github-mcp-server fails with "fetch failed" since 1.0.51 update #3455

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1. bartuszekj

   added the

   Bug

   issue type on May 21, 2026
2. bartuszekj

   added

   triage

   on May 21, 2026
3. examon

   added

   area:mcpMCP server configuration, discovery, connectivity, OAuth, policy, and registryMCP server configuration, discovery, connectivity, OAuth, policy, and registry

   area:platform-windowsWindows-specific: PowerShell, cmd, Git Bash, WSL, Windows TerminalWindows-specific: PowerShell, cmd, Git Bash, WSL, Windows Terminal

   area:networkingProxy, SSL/TLS, certificates, corporate environments, and connectivity issuesProxy, SSL/TLS, certificates, corporate environments, and connectivity issues

   on May 21, 2026
4. github-actions

   removed

   triage

   on May 21, 2026
5. melscoop commented on Jun 12, 2026

   

   melscoop

   on Jun 12, 2026

   Last edited by melscoop

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   👋 Another report of this - experiencing an issue with GitHub Copilot CLI 1.0.60 (latest) where the built-in GitHub MCP server github-mcp-server fails to initialize.

   Running /mcp show github-mcp-server consistently reports:

   Status: Failed
   Error: fetch failed
   

   Reauthentication attempts also fail with:

   MCPOAuthError: Failed to discover authorization server metadata
   

   However, manual validation confirms that network connectivity, TLS, OAuth metadata discovery, and authenticated MCP requests are all working outside of Copilot CLI. This suggests the failure is specific to Copilot CLI MCP initialization or OAuth handling, rather than a customer network, certificate, proxy, VPN, or account issue.

   Environment

   • GitHub Copilot CLI: 1.0.60
   • GitHub CLI: latest confirmed installed
   • Third-party MCP servers: working
   • Built-in github-mcp-server: failing consistently

   Troubleshooting performed

   Network and TLS validation

   The following checks succeeded:

   • curl https://api.githubcopilot.com/_ping
   • curl -vI https://api.business.githubcopilot.com/mcp/readonly

   The unauthenticated MCP request returned 401 as expected.

   Additional validation:

   • TLS handshake succeeds.
   • Certificate validation succeeds using the system trust store.
   • No proxy-related environment variables are present.
   • Issue reproduces both with and without the company VPN.

   OAuth metadata validation

   The OAuth protected resource metadata endpoint succeeds:

   curl https://api.githubcopilot.com/.well-known/oauth-protected-resource/mcp/readonly

   Result:

   • HTTP 200
   • Valid OAuth metadata returned

   Authenticated MCP validation

   The customer retrieved a token using:

   gh auth token

   They then performed an authenticated MCP initialize request directly against the GitHub Copilot MCP endpoint:

   curl -N -v 'https://api.githubcopilot.com/mcp/readonly' \
     --header 'Content-Type: application/json' \
     --header 'Accept: application/json, text/event-stream' \
     --header 'Authorization: Bearer <token>' \
     --data '{
       "jsonrpc": "2.0",
       "id": 1,
       "method": "initialize",
       "params": {
         "capabilities": {},
         "clientInfo": {
           "name": "torc-mcp-cli-debug",
           "version": "0.0.1"
         }
       }
     }'

   Result:

   • HTTP 200
   • MCP session created successfully
   • Server returned a valid JSON-RPC response
   • Response included capabilities and serverInfo
   • Server identified itself as github-mcp-server

   Relevant response details:

   {
     "jsonrpc": "2.0",
     "id": 1,
     "result": {
       "capabilities": {
         "completions": {},
         "prompts": {},
         "resources": {},
         "tools": {}
       },
       "protocolVersion": "2025-11-25",
       "serverInfo": {
         "name": "github-mcp-server",
         "title": "GitHub MCP Server",
         "version": "github-mcp-server/remote-020eb95790f7c817b0dd5bc3675b3d7ec88fbf0f"
       }
     }
   }

   CLI state validation

   The customer performed the following without resolving the issue:

   • Logged out and fully reauthenticated multiple times.
   • Ran /mcp reload repeatedly.
   • Confirmed third-party MCP servers continue to work.
   • Confirmed latest GitHub CLI and Copilot CLI versions are installed.

   Summary

   Manual testing confirms the GitHub Copilot MCP endpoint is reachable and functional from the customer’s environment, including OAuth metadata discovery and authenticated MCP initialization.

   The failure appears isolated to GitHub Copilot CLI’s handling of the built-in github-mcp-server, specifically during MCP initialization and/or OAuth metadata discovery.

   Requesting engineering investigation into Copilot CLI 1.0.60 behavior for built-in GitHub MCP server initialization, particularly around the fetch failed and MCPOAuthError: Failed to discover authorization server metadata errors.
6. melscoop commented on Jun 19, 2026

   

   melscoop

   on Jun 19, 2026

   More actions

   FYI: This issue has been resolved for the client I'd mentioned above after updating to the latest Copilot CLI ☝️

   👍React with 👍1Reacted by Iryna Kulakova
7. patniko commented on Oct 26, 2026

   

   patniko

   on Oct 26, 2026

   Collaborator

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   Thanks for the report. We've shipped fixes in this area since this was filed (most recently in Copilot CLI v1.0.71), and we believe this may now be resolved. Could you retest on the latest release (Copilot CLI v1.0.103) and let us know whether you still see it? If we don't hear back in a couple of weeks, we may close this issue — you can always reopen it.

   _{Triaged as part of a Copilot SDK backlog review, with help from GitHub Copilot.}
8. patniko

   added

   more-info-needed

   on Oct 26, 2026