fix(workspace): add COOP+COEP (credentialless) headers so embedded HermesWorld WebGL keeps SharedArrayBuffer multithreading — matches standalone web client latency/perf instead of dropping to single-threaded in the iframe

vite.config.ts

@@ -480,6 +480,19 @@ const config = defineConfig(({ mode, command }) => {
       ],
     },
     server: {
+      // Cross-origin isolation so the embedded HermesWorld WebGL client keeps
+      // SharedArrayBuffer multithreading (matches the standalone web client at
+      // play.hermes-world.ai). Without these, the iframe silently drops to a
+      // single thread → render+physics+netcode contend on one thread → inflated
+      // ping / worse frame pacing even though network RTT is identical.
+      // COEP 'credentialless' enables isolation WITHOUT requiring CORP headers
+      // on every cross-origin asset (fonts/images); the web client already sends
+      // cross-origin-resource-policy: cross-origin so the iframe still embeds.
+      // Same-origin agent API (/ws-claude, /api/claude-proxy) is unaffected.
+      headers: {
+        'Cross-Origin-Opener-Policy': 'same-origin',
+        'Cross-Origin-Embedder-Policy': 'credentialless',
+      },
       // Force IPv4 — 'localhost' resolves to ::1 (IPv6) on Windows, breaking connectivity
       host: '0.0.0.0',
       // Port precedence:
@@ -575,6 +588,17 @@ const config = defineConfig(({ mode, command }) => {
           if (command !== 'serve') return
         },
         configureServer(server) {
+          // Cross-origin isolation headers on EVERY response so the embedded
+          // HermesWorld WebGL client keeps SharedArrayBuffer multithreading
+          // (matches play.hermes-world.ai). Injected via middleware because the
+          // TanStack Start SSR handler owns the HTML response and overrides
+          // vite's server.headers. COEP 'credentialless' avoids requiring CORP
+          // on every cross-origin asset; same-origin agent API is unaffected.
+          server.middlewares.use((_req, res, next) => {
+            res.setHeader('Cross-Origin-Opener-Policy', 'same-origin')
+            res.setHeader('Cross-Origin-Embedder-Policy', 'credentialless')
+            next()
+          })
           server.middlewares.use(async (req, res, next) => {
             const requestPath = req.url?.split('?')[0]
             if (req.method === 'GET' && requestPath === '/api/healthcheck') {