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Dominance said a phase cannot end unless X. A port also needs "once X holds, it must end", and that is a must-reach set: nodes from which END_PHASE is unavoidable, as a least fixpoint where n qualifies when it has successors and ALL of them qualify. The conservatism is deliberate and is the honest answer: a loop never enters the set, because a poll loop reaches its exit only if the polled predicate eventually becomes true, which is a liveness property rather than a graph one. A dominating condition is a TRIGGER when the successor it takes on being satisfied lies in that set. Over all 28 stages: 732 dominating conditions, 234 triggers (31.97%). isl_report.py phase-guards now tags every line precond / TRIGGER. The split lands where it should. Stage 02's phase-1 objective exit is six preconditions -- player alive, TCN004 destroyed, t <= 210, ADT102/ADT107/ADT113 destroyed -- and exactly ONE trigger: hp_pct_test(ADN101, 0) != 1. Destroying ADN101 is what fires the phase. That is a sentence a port can implement. Per-exit distribution over 172 reachable exits: 89 have exactly one trigger, 42 have none, 41 have several. The 42 with none are not a failure -- they are the exits no branch fires; Stage 02's 0x006260 ends on read_freg(0) < 1200, a timeout, and time passing is not a property of the graph, so declining to call it a trigger is correct. Recorded as a heuristic rather than a rule: "the first trigger is the point of no return" holds for 33 of the 41 multi-trigger exits, with 8 counterexamples where a precondition appears after a trigger. The likely cause is that the listing is ordered by file offset, which is not execution order -- coroutines and jumps let a lower offset run later. Not asserted. calls, phase-ends and conditions all regenerate byte-identical; the two phase-guards artefacts change only by gaining the tags.