fix: keep sse streams alive behind proxies

.env.example

@@ -8,6 +8,7 @@ AUTO_OPEN_BROWSER=false
 STALE_DATA_MAX_AGE_MINUTES=60
 TERMINAL_ACTIONS_ENABLED=true
 SWEEP_TOKEN=
+SSE_HEARTBEAT_INTERVAL_MS=25000
 BRIEF_VERBOSITY=standard
 
 # LLM layer

README.md

@@ -137,6 +137,7 @@ AUTO_OPEN_BROWSER=false
 STALE_DATA_MAX_AGE_MINUTES=60
 TERMINAL_ACTIONS_ENABLED=true
 SWEEP_TOKEN=
+SSE_HEARTBEAT_INTERVAL_MS=25000
 BRIEF_VERBOSITY=standard
 
 LLM_PROVIDER=openrouter
@@ -190,6 +191,20 @@ For Pangolin or another reverse proxy, forward HTTP traffic to `intelligence-ter
 
 The dashboard Terminal Actions panel can trigger `status`, `sweep`, and `brief` through `/api/action`. Leave `TERMINAL_ACTIONS_ENABLED=true` for a private home-server deployment. For an internet-exposed deployment, set `SWEEP_TOKEN` and pass it through trusted automation, or set `TERMINAL_ACTIONS_ENABLED=false` to disable browser-triggered actions. If you protect actions with `SWEEP_TOKEN`, the browser can send it from `localStorage.crucix_sweep_token`.
 
+#### Reverse Proxy SSE
+
+The dashboard receives live sweep updates from `GET /events` using Server-Sent Events. The server sends `retry: 10000` reconnect guidance and lightweight heartbeat comments every `SSE_HEARTBEAT_INTERVAL_MS` milliseconds so reverse proxies do not close an otherwise idle stream between 15-minute sweeps.
+
+Recommended proxy settings:
+
+| Proxy | Setting |
+| --- | --- |
+| Pangolin / Traefik-style frontends | Keep response streaming enabled and set idle timeouts above `SSE_HEARTBEAT_INTERVAL_MS`. |
+| Nginx | Disable proxy buffering for `/events`, keep `proxy_read_timeout` above the heartbeat interval, and preserve `Connection: keep-alive`. |
+| Cloudflare-style proxies | Keep the heartbeat below common idle cutoffs; the default 25s is intentionally conservative. |
+
+If you raise the heartbeat interval, keep it shorter than the lowest idle timeout in the proxy chain.
+
 #### Build And Publish Your Gitea Image
 
 ```bash

crucix.config.mjs

@@ -25,6 +25,7 @@ export default {
   staleDataMaxAgeMinutes: intEnv('STALE_DATA_MAX_AGE_MINUTES', 60),
   sweepToken: process.env.SWEEP_TOKEN || null,
   terminalActionsEnabled: boolEnv('TERMINAL_ACTIONS_ENABLED', true),
+  sseHeartbeatIntervalMs: intEnv('SSE_HEARTBEAT_INTERVAL_MS', 25000),
 
   llm: {
     provider: process.env.LLM_PROVIDER || null, // anthropic | openai | gemini | codex | openrouter | minimax | mistral | ollama | grok

server.mjs

@@ -328,10 +328,24 @@ app.get('/events', (req, res) => {
     'Cache-Control': 'no-cache',
     'Connection': 'keep-alive',
     'Access-Control-Allow-Origin': '*',
+    'X-Accel-Buffering': 'no',
   });
+  res.write('retry: 10000\n');
   res.write('data: {"type":"connected"}\n\n');
+  const heartbeatMs = Math.max(5000, config.sseHeartbeatIntervalMs || 25000);
+  const heartbeat = setInterval(() => {
+    try {
+      res.write(`: heartbeat ${new Date().toISOString()}\n\n`);
+    } catch {
+      clearInterval(heartbeat);
+      sseClients.delete(res);
+    }
+  }, heartbeatMs);
   sseClients.add(res);
-  req.on('close', () => sseClients.delete(res));
+  req.on('close', () => {
+    clearInterval(heartbeat);
+    sseClients.delete(res);
+  });
 });
 
 function broadcast(data) {

test/fetch-utils.test.mjs

@@ -1,5 +1,6 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
 import { safeFetch, safeFetchText, getFetchMetrics } from '../apis/utils/fetch.mjs';
 
 test('safeFetch reports HTML as degraded JSON response', async () => {
@@ -34,3 +35,14 @@ test('safeFetchText returns text and byte count', async () => {
     globalThis.fetch = originalFetch;
   }
 });
+
+test('SSE endpoint sends reconnect guidance and clears heartbeat timer', () => {
+  const server = readFileSync(new URL('../server.mjs', import.meta.url), 'utf8');
+  const config = readFileSync(new URL('../crucix.config.mjs', import.meta.url), 'utf8');
+  assert.match(config, /sseHeartbeatIntervalMs/);
+  assert.match(server, /retry: 10000\\n/);
+  assert.match(server, /setInterval\(\(\) =>/);
+  assert.match(server, /: heartbeat/);
+  assert.match(server, /clearInterval\(heartbeat\)/);
+  assert.match(server, /X-Accel-Buffering/);
+});