🧭 fix: Subdirectory Deployment Auth Redirect Path Doubling (#12077)

* fix: subdirectory redirects

* fix: use path-segment boundary check when stripping BASE_URL prefix

A bare `startsWith(BASE_URL)` matches on character prefix, not path
segments. With BASE_URL="/chat", a path like "/chatroom/c/abc" would
incorrectly strip to "room/c/abc" (no leading slash). Guard with an
exact-match-or-slash check: `p === BASE_URL || p.startsWith(BASE_URL + '/')`.

Also removes the dead `BASE_URL !== '/'` guard — module init already
converts '/' to ''.

* test: add path-segment boundary tests and clarify subdirectory coverage

- Add /chatroom, /chatbot, /app/chatroom regression tests to verify
  BASE_URL stripping only matches on segment boundaries
- Clarify useAuthRedirect subdirectory test documents React Router
  basename behavior (BASE_URL stripping tested in api-endpoints-subdir)
- Use `delete proc.browser` instead of undefined assignment for cleanup
- Add rationale to eslint-disable comment for isolateModules require

* fix: use relative path and correct instructions in subdirectory test script

- Replace hardcoded /home/danny/LibreChat/.env with repo-root-relative
  path so the script works from any checkout location
- Update instructions to use production build (npm run build && npm run
  backend) since nginx proxies to :3080 which only serves the SPA after
  a full build, not during frontend:dev on :3090

* fix: skip pointless redirect_to=/ for root path and fix jsdom 26+ compat

buildLoginRedirectUrl now returns plain /login when the resolved path
is root — redirect_to=/ adds no value since / immediately redirects
to /c/new after login anyway.

Also rewrites api-endpoints.spec.ts to use window.history.replaceState
instead of Object.defineProperty(window, 'location', ...) which jsdom
26+ no longer allows.

* test: fix request-interceptor.spec.ts for jsdom 26+ compatibility

Switch from jsdom to happy-dom environment which allows
Object.defineProperty on window.location. jsdom 26+ made
location non-configurable, breaking all 8 tests in this file.

* chore: update browser property handling in api-endpoints-subdir test

Changed the handling of the `proc.browser` property from deletion to setting it to false, ensuring compatibility with the current testing environment.

* chore: update backend restart instructions in test subdirectory setup script

Changed the instruction for restarting the backend from "npm run backend:dev" to "npm run backend" to reflect the correct command for the current setup.

* refactor: ensure proper cleanup in loadModuleWithBase function

Wrapped the module loading logic in a try-finally block to guarantee that the `proc.browser` property is reset to false and the base element is removed, improving reliability in the testing environment.

* refactor: improve browser property handling in loadModuleWithBase function

Revised the management of the `proc.browser` property to store the original value before modification, ensuring it is restored correctly after module loading. This enhances the reliability of the testing environment.

config/test-subdirectory-setup.sh

@@ -0,0 +1,144 @@
+#!/usr/bin/env bash
+# =============================================================================
+# Test script for verifying subdirectory deployment (e.g., /chat/)
+#
+# Prerequisites:
+#   - nginx installed: sudo apt install nginx
+#   - LibreChat built:  npm run build
+#   - Backend running:  npm run backend (serves built SPA + API on port 3080)
+#
+# Usage:
+#   1. Build + start:        npm run build && npm run backend
+#   2. Run this script:      bash config/test-subdirectory-setup.sh start
+#   3. Open browser:         http://localhost:8080/chat/
+#   4. Cleanup:              bash config/test-subdirectory-setup.sh stop
+#
+# What to verify:
+#   - Accessing http://localhost:8080/chat/ should redirect to /chat/login
+#     (NOT /chat/chat/login)
+#   - After login, navigating to protected routes should work
+#   - Logging out and being redirected should not double the path
+# =============================================================================
+
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+NGINX_CONF="/tmp/librechat-subdir-test-nginx.conf"
+NGINX_PID="/tmp/librechat-subdir-test-nginx.pid"
+
+ENV_FILE="${REPO_ROOT}/.env"
+
+write_nginx_conf() {
+  cat > "$NGINX_CONF" << 'NGINX'
+worker_processes 1;
+pid /tmp/librechat-subdir-test-nginx.pid;
+error_log /tmp/librechat-subdir-test-nginx-error.log warn;
+
+events {
+    worker_connections 64;
+}
+
+http {
+    access_log /tmp/librechat-subdir-test-nginx-access.log;
+
+    map $http_upgrade $connection_upgrade {
+        default upgrade;
+        ''      close;
+    }
+
+    server {
+        listen 8080;
+        server_name localhost;
+
+        # Subdirectory proxy: strip /chat/ prefix and forward to backend
+        location /chat/ {
+            proxy_pass http://127.0.0.1:3080/;
+            proxy_http_version 1.1;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection $connection_upgrade;
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+            proxy_cache_bypass $http_upgrade;
+        }
+
+        # Redirect bare /chat to /chat/
+        location = /chat {
+            return 301 /chat/;
+        }
+    }
+}
+NGINX
+}
+
+start() {
+    echo "--- Setting up subdirectory test environment ---"
+
+    # Backup .env if it exists and doesn't have our marker
+    if [ -f "$ENV_FILE" ] && ! grep -q '## SUBDIR_TEST_MARKER' "$ENV_FILE"; then
+        cp "$ENV_FILE" "${ENV_FILE}.bak-subdir-test"
+        echo "Backed up .env to .env.bak-subdir-test"
+    fi
+
+    # Ensure DOMAIN_CLIENT and DOMAIN_SERVER are set for subdirectory
+    if ! grep -q 'DOMAIN_CLIENT=http://localhost:8080/chat' "$ENV_FILE" 2>/dev/null; then
+        echo ""
+        echo "You need to set these in your .env file:"
+        echo "  DOMAIN_CLIENT=http://localhost:8080/chat"
+        echo "  DOMAIN_SERVER=http://localhost:8080/chat"
+        echo ""
+        echo "Then restart the backend: npm run backend"
+        echo ""
+    fi
+
+    # Write and start nginx
+    write_nginx_conf
+    echo "Starting nginx on port 8080 with subdirectory /chat/ ..."
+
+    # Stop any existing test nginx
+    if [ -f "$NGINX_PID" ] && kill -0 "$(cat "$NGINX_PID")" 2>/dev/null; then
+        nginx -c "$NGINX_CONF" -s stop 2>/dev/null || true
+        sleep 1
+    fi
+
+    nginx -c "$NGINX_CONF"
+    echo "nginx started (PID: $(cat "$NGINX_PID" 2>/dev/null || echo 'unknown'))"
+    echo ""
+    echo "=== Test URLs ==="
+    echo "  Main:     http://localhost:8080/chat/"
+    echo "  Login:    http://localhost:8080/chat/login"
+    echo "  Expect:   Redirects should go to /chat/login, NOT /chat/chat/login"
+    echo ""
+    echo "=== Logs ==="
+    echo "  Access: /tmp/librechat-subdir-test-nginx-access.log"
+    echo "  Error:  /tmp/librechat-subdir-test-nginx-error.log"
+    echo ""
+    echo "Run '$0 stop' to clean up."
+}
+
+stop() {
+    echo "--- Cleaning up subdirectory test environment ---"
+
+    if [ -f "$NGINX_PID" ] && kill -0 "$(cat "$NGINX_PID")" 2>/dev/null; then
+        nginx -c "$NGINX_CONF" -s stop
+        echo "nginx stopped."
+    else
+        echo "nginx not running."
+    fi
+
+    rm -f "$NGINX_CONF" /tmp/librechat-subdir-test-nginx-*.log
+
+    if [ -f "${ENV_FILE}.bak-subdir-test" ]; then
+        echo "Restore .env backup: cp ${ENV_FILE}.bak-subdir-test ${ENV_FILE}"
+    fi
+}
+
+case "${1:-}" in
+    start) start ;;
+    stop)  stop ;;
+    *)
+        echo "Usage: $0 {start|stop}"
+        exit 1
+        ;;
+esac