microsoft/semantic-kernel · error · AgentChatException

Agent is not of the expected type {type(BedrockAgent)}.

Error message

Agent is not of the expected type {type(BedrockAgent)}.

What it means

Raised by BedrockAgentChannel.invoke (an AgentChatException) when the supplied agent is not an instance of BedrockAgent. Channels are agent-type-specific; the Bedrock channel only knows how to drive a BedrockAgent, so any other agent type is rejected before invocation.

Source

Thrown at python/semantic_kernel/agents/channels/bedrock_agent_channel.py:59

    thread: "BedrockAgentThread"
    MESSAGE_PLACEHOLDER: ClassVar[str] = "[SILENCE]"

    @override
    async def invoke(self, agent: "Agent", **kwargs: Any) -> AsyncIterable[tuple[bool, ChatMessageContent]]:
        """Perform a discrete incremental interaction between a single Agent and AgentChat.

        Args:
            agent: The agent to interact with.
            kwargs: Additional keyword arguments.

        Returns:
            An async iterable of ChatMessageContent with a boolean indicating if the
            message should be visible external to the agent.
        """
        from semantic_kernel.agents.bedrock.bedrock_agent import BedrockAgent

        if not isinstance(agent, BedrockAgent):
            raise AgentChatException(f"Agent is not of the expected type {type(BedrockAgent)}.")
        if not self.messages:
            # This is not supposed to happen, as the channel won't get invoked
            # before it has received messages. This is just extra safety.
            raise AgentChatException("No chat history available.")

        # Preprocess chat history
        await self._ensure_history_alternates()
        await self._ensure_last_message_is_user()

        async for response in agent.invoke(
            messages=self.messages[-1].content,
            thread=self.thread,
            sessionState=await self._parse_chat_history_to_session_state(),
        ):
            # All messages from Bedrock agents are user facing, i.e., function calls are not returned as messages
            self.messages.append(response.message)
            yield True, response.message

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Ensure only BedrockAgent instances are invoked through the BedrockAgentChannel / added to that agent group chat.
2. Separate agents by type into compatible groups, or use AgentGroupChat which routes each agent to its own channel.
3. Verify the agent object you pass is the concrete BedrockAgent subclass, not a parent or sibling type.
4. Check that agent construction returns the intended subclass (no factory returning a wrong type).

Example fix

// before
chat = AgentGroupChat(agent=chat_completion_agent)  # wrong channel/type
await chat.invoke()  # raises in bedrock channel
// after
chat = AgentGroupChat(agent=bedrock_agent)  # matching types
await chat.invoke()

from semantic_kernel.agents.bedrock.bedrock_agent import BedrockAgent
def assert_bedrock(agent):
    if not isinstance(agent, BedrockAgent):
        raise TypeError(f'Expected BedrockAgent, got {type(agent)}')
    return agent

def is_bedrock_agent(agent) -> bool:
    from semantic_kernel.agents.bedrock.bedrock_agent import BedrockAgent
    return isinstance(agent, BedrockAgent)

from semantic_kernel.exceptions.agent_exceptions import AgentChatException
try:
    await chat.invoke(agent=agent)
except AgentChatException as e:
    if 'expected type' in str(e): raise TypeError(e)
    raise

When it happens

Trigger: Registering/invoking a non-Bedrock agent (e.g. ChatCompletionAgent, OpenAIAssistantAgent) through an AgentGroupChat or channel that was created for a BedrockAgent; mixing agent types in a group chat where the channel type mismatches.

Common situations: Adding agents of different concrete types to an AgentGroupChat and letting the wrong channel receive a foreign agent; refactoring that swaps an agent's base type without updating the group; incorrect agent construction returning a base Agent instead of BedrockAgent.

Related errors

• Agent is not of the expected type {type(OpenAIAssistantAgent
• Agent is not of the expected type {type(AzureAIAgent)}.
• No chat history available.
• Channel Keys must not be empty. Unable to generate channel h
• No file found in the response.

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/c4e4856c1ad501d4. Report an issue: GitHub.