mastra-ai/mastra · error · HTTPException

Stored response ${body.previous_response_id} was not found

Error message

Stored response ${body.previous_response_id} was not found

What it means

When previous_response_id is supplied, the server looks up the stored response turn record. If no record exists with that ID, prepareCreateResponseRequest throws this 404 — chaining requires a real, previously stored response.

Source

Thrown at packages/server/src/server/handlers/responses.ts:669

      if (!previousResponseTurnRecord) {
        const owningResponseTurnRecord = await findResponseTurnRecordAcrossAgents({
          mastra,
          responseId: body.previous_response_id,
          requestContext,
        });

        if (owningResponseTurnRecord) {
          if (owningResponseTurnRecord.metadata.agentId === body.agent_id) {
            previousResponseTurnRecord = owningResponseTurnRecord;
          } else {
            throw new HTTPException(400, {
              message: `Stored response ${body.previous_response_id} belongs to agent ${owningResponseTurnRecord.metadata.agentId}, not ${body.agent_id}`,
            });
          }
        }

        if (!previousResponseTurnRecord) {
          throw new HTTPException(404, { message: `Stored response ${body.previous_response_id} was not found` });
        }
      }
    } else {
      if (!mastra) {
        throw new HTTPException(500, { message: 'Mastra instance is required for agent-backed responses' });
      }

      previousResponseTurnRecord = await findResponseTurnRecordAcrossAgents({
        mastra,
        responseId: body.previous_response_id,
        requestContext,
      });

      if (!previousResponseTurnRecord) {
        throw new HTTPException(404, { message: `Stored response ${body.previous_response_id} was not found` });
      }
    }
  }

View on GitHub (pinned to 75dd419e61)

Solutions

Verify the previous_response_id came from an actual prior response in the same environment/storage
Drop previous_response_id to start a new conversation
Check the server's storage backend contains the response turn record
Fix client caching so ids are taken from the latest stored response, not stale state

Example fix

// before
const r = await client.responses.create({ agent_id: 'a', previous_response_id: 'resp_hardcoded_123', input: 'more' });
// after
const first = await client.responses.create({ agent_id: 'a', input: 'hi' });
const r = await client.responses.create({ agent_id: 'a', previous_response_id: first.id, input: 'more' });

Defensive patterns

Strategy: try-catch

Validate before calling

if (previousResponseId && !(await responseExists(previousResponseId))) throw new Error(`Stored response ${previousResponseId} missing`);

Type guard

null

Try / catch

try {
  return await client.responses.create({ agent_id, previous_response_id, input });
} catch (e) {
  if (e?.status === 404 && /was not found/.test(e.message)) {
    return client.responses.create({ agent_id, input }); // start fresh conversation
  }
  throw e;
}

Prevention

Only chain from response ids actually returned by prior stored responses
Clear stale ids after storage resets or environment switches
Check storage retention policies before long-lived chaining

When it happens

Trigger: POST /api/responses with a previous_response_id that was never created, was created with store semantics off, was deleted, or exists in a different database/environment.

Common situations: Replaying old session ids against a fresh DB; typo'd or fabricated response ids; retention/cleanup removing old turns; pointing the client at another environment than where the response was stored.

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

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/b62482eee2ea006a. Report an issue: GitHub.