fix: support dev server previews over relay

packages/web/server/lib/relay/DOCUMENTATION.md

@@ -41,7 +41,7 @@ Relay is not a separate link format: it is one transport candidate inside the un
 Everything a client normally sends to the single OpenChamber origin:
 - **HTTP** — REST endpoints and proxied OpenCode SDK calls under `/api/*`, plus `/auth/*` and `/health`.
 - **SSE** — long-lived streamed responses (the event stream and notifications). These are just HTTP responses whose body streams; the tunnel needs no special SSE handling.
-- **WebSocket** — the endpoints that use a real socket (the global event stream on platforms that support WS, terminal I/O, dictation).
+- **WebSocket** — the endpoints that use a real socket (the global event stream on platforms that support WS, terminal I/O, dictation, and desktop dev-server previews).
 
 The host dispatcher restricts tunneled traffic to explicit path allowlists (one for HTTP, one for WS).
 

packages/web/server/lib/relay/tunnel-host.js

@@ -33,7 +33,9 @@ const ALLOWED_WS_PATHS = new Set([
   '/api/event/ws',
   '/api/terminal/ws',
   '/api/dictation/ws',
+  '/api/dev-tunnel',
 ]);
+export const isAllowedRelayWebSocketPath = (pathname) => ALLOWED_WS_PATHS.has(pathname);
 
 // Hop-by-hop headers stripped from tunneled requests; `host` is set by fetch
 // to the loopback origin. content-length is dropped too because the body is
@@ -425,7 +427,7 @@ export const createTunnelHost = ({ connectionId, getLocalPort, sendFrame, getBuf
       void sendAbort(streamId, error?.message ?? 'malformed ws open');
       return;
     }
-    if (!ALLOWED_WS_PATHS.has(open.path)) {
+    if (!isAllowedRelayWebSocketPath(open.path)) {
       void sendAbort(streamId, 'Path is not allowed through the relay');
       return;
     }

packages/web/server/lib/relay/tunnel-host.test.js

@@ -1,7 +1,7 @@
 import { describe, test, expect } from 'bun:test';
 import http from 'node:http';
 
-import { createTunnelHost } from './tunnel-host.js';
+import { createTunnelHost, isAllowedRelayWebSocketPath } from './tunnel-host.js';
 import { decodeTunnelFrame, encodeTunnelFrame, encodeJsonPayload, TunnelFrameType } from './tunnel-codec.js';
 
 const startLoopback = () =>
@@ -145,3 +145,11 @@ describe('tunnel-host HTTP body forwarding', () => {
     await loopback.stop();
   });
 });
+
+describe('relay host WebSocket allowlist', () => {
+  test('allows only the exact dev-server tunnel path', () => {
+    expect(isAllowedRelayWebSocketPath('/api/dev-tunnel')).toBe(true);
+    expect(isAllowedRelayWebSocketPath('/api/dev-tunnel/')).toBe(false);
+    expect(isAllowedRelayWebSocketPath('/api/database/ws')).toBe(false);
+  });
+});