For AI agents: The documentation index is at https://docs.digitalocean.com/llms.txt. Markdown versions of pages use the same URL with index.html.md in place of the HTML page (for example, append index.html.md to the directory path instead of opening the HTML document).

Harness Runtime supports multiple coding agent adapters. Each adapter runs in its own sandbox. Pick an adapter, set credentials under secrets, and start a session from the spec. To run a framework agent instead of a coding agent, see Run a LangGraph Agent or Run a CrewAI Agent.

Create a Spec File for a Coding Adapter

A spec file is a YAML file that describes the environment you want. You can choose from one of the following coding adapters in your spec:

name: codex-agent
agent: codex
size: mars-2vcpu-4gb
secrets:
  OPENAI_API_KEY: ${OPENAI_API_KEY}
permissions:
  default: ask

export OPENAI_API_KEY=<your-openai-key>

name: claude-code-agent
agent: claude-code
size: mars-2vcpu-4gb
secrets:
  ANTHROPIC_API_KEY: ${ANTHROPIC_API_KEY}
permissions:
  default: ask

export ANTHROPIC_API_KEY=<your-anthropic-key>

name: opencode-agent
agent: opencode
size: mars-2vcpu-4gb
secrets:
  OPENAI_API_KEY: ${OPENAI_API_KEY}
permissions:
  default: ask

export OPENAI_API_KEY=<your-openai-key>

To pin a model, or to use DigitalOcean Inference instead of an external provider key, put the model access key under secrets and the non-secret endpoint settings in env:

env:
  HARNESS_INFERENCE_MODEL: deepseek-v4-pro
secrets:
  HARNESS_INFERENCE_API_KEY: ${HARNESS_INFERENCE_API_KEY}

For more information about the environment spec, see the environment spec reference.

Start and Attach to the Session

Pass the spec file to launch, which creates the sandbox, starts the agent inside it, and attaches your terminal, all in one step:

doctl harness-runtime launch <your-spec-file>.yaml

Press Ctrl+D to detach. The session keeps running in the cloud, and the same launch command reconnects you to it. Passing the name of a session that already exists resumes it rather than creating a new one:

doctl harness-runtime launch <your-session-name>

If you start the same setup repeatedly, save the spec as an Environment Config and start sessions from it instead of uploading the YAML each time. See Use Environment Configs.

Create an Environment in the Control Panel

Instead of writing a spec file, you can also create an environment in the DigitalOcean Control Panel. On the Create Environment page, you configure the harness, model, sandbox, tools, skills, and tool permissions in one form.

1. In the Control Panel, under Managed Agents, click Harness Runtime, and then click Create Environment.

2. On Create Environment, under Select a Harness, choose a coding harness (OpenCode, Codex CLI, Claude Code, or Hermes) or a framework harness (LangGraph). If Build your own and Pre-built templates tabs appear, select Build your own to configure a harness from scratch. If you choose a framework harness, under Framework repository, provide the repository the platform clones at boot.

3. Under Model, choose Serverless Inference or Custom. For Serverless Inference, select the model and provide a model access key when prompted. For Custom, enter the API base URL, API key, and model name.

4. Under Configure, choose a size under Select a Sandbox Size. See Sandbox Sizes for available slugs and resources. Set Outbound Network Access to Unrestricted or Restricted, and optionally add environment variables or secrets.

5. Under Tools, click Add tools and choose the Action Gateway tools the agent can use. To let the agent run git commands in the sandbox, optionally connect GitHub under CLI Authentication: under Use an existing connection, select one of your GitHub connections, or click Connect a different GitHub account, enter an Actor ID, and click Connect account to authorize one without leaving the page. The list shows only connections you created. You can also click Revoke to revoke a connection here, which succeeds only if no Environment Config still uses it. Under Tool permissions, set the Default permission, and click Add rule to allow, ask for approval, or deny specific tools. To authorize Action Gateway providers for those tools, see Authorize Providers with Connections.

6. Under Skills, click Add Skill, then choose Upload skill or Create skill:

   • Upload skill: Select a SKILL.md Markdown file. The file must include YAML front matter with name and description. Review or edit the parsed skill in Review Skill, then save it.
   • Create skill: Enter the skill name, description, and instructions in Create New Skill.

   An environment accepts up to 32 skills. For every field a skill accepts, see skills in the Environment Spec Reference.

7. Enter a Name for the environment, then click Create Environment.

The environment appears in the Environments tab. Start a session from it by clicking Create Session, or from the command line as described in Use Environment Configs. You can then start sending requests to your agent.

Troubleshooting

Use this table to diagnose common errors when creating or attaching to a session: