Terminal on a teammate's channel opens a blank pane instead of saying it can't #629

On a teammate's channel, the New tab menu offers Terminal, and choosing it opens a blank terminal that never says it can't open.

Where

A teammate's channel → + (New tab) → Terminal.

What was seen

Both testers, on each other's channels: the menu lists "Chat / Diff / Terminal" with Terminal enabled. It opens a "Terminal" tab with a blank pane, a focused "Terminal input" field and a small corner chip, "Terminals open on the channel's host". No prompt, no error, nothing after 10 s. Both read it as an offer that hung, not a refusal (confusion 3 and 2). On their own channel the same steps give a working prompt.

Expected: until teammates can reach terminals (#11), Terminal is disabled or explained in the New tab menu for a teammate's channel, and never opens an empty, focused pane. Code: apps/host/src/gateway.ts:499, apps/host/src/gateway.ts:823.

Map: ^779.

Found in the 2026-10-22 two-Mac pair study on Canary 0.0.53.88.