feat: allow disabling the ADK Development UI with adk.web.ui.enabled

webserver/src/jvmMain/kotlin/com/google/adk/kt/webserver/AdkWebServer.kt

@@ -30,6 +30,7 @@ import com.google.adk.kt.webserver.loaders.AgentLoader
 import com.google.adk.kt.webserver.models.VersionInfo
 import com.google.adk.kt.webserver.routes.appRoutes
 import com.google.adk.kt.webserver.routes.artifactRoutes
+import com.google.adk.kt.webserver.routes.isWebUiEnabled
 import com.google.adk.kt.webserver.routes.runRoutes
 import com.google.adk.kt.webserver.routes.sessionRoutes
 import com.google.adk.kt.webserver.routes.staticRoutes
@@ -123,6 +124,13 @@ class AdkWebServer(
   }
 }
 
+/**
+ * Installs the ADK routes, including the Development UI.
+ *
+ * Set the `adk.web.ui.enabled` system property to `false` to leave the Development UI unmounted, or
+ * set it in this application's Ktor config; only `true` and `false` count, and any other value is
+ * ignored with a warning so the next source decides.
+ */
 @OptIn(FrameworkInternalApi::class)
 fun Application.adkModule(
   sessionService: SessionService,
@@ -183,6 +191,8 @@ fun Application.adkModule(
     graphRoutes(agentLoader, sessionService)
     runRoutes(agentLoader, sessionService, artifactService, plugins)
     sessionRoutes(sessionService)
-    staticRoutes(this@adkModule)
+    if (this@adkModule.isWebUiEnabled(default = true)) {
+      staticRoutes(this@adkModule)
+    }
   }
 }

webserver/src/jvmMain/kotlin/com/google/adk/kt/webserver/routes/StaticRoutes.kt

@@ -32,6 +32,39 @@ import org.slf4j.LoggerFactory
 
 private val logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass())
 
+/** Property that decides whether the Development UI is served at all. */
+internal const val WEB_UI_ENABLED_PROPERTY = "adk.web.ui.enabled"
+
+/**
+ * Whether to mount the Development UI, from the `adk.web.ui.enabled` system property, else the
+ * application config, else [default]. A value that is not a boolean counts as unset, so a mistyped
+ * system property cannot mask a setting in the config. Only a host-supplied Ktor config is read;
+ * `embeddedServer` supplies none.
+ */
+internal fun Application.isWebUiEnabled(default: Boolean): Boolean =
+  webUiSettingOrNull(System.getProperty(WEB_UI_ENABLED_PROPERTY), "system property")
+    ?: webUiSettingOrNull(
+      environment.config.propertyOrNull(WEB_UI_ENABLED_PROPERTY)?.getString(),
+      "application config",
+    )
+    ?: default
+
+/** Parses one configured value; null when absent or not a boolean, warning in the latter case. */
+private fun webUiSettingOrNull(raw: String?, source: String): Boolean? {
+  if (raw == null) return null
+  val value = raw.trim()
+  return value.lowercase().toBooleanStrictOrNull().also {
+    if (it == null) {
+      logger.warn(
+        "Ignoring a non-boolean {} from the {}: \"{}\"",
+        WEB_UI_ENABLED_PROPERTY,
+        source,
+        value,
+      )
+    }
+  }
+}
+
 fun Route.staticRoutes(application: Application) {
   var webUiDir =
     System.getProperty("adk.web.ui.dir")

webserver/src/jvmTest/kotlin/com/google/adk/kt/webserver/WebUiToggleTest.kt

@@ -0,0 +1,205 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.adk.kt.webserver
+
+import com.google.adk.kt.webserver.routes.WEB_UI_ENABLED_PROPERTY
+import com.google.adk.kt.webserver.routes.isWebUiEnabled
+import com.google.adk.kt.webserver.telemetry.ApiServerSpanExporter
+import com.google.common.truth.Truth.assertThat
+import io.ktor.client.request.get
+import io.ktor.http.HttpStatusCode
+import io.ktor.server.config.MapApplicationConfig
+import io.ktor.server.testing.ApplicationTestBuilder
+import io.ktor.server.testing.testApplication
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+/**
+ * The `adk.web.ui.enabled` property decides whether the Development UI routes are mounted.
+ *
+ * `/` is the discriminator: `staticRoutes` registers its redirect only when the UI is mounted.
+ */
+@RunWith(JUnit4::class)
+class WebUiToggleTest {
+  private val sessionService = FakeSessionService()
+  private val artifactService = FakeArtifactService()
+  private val agentLoader = FakeAgentLoader()
+
+  @Test
+  fun webUi_unset_isMounted() =
+    withWebUiProperty(null) {
+      testApplication {
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.Found)
+      }
+    }
+
+  @Test
+  fun webUi_disabled_isNotMounted() =
+    withWebUiProperty("false") {
+      testApplication {
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.NotFound)
+        assertThat(client.get(DEV_UI_INDEX).status).isEqualTo(HttpStatusCode.NotFound)
+        // The contract endpoints are untouched by the toggle.
+        assertThat(client.get("/health").status).isEqualTo(HttpStatusCode.OK)
+      }
+    }
+
+  @Test
+  fun webUi_paddedValue_isTrimmedAndHonoured() =
+    withWebUiProperty(" false ") {
+      testApplication {
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.NotFound)
+      }
+    }
+
+  @Test
+  fun webUi_disabledInMixedCase_isNotMounted() =
+    withWebUiProperty("False") {
+      testApplication {
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.NotFound)
+      }
+    }
+
+  @Test
+  fun webUi_nonBooleanValue_fallsBackToDefault() =
+    withWebUiProperty("perhaps") {
+      testApplication {
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.Found)
+      }
+    }
+
+  @Test
+  fun webUi_disabledInConfig_isNotMounted() =
+    withWebUiProperty(null) {
+      testApplication {
+        environment { config = MapApplicationConfig(WEB_UI_ENABLED_PROPERTY to "false") }
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.NotFound)
+      }
+    }
+
+  @Test
+  fun webUi_nonBooleanConfigValue_fallsBackToDefault() =
+    withWebUiProperty(null) {
+      testApplication {
+        environment { config = MapApplicationConfig(WEB_UI_ENABLED_PROPERTY to "perhaps") }
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.Found)
+      }
+    }
+
+  @Test
+  fun webUi_enabledInConfig_overridesCallerDefault() =
+    withWebUiProperty(null) {
+      testApplication {
+        environment { config = MapApplicationConfig(WEB_UI_ENABLED_PROPERTY to "true") }
+        application { assertThat(isWebUiEnabled(default = false)).isTrue() }
+
+        client.get("/")
+      }
+    }
+
+  @Test
+  fun webUi_blankProperty_fallsThroughToConfig() =
+    withWebUiProperty(" ") {
+      testApplication {
+        environment { config = MapApplicationConfig(WEB_UI_ENABLED_PROPERTY to "false") }
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.NotFound)
+      }
+    }
+
+  @Test
+  fun webUi_nonBooleanProperty_fallsThroughToConfig() =
+    withWebUiProperty("no") {
+      testApplication {
+        environment { config = MapApplicationConfig(WEB_UI_ENABLED_PROPERTY to "false") }
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.NotFound)
+      }
+    }
+
+  @Test
+  fun webUi_property_winsOverConfig() =
+    withWebUiProperty("true") {
+      testApplication {
+        environment { config = MapApplicationConfig(WEB_UI_ENABLED_PROPERTY to "false") }
+        installAdk()
+
+        assertThat(rootStatus()).isEqualTo(HttpStatusCode.Found)
+      }
+    }
+
+  @Test
+  fun webUi_unsetEverywhere_usesCallerDefault() =
+    withWebUiProperty(null) {
+      testApplication {
+        application {
+          assertThat(isWebUiEnabled(default = false)).isFalse()
+          assertThat(isWebUiEnabled(default = true)).isTrue()
+        }
+        // Start the app here so a failed assertion is reported at this line, not at teardown.
+        client.get("/")
+      }
+    }
+
+  private fun ApplicationTestBuilder.installAdk() {
+    application { adkModule(sessionService, artifactService, agentLoader, ApiServerSpanExporter()) }
+  }
+
+  /** Status of `/` without following the redirect, so the redirect itself is what is asserted. */
+  private suspend fun ApplicationTestBuilder.rootStatus(): HttpStatusCode =
+    createClient { followRedirects = false }.get("/").status
+
+  /** Runs [body] with `adk.web.ui.enabled` set to [value], or unset when it is null. */
+  private fun withWebUiProperty(value: String?, body: () -> Unit) {
+    val previous: String? = System.getProperty(WEB_UI_ENABLED_PROPERTY)
+    if (value == null) {
+      System.clearProperty(WEB_UI_ENABLED_PROPERTY)
+    } else {
+      System.setProperty(WEB_UI_ENABLED_PROPERTY, value)
+    }
+    try {
+      body()
+    } finally {
+      if (previous == null) {
+        System.clearProperty(WEB_UI_ENABLED_PROPERTY)
+      } else {
+        System.setProperty(WEB_UI_ENABLED_PROPERTY, previous)
+      }
+    }
+  }
+
+  private companion object {
+    const val DEV_UI_INDEX = "/dev-ui/index.html"
+  }
+}