diff --git a/backend/vitest.config.ts b/backend/vitest.config.ts
index eb261fd5..fd4035ef 100644
--- a/backend/vitest.config.ts
+++ b/backend/vitest.config.ts
@@ -8,11 +8,19 @@ export default defineConfig({
     exclude: ['dist/**', 'node_modules/**'],
     // Each test file gets its own worker so singletons are fresh between files.
     pool: 'forks',
+    // Cap concurrency: each worker dynamic-imports the full Express stack
+    // (TypeScript transform + DB init + every migration), so an uncapped
+    // fork pool that scales with availableParallelism saturates CPU and
+    // the suite spends most of its wall time waiting on cold-start
+    // contention. Four parallel workers is a sweet spot on both CI
+    // runners and laptops.
+    maxWorkers: 4,
+    minWorkers: 1,
     // Timeout generous for DB init and HTTP calls.
     testTimeout: 30_000,
     // Every test file dynamic-imports the full Express stack; each fork pays
     // TypeScript transformation cost and can take tens of seconds under
-    // CPU contention when all 64 fork workers run at once.
+    // CPU contention.
     hookTimeout: 45_000,
     // Sequential within each file (DB state is shared per file).
     sequence: { concurrent: false },