diff --git a/src/plugin-sdk/index.bundle.test.ts b/src/plugin-sdk/index.bundle.test.ts
index c79abc4b7a0..f364aac1d30 100644
--- a/src/plugin-sdk/index.bundle.test.ts
+++ b/src/plugin-sdk/index.bundle.test.ts
@@ -26,6 +26,12 @@ describe("plugin-sdk bundled exports", () => {
       clean: false,
       config: false,
       dts: false,
+      deps: {
+        // Match the production host build contract: Matrix SDK packages stay
+        // external so the heavy runtime surface does not fold multiple
+        // matrix-js-sdk entrypoints into one bundle artifact.
+        neverBundle: ["@lancedb/lancedb", "@matrix-org/matrix-sdk-crypto-nodejs", "matrix-js-sdk"],
+      },
       // Full plugin-sdk coverage belongs to `pnpm build`, package contract
       // guardrails, and `subpaths.test.ts`. This file only keeps the expensive
       // bundler path honest across representative entrypoint families.
diff --git a/tsdown.config.ts b/tsdown.config.ts
index 0885591c2e5..70e6bf41c40 100644
--- a/tsdown.config.ts
+++ b/tsdown.config.ts
@@ -155,7 +155,7 @@ export default defineConfig([
     // and bundled hooks in one graph so runtime singletons are emitted once.
     entry: buildUnifiedDistEntries(),
     deps: {
-      neverBundle: ["@lancedb/lancedb"],
+      neverBundle: ["@lancedb/lancedb", "@matrix-org/matrix-sdk-crypto-nodejs", "matrix-js-sdk"],
     },
   }),
 ]);