Multiple containers

The agent works in a service called main. Other containers provide the services it needs. All belong to one trial.

Add a small HTTP service

This environment gives the agent a JSON file through an HTTP service. Add it to a task with an instruction and verifier.

my-task

instruction.md

task.toml

environment

Dockerfile

docker-compose.yaml

api

Dockerfile

status.json

tests

test.sh

Set the task’s network policy to public; Compose does not support no-network. Update the existing [environment] table if present:

task.toml

[environment]
network_mode = "public"

FROM python:3.12-slim
WORKDIR /app

FROM python:3.12-slim
WORKDIR /srv
COPY status.json .
CMD ["python3", "-m", "http.server", "8000", "--bind", "0.0.0.0"]

{
  "status": "ready",
  "items": 3
}

Name the Compose file exactly environment/docker-compose.yaml:

environment/docker-compose.yaml

services:
  main:
    depends_on:
      api:
        condition: service_healthy
  api:
    build:
      context: ./api
    healthcheck:
      test:
        - CMD
        - python3
        - -c
        - >-
          import urllib.request;
          urllib.request.urlopen(
            'http://localhost:8000/status.json'
          )
      interval: 2s
      timeout: 5s
      retries: 15

Evolve builds main from environment/Dockerfile and api from its own Dockerfile. depends_on waits for the API healthcheck. From main, the agent can read http://api:8000/status.json using the service name as the hostname. The main stanza above only adds a dependency. You can omit it when you have no overrides. To use a prebuilt main image, set [environment].docker_image in task.toml.

Images, files, and configuration

Choice	Rule
Service `image`	Use a public image with an explicit tag or digest
Service `build`	Keep the context inside the task directory and the Dockerfile inside that context
Build options	`context`, `dockerfile`, `args`, `target`, `no_cache`, `pull`, and `labels`
Service dependencies	Use Compose `depends_on` and healthchecks
Container files	Include bind-mounted source files inside the task’s `environment/` directory
Runtime configuration	Compose ports, volumes, networks, `environment`, and `env_file` are handled by Compose
Compose variables	See the interpolation rules below.

Images are resolved during dataset import. Runtime tasks use the recorded images. Task files and image-build inputs are not a secret store; use job secrets for agent credentials.

Compose variable interpolation

At runtime, Evolve supplies Harbor’s Compose variables over your [environment.env] literals:

${CONTEXT_DIR}, ${MAIN_IMAGE_NAME}, and ${PREBUILT_IMAGE_NAME}
${CPUS} and ${MEMORY}
HOST_ and ENV_ paths for AGENT_LOGS, VERIFIER_LOGS, and ARTIFACTS

Publication resolves variables only in build contexts, main.image, and main.working_dir. Here ${CONTEXT_DIR} is the task’s environment/ directory. Other values come from [environment.env] literals, then :- or - defaults.

Configuration that import rejects

include and service extends, which can introduce unseen service images.
Interpolated sidecar image names, untagged images, and an unpinned :latest tag. On main, ${MAIN_IMAGE_NAME} and ${PREBUILT_IMAGE_NAME} name main’s own image, and other variables are accepted when they resolve at import.
A variable with no value and no default in a build context or in main’s working_dir, and a working_dir that is not an absolute path.
Build options such as ssh, secrets, additional contexts, and inline Dockerfiles.
A build context outside the task, or a Dockerfile outside its build context.
main.build together with [environment].docker_image, or conflicting main image declarations.

Provider and task limits

Compose tasks run on E2B or Daytona. They do not support Modal, no-network, GPUs, or multi-step execution. Sandbox capabilities describes provider selection and other network restrictions.

Score service state

A verifier may need more than files from main: a request log, a database export, or an in-memory counter. Use collection hooks and service artifacts to save that evidence before verification.

Start here

Run evaluations

Task format

Validate your work

Read results

Work together

Multiple containers

Add a small HTTP service

Images, files, and configuration

Provider and task limits

Score service state