Class ParallelAgent

java.lang.Object

com.google.adk.workflow.BaseNode

com.google.adk.agents.BaseAgent

com.google.adk.agents.ParallelAgent

All Implemented Interfaces:

Node

public class ParallelAgent
extends BaseAgent

A shell agent that runs its sub-agents in parallel in isolated manner.

This approach is beneficial for scenarios requiring multiple perspectives or attempts on a single task, such as running different algorithms simultaneously or generating multiple responses for review by a subsequent evaluation agent.

Composition with LlmAgents: a ParallelAgent does not transfer control back to a parent LlmAgent. To follow a fan-out with an aggregation step, wrap both in a SequentialAgent (used as the root or transferred-to agent). Each parallel sub-agent publishes via outputKey and the aggregator reads via {key} placeholders in its instruction:

var contacts =
    LlmAgent.builder()
        .name("contacts")
        .model("gemini-flash-latest")
        .instruction("List contacts.")
        .outputKey("contacts")
        .build();
var schedule =
    LlmAgent.builder()
        .name("schedule")
        .model("gemini-flash-latest")
        .instruction("List schedule.")
        .outputKey("schedule")
        .build();
var writer =
    LlmAgent.builder()
        .name("writer")
        .model("gemini-flash-latest")
        .instruction("Write: contacts={contacts}, schedule={schedule}")
        .build();
var gather =
    ParallelAgent.builder().name("gather").subAgents(contacts, schedule).build();
var root = SequentialAgent.builder().name("root").subAgents(gather, writer).build();

Nested Class Summary

Nested Classes

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

Method Summary

Modifier and Type	Method	Description
static ParallelAgent.Builder	builder()
static ParallelAgent	fromConfig(ParallelAgentConfig config, String configAbsPath)	Creates a ParallelAgent from configuration.
protected io.reactivex.rxjava3.core.Flowable<Event>	runAsyncImpl(InvocationContext invocationContext)	Runs sub-agents in parallel and emits their events.
protected io.reactivex.rxjava3.core.Flowable<Event>	runLiveImpl(InvocationContext invocationContext)	Not supported for ParallelAgent.

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 ParallelAgent.Builder builder()

fromConfig

public static ParallelAgent fromConfig(ParallelAgentConfig config,
 String configAbsPath)
                                throws ConfigAgentUtils.ConfigurationException

Creates a ParallelAgent from configuration.

Parameters:

config - the agent configuration

configAbsPath - The absolute path to the agent config file.

Returns:

the configured ParallelAgent

Throws:

ConfigAgentUtils.ConfigurationException - if the configuration is invalid

runAsyncImpl

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

Runs sub-agents in parallel and emits their events.

Sets the branch and merges event streams from all sub-agents.

Specified by:

runAsyncImpl in class BaseAgent

Parameters:

invocationContext - Invocation context.

Returns:

Flowable emitting events from all sub-agents.

runLiveImpl

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

Not supported for ParallelAgent.

Specified by:

runLiveImpl in class BaseAgent

Parameters:

invocationContext - Invocation context.

Returns:

Flowable that always throws UnsupportedOperationException.