BerriAI/litellm · error · ValueError

Invalid model format. Expected format: 'model=bedrock/agentc

Error message

Invalid model format. Expected format: 'model=bedrock/agentcore/arn:aws:bedrock-agentcore:region:account:runtime/runtime_id'

What it means

Error "Invalid model format. Expected format: 'model=bedrock/agentcore/arn:aws:bedrock-agentcore:region:account:runtime/runtime_id'" thrown in BerriAI/litellm.

Source

Thrown at litellm/llms/bedrock/chat/agentcore/transformation.py:163

            headers=headers,
            optional_params=optional_params,
            request_data=request_data,
            api_base=api_base,
            model=model,
            stream=stream,
            fake_stream=fake_stream,
            api_key=api_key,
        )

    def _get_agent_runtime_arn(self, model: str) -> str:
        """
        Extract ARN from model string
        model = "agentcore/arn:aws:bedrock-agentcore:us-west-2:888602223428:runtime/hosted_agent_r9jvp-3ySZuRHjLC"
        returns: "arn:aws:bedrock-agentcore:us-west-2:888602223428:runtime/hosted_agent_r9jvp-3ySZuRHjLC"
        """
        parts: Final = model.split("/", 1)
        if len(parts) != 2 or parts[0] != "agentcore":
            raise ValueError(
                "Invalid model format. Expected format: 'model=bedrock/agentcore/arn:aws:bedrock-agentcore:region:account:runtime/runtime_id'"
            )
        return parts[1]

    def _extract_region_from_arn(self, arn: str) -> str:
        """
        Extract region from ARN
        arn:aws:bedrock-agentcore:us-west-2:888602223428:runtime/hosted_agent_r9jvp-3ySZuRHjLC
        returns: us-west-2
        """
        parts: Final = arn.split(":")
        if len(parts) >= 4:
            return parts[3]
        raise ValueError(f"Invalid ARN format: {arn}")

    def _get_runtime_session_id(self, optional_params: dict) -> str:
        """
        Get or generate runtime session ID (must be 33+ chars)

View on GitHub (pinned to 6c2dcb801b)

Solutions

1. Use model format 'bedrock/agentcore/arn:aws:bedrock-agentcore:region:account:runtime/runtime_id'.

When it happens

Trigger: Thrown at litellm/llms/bedrock/chat/agentcore/transformation.py:163 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BerriAI/litellm@6c2dcb801b (2026-08-15). Data as JSON: /api/errors/bbd2768eec8265f5. Report an issue: GitHub.