Stream the answer as it is written, and let the operator stop it

Plugin/unraid/api/ai.php

@@ -207,6 +207,62 @@ if ($action === 'memory_set') {
     exit;
 }
 
+// ── stop ──────────────────────────────────────────────────────────────────────
+// Cancels a generation in flight. Only ever signals ONE pid, verified to be the worker for this
+// exact job — never a process group. Signalling a group is what took the WebGUI down on
+// 2026-08-07, and no group kill is needed here: the worker is a single php process whose only
+// child-like thing is an HTTP connection to Ollama, which dies with it.
+//
+// Whatever was already generated is kept. A turn stopped at 80% is usually stopped because the
+// operator has seen enough, not because they want it discarded.
+if ($action === 'stop') {
+    if (!$isPost) { http_response_code(405); echo json_encode(['ok' => false, 'error' => 'POST only']); exit; }
+
+    $token = trim($_POST['token'] ?? '');
+    if (vv_ai_job_path($token) === null) {
+        echo json_encode(['ok' => false, 'error' => 'Invalid token']); exit;
+    }
+
+    $job = vv_ai_job_read($token);
+    if ($job === null) { echo json_encode(['ok' => false, 'error' => 'No such job']); exit; }
+
+    $status = (string)($job['status'] ?? '');
+    if ($status === 'done' || $status === 'error' || $status === 'stopped') {
+        echo json_encode(['ok' => true, 'already' => true, 'status' => $status]); exit;
+    }
+
+    $pid = (int)($job['pid'] ?? 0);
+    // Below 2 is init or nonsense. A pid we cannot verify is a pid we do not signal.
+    $killed = false;
+    if ($pid >= 2) {
+        // Pid reuse is the reason for this: the recorded worker may have exited seconds ago and
+        // the number been handed to something else entirely. The cmdline must name both this
+        // worker and this job's own file before anything is signalled.
+        $cmdline = @file_get_contents("/proc/$pid/cmdline");
+        $cmdline = $cmdline === false ? '' : str_replace("\0", ' ', $cmdline);
+        if (strpos($cmdline, 'ai_chat_worker.php') !== false && strpos($cmdline, $token) !== false) {
+            $killed = @posix_kill($pid, SIGTERM);
+            // No escalation ladder. The worker holds no lock and writes the job file atomically,
+            // so there is no cleanup that a delay would protect — and a SIGKILL race could land
+            // between the temp write and the rename.
+        }
+    }
+
+    // The job file is rewritten either way. If the pid could not be verified the worker is
+    // already gone, and the page still needs a terminal state instead of polling to its ceiling.
+    $job['status']  = 'stopped';
+    $job['stopped'] = true;
+    $job['answer']  = trim((string)($job['partial'] ?? $job['answer'] ?? ''));
+    unset($job['partial']);
+    @file_put_contents(vv_ai_job_path($token), json_encode($job));
+
+    vv_ai_log(sprintf('stop token=%s pid=%d signalled=%s kept=%d chars',
+        substr($token, 0, 12), $pid, $killed ? 'yes' : 'no', strlen($job['answer'])));
+
+    echo json_encode(['ok' => true, 'signalled' => $killed, 'kept' => strlen($job['answer'])]);
+    exit;
+}
+
 // ── clear ─────────────────────────────────────────────────────────────────────
 if ($action === 'clear') {
     if (!$isPost) { http_response_code(405); echo json_encode(['ok' => false, 'error' => 'POST only']); exit; }
@@ -433,7 +489,12 @@ if ($action === 'ask') {
         exit;
     }
 
-    $cmd = 'nohup php ' . escapeshellarg($worker) . ' '
+    // setsid, not just nohup. nohup detaches from the terminal but leaves the child in the
+    // caller's process group — php-fpm's. That is the arrangement that took the WebGUI down on
+    // 2026-08-07 when a Stop signalled a group it did not own. Stop below signals one verified
+    // pid and never a group, so this is belt and braces, but it also means a php-fpm restart no
+    // longer takes a running generation with it.
+    $cmd = 'setsid nohup php ' . escapeshellarg($worker) . ' '
          . escapeshellarg($jobFile) . ' '
          . escapeshellarg($question) . ' '
          . escapeshellarg(json_encode($clean)) . ' '