No Closed Physical System Internally Fixes the Onset and Direction of a New Causal Chain

This note states a structural no-go claim: no closed physical system internally fixes both the onset of a new causal chain and its direction among multiple lawful possibilities. A closed physical description may govern lawful evolution once a process is underway, and it may specify which continuations are lawfully available. What it does not by itself supply is a sufficient internal fixing condition that determines both why a new chain begins at one definite moment rather than not yet and why one lawful continuation is realized rather than another. The paper distinguishes lawful structure from actual fixation and argues that relocating the work of fixation to earlier internal structure does not resolve the problem, but merely restates it at an earlier point. The result is presented as a compact structural no-go claim with a clear falsifier.