fix: rewrite absolute /ui/assets/ paths when SERVER_ROOT_PATH is set

Some JS chunks in the packaged Next.js UI output use absolute paths like
"/ui/assets/logos/" instead of the litellm-asset-prefix token. When the
proxy is served under a sub-path (SERVER_ROOT_PATH=/web-llmgateway/v1),
those absolute paths are not rewritten, so browsers request
/{SERVER_ROOT_PATH}/assets/logos/... (without /ui) and receive 404s.

Add a targeted string replacement alongside the existing litellm-asset-prefix
substitution so that '"/ui/assets/' becomes '"{server_root_path}/ui/assets/'
in all text files under the UI directory.

Fixes https://github.com/BerriAI/litellm/issues/25283

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

litellm/proxy/proxy_server.py

@@ -1373,6 +1373,15 @@ try:
                             f"{server_root_path}",
                         )
 
+                        # Replace absolute /ui/assets/ paths with server_root_path-prefixed
+                        # equivalents so logo/asset requests include the root path prefix.
+                        # Some JS bundles emit absolute paths like "/ui/assets/logos/" which
+                        # resolve incorrectly when the app is served under a sub-path.
+                        modified_content = modified_content.replace(
+                            '"/ui/assets/',
+                            f'"{server_root_path}/ui/assets/',
+                        )
+
                         # Replace the /.well-known/litellm-ui-config with the server root path
                         modified_content = modified_content.replace(
                             "/litellm/.well-known/litellm-ui-config",

tests/test_litellm/proxy/test_server_root_path_ui_assets.py

@@ -0,0 +1,119 @@
+"""
+Tests for SERVER_ROOT_PATH rewriting of absolute /ui/assets/ paths in JS bundles.
+
+Regression test for https://github.com/BerriAI/litellm/issues/25283
+
+When LiteLLM is served under a sub-path (SERVER_ROOT_PATH=/web-llmgateway/v1),
+some JS chunks emit absolute paths like "/ui/assets/logos/" that the browser
+resolves without the sub-path prefix, causing 404s for logo assets.
+The startup path-rewriting logic must patch these absolute paths.
+"""
+
+import os
+
+
+def _apply_server_root_path_replacements(
+    ui_path: str,
+    server_root_path: str,
+    litellm_asset_prefix: str = "/litellm-asset-prefix",
+) -> None:
+    """Replicate the replacement logic from proxy_server.py for testing."""
+    skip_extensions = (".png", ".jpg", ".jpeg", ".gif", ".ico", ".woff", ".woff2", ".ttf", ".eot")
+    for root, _, files in os.walk(ui_path):
+        for filename in files:
+            if filename.endswith(skip_extensions):
+                continue
+            file_path = os.path.join(root, filename)
+            try:
+                with open(file_path, "r", encoding="utf-8") as f:
+                    content = f.read()
+                modified = content.replace(litellm_asset_prefix, server_root_path)
+                modified = modified.replace('"/ui/assets/', f'"{server_root_path}/ui/assets/')
+                modified = modified.replace(
+                    "/litellm/.well-known/litellm-ui-config",
+                    f"{server_root_path}/.well-known/litellm-ui-config",
+                )
+                with open(file_path, "w", encoding="utf-8") as f:
+                    f.write(modified)
+            except (UnicodeDecodeError, PermissionError, OSError):
+                continue
+
+
+def test_absolute_ui_asset_paths_rewritten_with_server_root_path(tmp_path):
+    """
+    JS bundles that use absolute "/ui/assets/logos/" paths should have those
+    paths rewritten to include SERVER_ROOT_PATH when it is set.
+
+    Reproduces: browser requests /{SERVER_ROOT_PATH}/assets/logos/... (404)
+    instead of /{SERVER_ROOT_PATH}/ui/assets/logos/... (200).
+    """
+    ui_path = tmp_path / "ui"
+    ui_path.mkdir()
+
+    # Simulate a JS chunk that uses an absolute /ui/assets/ path.
+    # This mirrors the pattern seen in the packaged UI output:
+    #   _next/static/chunks/0d219667baa010f5.js
+    js_file = ui_path / "_next" / "static" / "chunks" / "logos.js"
+    js_file.parent.mkdir(parents=True)
+    js_file.write_text('let eq="/ui/assets/logos/",r={github:`${eq}github.svg`}')
+
+    server_root_path = "/web-llmgateway/v1"
+    _apply_server_root_path_replacements(str(ui_path), server_root_path)
+
+    result = js_file.read_text()
+    assert f'"{server_root_path}/ui/assets/logos/"' in result, (
+        f"Absolute /ui/assets/ path not rewritten to include SERVER_ROOT_PATH. Got: {result}"
+    )
+    assert '"/ui/assets/logos/"' not in result, (
+        "Old absolute /ui/assets/ path should have been replaced"
+    )
+
+
+def test_litellm_asset_prefix_still_rewritten(tmp_path):
+    """Existing litellm-asset-prefix replacement must still work alongside the new fix."""
+    ui_path = tmp_path / "ui"
+    ui_path.mkdir()
+
+    js_file = ui_path / "bundle.js"
+    js_file.write_text(
+        'let t="/litellm-asset-prefix/_next/",eq="/ui/assets/logos/"'
+    )
+
+    server_root_path = "/myapp"
+    _apply_server_root_path_replacements(str(ui_path), server_root_path)
+
+    result = js_file.read_text()
+    assert f'"{server_root_path}/_next/"' in result
+    assert f'"{server_root_path}/ui/assets/logos/"' in result
+    assert '"/litellm-asset-prefix/_next/"' not in result
+    assert '"/ui/assets/logos/"' not in result
+
+
+def test_no_replacement_when_no_server_root_path(tmp_path):
+    """When server_root_path is empty, paths should remain unchanged."""
+    ui_path = tmp_path / "ui"
+    ui_path.mkdir()
+
+    original = 'let eq="/ui/assets/logos/",r={}'
+    js_file = ui_path / "bundle.js"
+    js_file.write_text(original)
+
+    # Simulate the guard: only replace when server_root_path is non-empty
+    server_root_path = ""
+    if server_root_path and server_root_path != "/":
+        _apply_server_root_path_replacements(str(ui_path), server_root_path)
+
+    assert js_file.read_text() == original
+
+
+def test_binary_files_are_skipped(tmp_path):
+    """Image and font files must not be touched by the replacement logic."""
+    ui_path = tmp_path / "ui"
+    ui_path.mkdir()
+
+    png_file = ui_path / "logo.png"
+    png_file.write_bytes(b"\x89PNG\r\n\x1a\n")
+
+    _apply_server_root_path_replacements(str(ui_path), "/root")
+
+    assert png_file.read_bytes() == b"\x89PNG\r\n\x1a\n"