Troubleshooting GitHub Copilot Chat: Unblocking Network Issues for Developer Software

When Your AI Co-Pilot Hits a Network Wall

GitHub Copilot Chat is an indispensable piece of developer software for many, offering real-time coding assistance and explanations directly within the IDE. However, even the most advanced tools can encounter roadblocks, particularly when network configurations interfere. A recent discussion on the GitHub Community forum highlighted a common scenario: Copilot Chat suddenly stopped working, leading to a deep dive into network diagnostics.

The Problem: Copilot Chat Offline

User dariuspranskus initiated a discussion after experiencing 14 hours of Copilot Chat inactivity. Running the built-in diagnostics revealed a series of network checks, with most core Copilot services (api.github.com, api.githubcopilot.com, copilot-proxy.githubusercontent.com) showing successful HTTP 200 responses for IPv4. However, a critical failure was observed for https://default.exp-tas.com, returning an HTTP 400 error, alongside HTTP 404 errors for certain Microsoft telemetry endpoints. IPv6 DNS lookups also consistently failed with ENOTFOUND.

The diagnostic output provided valuable clues:

## GitHub Copilot Chat - Extension: 0.37.2 (prod) - VS Code: 1.109.0 (bdd88df003631aaa0bcbe057cb0a940b80a476fa) - OS: win32 10.0.26200 arm64 - GitHub Account: dariuspranskus ## Network User Settings: "http.systemCertificatesNode": false, "github.copilot.advanced.debug.useElectronFetcher": true, "github.copilot.advanced.debug.useNodeFetcher": false, "github.copilot.advanced.debug.useNodeFetchFetcher": true Connecting to https://api.github.com: - DNS ipv4 Lookup: 4.237.22.34 (16 ms) - DNS ipv6 Lookup: Error (15 ms): getaddrinfo ENOTFOUND api.github.com - Proxy URL: None (0 ms) - Electron fetch (configured): HTTP 200 (13 ms) - Node.js https: HTTP 200 (50 ms) - Node.js fetch: HTTP 200 (27 ms) Connecting to https://api.githubcopilot.com/_ping: - DNS ipv4 Lookup: 140.82.112.21 (19 ms) - DNS ipv6 Lookup: Error (36 ms): getaddrinfo ENOTFOUND api.githubcopilot.com - Proxy URL: None (20 ms) - Electron fetch (configured): HTTP 200 (655 ms) - Node.js https: HTTP 200 (646 ms) - Node.js fetch: HTTP 200 (644 ms) Connecting to https://copilot-proxy.githubusercontent.com/_ping: - DNS ipv4 Lookup: 4.237.22.41 (151 ms) - DNS ipv6 Lookup: Error (147 ms): getaddrinfo ENOTFOUND copilot-proxy.githubusercontent.com - Proxy URL: None (2 ms) - Electron fetch (configured): HTTP 200 (64 ms) - Node.js https: HTTP 200 (62 ms) - Node.js fetch: HTTP 200 (88 ms) Connecting to https://mobile.events.data.microsoft.com: HTTP 404 (186 ms) Connecting to https://dc.services.visualstudio.com: HTTP 404 (65 ms) Connecting to https://copilot-telemetry.githubusercontent.com/_ping: HTTP 200 (663 ms) Connecting to https://copilot-telemetry.githubusercontent.com/_ping: HTTP 200 (646 ms) Connecting to https://default.exp-tas.com: HTTP 400 (83 ms) Number of system certificates: 32 ## Documentation In corporate networks: Troubleshooting firewall settings for GitHub Copilot.

Community Insights and Solutions

A fellow community member, argenis972, provided an insightful analysis and actionable troubleshooting steps. The key takeaway was that while the core Copilot service endpoints were reachable, the issues with default.exp-tas.com (an experimentation and telemetry endpoint) were likely the culprit. This often points to interference from corporate network security measures.

Here are the recommended steps to troubleshoot and resolve such network issues for your developer software:

• Network Isolation Test: Try using Copilot from a different network, such as a mobile hotspot. This helps determine if the issue is specific to your corporate network's firewall, DNS filtering, or VPN.
• Disable Network Intermediaries: Temporarily disable any VPN, proxy, or security agents (like antivirus or network inspection tools) that might be intercepting or blocking network traffic.
• Reset Copilot Advanced Settings: Custom fetcher/debug flags in VS Code settings (e.g., github.copilot.advanced.debug.useElectronFetcher) can sometimes interfere. Remove these custom settings to revert to default behavior.
• Clear Extension State: A corrupted extension cache can cause unexpected behavior. Follow these steps:
  1. Disable the GitHub Copilot extension in VS Code.
  2. Close VS Code completely.
  3. Delete the Copilot extension cache (typically found in your user data directory, e.g., %APPDATA%\Code\User\globalStorage\github.copilot on Windows).
  4. Reinstall the Copilot extension.
• Whitelist Essential Domains: Ensure that your network's firewall or DNS filter is not blocking the following critical domains:
  • api.githubcopilot.com
  • copilot-proxy.githubusercontent.com
  • default.exp-tas.com
  • githubusercontent.com

If the problem appeared suddenly without any configuration changes, it's also worth considering if a backend service rollout or an update to your enterprise's network policy might be responsible.

Conclusion

Ensuring seamless operation of essential developer software like GitHub Copilot Chat often requires careful attention to network configuration. By systematically diagnosing and addressing potential network blocks, especially those related to corporate firewalls or custom settings, developers can quickly restore their AI assistant's functionality and maintain peak productivity.