Show HN: Lean4 proof that SSOT requires definition-time hooks and introspection https://ift.tt/k9b23Mv

Show HN: Lean4 proof that SSOT requires definition-time hooks and introspection I formalized the Single Source of Truth (SSOT) principle in Lean 4 (~2.1k LOC, zero sorry) and proved two core results: Structural SSOT is achievable only when a language provides definition-time hooks and runtime introspection. Macros/codegen (before definition) and reflection (after definition) are insufficient. These requirements are derived, not chosen: because structural facts are fixed at definition, derivation must occur at definition time and be introspectable to verify DOF = 1. Would appreciate review, critique, or independent checking of the Lean scripts. https://ift.tt/wLHDhd5 January 8, 2026 at 02:15AM