From 136adce9ff02145f248f2f4cb1ebd91f90db6787 Mon Sep 17 00:00:00 2001
From: Meta Vens <rwvens@hotmail.com>
Date: Tue, 29 Sep 2026 04:21:59 +0200
Subject: [PATCH] Prove TypeScript, Python and Rust refuse the C#-written
 variant store by name

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---
 packages/cultcache-py/tests/test_cultcache.py |  6 ++++++
 packages/cultcache-rs/src/lib.rs              | 10 ++++++++++
 packages/cultcache-ts/test/cult-cache.test.ts |  7 +++++++
 3 files changed, 23 insertions(+)

diff --git a/packages/cultcache-py/tests/test_cultcache.py b/packages/cultcache-py/tests/test_cultcache.py
index b4168690..6001c905 100644
--- a/packages/cultcache-py/tests/test_cultcache.py
+++ b/packages/cultcache-py/tests/test_cultcache.py
@@ -829,6 +829,12 @@ class CultCacheTests(unittest.TestCase):
         message = str(caught.exception)
         self.assertTrue("cultcache.store.v2" in message or "item:anvil-big" in message, message)
 
+    def test_single_file_refuses_the_csharp_written_variant_store_by_version_or_record(self) -> None:
+        with self.assertRaises(ValueError) as caught:
+            self._pull_vector("../document-variants-c1/variant-store.msgpack")
+        message = str(caught.exception)
+        self.assertTrue("cultcache.store.v2" in message or "laser-big" in message, message)
+
     def test_v1_store_written_at_the_base_commit_still_reads_byte_for_byte(self) -> None:
         envelopes = self._pull_vector("v1-base.msgpack")
         self.assertEqual([(e.key, e.type) for e in envelopes], [("alpha", "vectors.item"), ("beta", "vectors.item")])
diff --git a/packages/cultcache-rs/src/lib.rs b/packages/cultcache-rs/src/lib.rs
index e48ebad8..c9a7d282 100644
--- a/packages/cultcache-rs/src/lib.rs
+++ b/packages/cultcache-rs/src/lib.rs
@@ -4679,6 +4679,16 @@ mod tests {
         );
     }
 
+    // The store the C# runtime wrote through its own variant API (tests/vectors/document-variants-c1).
+    #[test]
+    fn single_file_refuses_the_csharp_written_variant_store_by_version_or_record() {
+        let message = refusal("../document-variants-c1/variant-store.msgpack");
+        assert!(
+            message.contains("cultcache.store.v2") || message.contains("laser-big"),
+            "{message}"
+        );
+    }
+
     #[test]
     fn v1_store_written_at_the_base_commit_still_reads_byte_for_byte() -> Result<()> {
         let envelopes = pull_vector("v1-base.msgpack")?;
diff --git a/packages/cultcache-ts/test/cult-cache.test.ts b/packages/cultcache-ts/test/cult-cache.test.ts
index a743ba00..8753af47 100644
--- a/packages/cultcache-ts/test/cult-cache.test.ts
+++ b/packages/cultcache-ts/test/cult-cache.test.ts
@@ -1443,6 +1443,13 @@ test("SingleFileMessagePackBackingStore refuses a variant store by version or re
   );
 });
 
+test("SingleFileMessagePackBackingStore refuses the C#-written variant store by version or record", async () => {
+  await assert.rejects(
+    () => pullVector("../document-variants-c1/variant-store.msgpack"),
+    (error: Error) => error.message.includes("cultcache.store.v2") || error.message.includes("laser-big"),
+  );
+});
+
 test("CultCache inspector refuses the same vectors by name", async () => {
   const inspect = async (name: string) => inspectCultCacheBytes(name, await readFile(join(variantVectors, name)));
   await assert.rejects(() => inspect("unknown-header.msgpack"), /cultcache\.store\.v9/u);