mastra-ai/mastra · error · HTTPException

Conversation ${conversationId} was not found

Error message

Conversation ${conversationId} was not found

What it means

When conversation_id is provided and the agent has memory, the server looks up the thread via memory.getThreadById. If no thread exists with that ID, it throws this 404 — the API does not silently create threads for arbitrary user-supplied conversation IDs.

Source

Thrown at packages/server/src/server/handlers/responses.ts:212

  if (!store && !conversationId && !effectiveThreadId) {
    return null;
  }

  const memory = await agent.getMemory({ requestContext });
  if (!memory) {
    if (conversationId) {
      throw new HTTPException(400, {
        message: 'conversation_id requires the target agent to have memory configured',
      });
    }

    return null;
  }

  if (conversationId) {
    const existingThread = await memory.getThreadById({ threadId: conversationId });
    if (!existingThread) {
      throw new HTTPException(404, { message: `Conversation ${conversationId} was not found` });
    }

    await enforceThreadAccess({
      mastra: agent.getMastraInstance(),
      requestContext,
      threadId: conversationId,
      thread: existingThread,
      effectiveResourceId,
    });
    return {
      threadId: existingThread.id,
      resourceId: effectiveResourceId ?? existingThread.resourceId,
    };
  }

  if (!effectiveThreadId) {
    if (!store) {
      return null;

View on GitHub (pinned to 75dd419e61)

Solutions

1. Create the conversation first (send a request without conversation_id and use the returned thread/conversation id, or explicitly create a thread via memory API)
2. Verify the conversation_id exists in the storage backend the server is actually connected to
3. Check for typos or stale cached IDs in the client; refresh from the last API response
4. Point the server at the environment/database where the thread was created

Example fix

// before
const r = await client.responses.create({ agent_id: 'a', conversation_id: crypto.randomUUID(), input: 'hi' }); // never created
// after
const first = await client.responses.create({ agent_id: 'a', input: 'hi' });
const r = await client.responses.create({ agent_id: 'a', conversation_id: first.threadId, input: 'next' });

const thread = conversationId ? await memory.getThreadById({ threadId: conversationId }) : null;
if (conversationId && !thread) throw new Error(`Conversation ${conversationId} does not exist yet`);

null

try {
  await client.responses.create({ agent_id, conversation_id: id, input });
} catch (e) {
  if (e?.status === 404 && /was not found/.test(e.message)) {
    const first = await client.responses.create({ agent_id, input }); // create conversation, then retry
    return client.responses.create({ agent_id, conversation_id: first.threadId, input });
  }
  throw e;
}

When it happens

Trigger: POST /api/responses with a conversation_id that was never created (no prior request created the thread), a deleted thread, a typo in the ID, or a thread belonging to a different storage backend/environment (e.g., staging DB vs production).

Common situations: Client generating its own UUID for conversation_id instead of using one returned by a previous response; pointing at a fresh database; running against a different environment than where the conversation was created; thread cleanup jobs deleting old threads.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Stored response ${body.previous_response_id} was not found
• Stored response ${responseId} was not found
• Scorer with id ${scorerId} not found
• Version with id ${versionId} not found
• AcpAgent does not support resuming suspended generate calls

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/04430d610a2fd543. Report an issue: GitHub.