GitHub Copilot loses six AI models on October 19, 2026, including OpenAI's GPT-5.5 and xAI's Grok 4.5. GitHub set the date in a changelog notice on September 18. Any team that picked one of these models by name, in an editor setting or a script, now needs to point it at a newer one. GitHub suggests GPT-5.6 Sol, GPT-5.6 Luna, Grok 4.6 and Gemini 3.8 Flash.
Which models leave Copilot and what replaces them
Copilot is GitHub's AI coding assistant. It lets users choose which company's model answers them. GitHub's September 18 notice says the six models leave "all GitHub Copilot experiences." That covers Copilot Chat, inline edits, the ask and agent modes, and code completions.
| Retired on October 19 | GitHub's suggested replacement |
|---|---|
| GPT-5.5 | GPT-5.6 Sol |
| GPT-5.4 | GPT-5.6 Sol |
| GPT-5.4 mini | GPT-5.6 Luna |
| GPT-5 mini | GPT-5.6 Luna |
| Grok 4.5 | Grok 4.6 |
| Gemini 3.7 Flash | Gemini 3.8 Flash |
The pattern is simple. Full-size OpenAI models map to GPT-5.6 Sol, and the small "mini" models map to GPT-5.6 Luna. The Grok and Gemini models each move up one point release.
Who gets the new models automatically
Business and Enterprise accounts get the replacements switched on for them, according to GitHub. That happens under "default model enablement," a setting that turns on new models as they arrive. There are two exceptions. An admin may have turned that global default off, or may have disabled one of the new models by hand.
In either case, an admin has to enable the replacements in Copilot's model policies. GitHub asked customers to "update your workflows and integrations to use the supported models before this date." Removing the old models takes no work. The notice says "no action is required" once they are gone.
Plan limits on the replacements
GitHub's notice does not say which paid plans include each new model. Byteiota, a developer news site, says GPT-5.6 Sol needs the Pro+, Max, Business or Enterprise plan. By its account, Sol is not on the base Pro plan. Byteiota lists GPT-5.6 Luna, Grok 4.6 and Gemini 3.8 Flash as available from Pro upward. It suggests GPT-5.6 Terra or Luna for Pro users who relied on GPT-5.5 or GPT-5.4.
Those plan details come from byteiota alone, so check your own model picker before you rely on them.
The second retirement wave in three weeks
This is not the first cut this month. On October 2, GitHub removed four other models, according to its changelog. Gemini 3.5 Flash and Gemini 3.6 Flash went to Gemini 3.8 Flash. Kimi K2.7 Code went to Kimi K3, and Claude Opus 4.7 went to Claude Opus 5.5.
Some models now live in Copilot for only a few months. Byteiota notes that Grok 4.5 arrived on July 28, 2026, which gives it 83 days in the product. Qcode.cc, a site that tracks these notices, re-checked the September 18 post on October 7 and found it unchanged.
What this means for developers
-
Search for pinned names today. Byteiota points to three places: the
github.copilot.chat.modelssetting in VS Code'ssettings.json, JetBrains plugin settings, and CI scripts that pass a model name. Search each one for the six retired model names. - Check the default switch. If your organization turned off default model enablement, nobody gets Sol or Luna until an admin enables them.
- Expect a cost or quality change. Moving a small "mini" model to Luna, or a big model to Sol, can change how answers read and how fast they arrive. Re-run any prompts your team depends on.
- Stop pinning exact versions where you can. Byteiota's advice is to use the plan default or a tier instead of an exact model name. With two retirement batches in three weeks, a pinned name may break again soon.
- Your API keys are a separate question. GitHub's notice covers Copilot only. It does not say these models are leaving OpenAI's, Google's or xAI's own APIs.
This article was first published on Tech AI Wire.
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Sources
- Upcoming deprecation of selected GitHub Copilot models in mid-October - GitHub Changelog
- Selected models in GitHub Copilot deprecated - GitHub Changelog
- GitHub Copilot Drops GPT-5.5 and Grok 4.5 on October 19 - byteiota
- GitHub Copilot retires six models on 2026-10-19: the mapping table, what to change, how to verify - qcode.cc
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