Rubber Duck Thursdays - Building with Agent Mode and MCP
An especially announcement-heavy week focused on new AI model availability across GitHub Copilot and GitHub Models, plus hands-on experiments with those models in agent mode and GitHub Actions workflows.
The extensive changelog review covers GPT-4.1 rolling out to all Copilot plans, Gemini 2.5 Pro entering public preview, O3 and O4 mini availability, Meta Llama 4 Scout and Maverick models in GitHub Models, macOS 15 and Windows 2025 GA for Actions runners, Windows ARM64 hosted runners in preview, expanded vision support beyond GPT-4o to Claude and Gemini models, CodeQL 2.21.0 with TypeScript 5.8 support, Copilot Chat for Eclipse GA, secret scanning pattern expansions, and the new Codespaces agent mode button on pull requests.
Chris shows off the strategy trend radar app built in the previous episode — now deployed to GitHub Pages with save/load functionality, light/dark mode support, and interactive dot placement for strategic planning. He creates a GitHub issue via the MCP server for a theme toggle feature, then attempts to implement it using both a Codespace (via the new agent mode PR button) and local VS Code in parallel, comparing how each approach pulls in issue context.
The stream closes with a practical GitHub Actions demo: a workflow that fetches the GitHub Changelog RSS feed and summarizes it into a themed newsletter using the GitHub Models API with GPT-4.1. Chris iterates on the system prompt live, demonstrating prompt engineering techniques to transform raw changelog entries into a polished, grouped, and linked newsletter format — highlighting the new models:read permission requirement for GitHub Actions.
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