mastra-ai/mastra · error

CursorSDKAgent resumeData must include a message.

Error message

CursorSDKAgent resumeData must include a message.

What it means

validateCursorResumeData requires resumeData to be a record containing a 'message' property — the conversation payload Cursor uses to resume an agent run. It throws when resumeData is not an object or lacks the message key.

Solutions

  1. Include the original conversation message in resumeData: resume({ message: savedMessage }).
  2. Persist the full CursorSDKAgentResumeData object returned/required by the agent, not just the agentId.
  3. Check resumeData is a non-null object with a 'message' key before calling resume.

Example fix

// before
await agent.resume({ agentId: saved.agentId });
// after
await agent.resume({ message: saved.message, agentId: saved.agentId });
Defensive patterns

Strategy: validation

Validate before calling

function canResumeCursor(data: unknown): boolean {
  return typeof data === 'object' && data !== null && 'message' in data;
}
if (!canResumeCursor(saved)) throw new Error('Saved Cursor resume data is missing message');
await agent.resume(saved);

Type guard

function isCursorResumeData(v: unknown): v is CursorSDKAgentResumeData {
  return typeof v === 'object' && v !== null && 'message' in v &&
    ((v as any).agentId === undefined || typeof (v as any).agentId === 'string');
}

Try / catch

try {
  await agent.resume(saved);
} catch (e) {
  if (e instanceof Error && e.message.includes('resumeData must include a message')) {
    // start a fresh run instead
    await agent.generate(prompt);
  } else throw e;
}

Prevention

When it happens

Trigger: cursorSDKAgent.resume(data) called with an empty object, a non-object (string/null/undefined), or an object holding only other fields like agentId but no message.

Common situations: Saving only the Cursor agentId after a run and trying to resume with just { agentId }; resuming with resume data persisted from a different SDK (e.g. Claude's sessionId-shaped data).

Related errors

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/1829ef666c2645f3. Report an issue: GitHub.

Appendix: source

Thrown at agent-sdks/cursor/src/index.ts:290

    });
    return this.#createdAgent;
  }

  private async resolveResumeCursorAgent(resumeData: CursorSDKAgentResumeData): Promise<SDKAgent> {
    if (!resumeData.agentId) {
      return this.resolveCursorAgent();
    }

    return CursorAgent.resume(resumeData.agentId, {
      ...toCursorCreateOptions(this.options),
      ...resumeData.sdkOptions,
    });
  }
}

function validateCursorResumeData(resumeData: CursorSDKAgentResumeData): CursorSDKAgentResumeData {
  if (!toRecord(resumeData) || !('message' in resumeData)) {
    throw new Error('CursorSDKAgent resumeData must include a message.');
  }

  if (resumeData.agentId !== undefined && typeof resumeData.agentId !== 'string') {
    throw new Error('CursorSDKAgent resumeData.agentId must be a string when provided.');
  }

  return resumeData;
}

function assertStructuredOutputUnsupported(options?: unknown): void {
  const structuredOutput = toRecord(toRecord(options)?.structuredOutput);
  if (structuredOutput && 'schema' in structuredOutput) {
    throw new Error(
      'CursorSDKAgent does not support structuredOutput because the Cursor TypeScript SDK does not expose a schema-constrained output API.',
    );
  }
}

View on GitHub (pinned to 75dd419e61)