mastra-ai/mastra · error

No agent or agent controller found with id "${agentId}"

Error message

No agent or agent controller found with id "${agentId}"

What it means

In the object form connect({ id, name }), the id may belong to either a registered agent or an AgentController (since the agent may not exist yet). If #resolveAgent and #resolveAgentController both fail, the provider has no owner for the installation and throws this error.

Source

Thrown at channels/slack/src/provider.ts:1063

    const baseUrl = this.#getBaseUrl();
    if (!baseUrl) {
      throw new Error(
        'SlackProvider baseUrl not set. Configure studioHost/studioProtocol/studioPort in Mastra server config, or call setBaseUrl().',
      );
    }

    // In the agentId form, the agent must exist. In the options form the id may
    // belong to a registered agent or an AgentController — resolve which one so
    // the installation records who owns it.
    const agent = this.#resolveAgent(agentId);
    if (isAgentIdForm && !agent) {
      throw new Error(`Agent "${agentId}" not found`);
    }
    let ownerType: SlackOwnerType = 'agent';
    if (!isAgentIdForm && !agent) {
      const controller = this.#resolveAgentController(agentId);
      if (!controller) {
        throw new Error(`No agent or agent controller found with id "${agentId}"`);
      }
      ownerType = 'agentController';
    }

    // If there's already a pending installation, return its authorization URL
    // instead of creating a duplicate Slack app
    const storage = await this.#getStorage();
    const existingRecord = await storage.getInstallationByAgent(PLATFORM, agentId);
    if (existingRecord?.status === 'pending') {
      try {
        const pending = this.#parsePendingInstallation(existingRecord);
        const decrypted = this.#decryptPendingInstallation(pending);

        // The stored Slack app may have been deleted out-of-band (e.g. removed
        // from the Slack admin UI). Reusing its authorizationUrl would hand the
        // caller a dead link (`Invalid client_id`). Probe existence first and,
        // if the app is gone, drop the pending record and create a fresh app.
        let appStillExists = true;

View on GitHub (pinned to 75dd419e61)

Solutions

1. Register an AgentController with the given id on the Mastra instance, or use an id of an existing controller.
2. Use an existing registered agent's id with connect(agentId) instead.
3. Log/list available agents and controllers before connecting to pick a valid id.

Example fix

// before
await provider.connect({ id: 'ghost-controller', name: 'Bot' });
// after
mastra.registerAgentController(new AgentController({ id: 'ghost-controller' }));
await provider.connect({ id: 'ghost-controller', name: 'Bot' });

const known = [...Object.keys(mastra.getAgents?.() ?? {}), ...listRegisteredControllerIds(mastra)];
if (!known.includes(id)) {
  throw new Error(`id "${id}" is neither an agent nor an agent controller`);
}

try {
  await provider.connect({ id, name });
} catch (err) {
  if (err instanceof Error && err.message.includes('No agent or agent controller found')) {
    console.error('Register the agent or AgentController with this id before connecting');
  } else throw err;
}

When it happens

Trigger: provider.connect({ id: 'x', name: 'Y' }) where 'x' matches neither a registered Agent nor a registered AgentController on the attached Mastra instance.

Common situations: Passing a made-up id intending the library to create an agent (it does not); controller not registered with Mastra; id from another environment; typos in the id.

Related errors

• Agent "${agentId}" not found
• App creation failed: ${errorDetails}
• App manifest update failed: ${errorDetails}
• connect({ id, name }): "name" is required when connecting wi
• Agent ID is required

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/6fd095d5eea2ab8d. Report an issue: GitHub.