diff --git a/vitest.config.ts b/vitest.config.ts
index 0868870..eefa362 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -13,5 +13,13 @@ export default defineConfig({
   test: {
     include: ['tests/**/*.test.ts'],
     setupFiles: ['tests/setup.ts'],
+    coverage: {
+      // Without an explicit include, v8 coverage walks the whole project root.
+      // While the read-only reference_code/ checkout was present that pulled in
+      // ~570 of its files and diluted every percentage below.
+      provider: 'v8',
+      include: ['packages/*/src/**'],
+      exclude: ['**/vendor/**', '**/*.d.ts'],
+    },
   },
 })