What is checkpoint design?

Checkpoint design is a concept in personal epistemology: Build verification points into workflows to catch errors before they propagate downstream.

Example: A product team ships a feature that breaks the checkout page. The bug was introduced during the design phase — a button was labeled "Submit" but wired to a cancellation endpoint. The design was reviewed by no one. The code was reviewed by a developer who didn't compare the implementation to the spec. QA tested only the happy path. Staging was skipped because of a deadline. Four checkpoints existed on paper; none of them caught the error because none of them asked the right verification question at the right moment. A single design review checkpoint — "Does every interactive element match its intended behavior in the spec?" — would have caught the bug six weeks before it reached a customer.

This concept is part of Phase 41 (Workflow Design) in the How to Think curriculum, which builds the epistemic infrastructure for workflow design.