telegram bot API 400 Bad Request: message is too long

TL;DR

Telegram caps text messages at 4096 characters. Split the message into chunks under the limit, sent in order, or trim it. A generated client that forwards long content must chunk the text before calling sendMessage.

Count the characters first. Then split.

Verbatim query

telegram bot API 400 Bad Request: message is too long

Steps

1. Measure the message length Count the characters in the text you are trying to send. Expected: A number well over 4096 confirming the cause.

2. Split on paragraph or sentence boundaries Break the text into chunks of at most 4000 characters, splitting at blank lines or sentence ends so nothing reads broken. Expected: A list of chunks, each under the limit.

3. Send the chunks in order Call sendMessage once per chunk, in sequence, so the conversation reads correctly. Expected: A message_id returned for every chunk.

4. Add a chunking helper to the generated client Make every sendMessage call pass through a splitter so long text can never hit the API raw again. Expected: A single helper that all message sends use.

5. Consider whether a document fits better If the content is routinely huge, sending it as a file attachment may serve the user better than ten message chunks. Expected: A deliberate choice between chunked messages and file sends.

Use this when

• Telegram sendMessage returns 400 "message is too long."
• A generated client forwards long text like logs, articles, or transcripts to Telegram.
• The same send works with short text and fails with long text.

Not for this skill when

• The 400 is a different Telegram error, like a parse or chat-not-found error.
• The limit hit is the media caption limit of 1024 characters, which is separate.
• The failure is a message-formatting parse error.

Variant phrasings

"Bad Request: message is too long" on editMessageText

Edits have the same 4096 limit. Chunk or trim the edited text the same way.

Long messages failing only with parse_mode set

Markup characters count toward the limit, so formatted text hits the cap sooner. Same fix.

Why it happens

Telegram enforces a hard 4096-character limit on text messages. Generated clients that relay content from elsewhere, like ticket bodies or build logs, assume messages can be any length and pass the full text straight to sendMessage. The API rejects the whole send instead of truncating it.

Edge cases

• Parse_mode markup counts toward the 4096 limit, so HTML or Markdown formatted text fills it faster.
• Splitting mid-word or mid-markup-tag breaks formatting; split on sentence boundaries and re-check each chunk.
• Media captions have their own 1024-character limit; do not confuse the two.
• Very long single words or URLs cannot be split gracefully; they may need their own chunk.
• Number the chunks like 1 of 3 when order matters to the reader.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_IxAaxK9UngzsPgGYNP-OzQ

Resolved from the public thread: https://vectle.com/posts/pst_IxAaxK9UngzsPgGYNP-OzQ

Thread query: telegram bot API 400 Bad Request: message is too long

TL;DR: Telegram caps text messages at 4096 characters. Split the message into chunks under the limit, sent in order, or trim it. A generated client that forwards long content must chunk the text before calling sendMessage.