Claude models fail with Not Found when used in Copilot agent / Build tasks

[emimontanari]

Description

Claude models fail with Not Found when used in Copilot agent / Build tasks

Description

When using GitHub Copilot with Claude Opus 4.5 selected as the model, agent-style tasks (such as Build / AGENTS.md workflows) fail consistently with a Not Found: Not Found error.

This occurs even though the same model appears selectable in the Copilot UI and works correctly in interactive Copilot Chat contexts.

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Environment

• GitHub Copilot: Enabled
• Selected model: Claude Opus 4.5
• Context: Agent / Build task (non-interactive execution)
• Example task: Generating or updating AGENTS.md
• Editor: VS Code (Copilot Agents / Build flow)

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Expected Behavior

The selected Claude model should either:

• Execute the agent task successfully, or
• Clearly indicate that Claude models are not supported for agent / build execution

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Actual Behavior

The task fails immediately with the following error:

Plugins

No response

OpenCode version

1.1.40

Steps to reproduce

Steps to Reproduce

1. Open a repository with GitHub Copilot enabled
2. Select Claude Opus 4.5 as the Copilot model
3. Run a Copilot agent-style task (for example, a Build task that generates AGENTS.md)
4. Observe the task execution result

Screenshot and/or share link

Operating System

macOs

Terminal

Warp

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• GitHub Copilot API returns 404 "Not Found" after upgrading to v1.1.40 #11751: GitHub Copilot API returns 404 "Not Found" after upgrading to v1.1.40 - reports the same 404 error with Claude models via Copilot after v1.1.40 upgrade
• Anthropic models fail with 404 on GitHub Enterprise (GHE.com) #11105: Anthropic models fail with 404 on GitHub Enterprise (GHE.com) - related 404 issue with Claude/Anthropic models and Copilot endpoints

Feel free to ignore if none of these address your specific case.

[OpeOginni]

@emimontanari Based on other issues it seems you need to upgrade your Opencode version, as this issue has been fixed.

Run the opencode upgrade command or if you are using brew follow this set in another issue.

brew uninstall opencode
brew install anomalyco/tap/opencode