diff --git a/electron.vite.config.ts b/electron.vite.config.ts
index 85d784c6..5dfe03a6 100644
--- a/electron.vite.config.ts
+++ b/electron.vite.config.ts
@@ -2,6 +2,24 @@ import { defineConfig, externalizeDepsPlugin } from 'electron-vite'
 import react from '@vitejs/plugin-react'
 import tailwindcss from '@tailwindcss/vite'
 import { resolve } from 'path'
+import { execSync } from 'child_process'
+
+// Captured once at vite startup. Restart `npm run dev` after switching
+// branches if you want the title to update.
+function currentGitBranch(): string {
+  try {
+    return execSync('git rev-parse --abbrev-ref HEAD', {
+      cwd: __dirname,
+      stdio: ['pipe', 'pipe', 'ignore']
+    })
+      .toString()
+      .trim()
+  } catch {
+    return ''
+  }
+}
+
+const DEV_BRANCH = currentGitBranch()
 
 export default defineConfig({
   main: {
@@ -37,6 +55,9 @@ export default defineConfig({
   },
   renderer: {
     plugins: [react(), tailwindcss()],
+    define: {
+      __HARNESS_DEV_BRANCH__: JSON.stringify(DEV_BRANCH)
+    },
     build: {
       ssr: false
     }
diff --git a/src/renderer/components/Sidebar.tsx b/src/renderer/components/Sidebar.tsx
index 63b13116..dd248235 100644
--- a/src/renderer/components/Sidebar.tsx
+++ b/src/renderer/components/Sidebar.tsx
@@ -265,7 +265,12 @@ export function Sidebar({
       </svg>
       {/* Title bar drag region with app name — vertically aligned with traffic lights at y:12 */}
       <div className="drag-region h-10 relative shrink-0">
-        <span className="gradient-text text-xs font-semibold absolute left-20 top-[11px]">Harness</span>
+        <span className="absolute left-20 top-[11px] text-xs font-semibold whitespace-nowrap">
+          <span className="gradient-text">Harness</span>
+          {import.meta.env.DEV && __HARNESS_DEV_BRANCH__ && (
+            <span className="text-faint font-normal ml-1">({__HARNESS_DEV_BRANCH__})</span>
+          )}
+        </span>
       </div>
 
       {/* Command Center entry */}
diff --git a/src/renderer/vite-env.d.ts b/src/renderer/vite-env.d.ts
index 11f02fe2..42f7cd77 100644
--- a/src/renderer/vite-env.d.ts
+++ b/src/renderer/vite-env.d.ts
@@ -1 +1,3 @@
 /// <reference types="vite/client" />
+
+declare const __HARNESS_DEV_BRANCH__: string