diff --git a/packages/analytics/vitest.config.ts b/packages/analytics/vitest.config.ts
index 3342336..3f43bfb 100644
--- a/packages/analytics/vitest.config.ts
+++ b/packages/analytics/vitest.config.ts
@@ -10,5 +10,11 @@ export default defineConfig({
 		// plugin-test suite.
 		testTimeout: 30_000,
 		hookTimeout: 30_000,
+		// plugin-test 0.2 builds the plugin into this package's dist/ once
+		// per test file and reads dist/manifest.json back. Files run in
+		// parallel rewrite that file while others read it, and a reader that
+		// gets it half-written fails the whole file with "Unexpected end of
+		// JSON input".
+		fileParallelism: false,
 	},
 });