Add GITHUB_HOST environment variable support for GitHub Enterprise Server and GitHub Enterprise Cloud

[Copilot]

This PR adds support for GitHub Enterprise Server (GHES) and GitHub Enterprise Cloud with data residency by passing the GITHUB_HOST environment variable to the GitHub MCP server Docker container.

Problem

The GitHub MCP server configuration was missing the GITHUB_HOST environment variable, which is required for connecting to GitHub Enterprise Server or GitHub Enterprise Cloud with data residency (ghe.com). Without this variable, the MCP server defaults to connecting to github.com, preventing workflows from working with enterprise GitHub instances.

Solution

Updated all three AI engines (Claude, Custom, and Codex) to include the GITHUB_HOST environment variable in their GitHub MCP server configurations:

• Docker args: Added -e GITHUB_HOST to pass the environment variable to the container
• Environment: Set GITHUB_HOST to ${{ env.GITHUB_SERVER_URL }} (GitHub Actions' built-in environment variable)

Example Configuration

The generated GitHub MCP configuration now includes:

{
  "mcpServers": {
    "github": {
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "GITHUB_PERSONAL_ACCESS_TOKEN",
        "-e", "GITHUB_HOST",
        "ghcr.io/github/github-mcp-server:sha-09deac4"
      ],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "${{ secrets.GITHUB_TOKEN }}",
        "GITHUB_HOST": "${{ env.GITHUB_SERVER_URL }}"
      }
    }
  }
}

This enables the GitHub MCP server to automatically connect to the correct GitHub instance based on where the workflow is running:

• GitHub.com: GITHUB_SERVER_URL = https://github.com
• GitHub Enterprise Server: GITHUB_SERVER_URL = https://your-ghes-instance.com
• GitHub Enterprise Cloud with data residency: GITHUB_SERVER_URL = https://yoursubdomain.ghe.com

Testing

• Added comprehensive test coverage for all three engines
• Verified all existing workflows recompile successfully
• Manually tested workflow compilation to confirm GITHUB_HOST is included in generated configurations
• All existing tests continue to pass

Files Changed

• pkg/workflow/claude_engine.go: Updated renderGitHubClaudeMCPConfig
• pkg/workflow/custom_engine.go: Updated renderGitHubMCPConfig
• pkg/workflow/codex_engine.go: Updated renderGitHubCodexMCPConfig
• pkg/workflow/codex_engine_test.go: Updated test expectations
• pkg/workflow/mcp_config_test.go: Added validation test for GITHUB_HOST

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• api.contoso.com
  • Triggering command: /tmp/go-build527290485/b279/cli.test -test.testlogfile=/tmp/go-build527290485/b279/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true (dns block)
  • Triggering command: /tmp/go-build1584658749/b279/cli.test -test.testlogfile=/tmp/go-build1584658749/b279/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true (dns block)
  • Triggering command: /tmp/go-build4114491301/b279/cli.test -test.testlogfile=/tmp/go-build4114491301/b279/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[kbreit]

Why was this closed without merging? I'm running into this problem.