The Agents of Stellaris

[!NOTE] Status: Content ready · Media: Generated cover and original SVG illustration · Last verified: 2026-09-05
Primary capability: Creating specialized custom agents and handoffs

[!TIP] Download this learner kit and use the extraction and setup guide. Keep the original starter untouched.

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flowchart LR
    accTitle: The Agents of Stellaris capability map
    accDescr: Roles should have distinct responsibilities and outputs. Tool discovery and handoff availability require evidence in the chosen host.
    S["Test scout: inspect and test"] --> F["Findings and proposed cases"]
    F --> H{"Human accepts scope?"}
    H -->|No| S
    H -->|Yes| A["Agent: implement reviewed slice"]
    A --> R["Clean review and test evidence"]

Legend. The diamond is a human scope gate, not an automatic grant of implementation authority.

Explanation. Roles should have distinct responsibilities and outputs. Tool discovery and handoff availability require evidence in the chosen host.

Official references

These official sources are the authority for product behavior and availability. Recheck them when using a different surface or after a product update.

• VS Code custom agents
• Custom agents configuration
• Custom agents for Copilot cloud agent

Story

Stellaris is navigated by specialists: one charts danger, one repairs engines, and one verifies the route. None receives every instrument.

The fantasy is a memory aid; the engineering lesson requires observable, reproducible evidence.

Learning objectives

• Define a test-focused agent with no source-edit tool and a bounded test command capability.
• Separate role instructions, available tools and a human-reviewed handoff.
• Verify profile discovery and report remaining failures rather than self-approving an implementation.

Prerequisites

For tools and personal accounts, complete the prerequisites guide. For terminal-only study, follow the extracted-kit CLI route; VS Code-specific evidence remains separate.

Evidence boundary: A command tool can still have side effects. Read-only intent is not a sandbox; review exact test commands and permissions.

Estimated session: 45–75 minutes after prerequisites; actual duration varies. Never use production secrets or customer data.

Concept explanation

A custom agent is a reusable role with focused instructions, selected tools, and optional handoffs. Use the .agent.md format; deprecated custom chat modes are not taught. Apply least authority: a reviewer may need read and test tools but not editing tools. Handoffs should transfer a concrete artifact or decision. Tool names and availability differ by host.

Concrete use case

A test scout can inspect and run a narrow test, then recommend a missing case. A separate implementer owns source edits; the handoff transfers a reviewed plan, not unlimited authority.

Vocabulary checkpoint

• Role: Ask, Plan, Agent, or a custom agent.
• Harness/surface: the runtime or product surface in which a role operates.
• Target: the selected session destination, such as Local, Copilot, or Cloud where exposed.
• Environment: the folder, worktree, local machine, Codespace, or remote environment.
• Instructions: automatically applied durable context.
• Prompt: a manually invoked task template.
• Skill: reusable expertise loaded when relevant.
• Custom agent: a role with instructions, tools, and optional handoffs.
• MCP: Model Context Protocol.
• Evidence: a path, diff, command result, trace, or review decision.

Ask → Plan → Agent workflow

Ask — investigate

1. Identify the real user outcome and current source of truth.
2. Inspect relevant files, instructions, tools, permissions, and existing checks.
3. Cite concrete paths or platform evidence for every important finding.
4. Record uncertainty and do not infer unavailable capabilities.

Gate: No implementation until the current state and evidence are understood.

Plan — design

1. State scope, non-goals, assumptions, risks, and trust boundaries.
2. Select the minimum role, tools, authority, and environment.
3. Define acceptance criteria, verification commands, review, and reset.
4. Mark any Preview or experimental dependency and provide a fallback.

Gate: Another learner should be able to predict completion from the plan.

Agent — execute

1. Make the smallest reversible change or produce the planned artifact.
2. Use short inspect → change → verify loops.
3. Preserve command output, exit status, diffs, traces, or platform records.
4. Stop when acceptance criteria are met; do not perform unrelated cleanup.

Review — challenge

1. Inspect the complete diff or artifact.
2. Compare each result with the plan and acceptance criteria.
3. Run the narrowest relevant existing check, broadening only when justified.
4. Record limitations and unresolved risks.
5. Score the work with rubric.md.

Guided mission

1. Prepare one isolated copy

1. Download and extract the stellaris-agents kit into a new work-drive directory.
2. Read KIT-START.md at its root. Open starter/ as the VS Code workspace when testing discovery, but run the verifier from the kit root.
3. Inspect starter/.github/agents/test-scout.agent.md, verify.js before editing.
4. From the extracted kit root, run node verify.js.
5. Record the documented starter rejection. A missing runtime or unrelated crash is not the expected exercise result.

2. Investigate and plan

Copyable baseline command, from the extracted kit root:

node verify.js

In Ask, request a trace of the inspected files and what the verifier actually observes. Challenge any claim about live execution that is not supported by output.

Use this planning prompt:

Define test-scout metadata and a minimal tool list consistent with the verifier. Keep recommendations test-focused, preserve source-read-only intent and require a reviewed handoff to Agent.
Do not implement yet. Identify affected files, the negative case and a safe reset.

3. Implement the reviewed slice

1. Approve only the named starter artifact and necessary focused tests.
2. Ask Agent to implement one slice; inspect proposed commands before execution.
3. Run node verify.js again from the kit root, or node ../verify.js from starter/.
4. Compare the exact result with the checkpoint below and review the complete diff.
5. Record host discovery or live activity separately when available. Do not enable extra services to manufacture a passing result.

[!IMPORTANT] Checkpoint: The profile has search and a focused command tool, no edit tool, and a concrete handoff prompt. A command tool can still have side effects. Read-only intent is not a sandbox; review exact test commands and permissions.

4. Prove a check can reject a mistake

Temporarily add an edit tool to the copied profile. Verify rejection, then restore the restricted tool list.

Finish with the adventure-specific capability evidence in the rubric, not just the presence of a file.

Intentional failure: The Omnipotent Star-Mage

Perform this only in a disposable environment:

Give the agent every tool and the mission “help with the project.” It may edit while reviewing or expand scope because responsibility and authority are unconstrained.

Recovery

Return to Ask, identify the violated boundary, narrow the plan, remove unnecessary authority or context, and repeat the smallest relevant verification. Document the causal lesson rather than merely stating that the attempt failed.

Independent challenge

Build an investigator, implementer, and reviewer chain with explicit artifacts and no duplicated responsibility.

Constraints:

• Do not copy the guided mission verbatim.
• Do not add tools, permissions, or cloud resources without a stated need.
• Do not claim quality, performance, compatibility, or availability without executed evidence.
• Keep fantasy language subordinate to technical clarity.

Evidence checklist

• Source-grounded Ask findings.
• Approved plan with scope, non-goals, risks, checks, and reset.
• Agent diff or artifact limited to the declared scope.
• Verification output with command, status, or platform record.
• Intentional-failure root cause and recovery.
• Independent challenge result.
• Explicit limitations and feature-status notes.
• Completed rubric.md.

Reset instructions

1. Save your diff, command output and limitations from the disposable kit.
2. Stop only the process or learning session you started. Do not stop other projects.
3. If you initialized Git in the kit, inspect git status --short there and restore only your named exercise files from its local baseline.
4. Otherwise, extract the original ZIP into a new unused directory for another attempt; do not overwrite your current work.
5. Remove only exercise-owned configurations, worktrees or remote resources after reviewing anything worth preserving.

The curriculum source and other projects must remain unchanged. A reset of the copied kit is not a repository-wide hard reset.

Next adventure

The Guardrails of Stonevale