GitHub Copilot CLI: Smarter Delegation, Fewer Failures

GitHub Copilot CLI now features "smarter subagent delegation." This change reduces unnecessary helper-agent handoffs and parallelizes work. It is live on all Copilot CLI production traffic. Users need to update to version 1.0.42 or later. A production A/B test showed this change cut tool failures per session by 23%. This includes a 27% reduction in search tool failures and an 18% reduction in edit tool failures. What's interesting is an experimental feature called "Rubber Duck." This pairs a second model, GPT-5.4, as an independent reviewer for plans made by a Claude-family orchestrator. This pairing closed nearly 75% of the performance gap versus a stronger single model on the SWE-Bench Pro benchmark. The bottom line is these improvements aim to make developer tools more efficient and reliable.