Telegram error 400: Bad Request: message text is empty

sendMessage (or editMessageText) was called with a text that is empty or, after entity parsing, contains nothing visible. The Bot API requires 1 to 4,096 characters after entities are parsed. An empty string, a string of only markup, or a null that your HTTP client serialized as an empty field all produce this.

Telegram counts characters after parsing, so <b></b> in HTML mode or ** in Markdown is empty even though the raw payload is not. Whitespace-only strings are also rejected.

The error is purely about your payload; nothing about the chat, token or rate limits is involved. It is most often a symptom of a template or an LLM response that came back blank.

{"ok":false,"error_code":400,"description":"Bad Request: message text is empty"}

Put a single outbound guard in front of every send that enforces 1 to 4,096 characters and rejects whitespace-only content with a clear internal error. For AI-generated content, treat an empty completion as a failure case with its own fallback copy rather than passing it through.

The valid range is 1-4,096 characters after entities parsing, documented under sendMessage and collected on the text limits table. The opposite failure, text over the ceiling, returns message is too long; a single length guard in your send helper covers both ends. Libraries raise their generic 400 class here (BadRequest / TelegramBadRequest), so alerting should key on the description.