03 — The model

Summary

The computation, pure and testable: facts prune, controls reshape, every path is enumerated, the weakest link labels the capability, the weakest route wins across surfaces, and the dashboard gets a sentence rather than a histogram — the chokepoint: one node is the weakest link on N of M paths, which says the visitor has one problem rather than eleven. The three documented traps: escalation-existence must be tracked across all paths, not on the winner (the root already wins every direct-path contest, so winner-only tracking hid every escalation the library had); dropping a node must walk its ancestors; and a tree without benign capabilities manufactures false shortfalls that a test suite can happily assert.

Key concepts

• The weakest link on the path — a path is only as bounded as its least-enforced node — the file's one idea
• The chokepoint sentence — on local surfaces the tier histogram reads all-none and tells nobody anything
• Escalation tracked across paths — the shipped bug: recording it on the winning path alone masked all of them

Key ideas

• The model's entire output vocabulary is: reachable, tier, evidence, path, excess, shortfall, chokepoint, closes, strengthens.
• Every bug in this document's history has a test that fails if it comes back.
• controlEffect runs the whole pipeline twice and diffs — the most expensive call in the file, and still instant at library scale.

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