Class LoopAgent

java.lang.Object

com.google.adk.workflow.BaseNode

com.google.adk.agents.BaseAgent

com.google.adk.agents.LoopAgent

All Implemented Interfaces:

Node

public class LoopAgent
extends BaseAgent

An agent that runs its sub-agents sequentially in a loop.

The loop continues until a sub-agent escalates, or until the maximum number of iterations is reached (if specified).

Composition with LlmAgents: a LoopAgent does not transfer control back to a parent LlmAgent. To react to loop results, place the LoopAgent and the follow-up LlmAgent as siblings inside a SequentialAgent. Loop sub-agents publish via outputKey and the follow-up reads via {key} placeholders in its instruction:

var refiner =
    LlmAgent.builder()
        .name("refiner")
        .model("gemini-flash-latest")
        .instruction("Refine: {draft?}")
        .outputKey("draft")
        .build();
var publisher =
    LlmAgent.builder()
        .name("publisher")
        .model("gemini-flash-latest")
        .instruction("Publish: {draft}")
        .build();
var loop =
    LoopAgent.builder().name("loop").subAgents(refiner).maxIterations(3).build();
var root = SequentialAgent.builder().name("root").subAgents(loop, publisher).build();

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LoopAgent.Builder	Builder for LoopAgent.

Method Summary

Modifier and Type	Method	Description
static LoopAgent.Builder	builder()
static LoopAgent	fromConfig(LoopAgentConfig config, String configAbsPath)	Creates a LoopAgent from configuration.
@Nullable Integer	maxIterations()
protected io.reactivex.rxjava3.core.Flowable<Event>	runAsyncImpl(InvocationContext invocationContext)	Agent-specific asynchronous logic.
protected io.reactivex.rxjava3.core.Flowable<Event>	runLiveImpl(InvocationContext invocationContext)	Agent-specific synchronous logic.

Methods inherited from class BaseAgent

afterAgentCallback, beforeAgentCallback, canonicalAfterAgentCallbacks, canonicalBeforeAgentCallbacks, close, findAgent, findSubAgent, fromConfig, parentAgent, parentAgent, rootAgent, runAsync, runLive, runNode, subAgents, toolOrigin

Modifier and Type	Method	Description
com.google.common.collect.ImmutableList<? extends Callbacks.AfterAgentCallback>	afterAgentCallback()
com.google.common.collect.ImmutableList<? extends Callbacks.BeforeAgentCallback>	beforeAgentCallback()
com.google.common.collect.ImmutableList<? extends Callbacks.AfterAgentCallback>	canonicalAfterAgentCallbacks()	The resolved afterAgentCallback field as a list.
com.google.common.collect.ImmutableList<? extends Callbacks.BeforeAgentCallback>	canonicalBeforeAgentCallbacks()	The resolved beforeAgentCallback field as a list.
io.reactivex.rxjava3.core.Completable	close()	Closes all sub-agents.
Optional<BaseAgent>	findAgent(String name)	Finds an agent (this or descendant) by name.
Optional<BaseAgent>	findSubAgent(String name)	Recursively search sub agent by name.
static BaseAgent	fromConfig(BaseAgentConfig config, String configAbsPath)	Creates a new agent instance from a configuration object.
BaseAgent	parentAgent()	Retrieves the parent agent in the agent tree.
protected void	parentAgent(BaseAgent parentAgent)	Sets the parent agent.
BaseAgent	rootAgent()	Returns the root agent for this agent by traversing up the parent chain.
io.reactivex.rxjava3.core.Flowable<Event>	runAsync(InvocationContext parentContext)	Runs the agent asynchronously.
io.reactivex.rxjava3.core.Flowable<Event>	runLive(InvocationContext parentContext)	Runs the agent synchronously.
io.reactivex.rxjava3.core.Flowable<Event>	runNode(Context context, @Nullable Object nodeInput)	Runs this agent as a workflow node through its BaseAgent.runAsync(InvocationContext) lifecycle, including its callbacks.
List<? extends BaseAgent>	subAgents()
AgentEnums.AgentOrigin	toolOrigin()	Returns the origin of the tool when this agent is used as a tool.

Methods inherited from class BaseNode

config, description, inputSchema, name, outputSchema, rerunOnResume, stateSchema, waitForOutput

Modifier and Type	Method	Description
NodeConfig	config()	Returns the node's retry policy and execution timeout.
String	description()	Returns what the node does, for humans and for a model that may call it.
Optional<com.google.genai.types.Schema>	inputSchema()	Returns the schema the node's input must match.
final String	name()	Returns the name that identifies the node within its graph.
Optional<com.google.genai.types.Schema>	outputSchema()	Returns the schema that the node's output value must match.
boolean	rerunOnResume()	Returns true if a resumed node runs again from scratch, rather than completing with the resuming answer as its output.
Optional<com.google.genai.types.Schema>	stateSchema()	Returns the schema declaring the state keys the node uses.
boolean	waitForOutput()	Returns true if the node stays re-triggerable until it produces an output or a route, instead of completing when its run completes.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface Node

requiresAllPredecessors

Modifier and Type	Method	Description
default boolean	requiresAllPredecessors()	Returns true if the node runs only once every predecessor has completed, receiving all their outputs keyed by node name, as a fan-in node does.

Method Details

builder

public static LoopAgent.Builder builder()

fromConfig

public static LoopAgent fromConfig(LoopAgentConfig config,
 String configAbsPath)
                            throws ConfigAgentUtils.ConfigurationException

Creates a LoopAgent from configuration.

Parameters:

config - The agent configuration.

configAbsPath - The absolute path to the agent config file.

Returns:

the configured LoopAgent

Throws:

ConfigAgentUtils.ConfigurationException - if the configuration is invalid

runAsyncImpl

protected io.reactivex.rxjava3.core.Flowable<Event> runAsyncImpl(InvocationContext invocationContext)

Description copied from class: BaseAgent

Agent-specific asynchronous logic.

Specified by:

runAsyncImpl in class BaseAgent

Parameters:

invocationContext - Current invocation context.

Returns:

stream of agent-generated events.

runLiveImpl

protected io.reactivex.rxjava3.core.Flowable<Event> runLiveImpl(InvocationContext invocationContext)

Description copied from class: BaseAgent

Agent-specific synchronous logic.

Specified by:

runLiveImpl in class BaseAgent

Parameters:

invocationContext - Current invocation context.

Returns:

stream of agent-generated events.

maxIterations

public @Nullable Integer maxIterations()