A teammate's offline channel hides its history and disables Send without a reason #607

A teammate's channel whose Mac is offline shows none of its history and disables Send without saying why. The project picker doesn't mark the project as offline.

What was seen

With Sam's helper stopped, A opened b-chan:

• "nate16-1 is offline — b-chan runs on that Mac. Its chat opens here when the Mac is back." Nothing else: "I can't read any of the earlier history; Sam's 1:16 message and my messages from 1:24–1:29 are all gone from view." Details lost Model, Tokens and Cost.
• The composer still offered Chat/Ace, and in Ace mode it pre-filled an "ace" chip while agent access was unknown. A typed "are you offline?": "the Send arrow stays grey and disabled. Enter does nothing, and nothing explains why: no tooltip, no toast, no 'will send when back'." Nothing was queued.
• The project picker showed "b-sandbox · nate16-1" with no offline mark, while People, the sidebar ("samechocolixir · Offline") and the Dashboard row ("Offline: nate16-1 is unreachable") all agreed.
• Nothing said Sam had gone offline, and nothing on either side recorded the outage afterwards.

Steps

1. Open a teammate's channel and read it, then the teammate's Mac goes offline.
2. Open the channel again and try to post.

Expected: the history you've already read stays readable, and the composer says why it can't send or queues the message for when the Mac is back. The picker marks the project offline.

Map: ^104. Related: #58.

Found in the 2026-10-22 two-Mac pair study.