feat: improve Windows cache management and enhance FastAPI/Next.js logging in the Electron app

electron/app/main.ts

@@ -1,6 +1,7 @@
 require("dotenv").config();
 import { app, BrowserWindow } from "electron";
 import path from "path";
+import fs from "fs";
 import { findUnusedPorts, killProcess, setupEnv, setUserConfig } from "./utils";
 import { startFastApiServer, startNextJsServer } from "./utils/servers";
 import { ChildProcessByStdio } from "child_process";
@@ -16,6 +17,30 @@ var nextjsProcess: any;
 
 app.commandLine.appendSwitch('gtk-version', '3');
 
+// Mitigate "Unable to move the cache: Access is denied" on Windows (Chromium disk cache).
+// Use explicit cache paths and remove stale old_* dirs that cause move failures.
+if (process.platform === "win32") {
+  const ud = app.getPath("userData");
+  const cacheBase = path.join(ud, "Cache");
+  const gpuCacheBase = path.join(ud, "GPUCache");
+  app.setPath("cache", cacheBase);
+  app.commandLine.appendSwitch("disk-cache-dir", cacheBase);
+  try {
+    [cacheBase, gpuCacheBase].forEach((dir) => {
+      if (fs.existsSync(dir)) {
+        const entries = fs.readdirSync(dir, { withFileTypes: true });
+        for (const e of entries) {
+          if (e.isDirectory() && e.name.startsWith("old_")) {
+            fs.rmSync(path.join(dir, e.name), { recursive: true, force: true });
+          }
+        }
+      }
+    });
+  } catch {
+    /* ignore cleanup errors */
+  }
+}
+
 const createWindow = () => {
   win = new BrowserWindow({
     width: 1280,

electron/app/utils/servers.ts

@@ -24,8 +24,22 @@ export async function startFastApiServer(
     const binary = process.platform === "win32" ? "fastapi.exe" : "fastapi";
     command = path.join(directory, binary);
     args = ["--port", port.toString()];
+    if (!fs.existsSync(command)) {
+      throw new Error(
+        `FastAPI binary not found at ${command}. Rebuild the app for ${process.platform} or run in dev mode.`
+      );
+    }
   }
 
+  const safeLog = (data: Buffer | string, logPath: string) => {
+    try {
+      fs.appendFileSync(logPath, data);
+    } catch {
+      /* ignore if logs dir not writable */
+    }
+  };
+  const fastapiLogPath = path.join(logsDir, "fastapi-server.log");
+
   const fastApiProcess = spawn(
     command,
     args,
@@ -36,13 +50,16 @@ export async function startFastApiServer(
     }
   );
   fastApiProcess.stdout.on("data", (data: any) => {
-    fs.appendFileSync(path.join(logsDir, "fastapi-server.log"), data);
+    safeLog(data, fastapiLogPath);
     console.log(`FastAPI: ${data}`);
   });
   fastApiProcess.stderr.on("data", (data: any) => {
-    fs.appendFileSync(path.join(logsDir, "fastapi-server.log"), data);
+    safeLog(data, fastapiLogPath);
     console.error(`FastAPI: ${data}`);
   });
+  fastApiProcess.on("error", (err) => {
+    safeLog(`Spawn error: ${err.message}\n`, fastapiLogPath);
+  });
   // Wait for FastAPI server to start
   await waitForServer(`${localhost}:${port}/docs`);
   return fastApiProcess;
@@ -67,17 +84,25 @@ export async function startNextJsServer(
         env: { ...process.env, ...env },
       }
     );
+    const nextjsLogPath = path.join(logsDir, "nextjs-server.log");
+    const safeNextLog = (d: Buffer | string) => {
+      try {
+        fs.appendFileSync(nextjsLogPath, d);
+      } catch {
+        /* ignore */
+      }
+    };
     nextjsProcess.stdout.on("data", (data: any) => {
-      fs.appendFileSync(path.join(logsDir, "nextjs-server.log"), data);
+      safeNextLog(data);
       console.log(`NextJS: ${data}`);
     });
     nextjsProcess.stderr.on("data", (data: any) => {
-      fs.appendFileSync(path.join(logsDir, "nextjs-server.log"), data);
+      safeNextLog(data);
       console.error(`NextJS: ${data}`);
     });
   } else {
     // Start NextJS build server
-    nextjsProcess = startNextjsBuildServer(directory, port);
+    nextjsProcess = await startNextjsBuildServer(directory, port);
   }
 
   // Wait for NextJS server to start
@@ -85,16 +110,20 @@ export async function startNextJsServer(
   return nextjsProcess;
 }
 
-async function startNextjsBuildServer(directory: string, port: number) {
-  const server = http.createServer((req, res) => {
-    return handler(req, res, {
-      public: directory,
-      cleanUrls: true,
+function startNextjsBuildServer(directory: string, port: number): Promise<http.Server> {
+  return new Promise((resolve, reject) => {
+    const server = http.createServer((req, res) => {
+      return handler(req, res, {
+        public: directory,
+        cleanUrls: true,
+      });
+    });
+    server.on("error", reject);
+    server.listen(port, () => {
+      server.off("error", reject);
+      resolve(server);
     });
   });
-
-  server.listen(port);
-  return server;
 }