A briefing has a short version and a note. They sit near each other. Assistants love to copy one into the other, or to write a "warm" note that is just the TL;DR with a greeting stapled on. That collapse is how a summary — which may be the model's verdict — gets read as the sentence you signed.
They are different jobs. Treat them as different objects.
The TL;DR is for the person who will not open the rest
Some readers will act on the short version alone. That is allowed. It is why the short version has to state the conclusion and the ask, not the topic. "Vendor update" is a folder. "Pick B by Wednesday or we lose September" is a verdict.
It is also why the TL;DR is a dangerous place to be sloppy. A skimmer who trusts it will do the wrong thing if it is wrong. It should be checkable against the brief, and it should not contain a private nickname, a side comment, or a guess unmarked as a guess.
A briefing carries both parts because they serve two speeds of reading. One is not a prettier reprint of the other.
The note is the signature
The note is the line that approval is really about. Leave the draft and you approved the assistant's wording. Change it and you claimed different words. The verbatim label only applies when the wording actually differs, and only on the path the server can see.
If the note is a second TL;DR, you have signed a headline. Headlines hedge. They omit the lean. They sound like a model. The note is where you say "I will call them if you pick B," or "I am sorry this is late," or "I do not want C and I will own that." A skimmer who opens nothing else will miss that. The person who reads the note will not.
A note past the cap is refused, not trimmed. Shortening it yourself and resending would put the assistant's cut behind a label that says the words are yours.
Mixing them creates a false author
When both boxes contain the same polished paragraph, a later quote has no owner. Was that you? Was that the model summarising you? The labels cannot help if you used the note as a dump for the summary.
Direct replies have a cleaner rule: if the note already opens with the short version, the TL;DR stays empty. Repeating the sentence does not make it more true. It makes the page look like a template.
A practical split
Write the brief first. Write the TL;DR last, as a verdict a stranger could act on. Then write a note that would be incomplete as a summary and complete as a human sentence.
If you cannot tell them apart in the preview, you are not ready to confirm. Cut until the short version could travel alone, and the note could not be mistaken for anyone but you.