microsoft/semantic-kernel · error · AgentChatException

Failed to delete thread: {e}

Error message

Failed to delete thread: {e}

What it means

Raised by AzureAIChannel.reset when client.agents.threads.delete raises any exception during a channel reset. The original exception is interpolated into the message (not chained via 'from'), limiting introspection. Surfaced as AgentChatException.

Source

Thrown at python/semantic_kernel/agents/azure_ai/azure_ai_channel.py:121

            yield message

    @override
    async def get_history(self) -> AsyncIterable["ChatMessageContent"]:
        """Get the conversation history.

        Yields:
            ChatMessageContent: The conversation history.
        """
        async for message in AgentThreadActions.get_messages(self.client, thread_id=self.thread_id):
            yield message

    @override
    async def reset(self) -> None:
        """Reset the agent's thread."""
        try:
            await self.client.agents.threads.delete(thread_id=self.thread_id)
        except Exception as e:
            raise AgentChatException(f"Failed to delete thread: {e}")

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Make reset tolerant of 'not found'/404 by catching AgentChatException and inspecting the embedded message/cause.
2. Avoid calling reset() multiple times on the same channel without coordination.
3. Retry transient network/5xx errors with backoff during reset.

Example fix

try:
    await channel.reset()
except AgentChatException as e:
    if 'not found' not in str(e).lower() and not _is_transient(e):
        raise

from semantic_kernel.exceptions.agent_exceptions import AgentChatException
try:
    await channel.reset()
except AgentChatException as e:
    msg = str(e).lower()
    if 'not found' in msg:
        return  # thread already gone -> treat reset as success
    if _is_transient_text(msg):
        await asyncio.sleep(backoff); await channel.reset()
    else:
        raise

When it happens

Trigger: Resetting a channel whose thread was already deleted server-side; auth/network failure during reset; the thread_id belongs to a different project; concurrent reset/delete by another client.

Common situations: Group-chat teardown calling reset() on a channel whose thread was already cleaned up; a thread deleted out-of-band; expired credential at teardown time; transient 5xx during shutdown.

Related errors

• The thread could not be deleted due to an error response fro
• Agent is not of the expected type {type(AzureAIAgent)}.
• The message could not be added to the thread due to an error
• The thread could not be created due to an error response fro
• The thread cannot be deleted because it has not been created

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/6fabbfaacf5f2913. Report an issue: GitHub.