mastra-ai/mastra · error

AcpAgent does not support resuming suspended stream calls

Error message

AcpAgent does not support resuming suspended stream calls

What it means

The Mastra instance has a storage adapter, but storage.getStore('agents') returned undefined, meaning the adapter in use does not implement/expose the agents domain store. Versioning handlers require the agents store specifically and fail closed with a 500 HTTPException.

Source

Thrown at agent-sdks/acp/src/agent.ts:123

    const messageList = this.createMessageList(messages, text);

    return {
      text,
      response: {
        dbMessages: messageList.get.response.db(),
      },
      toolResults: [],
      finishReason: 'stop',
      runId: options?.runId ?? randomUUID(),
    };
  }

  async resumeGenerate(): Promise<SubAgentGenerateResult> {
    throw new Error('AcpAgent does not support resuming suspended generate calls');
  }

  async resumeStream(): Promise<SubAgentStreamResult> {
    throw new Error('AcpAgent does not support resuming suspended stream calls');
  }

  async stream(messages: MessageListInput, options?: AgentStreamOptions): Promise<SubAgentStreamResult> {
    const runId = options?.runId ?? randomUUID();
    const prompt = this.getPrompt(messages, options?.instructions);
    const signal = (options as { abortSignal?: AbortSignal } | undefined)?.abortSignal;
    const messageList = new MessageList();
    messageList.add(messages, 'input');

    let resolveText!: (text: string) => void;
    let rejectText!: (error: unknown) => void;
    const textPromise = new Promise<string>((resolve, reject) => {
      resolveText = resolve;
      rejectText = reject;
    });

    const fullStream = new ReadableStream<ChunkType>({
      start: async controller => {

View on GitHub (pinned to 75dd419e61)

Solutions

1. Switch to a storage adapter that implements the agents store (Postgres/Upstash/LibSQL/etc. official adapters)
2. Update the storage adapter package to the latest version so all domain stores are implemented
3. If using a custom adapter, implement getStore('agents') (getById, getVersion, listVersions, etc.)
4. Check the version matrix between @mastra/core and the storage adapter package for compatibility

Example fix

// before
storage: new MinimalStorage({ connection }) // no agents domain
// after
storage: new PostgresStore({ connectionString: process.env.DATABASE_URL }) // implements agents store

const storage = mastra.getStorage();
if (!storage || typeof storage.getStore !== 'function') throw new Error('Invalid storage adapter');
const agentsStore = await storage.getStore('agents');
if (!agentsStore) throw new Error('Storage adapter does not implement agents domain');

function implementsAgentsStore(s: any): boolean {
  const store = s?.getStore?.('agents');
  return !!store && typeof store.getById === 'function' && typeof store.getVersion === 'function';
}

try {
  await callAgentVersionsApi();
} catch (e) {
  if (isHttpError(e) && e.status === 500 && /Agents storage domain is not available/.test(e.message)) {
    // swap to an adapter implementing the agents store
  } else throw e;
}

When it happens

Trigger: Calling an agent-version endpoint when the storage adapter lacks the agents domain (e.g. a minimal/custom storage implementation that doesn't define getStore('agents'), or a legacy adapter predating the agents store).

Common situations: Custom storage adapters that implement only some domains (workflows, traces) but not agents; using an in-memory or third-party adapter that hasn't implemented the agents store; upgrading Mastra while keeping an old adapter that is missing new domain stores.

Related errors

• ClaudeSDKAgent resumeData must include a message.
• AcpAgent does not support resuming suspended generate calls
• ACP prompt stopped before completing: ${response.stopReason}
• MCP clients storage domain is not available
• Memory storage was not available while storing the response

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/4401758e595176eb. Report an issue: GitHub.