response-block models are updated in patch releases as Bedrock adds fields
2. Capture response.text with a post-call logging hook to identify the offending field
3. If it persists on the latest version, file the issue at https://github.com/BerriAI/litellm/issues with the redacted payload
4. As a stopgap, pin calls to a Bedrock region/model combination that still returns the older schema

try:
    resp = litellm.completion(model="bedrock/...", messages=msgs)
except BedrockError as e:
    if e.status_code == 422 and "Error converting to valid response block" in str(e):
        logger.error("Bedrock schema drift — update litellm; payload: %s", captured_response_text)
        raise DependencyOutdated("pip install -U litellm") from e
    raise

When it happens

Trigger: AWS ships a response containing fields, enum values, or block types absent from your LiteLLM version's ConverseResponseBlock; an error body reaching the success parser; a response mutated by a proxy or cross-region inference endpoint with a nonstandard envelope.

Common situations: Running an older LiteLLM against a newly updated Bedrock API; beta features (guardrail traces, performance configs, new tool result shapes) returning extra fields; the morning after an AWS rollout with a pinned litellm version.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• BedrockException
• {err.response.text}
• Error processing response
• messages must be a list
• messages parameter is required for Converse input

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/87371b3940e26f33. Report an issue: GitHub.

Appendix: source

Thrown at litellm/llms/bedrock/chat/converse_transformation.py:2157

        data: dict | str,
        messages: list,
        encoding,
    ) -> ModelResponse:
        ## LOGGING
        if logging_obj is not None:
            logging_obj.post_call(
                input=messages,
                api_key=api_key,
                original_response=response.text,
                additional_args={"complete_input_dict": data},
            )

        json_mode: Final[bool | None] = optional_params.get("json_mode", None)
        ## RESPONSE OBJECT
        try:
            completion_response: Final = ConverseResponseBlock(**response.json())
        except Exception as e:
            raise BedrockError(
                message=f"Error converting to valid response block={e}. File an issue if litellm error - https://github.com/BerriAI/litellm/issues",
                status_code=422,
            )

        """
        Bedrock Response Object has optional message block

        completion_response["output"].get("message", None)

        A message block looks like this (Example 1):
        "output": {
            "message": {
                "role": "assistant",
                "content": [
                    {
                        "text": "Is there anything else you'd like to talk about? Perhaps I can help with some economic questions or provide some information about economic concepts?"
                    }
                ]

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