Playbook Boundary Conditions: the Devil's-Advocate Substrate and the Prototype's Edge

Joint answer to two #oq/now items about where AI-native playbook prescriptions stop being general. (1) The founder's devil's-advocate prescription interacts with character training complementarily, not conflictingly: the prompted moves are framing-compliance tasks that work on any instruction-follower (asking for the competitor's best case never requires disagreeing with the founder), while character training supplies the unprompted honesty the prompts can't manufacture — so the technique is model-portable but its safety net is Claude-specific, and the residual risk (framing bias *within* the assigned adversarial task) is exactly the part neither layer covers. (2) Prototype-over-PRD's breakdown boundary is not backend-vs-frontend but observable-surface-vs-invariant: the corpus already holds a domain-matched artifact for each spec job (three PRs, tracer-bullet slice, ten evals, design_system.html), so what breaks at the backend is the clickable prototype, not the artifact-over-document principle; the PRD survives where no cheap artifact's surface covers the risk — cross-cutting invariants and cross-team coordination. Both answers have the same shape: every prescription has a substrate; know the substrate, know the boundary