Copilot CLI Weekly: BYOK, Rubber Duck, and Direct Mode Flags

The CLI Goes Fully Open: BYOK and Local Models GitHub dropped a changelog entry on April 7 that fundamentally changes what Copilot CLI is: you can now bring your own model provider or run fully local models. No GitHub-hosted routing required. This is BYOK (bring your own key) for the terminal agent, and it's a big deal. Here's what it means in practice: you configure environment variables pointing to Azure OpenAI, Anthropic, OpenAI, or any OpenAI-compatible endpoint, and Copilot CLI routes all inference through your provider instead of GitHub's model gateway.