The /focus command now requires the fullscreen renderer (TUI mode) and provides clear guidance on how to enable it. If viewMode is set to "focus" in settings.json, the command warns that it must be removed there before toggling. The viewMode setting now validates against an enum: ["default", "verbose", "focus"].
Evidence
Focus view requirements (search for "Focus view needs the fullscreen renderer")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeFixed /focus showing "Unknown command" when the fullscreen renderer is off — now explains how to enable it
