// Rubber Duck Thursdays - Let's build with custom agents

Chris explores Copilot custom agents and custom instructions, restructuring project context files and creating meta instruction files for a more effective AI-assisted development workflow.

Topics Covered

• GitHub Changelog Roundup — Enterprise bring-your-own-key for Copilot, linter integration with Copilot code review (ESLint, PMD), GitHub Actions cache size exceeding 10 GB, Claude Opus 4.5 in public preview, and secret scanning updates.
• Custom Instructions Deep Dive — Restructuring copilot-instructions.md to include monorepo tech stack details, build order, service boundaries, security guidelines, and testing conventions using recommended practices from the docs.
• Meta Instruction Files — Creating instruction files that teach Copilot how to write better custom instructions and custom agents, pulling in recommended practices from the GitHub and VS Code documentation.
• Plan Mode for Agent Design — Using Copilot’s plan mode to iterate on ideas before implementation, demonstrating how follow-up questions help refine requirements like rubber duck debugging.
• Context Engineering — Discussion on supplying the right context to Copilot, balancing context window size, and the importance of being requirements-driven for high-quality code generation.
• Community Q&A — Topics including sustainable engineering pace, avoiding burnout, handling merge conflicts, and the fundamentals of software quality.