diff --git a/runtime/README.md b/runtime/README.md
index 1e68cbe..f221d14 100644
--- a/runtime/README.md
+++ b/runtime/README.md
@@ -1,4 +1,11 @@
-# interscript-ml (Python runtime)
+# interscript-ml (Python runtime) — SUPERSEDED by `secryst`
+
+> **Deprecated.** The canonical Python crystal is
+> [`secryst`](https://pypi.org/project/secryst/) (same code, same
+> IMF v1 contract, same SECRYST_INDEX/SECRYST_CACHE env vars) —
+> `pip install secryst` instead. This package remains published for
+> provenance; `runtime/` in this repo is the frozen origin of the
+> crystal family (golden-owner history in the secryst-py README).
 
 The reference Python runtime for **IMF v1** model zips — the phonological
 layer of Interscript. The Ruby (secryst gem) and TypeScript
diff --git a/runtime/pyproject.toml b/runtime/pyproject.toml
index ed908e0..ff66ffb 100644
--- a/runtime/pyproject.toml
+++ b/runtime/pyproject.toml
@@ -4,13 +4,14 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "interscript-ml"
-version = "0.1.0"
-description = "Python runtime for Interscript Model Format (IMF v1) — the phonological layer of Interscript"
+version = "0.1.2"
+description = "DEPRECATED — superseded by the 'secryst' package; Python runtime for Interscript Model Format (IMF v1)"
 readme = "README.md"
 license = { text = "BSD-3-Clause" }
 requires-python = ">=3.10"
 authors = [{ name = "Interscript Project" }]
-keywords = ["transliteration", "diacritization", "g2p", "onnx", "byt5"]
+classifiers = ["Development Status :: 7 - Inactive"]
+keywords = ["transliteration", "diacritization", "g2p", "onnx", "byt5", "deprecated"]
 
 dependencies = [
   "numpy>=1.26",
diff --git a/runtime/src/interscript_ml/registry.py b/runtime/src/interscript_ml/registry.py
index aae6c28..aede061 100644
--- a/runtime/src/interscript_ml/registry.py
+++ b/runtime/src/interscript_ml/registry.py
@@ -19,7 +19,7 @@
 import yaml
 
 DEFAULT_INDEX_URL = (
-    "https://raw.githubusercontent.com/interscript/interscript-ml/main/models.yaml"
+    "https://github.com/interscript/interscript-ml/releases/download/index-v6/models-index.yaml"
 )
 ENV_INDEX = "SECRYST_INDEX"
 ENV_CACHE = "SECRYST_CACHE"
diff --git a/runtime/tests/test_registry.py b/runtime/tests/test_registry.py
index 4dd61d8..e2c0c2e 100644
--- a/runtime/tests/test_registry.py
+++ b/runtime/tests/test_registry.py
@@ -165,3 +165,16 @@ def test_resolve_parts_rejects_corrupt_part(tmp_path: Path) -> None:
             resolve("tiny-1.0", index_url=str(index_path))
     finally:
         os.environ.pop("SECRYST_CACHE", None)
+
+
+def test_default_index_url_pins_current_release() -> None:
+    # exact pin: raw.githubusercontent is NEVER a data channel (the
+    # contract is GitHub Releases + sha256 sidecar). Bump this test
+    # WITH the registry constant, never ahead of it.
+    from interscript_ml.registry import DEFAULT_INDEX_URL
+
+    assert DEFAULT_INDEX_URL == (
+        "https://github.com/interscript/interscript-ml"
+        "/releases/download/index-v6/models-index.yaml"
+    )
+    assert "raw.githubusercontent" not in DEFAULT_INDEX_URL