feat: enable LoopAgent configuration

PiperOrigin-RevId: 846216015

Author: google-genai-bot

core/src/main/java/com/google/adk/agents/ConfigAgentUtils.java

@@ -307,6 +307,10 @@ private static Class<? extends BaseAgentConfig> getConfigClassForAgent(
       return ParallelAgentConfig.class;
     }
 
+    if (agentClass == LoopAgent.class) {
+      return LoopAgentConfig.class;
+    }
+
     // TODO: Add more agent class to config class mappings as needed
     // Example:
     // if (agentClass == CustomAgent.class) {

core/src/main/java/com/google/adk/agents/LoopAgent.java

@@ -16,11 +16,14 @@
 
 package com.google.adk.agents;
 
+import com.google.adk.agents.ConfigAgentUtils.ConfigurationException;
 import com.google.adk.events.Event;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import io.reactivex.rxjava3.core.Flowable;
 import java.util.List;
 import java.util.Optional;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * An agent that runs its sub-agents sequentially in a loop.
@@ -29,6 +32,7 @@
  * reached (if specified).
  */
 public class LoopAgent extends BaseAgent {
+  private static final Logger logger = LoggerFactory.getLogger(LoopAgent.class);
 
   private final Optional<Integer> maxIterations;
 
@@ -82,6 +86,35 @@ public static Builder builder() {
     return new Builder();
   }
 
+  /**
+   * Creates a LoopAgent from configuration.
+   *
+   * @param config The agent configuration.
+   * @param configAbsPath The absolute path to the agent config file.
+   * @return the configured LoopAgent
+   * @throws ConfigurationException if the configuration is invalid
+   */
+  public static LoopAgent fromConfig(LoopAgentConfig config, String configAbsPath)
+      throws ConfigurationException {
+    logger.debug("Creating LoopAgent from config: {}", config.name());
+
+    Builder builder = builder();
+    ConfigAgentUtils.resolveAndSetCommonAgentFields(builder, config, configAbsPath);
+
+    if (config.maxIterations() != null) {
+      builder.maxIterations(config.maxIterations());
+    }
+
+    // Build and return the agent
+    LoopAgent agent = builder.build();
+    logger.info(
+        "Successfully created LoopAgent: {} with {} subagents",
+        agent.name(),
+        agent.subAgents() != null ? agent.subAgents().size() : 0);
+
+    return agent;
+  }
+
   @Override
   protected Flowable<Event> runAsyncImpl(InvocationContext invocationContext) {
     List<? extends BaseAgent> subAgents = subAgents();

core/src/main/java/com/google/adk/agents/LoopAgentConfig.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2025 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
+ *
+ *     http://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.agents;
+
+/** Configuration for LoopAgent. */
+public class LoopAgentConfig extends BaseAgentConfig {
+  private Integer maxIterations;
+
+  public LoopAgentConfig() {
+    super("LoopAgent");
+  }
+
+  public Integer maxIterations() {
+    return maxIterations;
+  }
+
+  public void setMaxIterations(Integer maxIterations) {
+    this.maxIterations = maxIterations;
+  }
+}

core/src/main/java/com/google/adk/tools/ExitLoopTool.java

@@ -42,7 +42,8 @@ public final class ExitLoopTool {
       name = "exit_loop",
       description = "Exits the loop.\n\nCall this function only when you are instructed to do so.")
   public static void exitLoop(ToolContext toolContext) {
-    toolContext.setActions(toolContext.actions().toBuilder().escalate(true).build());
+    toolContext.setActions(
+        toolContext.actions().toBuilder().escalate(true).skipSummarization(true).build());
   }
 
   private ExitLoopTool() {}

core/src/test/java/com/google/adk/agents/ConfigAgentUtilsTest.java

@@ -1381,4 +1381,34 @@ public void testCallbackRefAccessors() {
     callbackRef.setName("updated-name");
     assertThat(callbackRef.name()).isEqualTo("updated-name");
   }
+
+  @Test
+  public void fromConfig_validYamlLoopAgent_createsLoopAgent()
+      throws IOException, ConfigurationException {
+    File subAgentFile = tempFolder.newFile("sub_agent.yaml");
+    Files.writeString(
+        subAgentFile.toPath(),
+        """
+        agent_class: LlmAgent
+        name: sub_agent
+        description: A test subagent
+        instruction: You are a helpful subagent
+        """);
+
+    File configFile = tempFolder.newFile("loop_agent.yaml");
+    Files.writeString(
+        configFile.toPath(),
+        """
+        name: testLoopAgent
+        description: A test loop agent
+        agent_class: LoopAgent
+        max_iterations: 5
+        sub_agents:
+          - config_path: sub_agent.yaml
+        """);
+    String configPath = configFile.getAbsolutePath();
+    BaseAgent agent = ConfigAgentUtils.fromConfig(configPath);
+    assertThat(agent).isNotNull();
+    assertThat(agent).isInstanceOf(LoopAgent.class);
+  }
 }