mastra-ai/mastra · error

Failed to check whether Slack app exists: ${data.error ?? 'u

Error message

Failed to check whether Slack app exists: ${data.error ?? 'unknown_error'}

What it means

appExists checks whether the Slack app still exists. It returns false for the expected 'not found' errors (app_not_found, invalid_app_id) but any OTHER error is unexpected — it could be transient — so the client re-throws rather than reporting false, preventing callers from tearing down a valid installation on a temporary failure.

Source

Thrown at channels/slack/src/client.ts:228

    });

    const data = (await response.json()) as {
      ok: boolean;
      error?: string;
    };

    if (data.ok) return true;

    // Only a definitive "app is gone" answer counts as non-existence. Slack
    // returns `app_not_found` when the app was deleted and `invalid_app_id`
    // when the id is malformed. Any other error (rate limiting, auth, outage)
    // is transient — re-throw so callers don't tear down a valid installation
    // on a temporary failure.
    if (data.error === 'app_not_found' || data.error === 'invalid_app_id') {
      return false;
    }

    throw new Error(`Failed to check whether Slack app exists: ${data.error ?? 'unknown_error'}`);
  }

  /**
   * Update an existing Slack app's manifest.
   */
  async updateApp(appId: string, manifest: SlackAppManifest): Promise<void> {
    await this.rotateToken();

    const response = await fetch(`${SLACK_API_BASE}/apps.manifest.update`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${this.#token}`,
      },
      body: JSON.stringify({ app_id: appId, manifest }),
      signal: AbortSignal.timeout(SLACK_API_TIMEOUT_MS),
    });

View on GitHub (pinned to 75dd419e61)

Solutions

1. Retry the connect/appExists call after a short backoff — the error is often transient
2. Verify app configuration tokens are valid (invalid_auth → get fresh tokens from the Slack app config)
3. Check Slack's status page if errors persist, and only treat the app as missing when appExists returns false

Example fix

// before
const exists = await client.appExists(appId); // throws on transient error
// after
let exists: boolean;
try { exists = await client.appExists(appId); }
catch (e) { exists = true; /* assume exists; don't tear down on transient failure */ }

let exists: boolean;
try {
  exists = await client.appExists(appId);
} catch (e) {
  // transient failure: assume the app exists rather than tearing down a valid install
  logger.warn({ err: e }, 'appExists check failed; assuming exists');
  exists = true;
}

When it happens

Trigger: appExists() (called from connect) receives { ok: false, error: X } where X is neither app_not_found nor invalid_app_id — e.g. fatal_error, invalid_auth, rateLimited, network-level issues surfaced as Slack errors.

Common situations: Slack API outage or rate limiting during channel connect; bad/expired app configuration token; intermittent network failures in deployment environments.

Related errors

• Token rotation failed: ${data.error}
• App creation failed: ${errorDetails}
• App deletion failed: ${data.error}
• Slack refresh token is invalid. Get fresh tokens from https:
• Token rotation returned incomplete data

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/e34ce8d3b0229a58. Report an issue: GitHub.