DIYgod/RSSHub · critical · Error

Cannot start TG: ${err}

Error message

Cannot start TG: ${err}

What it means

getClient calls client.start(...) with an onError callback that re-throws the underlying Telegram client start error wrapped as 'Cannot start TG: <err>'. The wrapped error is whatever caused MTProto connection/authentication to fail: bad session, auth challenge, proxy failure, or network error.

Source

Thrown at lib/routes/telegram/tglib/client.ts:39

        connectionRetries: Infinity,
        autoReconnect: true,
        retryDelay: 3000,
        maxConcurrentDownloads: Number(config.telegram.maxConcurrentDownloads ?? 10),
        proxy:
            config.telegram.proxy?.host && config.telegram.proxy.port && config.telegram.proxy.secret
                ? {
                      ip: config.telegram.proxy.host,
                      port: Number(config.telegram.proxy.port),
                      MTProxy: true,
                      secret: config.telegram.proxy.secret,
                  }
                : undefined,
    });

    await client.start(
        Object.assign(authParams ?? {}, {
            onError: (err: Error) => {
                throw new Error('Cannot start TG: ' + err);
            },
        }) as any
    );
    return client;
}

export function getFilename(x: Api.TypeMessageMedia) {
    if (x instanceof Api.MessageMediaDocument) {
        for (const a of (x.document as Api.Document).attributes) {
            if (a instanceof Api.DocumentAttributeFilename) {
                return a.fileName;
            }
        }
    }
    return x.className;
}

export function getDocument(m: Api.TypeMessageMedia) {

View on GitHub (pinned to bed535e087)

Solutions

  1. Read the wrapped err string to identify the root cause (auth_key not found, SESSION_REVOKED, FLOOD_WAIT, proxy timeout) before changing anything.
  2. Regenerate TELEGRAM_SESSION and verify TELEGRAM_API_ID/TELEGRAM_API_HASH are correct for your app.
  3. If using config.telegram.proxy, confirm the proxy host/port/secret are reachable and valid; test without the proxy first.
  4. Reduce retry pressure: the connectionRetries:Infinity setting can turn a transient error into a floodwait; retry the whole feed fetch after a delay instead of relying on infinite MTProto retries.

Example fix

// before
await client.start(
    Object.assign(authParams ?? {}, {
        onError: (err: Error) => {
            throw new Error('Cannot start TG: ' + err);
        },
    }) as any
);

// after: preserve the original error type for upstream handling
await client.start(
    Object.assign(authParams ?? {}, {
        onError: (err: Error) => {
            const e = new Error('Cannot start TG: ' + err.message, { cause: err });
            e.name = err.name || 'TelegramStartError';
            throw e;
        },
    }) as any
);
Defensive patterns

Strategy: try-catch

Validate before calling

import { config } from '@/config';
function canStartTelegram(): boolean {
    return Boolean(config.telegram?.session) && Boolean(config.telegram?.apiId) && Boolean(config.telegram?.apiHash);
}
// do not call getClient() until canStartTelegram() is true

Type guard

function telegramStartConfigComplete(): boolean {
    const t = config.telegram as { session?: string; apiId?: string | number; apiHash?: string } | undefined;
    return Boolean(t?.session && t?.apiHash);
}

Try / catch

try {
    return await getClient(authParams);
} catch (e) {
    if (e instanceof Error && /Cannot start TG:/.test(e.message)) {
        const cause = e.message;
        if (/FLOOD_WAIT/i.test(cause)) {
            await sleep(60_000);
            return await getClient(authParams);
        }
        if (/SESSION_REVOKED|AUTH_KEY/i.test(cause)) {
            throw new Error('TELEGRAM_SESSION is invalid or revoked; regenerate it.');
        }
        throw e;
    }
    throw e;
}

Prevention

When it happens

Trigger: client.start tries to connect to Telegram over the configured (optional) MTProxy or direct connection; the start promise rejects because the session is invalid, the API credentials are wrong, the proxy is unreachable, or Telegram rate-limits the connection.

Common situations: TELEGRAM_SESSION string is malformed or logged-out; TELEGRAM_API_ID/API_HASH mismatch; a configured MTProxy (config.telegram.proxy) is down; floodwait/TooManyRequests from repeated connect attempts; connectionRetries:Infinity amplifying a flapping network.

Related errors

AI-assisted analysis of DIYgod/RSSHub@bed535e087 (2026-08-12). Data as JSON: /api/errors/d7c5db132e450ec6. Report an issue: GitHub.