Adding an inline button with the ability to open a chat with a user knowing their username

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Summary

A developer attempted to create an inline button in a Telegram bot that would open a direct chat with a user using only their username. The implementation used a URL button pointing to https://t.me/Username. However, the button click resulted in an error message stating the user does not exist, despite the username being valid.

The core issue was a misunderstanding of Telegram’s deep-linking syntax and the difference between a bot token, a bot username, and a user username. The developer likely used a t.me link that conflicted with the bot’s own handling of usernames or formatted the URL incorrectly, causing Telegram to interpret the request as invalid.

Root Cause

The root cause lies in the specific syntax required for t.me links and how Telegram handles them in the context of Inline Keyboard Buttons.

  1. Incorrect URL Pattern: The developer used url="https://t.me/Username starting with @". This is syntactically ambiguous. While standard web links often ignore the @ symbol, Telegram’s internal routing for t.me handles the @ prefix specifically. If the link pointed to the bot’s own username (which usually starts with @), the bot cannot “open a chat with itself” in the way a user chats with a user, leading to the “user does not exist” error.
  2. Deep Linking vs. Standard Links: Telegram supports specific deep linking parameters (e.g., https://t.me/username?start=parameter). However, to simply open a chat, the syntax must be exact. The error typically arises when the username provided in the URL does not resolve to an active user or bot account accessible via that specific link type.
  3. Bot Token Confusion: In some cases, developers confuse the Bot Token (e.g., 1234567890:ABC...) with the Bot Username (e.g., @my_bot). A token cannot be used in a t.me URL.

Why This Happens in Real Systems

This issue is common in distributed messaging systems where identifiers and human-readable handles are treated differently.

  • Namespace Collision: Telegram manages namespaces for users, bots, groups, and channels. A t.me link is a global routing key. If a bot attempts to link to a resource that falls outside its allowed routing permissions (or uses a malformed route), the server returns a generic “user not found” error to prevent scraping or enumeration attacks.
  • Client-Side Interpretation: The Telegram client (iOS/Android/Desktop) parses the url field of an inline button. If the URL is not a valid deep link or points to a resource the client cannot resolve (e.g., an internal bot token), it fails gracefully with a misleading error message.
  • Lack of Immediate Feedback: Unlike API calls which return specific JSON errors (e.g., 400: CHAT_NOT_FOUND), a URL button click is handled by the client application, which translates the underlying routing failure into a user-friendly (but technically vague) toast message.

Real-World Impact

  • Broken User Experience: Users clicking the button are met with an error instead of the intended chat, creating friction and reducing trust in the bot’s functionality.
  • Development Friction: The error message “user does not exist” is a false negative. It sends developers debugging down the wrong path—checking database records or user status—when the issue is purely syntactical in the URL construction.
  • Reduced Engagement: If the primary Call to Action (CTA) is to start a chat, a broken button directly correlates to lost conversions or support requests.

Example or Code

The solution requires using the correct URL format. To open a chat with a user by their username (which must start with @), the URL should strictly be https://t.me/USERNAME.

Here is the correct Python implementation using telebot:

import telebot

# Initialize bot with your token
API_TOKEN = 'YOUR_BOT_TOKEN'
bot = telebot.TeleBot(API_TOKEN)

@bot.message_handler(commands=['start'])
def send_welcome(message):
    # Define the target username (Must include the @ symbol)
    target_username = "@target_user_name"

    # Create the inline keyboard button
    # The URL must be exactly "https://t.me/USERNAME" (without https:// if preferred, but full URL is safer)
    # Note: The username in the URL should NOT include the @ symbol usually, 
    # but the link text can. 
    # CORRECT SYNTAX: https://t.me/USERNAME (where USERNAME is the handle without @)

    username_handle = "target_user_name" # The actual handle without the @

    keyboard = telebot.types.InlineKeyboardMarkup()
    url_button = telebot.types.InlineKeyboardButton(
        text="Open Chat", 
        url=f"https://t.me/{username_handle}"
    )
    keyboard.add(url_button)

    bot.send_message(message.chat.id, "Click the button to chat:", reply_markup=keyboard)

if __name__ == "__main__":
    bot.infinity_polling()

Note: If you are trying to open a chat with the Bot itself, you must use the bot’s own username in the URL (e.g., https://t.me/my_bot_username). Using a user token or a random string will fail.

How Senior Engineers Fix It

Senior engineers approach this by isolating the routing mechanism from the business logic.

  1. Validate the Identifier: They verify that the target username is a valid, active Telegram handle. They ensure there is no whitespace or hidden characters in the string variable.
  2. Use Canonical URL Format: They strictly adhere to the https://t.me/{username} format. They avoid adding @ inside the URL path if it is not required by the Telegram API (usually the URL path is the raw username, while the display text can contain the @).
  3. Implement Fallbacks: They often add a fallback mechanism. If the username is invalid, they disable the button or change the text to “User unavailable” rather than relying on the API to handle the error gracefully.
  4. Debug via API: Instead of clicking the button, they use the Telegram API getChat method with the username to confirm the chat exists programmatically before generating the button.

Why Juniors Miss It

Juniors often struggle with this due to a lack of understanding of Telegram’s specific URL routing protocols.

  • String Manipulation: They often mishandle string formatting (e.g., including/excluding the @ symbol incorrectly). They might pass the entire string @username into the URL path, resulting in https://t.me/%40username, which Telegram may interpret differently than intended.
  • Confusing Chat IDs with Usernames: Juniors are used to using numerical chat_id integers for sending messages. When switching to usernames for public addressing, they fail to realize that usernames are case-insensitive and must be URL-safe.
  • Assuming API Magic: They assume telebot or the API will automatically “fix” the URL or convert the username to a link, not realizing that the url parameter is treated as a raw string that the Telegram client navigates to directly.