fix(process): harden graceful kill-tree cancellation semantics

src/process/supervisor/adapters/pty.ts

@@ -1,7 +1,9 @@
-import { killProcessTree } from "../../kill-tree.js";
 import type { ManagedRunStdin } from "../types.js";
+import { killProcessTree } from "../../kill-tree.js";
 import { toStringEnv } from "./env.js";
 
+const FORCE_KILL_WAIT_FALLBACK_MS = 4000;
+
 type PtyExitEvent = { exitCode: number; signal?: number };
 type PtyDisposable = { dispose: () => void };
 type PtySpawnHandle = {
@@ -70,11 +72,21 @@ export async function createPtyAdapter(params: {
     | null = null;
   let waitPromise: Promise<{ code: number | null; signal: NodeJS.Signals | number | null }> | null =
     null;
+  let forceKillWaitFallbackTimer: NodeJS.Timeout | null = null;
+
+  const clearForceKillWaitFallback = () => {
+    if (!forceKillWaitFallbackTimer) {
+      return;
+    }
+    clearTimeout(forceKillWaitFallbackTimer);
+    forceKillWaitFallbackTimer = null;
+  };
 
   const settleWait = (value: { code: number | null; signal: NodeJS.Signals | number | null }) => {
     if (waitResult) {
       return;
     }
+    clearForceKillWaitFallback();
     waitResult = value;
     if (resolveWait) {
       const resolve = resolveWait;
@@ -83,6 +95,16 @@ export async function createPtyAdapter(params: {
     }
   };
 
+  const scheduleForceKillWaitFallback = (signal: NodeJS.Signals) => {
+    clearForceKillWaitFallback();
+    // Some PTY hosts fail to emit onExit after kill; use a delayed fallback
+    // so callers can still unblock without marking termination immediately.
+    forceKillWaitFallbackTimer = setTimeout(() => {
+      settleWait({ code: null, signal });
+    }, FORCE_KILL_WAIT_FALLBACK_MS);
+    forceKillWaitFallbackTimer.unref();
+  };
+
   exitListener =
     pty.onExit((event) => {
       const signal = event.signal && event.signal !== 0 ? event.signal : null;
@@ -151,9 +173,10 @@ export async function createPtyAdapter(params: {
     } catch {
       // ignore kill errors
     }
-    // Some PTY hosts do not emit `onExit` reliably after kill.
-    // Ensure waiters can progress on forced termination.
-    settleWait({ code: null, signal });
+
+    if (signal === "SIGKILL") {
+      scheduleForceKillWaitFallback(signal);
+    }
   };
 
   const dispose = () => {
@@ -167,6 +190,7 @@ export async function createPtyAdapter(params: {
     } catch {
       // ignore disposal errors
     }
+    clearForceKillWaitFallback();
     dataListener = null;
     exitListener = null;
     settleWait({ code: null, signal: null });