fix: serve runtime-config.json dynamically instead of writing to package directory

src/google/adk/cli/adk_web_server.py

@@ -601,30 +601,11 @@ def _import_plugin_object(self, qualified_name: str) -> Any:
     module = importlib.import_module(module_name)
     return getattr(module, obj_name)
 
-  def _setup_runtime_config(self, web_assets_dir: str):
-    """Sets up the runtime config for the web server."""
-    # Read existing runtime config file.
-    runtime_config_path = os.path.join(
-        web_assets_dir, "assets", "config", "runtime-config.json"
-    )
-    runtime_config = {}
-    try:
-      with open(runtime_config_path, "r") as f:
-        runtime_config = json.load(f)
-    except FileNotFoundError:
-      logger.info(
-          "File not found: %s. A new runtime config file will be created.",
-          runtime_config_path,
-      )
-    except json.JSONDecodeError:
-      logger.warning(
-          "Failed to decode JSON from %s. The file content will be"
-          " overwritten.",
-          runtime_config_path,
-      )
-    runtime_config["backendUrl"] = self.url_prefix if self.url_prefix else ""
-
-    # Set custom logo config.
+  def _build_runtime_config(self) -> dict[str, Any]:
+    """Builds the runtime config dict for the dev UI frontend."""
+    runtime_config: dict[str, Any] = {
+        "backendUrl": self.url_prefix if self.url_prefix else "",
+    }
     if self.logo_text or self.logo_image_url:
       if not self.logo_text or not self.logo_image_url:
         raise ValueError(
@@ -635,18 +616,7 @@ def _setup_runtime_config(self, web_assets_dir: str):
           "text": self.logo_text,
           "imageUrl": self.logo_image_url,
       }
-    elif "logo" in runtime_config:
-      del runtime_config["logo"]
-
-    # Write the runtime config file.
-    try:
-      os.makedirs(os.path.dirname(runtime_config_path), exist_ok=True)
-      with open(runtime_config_path, "w") as f:
-        json.dump(runtime_config, f, indent=2)
-    except IOError as e:
-      logger.error(
-          "Failed to write runtime config file %s: %s", runtime_config_path, e
-      )
+    return runtime_config
 
   async def _create_session(
       self,
@@ -742,7 +712,7 @@ async def internal_lifespan(app: FastAPI):
         ],
     )
     if web_assets_dir:
-      self._setup_runtime_config(web_assets_dir)
+      self._build_runtime_config()
 
     # TODO - register_processors to be removed once --otel_to_cloud is no
     # longer experimental.
@@ -1816,6 +1786,10 @@ async def get_ui_config():
             "logo_image_url": self.logo_image_url,
         }
 
+      @app.get("/dev-ui/assets/config/runtime-config.json")
+      async def get_runtime_config():
+        return self._build_runtime_config()
+
       @app.get("/")
       async def redirect_root_to_dev_ui():
         return RedirectResponse(redirect_dev_ui_url)

tests/unittests/cli/test_adk_web_server_run_live.py

@@ -203,3 +203,70 @@ async def _get_runner_async(_self, _app_name: str):
         run_config.session_resumption.transparent
         is expected_session_resumption_transparent
     )
+
+
+def _make_server(**kwargs) -> AdkWebServer:
+  defaults = dict(
+      agent_loader=_DummyAgentLoader(),
+      session_service=InMemorySessionService(),
+      memory_service=types.SimpleNamespace(),
+      artifact_service=types.SimpleNamespace(),
+      credential_service=types.SimpleNamespace(),
+      eval_sets_manager=types.SimpleNamespace(),
+      eval_set_results_manager=types.SimpleNamespace(),
+      agents_dir=".",
+  )
+  defaults.update(kwargs)
+  return AdkWebServer(**defaults)
+
+
+class TestBuildRuntimeConfig:
+
+  def test_default_no_prefix(self):
+    server = _make_server()
+    config = server._build_runtime_config()
+    assert config == {"backendUrl": ""}
+
+  def test_with_url_prefix(self):
+    server = _make_server(url_prefix="/my-prefix")
+    config = server._build_runtime_config()
+    assert config == {"backendUrl": "/my-prefix"}
+
+  def test_with_logo(self):
+    server = _make_server(
+        logo_text="My App",
+        logo_image_url="https://example.com/logo.png",
+    )
+    config = server._build_runtime_config()
+    assert config == {
+        "backendUrl": "",
+        "logo": {
+            "text": "My App",
+            "imageUrl": "https://example.com/logo.png",
+        },
+    }
+
+  def test_logo_text_only_raises(self):
+    server = _make_server(logo_text="My App")
+    with pytest.raises(ValueError, match="Both --logo-text and --logo-image-url"):
+      server._build_runtime_config()
+
+  def test_logo_image_url_only_raises(self):
+    server = _make_server(logo_image_url="https://example.com/logo.png")
+    with pytest.raises(ValueError, match="Both --logo-text and --logo-image-url"):
+      server._build_runtime_config()
+
+
+class TestRuntimeConfigEndpoint:
+
+  def test_get_runtime_config_json(self, tmp_path):
+    server = _make_server(url_prefix="/test-prefix")
+    app = server.get_fast_api_app(
+        setup_observer=lambda _observer, _server: None,
+        tear_down_observer=lambda _observer, _server: None,
+        web_assets_dir=str(tmp_path),
+    )
+    client = TestClient(app)
+    resp = client.get("/dev-ui/assets/config/runtime-config.json")
+    assert resp.status_code == 200
+    assert resp.json() == {"backendUrl": "/test-prefix"}