diff --git a/design/INDEX.md b/design/INDEX.md
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--- a/design/INDEX.md
+++ b/design/INDEX.md
@@ -1,5 +1,21 @@
 # AILang Design — Index
 
+> **Status: RETIRED (paused) as of 2026-06-03.** No further compiler or
+> language work is planned for now. The project's differentiating thesis —
+> that a language purpose-built for LLM authorship makes LLM authors
+> measurably more correct — did not find empirical support in the project's
+> own cross-model measurements: the optimal surface is model-relative (a
+> redundant-structure crutch helps a small model and *hurts* a frontier one),
+> a compiler-in-the-loop is not an equaliser, and for a frontier author AILang
+> is at best neutral versus a familiar language given a scan. The
+> hallucination-robustness pillar (content-addressed symbols) was separately
+> falsified and removed (#66). Evidence corpus:
+> `experiments/2026-05-12-cross-model-authoring/format-findings.md`. The
+> language design below remains a sound small ML/effect language and the
+> measurement harness remains the project's most durable output; the git
+> history and the `design/` ledger stand as the record. This is a pause, not
+> a deletion — reversible if a new framing makes the remaining work worthwhile.
+
 The sole addressable entry point. Every contract and model is
 reached from here. A contract is a prescriptive, test-linked
 invariant; a model is a whitepaper narrative. `ratifying-test` names