chore: Add support for reversed proxy in adk web, users can use an optional param --root_path for proxy's path

Co-authored-by: Yifan Wang <wanyif@google.com> PiperOrigin-RevId: 826632932

Author: wyf7107

src/google/adk/cli/adk_web_server.py

@@ -436,6 +436,7 @@ def __init__(
  extra_plugins: Optional[list[str]] = None,
  logo_text: Optional[str] = None,
  logo_image_url: Optional[str] = None,
+ url_prefix: Optional[str] = None,
  ):
  self.agent_loader = agent_loader
  self.session_service = session_service
@@ -452,6 +453,7 @@ def __init__(
  self.runners_to_clean: set[str] = set()
  self.current_app_name_ref: SharedValue[str] = SharedValue(value="")
  self.runner_dict = {}
+ self.url_prefix = url_prefix
 
  async def get_runner_async(self, app_name: str) -> Runner:
  """Returns the cached runner for the given app."""
@@ -559,6 +561,7 @@ def _setup_runtime_config(self, web_assets_dir: str):
  " overwritten.",
  runtime_config_path,
  )
+ runtime_config["backendUrl"] = self.url_prefix if self.url_prefix else ""
 
  # Set custom logo config.
  if self.logo_text or self.logo_image_url:
@@ -1562,6 +1565,10 @@ async def process_messages():
  mimetypes.add_type("application/javascript", ".js", True)
  mimetypes.add_type("text/javascript", ".js", True)
 
+ redirect_dev_ui_url = (
+ self.url_prefix + "/dev-ui/" if self.url_prefix else "/dev-ui/"
+ )
+
  @app.get("/dev-ui/config")
  async def get_ui_config():
  return {
@@ -1571,11 +1578,11 @@ async def get_ui_config():
 
  @app.get("/")
  async def redirect_root_to_dev_ui():
- return RedirectResponse("/dev-ui/")
+ return RedirectResponse(redirect_dev_ui_url)
 
  @app.get("/dev-ui")
  async def redirect_dev_ui_add_slash():
- return RedirectResponse("/dev-ui/")
+ return RedirectResponse(redirect_dev_ui_url)
 
  app.mount(
  "/dev-ui/",

src/google/adk/cli/cli_tools_click.py

@@ -1028,6 +1028,17 @@ def decorator(func):
  ),
  multiple=True,
  )
+ @click.option(
+ "--url_prefix",
+ type=str,
+ help=(
+ "Optional. URL path prefix when the application is mounted behind a"
+ " reverse proxy or API gateway (e.g., '/api/v1', '/adk'). This"
+ " ensures generated URLs and redirects work correctly when the app"
+ " is not served at the root path. Must start with '/' if provided."
+ ),
+ default=None,
+ )
  @functools.wraps(func)
  @click.pass_context
  def wrapper(ctx, *args, **kwargs):
@@ -1065,6 +1076,7 @@ def cli_web(
  allow_origins: Optional[list[str]] = None,
  host: str = "127.0.0.1",
  port: int = 8000,
+ url_prefix: Optional[str] = None,
  trace_to_cloud: bool = False,
  otel_to_cloud: bool = False,
  reload: bool = True,
@@ -1128,6 +1140,7 @@ async def _lifespan(app: FastAPI):
  a2a=a2a,
  host=host,
  port=port,
+ url_prefix=url_prefix,
  reload_agents=reload_agents,
  extra_plugins=extra_plugins,
  logo_text=logo_text,
@@ -1164,6 +1177,7 @@ def cli_api_server(
  allow_origins: Optional[list[str]] = None,
  host: str = "127.0.0.1",
  port: int = 8000,
+ url_prefix: Optional[str] = None,
  trace_to_cloud: bool = False,
  otel_to_cloud: bool = False,
  reload: bool = True,
@@ -1203,6 +1217,7 @@ def cli_api_server(
  a2a=a2a,
  host=host,
  port=port,
+ url_prefix=url_prefix,
  reload_agents=reload_agents,
  extra_plugins=extra_plugins,
  ),

src/google/adk/cli/fast_api.py

@@ -64,6 +64,7 @@ def get_fast_api_app(
  a2a: bool = False,
  host: str = "127.0.0.1",
  port: int = 8000,
+ url_prefix: Optional[str] = None,
  trace_to_cloud: bool = False,
  otel_to_cloud: bool = False,
  reload_agents: bool = False,
@@ -144,6 +145,7 @@ def get_fast_api_app(
  extra_plugins=extra_plugins,
  logo_text=logo_text,
  logo_image_url=logo_image_url,
+ url_prefix=url_prefix,
  )
 
  # Callbacks & other optional args for when constructing the FastAPI instance