Agents

Jupiter agents are Markdown files with YAML frontmatter. This is similar to other coding agents such as Claude or Codex.

Primary Agents

Jupiter ships with two primary agents:

• Plan - focused on planning and exploration.
• Engineer - the coding agent.

Their current model preferences live in the bundled agent definitions and may change independently of this documentation. See Models and Providers for model selection and fallback behaviour.

There are also Explore, Apprentice, and Test subagents. See Subagents.

Agent File Format

An agent definition can contain:

• id and name
• description
• mode: agent or subagent
• default model (a single model ID or a comma-separated, ordered preference list)
• reasoningEffort
• optional textVerbosity
• tool permissions
• a Markdown prompt body

Tool Permissions

The tool map decides what an agent can call directly. * expands to native tools plus mcp:*; primary agents also get the task tool.

One subtle point: Plan has no direct write or command tools, but it can delegate to configured subagents. Its “planning only” behaviour is therefore partly prompt-directed, not a transitive read-only sandbox.

Subagents never receive task, so native delegation cannot recurse forever.

The composer lets you pick the agent, model, and thinking level for a turn. Without an explicit model or thinking override, the selected agent's configured defaults apply.