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How to Fix "GitHub Copilot could not connect to server" Errors in VS Code

 Few things break a developer's flow state faster than a spinning loading icon where code suggestions should be. If you are working in an enterprise environment, behind a corporate firewall, or using a VPN, you have likely encountered the frustrating "GitHub Copilot could not connect to server" error.

This isn't just a connectivity glitch; it is almost always a Trust Level Security (TLS) or proxy configuration conflict between the Node.js runtime powering VS Code and your network's security infrastructure.

This guide provides a rigorous technical breakdown of why this happens and offers three distinct solutions, ranging from quick configuration overrides to root-level certificate fixes.

The Root Cause: TLS Handshakes and Corporate Proxies

To fix the problem, you must understand the architecture of the failure.

GitHub Copilot operates as a VS Code extension, which runs inside a Node.js process. When Copilot requests suggestions, it initiates an HTTPS request to https://api.githubcopilot.com.

In a standard home network, this is a direct connection. However, in enterprise environments using Deep Packet Inspection (DPI) tools like Zscaler, Palo Alto Networks, or Cisco Umbrella, the connection is intercepted.

  1. The Interception: The corporate proxy acts as a Man-in-the-Middle (MITM). It intercepts the HTTPS request to inspect the traffic for security compliance.
  2. The Re-encryption: To send the data back to your machine, the proxy re-encrypts the traffic using its own Self-Signed Certificate (or a corporate Root CA).
  3. The Rejection: The Node.js runtime inside VS Code has a built-in list of public Root CAs (DigiCert, Let's Encrypt, etc.). It does not natively know about your company's private Root CA.

When Node.js sees the corporate certificate, it flags it as untrusted, throwing errors like UNABLE_TO_VERIFY_LEAF_SIGNATURE or ERR_TLS_CERT_ALTNAME_INVALID. Consequently, the connection is terminated to prevent a potential security breach.

Solution 1: Injecting Custom Certificates (The Robust Fix)

The most "correct" engineering solution is to tell the VS Code Node.js runtime to trust your organization's certificate chain. This maintains security while allowing connectivity.

Step 1: Export the Certificate

First, you need to identify the certificate intercepting your traffic.

  1. Open your browser (Chrome/Edge) and navigate to https://github.com.
  2. Click the Lock Icon in the URL bar.
  3. Select Connection is secure -> Certificate is valid.
  4. Go to the Details or Certification Path tab. Look for the top-most root certificate (e.g., "Zscaler Root CA" or "YourCompany Internal CA").
  5. Export this certificate as a Base64-encoded X.509 (.CER or .PEM) file. Save it to a stable location, e.g., C:\Certs\corporate-ca.pem or ~/.certs/corporate-ca.pem.

Step 2: Configure VS Code to Use System Certificates

Modern versions of VS Code allow the extension host to inherit certificates from the OS trust store, but this is often disabled by default or overridden by strict proxy settings.

Open your settings.json file in VS Code (Ctrl+Shift+P -> "Preferences: Open User Settings (JSON)") and add the following configuration:

{
  "http.systemCertificates": true,
  "http.proxySupport": "override",
  "github.copilot.advanced": {
    "debug.overrideProxyUrl": "http://127.0.0.1:3128" 
  }
}

Note: Remove debug.overrideProxyUrl if you are not explicitly tunneling through a local proxy tool like Fiddler or Charles Proxy. The key setting here is "http.systemCertificates": true.

Step 3: Injecting Certificates via Environment Variables

If the native setting fails (common in Linux/macOS environments or specific Node versions), you must force Node.js to load the extra certificate using the NODE_EXTRA_CA_CERTS environment variable.

For macOS/Linux (Bash/Zsh):

Add this to your .zshrc or .bashrc:

export NODE_EXTRA_CA_CERTS="$HOME/.certs/corporate-ca.pem"

For Windows (PowerShell):

[System.Environment]::SetEnvironmentVariable("NODE_EXTRA_CA_CERTS", "C:\Certs\corporate-ca.pem", "User")

Restart VS Code completely (close all instances) for this variable to take effect in the extension host process.

Solution 2: Configuring Upstream Proxy Settings

If you are behind an authenticating HTTP proxy, Copilot might fail because it doesn't know where to send the traffic. VS Code generally respects the OS proxy settings, but explicit definitions ensure reliability.

Manual Proxy Configuration

In your settings.json, explicitly define the proxy URL. This is often required if your system uses a PAC (Proxy Auto-Config) file, which Node.js struggles to parse natively.

{
  "http.proxy": "http://user:password@proxy.example.com:8080",
  "http.proxyStrictSSL": true
}

Security Warning: Avoid hardcoding passwords in plain text. Ideally, use environment variables (HTTP_PROXY and HTTPS_PROXY) at the OS level so VS Code picks them up automatically without committing credentials to your settings file.

Solution 3: The "Strict SSL" Bypass (Temporary Workaround)

If you are blocked by a deadline and cannot extract certificates immediately, you can disable SSL verification.

Warning: This makes your connection vulnerable to real Man-in-the-Middle attacks. Do not use this on public Wi-Fi (coffee shops, airports). Use this only as a diagnostic step or temporary fix inside a secure corporate network.

Add this to your settings.json:

{
  "http.proxyStrictSSL": false
}

If Copilot connects immediately after saving this file, you have confirmed the issue is a Certificate Trust issue (Solution 1), not a network block.

Diagnostics: Analyzing the Extension Logs

If the solutions above do not resolve the issue, you need to inspect the actual handshake logs.

  1. Open the Output panel in VS Code (Ctrl+Shift+U).
  2. In the dropdown menu (top-right of the panel), select GitHub Copilot.

Look for these specific error codes:

  • self signed certificate in certificate chain: Indicates the OS trust store is ignored. Apply Solution 1 (Step 3).
  • ECONNREFUSED: The extension cannot reach the internet at all. Check your firewall rules or VPN status.
  • 407 Proxy Authentication Required: Your proxy requires credentials. Ensure your http_proxy environment variable includes the user:pass string.

Edge Case: Zscaler and Cisco Umbrella

Security appliances like Zscaler operate by dynamically generating certificates. Occasionally, the intermediate certificate rotates.

If your setup stops working suddenly:

  1. Re-export the certificate chain (Solution 1, Step 1).
  2. Verify if your organization requires a specific "Zscaler Root CA" versus an "Intermediate CA". Always prefer the Root CA for your NODE_EXTRA_CA_CERTS, as it changes less frequently.

Conclusion

The "GitHub Copilot could not connect to server" error is rarely a GitHub outage. It is a symptom of modern enterprise security conflicting with Node.js networking.

By explicitly managing the Chain of Trust via NODE_EXTRA_CA_CERTS or correctly configuring the http.proxy settings in VS Code, you can permanently resolve these interruptions. Avoid relying on http.proxyStrictSSL: false permanently; treating the root cause by importing the correct certificates ensures both security and productivity.

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