diff --git a/server.js b/server.js
index b4cd8ab..c7b66fa 100644
--- a/server.js
+++ b/server.js
@@ -37,9 +37,13 @@ app.post('/api/chat', (req, res) => {
     res.setHeader('Content-Type', 'text/event-stream');
     res.setHeader('Cache-Control', 'no-cache');
     res.setHeader('Connection', 'keep-alive');
+    res.flushHeaders(); // establish SSE connection immediately
 
     const env = { ...process.env, CLAUDE_CONFIG_DIR: configDir };
 
+    // heartbeat to keep connection alive during long generation
+    const heartbeat = setInterval(() => res.write(': ping\n\n'), 15000);
+
     const proc = spawn(CLAUDE_BIN, ['-p', text, '--model', modelId, '--output-format', 'stream-json', '--verbose'], {
         env,
         stdio: ['ignore', 'pipe', 'pipe'],
@@ -49,24 +53,17 @@ app.post('/api/chat', (req, res) => {
     proc.stdout.on('data', (chunk) => {
         buf += chunk.toString();
         const lines = buf.split('\n');
-        buf = lines.pop(); // keep incomplete line
+        buf = lines.pop();
         for (const line of lines) {
             if (!line.trim()) continue;
             try {
                 const obj = JSON.parse(line);
-                // streaming delta
-                if (obj.type === 'content_block_delta' && obj.delta?.type === 'text_delta') {
-                    res.write(`data: ${JSON.stringify({ text: obj.delta.text })}\n\n`);
-                }
-                // fallback: full assistant message
-                else if (obj.type === 'assistant' && obj.message?.content) {
+                if (obj.type === 'assistant' && obj.message?.content) {
                     for (const block of obj.message.content) {
                         if (block.type === 'text') res.write(`data: ${JSON.stringify({ text: block.text })}\n\n`);
                     }
-                }
-                // error in result
-                else if (obj.type === 'result' && obj.is_error) {
-                    res.write(`data: ${JSON.stringify({ error: obj.result || 'unknown error' })}\n\n`);
+                } else if (obj.type === 'result' && obj.is_error) {
+                    res.write(`data: ${JSON.stringify({ error: obj.result || 'error' })}\n\n`);
                 }
             } catch (e) {}
         }
@@ -85,6 +82,7 @@ app.post('/api/chat', (req, res) => {
     });
 
     proc.on('close', (code, signal) => {
+        clearInterval(heartbeat);
         console.log(`[claude close] code=${code} signal=${signal} stderr=${stderrBuf.substring(0,300)}`);
         if (code !== 0) {
             const msg = stderrBuf.trim() || `code=${code} signal=${signal}`;
@@ -96,7 +94,7 @@ app.post('/api/chat', (req, res) => {
 
     let finished = false;
     proc.on('close', () => { finished = true; });
-    res.on('close', () => { if (!finished) try { proc.kill(); } catch (e) {} });
+    res.on('close', () => { clearInterval(heartbeat); if (!finished) try { proc.kill(); } catch (e) {} });
 });
 
 app.listen(8108, () => console.log('sechenov :8108'));