diff --git a/tools/cli/open.ts b/tools/cli/open.ts
index 8d5dfc8..b747347 100644
--- a/tools/cli/open.ts
+++ b/tools/cli/open.ts
@@ -33,7 +33,12 @@ export async function readServerInfo(): Promise<ServerInfo | null> {
     // Legacy 3-line format: pid\nmode\nfilePath
     const lines = content.split('\n');
     if (lines.length >= 2 && !isNaN(Number(lines[0]))) {
-      return { version: 1, pid: Number(lines[0]), mode: lines[1] as any, port: PORT };
+      return {
+        version: 1,
+        pid: Number(lines[0]),
+        mode: lines[1] as any,
+        port: PORT,
+      };
     }
     // Corrupt — clean up
     await fs.unlink(PID_FILE).catch(() => {});
@@ -64,35 +69,72 @@ async function validateAndResolve(filePath: string): Promise<string> {
 
 // --- 2-state server detection ---
 
-async function isServerRunning(): Promise<{ running: boolean; info: ServerInfo | null }> {
-  const info = await readServerInfo();
-  if (!info) return { running: false, info: null };
-
-  // Check if process is alive
+async function probePort(): Promise<{
+  running: boolean;
+  info: ServerInfo | null;
+}> {
   try {
-    process.kill(info.pid, 0);
+    const res = await fetch(`http://localhost:${PORT}/api/health`, {
+      signal: AbortSignal.timeout(1000),
+    });
+    if (!res.ok) return { running: false, info: null };
+    const body = await res.json();
+    if (body.version !== 2) return { running: false, info: null };
+
+    // Recover PID file from health response
+    const recoveredInfo: ServerInfo = {
+      version: 2,
+      pid: body.pid,
+      mode: 'daemon',
+      port: PORT,
+    };
+    await writeServerInfo(recoveredInfo);
+    console.log(
+      `[vync] Discovered existing server (PID ${body.pid}), recovered PID file.`
+    );
+    return { running: true, info: recoveredInfo };
   } catch {
-    await fs.unlink(PID_FILE).catch(() => {});
     return { running: false, info: null };
   }
+}
 
-  // Health check
-  try {
-    const res = await fetch(`http://localhost:${info.port}/api/health`, {
-      signal: AbortSignal.timeout(1000),
-    });
-    if (res.ok) {
-      const body = await res.json();
-      if (body.version === 2) return { running: true, info };
-      // Old server -> stop it
-      await vyncStop();
-      return { running: false, info: null };
+async function isServerRunning(): Promise<{
+  running: boolean;
+  info: ServerInfo | null;
+}> {
+  const info = await readServerInfo();
+
+  if (info) {
+    // Check if process is alive
+    try {
+      process.kill(info.pid, 0);
+    } catch {
+      await fs.unlink(PID_FILE).catch(() => {});
+      // Fall through to port probe
+      return probePort();
     }
-  } catch {}
 
-  // PID alive but HTTP dead -> stale
-  await fs.unlink(PID_FILE).catch(() => {});
-  return { running: false, info: null };
+    // Health check
+    try {
+      const res = await fetch(`http://localhost:${info.port}/api/health`, {
+        signal: AbortSignal.timeout(1000),
+      });
+      if (res.ok) {
+        const body = await res.json();
+        if (body.version === 2) return { running: true, info };
+        // Old server -> stop it
+        await vyncStop();
+        return { running: false, info: null };
+      }
+    } catch {}
+
+    // PID alive but HTTP dead -> stale
+    await fs.unlink(PID_FILE).catch(() => {});
+    return { running: false, info: null };
+  }
+
+  // No PID file — probe port as fallback
+  return probePort();
 }
 
 // --- Helpers ---
@@ -105,13 +147,20 @@ async function registerFile(port: number, filePath: string): Promise<void> {
   });
   if (!res.ok) {
     const body = await res.json().catch(() => ({}));
-    throw new Error(`[vync] Registration failed: ${(body as any).error || res.statusText}`);
+    throw new Error(
+      `[vync] Registration failed: ${(body as any).error || res.statusText}`
+    );
   }
 }
 
-async function openBrowserWithFile(port: number, filePath: string): Promise<void> {
+async function openBrowserWithFile(
+  port: number,
+  filePath: string
+): Promise<void> {
   const openModule = await import('open');
-  await openModule.default(`http://localhost:${port}/?file=${encodeURIComponent(filePath)}`);
+  await openModule.default(
+    `http://localhost:${port}/?file=${encodeURIComponent(filePath)}`
+  );
 }
 
 // --- Startup helpers ---
@@ -144,7 +193,10 @@ async function runForeground(resolved: string): Promise<void> {
   });
 
   const { startServer } = await import('../server/server.js');
-  const { shutdown } = await startServer({ initialFile: resolved, openBrowser: true });
+  const { shutdown } = await startServer({
+    initialFile: resolved,
+    openBrowser: true,
+  });
 
   const cleanup = async () => {
     await shutdown();
@@ -182,7 +234,12 @@ async function runElectron(resolved: string): Promise<void> {
     process.exit(1);
   }
 
-  await writeServerInfo({ version: 2, pid: childPid, mode: 'electron', port: PORT });
+  await writeServerInfo({
+    version: 2,
+    pid: childPid,
+    mode: 'electron',
+    port: PORT,
+  });
   child.unref();
   fsSync.closeSync(logFd);
 
@@ -203,7 +260,24 @@ async function runElectron(resolved: string): Promise<void> {
     try {
       const res = await fetch(`${url}/api/health`);
       if (res.ok) {
-        console.log(`[vync] Vync app running (PID ${childPid})`);
+        const body = await res.json();
+        // Verify this is our server, not a ghost
+        if (body.pid !== childPid) {
+          // Ghost server detected — reuse it instead
+          console.log(
+            `[vync] Existing server found (PID ${body.pid}), reusing.`
+          );
+          await writeServerInfo({
+            version: 2,
+            pid: body.pid,
+            mode: 'daemon',
+            port: PORT,
+          });
+        } else {
+          console.log(`[vync] Vync app running (PID ${childPid})`);
+        }
+        // Register file (same as runDaemon)
+        await registerFile(PORT, resolved);
         console.log(`[vync] Log: ${LOG_FILE}`);
         return;
       }
@@ -256,7 +330,12 @@ async function runDaemon(resolved: string): Promise<void> {
   }
 
   // Save child PID (not this process's PID)
-  await writeServerInfo({ version: 2, pid: childPid, mode: 'daemon', port: PORT });
+  await writeServerInfo({
+    version: 2,
+    pid: childPid,
+    mode: 'daemon',
+    port: PORT,
+  });
   child.unref();
   fsSync.closeSync(logFd);
 
@@ -349,7 +428,9 @@ export async function vyncClose(
     const resolved = resolveVyncPath(filePath);
     try {
       const res = await fetch(
-        `http://localhost:${info.port}/api/files?file=${encodeURIComponent(resolved)}`,
+        `http://localhost:${info.port}/api/files?file=${encodeURIComponent(
+          resolved
+        )}`,
         { method: 'DELETE' }
       );
       if (res.ok) console.log(`[vync] Closed: ${resolved}`);
@@ -359,7 +440,9 @@ export async function vyncClose(
     }
   } else {
     try {
-      await fetch(`http://localhost:${info.port}/api/files?all=true`, { method: 'DELETE' });
+      await fetch(`http://localhost:${info.port}/api/files?all=true`, {
+        method: 'DELETE',
+      });
       console.log('[vync] All files closed.');
     } catch {
       console.error('[vync] Server not reachable.');
@@ -449,9 +532,7 @@ export async function vyncStop(): Promise<void> {
   }
 
   if (!portFree) {
-    console.error(
-      `[vync] Warning: port ${port} still in use after stop.`
-    );
+    console.error(`[vync] Warning: port ${port} still in use after stop.`);
   }
   console.log(`[vync] Server stopped (PID ${info.pid})`);
 }
diff --git a/tools/electron/main.ts b/tools/electron/main.ts
index 8648898..b42dc1c 100644
--- a/tools/electron/main.ts
+++ b/tools/electron/main.ts
@@ -94,9 +94,54 @@ async function openFile(filePath: string): Promise<void> {
         staticDir,
       });
     } catch (err: any) {
-      dialog.showErrorBox('Vync Error', err.message);
-      app.quit();
-      return;
+      // EADDRINUSE: try connecting to existing server
+      if (err.message.includes('already in use')) {
+        const existingUrl = 'http://localhost:3100';
+        try {
+          const res = await fetch(`${existingUrl}/api/health`, {
+            signal: AbortSignal.timeout(2000),
+          });
+          if (res.ok) {
+            const body = await res.json();
+            if (body.version === 2) {
+              // Reuse existing server (no shutdown responsibility)
+              serverHandle = { shutdown: async () => {}, url: existingUrl };
+              console.log(`[vync] Reusing existing server (PID ${body.pid})`);
+              // Register the file with existing server
+              await fetch(`${existingUrl}/api/files`, {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ filePath: resolved }),
+              });
+            } else {
+              dialog.showErrorBox(
+                'Vync Error',
+                'Incompatible server on port 3100'
+              );
+              app.quit();
+              return;
+            }
+          } else {
+            dialog.showErrorBox(
+              'Vync Error',
+              'Port 3100 in use by non-Vync process'
+            );
+            app.quit();
+            return;
+          }
+        } catch {
+          dialog.showErrorBox(
+            'Vync Error',
+            'Port 3100 in use but server not responding'
+          );
+          app.quit();
+          return;
+        }
+      } else {
+        dialog.showErrorBox('Vync Error', err.message);
+        app.quit();
+        return;
+      }
     }
   }
 
diff --git a/tools/server/server.ts b/tools/server/server.ts
index e24c128..9e2757b 100644
--- a/tools/server/server.ts
+++ b/tools/server/server.ts
@@ -3,7 +3,11 @@ import path from 'node:path';
 import express from 'express';
 import { createWsServer } from './ws-handler.js';
 import { FileRegistry } from './file-registry.js';
-import { addAllowedDir, createHostGuard, validateFilePath } from './security.js';
+import {
+  addAllowedDir,
+  createHostGuard,
+  validateFilePath,
+} from './security.js';
 import type { VyncFile } from '@vync/shared';
 
 const DEFAULT_PORT = 3100;
@@ -55,7 +59,12 @@ export async function startServer(
 
   // --- Health endpoint ---
   app.get('/api/health', (_req, res) => {
-    res.json({ version: 2, mode: 'hub', fileCount: registry.listFiles().length });
+    res.json({
+      version: 2,
+      mode: 'hub',
+      pid: process.pid,
+      fileCount: registry.listFiles().length,
+    });
   });
 
   // --- File registration API ---
@@ -79,7 +88,10 @@ export async function startServer(
         status: alreadyRegistered ? 'already_registered' : 'registered',
       });
     } catch (err: any) {
-      if (err.message.includes('outside allowed') || err.message.includes('Only .vync')) {
+      if (
+        err.message.includes('outside allowed') ||
+        err.message.includes('Only .vync')
+      ) {
         res.status(403).json({ error: err.message });
       } else if (err.message.includes('Maximum')) {
         res.status(429).json({ error: err.message });
@@ -116,7 +128,9 @@ export async function startServer(
   app.get('/api/sync', async (req, res) => {
     const filePath = req.query.file as string;
     if (!filePath) {
-      res.status(400).json({ error: 'file_required', files: registry.listFiles() });
+      res
+        .status(400)
+        .json({ error: 'file_required', files: registry.listFiles() });
       return;
     }
     const sync = registry.getSync(filePath);
@@ -194,7 +208,10 @@ export async function startServer(
     if (vite) await vite.close();
     await new Promise<void>((resolve) => {
       const timer = setTimeout(resolve, 3000);
-      server.close(() => { clearTimeout(timer); resolve(); });
+      server.close(() => {
+        clearTimeout(timer);
+        resolve();
+      });
     });
   };
 
@@ -221,7 +238,9 @@ export async function startServer(
 
   if (options.openBrowser && options.initialFile) {
     const openModule = await import('open');
-    await openModule.default(`${url}/?file=${encodeURIComponent(options.initialFile)}`);
+    await openModule.default(
+      `${url}/?file=${encodeURIComponent(options.initialFile)}`
+    );
   }
 
   return { shutdown, server, url, registry };
@@ -239,8 +258,14 @@ if (isDirectRun) {
 
   startServer({ initialFile: resolvedFile })
     .then(({ shutdown }) => {
-      process.on('SIGINT', async () => { await shutdown(); process.exit(0); });
-      process.on('SIGTERM', async () => { await shutdown(); process.exit(0); });
+      process.on('SIGINT', async () => {
+        await shutdown();
+        process.exit(0);
+      });
+      process.on('SIGTERM', async () => {
+        await shutdown();
+        process.exit(0);
+      });
     })
     .catch((err) => {
       console.error('[vync] Fatal error:', err.message);