diff --git a/test/vitest/vitest.shared.config.ts b/test/vitest/vitest.shared.config.ts
index 50ca3c96e600..1d93b0a0e9cb 100644
--- a/test/vitest/vitest.shared.config.ts
+++ b/test/vitest/vitest.shared.config.ts
@@ -160,6 +160,21 @@ export const sharedVitestConfig = {
   envDir: false as const,
   resolve: {
     alias: [
+      {
+        // Route bare `zod` through a runtime shim (same pattern as the
+        // discord-api-types shims below): zod's own entry re-exports `z` as a
+        // namespace binding, which Bun's linker drops under Vitest's loader
+        // hooks. The shim exposes the identical surface on Node and Bun.
+        find: /^zod$/u,
+        replacement: path.join(repoRoot, "test", "vitest", "zod-runtime.ts"),
+      },
+      {
+        // Bun substitutes its built-in fetch shim for bare `undici`, whose
+        // MockAgent is a non-functional stub; pin the real package so
+        // mock-http interception works. Node resolves to this file anyway.
+        find: /^undici$/u,
+        replacement: path.join(repoRoot, "node_modules", "undici", "index.js"),
+      },
       {
         find: "discord-api-types/v10",
         replacement: path.join(repoRoot, "test", "vitest", "discord-api-types-v10-runtime.ts"),
diff --git a/test/vitest/zod-runtime.ts b/test/vitest/zod-runtime.ts
new file mode 100644
index 000000000000..4a354a0f8e5e
--- /dev/null
+++ b/test/vitest/zod-runtime.ts
@@ -0,0 +1,10 @@
+// Test-only zod entry: zod's real index.js re-exports the `z` namespace via
+// `import * as z; export { z }`, which Bun's module linker drops when Vitest's
+// loader hooks are active (named `z` arrives undefined). Re-exporting through a
+// const binding links correctly on both Node and Bun; the exposed surface is
+// identical to `zod` (zod/v4 is the same classic API), so Node is unchanged.
+import * as zNamespace from "zod/v4";
+
+export * from "zod/v4";
+export const z = zNamespace;
+export default zNamespace;