perf(web): add cache headers for web UI static assets saving 90% data traffic in loading pages

.changeset/web-assets-cache-headers.md

@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+web: Serve hashed static assets with long-lived immutable cache headers so repeat visits load faster.

packages/kap-server/src/routes/webAssets.ts

@@ -1,6 +1,6 @@
 import { createReadStream } from 'node:fs';
 import { stat } from 'node:fs/promises';
-import { extname, join, normalize, resolve, sep } from 'node:path';
+import { extname, join, normalize, relative, resolve, sep } from 'node:path';
 
 import type { FastifyReply, FastifyRequest } from 'fastify';
 
@@ -57,9 +57,19 @@ async function serveWebAsset(
   return reply
     .type(mimeType(filePath))
     .header('Content-Length', String(fileInfo.size))
+    .header('Cache-Control', cacheControl(assetsDir, filePath))
     .send(createReadStream(filePath));
 }
 
+// Vite emits content-hashed files under `assets/` — cache them forever.
+// Everything else (index.html, SPA fallback, favicon, ...) must revalidate.
+function cacheControl(assetsDir: string, filePath: string): string {
+  const rel = relative(resolve(assetsDir), filePath);
+  return rel.startsWith(`assets${sep}`)
+    ? 'public, max-age=31536000, immutable'
+    : 'no-cache';
+}
+
 async function resolveStaticFile(
   assetsDir: string,
   pathname: string,