fixing disconnection issue

packages/backend/src/routes/recommendations.ts

@@ -101,6 +101,67 @@ export default async function recommendationsRoute(fastify: FastifyInstance) {
 
     if (!rec) return reply.code(404).send({ error: 'Not found' });
 
+    // Set SSE headers and hijack before any branching
+    reply.raw.setHeader('Content-Type', 'text/event-stream');
+    reply.raw.setHeader('Cache-Control', 'no-cache');
+    reply.raw.setHeader('Connection', 'keep-alive');
+    reply.raw.setHeader('Access-Control-Allow-Origin', '*');
+    reply.raw.flushHeaders();
+    reply.hijack();
+
+    // Resilient write — swallows errors so a disconnected client never crashes
+    // an in-flight pipeline that is still running server-side.
+    const sseWrite = (event: SSEEvent) => {
+      try {
+        reply.raw.write(`data: ${JSON.stringify(event)}\n\n`);
+      } catch {
+        // Client disconnected — pipeline continues, writes are silently dropped
+      }
+    };
+
+    try {
+      // Already finished — send a synthetic completion event and close immediately.
+      if (rec.status === 'done') {
+        sseWrite({ stage: 'complete', status: 'done', data: { title: rec.title } });
+        return;
+      }
+
+      // Already errored — send a synthetic error event and close immediately.
+      if (rec.status === 'error') {
+        sseWrite({ stage: 'curator', status: 'error', data: { message: 'Pipeline failed' } });
+        return;
+      }
+
+      // Already running — the pipeline is executing on a previous connection.
+      // Poll the DB until it reaches a terminal state, then report the result.
+      // This prevents starting a duplicate pipeline run on page reload.
+      if (rec.status === 'running') {
+        const POLL_INTERVAL_MS = 2000;
+        const TIMEOUT_MS = 20 * 60 * 1000; // 20 minutes hard ceiling
+        const start = Date.now();
+        while (Date.now() - start < TIMEOUT_MS) {
+          await new Promise((resolve) => setTimeout(resolve, POLL_INTERVAL_MS));
+          const [current] = await db
+            .select({ status: recommendations.status, title: recommendations.title })
+            .from(recommendations)
+            .where(eq(recommendations.id, id));
+          if (!current || current.status === 'done') {
+            sseWrite({ stage: 'complete', status: 'done', data: { title: current?.title ?? rec.title } });
+            return;
+          }
+          if (current.status === 'error') {
+            sseWrite({ stage: 'curator', status: 'error', data: { message: 'Pipeline failed' } });
+            return;
+          }
+          // Still running — keep polling
+        }
+        // Timed out waiting — report as error
+        sseWrite({ stage: 'curator', status: 'error', data: { message: 'Pipeline timed out' } });
+        return;
+      }
+
+      // status === 'pending' — start the pipeline normally.
+
       // Load all feedback to potentially inject as context
       const feedbackRows = await db.select().from(feedback);
       const mediaLabel = rec.media_type === 'movie' ? 'Movie' : 'Show';
@@ -114,19 +175,6 @@ export default async function recommendationsRoute(fastify: FastifyInstance) {
               .join('\n')
           : undefined;
 
-    // Set SSE headers and hijack
-    reply.raw.setHeader('Content-Type', 'text/event-stream');
-    reply.raw.setHeader('Cache-Control', 'no-cache');
-    reply.raw.setHeader('Connection', 'keep-alive');
-    reply.raw.setHeader('Access-Control-Allow-Origin', '*');
-    reply.raw.flushHeaders();
-    reply.hijack();
-
-    const sseWrite = (event: SSEEvent) => {
-      reply.raw.write(`data: ${JSON.stringify(event)}\n\n`);
-    };
-
-    try {
       await runPipeline(rec, sseWrite, feedbackContext);
     } finally {
       reply.raw.end();