Observe startup readiness in structured stderr logs

.github/workflows/verify.yml

@@ -19,6 +19,8 @@ jobs:
           version: 0.27.23
       - name: Verify package behavior
         run: node scripts/verify.mjs
+      - name: Verify process observation
+        run: node --test scripts/observe-process.test.mjs scripts/verify-native-web.test.mjs
 
       - name: Verify native applications
         if: github.event_name == 'workflow_dispatch'

scripts/observe-process.mjs

@@ -6,15 +6,17 @@ export function observeProcess(child, readiness, timeoutMs) {
     const timer = setTimeout(() => {
       reject(new Error(`Process startup timed out\n${diagnostics()}`));
     }, timeoutMs);
-    child.stdout.setEncoding('utf8').on('data', chunk => {
-      output += chunk;
-      const match = output.match(readiness);
-      if (match) {
-        clearTimeout(timer);
-        resolve(match);
-      }
-    });
-    child.stderr.setEncoding('utf8').on('data', chunk => { errors += chunk; });
+    for (const [channel, stream] of [['stdout', child.stdout], ['stderr', child.stderr]]) {
+      stream.setEncoding('utf8').on('data', chunk => {
+        if (channel === 'stdout') output += chunk;
+        else errors += chunk;
+        const match = (channel === 'stdout' ? output : errors).match(readiness);
+        if (match) {
+          clearTimeout(timer);
+          resolve(match);
+        }
+      });
+    }
     child.once('error', error => {
       clearTimeout(timer);
       reject(error);

scripts/observe-process.test.mjs

@@ -29,6 +29,18 @@ test('recognizes fragmented readiness and retains later diagnostics', async () =
   assert.match(observed.diagnostics(), /after readiness/);
 });
 
+test('recognizes fragmented structured readiness on stderr', async () => {
+  const child = spawn(process.execPath, ['-e',
+    'process.stderr.write("123 [INFO] service REA"); setTimeout(() => { process.stderr.write("DY http://127.0.0.1:1234\\n"); process.stdout.write("program output\\n"); }, 20);'],
+    { windowsHide: true });
+  const closed = once(child, 'close');
+  const observed = observeProcess(child, /READY (http:\/\/127\.0\.0\.1:\d+)\n/, 5000);
+  assert.equal((await observed.ready)[1], 'http://127.0.0.1:1234');
+  await closed;
+  assert.match(observed.diagnostics(), /program output/);
+  assert.match(observed.diagnostics(), /123 \[INFO\] service READY/);
+});
+
 test('timeout reports captured output and leaves process ownership with caller', async () => {
   const child = spawn(process.execPath, ['-e', 'console.log("booting"); setInterval(() => {}, 1000);'],
     { windowsHide: true });