fix(health): stop expired probes before work starts

CHANGES.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## Unreleased
+
+- `@openstatus/health`: Probes no longer start work if an async `skip`
+  returns `false` after the timeout. The completed timeout report stays unchanged.
+
 ## 0.1.2
 
 - Every hosting package (`fly`, `koyeb`, `railway`, `vercel`, `cloudflare`)

packages/health/src/run.test.ts

@@ -175,6 +175,27 @@ test("runProbes() times out a hanging skip()", async () => {
   assert.equal(report.checks[0].status, "timeout");
 });
 
+test("runProbes() does not start work when skip() resolves false after timeout", async () => {
+  const skip = Promise.withResolvers<boolean>();
+  let ran = false;
+  const report = await runProbes([{
+    name: "a",
+    timeoutMs: 10,
+    skip: () => skip.promise,
+    run: () => {
+      ran = true;
+    },
+  }]);
+  assert.equal(report.checks[0].status, "timeout");
+  const completed = structuredClone(report);
+
+  skip.resolve(false);
+  await delay(0);
+
+  assert.equal(ran, false);
+  assert.deepEqual(report, completed);
+});
+
 test("runProbes() passes name, critical and timeoutMs to run()", async () => {
   let seen: { name: string; critical: boolean; timeoutMs: number } | undefined;
   await runProbes([{

packages/health/src/run.ts

@@ -63,6 +63,7 @@ async function runProbe(
 
   const work = Promise.resolve().then(async () => {
     if (await probe.skip?.()) return "skipped";
+    controller.signal.throwIfAborted();
     await probe.run(controller.signal, ctx);
     return "ok";
   });