GitHub: Copilot Retires Opus 4.6 (fast) on June 29, Adds AGENTS.md to Code Review and ai_credits_used Field to API

GitHub announced three changes for Copilot, its AI programming tool, through its changelog. The changelog is a chronological record of minor product changes, separate from major blog posts, gathering practical updates for the day-to-day work of development teams.

Retiring the Opus 4.6 (fast) Model

The most important change for users is that the Opus 4.6 (fast) model is being retired on June 29, 2026 across all Copilot surfaces, with a recommendation to switch to Opus 4.8 (fast). The retirement affects chat, inline edits and code completion, so teams that have pinned the old model need to migrate before the deadline to avoid disruption.

AGENTS.md and Credit Measurement

Copilot code review now reads repository AGENTS.md files and adapts feedback to project conventions, reducing noise from irrelevant comments. Additionally, the Copilot Usage Metrics API gains a new ai_credits_used field that tracks total AI credit consumption per user in daily and 28-day reports. Unlike a billing statement, the field is a signal for consumption analysis and currently has no breakdown by feature, model or surface.