diff --git a/tests/test_litellm/ui/test_ui_build_pinning_lit_2723.py b/tests/test_litellm/ui/test_ui_build_pinning_lit_2723.py
new file mode 100644
index 000000000000..17a11bb44d7c
--- /dev/null
+++ b/tests/test_litellm/ui/test_ui_build_pinning_lit_2723.py
@@ -0,0 +1,62 @@
+"""
+Regression tests for LIT-2723 - pin the UI build output layout and Node version
+so committed `litellm/proxy/_experimental/out/` diffs stop flipping between
+`<route>.html` and `<route>/index.html`, and so the build does not silently
+fall back to a non-v20 Node.
+
+These are file-level assertions on the build config + script. They do not run
+npm or restructure the export; they only guard the locking lines.
+"""
+
+from pathlib import Path
+
+
+REPO_ROOT = Path(__file__).resolve().parents[3]
+NEXT_CONFIG = REPO_ROOT / "ui" / "litellm-dashboard" / "next.config.mjs"
+BUILD_UI_SH = REPO_ROOT / "ui" / "litellm-dashboard" / "build_ui.sh"
+
+
+def test_next_config_pins_trailing_slash_true():
+    """next.config.mjs must declare `trailingSlash: true` so every build emits
+    the `<route>/index.html` directory-index layout. Flipping back to the
+    `<route>.html` form rewrites every file in `_experimental/out` and breaks
+    deployments that rely on directory-index routing (e.g. the MCP OAuth
+    callback)."""
+    assert NEXT_CONFIG.is_file(), f"next.config.mjs missing at {NEXT_CONFIG}"
+    text = NEXT_CONFIG.read_text()
+    assert "trailingSlash: true" in text or "trailingSlash:true" in text, (
+        "next.config.mjs must set `trailingSlash: true` (LIT-2723). "
+        "Removing it makes the static export flip back to the bare "
+        "<route>.html form on the next local build."
+    )
+
+
+def test_build_ui_sh_installs_node_v20_and_verifies():
+    """build_ui.sh must install v20 (not just `nvm use`), error-check both
+    steps, and verify `node -v` actually reports v20 before running the
+    build. Without these guards the script silently succeeds against any
+    Node version on PATH in non-interactive shells, and the committed
+    artifacts pick up the wrong Node."""
+    assert BUILD_UI_SH.is_file(), f"build_ui.sh missing at {BUILD_UI_SH}"
+    text = BUILD_UI_SH.read_text()
+
+    assert "nvm install v20" in text, (
+        "build_ui.sh must `nvm install v20` before `nvm use v20` - "
+        "`use` alone silently no-ops when v20 is not already installed."
+    )
+    assert "nvm install v20 failed" in text, (
+        "build_ui.sh must surface `nvm install v20` failure with an "
+        "error message and non-zero exit (LIT-2723)."
+    )
+    assert "Failed to switch to Node.js v20" in text, (
+        "build_ui.sh must surface `nvm use v20` failure with an error "
+        "message and non-zero exit."
+    )
+    assert "node -v" in text, (
+        "build_ui.sh must read `node -v` to verify the active Node "
+        "version after `nvm use v20`."
+    )
+    assert "v20." in text, (
+        "build_ui.sh must check that `node -v` output starts with "
+        "`v20.` and abort otherwise (LIT-2723)."
+    )
diff --git a/ui/litellm-dashboard/build_ui.sh b/ui/litellm-dashboard/build_ui.sh
index aa346c12edc4..faeb13efd4e3 100755
--- a/ui/litellm-dashboard/build_ui.sh
+++ b/ui/litellm-dashboard/build_ui.sh
@@ -22,15 +22,29 @@ if ! command -v nvm &> /dev/null; then
   [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
 fi
 
-# Use nvm to set the required Node.js version
-nvm use v20
+# Install + use the pinned Node.js version. `nvm use` alone silently no-ops
+# when v20 isn't installed in the current shell (e.g. non-interactive CI),
+# and the build then runs against whatever node is on PATH. Install first, use
+# second, and verify `node -v` actually reports v20 before continuing.
+if ! nvm install v20; then
+  echo "Error: nvm install v20 failed. Deployment aborted."
+  exit 1
+fi
 
-# Check if nvm use was successful
-if [ $? -ne 0 ]; then
+if ! nvm use v20; then
   echo "Error: Failed to switch to Node.js v20. Deployment aborted."
   exit 1
 fi
 
+NODE_VER="$(node -v 2>/dev/null || true)"
+case "$NODE_VER" in
+  v20.*) echo "Confirmed Node.js $NODE_VER" ;;
+  *)
+    echo "Error: expected Node.js v20.* but got '$NODE_VER'. Deployment aborted."
+    exit 1
+    ;;
+esac
+
 # print contents of ui_colors.json
 echo "Contents of ui_colors.json:"
 cat ui_colors.json
@@ -60,4 +74,6 @@ if [ $? -eq 0 ]; then
   echo "Deployment completed."
 else
   echo "Build failed. Deployment aborted."
+  exit 1
 fi
+
diff --git a/ui/litellm-dashboard/next.config.mjs b/ui/litellm-dashboard/next.config.mjs
index cfaeb24dc5d4..3d9b8e3463e4 100644
--- a/ui/litellm-dashboard/next.config.mjs
+++ b/ui/litellm-dashboard/next.config.mjs
@@ -7,6 +7,12 @@ const __dirname = path.dirname(__filename);
 
 const nextConfig = {
   output: "export",
+  // Pin the directory-index layout (<route>/index.html). Otherwise different
+  // Next.js patch versions or stale .next caches flip the export between
+  // foo.html and foo/index.html, producing massive rename-only diffs in
+  // litellm/proxy/_experimental/out and breaking deployments that rely on
+  // directory-index routing for nested paths (e.g. /ui/mcp/oauth/callback).
+  trailingSlash: true,
   // Required with output: "export" — default image optimizer runs only in server mode.
   // See https://nextjs.org/docs/messages/export-image-api
   images: {