# Six GitHub Copilot models retire on December 14

GitHub will remove Claude Fable 5, Claude Haiku 4.5, Gemini 3.8 Flash, Gemini 4 Argon, Grok 4.6 and Kimi K3 from Copilot experiences. Five have named replacements, while GitHub has not named a Kimi K3 successor.[1]

GitHub announced on November 13, 2026 that six models will leave Copilot on December 14. The retirement applies across Copilot Chat, inline edits, ask mode, agent mode and code completions.[1]

GitHub recommends Claude Fable 5.1, Claude Haiku 5.5, Gemini 4 Hydrogen, Gemini 4 Carbon and Grok 4.7 for five of the retiring models. Its announcement lists the Kimi K3 replacement as to be announced.[1]

Business and Enterprise administrators who use default model enablement should receive the named alternatives automatically. Administrators who disabled the global default or explicitly blocked a model need to update their model policies.[1]

## What GitHub is retiring

[GitHub published the retirement notice on November 13 [1]](https://github.blog/changelog/2026-11-13-upcoming-deprecation-of-selected-github-copilot-models-in-december). The same December 14 date covers Claude Fable 5, Claude Haiku 4.5, Gemini 3.8 Flash, Gemini 4 Argon, Grok 4.6 and Kimi K3 across Copilot experiences.

GitHub names Claude Fable 5.1 as the alternative to Fable 5, Haiku 5.5 for Haiku 4.5, Gemini 4 Hydrogen for Gemini 3.8 Flash, Gemini 4 Carbon for Gemini 4 Argon and Grok 4.7 for Grok 4.6. The notice does not yet name a replacement for Kimi K3.[1]

One exception applies to Claude Haiku 4.5: GitHub says individual subscribers on annual plans can keep access. The general retirement still applies to the other users and Copilot surfaces named in the announcement.[1]

## Who needs to take action

A developer who always accepts Copilot's current automatic choice may see little setup work, but should still check whether important tasks change after the model pool changes. Anyone who pins a model in chat, agent mode, team instructions or a documented workflow needs a direct replacement test.

Copilot Business and Enterprise administrators should review model policies. GitHub says the suggested alternatives are enabled automatically when the organization keeps default model enablement. An administrator who turned off the global default or explicitly disabled a replacement must enable it before users can select it.[1]

[GitHub's supported-model reference [2]](https://docs.github.com/en/copilot/reference/ai-models/supported-models) shows that availability varies by plan and client. A replacement appearing in GitHub's catalog does not prove that every IDE version, extension or account policy can use it.

## How the suggested replacements differ

The suggested pairs preserve a broad role, rather than identical behavior. Hydrogen is Google's fast model for coding and tool use, while Carbon targets more demanding reasoning. GitHub made Hydrogen generally available in Copilot on November 13 and bills it at provider list pricing under usage-based billing.[3]

A newer family member can change instruction following, tool selection, latency, context use and credit consumption. Existing prompt files and repository instructions may need revision even when the replacement handles the same type of work.

GitHub's supported-model page also records plan, client and minimum-version details where available. Keep the current IDE and Copilot extension in the migration record so a client problem does not look like a model regression.[2]

## A two-week migration test

Use the remaining window to compare accepted work rather than judging one conversational answer. Keep the repository revision, task prompt, instructions, tools and review rubric stable for both models.

- List every retiring model used in team guidance, screenshots, onboarding, policies and saved prompts.
- Choose five to ten recent tasks for each use case, including one failure case and one tool-heavy agent task.
- Run the retiring model and GitHub's suggested alternative with the same repository state and permissions.
- Record passed tests, reviewer corrections, tool failures, elapsed time and premium-request or usage-based cost.
- Check each required IDE and Copilot surface because model support can differ between clients.[2]
- Enable the replacement in a small group, keep a second supported fallback, then update team documentation.
- Move Kimi K3 workflows to a temporary tested model or wait for GitHub's named replacement, but do not invent an alias.[1]

## Limits and open questions

GitHub has not said why it chose one retirement date for these six models. The notice supplies replacements and policy instructions, but it does not claim that each replacement produces equivalent code or costs the same.[1]

The Kimi K3 alternative remains unannounced. Teams using it should monitor the changelog and supported-model page rather than assuming that another Kimi model will appear.[1][2]

GitHub's live model reference can change before December 14. Save the tested model name, client version and policy state with each result, then check the final catalog again before switching defaults.[2]

Model migration does not remove the need for tests and human review. GitHub warns that evaluation models and other models can perform worse on security-related prompts and tells users to validate generated code before production use.[2]

## Frequently asked questions

- When do the six Copilot models retire? GitHub lists December 14, 2026 for all six.[1]
- Does the change affect agent mode? Yes. GitHub names Chat, inline edits, ask mode, agent mode and code completions.[1]
- Will GitHub enable replacements automatically? It says yes for Business and Enterprise customers using default model enablement, unless an administrator disabled the global default or the specific model.[1]
- What replaces Kimi K3? GitHub lists the alternative as to be announced.[1]
- Should a team switch without testing? No. The replacements serve similar roles, but behavior, availability and billing can differ.[2][3]

## Sources

- [[1] GitHub Changelog: Upcoming deprecation of selected Copilot models, November 13, 2026](https://github.blog/changelog/2026-11-13-upcoming-deprecation-of-selected-github-copilot-models-in-december)
- [[2] GitHub Docs: Supported AI models in GitHub Copilot](https://docs.github.com/en/copilot/reference/ai-models/supported-models)
- [[3] GitHub Changelog: Gemini 4 Hydrogen in GitHub Copilot, November 13, 2026](https://github.blog/changelog/2026-11-13-gemini-4-hydrogen-in-github-copilot)