diff --git a/package.json b/package.json
index d4c50331..19f43484 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,7 @@
     "format": "pretty-quick --staged",
     "format:all": "prettier --write .",
     "test": "npm run test:unit",
-    "test:unit": "node --import ./tests/unit/env.js --test-isolation=none --test-force-exit --test 'tests/unit/specs/**/*.test.js'",
+    "test:unit": "node --import ./tests/unit/env.js --test-isolation=none --test-force-exit --test-reporter=./tests/unit/testReporter.js --test 'tests/unit/specs/**/*.test.js'",
     "test:unit:coverage": "node --import ./tests/unit/env.js --test-isolation=none --test-force-exit --experimental-test-coverage --test-coverage-include='src/js/**' --test 'tests/unit/specs/**/*.test.js'",
     "test:e2e": "npx playwright test",
     "test:visual": "VISUAL_CAPTURE_DIR=tests/.artifacts/visual npx playwright test tests/e2e/specs/views",
diff --git a/tests/unit/testReporter.js b/tests/unit/testReporter.js
new file mode 100644
index 00000000..4ad3aab8
--- /dev/null
+++ b/tests/unit/testReporter.js
@@ -0,0 +1,25 @@
+import { compose } from "node:stream";
+import { spec } from "node:test/reporters";
+
+const THRESHOLD_MS = Number(process.env.SLOW_TEST_MS ?? 500);
+
+// Custom node:test reporter to record slow tests (>500ms by default)
+export default async function* testReporter(source) {
+  let slowCount = 0;
+  const trackSlowTests = async function* () {
+    for await (const event of source) {
+      if (event.type === "test:pass" || event.type === "test:fail") {
+        const { details } = event.data;
+        if (details?.type !== "suite" && details?.duration_ms >= THRESHOLD_MS) {
+          slowCount++;
+        }
+      }
+      yield event;
+    }
+    yield {
+      type: "test:diagnostic",
+      data: { nesting: 0, message: `slow ${slowCount}` },
+    };
+  };
+  yield* compose(trackSlowTests(), spec);
+}