GitHub Copilot Enterprise works in 1.2.4 but fails in 1.3.0 with 400 Bad Request on GHE chat/completions

[jfernandezj-telpark]

Bug

GitHub Copilot Enterprise works for a colleague on OpenCode 1.2.4, but fails for me on OpenCode 1.3.0.

In 1.2.4, the provider appears as a dedicated GitHub Copilot Enterprise provider.
In 1.3.0, it appears as GitHub Copilot -> Enterprise.

This looks like a regression in the provider/auth/model mapping after the provider merge.

Environment

• OpenCode version: 1.3.0
• Working comparison version: 1.2.4
• GitHub Enterprise Copilot endpoint: https://copilot-api.<enterprise-domain>.ghe.com
• OS: Linux

What happens

Enterprise auth appears to complete far enough that requests are sent to the enterprise Copilot endpoint, but inference fails with:

• 400 Bad Request
• URL: https://copilot-api.<enterprise-domain>.ghe.com/chat/completions

Example local error payload:

{
  "message": "Bad Request: Bad Request",
  "statusCode": 400,
  "responseBody": "Bad Request\n",
  "metadata": {
    "url": "https://copilot-api.<enterprise-domain>.ghe.com/chat/completions"
  }
}

Why this looks like a regression

On my machine, historical OpenCode session data shows enterprise requests being sent with raw model IDs like:

• claude-sonnet-4.6
• gpt-5.4

But the bundled Copilot model mapping in OpenCode appears to expect Copilot-native model IDs such as:

• duo-chat-sonnet-4-6
• duo-chat-gpt-5-mini

So it looks like in 1.3.0 the enterprise flow switches the base URL correctly, but does not fully switch to the Copilot Enterprise-safe model mapping.

Comparison with working setup

A colleague using 1.2.4 is able to use GitHub Copilot Enterprise successfully.

The UX differs:

• 1.2.4: dedicated GitHub Copilot Enterprise provider
• 1.3.0: GitHub Copilot -> Enterprise

That makes me suspect the regression happened during or after the provider merge/refactor.

Additional local observations

My current auth state is stored under github-copilot with enterprise mode, rather than a separate enterprise provider.

The failing requests are not 401/403; they are 400, which suggests:

• enterprise auth/base URL selection is at least partially working
• the request payload itself is invalid for the enterprise Copilot endpoint

Expected behavior

GitHub Copilot -> Enterprise in 1.3.0 should behave equivalently to the working dedicated GitHub Copilot Enterprise provider in 1.2.4.

Actual behavior

Requests to the GitHub Enterprise Copilot chat endpoint fail with 400 Bad Request.

Possible root cause

A regression in one of:

• enterprise provider/model mapping
• enterprise auth state migration
• request shaping for Copilot Enterprise after merging providers
• raw model IDs being sent where Copilot-native IDs are required

Related work

I noticed these related changes/issues:

• #17847 fix: github copilot enterprise integration
• #14189 fix(opencode): exchange OAuth token for Copilot JWT to fix GitHub Enterprise auth
• #18782 fix(copilot): add token exchange and editor headers for corporate network compatibility

If helpful, I can provide sanitized local logs/error payloads.

[github-actions]

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

• GitHub Copilot Enterprise works in 1.2.4 but fails in 1.3.0 with 400 Bad Request #18936: Nearly identical report filed by the same author 29 seconds later — same bug (GitHub Copilot Enterprise 400 Bad Request on 1.3.0 vs 1.2.4). Please close one of the two to avoid split discussion.

[vikrant82]

I am seeing something similar on 1.3.3. Since may be last week or so, after a few requests - We will see Bad Request from copilot:

{
  "message": {
    "id": "msg_d386e33c8001ba4dA3EIc36ApE",
    "sessionID": "ses_2ce8d7495ffeKNZGV4IHBLwcb0",
    "role": "assistant",
    "time": {
      "created": 1774768239560,
      "completed": 1774768242887
    },
    "parentID": "msg_d34e2a912001X550cRrWyVOQzr",
    "modelID": "claude-opus-4.6",
    "providerID": "github-copilot",
    "mode": "xxx",
    "agent": "xxx",
    "path": {
      "cwd": "xxx",
      "root": "xxx"
    },
    "cost": 0,
    "tokens": {
      "input": 0,
      "output": 0,
      "reasoning": 0,
      "cache": {
        "read": 0,
        "write": 0
      }
    },
    "variant": "thinking",
    "error": {
      "name": "APIError",
      "data": {
        "message": "Bad Request: Bad Request",
        "statusCode": 400,
        "isRetryable": false,
        "responseHeaders": {
          "cache-control": "no-cache",
          "content-security-policy": "default-src 'none'; sandbox",
          "content-type": "text/plain; charset=utf-8",
          "date": "Sun, 29 Mar 2026 07:10:42 GMT",
          "strict-transport-security": "max-age=31536000",
          "transfer-encoding": "chunked",
          "x-content-type-options": "nosniff",
          "x-copilot-api-exp-assignment-context": "e4hcf520:1109203;",
          "x-github-backend": "Kubernetes",
          "x-github-request-id": "2A1E:F573A:2479C1:3094CB:69C8D06F",
          "x-request-id": "00000-0635e83c-9527-4805-b917-74a22e53f706"
        },
        "responseBody": "Bad Request\n",
        "metadata": {
          "url": "https://api.githubcopilot.com/chat/completions"
        }
      }
    }
  },
  "parts": []
}

The URL though is different.. Can this be related ?

[Femumme]

For anyone that faces this issue:

It seems like the provider id has changed from github-copilot-enterprise to github-copilot.

To fix this issue:

1. Remove the github-copilot-enterprise block from ~/.local/share/opencode/auth.json. DO NOT ADD THIS FILE TO ANY LLM - IT CONTAINS CREDENTIALS!!
2. Login again to GHE using opencode auth login
3. Replace any mentions of github-copilot-enterprise in ~/.config/opencode/opencode.json with github-copilot

After that restart opencode and it works again.

Hint: you also have to update the model references in your agents, e.g. github-copilot-enterprise/claude-sonnet-4.6 -> github-copilot/claude-sonnet-4.6

[jfernandezj-telpark]

I was able to resolve this issue by checking the auth config file at ~/.local/share/opencode/auth.json. The problem was that the "enterpriseUrl" attribute was missing from the configuration.
Steps taken:

1. Deleted the auth config block from ~/.local/share/opencode/auth.json
2. Ran reauthentication
3. After reauthenticating, the enterpriseUrl attribute was properly set with the correct enterprise URL
4. The issue was resolved and everything worked as expected
   If you encounter this issue, try removing the auth config block and reauthenticating to ensure all required attributes are properly populated.