golem-call-another-agent-scala

Agent Building

Calling another agent and awaiting the result in a Scala Golem project. Use when the user asks about agent-to-agent RPC, calling remote agents, or inter-component communication.

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Calling Another Agent (Scala)

Overview

The SDK generates companion objects for agent-to-agent calls. Define a companion extending AgentCompanion on the agent trait to enable ergonomic .get() syntax.

Setup

Define the agent trait. The SDK auto-generates a CounterAgentClient companion object at build time:

import golem.BaseAgent
import golem.runtime.annotations.agentDefinition

import scala.concurrent.Future

@agentDefinition()
trait CounterAgent extends BaseAgent {
  class Id(val name: String)
  def increment(): Future[Int]
  def getCount(): Future[Int]
}

Getting a Client

Use CounterAgentClient.get(...) with the target agent's constructor parameters:

val counter = CounterAgentClient.get("my-counter")

This returns a CounterAgentRemote with per-method wrapper fields. It does not create the agent — the agent is created implicitly on its first invocation. If it already exists, you get a handle to the existing instance.

Awaited Call

Call a method and wait for the result:

val result: Future[Int] = counter.increment()
val count: Future[Int] = counter.getCount()

The call uses async-invoke-and-await under the hood — the calling agent suspends (yields the WASM event loop) until the target agent returns. The returned Future is genuinely async, enabling concurrent RPC calls to multiple agents.

Cancelable Call

Get a (Future[Out], CancellationToken) pair to cancel a pending call:

val (result, token) = counter.increment.cancelable()
// Later: token.cancel() — best-effort cancellation

Other Call Modes

Each method also supports fire-and-forget and scheduling:

counter.increment.trigger()                          // fire-and-forget
counter.increment.scheduleAt(Datetime.afterSeconds(60)) // scheduled
counter.increment.scheduleCancelableAt(Datetime.afterSeconds(60)) // cancelable scheduled

See the golem-fire-and-forget-scala and golem-schedule-future-call-scala skills.

Phantom Agents

To create multiple distinct instances with the same constructor parameters, use phantom agents. See the golem-multi-instance-agent-scala skill.

Cross-Component RPC

When calling agents defined in a different component, the generated client type is available after running golem build — the build step generates bridge SDK code for inter-component dependencies declared in golem.yaml.

Avoiding Deadlocks

Never create RPC cycles where A awaits B and B awaits A — this deadlocks both agents. Use .trigger() (fire-and-forget) to break cycles. See the golem-fire-and-forget-scala skill.