[FEATURE]: Support for Claude Opus 4.6 Fast Mode

Feature hasn't been suggested before.

I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

First, thank you for maintaining this project. I really appreciate all your work.

I wanted to bring to your attention that both Anthropic and GitHub Copilot have recently announced experimental support for Fast Mode with the Claude Opus 4.6 model. I would love to see this capability available in OpenCode, but it doesn’t appear that such a feature or commit exists yet, and I haven’t seen any related issue requests.

It would be fantastic if this functionality could be supported.

Thank you!

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

[FEATURE]: Add support of Claude Opus 4.6 #12323: [FEATURE]: Add support of Claude Opus 4.6 - General Opus 4.6 model support
[FEATURE]: Add Claude Opus 4.6 support for GitHub Copilot provider #12504: [FEATURE]: Add Claude Opus 4.6 support for GitHub Copilot provider - Specifically addresses Opus 4.6 for GitHub Copilot
Support adaptive thinking for Claude Opus 4.6 #12485: Support adaptive thinking for Claude Opus 4.6 - Related Opus 4.6 feature

Fast Mode is a specific capability of Opus 4.6. Once Opus 4.6 support is added (especially for GitHub Copilot), the Fast Mode feature would likely be available as part of that implementation.

bump on this

There is an issue on this at models.dev: anomalyco/models.dev#833

@utapyngo

@utapyngo Thanks for letting me know. I didn't realize this was an issue with that repository. I'll go ahead and close this.

@utapyngo Thanks for letting me know. I didn't realize this was an issue with that repository. I'll go ahead and close this.

Actually I would keep this open since it seems that changes to opencode are also required. I tried adding this to my opencode.json:

  "provider": {
    "github-copilot": {
      "models": {
        "claude-opus-4.6-fast": {
          "id": "claude-opus-4.6-fast",
          "name": "Claude Opus 4.6 (fast mode)",
          "family": "claude-opus",
          "attachment": true,
          "reasoning": true,
          "tool_call": true,
          "temperature": true,
          "release_date": "2026-02-07",
          "limit": {
            "context": 200000,
            "output": 64000
          }
        }
      }
    }

The model appeared in the list but the server keeps responding with "The requested model is not supported".

@utapyngo

@utapyngo

(Note: I'm writing this from memory without my work environment in front of me, so some details might not be perfectly accurate.)

Yesterday, after briefly doing some LLM-assisted research and analyzing the microsoft/vscode-copilot-chat extension, I discovered that the Copilot domain and /models endpoint used by OpenCode simply do not expose the claude-opus-4.6-fast model at all.

When I requested /models against the domain OpenCode uses (api.githubcopilot.com), the claude-opus-4.6-fast model was not in the list. As a result, all requests fail with the message: "The requested model is not supported."

However, the model selector in VSCode's official Copilot Chat extension clearly includes Opus 4.6 Fast Mode. Digging into the source code based on that, I found that VSCode actually sends requests to a different domain: api.individual.githubcopilot.com. The /models endpoint on this domain does expose the Fast Mode model.

I still need to investigate this further, but I suspect the authentication workflow itself might be different, and it's unclear if GitHub Copilot intended this behavior or not. Just to be sure, I even tried signing out of GitHub Copilot in OpenCode and authenticating again, but the model still didn't appear in the list.

However, the model selector in VSCode's official Copilot Chat extension clearly includes Opus 4.6 Fast Mode. Digging into the source code based on that, I found that VSCode actually sends requests to a different domain: api.individual.githubcopilot.com. The /models endpoint on this domain does expose the Fast Mode model.

So we need to reopen this issue.

@utapyngo

@utapyngo Okay, I just don't want to bother them. But come to think of it, GitHub Copilot is one of the official providers for OpenCode, isn't it? So I think I need to reopen this. They might even be able to request GitHub Copilot to support Fast Mode for OpenCode as well.

Would love to see this for GPT 5.4 fast mode as well!

selecting opus 4.6 from github copilot seems to be using the fast model by default and charging 30x credit, i came across a similar post in reddit. a fast selector would be nice as i donot want 10% of my credits to be gone in an instant.

please

I think this feature might become urgent. Background: Copilot seems to rate-limit Opus 4.6 quite hard. But the fast version is obviously performing full-speed ( "paying4speed")

Would be great to see an improvement here.

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[FEATURE]: Support for Claude Opus 4.6 Fast Mode #12923

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[FEATURE]: Support for Claude Opus 4.6 Fast Mode #12923

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github-actions commented on Feb 10, 2026

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utapyngo commented on Mar 3, 2026

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