Error Handling

grammY provides three main error types to help you handle different failure scenarios in your bot.

BotError<C>

Thrown when middleware throws an error. Wraps the original error and provides access to the context.

class BotError<C extends Context = Context> extends Error {
  constructor(
    public readonly error: unknown,
    public readonly ctx: C
  )
}

Properties

error: The original error that was thrown by your middleware
ctx: The context object being processed when the error occurred
message: A descriptive error message
name: Always "BotError"
stack: Stack trace from the original error (if available)

When it occurs

BotError is thrown whenever an error occurs during middleware execution:

bot.on('message', (ctx) => {
  throw new Error('Something went wrong!')  // Will be wrapped in BotError
})

bot.on('message', async (ctx) => {
  await riskyOperation()  // If this throws, it becomes BotError
})

Handling BotError

Use bot.catch() to install an error handler:

import { BotError } from 'grammy'

bot.catch((err: BotError) => {
  const ctx = err.ctx
  console.error(`Error while handling update ${ctx.update.update_id}:`)
  
  const e = err.error
  
  if (e instanceof GrammyError) {
    console.error('Error in request:', e.description)
  } else if (e instanceof HttpError) {
    console.error('Could not contact Telegram:', e)
  } else {
    console.error('Unknown error:', e)
  }
})

Accessing context from errors

The ctx property lets you access update information when an error occurs:

bot.catch(async (err: BotError) => {
  const ctx = err.ctx
  
  // Notify user about the error
  if (ctx.chat) {
    await ctx.reply('Sorry, an error occurred while processing your request.')
  }
  
  // Log detailed information
  console.error('Error details:', {
    updateId: ctx.update.update_id,
    userId: ctx.from?.id,
    chatId: ctx.chat?.id,
    error: err.error
  })
})

Example: Retry on error

bot.catch(async (err: BotError) => {
  if (err.error instanceof GrammyError) {
    if (err.error.error_code === 429) {
      // Rate limited - retry after delay
      const retryAfter = err.error.parameters.retry_after ?? 30
      console.log(`Rate limited. Retrying after ${retryAfter}s`)
      await new Promise(resolve => setTimeout(resolve, retryAfter * 1000))
      // Re-handle the update
      await bot.handleUpdate(err.ctx.update)
    }
  }
})

GrammyError

Thrown when the Telegram Bot API returns an error response.

class GrammyError extends Error implements ApiError {
  public readonly ok: false = false
  public readonly error_code: number
  public readonly description: string
  public readonly parameters: ResponseParameters
  
  constructor(
    message: string,
    err: ApiError,
    public readonly method: string,
    public readonly payload: Record<string, unknown>
  )
}

Properties

error_code: Telegram’s error code (e.g., 400, 404, 429)
description: Human-readable error description from Telegram
parameters: Additional parameters (e.g., retry_after for rate limits)
method: The API method that was called (e.g., "sendMessage")
payload: The parameters passed to the API method
ok: Always false

Common Error Codes

Code	Description
400	Bad Request - invalid parameters
401	Unauthorized - invalid bot token
403	Forbidden - no permission to perform action
404	Not Found - resource doesn’t exist
409	Conflict - bot is already running elsewhere
429	Too Many Requests - rate limited
500	Internal Server Error - Telegram server issue

When it occurs

GrammyError is thrown when Telegram’s API returns an error:

try {
  await ctx.reply('Hello!')
} catch (err) {
  if (err instanceof GrammyError) {
    console.error('Telegram API error:', err.description)
  }
}

Example: Handling specific errors

import { GrammyError } from 'grammy'

try {
  await bot.api.sendMessage(chatId, text)
} catch (err) {
  if (err instanceof GrammyError) {
    switch (err.error_code) {
      case 400:
        console.error('Bad request:', err.description)
        break
      
      case 403:
        console.error('Bot was blocked by user')
        // Remove user from database
        break
      
      case 429:
        const retryAfter = err.parameters.retry_after
        console.error(`Rate limited. Retry after ${retryAfter}s`)
        break
      
      default:
        console.error('Telegram error:', err)
    }
  }
}

Example: Handling message deletion

try {
  await ctx.deleteMessage()
} catch (err) {
  if (err instanceof GrammyError) {
    if (err.description.includes('message to delete not found')) {
      console.log('Message already deleted')
    } else if (err.description.includes("message can't be deleted")) {
      console.log('Message is too old to delete')
    } else {
      throw err  // Re-throw unknown errors
    }
  }
}

Example: Handling bot blocking

bot.on('message', async (ctx) => {
  try {
    await ctx.reply('Hello!')
  } catch (err) {
    if (err instanceof GrammyError) {
      if (err.error_code === 403) {
        console.log(`User ${ctx.from.id} blocked the bot`)
        // Update user status in database
        await db.users.update(ctx.from.id, { blocked: true })
      }
    }
  }
})

ResponseParameters

Some errors include additional parameters:

interface ResponseParameters {
  migrate_to_chat_id?: number      // Group migrated to supergroup
  retry_after?: number             // Seconds to wait before retry
}

Example:

try {
  await ctx.reply('Message')
} catch (err) {
  if (err instanceof GrammyError) {
    if (err.parameters.migrate_to_chat_id) {
      const newChatId = err.parameters.migrate_to_chat_id
      console.log(`Chat migrated to ${newChatId}`)
      // Update chat ID in database
    }
  }
}

HttpError

Thrown when the HTTP request to Telegram’s servers fails.

class HttpError extends Error {
  constructor(
    message: string,
    public readonly error: unknown
  )
}

Properties

error: The underlying network error
message: Descriptive error message
name: Always "HttpError"

When it occurs

HttpError is thrown when:

Network connection fails
DNS resolution fails
Request times out
Connection is aborted
API transformer function throws

import { HttpError } from 'grammy'

try {
  await bot.api.sendMessage(chatId, 'Hello')
} catch (err) {
  if (err instanceof HttpError) {
    console.error('Network error:', err.error)
    // Retry logic here
  }
}

Example: Retry on network failure

import { HttpError } from 'grammy'

async function sendWithRetry(chatId: number, text: string, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      return await bot.api.sendMessage(chatId, text)
    } catch (err) {
      if (err instanceof HttpError) {
        console.log(`Network error. Retry ${i + 1}/${maxRetries}`)
        if (i === maxRetries - 1) throw err  // Last retry failed
        await new Promise(resolve => setTimeout(resolve, 1000 * (i + 1)))
      } else {
        throw err  // Not a network error
      }
    }
  }
}

Error Handling Patterns

Global Error Handler

Handle all errors in one place:

import { BotError, GrammyError, HttpError } from 'grammy'

bot.catch((err: BotError) => {
  const e = err.error
  
  if (e instanceof GrammyError) {
    console.error('API Error:', e.description)
    
    if (e.error_code === 401) {
      console.error('Invalid bot token!')
      process.exit(1)
    }
  } else if (e instanceof HttpError) {
    console.error('Network error:', e)
  } else {
    console.error('Unknown error:', e)
  }
})

Local Error Handling

Handle errors in specific middleware:

bot.command('start', async (ctx) => {
  try {
    await ctx.reply('Welcome!')
  } catch (err) {
    console.error('Failed to send welcome message:', err)
    // Don't crash the bot, just log it
  }
})

Error Boundaries

Create protected middleware sections:

bot.errorBoundary(
  (err) => {
    console.error('Error in admin commands:', err)
  },
  adminCommands.middleware()
)

Ignore Specific Errors

Silently handle expected errors:

bot.on('message', async (ctx) => {
  try {
    await ctx.deleteMessage()
  } catch (err) {
    if (err instanceof GrammyError) {
      // Ignore "message not found" errors
      if (!err.description.includes('message to delete not found')) {
        throw err
      }
    } else {
      throw err
    }
  }
})

Custom Error Classes

Create application-specific errors:

class UserNotFoundError extends Error {
  constructor(public userId: number) {
    super(`User ${userId} not found`)
    this.name = 'UserNotFoundError'
  }
}

bot.on('message', async (ctx) => {
  const user = await db.findUser(ctx.from.id)
  if (!user) {
    throw new UserNotFoundError(ctx.from.id)
  }
  // ...
})

bot.catch((err: BotError) => {
  if (err.error instanceof UserNotFoundError) {
    console.log('New user:', err.error.userId)
    // Create user in database
  }
})

Error Logging

Log errors with context:

bot.catch(async (err: BotError) => {
  const errorLog = {
    timestamp: new Date().toISOString(),
    updateId: err.ctx.update.update_id,
    userId: err.ctx.from?.id,
    chatId: err.ctx.chat?.id,
    errorType: err.error?.constructor.name,
    errorMessage: err.error instanceof Error ? err.error.message : String(err.error),
    stack: err.stack
  }
  
  console.error(JSON.stringify(errorLog, null, 2))
  
  // Send to external logging service
  await logger.error(errorLog)
})

Best Practices

Always set an error handler

bot.catch((err) => {
  console.error('Bot error:', err)
})

Handle specific errors explicitly

if (err instanceof GrammyError && err.error_code === 403) {
  // User blocked the bot
}

Don’t leak sensitive information

// ❌ Bad - might expose token in logs
console.error(err)

// ✅ Good - sanitize error
console.error(err.description)

Implement retry logic for transient errors

if (err instanceof HttpError || err.error_code >= 500) {
  // Retry
}

Fail gracefully

try {
  await ctx.reply('Result')
} catch {
  await ctx.reply('Sorry, something went wrong')
}

Proper error handling makes your bot robust and reliable!

Core API

Convenience APIs

Types

Error Handling

Error Handling

BotError<C>

Properties

When it occurs

Handling BotError

Accessing context from errors

Example: Retry on error

GrammyError

Properties

Common Error Codes

When it occurs

Example: Handling specific errors

Example: Handling message deletion

Example: Handling bot blocking

ResponseParameters

HttpError

Properties

When it occurs

Example: Retry on network failure

Error Handling Patterns

Global Error Handler

Local Error Handling

Error Boundaries

Ignore Specific Errors

Custom Error Classes

Error Logging

Best Practices

Build docs developers (and LLMs) love

Core API

Convenience APIs

Types

Error Handling

​BotError<C>

​Properties

​When it occurs

​Handling BotError

​Accessing context from errors

​Example: Retry on error

​GrammyError

​Properties

​Common Error Codes

​When it occurs

​Example: Handling specific errors

​Example: Handling message deletion

​Example: Handling bot blocking

​ResponseParameters

​HttpError

​Properties

​When it occurs

​Example: Retry on network failure

​Error Handling Patterns

​Global Error Handler

​Local Error Handling

​Error Boundaries

​Ignore Specific Errors

​Custom Error Classes

​Error Logging

​Best Practices

Build docs developers (and LLMs) love

BotError<C>

Properties

When it occurs

Handling BotError

Accessing context from errors

Example: Retry on error

GrammyError

Properties

Common Error Codes

When it occurs

Example: Handling specific errors

Example: Handling message deletion

Example: Handling bot blocking

ResponseParameters

HttpError

Properties

When it occurs

Example: Retry on network failure

Error Handling Patterns

Global Error Handler

Local Error Handling

Error Boundaries

Ignore Specific Errors

Custom Error Classes

Error Logging

Best Practices