You want one of your Claude Code sessions to tell another that a migration has landed, and you are also wondering whether that same mechanism could hand the second session the whole discussion you have been having in the first. What does a message from one session to another carry, and what does moving an entire conversation take instead?

The principle — a message is text, and text is all of it.

Why the key is correct — both halves are on the same page. A message is a piece of text one Claude writes to another, never conversation history or files. And the alternative is named: to move a whole conversation or its context, resume the session instead. So telling the other session that the migration landed is what the channel is for; handing it your discussion is not.

Why the others are wrong — context does not ride along, so nothing is picked up where you left it. A history written into a message is words about a conversation, not the conversation. And this channel is for independent sessions you steer yourself.

Remember this — text crosses between sessions and context does not. A conversation moves only by resuming it.

Sources — Anthropic's documentation on cross-session messaging.