golemcloud/golem/golem-add-config-scala

Adding Typed Configuration to a Scala Agent

Overview

Scala agents receive typed configuration via Config[T] from golem.config. The agent trait declares its config type by mixing in the AgentConfig[T] trait. The implementation class receives a Config[T] constructor parameter and accesses the resolved value lazily via .value.

Steps

1. Define config case classes with Schema.derived in companion objects
2. Mix in `AgentConfig[T]` on the agent trait
3. Accept `Config[T]` in the implementation constructor
4. Access config via config.value

Config Types

Define case classes for your configuration. Each needs an implicit val schema in its companion object:

import zio.blocks.schema.Schema
 
final case class DbConfig(
  host: String,
  port: Int,
)
 
object DbConfig {
  implicit val schema: Schema[DbConfig] = Schema.derived
}
 
final case class MyAppConfig(
  appName: String,
  db: DbConfig,
)
 
object MyAppConfig {
  implicit val schema: Schema[MyAppConfig] = Schema.derived
}

Agent Definition

Mix in AgentConfig[T] alongside BaseAgent:

import golem.BaseAgent
import golem.config.AgentConfig
import golem.runtime.annotations.{agentDefinition, description}
 
@agentDefinition()
trait MyAgent extends BaseAgent with AgentConfig[MyAppConfig] {
  class Id(val value: String)
 
  def greet(): Future[String]
}

Agent Implementation

Accept Config[T] as a constructor parameter and access the value lazily:

import golem.config.Config
import golem.runtime.annotations.agentImplementation
 
@agentImplementation()
final class MyAgentImpl(input: String, config: Config[MyAppConfig]) extends MyAgent {
  override def greet(): Future[String] = {
    val cfg = config.value
    Future.successful(s"Hello from ${cfg.appName}! DB at ${cfg.db.host}:${cfg.db.port}")
  }
}

Providing Config Values

golem.yaml — set defaults for agents:

agents:
  MyAgent:
    config:
      appName: "My Application"
      db:
        host: "localhost"
        port: 5432

CLI — override at agent creation:

golem agent new 'MyAgent("agent-1")' \
  --config appName="My App" \
  --config db.host=localhost \
  --config db.port=5432

RPC — override via the generated helper:

val client = MyAgentClient.getWithConfig(
  "agent-1",
  appName = Some("OverriddenApp"),
  dbHost = Some("new-host"),
  dbPort = Some(9999)
)

Key Constraints

• Config case classes need a companion object with implicit val schema: Schema[T] = Schema.derived
• The agent trait mixes in AgentConfig[T] to declare its config type
• The implementation class receives Config[T] as a constructor parameter
• Config is loaded lazily when .value is accessed
• Config values in golem.yaml use camelCase keys matching Scala field names
• Config cascade order: componentTemplates → components → agents, with presets resolved

within each template, component, and agent layer, not as one final global layer

• If the config includes Secret[T] fields, also use golem-add-secret-scala for secret-specific declaration and CLI guidance