diff --git a/src/core/pinecone/searchable-index-conformance.test.ts b/src/core/pinecone/searchable-index-conformance.test.ts
new file mode 100644
index 0000000..a711300
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+++ b/src/core/pinecone/searchable-index-conformance.test.ts
@@ -0,0 +1,43 @@
+import { describe, it, expect } from 'vitest';
+import { Pinecone } from '@pinecone-database/pinecone';
+
+/**
+ * SDK-shape conformance guard for SearchableIndex (#220).
+ *
+ * `indexes.ts` force-casts `pc.index(...)` to `SearchableIndex` with `as unknown as`,
+ * which erases type checking, and the other tests only mock our own interface. So
+ * nothing verifies the real SDK index still provides the members the code calls. If a
+ * Pinecone SDK bump renames or removes one, it slips past the compiler and fails at
+ * runtime in production. This asserts those members exist on a real SDK index, so a
+ * drift fails here loudly instead.
+ *
+ * A compile-time assertion was tried but the SDK types the index too loosely to catch
+ * drift, so this is a runtime existence check. `pc.index()` returns a handle
+ * synchronously with no network call, so it needs no live Pinecone.
+ */
+describe('SearchableIndex SDK conformance (#220)', () => {
+  const index = new Pinecone({ apiKey: 'pc-conformance-test' }).index(
+    'conformance-test'
+  ) as unknown as Record<string, unknown>;
+
+  // Called on the top-level index: indexes.ts uses describeIndexStats() and
+  // namespace(), and search.ts uses searchRecords() on the index fallback branch.
+  it.each(['describeIndexStats', 'namespace', 'searchRecords'] as const)(
+    'the SDK index exposes %s()',
+    (method) => {
+      expect(typeof index[method]).toBe('function');
+    }
+  );
+
+  // Called on the namespace handle from index.namespace(ns): indexes.ts does
+  // namespace(ns).query(...) and search.ts does namespace(ns).searchRecords(...).
+  const namespaceHandle = (index.namespace as (name: string) => Record<string, unknown>)(
+    'conformance-test'
+  );
+  it.each(['query', 'searchRecords'] as const)(
+    'the SDK namespace handle exposes %s()',
+    (method) => {
+      expect(typeof namespaceHandle[method]).toBe('function');
+    }
+  );
+});