fix: ensure spawned processes are fully killed

package.json

@@ -83,6 +83,7 @@
     "stylelint-config-recommended-scss": "^16.0.0",
     "tiktoken": "^1.0.22",
     "tinyglobby": "^0.2.14",
+    "tree-kill": "^1.2.2",
     "tsx": "^4.20.3",
     "typescript": "^5.8.3",
     "yargs": "^18.0.0",

runner/orchestration/generate.ts

@@ -158,7 +158,7 @@ export async function generateCodeAndAssess(options: {
           ? // Building can be really expensive. We likely should add support for "CPU hints" per environment.
             // E.g. CLI building is really CPU intensive with ESBuild being multi-core.
             // TODO: Follow-up on this and add CPU hints.
-            Math.floor(availableParallelism() * 0.4 * 0.5)
+            Math.floor(appConcurrency * 0.5)
           : Infinity,
     });
 

runner/utils/kill-gracefully.ts

@@ -1,13 +1,31 @@
 import { ChildProcess } from 'child_process';
+import treeKill from 'tree-kill';
+
+function treeKillPromise(pid: number, signal: string): Promise<void> {
+  return new Promise((resolve, reject) => {
+    treeKill(pid, signal, (err) => {
+      if (err !== undefined) {
+        reject(err);
+      } else {
+        resolve(err);
+      }
+    });
+  });
+}
 
 export function killChildProcessGracefully(
   child: ChildProcess,
   timeoutInMs = 1000 * 10 // 10s
 ): Promise<void> {
-  return new Promise((resolve, reject) => {
+  return new Promise(async (resolve, reject) => {
     // Process already exited.
     if (child.exitCode !== null) {
       resolve();
+      return;
+    }
+    const pid = child.pid;
+    if (pid === undefined) {
+      throw new Error(`No process ID for processed that should be killed.`);
     }
 
     // Watch for exiting, so that we can cancel the timeout(s) then.
@@ -18,10 +36,17 @@ export function killChildProcessGracefully(
     });
 
     // Send SIGTERM
-    child.kill('SIGTERM');
+    try {
+      await treeKillPromise(pid, 'SIGTERM');
+    } catch (e) {
+      console.error(
+        `Could not send "SIGTERM" for killing process. Trying "SIGKILL".`
+      );
+    }
+
     // Start a timeout for the SIGKILL fallback
     const sigkillTimeoutId = setTimeout(
-      () => child.kill('SIGKILL'),
+      () => treeKill(pid, 'SIGKILL'),
       timeoutInMs
     );
     // Start another timeout to reject the promise if the child process never fires `exit` for some reasons.