When an agent's script committed a transaction that hit a Revit warning or error, Revit opened its failure dialog modally inside Commit(); the MCP call hung until the 60 s timeout with nothing returned and Revit stayed stuck until a person clicked. When the error was cancelled in time, the agent got only 'Expected Committed, received RolledBack', never the reason. The fix rolls errors back with failure text and element IDs returned to the agent.