diff --git a/test/js/node/worker_threads/worker_destruction.test.ts b/test/js/node/worker_threads/worker_destruction.test.ts
index 02855dd90ce5..ad0d8d62ca01 100644
--- a/test/js/node/worker_threads/worker_destruction.test.ts
+++ b/test/js/node/worker_threads/worker_destruction.test.ts
@@ -1,12 +1,30 @@
 import { describe, expect, test } from "bun:test";
-import { bunEnv, bunExe, bunRun } from "harness";
+import { bunEnv, bunExe, bunRun, isDebug } from "harness";
 import { join } from "path";
 
+// worker_thread_check.ts runs RUN_COUNT rounds of CONCURRENCY Workers, terminating each as it comes
+// online. On a debug+ASAN build one worker_threads spawn + terminate costs ~2.4s of CPU (~30ms on
+// release), and the three cases run concurrently with each other and with the test below them, so the
+// file needs roughly 3 x CONCURRENCY x 2.4s + ~8s of CPU, spread over the available cores, to fit the
+// 5s default timeout: 5 x 10 takes ~30s per case, and even one round of 3 per case (~29s of CPU) times
+// out on 4 to 6 cores. Debug builds therefore take each teardown path once (~15s of CPU, 3 to 4s per
+// test on 4 cores); release builds, which is all CI runs (ASAN lanes included), keep the full count.
+const RUN_COUNT = isDebug ? 1 : 5;
+const CONCURRENCY = isDebug ? 1 : 10;
+
 describe("Worker destruction", () => {
   const method = ["Bun.connect", "Bun.listen", "fetch"];
   describe.each(method)("bun when %s is used in a Worker that is terminating", method => {
     test.concurrent("exits cleanly", async () => {
-      expect(await bunRun([join(import.meta.dir, "worker_thread_check.ts"), method])).toSpawn();
+      const result = await bunRun([join(import.meta.dir, "worker_thread_check.ts"), method], {
+        RUN_COUNT: String(RUN_COUNT),
+        CONCURRENCY: String(CONCURRENCY),
+      });
+      expect(result).toSpawn();
+      // One line per completed round, so a misread count cannot turn this into a no-op run.
+      expect(result.stdout.split("\n").map(line => line.replace(/ RSS \d+ MB$/, ""))).toEqual(
+        Array(RUN_COUNT).fill(`Spawned ${CONCURRENCY} workers`),
+      );
     });
   });
 
diff --git a/test/js/node/worker_threads/worker_thread_check.ts b/test/js/node/worker_threads/worker_thread_check.ts
index 531de8eb26fa..b1a5b62c284a 100644
--- a/test/js/node/worker_threads/worker_thread_check.ts
+++ b/test/js/node/worker_threads/worker_thread_check.ts
@@ -1,5 +1,6 @@
-const CONCURRENCY = 10;
-const RUN_COUNT = 5;
+// worker_destruction.test.ts lowers these on debug builds; see the note there.
+const CONCURRENCY = Number(process.env.CONCURRENCY ?? 10);
+const RUN_COUNT = Number(process.env.RUN_COUNT ?? 5);
 
 import { Worker, isMainThread, workerData } from "worker_threads";