CDIP v1.1 —P20-IND v0.1 Recursive Type Universe (IND-ADT Fragment) A Conservative, Auditable Inductive Extension Compatible with P18-revA and P19-WCCC v0.2

This document opens the CDIP v1.1 exploration frontier P20-RTU by introducing an auditable Recursive Type Universe restricted to an inductive algebraic data type fragment (IND-ADT). The goal is to admit controlled self-reference in type formation while pre- serving: (i) determinism of adjudication, (ii) P18-revA closed-world evidence typing and anti-laundering, and (iii) P19-WCCC v0.2 external anchoring discipline (human or proof assistant + DOI). We provide a fully ordered gate sequence (earliest-fail), reason-code namespace P20.*, and machine-checkable policy schema sketches.