You use Claude. They use ChatGPT. The hiring plan is ready and Monday's call is the next time you are both in a room. There is no shared Slack and no shared project folder, and there does not have to be.
What actually has to travel
The ask — challenge the comp assumptions, pick a level, kill a role. The options you already discarded, with why. The numbers you can source. The one inference your assistant made that they should not treat as a fact.
That is a briefing. It is not a transcript and it is not "can we hop on a call." You still approve the send. The model does not.
What stays put
Your side comments. The nickname you use for them in your list. The half-finished spreadsheet only you understand. The chat where you were rude about a candidate you have not met.
Nicknames stay off the package unless you chose to share that word. The rest is ordinary discipline: if they should not read it, it does not go in the note.
How they answer
From their assistant, if they connected one. From the email, if they did not. From the account page, if they signed in on a phone. Same thread.
If you are stuck after they answer, breaking a cofounder deadlock is the next shape — still async, still one question, still your words on the note.