GitHub Copilot Review (September 2026): GPT-6 Astra, Four Models Retiring, and the Usage Billing Math
GitHub Copilot shipped GPT-6 Astra, Claude Fable 5.1, and Gemini 3.8 Flash in one week, is retiring four models on October 2, and code review can now approve PRs. Here is what changed, which model to default, and whether the 4.5 rating holds.
- ✓GPT-6 Astra is GA on Pro+, Max, Business, and Enterprise, built for long-horizon autonomous coding that plans and validates as it goes before it declares a task done (per GitHub changelog, Sept 4 2026)
- ✓The picker gained three GA models in one week: GPT-6 Astra, Claude Fable 5.1, and Gemini 3.8 Flash, the last of which reaches Pro seats too (per GitHub changelog, Sept 1 to 4 2026)
- ✕GPT-6 Astra and Claude Fable 5.1 both bill at provider list pricing under usage-based billing, so on flat-rate Business the frontier models draw down the pooled credit allowance rather than riding for free on the seat (per GitHub changelog, Sept 1 and 4 2026)
- ✕Four models retire October 2 (Gemini 3.5 Flash, Gemini 3.6 Flash, Kimi K2.7 Code, Claude Opus 4.7), so any team with pinned workflows has a migration to run first (per GitHub changelog, Sept 3 2026)
For a solo developer, Pro+ at $39 is still the working tier, and GPT-6 Astra plus Claude Fable 5.1 are the reason to be on it, but watch the credit meter because both bill usage-based and long agent runs draw it down fast; if your day is all-day whole-repo editing, Cursor's Composer still edits cleaner. For a small team on Business at $19/user, the pick holds with one caveat: budget GPT-6 Astra as paid usage on top of the pooled allowance instead of assuming the seat covers it, and run the October 2 model migration before it bites. For an enterprise on Enterprise at $39/user, the any-model default, content exclusions in the app and CLI, and the new PR-approval control make it the standardize-here buy, provided admins enable the Fable 5.1 retention policy deliberately and set the PR-approval scope by file path.