Arin's Tech Musings

GitHub Copilot's customization system separates into four distinct layers: custom agents, instructions, skills, and MCP servers. Each handles a different concern, and they compose together while remaining independently upgradeable. The key insight: separating "who" (agent workflow), "rules" (project standards), and "how" (capabilities) means you can change one without touching the others. Update standards without rewriting agents. Upgrade skills without modifying instructions. Change agent behavior while keeping conventions intact. Everything lives in git. Changes go through pull requests. You can review, approve, and roll back AI behavior like infrastructure. > **Honest disclaimer:** The thoughts here are mine — the prose, structure, and general readability are courtesy of AI. I handed it a brain-dump and it handed back something you'd actually want to read. ```mermaid graph TB subgraph "GitHub Copilot Architecture" ...

GitHub Copilot custom agents make it possible to move beyond a single “do everything” assistant. Instead, you can design workflows where multiple agents collaborate, each focused on a specific responsibility. In this post, I’ll walk through three orchestration modes you can use today when building custom agents in VS Code: VS Code agent handoffs Explicit subagent delegation Automatic subagent delegation Each mode serves a different purpose. Understanding the trade‑offs helps you decide when you want user control, when you want structure, and when you want the agent to adapt on its own. 1. VS Code Agent Handoffs ```mermaid sequenceDiagram participant User participant MainAgent participant SecurityAgent User->>MainAgent: scan my code for security issues MainAgent->>SecurityAgent: handoff (code review) SecurityAgent-->>MainAgent: report findi...