wire name	revit.cancel
C# constant	BridgeMessage.Names.Cancel
kind	command
direction	panel-to-addin
runs on	revit-ui-thread-inline

Carries the revit. prefix because it is ABOUT Revit-side work, but is answered INLINE in the WebView callback and never enqueued — a queued cancel would run after the operation it was meant to stop, because that operation is holding the external event. That callback is itself on Revit’s UI thread, so a cancel can only ARRIVE while that thread is free: it cannot interrupt a survey.

What these words mean

kind. query = changes nothing a later message can observe. command = it does. event = the add-in pushes it, unasked. DECLARED per message, never derived from the prefix — the prefix is a THREAD decision.

runs on. revit-api-thread = inside the ExternalEvent dispatcher (ADR-4). revit-ui-thread-inline = on Revit’s main loop but OUTSIDE the dispatcher, straight from a callback Revit invokes. beside-the-dispatcher = off Revit’s main loop, on a thread-pool thread (ADR-11, ADR-31).

Source of truth: BuildPlan.Core/Bridge/BridgeMessage.cs in the plugin repository.