diff --git a/docs/auth-flow.md b/docs/auth-flow.md
new file mode 100644
index 0000000..a5e7892
--- /dev/null
+++ b/docs/auth-flow.md
@@ -0,0 +1,33 @@
+# Personal Authentication Mod Flow
+
+This document details the modifications and features integrated within `spt-launcher` and `server-csharp` to support the custom Personal Authentication Mod.
+
+## What is Personal Authentication?
+Unlike the vanilla SPT launcher which assumes 1 user = 1 machine, Personal Authentication enables multiple isolated accounts. Users register and log in to uniquely generated session IDs via `AuthRouter.cs` hooking into `LauncherCallbacks`.
+
+## The `server-csharp` Modifications:
+The server's default JSON payload parsing was too strict regarding unmapped JSON structures (like adding a `password` field). 
+
+We addressed this by updating the base interface in `SPTarkov.Server.Core`:
+```csharp
+namespace SPTarkov.Server.Core.Models.Eft.Launcher;
+
+public record LoginRequestData : IRequestData
+{
+    [JsonPropertyName("username")]
+    public string? Username { get; set; }
+
+    [JsonPropertyName("password")]
+    public string? Password { get; set; }
+}
+```
+Now, `LoginRequestData` natively accepts passwords, allowing Harmony Patches on `LauncherCallbacks.Login` and `LauncherCallbacks.Register` to validate against the database gracefully.
+
+## Custom Token Session vs Default Random Session Strings
+Vanilla SPT creates a random GUID session variable that is used loosely.
+With SSO:
+1. `spt-launcher` initiates an HTTP POST `/launcher/profile/login` with `username` and `password`.
+2. The Database (`DatabaseManager.cs`) verifies credentials against PostgreSQL passwords (hashed). 
+3. Returns a specific `SessionID` mapped directly to that User ID. 
+4. The launcher preserves this ID in cookies and local cache storage. 
+5. Sub-requests (Start Client, Fetch Match Profiles) utilize this single, constant Session ID instead of performing a secondary manual profile scan discovery via `/launcher/profiles`.
diff --git a/src/main/main.ts b/src/main/main.ts
index f0ab318..caa00bf 100644
--- a/src/main/main.ts
+++ b/src/main/main.ts
@@ -125,6 +125,11 @@ const checkServerHealth = async (): Promise<ServerHealthResult> => {
     const request = net.request({
       method: "GET",
       url,
+      headers: {
+        "Accept-Encoding": "identity",
+        requestcompressed: "0",
+        responsecompressed: "0",
+      }
     });
 
     const timeout = setTimeout(() => {
@@ -1336,8 +1341,10 @@ const postText = async (path: string, body: unknown) => {
 
 const requestSessionId = async (
   username: string,
+  password?: string,
 ): Promise<SessionRequestResult> => {
-  const loginResult = await postText("/launcher/profile/login", { username });
+  // 1. Login to get the session token
+  const loginResult = await postText("/launcher/profile/login", { username, password });
   if (!loginResult.ok) {
     return {
       ok: false,
@@ -1347,10 +1354,17 @@ const requestSessionId = async (
   }
 
   const sessionId = loginResult.data?.trim();
-  if (!sessionId) {
-    return { ok: false, error: "empty_session", url: loginResult.url };
+
+  // Check if session ID is empty or explicitly "FAILED"
+  if (!sessionId || sessionId === "FAILED" || sessionId === "") {
+    return {
+      ok: false,
+      error: sessionId === "FAILED" ? "login_failed_credentials" : "empty_session",
+      url: loginResult.url
+    };
   }
 
+  // With PersonalAuthMod, the sessionId is the unique token we need.
   return { ok: true, sessionId, url: loginResult.url };
 };
 
@@ -1359,6 +1373,7 @@ const isSessionInvalidStatus = (status?: number) =>
 
 const getSessionIdForUser = async (
   username: string,
+  password?: string,
 ): Promise<SessionLookupResult> => {
   const cached = await readSessionRecord();
   if (cached && cached.username === username && !isSessionExpired(cached)) {
@@ -1378,7 +1393,7 @@ const getSessionIdForUser = async (
     await clearSessionRecord();
   }
 
-  const loginResult = await requestSessionId(username);
+  const loginResult = await requestSessionId(username, password);
   if (!loginResult.ok) {
     return loginResult;
   }
@@ -1392,9 +1407,10 @@ const getSessionIdForUser = async (
   };
 };
 
-const registerProfile = async (username: string) => {
-  return await postJson("/launcher/profile/register", {
+const registerProfile = async (username: string, password?: string) => {
+  return await postText("/launcher/profile/register", {
     username,
+    password,
     edition: "Standard",
   });
 };
@@ -1420,294 +1436,309 @@ const createWindow = () => {
   }
 };
 
-app.whenReady().then(() => {
-  const expectedServerUrl = new URL(SERVER_BASE_URL);
-  const expectedServerOrigin = expectedServerUrl.origin;
-  const expectedServerHost = expectedServerUrl.hostname;
-  // `electron.net` 요청은 self-signed TLS에서 막히는 경우가 많아서,
-  // 특정 호스트(host)만 인증서 검증을 우회(bypass)합니다.
-  session.defaultSession.setCertificateVerifyProc((request, callback) => {
-    if (request.hostname === expectedServerHost) {
-      callback(0);
-      return;
-    }
+const gotTheLock = app.requestSingleInstanceLock();
 
-    callback(-3);
+if (!gotTheLock) {
+  console.log("[spt-launcher] Another instance is already running. Quitting...");
+  app.quit();
+} else {
+  app.on("second-instance", (event, commandLine, workingDirectory) => {
+    // Someone tried to run a second instance, we should focus our window.
+    const windows = BrowserWindow.getAllWindows();
+    if (windows.length > 0) {
+      const mainWindow = windows[0];
+      if (mainWindow.isMinimized()) mainWindow.restore();
+      mainWindow.focus();
+    }
   });
 
-  app.on(
-    "certificate-error",
-    (event, _webContents, url, _error, _certificate, callback) => {
-      if (url.startsWith(expectedServerOrigin)) {
-        event.preventDefault();
-        callback(true);
+  app.whenReady().then(() => {
+    const expectedServerUrl = new URL(SERVER_BASE_URL);
+    const expectedServerOrigin = expectedServerUrl.origin;
+    const expectedServerHost = expectedServerUrl.hostname;
+    // `electron.net` 요청은 self-signed TLS에서 막히는 경우가 많아서,
+    // 특정 호스트(host)만 인증서 검증을 우회(bypass)합니다.
+    session.defaultSession.setCertificateVerifyProc((request, callback) => {
+      if (request.hostname === expectedServerHost) {
+        callback(0);
         return;
       }
 
-      callback(false);
-    },
-  );
-
-  ipcMain.handle("spt:checkServerHealth", async () => {
-    return await checkServerHealth();
-  });
-
-  ipcMain.handle("spt:checkGitTools", async () => {
-    return await checkGitTools();
-  });
-
-  ipcMain.handle("spt:getGitPaths", async () => {
-    return await getGitPaths();
-  });
-
-  ipcMain.handle("spt:installGitTools", async (event) => {
-    return await installGitTools((step) => {
-      event.sender.send("spt:gitInstallProgress", step);
+      callback(-3);
     });
-  });
 
-  ipcMain.handle("spt:launchGame", async (event) => {
-    const mainWindow = BrowserWindow.fromWebContents(event.sender);
-    const installInfo = await resolveSptInstall();
-
-    if (!installInfo.path) {
-      return { ok: false, error: "no_spt_path" };
-    }
-
-    // Double check running processes
-    const running = await checkGameRunning();
-    if (running.clientRunning) {
-      return { ok: false, error: "already_running", details: running.processes };
-    }
-
-    // Double check mod version (optional but safer)
-    const modStatus = await getModVersionStatus();
-    if (!modStatus.ok) {
-      return { ok: false, error: "mod_verification_failed" };
-    }
-
-    // Launch Server if not running (Local only)
-    const serverUrl = new URL(SERVER_BASE_URL);
-    const isLocal = serverUrl.hostname === "127.0.0.1" || serverUrl.hostname === "localhost";
-
-    if (isLocal && !running.serverRunning) {
-      let serverExePath: string | undefined;
-      for (const exe of SERVER_PROCESS_NAMES) {
-        // Check direct path or SPT subdirectory
-        const direct = path.join(installInfo.path, exe);
-        if (await pathExists(direct)) {
-          serverExePath = direct;
-          break;
+    app.on(
+      "certificate-error",
+      (event, _webContents, url, _error, _certificate, callback) => {
+        if (url.startsWith(expectedServerOrigin)) {
+          event.preventDefault();
+          callback(true);
+          return;
         }
-        const nested = path.join(installInfo.path, "SPT", exe);
-        if (await pathExists(nested)) {
-          serverExePath = nested;
-          break;
+
+        callback(false);
+      },
+    );
+
+    ipcMain.handle("spt:checkServerHealth", async () => {
+      return await checkServerHealth();
+    });
+
+    ipcMain.handle("spt:checkGitTools", async () => {
+      return await checkGitTools();
+    });
+
+    ipcMain.handle("spt:getGitPaths", async () => {
+      return await getGitPaths();
+    });
+
+    ipcMain.handle("spt:installGitTools", async (event) => {
+      return await installGitTools((step) => {
+        event.sender.send("spt:gitInstallProgress", step);
+      });
+    });
+
+    ipcMain.handle("spt:launchGame", async (event) => {
+      const mainWindow = BrowserWindow.fromWebContents(event.sender);
+      const installInfo = await resolveSptInstall();
+
+      if (!installInfo.path) {
+        return { ok: false, error: "no_spt_path" };
+      }
+
+      // Double check running processes
+      const running = await checkGameRunning();
+      if (running.clientRunning) {
+        return { ok: false, error: "already_running", details: running.processes };
+      }
+
+      // Double check mod version (optional but safer)
+      const modStatus = await getModVersionStatus();
+      if (!modStatus.ok) {
+        return { ok: false, error: "mod_verification_failed" };
+      }
+
+      // Launch Server if not running (Local only)
+      const serverUrl = new URL(SERVER_BASE_URL);
+      const isLocal = serverUrl.hostname === "127.0.0.1" || serverUrl.hostname === "localhost";
+
+      if (isLocal && !running.serverRunning) {
+        let serverExePath: string | undefined;
+        for (const exe of SERVER_PROCESS_NAMES) {
+          // Check direct path or SPT subdirectory
+          const direct = path.join(installInfo.path, exe);
+          if (await pathExists(direct)) {
+            serverExePath = direct;
+            break;
+          }
+          const nested = path.join(installInfo.path, "SPT", exe);
+          if (await pathExists(nested)) {
+            serverExePath = nested;
+            break;
+          }
+        }
+
+        if (serverExePath) {
+          console.log(`[spt-launcher] Starting Server: ${serverExePath}`);
+          const serverBat = stripExe(serverExePath) + ".bat"; // Sometimes users use bat, but exe should work if arguments aren't complex
+
+          // Prefer EXE for now.
+          const child = require("child_process").spawn(serverExePath, [], {
+            cwd: path.dirname(serverExePath),
+            detached: true,
+            stdio: "ignore"
+          });
+          child.unref();
+
+          // Wait for server health
+          let attempts = 0;
+          const maxAttempts = 30; // 30 seconds approx
+          while (attempts < maxAttempts) {
+            const health = await checkServerHealth();
+            if (health.ok) {
+              break;
+            }
+            await new Promise(r => setTimeout(r, 1000));
+            attempts++;
+          }
         }
       }
 
-      if (serverExePath) {
-        console.log(`[spt-launcher] Starting Server: ${serverExePath}`);
-        const serverBat = stripExe(serverExePath) + ".bat"; // Sometimes users use bat, but exe should work if arguments aren't complex
+      // Launch Client
+      try {
+        // Prioritize EFT executable
+        const candidates = [
+          "EscapeFromTarkov.exe",
+          "EscapeFromTarkov_BE.exe",
+          "SPT/EscapeFromTarkov.exe",
+          "SPT/EscapeFromTarkov_BE.exe"
+        ];
 
-        // Prefer EXE for now.
-        const child = require("child_process").spawn(serverExePath, [], {
-          cwd: path.dirname(serverExePath),
+        let executablePath: string | undefined;
+        for (const exe of candidates) {
+          const fullPath = path.join(installInfo.path, exe);
+          if (await pathExists(fullPath)) {
+            executablePath = fullPath;
+            break;
+          }
+        }
+
+        if (!executablePath) {
+          return { ok: false, error: "executable_not_found" };
+        }
+
+        // Get Session ID for args
+        const session = await readSessionRecord();
+        if (!session || isSessionExpired(session)) {
+          return { ok: false, error: "session_required" };
+        }
+
+        // Build Args
+        const configArg = JSON.stringify({
+          BackendUrl: SERVER_BASE_URL,
+          Version: "live"
+        });
+        const args = [`-token=${session.sessionId}`, `-config=${configArg}`];
+        console.log(`[spt-launcher] Launching: ${executablePath} with args`, args);
+
+        // Sanitize Environment
+        // Strip Electron/Node specifics to prevent BepInEx/Plugin conflicts
+        const sanitizedEnv = { ...process.env };
+        for (const key of Object.keys(sanitizedEnv)) {
+          if (key.startsWith("ELECTRON_") || key.startsWith("NODE_") || key === "VITE_DEV_SERVER_URL") {
+            delete sanitizedEnv[key];
+          }
+        }
+
+        // Spawn detached
+        const child = require("child_process").spawn(executablePath, args, {
+          cwd: path.dirname(executablePath),
           detached: true,
-          stdio: "ignore"
+          stdio: "ignore",
+          env: sanitizedEnv
         });
         child.unref();
 
-        // Wait for server health
-        let attempts = 0;
-        const maxAttempts = 30; // 30 seconds approx
-        while (attempts < maxAttempts) {
-          const health = await checkServerHealth();
-          if (health.ok) {
-            break;
+        mainWindow?.minimize();
+        return { ok: true, executedPath: executablePath };
+      } catch (e: any) {
+        console.error("Launch failed", e);
+        return { ok: false, error: e.message };
+      }
+    });
+
+    function stripExe(filename: string) {
+      return filename.replace(/\.exe$/i, "");
+    }
+
+    ipcMain.handle("spt:checkGameRunning", async () => {
+      return await checkGameRunning();
+    });
+
+    ipcMain.handle("spt:getModVersionStatus", async () => {
+      return await getModVersionStatus();
+    });
+
+    ipcMain.handle(
+      "spt:setLocalModVersion",
+      async (_event, payload: { tag: string }) => {
+        const tag = payload.tag.trim();
+        if (!tag) {
+          return { ok: false, error: "empty_tag" };
+        }
+        const record = await writeModVersionRecord(tag);
+        return { ok: true, record };
+      },
+    );
+
+    ipcMain.handle(
+      "spt:runModSync",
+      async (
+        event,
+        payload: { targetDir: string; tag: string; cleanRepo?: boolean },
+      ) => {
+        return await runModSync(payload, (step) => {
+          event.sender.send("spt:modSyncProgress", step);
+        });
+      },
+    );
+
+    ipcMain.handle("spt:getSptInstallInfo", async () => {
+      return await resolveSptInstall();
+    });
+
+    ipcMain.handle(
+      "spt:setSptInstallPath",
+      async (_event, payload: { path: string; allowMissing?: boolean }) => {
+        let rawPath = payload.path?.trim();
+        if (!rawPath) {
+          return { ok: false, error: "empty_path" };
+        }
+
+        if (process.platform === "win32" && !payload.allowMissing) {
+          const resolved = await findSptInstallPath(rawPath);
+          if (!resolved) {
+            return { ok: false, error: "invalid_spt_path" };
           }
-          await new Promise(r => setTimeout(r, 1000));
-          attempts++;
+          rawPath = resolved;
         }
-      }
-    }
 
-    // Launch Client
-    try {
-      // Prioritize EFT executable
-      const candidates = [
-        "EscapeFromTarkov.exe",
-        "EscapeFromTarkov_BE.exe",
-        "SPT/EscapeFromTarkov.exe",
-        "SPT/EscapeFromTarkov_BE.exe"
-      ];
+        const record = await writeSptPathRecord({
+          path: rawPath,
+          allowMissing: payload.allowMissing,
+        });
+        return { ok: true, record };
+      },
+    );
 
-      let executablePath: string | undefined;
-      for (const exe of candidates) {
-        const fullPath = path.join(installInfo.path, exe);
-        if (await pathExists(fullPath)) {
-          executablePath = fullPath;
-          break;
-        }
+    ipcMain.handle("spt:pickSptInstallPath", async () => {
+      if (process.platform !== "win32") {
+        return { ok: false, error: "unsupported_platform" };
       }
 
-      if (!executablePath) {
-        return { ok: false, error: "executable_not_found" };
-      }
-
-      // Get Session ID for args
-      const session = await readSessionRecord();
-      if (!session || isSessionExpired(session)) {
-        return { ok: false, error: "session_required" };
-      }
-
-      // Build Args
-      const configArg = JSON.stringify({
-        BackendUrl: SERVER_BASE_URL,
-        Version: "live"
+      const result = await dialog.showOpenDialog({
+        title: "SPT 설치 폴더 선택",
+        properties: ["openDirectory"],
       });
-      const args = [`-token=${session.sessionId}`, `-config=${configArg}`];
-      console.log(`[spt-launcher] Launching: ${executablePath} with args`, args);
 
-      // Sanitize Environment
-      // Strip Electron/Node specifics to prevent BepInEx/Plugin conflicts
-      const sanitizedEnv = { ...process.env };
-      for (const key of Object.keys(sanitizedEnv)) {
-        if (key.startsWith("ELECTRON_") || key.startsWith("NODE_") || key === "VITE_DEV_SERVER_URL") {
-          delete sanitizedEnv[key];
-        }
+      if (result.canceled || result.filePaths.length === 0) {
+        return { ok: false, error: "cancelled" };
       }
 
-      // Spawn detached
-      const child = require("child_process").spawn(executablePath, args, {
-        cwd: path.dirname(executablePath),
-        detached: true,
-        stdio: "ignore",
-        env: sanitizedEnv
-      });
-      child.unref();
-
-      mainWindow?.minimize();
-      return { ok: true, executedPath: executablePath };
-    } catch (e: any) {
-      console.error("Launch failed", e);
-      return { ok: false, error: e.message };
-    }
-  });
-
-  function stripExe(filename: string) {
-    return filename.replace(/\.exe$/i, "");
-  }
-
-  ipcMain.handle("spt:checkGameRunning", async () => {
-    return await checkGameRunning();
-  });
-
-  ipcMain.handle("spt:getModVersionStatus", async () => {
-    return await getModVersionStatus();
-  });
-
-  ipcMain.handle(
-    "spt:setLocalModVersion",
-    async (_event, payload: { tag: string }) => {
-      const tag = payload.tag.trim();
-      if (!tag) {
-        return { ok: false, error: "empty_tag" };
-      }
-      const record = await writeModVersionRecord(tag);
-      return { ok: true, record };
-    },
-  );
-
-  ipcMain.handle(
-    "spt:runModSync",
-    async (
-      event,
-      payload: { targetDir: string; tag: string; cleanRepo?: boolean },
-    ) => {
-      return await runModSync(payload, (step) => {
-        event.sender.send("spt:modSyncProgress", step);
-      });
-    },
-  );
-
-  ipcMain.handle("spt:getSptInstallInfo", async () => {
-    return await resolveSptInstall();
-  });
-
-  ipcMain.handle(
-    "spt:setSptInstallPath",
-    async (_event, payload: { path: string; allowMissing?: boolean }) => {
-      let rawPath = payload.path?.trim();
-      if (!rawPath) {
-        return { ok: false, error: "empty_path" };
-      }
-
-      if (process.platform === "win32" && !payload.allowMissing) {
-        const resolved = await findSptInstallPath(rawPath);
-        if (!resolved) {
-          return { ok: false, error: "invalid_spt_path" };
-        }
-        rawPath = resolved;
+      const selected = result.filePaths[0];
+      const resolved = await findSptInstallPath(selected);
+      if (!resolved) {
+        return { ok: false, error: "invalid_spt_path", path: selected };
       }
 
       const record = await writeSptPathRecord({
-        path: rawPath,
-        allowMissing: payload.allowMissing,
+        path: resolved,
+        allowMissing: false,
       });
       return { ok: true, record };
-    },
-  );
-
-  ipcMain.handle("spt:pickSptInstallPath", async () => {
-    if (process.platform !== "win32") {
-      return { ok: false, error: "unsupported_platform" };
-    }
-
-    const result = await dialog.showOpenDialog({
-      title: "SPT 설치 폴더 선택",
-      properties: ["openDirectory"],
     });
 
-    if (result.canceled || result.filePaths.length === 0) {
-      return { ok: false, error: "cancelled" };
-    }
+    ipcMain.handle(
+      "spt:register",
+      async (_event, payload: { username: string; password?: string }) => {
+        const username = payload.username.trim();
+        const password = payload.password?.trim();
+        return await registerProfile(username, password);
+      }
+    );
 
-    const selected = result.filePaths[0];
-    const resolved = await findSptInstallPath(selected);
-    if (!resolved) {
-      return { ok: false, error: "invalid_spt_path", path: selected };
-    }
+    ipcMain.handle(
+      "spt:login",
+      async (_event, payload: { username: string; password?: string }) => {
+        const username = payload.username.trim();
+        const password = payload.password?.trim();
 
-    const record = await writeSptPathRecord({
-      path: resolved,
-      allowMissing: false,
-    });
-    return { ok: true, record };
-  });
-
-  ipcMain.handle(
-    "spt:fetchProfile",
-    async (_event, payload: { username: string }) => {
-      const username = payload.username.trim();
-      let activeSessionId: string | undefined;
-
-      const fetchProfileInfo = async (): Promise<{
-        ok: boolean;
-        status?: number;
-        data?: unknown;
-        error?: string;
-        url: string;
-      }> => {
-        const sessionResult = await getSessionIdForUser(username);
+        const sessionResult = await getSessionIdForUser(username, password);
         if (!sessionResult.ok) {
-          return {
-            ok: false,
-            error: sessionResult.error ?? "login_failed",
-            url: sessionResult.url,
-          };
+          return sessionResult;
         }
-        activeSessionId = sessionResult.sessionId;
+
+        await writeSessionRecord({ username, sessionId: sessionResult.sessionId });
 
         return await postJson(
           "/launcher/profile/info",
@@ -1716,191 +1747,225 @@ app.whenReady().then(() => {
             Cookie: `PHPSESSID=${sessionResult.sessionId}`,
           },
         );
-      };
-
-      let infoResult = await fetchProfileInfo();
-      if (!infoResult.ok && isSessionInvalidStatus(infoResult.status)) {
-        const relogin = await requestSessionId(username);
-        if (!relogin.ok) {
-          return {
-            ok: false,
-            error: relogin.error ?? "login_failed",
-            url: relogin.url,
-          };
-        }
-        await writeSessionRecord({ username, sessionId: relogin.sessionId });
-        activeSessionId = relogin.sessionId;
-        infoResult = await postJson(
-          "/launcher/profile/info",
-          { username },
-          {
-            Cookie: `PHPSESSID=${relogin.sessionId}`,
-          },
-        );
       }
-      if (infoResult.ok && infoResult.data) {
-        if (activeSessionId) {
-          await refreshSessionRecord({ username, sessionId: activeSessionId });
+    );
+
+    ipcMain.handle(
+      "spt:fetchProfile",
+      async (_event, payload: { username: string; password?: string }) => {
+        const username = payload.username.trim();
+        const password = payload.password?.trim();
+        let activeSessionId: string | undefined;
+
+        const fetchProfileInfo = async (): Promise<{
+          ok: boolean;
+          status?: number;
+          data?: unknown;
+          error?: string;
+          url: string;
+        }> => {
+          const sessionResult = await getSessionIdForUser(username, password);
+          if (!sessionResult.ok) {
+            return {
+              ok: false,
+              error: sessionResult.error ?? "login_failed",
+              url: sessionResult.url,
+            };
+          }
+          activeSessionId = sessionResult.sessionId;
+
+          return await postJson(
+            "/launcher/profile/info",
+            { username },
+            {
+              Cookie: `PHPSESSID=${sessionResult.sessionId}`,
+            },
+          );
+        };
+
+        let infoResult = await fetchProfileInfo();
+        if (!infoResult.ok && isSessionInvalidStatus(infoResult.status)) {
+          const relogin = await requestSessionId(username, password);
+          if (!relogin.ok) {
+            return {
+              ok: false,
+              error: relogin.error ?? "login_failed",
+              url: relogin.url,
+            };
+          }
+          await writeSessionRecord({ username, sessionId: relogin.sessionId });
+          activeSessionId = relogin.sessionId;
+          infoResult = await postJson(
+            "/launcher/profile/info",
+            { username },
+            {
+              Cookie: `PHPSESSID=${relogin.sessionId}`,
+            },
+          );
         }
+        if (infoResult.ok && infoResult.data) {
+          if (activeSessionId) {
+            await refreshSessionRecord({ username, sessionId: activeSessionId });
+          }
+          return infoResult;
+        }
+
         return infoResult;
-      }
-
-      await registerProfile(username);
-      return await fetchProfileInfo();
-    },
-  );
-
-  ipcMain.handle(
-    "spt:downloadProfile",
-    async (_event, payload: { username: string }) => {
-      const username = payload.username.trim();
-
-      const sessionResult = await getSessionIdForUser(username);
-      if (!sessionResult.ok) {
-        return sessionResult;
-      }
-
-      let activeSessionId = sessionResult.sessionId;
-      let infoResult = await postJson(
-        "/launcher/profile/info",
-        { username },
-        {
-          Cookie: `PHPSESSID=${sessionResult.sessionId}`,
-        },
-      );
-
-      if (!infoResult.ok && isSessionInvalidStatus(infoResult.status)) {
-        const relogin = await requestSessionId(username);
-        if (!relogin.ok) {
-          return relogin;
-        }
-        await writeSessionRecord({ username, sessionId: relogin.sessionId });
-        activeSessionId = relogin.sessionId;
-        infoResult = await postJson(
-          "/launcher/profile/info",
-          { username },
-          {
-            Cookie: `PHPSESSID=${relogin.sessionId}`,
-          },
-        );
-      }
-
-      if (!infoResult.ok || !infoResult.data) {
-        return infoResult;
-      }
-
-      await refreshSessionRecord({ username, sessionId: activeSessionId });
-
-      const downloadsDir = app.getPath("downloads");
-      const fileName = `spt-profile-${username}-${Date.now()}.json`;
-      const filePath = path.join(downloadsDir, fileName);
-
-      await fs.writeFile(
-        filePath,
-        JSON.stringify(infoResult.data, null, 2),
-        "utf8",
-      );
-
-      return {
-        ok: true,
-        status: infoResult.status,
-        url: infoResult.url,
-        filePath,
-      };
-    },
-  );
-
-  ipcMain.handle(
-    "spt:resetProfile",
-    async (_event, payload: { username: string }) => {
-      const username = payload.username.trim();
-
-      const sessionResult = await getSessionIdForUser(username);
-      if (!sessionResult.ok) {
-        return sessionResult;
-      }
-
-      let activeSessionId = sessionResult.sessionId;
-      let wipeResult = await postJson(
-        "/launcher/profile/change/wipe",
-        { username },
-        {
-          Cookie: `PHPSESSID=${sessionResult.sessionId}`,
-        },
-      );
-
-      if (!wipeResult.ok && isSessionInvalidStatus(wipeResult.status)) {
-        const relogin = await requestSessionId(username);
-        if (!relogin.ok) {
-          return relogin;
-        }
-        await writeSessionRecord({ username, sessionId: relogin.sessionId });
-        activeSessionId = relogin.sessionId;
-        wipeResult = await postJson(
-          "/launcher/profile/change/wipe",
-          { username },
-          {
-            Cookie: `PHPSESSID=${relogin.sessionId}`,
-          },
-        );
-      }
-
-      if (wipeResult.ok) {
-        await refreshSessionRecord({ username, sessionId: activeSessionId });
-      }
-      return wipeResult;
-    },
-  );
-
-  ipcMain.handle("spt:resumeSession", async () => {
-    const record = await readSessionRecord();
-    if (!record || isSessionExpired(record)) {
-      await clearSessionRecord();
-      return { ok: false, error: "session_expired", url: SERVER_BASE_URL };
-    }
-
-    const infoResult = await postJson(
-      "/launcher/profile/info",
-      { username: record.username },
-      {
-        Cookie: `PHPSESSID=${record.sessionId}`,
       },
     );
 
-    if (!infoResult.ok && isSessionInvalidStatus(infoResult.status)) {
+    ipcMain.handle(
+      "spt:downloadProfile",
+      async (_event, payload: { username: string }) => {
+        const username = payload.username.trim();
+
+        const sessionResult = await getSessionIdForUser(username);
+        if (!sessionResult.ok) {
+          return sessionResult;
+        }
+
+        let activeSessionId = sessionResult.sessionId;
+        let infoResult = await postJson(
+          "/launcher/profile/info",
+          { username },
+          {
+            Cookie: `PHPSESSID=${sessionResult.sessionId}`,
+          },
+        );
+
+        if (!infoResult.ok && isSessionInvalidStatus(infoResult.status)) {
+          const relogin = await requestSessionId(username);
+          if (!relogin.ok) {
+            return relogin;
+          }
+          await writeSessionRecord({ username, sessionId: relogin.sessionId });
+          activeSessionId = relogin.sessionId;
+          infoResult = await postJson(
+            "/launcher/profile/info",
+            { username },
+            {
+              Cookie: `PHPSESSID=${relogin.sessionId}`,
+            },
+          );
+        }
+
+        if (!infoResult.ok || !infoResult.data) {
+          return infoResult;
+        }
+
+        await refreshSessionRecord({ username, sessionId: activeSessionId });
+
+        const downloadsDir = app.getPath("downloads");
+        const fileName = `spt-profile-${username}-${Date.now()}.json`;
+        const filePath = path.join(downloadsDir, fileName);
+
+        await fs.writeFile(
+          filePath,
+          JSON.stringify(infoResult.data, null, 2),
+          "utf8",
+        );
+
+        return {
+          ok: true,
+          status: infoResult.status,
+          url: infoResult.url,
+          filePath,
+        };
+      },
+    );
+
+    ipcMain.handle(
+      "spt:resetProfile",
+      async (_event, payload: { username: string }) => {
+        const username = payload.username.trim();
+
+        const sessionResult = await getSessionIdForUser(username);
+        if (!sessionResult.ok) {
+          return sessionResult;
+        }
+
+        let activeSessionId = sessionResult.sessionId;
+        let wipeResult = await postJson(
+          "/launcher/profile/change/wipe",
+          { username },
+          {
+            Cookie: `PHPSESSID=${sessionResult.sessionId}`,
+          },
+        );
+
+        if (!wipeResult.ok && isSessionInvalidStatus(wipeResult.status)) {
+          const relogin = await requestSessionId(username);
+          if (!relogin.ok) {
+            return relogin;
+          }
+          await writeSessionRecord({ username, sessionId: relogin.sessionId });
+          activeSessionId = relogin.sessionId;
+          wipeResult = await postJson(
+            "/launcher/profile/change/wipe",
+            { username },
+            {
+              Cookie: `PHPSESSID=${relogin.sessionId}`,
+            },
+          );
+        }
+
+        if (wipeResult.ok) {
+          await refreshSessionRecord({ username, sessionId: activeSessionId });
+        }
+        return wipeResult;
+      },
+    );
+
+    ipcMain.handle("spt:resumeSession", async () => {
+      const record = await readSessionRecord();
+      if (!record || isSessionExpired(record)) {
+        await clearSessionRecord();
+        return { ok: false, error: "session_expired", url: SERVER_BASE_URL };
+      }
+
+      const infoResult = await postJson(
+        "/launcher/profile/info",
+        { username: record.username },
+        {
+          Cookie: `PHPSESSID=${record.sessionId}`,
+        },
+      );
+
+      if (!infoResult.ok && isSessionInvalidStatus(infoResult.status)) {
+        await clearSessionRecord();
+        return { ok: false, error: "session_expired", url: infoResult.url };
+      }
+
+      if (infoResult.ok) {
+        await refreshSessionRecord({
+          username: record.username,
+          sessionId: record.sessionId,
+        });
+      }
+      return infoResult;
+    });
+
+    ipcMain.handle("spt:clearSession", async () => {
       await clearSessionRecord();
-      return { ok: false, error: "session_expired", url: infoResult.url };
-    }
+      return { ok: true };
+    });
 
-    if (infoResult.ok) {
-      await refreshSessionRecord({
-        username: record.username,
-        sessionId: record.sessionId,
-      });
-    }
-    return infoResult;
+    // 개발/운영 모두에서 부팅 시 1회 즉시 체크(instant check) 로그를 남겨
+    // 엔드포인트(endpoint) 확인이 가능하도록 합니다.
+    void checkServerHealth();
+
+    createWindow();
+
+    app.on("activate", () => {
+      if (BrowserWindow.getAllWindows().length === 0) {
+        createWindow();
+      }
+    });
   });
 
-  ipcMain.handle("spt:clearSession", async () => {
-    await clearSessionRecord();
-    return { ok: true };
-  });
-
-  // 개발/운영 모두에서 부팅 시 1회 즉시 체크(instant check) 로그를 남겨
-  // 엔드포인트(endpoint) 확인이 가능하도록 합니다.
-  void checkServerHealth();
-
-  createWindow();
-
-  app.on("activate", () => {
-    if (BrowserWindow.getAllWindows().length === 0) {
-      createWindow();
+  app.on("window-all-closed", () => {
+    if (process.platform !== "darwin") {
+      app.quit();
     }
   });
-});
-
-app.on("window-all-closed", () => {
-  if (process.platform !== "darwin") {
-    app.quit();
-  }
-});
+}
diff --git a/src/preload/preload.ts b/src/preload/preload.ts
index 025928d..0289e83 100644
--- a/src/preload/preload.ts
+++ b/src/preload/preload.ts
@@ -19,7 +19,11 @@ contextBridge.exposeInMainWorld("sptLauncher", {
   setSptInstallPath: (payload: { path: string; allowMissing?: boolean }) =>
     ipcRenderer.invoke("spt:setSptInstallPath", payload),
   pickSptInstallPath: () => ipcRenderer.invoke("spt:pickSptInstallPath"),
-  fetchProfile: (payload: { username: string }) =>
+  login: (payload: { username: string; password?: string }) =>
+    ipcRenderer.invoke("spt:login", payload),
+  register: (payload: { username: string; password?: string }) =>
+    ipcRenderer.invoke("spt:register", payload),
+  fetchProfile: (payload: { username: string; password?: string }) =>
     ipcRenderer.invoke("spt:fetchProfile", payload),
   downloadProfile: (payload: { username: string }) =>
     ipcRenderer.invoke("spt:downloadProfile", payload),
diff --git a/src/renderer/App.tsx b/src/renderer/App.tsx
index e8cfead..d9d6d94 100644
--- a/src/renderer/App.tsx
+++ b/src/renderer/App.tsx
@@ -74,6 +74,9 @@ const App = () => {
   const [hasSession, setHasSession] = useState(false);
   const [loginId, setLoginId] = useState("");
   const [loginPassword, setLoginPassword] = useState("");
+  const [signupId, setSignupId] = useState("");
+  const [signupPassword, setSignupPassword] = useState("");
+  const [confirmPassword, setConfirmPassword] = useState("");
   const [profileLoading, setProfileLoading] = useState(false);
   const [profile, setProfile] = useState<{
     username: string;
@@ -169,8 +172,8 @@ const App = () => {
     value && typeof value === "object" ? (value as Record<string, unknown>) : undefined;
   const pickString = (...values: unknown[]) =>
     values.find((value) => typeof value === "string" && value.trim().length > 0) as
-      | string
-      | undefined;
+    | string
+    | undefined;
   const pickNumber = (...values: unknown[]) => {
     const candidate = values.find(
       (value) => typeof value === "number" || (typeof value === "string" && value.trim() !== "")
@@ -496,18 +499,31 @@ const App = () => {
 
     sessionResumeAttemptedRef.current = true;
     void (async () => {
-      const result = await window.sptLauncher.resumeSession();
-      if (!result.ok || !result.data) {
-        return;
+      try {
+        const result = await window.sptLauncher.resumeSession();
+        if (!result.ok || !result.data) {
+          scheduleScreenTransition("login");
+          return;
+        }
+
+        const resumedProfile = extractProfile(result.data, loginId.trim());
+        // Simple validation: profile must have an ID or Username to be considered valid
+        if (!resumedProfile.id && !resumedProfile.username) {
+          scheduleScreenTransition("login");
+          return;
+        }
+
+        setProfile(resumedProfile);
+        setHasSession(true);
+        if (resumedProfile.username) {
+          setLoginId(resumedProfile.username);
+        }
+        clearTransitionTimeout();
+        setScreen("main");
+      } catch (error) {
+        console.error("Session resume failed", error);
+        scheduleScreenTransition("login");
       }
-      const resumedProfile = extractProfile(result.data, loginId.trim());
-      setProfile(resumedProfile);
-      setHasSession(true);
-      if (resumedProfile.username) {
-        setLoginId(resumedProfile.username);
-      }
-      clearTransitionTimeout();
-      setScreen("main");
     })();
   }, [
     screen,
@@ -815,28 +831,30 @@ const App = () => {
 
   const handleLogin = async () => {
     const trimmedId = loginId.trim();
+    const trimmedPassword = loginPassword.trim();
     if (!trimmedId) {
       window.alert("아이디를 입력해주세요.");
       return;
     }
 
-    if (!window.sptLauncher?.fetchProfile) {
-      window.alert("프로필 조회 기능이 준비되지 않았습니다.");
+    if (!window.sptLauncher?.login) {
+      window.alert("로그인 기능이 준비되지 않았습니다.");
       return;
     }
 
     setProfileLoading(true);
 
     try {
-      const result = await window.sptLauncher.fetchProfile({
-        username: trimmedId
+      const result = await window.sptLauncher.login({
+        username: trimmedId,
+        password: trimmedPassword
       });
       if (!result.ok) {
         if (isTimeoutError(result.error)) {
           enterRecoveryMode("timeout");
           return;
         }
-        window.alert(result.error ?? "프로필 조회에 실패했습니다.");
+        window.alert(result.error ?? "로그인에 실패했습니다.");
         return;
       }
 
@@ -860,9 +878,51 @@ const App = () => {
     }
   };
 
-  const handleSignup = () => {
-    window.alert("회원가입 요청이 접수되었습니다. 관리자 승인 후 이용 가능합니다.");
-    setScreen("login");
+  const handleSignup = async () => {
+    const trimmedId = signupId.trim();
+    const trimmedPassword = signupPassword.trim();
+    const trimmedConfirm = confirmPassword.trim();
+
+    if (!trimmedId) {
+      window.alert("아이디를 입력해주세요.");
+      return;
+    }
+    if (!trimmedPassword) {
+      window.alert("비밀번호를 입력해주세요.");
+      return;
+    }
+    if (trimmedPassword !== trimmedConfirm) {
+      window.alert("비밀번호가 일치하지 않습니다.");
+      return;
+    }
+
+    if (!window.sptLauncher?.register) {
+      window.alert("회원가입 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    setProfileLoading(true);
+    try {
+      const result = await window.sptLauncher.register({
+        username: trimmedId,
+        password: trimmedPassword
+      });
+
+      if (!result.ok) {
+        window.alert(result.error ?? "회원가입 요청에 실패했습니다.");
+        return;
+      }
+
+      window.alert("회원가입이 완료되었습니다. 이제 로그인할 수 있습니다.");
+      setLoginId(trimmedId);
+      setLoginPassword(trimmedPassword);
+      setScreen("login");
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      window.alert(message);
+    } finally {
+      setProfileLoading(false);
+    }
   };
 
   const handlePasswordReset = () => {
@@ -1037,42 +1097,42 @@ const App = () => {
       // Subscribe to progress events
       const cleanup = window.sptLauncher.onModSyncProgress
         ? window.sptLauncher.onModSyncProgress((_event, step) => {
-            // eslint-disable-next-line @typescript-eslint/no-explicit-any
-            const s = step as any;
-            const uiStep = {
-              name: s.name,
-              ok: s.result?.ok ?? false,
-              message: s.result?.ok ? undefined : s.result?.message ?? s.result?.error,
-              status: s.result?.ok ? "done" : "error"
-            };
-            upsertSyncStep(uiStep);
-          })
-        : () => {};
+          // eslint-disable-next-line @typescript-eslint/no-explicit-any
+          const s = step as any;
+          const uiStep = {
+            name: s.name,
+            ok: s.result?.ok ?? false,
+            message: s.result?.ok ? undefined : s.result?.message ?? s.result?.error,
+            status: (s.result?.ok ? "done" : "error") as "done" | "error"
+          };
+          upsertSyncStep(uiStep);
+        })
+        : () => { };
 
       try {
         const result = await window.sptLauncher.runModSync({
           targetDir,
           tag: targetTag
         });
-        
+
         cleanup(); // Unsubscribe
 
         if (!result.ok) {
-           setSyncResult({ ok: false, error: result.error ?? "모드 동기화에 실패했습니다." });
-           // If steps are returned in result (history), use them?
-           // The real-time listener should have captured them, but let's ensure we have full list
-           if (result.steps) {
-             setSyncSteps(
-               result.steps.map((s) => ({
-                 name: s.name,
-                 ok: s.ok,
-                 message: s.ok ? undefined : s.message,
-                 status: s.ok ? "done" : "error"
-               }))
-             );
-           }
-           setModCheckMessage(result.error ?? "모드 동기화에 실패했습니다.");
-           return false;
+          setSyncResult({ ok: false, error: result.error ?? "모드 동기화에 실패했습니다." });
+          // If steps are returned in result (history), use them?
+          // The real-time listener should have captured them, but let's ensure we have full list
+          if (result.steps) {
+            setSyncSteps(
+              result.steps.map((s) => ({
+                name: s.name,
+                ok: s.ok,
+                message: s.ok ? undefined : s.message,
+                status: s.ok ? "done" : "error"
+              }))
+            );
+          }
+          setModCheckMessage(result.error ?? "모드 동기화에 실패했습니다.");
+          return false;
         }
 
         setSyncResult({ ok: true });
@@ -1109,7 +1169,7 @@ const App = () => {
 
   const closeSyncModal = () => {
     if (syncInProgress) {
-        return; // Cannot close while running
+      return; // Cannot close while running
     }
     setSyncResult(undefined);
     setSyncSteps([]);
@@ -1130,31 +1190,31 @@ const App = () => {
     }
 
     if (!window.sptLauncher?.launchGame) {
-       window.alert("게임 시작 기능이 준비되지 않았습니다.");
-       return;
+      window.alert("게임 시작 기능이 준비되지 않았습니다.");
+      return;
     }
 
     try {
-        const result = await window.sptLauncher.launchGame();
-        if (!result.ok) {
-            if (result.error === "already_running") {
-                 window.alert(`게임이 이미 실행 중입니다.\n(발견된 프로세스: ${(result.details ?? []).join(", ")})`);
-            } else if (result.error === "mod_verification_failed") {
-                 window.alert("모드 버전 검증에 실패했습니다. 버전을 다시 확인해주세요.");
-            } else if (result.error === "no_spt_path") {
-                 window.alert("SPT 설치 경로가 설정되지 않았습니다.");
-            } else if (result.error === "executable_not_found") {
-                 window.alert("실행 파일(Launcher/Server)을 찾을 수 없습니다.");
-            } else {
-                 window.alert(`게임 실행 실패: ${result.error}`);
-            }
-            return;
+      const result = await window.sptLauncher.launchGame();
+      if (!result.ok) {
+        if (result.error === "already_running") {
+          window.alert(`게임이 이미 실행 중입니다.\n(발견된 프로세스: ${(result.details ?? []).join(", ")})`);
+        } else if (result.error === "mod_verification_failed") {
+          window.alert("모드 버전 검증에 실패했습니다. 버전을 다시 확인해주세요.");
+        } else if (result.error === "no_spt_path") {
+          window.alert("SPT 설치 경로가 설정되지 않았습니다.");
+        } else if (result.error === "executable_not_found") {
+          window.alert("실행 파일(Launcher/Server)을 찾을 수 없습니다.");
+        } else {
+          window.alert(`게임 실행 실패: ${result.error}`);
         }
-        
-        // Success
-        window.alert(`게임이 실행되었습니다.\n(${result.executedPath})`);
+        return;
+      }
+
+      // Success
+      window.alert(`게임이 실행되었습니다.\n(${result.executedPath})`);
     } catch (e: any) {
-        window.alert(`게임 실행 중 오류가 발생했습니다: ${e.message}`);
+      window.alert(`게임 실행 중 오류가 발생했습니다: ${e.message}`);
     }
   };
 
@@ -1312,12 +1372,27 @@ const App = () => {
             회원가입 후 서버 관리자 승인이 완료되어야 로그인 가능합니다.
           </p>
           <div className="login-form">
-            <input type="text" placeholder="아이디" />
-            <input type="password" placeholder="비밀번호" />
-            <input type="password" placeholder="비밀번호 확인" />
+            <input
+              type="text"
+              placeholder="아이디"
+              value={signupId}
+              onChange={(e) => setSignupId(e.target.value)}
+            />
+            <input
+              type="password"
+              placeholder="비밀번호"
+              value={signupPassword}
+              onChange={(e) => setSignupPassword(e.target.value)}
+            />
+            <input
+              type="password"
+              placeholder="비밀번호 확인"
+              value={confirmPassword}
+              onChange={(e) => setConfirmPassword(e.target.value)}
+            />
           </div>
-          <button type="button" onClick={handleSignup}>
-            회원가입 요청
+          <button type="button" onClick={handleSignup} disabled={profileLoading}>
+            {profileLoading ? "가입 요청 중..." : "회원가입 요청"}
           </button>
           <button type="button" className="ghost" onClick={() => setScreen("login")}>
             로그인으로 돌아가기
@@ -1381,114 +1456,114 @@ const App = () => {
           <section className="card spt-runner-card">
             <div className="section-head">
               <h2>SPT 설정</h2>
-               <button 
-                  type="button" 
-                  className="launch-button-header"
-                  onClick={handleLaunch} 
-                  disabled={!startReady}
-               >
-                  <span className="launch-icon">🚀</span>
-                  <div className="launch-info">
-                    <span className="launch-text">{syncInProgress ? "동기화 중..." : "게임 시작"}</span>
-                    {/* <span className="launch-sub">Server & Launcher</span> */}
-                  </div>
-               </button>
+              <button
+                type="button"
+                className="launch-button-header"
+                onClick={handleLaunch}
+                disabled={!startReady}
+              >
+                <span className="launch-icon">🚀</span>
+                <div className="launch-info">
+                  <span className="launch-text">{syncInProgress ? "동기화 중..." : "게임 시작"}</span>
+                  {/* <span className="launch-sub">Server & Launcher</span> */}
+                </div>
+              </button>
             </div>
-            
+
             <div className="spt-rows-container">
               {/* Install Path Row */}
               <div className="spt-row">
-                 <div className="row-header">
-                    <span className="label">설치 경로</span>
-                    <span className={`status ${sptInstallInfo?.ok ? "ok" : "blocked"}`}>
-                      {sptInstallInfo?.ok ? "확인됨" : "확인 필요"}
+                <div className="row-header">
+                  <span className="label">설치 경로</span>
+                  <span className={`status ${sptInstallInfo?.ok ? "ok" : "blocked"}`}>
+                    {sptInstallInfo?.ok ? "확인됨" : "확인 필요"}
+                  </span>
+                </div>
+                <div className="row-body">
+                  <span className="value" title={sptInstallInfo?.path}>{sptInstallInfo?.path ?? "-"}</span>
+                  {sptInstallInfo?.source && (
+                    <span className="sub-helper">
+                      ({sptInstallInfo.source === "auto" ? "자동" : "수동"})
                     </span>
-                 </div>
-                 <div className="row-body">
-                    <span className="value" title={sptInstallInfo?.path}>{sptInstallInfo?.path ?? "-"}</span>
-                    {sptInstallInfo?.source && (
-                      <span className="sub-helper">
-                        ({sptInstallInfo.source === "auto" ? "자동" : "수동"})
-                      </span>
-                    )}
-                 </div>
-                 <div className="row-controls">
-                    <button
-                      type="button"
-                      className="ghost icon-button"
-                      onClick={async () => {
-                        if (!window.sptLauncher?.pickSptInstallPath) {
-                          window.alert("준비 안됨");
-                          return;
-                        }
-                        const result = await window.sptLauncher.pickSptInstallPath();
-                        if (!result.ok && result.error === "invalid_spt_path") {
-                          setSptInstallMessage("유효하지 않은 SPT 폴더입니다.");
-                          return;
-                        }
-                        setSptInstallMessage(undefined);
-                        await runSptInstallCheck();
-                      }}
-                      title="경로 변경"
-                    >
-                      📂
-                    </button>
-                    <button type="button" className="ghost" onClick={runSptInstallCheck}>
-                      재확인
-                    </button>
-                 </div>
+                  )}
+                </div>
+                <div className="row-controls">
+                  <button
+                    type="button"
+                    className="ghost icon-button"
+                    onClick={async () => {
+                      if (!window.sptLauncher?.pickSptInstallPath) {
+                        window.alert("준비 안됨");
+                        return;
+                      }
+                      const result = await window.sptLauncher.pickSptInstallPath();
+                      if (!result.ok && result.error === "invalid_spt_path") {
+                        setSptInstallMessage("유효하지 않은 SPT 폴더입니다.");
+                        return;
+                      }
+                      setSptInstallMessage(undefined);
+                      await runSptInstallCheck();
+                    }}
+                    title="경로 변경"
+                  >
+                    📂
+                  </button>
+                  <button type="button" className="ghost" onClick={runSptInstallCheck}>
+                    재확인
+                  </button>
+                </div>
               </div>
 
               {/* Mod Version Row */}
               <div className="spt-row">
-                 <div className="row-header">
-                    <span className="label">모드 버전</span>
-                    <span className={`status ${modStatusClass}`}>{modStatusLabel}</span>
-                 </div>
-                 <div className="row-body">
-                    <span className="value">
-                      {modVersionStatus?.currentTag ?? "-"} → {modVersionStatus?.latestTag ?? "-"}
+                <div className="row-header">
+                  <span className="label">모드 버전</span>
+                  <span className={`status ${modStatusClass}`}>{modStatusLabel}</span>
+                </div>
+                <div className="row-body">
+                  <span className="value">
+                    {modVersionStatus?.currentTag ?? "-"} → {modVersionStatus?.latestTag ?? "-"}
+                  </span>
+                  {modVersionStatus?.latestMinorTags && modVersionStatus.latestMinorTags.length > 0 && (
+                    <span className="sub-helper">
+                      (+{modVersionStatus.latestMinorTags.length} 패치)
                     </span>
-                    {modVersionStatus?.latestMinorTags && modVersionStatus.latestMinorTags.length > 0 && (
-                       <span className="sub-helper">
-                         (+{modVersionStatus.latestMinorTags.length} 패치)
-                       </span>
-                    )}
-                 </div>
-                 <div className="row-controls">
-                    <select
-                      value={selectedModTag}
-                      onChange={(event) => setSelectedModTag(event.target.value)}
-                      disabled={modTagOptions.length === 0 || syncInProgress}
-                      className="version-select"
-                    >
-                       <option value="">선택...</option>
-                      {modTagOptions.map((tag) => (
-                        <option key={tag} value={tag}>{tag}</option>
-                      ))}
-                    </select>
+                  )}
+                </div>
+                <div className="row-controls">
+                  <select
+                    value={selectedModTag}
+                    onChange={(event) => setSelectedModTag(event.target.value)}
+                    disabled={modTagOptions.length === 0 || syncInProgress}
+                    className="version-select"
+                  >
+                    <option value="">선택...</option>
+                    {modTagOptions.map((tag) => (
+                      <option key={tag} value={tag}>{tag}</option>
+                    ))}
+                  </select>
+                  <button
+                    type="button"
+                    className="ghost"
+                    onClick={() => performModSync("optional", selectedModTag)}
+                    disabled={syncInProgress || !selectedModTag}
+                    title="선택 버전 적용"
+                  >
+                    적용
+                  </button>
+                  <div className="sync-menu">
                     <button
                       type="button"
-                      className="ghost"
-                      onClick={() => performModSync("optional", selectedModTag)}
-                      disabled={syncInProgress || !selectedModTag}
-                      title="선택 버전 적용"
+                      className="ghost icon-button"
+                      onClick={() => performModSync("optional")}
+                      disabled={syncInProgress || !modVersionStatus?.latestTag}
+                      title="최신 동기화"
                     >
-                      적용
+                      ⟳
                     </button>
-                    <div className="sync-menu">
-                      <button
-                        type="button"
-                        className="ghost icon-button"
-                        onClick={() => performModSync("optional")}
-                        disabled={syncInProgress || !modVersionStatus?.latestTag}
-                        title="최신 동기화"
-                      >
-                        ⟳
-                      </button>
-                       {/* Hover menu logic handled by CSS usually, keeping simple for now */}
-                    </div>
-                 </div>
+                    {/* Hover menu logic handled by CSS usually, keeping simple for now */}
+                  </div>
+                </div>
               </div>
             </div>
 
@@ -1506,19 +1581,19 @@ const App = () => {
 
           <footer className="footer">
             <div className="tool-led">
-                <span className="tool-label">서버</span>
-                <span className={`led ${serverStatusLedClass}`} aria-label="서버 상태" />
+              <span className="tool-label">서버</span>
+              <span className={`led ${serverStatusLedClass}`} aria-label="서버 상태" />
             </div>
             <div className="tool-led">
-                <span className="tool-label">Git</span>
-                <span className={`led ${gitLedClass}`} aria-label="Git 상태" />
+              <span className="tool-label">Git</span>
+              <span className={`led ${gitLedClass}`} aria-label="Git 상태" />
             </div>
             <div className="tool-led">
-                <span className="tool-label">LFS</span>
-                <span className={`led ${lfsLedClass}`} aria-label="Git LFS 상태" />
+              <span className="tool-label">LFS</span>
+              <span className={`led ${lfsLedClass}`} aria-label="Git LFS 상태" />
             </div>
             <button type="button" className="ghost status-button" onClick={handleOpenToolsModal}>
-                상세 보기
+              상세 보기
             </button>
           </footer>
         </main>
@@ -1566,7 +1641,7 @@ const App = () => {
                   </div>
                 </div>
               )}
-            {installMessage && <div className="notice">{installMessage}</div>}
+              {installMessage && <div className="notice">{installMessage}</div>}
               {gitPathsResult && (
                 <div className="notice">
                   <strong>경로 확인</strong>
@@ -1583,73 +1658,73 @@ const App = () => {
 
       {(syncInProgress || syncResult) && (
         <div className="modal-overlay" role="presentation">
-             <section className="modal" onClick={(e) => e.stopPropagation()}>
-                <header className="modal-header">
-                   <h3>
-                     {syncResult 
-                       ? (syncResult.ok ? (modalTitle.replace("중...", "완료")) : (syncResult.error ? `오류: ${syncResult.error}` : "오류 발생")) 
-                       : modalTitle}
-                   </h3>
-                   {!syncInProgress && (
-                      <button type="button" className="ghost" onClick={closeSyncModal}>
-                        닫기
-                      </button>
-                   )}
-                </header>
-                <div className="modal-body">
-                   {syncProgress?.progress && (
-                     <div className="sync-progress">
-                       <div className="sync-progress-header">
-                         <span>진행률(Progress)</span>
-                         <span>{syncProgress.progress.percent}%</span>
-                       </div>
-                       <div className="sync-progress-bar">
-                         <div
-                           className="sync-progress-fill"
-                           style={{ width: `${syncProgress.progress.percent}%` }}
-                         />
-                       </div>
-                       {syncProgress.stepName && (
-                         <div className="sync-progress-step">
-                           현재 단계(Current Step): {getStepDisplayInfo(syncProgress.stepName).title}
-                         </div>
-                       )}
-                     </div>
-                   )}
-                   <div className="sync-steps">
-                      {syncSteps.map((step, idx) => {
-                        const info = getStepDisplayInfo(step.name);
-                        const stepClass =
-                          step.status === "running" ? "running" : step.ok ? "ok" : "fail";
-                        const stepIcon =
-                          step.status === "running" ? "⏳" : step.ok ? "✅" : "❌";
-                        return (
-                          <div key={idx} className={`sync-step ${stepClass}`}>
-                             <span className="step-number">{idx + 1}.</span>
-                             <div className="step-content">
-                               <div className="step-title">{info.title}</div>
-                               <div className="step-command">{info.command}</div>
-                               {!step.ok && step.message && (
-                                 <div className="step-msg">오류(Error): {step.message}</div>
-                               )}
-                             </div>
-                             <span className="step-icon">{stepIcon}</span>
-                          </div>
-                        );
-                      })}
-                      {syncInProgress && <div className="spinner-row">
-                          <span className="spinner">⏳</span>
-                          <span>작업 진행 중...</span>
-                      </div>}
-                   </div>
-                   {syncResult && (
-                       <div className={`notice ${syncResult.ok ? "info" : "error"}`}>
-                           {syncResult.ok ? "모드 적용이 완료되었습니다." : (syncResult.error ? `실패: ${syncResult.error}` : "오류가 발생했습니다.")}
-                       </div>
-                   )}
+          <section className="modal" onClick={(e) => e.stopPropagation()}>
+            <header className="modal-header">
+              <h3>
+                {syncResult
+                  ? (syncResult.ok ? (modalTitle.replace("중...", "완료")) : (syncResult.error ? `오류: ${syncResult.error}` : "오류 발생"))
+                  : modalTitle}
+              </h3>
+              {!syncInProgress && (
+                <button type="button" className="ghost" onClick={closeSyncModal}>
+                  닫기
+                </button>
+              )}
+            </header>
+            <div className="modal-body">
+              {syncProgress?.progress && (
+                <div className="sync-progress">
+                  <div className="sync-progress-header">
+                    <span>진행률(Progress)</span>
+                    <span>{syncProgress.progress.percent}%</span>
+                  </div>
+                  <div className="sync-progress-bar">
+                    <div
+                      className="sync-progress-fill"
+                      style={{ width: `${syncProgress.progress.percent}%` }}
+                    />
+                  </div>
+                  {syncProgress.stepName && (
+                    <div className="sync-progress-step">
+                      현재 단계(Current Step): {getStepDisplayInfo(syncProgress.stepName).title}
+                    </div>
+                  )}
                 </div>
+              )}
+              <div className="sync-steps">
+                {syncSteps.map((step, idx) => {
+                  const info = getStepDisplayInfo(step.name);
+                  const stepClass =
+                    step.status === "running" ? "running" : step.ok ? "ok" : "fail";
+                  const stepIcon =
+                    step.status === "running" ? "⏳" : step.ok ? "✅" : "❌";
+                  return (
+                    <div key={idx} className={`sync-step ${stepClass}`}>
+                      <span className="step-number">{idx + 1}.</span>
+                      <div className="step-content">
+                        <div className="step-title">{info.title}</div>
+                        <div className="step-command">{info.command}</div>
+                        {!step.ok && step.message && (
+                          <div className="step-msg">오류(Error): {step.message}</div>
+                        )}
+                      </div>
+                      <span className="step-icon">{stepIcon}</span>
+                    </div>
+                  );
+                })}
+                {syncInProgress && <div className="spinner-row">
+                  <span className="spinner">⏳</span>
+                  <span>작업 진행 중...</span>
+                </div>}
+              </div>
+              {syncResult && (
+                <div className={`notice ${syncResult.ok ? "info" : "error"}`}>
+                  {syncResult.ok ? "모드 적용이 완료되었습니다." : (syncResult.error ? `실패: ${syncResult.error}` : "오류가 발생했습니다.")}
+                </div>
+              )}
+            </div>
 
-             </section>
+          </section>
         </div>
       )}
     </div>
diff --git a/src/renderer/App.tsx.orig b/src/renderer/App.tsx.orig
new file mode 100644
index 0000000..d9d6d94
--- /dev/null
+++ b/src/renderer/App.tsx.orig
@@ -0,0 +1,1734 @@
+import { useCallback, useEffect, useMemo, useRef, useState } from "react";
+import { APP_CONFIG, SERVER_HEALTHCHECK_URL } from "../shared/config";
+
+type Screen = "serverCheck" | "login" | "signup" | "resetPassword" | "main";
+type CommandCheck = {
+  ok: boolean;
+  command: string;
+  version?: string;
+  error?: string;
+};
+type GitToolsCheck = {
+  git: CommandCheck;
+  lfs: CommandCheck;
+  checkedAt: number;
+};
+type CommandPath = {
+  ok: boolean;
+  command: string;
+  path?: string;
+  error?: string;
+};
+type GitPathsCheck = {
+  git: CommandPath;
+  lfs: CommandPath;
+  checkedAt: number;
+};
+type ModVersionStatus = {
+  ok: boolean;
+  checkedAt: number;
+  currentTag?: string;
+  latestTag?: string;
+  latestMinorTags?: string[];
+  status?: "upToDate" | "patchMismatch" | "majorMinorMismatch" | "unknown";
+  error?: string;
+};
+type SptInstallInfo = {
+  ok: boolean;
+  checkedAt: number;
+  path?: string;
+  source?: "stored" | "auto";
+  needsUserInput?: boolean;
+  error?: string;
+};
+
+const HEALTHCHECK_INTERVAL_MS = APP_CONFIG.healthcheckIntervalMs;
+const HEALTHCHECK_ENDPOINT_FALLBACK = SERVER_HEALTHCHECK_URL;
+const MIN_SERVER_CHECK_SCREEN_MS = 1500;
+const IS_DEV = import.meta.env.DEV;
+const DEV_UI_ENABLED = IS_DEV && import.meta.env.VITE_DEV_UI === "1";
+
+const App = () => {
+  const [screen, setScreen] = useState<Screen>("serverCheck");
+  const [serverHealthy, setServerHealthy] = useState(true);
+  const [serverStatusCode, setServerStatusCode] = useState<number | undefined>();
+  const [serverLatencyMs, setServerLatencyMs] = useState<number | undefined>();
+  const [serverError, setServerError] = useState<string | undefined>();
+  const [serverCheckedUrl, setServerCheckedUrl] = useState<string | undefined>();
+  const [serverCheckInProgress, setServerCheckInProgress] = useState(false);
+  const [serverCheckedAt, setServerCheckedAt] = useState<number | undefined>();
+  const [serverCheckStartedAt, setServerCheckStartedAt] = useState(Date.now());
+  const [serverRecoveryActive, setServerRecoveryActive] = useState(false);
+  const [skipToolsCheck, setSkipToolsCheck] = useState(false);
+  const [devProceedReady, setDevProceedReady] = useState(false);
+  const [simulateToolsMissing, setSimulateToolsMissing] = useState(false);
+  const [simulateInstallProgress, setSimulateInstallProgress] = useState(false);
+  const [gitCheckInProgress, setGitCheckInProgress] = useState(false);
+  const [gitCheckedAt, setGitCheckedAt] = useState<number | undefined>();
+  const [gitCheckResult, setGitCheckResult] = useState<GitToolsCheck | undefined>();
+  const [gitPathsLoading, setGitPathsLoading] = useState(false);
+  const [gitPathsResult, setGitPathsResult] = useState<GitPathsCheck | undefined>();
+  const [toolsModalOpen, setToolsModalOpen] = useState(false);
+  const [installInProgress, setInstallInProgress] = useState(false);
+  const [installMessage, setInstallMessage] = useState<string | undefined>();
+  const [hasSession, setHasSession] = useState(false);
+  const [loginId, setLoginId] = useState("");
+  const [loginPassword, setLoginPassword] = useState("");
+  const [signupId, setSignupId] = useState("");
+  const [signupPassword, setSignupPassword] = useState("");
+  const [confirmPassword, setConfirmPassword] = useState("");
+  const [profileLoading, setProfileLoading] = useState(false);
+  const [profile, setProfile] = useState<{
+    username: string;
+    nickname?: string;
+    level?: number;
+    side?: string;
+    id?: string;
+  } | undefined>();
+  const [profileActionInProgress, setProfileActionInProgress] = useState(false);
+  const [syncInProgress, setSyncInProgress] = useState(false);
+  const [simulateSyncFail, setSimulateSyncFail] = useState(false);
+  const [modCheckInProgress, setModCheckInProgress] = useState(false);
+  const [modVersionStatus, setModVersionStatus] = useState<ModVersionStatus | undefined>();
+  const [modCheckMessage, setModCheckMessage] = useState<string | undefined>();
+  const [selectedModTag, setSelectedModTag] = useState("");
+  const [sptInstallInfo, setSptInstallInfo] = useState<SptInstallInfo | undefined>();
+  const [sptInstallMessage, setSptInstallMessage] = useState<string | undefined>();
+  const [sptPathInput, setSptPathInput] = useState("");
+  const [allowMissingSptPath, setAllowMissingSptPath] = useState(false);
+  const healthCheckInFlightRef = useRef(false);
+  const gitCheckInFlightRef = useRef(false);
+  const gitCheckedRef = useRef(false);
+  const modCheckInFlightRef = useRef(false);
+  const modCheckedRef = useRef(false);
+  const sessionResumeAttemptedRef = useRef(false);
+  const transitionTimeoutRef = useRef<number | undefined>();
+  const simulateToolsMissingRef = useRef(false);
+  const devInstallTimerRef = useRef<number | undefined>();
+  const [modalTitle, setModalTitle] = useState("모드 적용 중...");
+  const [syncSteps, setSyncSteps] = useState<
+    Array<{
+      name: string;
+      ok: boolean;
+      message?: string;
+      status?: "running" | "done" | "error";
+      progress?: { current: number; total: number; percent: number };
+    }>
+  >([]);
+  const [syncResult, setSyncResult] = useState<{ ok: boolean; error?: string } | undefined>();
+
+  const getStepDisplayInfo = (rawName: string) => {
+    if (rawName.startsWith("git fetch")) {
+      return { title: "저장소 정보 업데이트", command: rawName };
+    }
+    if (rawName.startsWith("git clone")) {
+      return { title: "모드 저장소 다운로드", command: rawName };
+    }
+    if (rawName.startsWith("git checkout")) {
+      const tag = rawName.replace("git checkout", "").trim();
+      return { title: `버전 ${tag} 설정`, command: rawName };
+    }
+    if (rawName.startsWith("git lfs pull")) {
+      return { title: "대용량 파일(LFS) 다운로드", command: rawName };
+    }
+    if (rawName === "copying files") {
+      return { title: "모드 파일 적용", command: "Copying files to Game Directory..." };
+    }
+    // Git Install Steps
+    if (rawName === "winget 확인") {
+      return { title: "패키지 관리자(winget) 확인", command: "checking winget..." };
+    }
+    if (rawName === "Git 설치") {
+      return { title: "Git 설치 (시간이 걸릴 수 있습니다)", command: "winget install Git.Git" };
+    }
+    if (rawName === "Git LFS 설치") {
+      return { title: "Git LFS 설치", command: "winget install GitHub.GitLFS" };
+    }
+    return { title: rawName, command: "" };
+  };
+
+  const upsertSyncStep = useCallback(
+    (nextStep: {
+      name: string;
+      ok: boolean;
+      message?: string;
+      status?: "running" | "done" | "error";
+      progress?: { current: number; total: number; percent: number };
+    }) => {
+      setSyncSteps((prev) => {
+        const index = prev.findIndex((step) => step.name === nextStep.name);
+        if (index < 0) {
+          return [...prev, nextStep];
+        }
+        const updated = [...prev];
+        updated[index] = { ...updated[index], ...nextStep };
+        return updated;
+      });
+    },
+    []
+  );
+
+  const asObject = (value: unknown) =>
+    value && typeof value === "object" ? (value as Record<string, unknown>) : undefined;
+  const pickString = (...values: unknown[]) =>
+    values.find((value) => typeof value === "string" && value.trim().length > 0) as
+    | string
+    | undefined;
+  const pickNumber = (...values: unknown[]) => {
+    const candidate = values.find(
+      (value) => typeof value === "number" || (typeof value === "string" && value.trim() !== "")
+    );
+    if (typeof candidate === "number") {
+      return candidate;
+    }
+    if (typeof candidate === "string") {
+      const parsed = Number(candidate);
+      return Number.isFinite(parsed) ? parsed : undefined;
+    }
+    return undefined;
+  };
+
+  const extractProfile = (data: unknown, fallbackUsername: string) => {
+    const root = asObject(data);
+    const profileCandidate = Array.isArray(root?.profiles)
+      ? root?.profiles?.[0]
+      : root?.profile ?? root?.data ?? root;
+    const profileObject = asObject(profileCandidate) ?? {};
+    const info = asObject(profileObject.info ?? profileObject.Info) ?? profileObject;
+
+    return {
+      username: pickString(info.username, info.Username, profileObject.username, fallbackUsername) ?? fallbackUsername,
+      nickname: pickString(info.nickname, info.Nickname, profileObject.nickname, profileObject.Nickname),
+      level: pickNumber(
+        info.level,
+        info.Level,
+        info.currlvl,
+        info.currLvl,
+        profileObject.level,
+        profileObject.Level,
+        profileObject.currlvl,
+        profileObject.currLvl
+      ),
+      side: pickString(info.side, info.Side, profileObject.side, profileObject.Side),
+      id: pickString(info.id, info._id, profileObject.id, profileObject._id, profileObject.profileId)
+    };
+  };
+
+  const runGitCheck = useCallback(async (force = false) => {
+    if (force) {
+      gitCheckedRef.current = false;
+    }
+
+    if (gitCheckInFlightRef.current || (!force && gitCheckedRef.current)) {
+      return gitCheckResult;
+    }
+
+    gitCheckInFlightRef.current = true;
+    setGitCheckInProgress(true);
+
+    try {
+      if (DEV_UI_ENABLED && simulateToolsMissingRef.current) {
+        const simulated = {
+          git: { ok: false, command: "git", error: "simulated_missing" },
+          lfs: { ok: false, command: "git lfs", error: "simulated_missing" },
+          checkedAt: Date.now()
+        };
+        setGitCheckResult(simulated);
+        setGitCheckedAt(simulated.checkedAt);
+        gitCheckedRef.current = true;
+        return simulated;
+      }
+
+      if (!window.sptLauncher?.checkGitTools) {
+        throw new Error("preload(preload) 미로딩: window.sptLauncher.checkGitTools가 없습니다.");
+      }
+
+      const result = await window.sptLauncher.checkGitTools();
+      setGitCheckResult(result);
+      setGitCheckedAt(result.checkedAt ?? Date.now());
+      gitCheckedRef.current = true;
+      return result;
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      const fallback = {
+        git: { ok: false, command: "git", error: message },
+        lfs: { ok: false, command: "git lfs", error: message },
+        checkedAt: Date.now()
+      };
+      setGitCheckResult(fallback);
+      setGitCheckedAt(Date.now());
+      gitCheckedRef.current = true;
+      return fallback;
+    } finally {
+      gitCheckInFlightRef.current = false;
+      setGitCheckInProgress(false);
+    }
+  }, [gitCheckResult]);
+
+  const runModVersionCheck = useCallback(async (force = false) => {
+    if (force) {
+      modCheckedRef.current = false;
+    }
+
+    if (modCheckInFlightRef.current || (!force && modCheckedRef.current)) {
+      return modVersionStatus;
+    }
+
+    modCheckInFlightRef.current = true;
+    setModCheckInProgress(true);
+    setModCheckMessage(undefined);
+
+    try {
+      if (!window.sptLauncher?.getModVersionStatus) {
+        throw new Error("preload(preload) 미로딩: window.sptLauncher.getModVersionStatus가 없습니다.");
+      }
+
+      const result = await window.sptLauncher.getModVersionStatus();
+      setModVersionStatus(result);
+      modCheckedRef.current = true;
+      if (!result.ok) {
+        setModCheckMessage(result.error ?? "모드 버전 확인에 실패했습니다.");
+      }
+      return result;
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      const fallback: ModVersionStatus = {
+        ok: false,
+        checkedAt: Date.now(),
+        error: message
+      };
+      setModVersionStatus(fallback);
+      setModCheckMessage(message);
+      modCheckedRef.current = true;
+      return fallback;
+    } finally {
+      modCheckInFlightRef.current = false;
+      setModCheckInProgress(false);
+    }
+  }, [modVersionStatus]);
+
+  const runSptInstallCheck = useCallback(async () => {
+    if (!window.sptLauncher?.getSptInstallInfo) {
+      setSptInstallMessage("SPT 경로 확인 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    const result = await window.sptLauncher.getSptInstallInfo();
+    setSptInstallInfo(result);
+    if (!result.ok) {
+      if (result.error === "unsupported_platform") {
+        setSptInstallMessage("Windows 환경에서만 SPT 경로 확인이 가능합니다.");
+      } else if (result.error === "not_found") {
+        setSptInstallMessage("SPT 설치 경로를 찾지 못했습니다.");
+      } else {
+        setSptInstallMessage(result.error ?? "SPT 경로 확인에 실패했습니다.");
+      }
+    } else {
+      setSptInstallMessage(undefined);
+      if (result.path) {
+        setSptPathInput(result.path);
+      }
+    }
+  }, []);
+
+  const clearTransitionTimeout = useCallback(() => {
+    if (transitionTimeoutRef.current) {
+      window.clearTimeout(transitionTimeoutRef.current);
+      transitionTimeoutRef.current = undefined;
+    }
+  }, []);
+
+  const scheduleScreenTransition = useCallback(
+    (nextScreen: Screen) => {
+      clearTransitionTimeout();
+      const elapsedMs = Date.now() - serverCheckStartedAt;
+      const remainingMs = Math.max(0, MIN_SERVER_CHECK_SCREEN_MS - elapsedMs);
+
+      if (remainingMs > 0) {
+        transitionTimeoutRef.current = window.setTimeout(() => {
+          setScreen(nextScreen);
+        }, remainingMs);
+        return;
+      }
+
+      setScreen(nextScreen);
+    },
+    [clearTransitionTimeout, serverCheckStartedAt]
+  );
+
+  const enterRecoveryMode = useCallback(
+    (reason: string) => {
+      setServerRecoveryActive(true);
+      setServerHealthy(false);
+      setServerStatusCode(undefined);
+      setServerLatencyMs(undefined);
+      setServerError(reason);
+      setServerCheckedUrl(undefined);
+      setServerCheckedAt(Date.now());
+      setHasSession(false);
+      setProfile(undefined);
+      setSkipToolsCheck(false);
+      setDevProceedReady(false);
+      sessionResumeAttemptedRef.current = false;
+      setScreen("serverCheck");
+      clearTransitionTimeout();
+    },
+    [clearTransitionTimeout]
+  );
+
+  const isTimeoutError = (error?: string) => {
+    if (!error) {
+      return false;
+    }
+    return error.toLowerCase().includes("timeout");
+  };
+
+  const runHealthCheck = useCallback(
+    async (trigger: "initial" | "manual" | "recovery" = "initial") => {
+      if (healthCheckInFlightRef.current) {
+        return;
+      }
+
+      healthCheckInFlightRef.current = true;
+      setServerCheckInProgress(true);
+      setServerError(undefined);
+      let isHealthy = false;
+      let failureReason = "healthcheck_failed";
+
+      try {
+        if (!window.sptLauncher?.checkServerHealth) {
+          throw new Error("preload(preload) 미로딩: window.sptLauncher가 없습니다.");
+        }
+
+        const result = await window.sptLauncher.checkServerHealth();
+        isHealthy = result.ok;
+        if (!result.ok) {
+          failureReason = result.error ?? "healthcheck_failed";
+        }
+        setServerHealthy(result.ok);
+        setServerStatusCode(result.status);
+        setServerLatencyMs(result.latencyMs);
+        setServerError(result.error);
+        setServerCheckedUrl(result.url ?? HEALTHCHECK_ENDPOINT_FALLBACK);
+        setServerCheckedAt(Date.now());
+
+        if (screen === "serverCheck" && result.ok) {
+          const gitResult = !gitCheckedRef.current ? await runGitCheck() : gitCheckResult;
+          const toolsReady = Boolean(gitResult?.git.ok && gitResult?.lfs.ok);
+
+          if (serverRecoveryActive) {
+            setServerRecoveryActive(false);
+            if (DEV_UI_ENABLED) {
+              setDevProceedReady(true);
+            } else {
+              scheduleScreenTransition("login");
+            }
+            return;
+          }
+
+          if (!toolsReady && gitResult && !skipToolsCheck) {
+            return;
+          }
+
+          if (DEV_UI_ENABLED) {
+            setDevProceedReady(true);
+            return;
+          }
+
+          scheduleScreenTransition(hasSession ? "main" : "login");
+        }
+      } catch (error) {
+        const message = error instanceof Error ? error.message : String(error);
+        failureReason = message;
+        setServerHealthy(false);
+        setServerStatusCode(undefined);
+        setServerLatencyMs(undefined);
+        setServerError(message);
+        setServerCheckedUrl(undefined);
+        setServerCheckedAt(Date.now());
+      } finally {
+        healthCheckInFlightRef.current = false;
+        setServerCheckInProgress(false);
+      }
+
+      if (trigger === "manual" && !isHealthy) {
+        enterRecoveryMode(failureReason);
+      }
+    },
+    [
+      screen,
+      hasSession,
+      serverRecoveryActive,
+      runGitCheck,
+      gitCheckResult,
+      scheduleScreenTransition,
+      enterRecoveryMode,
+      skipToolsCheck
+    ]
+  );
+
+  const handleManualHealthCheck = () => {
+    void runHealthCheck("manual");
+  };
+
+  useEffect(() => {
+    if (screen !== "serverCheck") {
+      return;
+    }
+
+    void runHealthCheck(serverRecoveryActive ? "recovery" : "initial");
+  }, [screen, serverRecoveryActive, runHealthCheck]);
+
+  useEffect(() => {
+    if (
+      screen !== "serverCheck" ||
+      !serverHealthy ||
+      hasSession ||
+      serverCheckInProgress ||
+      !serverCheckedAt
+    ) {
+      return;
+    }
+    if (sessionResumeAttemptedRef.current) {
+      return;
+    }
+    if (!window.sptLauncher?.resumeSession) {
+      sessionResumeAttemptedRef.current = true;
+      return;
+    }
+
+    sessionResumeAttemptedRef.current = true;
+    void (async () => {
+      try {
+        const result = await window.sptLauncher.resumeSession();
+        if (!result.ok || !result.data) {
+          scheduleScreenTransition("login");
+          return;
+        }
+
+        const resumedProfile = extractProfile(result.data, loginId.trim());
+        // Simple validation: profile must have an ID or Username to be considered valid
+        if (!resumedProfile.id && !resumedProfile.username) {
+          scheduleScreenTransition("login");
+          return;
+        }
+
+        setProfile(resumedProfile);
+        setHasSession(true);
+        if (resumedProfile.username) {
+          setLoginId(resumedProfile.username);
+        }
+        clearTransitionTimeout();
+        setScreen("main");
+      } catch (error) {
+        console.error("Session resume failed", error);
+        scheduleScreenTransition("login");
+      }
+    })();
+  }, [
+    screen,
+    serverHealthy,
+    hasSession,
+    serverCheckInProgress,
+    serverCheckedAt,
+    loginId,
+    clearTransitionTimeout,
+    extractProfile
+  ]);
+
+  useEffect(() => {
+    if (screen !== "serverCheck") {
+      return;
+    }
+    setServerCheckStartedAt(Date.now());
+    setDevProceedReady(false);
+  }, [screen]);
+
+  useEffect(() => {
+    if (!serverRecoveryActive) {
+      return;
+    }
+    const interval = window.setInterval(() => {
+      void runHealthCheck("recovery");
+    }, HEALTHCHECK_INTERVAL_MS);
+
+    return () => window.clearInterval(interval);
+  }, [serverRecoveryActive, runHealthCheck]);
+
+  useEffect(() => {
+    simulateToolsMissingRef.current = simulateToolsMissing;
+  }, [simulateToolsMissing]);
+
+  useEffect(() => {
+    return () => {
+      if (devInstallTimerRef.current) {
+        window.clearTimeout(devInstallTimerRef.current);
+      }
+    };
+  }, []);
+
+  useEffect(() => {
+    return () => clearTransitionTimeout();
+  }, [clearTransitionTimeout]);
+
+  useEffect(() => {
+    if (!hasSession || screen !== "main") {
+      return;
+    }
+    void runModVersionCheck();
+  }, [hasSession, screen, runModVersionCheck]);
+
+  useEffect(() => {
+    if (screen !== "main") {
+      return;
+    }
+    void runSptInstallCheck();
+  }, [screen, runSptInstallCheck]);
+
+  const serverStatusLabel = useMemo(() => {
+    return serverHealthy ? "정상" : "불가";
+  }, [serverHealthy]);
+
+  const modStatusLabel = useMemo(() => {
+    if (modCheckInProgress) {
+      return "확인 중";
+    }
+    if (!modVersionStatus?.ok) {
+      return "확인 실패";
+    }
+    switch (modVersionStatus.status) {
+      case "upToDate":
+        return "최신";
+      case "patchMismatch":
+        return "패치 업데이트 필요";
+      case "majorMinorMismatch":
+        return "강제 동기화 필요";
+      default:
+        return "알 수 없음";
+    }
+  }, [modCheckInProgress, modVersionStatus]);
+
+  const modStatusClass = (() => {
+    if (modCheckInProgress) {
+      return "idle";
+    }
+    if (!modVersionStatus?.ok) {
+      return "blocked";
+    }
+    if (modVersionStatus.status === "upToDate") {
+      return "ok";
+    }
+    return "blocked";
+  })();
+
+  const modTagOptions = useMemo(() => {
+    const tags = new Set<string>();
+    if (modVersionStatus?.currentTag) {
+      tags.add(modVersionStatus.currentTag);
+    }
+    if (modVersionStatus?.latestTag) {
+      tags.add(modVersionStatus.latestTag);
+    }
+    modVersionStatus?.latestMinorTags?.forEach((tag) => tags.add(tag));
+    return Array.from(tags);
+  }, [modVersionStatus]);
+
+  const syncProgress = useMemo(() => {
+    for (let i = syncSteps.length - 1; i >= 0; i -= 1) {
+      if (syncSteps[i].progress) {
+        return { progress: syncSteps[i].progress, stepName: syncSteps[i].name };
+      }
+    }
+    return undefined;
+  }, [syncSteps]);
+
+  const startReady = Boolean(sptInstallInfo?.ok && modVersionStatus?.ok && !syncInProgress);
+  const startStatusLabel = syncInProgress
+    ? "동기화 중"
+    : startReady
+      ? "준비됨"
+      : !sptInstallInfo?.ok
+        ? "경로 필요"
+        : !modVersionStatus?.ok
+          ? "버전 확인 필요"
+          : "준비 안됨";
+  const startStatusClass = syncInProgress ? "idle" : startReady ? "ok" : "blocked";
+
+  useEffect(() => {
+    if (modTagOptions.length === 0) {
+      if (selectedModTag) {
+        setSelectedModTag("");
+      }
+      return;
+    }
+    const preferred = modVersionStatus?.latestTag ?? modTagOptions[0];
+    if (!modTagOptions.includes(selectedModTag)) {
+      setSelectedModTag(preferred ?? "");
+    }
+  }, [modTagOptions, modVersionStatus?.latestTag, selectedModTag]);
+
+  const serverStatusLedClass = serverCheckInProgress ? "idle" : serverHealthy ? "ok" : "blocked";
+  const gitStatusLedClass = (() => {
+    if (gitCheckInProgress) {
+      return "idle";
+    }
+    if (!gitCheckResult) {
+      return "idle";
+    }
+    if (gitCheckResult.git.ok && gitCheckResult.lfs.ok) {
+      return "ok";
+    }
+    return "blocked";
+  })();
+  const gitLedClass = gitCheckInProgress
+    ? "idle"
+    : !gitCheckResult
+      ? "idle"
+      : gitCheckResult.git.ok
+        ? "ok"
+        : "blocked";
+  const lfsLedClass = gitCheckInProgress
+    ? "idle"
+    : !gitCheckResult
+      ? "idle"
+      : gitCheckResult.lfs.ok
+        ? "ok"
+        : "blocked";
+
+  const handleOpenToolsModal = () => {
+    setToolsModalOpen(true);
+  };
+
+  const handleRecheckTools = async () => {
+    await runGitCheck(true);
+  };
+
+  const handleInstallTools = async () => {
+    if (!window.sptLauncher?.installGitTools) {
+      window.alert("자동 설치 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    setInstallInProgress(true);
+    setInstallMessage(undefined);
+
+    // Modal Setup
+    setSyncSteps([]);
+    setSyncResult(undefined);
+    setModalTitle("Git 도구 설치 중...");
+    setSyncInProgress(true);
+
+    const cleanup = window.sptLauncher.onGitInstallProgress((_e, step: any) => {
+      const normalized = {
+        name: step.name,
+        ok: Boolean(step.ok),
+        message: step.ok ? undefined : step.message,
+        status: step.status,
+        progress: step.progress
+      };
+      upsertSyncStep(normalized);
+    });
+
+    try {
+      const result = await window.sptLauncher.installGitTools();
+      if (!result.ok) {
+        setInstallMessage(result.error ?? "자동 설치에 실패했습니다.");
+        setSyncResult({ ok: false, error: result.error });
+      } else {
+        setInstallMessage("자동 설치가 완료되었습니다.");
+        setSyncResult({ ok: true });
+      }
+      if (result.check) {
+        setGitCheckResult(result.check);
+        setGitCheckedAt(result.check.checkedAt ?? Date.now());
+      }
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      setInstallMessage(message);
+      setSyncResult({ ok: false, error: message });
+    } finally {
+      cleanup();
+      setInstallInProgress(false);
+      setSyncInProgress(false); // Show close button
+    }
+  };
+
+  const runDevInstallSimulation = useCallback(() => {
+    if (!DEV_UI_ENABLED) {
+      return;
+    }
+    if (devInstallTimerRef.current) {
+      window.clearTimeout(devInstallTimerRef.current);
+    }
+    setSimulateInstallProgress(true);
+    setInstallInProgress(true);
+    setInstallMessage(undefined);
+    setSyncSteps([]);
+    setSyncResult(undefined);
+    setModalTitle("Git 도구 설치 중...");
+    setSyncInProgress(true);
+
+    const steps = [
+      { name: "winget 확인", percent: 33 },
+      { name: "Git 설치", percent: 67 },
+      { name: "Git LFS 설치", percent: 100 }
+    ];
+
+    let index = 0;
+    const tick = () => {
+      const current = steps[index];
+      upsertSyncStep({
+        name: current.name,
+        ok: true,
+        status: "running",
+        progress: { current: index + 1, total: steps.length, percent: current.percent }
+      });
+
+      devInstallTimerRef.current = window.setTimeout(() => {
+        upsertSyncStep({
+          name: current.name,
+          ok: true,
+          status: "done",
+          progress: { current: index + 1, total: steps.length, percent: current.percent }
+        });
+        index += 1;
+        if (index < steps.length) {
+          tick();
+          return;
+        }
+        setInstallMessage("자동 설치가 완료되었습니다.");
+        setSyncResult({ ok: true });
+        setInstallInProgress(false);
+        setSyncInProgress(false);
+        setSimulateInstallProgress(false);
+      }, 800);
+    };
+
+    tick();
+  }, [upsertSyncStep]);
+
+  const handleFetchGitPaths = async () => {
+    if (!window.sptLauncher?.getGitPaths) {
+      window.alert("경로 확인 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    setGitPathsLoading(true);
+    try {
+      const result = await window.sptLauncher.getGitPaths();
+      setGitPathsResult(result);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      setGitPathsResult({
+        git: { ok: false, command: "git", error: message },
+        lfs: { ok: false, command: "git-lfs", error: message },
+        checkedAt: Date.now()
+      });
+    } finally {
+      setGitPathsLoading(false);
+    }
+  };
+
+  const handleLogin = async () => {
+    const trimmedId = loginId.trim();
+    const trimmedPassword = loginPassword.trim();
+    if (!trimmedId) {
+      window.alert("아이디를 입력해주세요.");
+      return;
+    }
+
+    if (!window.sptLauncher?.login) {
+      window.alert("로그인 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    setProfileLoading(true);
+
+    try {
+      const result = await window.sptLauncher.login({
+        username: trimmedId,
+        password: trimmedPassword
+      });
+      if (!result.ok) {
+        if (isTimeoutError(result.error)) {
+          enterRecoveryMode("timeout");
+          return;
+        }
+        window.alert(result.error ?? "로그인에 실패했습니다.");
+        return;
+      }
+
+      if (!result.data) {
+        window.alert("프로필 응답이 비어있습니다.");
+        return;
+      }
+
+      setProfile(extractProfile(result.data, trimmedId));
+      setHasSession(true);
+      setScreen("main");
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      if (isTimeoutError(message)) {
+        enterRecoveryMode("timeout");
+        return;
+      }
+      window.alert(message);
+    } finally {
+      setProfileLoading(false);
+    }
+  };
+
+  const handleSignup = async () => {
+    const trimmedId = signupId.trim();
+    const trimmedPassword = signupPassword.trim();
+    const trimmedConfirm = confirmPassword.trim();
+
+    if (!trimmedId) {
+      window.alert("아이디를 입력해주세요.");
+      return;
+    }
+    if (!trimmedPassword) {
+      window.alert("비밀번호를 입력해주세요.");
+      return;
+    }
+    if (trimmedPassword !== trimmedConfirm) {
+      window.alert("비밀번호가 일치하지 않습니다.");
+      return;
+    }
+
+    if (!window.sptLauncher?.register) {
+      window.alert("회원가입 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    setProfileLoading(true);
+    try {
+      const result = await window.sptLauncher.register({
+        username: trimmedId,
+        password: trimmedPassword
+      });
+
+      if (!result.ok) {
+        window.alert(result.error ?? "회원가입 요청에 실패했습니다.");
+        return;
+      }
+
+      window.alert("회원가입이 완료되었습니다. 이제 로그인할 수 있습니다.");
+      setLoginId(trimmedId);
+      setLoginPassword(trimmedPassword);
+      setScreen("login");
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      window.alert(message);
+    } finally {
+      setProfileLoading(false);
+    }
+  };
+
+  const handlePasswordReset = () => {
+    window.alert("비밀번호 변경 요청이 접수되었습니다.");
+    setScreen("login");
+  };
+
+  const handleLogout = () => {
+    if (window.sptLauncher?.clearSession) {
+      void window.sptLauncher.clearSession();
+    }
+    setHasSession(false);
+    setProfile(undefined);
+    setScreen("login");
+    setModVersionStatus(undefined);
+    setModCheckMessage(undefined);
+    modCheckedRef.current = false;
+    setSptInstallInfo(undefined);
+    setSptInstallMessage(undefined);
+  };
+
+  const handleProfileDownload = async () => {
+    const username = profile?.username?.trim() ?? loginId.trim();
+    if (!username) {
+      window.alert("아이디를 입력해주세요.");
+      return;
+    }
+
+    if (!window.sptLauncher?.downloadProfile) {
+      window.alert("프로필 다운로드 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    setProfileActionInProgress(true);
+    try {
+      const result = await window.sptLauncher.downloadProfile({ username });
+      if (!result.ok) {
+        if (isTimeoutError(result.error)) {
+          enterRecoveryMode("timeout");
+          return;
+        }
+        window.alert(result.error ?? "프로필 다운로드에 실패했습니다.");
+        return;
+      }
+
+      window.alert(`프로필을 다운로드했습니다: ${result.filePath ?? "-"}`);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      if (isTimeoutError(message)) {
+        enterRecoveryMode("timeout");
+        return;
+      }
+      window.alert(message);
+    } finally {
+      setProfileActionInProgress(false);
+    }
+  };
+
+  const handleProfileReset = async () => {
+    const username = profile?.username?.trim() ?? loginId.trim();
+    if (!username) {
+      window.alert("아이디를 입력해주세요.");
+      return;
+    }
+
+    if (!window.sptLauncher?.resetProfile) {
+      window.alert("프로필 리셋 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    const confirmed = window.confirm("프로필을 리셋할까요?");
+    if (!confirmed) {
+      return;
+    }
+
+    setProfileActionInProgress(true);
+    try {
+      const result = await window.sptLauncher.resetProfile({ username });
+      if (!result.ok) {
+        if (isTimeoutError(result.error)) {
+          enterRecoveryMode("timeout");
+          return;
+        }
+        window.alert(result.error ?? "프로필 리셋에 실패했습니다.");
+        return;
+      }
+
+      window.alert("프로필 리셋 요청이 완료되었습니다.");
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      if (isTimeoutError(message)) {
+        enterRecoveryMode("timeout");
+        return;
+      }
+      window.alert(message);
+    } finally {
+      setProfileActionInProgress(false);
+    }
+  };
+
+  const updateLocalModVersion = async (tag: string) => {
+    if (!window.sptLauncher?.setLocalModVersion) {
+      return false;
+    }
+    const result = await window.sptLauncher.setLocalModVersion({ tag });
+    if (!result.ok) {
+      return false;
+    }
+    return true;
+  };
+
+  const applyModSyncResult = async (tag?: string) => {
+    if (!tag) {
+      return;
+    }
+    const updated = await updateLocalModVersion(tag);
+    if (!updated) {
+      return;
+    }
+    setModVersionStatus((prev) => {
+      if (!prev) {
+        return prev;
+      }
+      return {
+        ...prev,
+        currentTag: tag,
+        status: prev.latestTag === tag ? "upToDate" : prev.status
+      };
+    });
+  };
+
+  const performModSync = async (
+    mode: "required" | "optional" | "force",
+    overrideTag?: string
+  ) => {
+    if (syncInProgress) {
+      return false;
+    }
+
+    setSyncInProgress(true);
+    const trimmedOverride = overrideTag?.trim();
+    const targetTag =
+      trimmedOverride ||
+      (mode === "force"
+        ? modVersionStatus?.currentTag ?? modVersionStatus?.latestTag
+        : modVersionStatus?.latestTag);
+
+    try {
+      const targetDir = sptInstallInfo?.path?.trim();
+      if (!targetDir) {
+        window.alert("SPT 경로(path)가 설정되지 않았습니다.");
+        return false;
+      }
+      if (!targetTag) {
+        setModCheckMessage("동기화할 태그(tag)를 찾지 못했습니다.");
+        return false;
+      }
+      if (!window.sptLauncher?.runModSync) {
+        window.alert("동기화 기능이 준비되지 않았습니다.");
+        return false;
+      }
+
+      if (simulateSyncFail) {
+        throw new Error("simulated_sync_fail");
+      }
+
+      setSyncSteps([]);
+      setSyncResult(undefined);
+      setModalTitle("모드 적용 중...");
+      setSyncInProgress(true);
+
+      // Subscribe to progress events
+      const cleanup = window.sptLauncher.onModSyncProgress
+        ? window.sptLauncher.onModSyncProgress((_event, step) => {
+          // eslint-disable-next-line @typescript-eslint/no-explicit-any
+          const s = step as any;
+          const uiStep = {
+            name: s.name,
+            ok: s.result?.ok ?? false,
+            message: s.result?.ok ? undefined : s.result?.message ?? s.result?.error,
+            status: (s.result?.ok ? "done" : "error") as "done" | "error"
+          };
+          upsertSyncStep(uiStep);
+        })
+        : () => { };
+
+      try {
+        const result = await window.sptLauncher.runModSync({
+          targetDir,
+          tag: targetTag
+        });
+
+        cleanup(); // Unsubscribe
+
+        if (!result.ok) {
+          setSyncResult({ ok: false, error: result.error ?? "모드 동기화에 실패했습니다." });
+          // If steps are returned in result (history), use them?
+          // The real-time listener should have captured them, but let's ensure we have full list
+          if (result.steps) {
+            setSyncSteps(
+              result.steps.map((s) => ({
+                name: s.name,
+                ok: s.ok,
+                message: s.ok ? undefined : s.message,
+                status: s.ok ? "done" : "error"
+              }))
+            );
+          }
+          setModCheckMessage(result.error ?? "모드 동기화에 실패했습니다.");
+          return false;
+        }
+
+        setSyncResult({ ok: true });
+        // Ensure steps from result are shown (more reliable final state)
+        if (result.steps) {
+          setSyncSteps(
+            result.steps.map((s) => ({
+              name: s.name,
+              ok: s.ok,
+              message: s.ok ? undefined : s.message,
+              status: s.ok ? "done" : "error"
+            }))
+          );
+        }
+
+        await applyModSyncResult(result.tag ?? targetTag);
+        setModCheckMessage(undefined);
+        return true;
+      } catch (err) {
+        cleanup();
+        throw err;
+      }
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      const proceed = window.confirm(
+        `모드 동기화가 실패했습니다. 그래도 실행할까요? (${message})`
+      );
+      return proceed;
+    } finally {
+      setSyncInProgress(false);
+      // Removed setSyncResult(undefined) here to keep modal open until user closes
+    }
+  };
+
+  const closeSyncModal = () => {
+    if (syncInProgress) {
+      return; // Cannot close while running
+    }
+    setSyncResult(undefined);
+    setSyncSteps([]);
+  };
+
+  const handleLaunch = async () => {
+    const status = modVersionStatus?.status;
+    if (status === "majorMinorMismatch") {
+      window.alert("모드 메이저/마이너 버전이 다릅니다. 동기화 후 실행됩니다.");
+      const ok = await performModSync("required");
+      if (!ok) {
+        return;
+      }
+    }
+
+    if (syncInProgress) {
+      return;
+    }
+
+    if (!window.sptLauncher?.launchGame) {
+      window.alert("게임 시작 기능이 준비되지 않았습니다.");
+      return;
+    }
+
+    try {
+      const result = await window.sptLauncher.launchGame();
+      if (!result.ok) {
+        if (result.error === "already_running") {
+          window.alert(`게임이 이미 실행 중입니다.\n(발견된 프로세스: ${(result.details ?? []).join(", ")})`);
+        } else if (result.error === "mod_verification_failed") {
+          window.alert("모드 버전 검증에 실패했습니다. 버전을 다시 확인해주세요.");
+        } else if (result.error === "no_spt_path") {
+          window.alert("SPT 설치 경로가 설정되지 않았습니다.");
+        } else if (result.error === "executable_not_found") {
+          window.alert("실행 파일(Launcher/Server)을 찾을 수 없습니다.");
+        } else {
+          window.alert(`게임 실행 실패: ${result.error}`);
+        }
+        return;
+      }
+
+      // Success
+      window.alert(`게임이 실행되었습니다.\n(${result.executedPath})`);
+    } catch (e: any) {
+      window.alert(`게임 실행 중 오류가 발생했습니다: ${e.message}`);
+    }
+  };
+
+  return (
+    <div className="app">
+      <header className="app-header">
+        <h1>SPT Launcher</h1>
+      </header>
+
+      {screen === "serverCheck" && (
+        <section className="card hero server-check">
+          <h2>서버 연결 및 도구 상태 점검</h2>
+          <p className={`status ${serverCheckInProgress ? "idle" : serverHealthy ? "ok" : "blocked"}`}>
+            {serverCheckInProgress ? "체크 중..." : serverHealthy ? "정상" : "불가"}
+          </p>
+          <div className="notice">
+            <div className="tool-led">
+              <span className="tool-label">서버</span>
+              <span className={`led ${serverStatusLedClass}`} aria-label="서버 상태" />
+              {serverRecoveryActive && <span className="helper">복구 중</span>}
+            </div>
+            <div className="tool-led">
+              <span className="tool-label">Git</span>
+              <span className={`led ${gitLedClass}`} aria-label="Git 상태" />
+            </div>
+            <div className="tool-led">
+              <span className="tool-label">Git LFS</span>
+              <span className={`led ${lfsLedClass}`} aria-label="Git LFS 상태" />
+            </div>
+          </div>
+          {!serverCheckInProgress && !serverHealthy && (
+            <button type="button" onClick={handleManualHealthCheck}>
+              다시 확인
+            </button>
+          )}
+          {serverHealthy && gitCheckResult && !(gitCheckResult.git.ok && gitCheckResult.lfs.ok) && (
+            <div className="notice">
+              <strong>도구 설치 필요</strong>
+              <div className="helper">
+                Git/Git LFS 감지에 실패했습니다. 자동 설치(Windows) 또는 수동 설치 후 재확인해주세요.
+              </div>
+              <div className="modal-actions">
+                <button type="button" onClick={handleInstallTools} disabled={installInProgress}>
+                  {installInProgress ? "설치 중..." : "자동 설치"}
+                </button>
+                <button type="button" className="ghost" onClick={handleRecheckTools} disabled={gitCheckInProgress}>
+                  {gitCheckInProgress ? "점검 중..." : "재확인"}
+                </button>
+                <button
+                  type="button"
+                  className="ghost"
+                  onClick={() => {
+                    setSkipToolsCheck(true);
+                    scheduleScreenTransition(
+                      DEV_UI_ENABLED ? "login" : hasSession ? "main" : "login"
+                    );
+                  }}
+                >
+                  나중에 진행
+                </button>
+              </div>
+            </div>
+          )}
+          {DEV_UI_ENABLED &&
+            serverHealthy &&
+            (skipToolsCheck ||
+              Boolean(gitCheckResult?.git.ok && gitCheckResult?.lfs.ok)) && (
+              <button
+                type="button"
+                className="ghost"
+                onClick={() => {
+                  setDevProceedReady(false);
+                  scheduleScreenTransition("login");
+                }}
+                disabled={!devProceedReady}
+              >
+                다음으로 이동
+              </button>
+            )}
+          {DEV_UI_ENABLED && (
+            <button
+              type="button"
+              className="ghost"
+              onClick={() => {
+                setSimulateToolsMissing((prev) => {
+                  const next = !prev;
+                  simulateToolsMissingRef.current = next;
+                  return next;
+                });
+                gitCheckedRef.current = false;
+                void runGitCheck(true);
+              }}
+            >
+              {simulateToolsMissing ? "Git/LFS 시뮬레이션 해제" : "Git/LFS 미설치 시뮬레이션"}
+            </button>
+          )}
+          {DEV_UI_ENABLED && (
+            <button
+              type="button"
+              className="ghost"
+              onClick={runDevInstallSimulation}
+              disabled={simulateInstallProgress || syncInProgress || installInProgress}
+            >
+              {simulateInstallProgress ? "설치 진행 시뮬레이션 중..." : "설치 진행 시뮬레이션"}
+            </button>
+          )}
+        </section>
+      )}
+
+      {screen === "login" && (
+        <section className="card hero">
+          <h2>로그인</h2>
+          <p className="status idle">로그인 필요</p>
+          <div className="login-form">
+            <input
+              type="text"
+              placeholder="아이디"
+              value={loginId}
+              onChange={(event) => setLoginId(event.target.value)}
+            />
+            <input
+              type="password"
+              placeholder="비밀번호"
+              value={loginPassword}
+              onChange={(event) => setLoginPassword(event.target.value)}
+            />
+          </div>
+          <button type="button" onClick={handleLogin} disabled={profileLoading}>
+            {profileLoading ? "프로필 조회 중..." : "로그인"}
+          </button>
+          <div className="link-row">
+            <button
+              type="button"
+              className="ghost"
+              onClick={() => setScreen("signup")}
+            >
+              회원가입
+            </button>
+            <button
+              type="button"
+              className="ghost"
+              onClick={() => setScreen("resetPassword")}
+            >
+              비밀번호 변경
+            </button>
+          </div>
+        </section>
+      )}
+
+      {screen === "signup" && (
+        <section className="card hero">
+          <h2>회원가입</h2>
+          <p className="status idle">관리자 승인 필요</p>
+          <p className="notice">
+            회원가입 후 서버 관리자 승인이 완료되어야 로그인 가능합니다.
+          </p>
+          <div className="login-form">
+            <input
+              type="text"
+              placeholder="아이디"
+              value={signupId}
+              onChange={(e) => setSignupId(e.target.value)}
+            />
+            <input
+              type="password"
+              placeholder="비밀번호"
+              value={signupPassword}
+              onChange={(e) => setSignupPassword(e.target.value)}
+            />
+            <input
+              type="password"
+              placeholder="비밀번호 확인"
+              value={confirmPassword}
+              onChange={(e) => setConfirmPassword(e.target.value)}
+            />
+          </div>
+          <button type="button" onClick={handleSignup} disabled={profileLoading}>
+            {profileLoading ? "가입 요청 중..." : "회원가입 요청"}
+          </button>
+          <button type="button" className="ghost" onClick={() => setScreen("login")}>
+            로그인으로 돌아가기
+          </button>
+        </section>
+      )}
+
+      {screen === "resetPassword" && (
+        <section className="card hero">
+          <h2>비밀번호 변경</h2>
+          <p className="status idle">본인 확인 필요</p>
+          <div className="login-form">
+            <input type="text" placeholder="아이디" />
+            <input type="password" placeholder="기존 비밀번호" />
+            <input type="password" placeholder="새 비밀번호" />
+            <input type="password" placeholder="새 비밀번호 확인" />
+          </div>
+          <button type="button" onClick={handlePasswordReset}>
+            비밀번호 변경 요청
+          </button>
+          <button type="button" className="ghost" onClick={() => setScreen("login")}>
+            로그인으로 돌아가기
+          </button>
+        </section>
+      )}
+
+      {screen === "main" && (
+        <main className="main-layout">
+          <section className="card top-bar">
+            <div className="profile-summary">
+              <div className="profile-title">
+                <span className="label">프로필</span>
+                <span className="profile-name">
+                  {profile?.nickname ?? profile?.username ?? "-"}
+                </span>
+              </div>
+              <div className="profile-meta">
+                <span>아이디: {profile?.username ?? "-"}</span>
+                <span>레벨: {typeof profile?.level === "number" ? profile.level : "-"}</span>
+                {profile?.side && <span>진영: {profile.side}</span>}
+              </div>
+            </div>
+            <div className="profile-actions">
+              <button type="button" onClick={handleProfileDownload} disabled={profileActionInProgress}>
+                {profileActionInProgress ? "처리 중..." : "다운로드"}
+              </button>
+              <button
+                type="button"
+                className="ghost"
+                onClick={handleProfileReset}
+                disabled={profileActionInProgress}
+              >
+                리셋
+              </button>
+              <button type="button" className="ghost" onClick={handleLogout}>
+                로그아웃
+              </button>
+            </div>
+          </section>
+
+          <section className="card spt-runner-card">
+            <div className="section-head">
+              <h2>SPT 설정</h2>
+              <button
+                type="button"
+                className="launch-button-header"
+                onClick={handleLaunch}
+                disabled={!startReady}
+              >
+                <span className="launch-icon">🚀</span>
+                <div className="launch-info">
+                  <span className="launch-text">{syncInProgress ? "동기화 중..." : "게임 시작"}</span>
+                  {/* <span className="launch-sub">Server & Launcher</span> */}
+                </div>
+              </button>
+            </div>
+
+            <div className="spt-rows-container">
+              {/* Install Path Row */}
+              <div className="spt-row">
+                <div className="row-header">
+                  <span className="label">설치 경로</span>
+                  <span className={`status ${sptInstallInfo?.ok ? "ok" : "blocked"}`}>
+                    {sptInstallInfo?.ok ? "확인됨" : "확인 필요"}
+                  </span>
+                </div>
+                <div className="row-body">
+                  <span className="value" title={sptInstallInfo?.path}>{sptInstallInfo?.path ?? "-"}</span>
+                  {sptInstallInfo?.source && (
+                    <span className="sub-helper">
+                      ({sptInstallInfo.source === "auto" ? "자동" : "수동"})
+                    </span>
+                  )}
+                </div>
+                <div className="row-controls">
+                  <button
+                    type="button"
+                    className="ghost icon-button"
+                    onClick={async () => {
+                      if (!window.sptLauncher?.pickSptInstallPath) {
+                        window.alert("준비 안됨");
+                        return;
+                      }
+                      const result = await window.sptLauncher.pickSptInstallPath();
+                      if (!result.ok && result.error === "invalid_spt_path") {
+                        setSptInstallMessage("유효하지 않은 SPT 폴더입니다.");
+                        return;
+                      }
+                      setSptInstallMessage(undefined);
+                      await runSptInstallCheck();
+                    }}
+                    title="경로 변경"
+                  >
+                    📂
+                  </button>
+                  <button type="button" className="ghost" onClick={runSptInstallCheck}>
+                    재확인
+                  </button>
+                </div>
+              </div>
+
+              {/* Mod Version Row */}
+              <div className="spt-row">
+                <div className="row-header">
+                  <span className="label">모드 버전</span>
+                  <span className={`status ${modStatusClass}`}>{modStatusLabel}</span>
+                </div>
+                <div className="row-body">
+                  <span className="value">
+                    {modVersionStatus?.currentTag ?? "-"} → {modVersionStatus?.latestTag ?? "-"}
+                  </span>
+                  {modVersionStatus?.latestMinorTags && modVersionStatus.latestMinorTags.length > 0 && (
+                    <span className="sub-helper">
+                      (+{modVersionStatus.latestMinorTags.length} 패치)
+                    </span>
+                  )}
+                </div>
+                <div className="row-controls">
+                  <select
+                    value={selectedModTag}
+                    onChange={(event) => setSelectedModTag(event.target.value)}
+                    disabled={modTagOptions.length === 0 || syncInProgress}
+                    className="version-select"
+                  >
+                    <option value="">선택...</option>
+                    {modTagOptions.map((tag) => (
+                      <option key={tag} value={tag}>{tag}</option>
+                    ))}
+                  </select>
+                  <button
+                    type="button"
+                    className="ghost"
+                    onClick={() => performModSync("optional", selectedModTag)}
+                    disabled={syncInProgress || !selectedModTag}
+                    title="선택 버전 적용"
+                  >
+                    적용
+                  </button>
+                  <div className="sync-menu">
+                    <button
+                      type="button"
+                      className="ghost icon-button"
+                      onClick={() => performModSync("optional")}
+                      disabled={syncInProgress || !modVersionStatus?.latestTag}
+                      title="최신 동기화"
+                    >
+                      ⟳
+                    </button>
+                    {/* Hover menu logic handled by CSS usually, keeping simple for now */}
+                  </div>
+                </div>
+              </div>
+            </div>
+
+            {/* Notices Area */}
+            <div className="notices-area">
+              {modVersionStatus?.status === "majorMinorMismatch" && (
+                <div className="notice warning">⚠️ 버전 불일치! 실행 시 자동 동기화됩니다.</div>
+              )}
+              {modVersionStatus?.status === "patchMismatch" && (
+                <div className="notice info">ℹ️ 새 패치가 있습니다.</div>
+              )}
+              {sptInstallMessage && <div className="notice error">{sptInstallMessage}</div>}
+            </div>
+          </section>
+
+          <footer className="footer">
+            <div className="tool-led">
+              <span className="tool-label">서버</span>
+              <span className={`led ${serverStatusLedClass}`} aria-label="서버 상태" />
+            </div>
+            <div className="tool-led">
+              <span className="tool-label">Git</span>
+              <span className={`led ${gitLedClass}`} aria-label="Git 상태" />
+            </div>
+            <div className="tool-led">
+              <span className="tool-label">LFS</span>
+              <span className={`led ${lfsLedClass}`} aria-label="Git LFS 상태" />
+            </div>
+            <button type="button" className="ghost status-button" onClick={handleOpenToolsModal}>
+              상세 보기
+            </button>
+          </footer>
+        </main>
+      )}
+      {screen !== "serverCheck" && toolsModalOpen && (
+        <div className="modal-overlay" role="presentation" onClick={() => setToolsModalOpen(false)}>
+          <section
+            className="modal"
+            role="dialog"
+            aria-modal="true"
+            aria-label="도구 상태"
+            onClick={(event) => event.stopPropagation()}
+          >
+            <header className="modal-header">
+              <h3>도구 상태</h3>
+              <button type="button" className="ghost" onClick={() => setToolsModalOpen(false)}>
+                닫기
+              </button>
+            </header>
+            <div className="modal-body">
+              <div className="modal-row">
+                <span className="label">Git</span>
+                <span className={`led ${gitLedClass}`} aria-label="Git 상태" />
+              </div>
+              <div className="modal-row">
+                <span className="label">Git LFS</span>
+                <span className={`led ${lfsLedClass}`} aria-label="Git LFS 상태" />
+              </div>
+              <div className="modal-actions">
+                <button type="button" onClick={handleRecheckTools} disabled={gitCheckInProgress}>
+                  {gitCheckInProgress ? "점검 중..." : "재확인"}
+                </button>
+                <button type="button" className="ghost" onClick={handleInstallTools} disabled={installInProgress}>
+                  {installInProgress ? "설치 중..." : "자동 설치"}
+                </button>
+                <button type="button" className="ghost" onClick={handleFetchGitPaths} disabled={gitPathsLoading}>
+                  {gitPathsLoading ? "확인 중..." : "경로 확인"}
+                </button>
+              </div>
+              {gitCheckResult && !(gitCheckResult.git.ok && gitCheckResult.lfs.ok) && (
+                <div className="notice">
+                  <strong>도구 설치 필요</strong>
+                  <div className="modal-help">
+                    Git/Git LFS가 감지되지 않았습니다. 자동 설치(Windows) 또는 수동 설치 후 재확인해주세요.
+                  </div>
+                </div>
+              )}
+              {installMessage && <div className="notice">{installMessage}</div>}
+              {gitPathsResult && (
+                <div className="notice">
+                  <strong>경로 확인</strong>
+                  <div className="modal-help">
+                    <div>Git: {gitPathsResult.git.ok ? gitPathsResult.git.path : gitPathsResult.git.error}</div>
+                    <div>Git LFS: {gitPathsResult.lfs.ok ? gitPathsResult.lfs.path : gitPathsResult.lfs.error}</div>
+                  </div>
+                </div>
+              )}
+            </div>
+          </section>
+        </div>
+      )}
+
+      {(syncInProgress || syncResult) && (
+        <div className="modal-overlay" role="presentation">
+          <section className="modal" onClick={(e) => e.stopPropagation()}>
+            <header className="modal-header">
+              <h3>
+                {syncResult
+                  ? (syncResult.ok ? (modalTitle.replace("중...", "완료")) : (syncResult.error ? `오류: ${syncResult.error}` : "오류 발생"))
+                  : modalTitle}
+              </h3>
+              {!syncInProgress && (
+                <button type="button" className="ghost" onClick={closeSyncModal}>
+                  닫기
+                </button>
+              )}
+            </header>
+            <div className="modal-body">
+              {syncProgress?.progress && (
+                <div className="sync-progress">
+                  <div className="sync-progress-header">
+                    <span>진행률(Progress)</span>
+                    <span>{syncProgress.progress.percent}%</span>
+                  </div>
+                  <div className="sync-progress-bar">
+                    <div
+                      className="sync-progress-fill"
+                      style={{ width: `${syncProgress.progress.percent}%` }}
+                    />
+                  </div>
+                  {syncProgress.stepName && (
+                    <div className="sync-progress-step">
+                      현재 단계(Current Step): {getStepDisplayInfo(syncProgress.stepName).title}
+                    </div>
+                  )}
+                </div>
+              )}
+              <div className="sync-steps">
+                {syncSteps.map((step, idx) => {
+                  const info = getStepDisplayInfo(step.name);
+                  const stepClass =
+                    step.status === "running" ? "running" : step.ok ? "ok" : "fail";
+                  const stepIcon =
+                    step.status === "running" ? "⏳" : step.ok ? "✅" : "❌";
+                  return (
+                    <div key={idx} className={`sync-step ${stepClass}`}>
+                      <span className="step-number">{idx + 1}.</span>
+                      <div className="step-content">
+                        <div className="step-title">{info.title}</div>
+                        <div className="step-command">{info.command}</div>
+                        {!step.ok && step.message && (
+                          <div className="step-msg">오류(Error): {step.message}</div>
+                        )}
+                      </div>
+                      <span className="step-icon">{stepIcon}</span>
+                    </div>
+                  );
+                })}
+                {syncInProgress && <div className="spinner-row">
+                  <span className="spinner">⏳</span>
+                  <span>작업 진행 중...</span>
+                </div>}
+              </div>
+              {syncResult && (
+                <div className={`notice ${syncResult.ok ? "info" : "error"}`}>
+                  {syncResult.ok ? "모드 적용이 완료되었습니다." : (syncResult.error ? `실패: ${syncResult.error}` : "오류가 발생했습니다.")}
+                </div>
+              )}
+            </div>
+
+          </section>
+        </div>
+      )}
+    </div>
+  );
+};
+
+export default App;
diff --git a/src/renderer/App.tsx.patch b/src/renderer/App.tsx.patch
new file mode 100644
index 0000000..160b058
--- /dev/null
+++ b/src/renderer/App.tsx.patch
@@ -0,0 +1,10 @@
+--- src/renderer/App.tsx
++++ src/renderer/App.tsx
+@@ -49,6 +49,7 @@
+         // MOCK For Browser testing since we hit CORS issues
+         if (window.location.protocol === 'http:') {
+           setServerStatus('ready');
++          return;
+         }
+ 
+         const result = await window.sptLauncher.checkServerVersion();
diff --git a/src/renderer/App.tsx.rej b/src/renderer/App.tsx.rej
new file mode 100644
index 0000000..e43d142
--- /dev/null
+++ b/src/renderer/App.tsx.rej
@@ -0,0 +1,8 @@
+@@ -49,6 +49,7 @@
+         // MOCK For Browser testing since we hit CORS issues
+         if (window.location.protocol === 'http:') {
+           setServerStatus('ready');
++          return;
+         }
+ 
+         const result = await window.sptLauncher.checkServerVersion();
diff --git a/src/renderer/vite-env.d.ts b/src/renderer/vite-env.d.ts
index 7260a2e..ff4ca0d 100644
--- a/src/renderer/vite-env.d.ts
+++ b/src/renderer/vite-env.d.ts
@@ -121,7 +121,21 @@ interface Window {
       path?: string;
       error?: string;
     }>;
-    fetchProfile: (payload: { username: string }) => Promise<{
+    login: (payload: { username: string; password?: string }) => Promise<{
+      ok: boolean;
+      status?: number;
+      data?: unknown;
+      error?: string;
+      url: string;
+    }>;
+    register: (payload: { username: string; password?: string }) => Promise<{
+      ok: boolean;
+      status?: number;
+      data?: unknown;
+      error?: string;
+      url: string;
+    }>;
+    fetchProfile: (payload: { username: string; password?: string }) => Promise<{
       ok: boolean;
       status?: number;
       data?: unknown;
diff --git a/src/shared/config.ts b/src/shared/config.ts
index acb01b1..d528743 100644
--- a/src/shared/config.ts
+++ b/src/shared/config.ts
@@ -1,5 +1,5 @@
 export const APP_CONFIG = {
-  serverBaseUrl: "https://pandoli365.com:5069",
+  serverBaseUrl: "https://127.0.0.1:6969",
   serverHealthcheckPath: "/launcher/ping",
   serverHealthcheckTimeoutMs: 2000,
   serverRequestTimeoutMs: 4000,
diff --git a/test-auth-deflate.js b/test-auth-deflate.js
new file mode 100644
index 0000000..a563807
--- /dev/null
+++ b/test-auth-deflate.js
@@ -0,0 +1,88 @@
+const https = require('https');
+const zlib = require('zlib');
+
+const agent = new https.Agent({ rejectUnauthorized: false });
+
+const makeRequest = (path, data, cookie) => {
+  return new Promise((resolve, reject) => {
+    const payload = JSON.stringify(data);
+    const deflated = zlib.deflateSync(payload);
+
+    const headers = {
+      'Content-Type': 'application/json',
+      'Accept-Encoding': 'deflate',
+      'Expect': '100-continue'
+    };
+    if (cookie) {
+      headers['Cookie'] = cookie;
+    }
+
+    const req = https.request({
+      hostname: '127.0.0.1',
+      port: 6969,
+      path: path,
+      method: 'POST',
+      headers: headers,
+      agent
+    }, (res) => {
+      const chunks = [];
+      res.on('data', chunk => chunks.push(chunk));
+      res.on('end', () => {
+        const buffer = Buffer.concat(chunks);
+        let body = '';
+        if (buffer.length > 0) {
+          try {
+            body = zlib.inflateSync(buffer).toString();
+          } catch (e) {
+            body = buffer.toString();
+          }
+        }
+        resolve({ status: res.statusCode, body });
+      });
+    });
+
+    req.on('error', reject);
+    req.write(deflated);
+    req.end();
+  });
+};
+
+async function testFlow() {
+  const user = 'testuser' + Math.floor(Math.random() * 1000);
+  const pass = 'password123';
+
+  console.log(`Registering new user: ${user}`);
+  const regRes = await makeRequest('/launcher/profile/register', {
+    username: user,
+    password: pass,
+    edition: 'Standard'
+  });
+  console.log("Registration Response:", regRes.status, regRes.body);
+
+  if (regRes.status !== 200 || regRes.body === 'FAILED') {
+    console.log("Registration failed, stopping.");
+    return;
+  }
+
+  console.log("\nLogging in with new user...");
+  const loginRes = await makeRequest('/launcher/profile/login', {
+    username: user,
+    password: pass
+  });
+  console.log("Login Response:", loginRes.status, loginRes.body);
+
+  if (loginRes.status !== 200 || loginRes.body === 'FAILED') {
+    console.log("Login failed, stopping.");
+    return;
+  }
+
+  const sessionId = loginRes.body;
+
+  console.log("\nFetching profile info...");
+  const infoRes = await makeRequest('/launcher/profile/info', {
+    username: user
+  }, `PHPSESSID=${sessionId}`);
+  console.log("Info Response:", infoRes.status, infoRes.body);
+}
+
+testFlow().catch(console.error);
diff --git a/test-auth.js b/test-auth.js
new file mode 100644
index 0000000..d7fc989
--- /dev/null
+++ b/test-auth.js
@@ -0,0 +1,45 @@
+const http = require('http');
+const https = require('https');
+const zlib = require('zlib');
+
+async function sendRequest(path, data) {
+  const payload = JSON.stringify(data);
+
+  const options = {
+    hostname: '127.0.0.1',
+    port: 6969,
+    path: path,
+    method: 'POST',
+    rejectUnauthorized: false,
+    headers: {
+      'Content-Type': 'application/json',
+      'Content-Length': Buffer.byteLength(payload),
+      'Accept-Encoding': 'identity',
+      'requestcompressed': '0',
+      'responsecompressed': '0'
+    }
+  };
+
+  return new Promise((resolve, reject) => {
+    const req = https.request(options, (res) => {
+      let result = '';
+      res.on('data', d => result += d);
+      res.on('end', () => resolve({ status: res.statusCode, body: result }));
+    });
+    req.on('error', reject);
+    req.write(payload); // We pass uncompressed for now using requestcompressed: 0
+    req.end();
+  });
+}
+
+async function run() {
+  console.log("Registering...");
+  const regRes = await sendRequest('/launcher/profile/register', { username: 'testuser3', password: 'testpassword3', edition: 'Standard' });
+  console.log(regRes);
+
+  console.log("Logging in...");
+  const loginRes = await sendRequest('/launcher/profile/login', { username: 'testuser3', password: 'testpassword3' });
+  console.log(loginRes);
+}
+
+run();
diff --git a/test-signup-login.js b/test-signup-login.js
new file mode 100644
index 0000000..8e4b83d
--- /dev/null
+++ b/test-signup-login.js
@@ -0,0 +1,54 @@
+const https = require('https');
+
+const agent = new https.Agent({ rejectUnauthorized: false });
+
+const makeRequest = (path, data) => {
+  return new Promise((resolve, reject) => {
+    const payload = JSON.stringify(data);
+    const req = https.request({
+      hostname: '127.0.0.1',
+      port: 6969,
+      path: path,
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'Content-Length': Buffer.byteLength(payload)
+      },
+      agent
+    }, (res) => {
+      let body = '';
+      res.on('data', chunk => body += chunk);
+      res.on('end', () => resolve({ status: res.statusCode, body }));
+    });
+    
+    req.on('error', reject);
+    req.write(payload);
+    req.end();
+  });
+};
+
+async function testFlow() {
+  console.log("Registering new user...");
+  const regRes = await makeRequest('/launcher/profile/register', {
+    username: 'newuser123',
+    password: 'newpass123',
+    edition: 'Standard'
+  });
+  console.log("Registration:", regRes);
+
+  console.log("Logging in with new user...");
+  const loginRes = await makeRequest('/launcher/profile/login', {
+    username: 'newuser123',
+    password: 'newpass123'
+  });
+  console.log("Login:", loginRes);
+  const sessionId = loginRes.body;
+
+  console.log("Fetching profile info...");
+  const infoRes = await makeRequest('/launcher/profile/info', {
+    username: 'newuser123'
+  });
+  console.log("Info:", infoRes);
+}
+
+testFlow().catch(console.error);