diff --git a/backend/config/settings.py b/backend/config/settings.py
index 087c627..1efe311 100644
--- a/backend/config/settings.py
+++ b/backend/config/settings.py
@@ -3,6 +3,7 @@ Django settings for the J621 backend.
 """
 
 import os
+import subprocess
 from pathlib import Path
 
 from dotenv import load_dotenv
@@ -19,6 +20,24 @@ ALLOWED_HOSTS = [
     if host.strip()
 ]
 
+
+def _git_commit_hash():
+    """Short git hash of the running build, mirroring the original app."""
+    try:
+        return subprocess.check_output(
+            ["git", "rev-parse", "--short", "HEAD"],
+            cwd=BASE_DIR,
+            text=True,
+            stderr=subprocess.DEVNULL,
+        ).strip()
+    except (subprocess.SubprocessError, OSError):
+        return "unknown"
+
+
+GIT_COMMIT_HASH = _git_commit_hash()
+APP_ENV = "dev" if DEBUG else "prod"
+APP_VERSION = f"{APP_ENV} @ {GIT_COMMIT_HASH}"
+
 # Application definition
 
 INSTALLED_APPS = [
diff --git a/frontend/design.md_j621_frontend_spec.md b/frontend/design.md_j621_frontend_spec.md
index 94cc9de..288cd8e 100644
--- a/frontend/design.md_j621_frontend_spec.md
+++ b/frontend/design.md_j621_frontend_spec.md
@@ -1,6 +1,6 @@
 # DESIGN.md — J621 Frontend Design System & Architecture Specification
 
-> **Version:** 1.4.2-stable  
+> **Version:** the git commit hash of the build (e.g. `3f35330`)  
 > **Theme Foundation:** Catppuccin Mocha + e621 Authentic Taxonomy Architecture  
 > **Target Platform:** Desktop-first, fully responsive self-hosted home-server media web application (the library is a watched folder on disk, not a NAS appliance)  
 > **Reference Design System:** `Mocha Archive Terminal` (`{{DATA:DESIGN_SYSTEM:DESIGN_SYSTEM_3}}`)
@@ -79,12 +79,12 @@ All tag chips, counters, and sidebar taxonomy badges strictly adhere to e621's e
 - **Top App Bar (`#11111b`, height: 56px):**
   - Left: Brand mark `J621` badge (`#cba6f7`) followed by the **storage line** — the path of the watched folder that J621 indexes (e.g. `/mnt/media/library`). J621 is folder-based: this is just a path on disk, not a NAS/appliance indicator.
   - Center: Nav pills: `Library`, `Online`, `Pools`, `Followed`, `Upload`, `Duplicates`, and `Stats [STAFF]`.
-  - Right: System status pill with real backend values, never hardcoded: environment (`DEV`/`PROD`), the actual host OS, page generation time, and the total e621 API request time for that page load — e.g. `ENV: PROD · LINUX · 18ms (e621: 4ms)`. Followed by the user avatar.
+  - Right: System status pill with real backend values, never hardcoded: environment (`DEV`/`PROD`), git commit hash, the actual host OS, page generation time, and the total e621 API request time for that page load — e.g. `ENV: PROD · a1b2c3d · LINUX · 18ms (e621: 4ms)`. Followed by the user avatar.
 - **Global Footer Status Strip (`#11111b`, height: 32px):**
   - The strip placement is a proposal; its values are real and drawn from the existing stats data.
   - Left: the watched folder path — `📁 Local Storage: /mnt/media/library`.
   - Center: `⚡ Active Workers: N running | Queue: M pending` — the count of active optimization/ingest jobs and queued downloads (the original app surfaced this on its stats page; the footer simply keeps it visible).
-  - Right: the build actually running — `J621 <version>` / commit hash.
+  - Right: the running build — `<env> @ <git commit hash>` (e.g. `dev @ 3f35330`), matching the original app.
 - **Collapsible Sidebar (Behavior):**
   - **Closed by default** across all gallery and viewer views to prioritize screen real estate.
   - Toggled via `☰` button or quick keyboard shortcut (`Ctrl+B` or `⌘B`).
diff --git a/frontend/src/components/AppShell.tsx b/frontend/src/components/AppShell.tsx
index 2f1bd1f..1594a0d 100644
--- a/frontend/src/components/AppShell.tsx
+++ b/frontend/src/components/AppShell.tsx
@@ -2,6 +2,7 @@ import { LogOut } from "lucide-react";
 import { Link, NavLink, Outlet } from "react-router-dom";
 
 import { cn } from "@/lib/cn";
+import { APP_VERSION } from "@/lib/version";
 import { useAuth } from "@/store/auth";
 
 const navItems = [
@@ -21,9 +22,6 @@ export function AppShell() {
             <span className="rounded bg-ctp-mauve px-2 py-1 font-mono text-xs font-bold tracking-wide text-ctp-crust">
               J621
             </span>
-            <span className="hidden text-[11px] font-medium uppercase tracking-[0.14em] text-ctp-overlay0 md:block">
-              Mocha Archive Terminal
-            </span>
           </Link>
 
           <nav className="flex items-center gap-1">
@@ -47,6 +45,12 @@ export function AppShell() {
           </nav>
 
           <div className="ml-auto flex items-center gap-3">
+            <span
+              className="hidden font-mono text-[11px] text-ctp-overlay0 lg:block"
+              title="Running build"
+            >
+              {APP_VERSION}
+            </span>
             {user ? (
               <>
                 <div className="flex items-center gap-2">
diff --git a/frontend/src/lib/version.ts b/frontend/src/lib/version.ts
new file mode 100644
index 0000000..34e7467
--- /dev/null
+++ b/frontend/src/lib/version.ts
@@ -0,0 +1,5 @@
+declare const __GIT_COMMIT_HASH__: string;
+
+export const GIT_COMMIT_HASH = __GIT_COMMIT_HASH__;
+export const APP_ENV = import.meta.env.DEV ? "dev" : "prod";
+export const APP_VERSION = `${APP_ENV} @ ${GIT_COMMIT_HASH}`;
diff --git a/frontend/vite.config.ts b/frontend/vite.config.ts
index 5ac699a..63ba397 100644
--- a/frontend/vite.config.ts
+++ b/frontend/vite.config.ts
@@ -1,13 +1,30 @@
+import { execSync } from "node:child_process";
 import { fileURLToPath, URL } from "node:url";
 
 import tailwindcss from "@tailwindcss/vite";
 import react from "@vitejs/plugin-react";
 import { defineConfig } from "vite";
 
+function gitCommitHash(): string {
+  try {
+    return execSync("git rev-parse --short HEAD", {
+      cwd: fileURLToPath(new URL(".", import.meta.url)),
+      stdio: ["ignore", "pipe", "ignore"],
+    })
+      .toString()
+      .trim();
+  } catch {
+    return "unknown";
+  }
+}
+
 const backend = process.env.VITE_BACKEND ?? "http://127.0.0.1:8000";
 
 // https://vite.dev/config/
 export default defineConfig({
+  define: {
+    __GIT_COMMIT_HASH__: JSON.stringify(gitCommitHash()),
+  },
   plugins: [react(), tailwindcss()],
   resolve: {
     alias: {