A fool-proof plan is a stack of decisions made early
“Fool-proof” doesn't mean nothing goes wrong. It means the plan already knows what to do when things go wrong — because the person who decided was warm, fed, and looking at a forecast, not standing in the wind arguing with a map. The whole method is one move: take every decision the trip will demand, and make as many as possible before you leave.
Step 1 — Inventory the decisions
Walk the trip cairn by cairn and ask, at each one and each leg: what could force a choice here? Permits are decisions (apply, backup, walk-up?). Weather is decisions (go, hold, reroute?). The group is decisions (split, slow down, cut the day?). Water, daylight, road closures, shuttle times. Write them all down. A six-day trip usually yields ten or fifteen; most trips run on none of them written anywhere.
Step 2 — Sort them into the three buckets
Every decision on the list resolves into one of the three primitives.
What remains after sorting is the trip's true residual risk — the handful of judgment calls only the mountain can referee. On a well-planned trip that list is short enough to hold in your head, which is exactly where you want it when the wind picks up.
Step 3 — Stress the plan on paper
Now break your own trip, in comfort. Lose the lottery — does Plan B stand on its own? Add three hours to the longest day — does anyone summit in the dark? Put a 40% thunderstorm on the pass day — is the hold-camp legal, watered, and pleasant? Take out the strongest member — do the route budgets survive? Each failure you find is a decision you get to make early instead of late. This is also the point of the shareable itinerary: a plan a stranger can read is a plan that has been forced to be explicit.
In the field: execute, don't re-plan
The payoff comes at the divisions. When the moment arrives, you don't deliberate — you check the condition and take the branch. It's 8am, the buildup is over the crest, the plan says under 30% or hold: you hold, and nobody argues, because past-you already won that argument with better information. The plan absorbs the surprise; the group just walks.
And when something truly outside the plan happens — it will, eventually — you meet it with your whole judgment available, because it isn't competing with fourteen deferred decisions you should have made in February. That's the entire philosophy. Cairns settle where. Routes settle when. Divisions settle what-if. The mountain gets only the questions it insists on.