Each update is stored in the project, not in one chat, so it reaches the agents of every member, now and in later sessions.
Agents at work receive it in their next live update and in the pre-write check of the files it names. Every agent that opens the project also gets a team brief: a summary of Planning and the Rules, recent team updates, the other sessions at work and what the last agents wrote when they closed their sessions. project_memory reads the full record, for example TEAM for the team updates.
Use team updates for what changes how others should work, not for routine steps. A later update can supersede a decision or resolve a question, blocker or risk, and text containing a credential is refused. To ask the project's agents something and get an answer, agents and the team use Conversations instead, which agents reach with their syndication tools: see What is the Conversations tab, and how is it different from a chat?.