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Fixing GitHub Copilot 'Invalid Authorization Header' & Freezing Issues

 There are few things more disruptive to a developer’s flow state than an AI assistant that suddenly goes silent. You are in the middle of a complex refactor, you prompt GitHub Copilot Chat, and instead of a solution, you get a loading spinner that spins indefinitely.

Eventually, the Output logs reveal the culprit: a 400 or 401 error, specifically the Invalid Authorization Header.

This guide targets professional developers and enterprise users experiencing persistent Copilot authentication failures. We will move beyond basic troubleshooting to diagnose the root cause of token desynchronization and implement a permanent fix within your VS Code environment.

The Root Cause: Token Desynchronization

To fix the issue, you must understand the architecture of the failure. GitHub Copilot relies on a secure handshake between your local VS Code client and GitHub’s API endpoints (typically via api.github.com).

When you sign in, VS Code acquires an OAuth2 access token. This token is cached locally to minimize latency. The "Invalid Authorization Header" error rarely implies your account is inactive; rather, it indicates a state mismatch.

Why the Header Becomes Invalid

  1. Token Rotation Failures: GitHub’s authentication servers rotate tokens periodically. If your VS Code session persists for days (or across sleep/wake cycles), the local client may attempt to send an expired or malformed token format that the server no longer accepts.
  2. Enterprise Proxy Interference: In corporate environments, Zscaler, Cisco AnyConnect, or other packet-inspecting proxies often intercept the SSL handshake. They may strip or alter the Authorization header, resulting in a 400 Bad Request.
  3. Extension Context Corruption: The Copilot extension maintains its own session context. If the extension updates in the background while VS Code is open, the in-memory context can become stale while the disk-based configuration is new, leading to API rejection.

Diagnostic Phase: verifying Connectivity

Before altering configurations, we must ensure your machine can actually reach GitHub's authentication servers. We will use a modern Node.js script to bypass VS Code and test the raw connection.

Create a file named diag-copilot.mjs (ES Modules) and run it with Node.js (v18+).

import https from 'node:https';

/**
 * Diagnostic script to verify connectivity to GitHub API
 * independent of VS Code settings.
 */
const checkConnectivity = async () => {
  const url = 'https://api.github.com/zen';
  
  console.log(`[Diagnostic] Pinging ${url}...`);

  try {
    const response = await fetch(url, {
      method: 'GET',
      headers: {
        'User-Agent': 'VSCode-Copilot-Diagnostic/1.0',
        'Accept': 'application/vnd.github.v3+json'
      }
    });

    if (response.ok) {
      const data = await response.text();
      console.log(`[Success] GitHub API is reachable. Server says: "${data}"`);
    } else {
      console.error(`[Error] HTTP ${response.status}: ${response.statusText}`);
      // A 403 here is fine (rate limiting), but 407 implies Proxy issues.
    }
  } catch (error) {
    console.error('[Critical] Network unreachable. This is a local network/proxy issue.');
    console.error(error.message);
  }
};

checkConnectivity();

If this script fails with a timeout or certificate error, your issue is network-level (VPN/Proxy). If it succeeds, the issue is isolated to VS Code's internal state.

Solution 1: The Hard Token Flush

Simply clicking "Sign out" in the UI is often insufficient because VS Code caches credentials in the OS keychain (macOS Keychain, Windows Credential Manager, or Linux Keyring). We need to force a complete flush.

Step-by-Step Execution

  1. In VS Code, open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P).
  2. Type and select: "Developer: Reload Window". (Do this first to clear in-memory states).
  3. Open Command Palette again and select: "Sign out of GitHub".
    • Note: If you see multiple accounts, sign out of ALL of them.
  4. Critical Step: Close VS Code completely.
  5. Open your terminal and verify no lingering VS Code processes exist.
  6. Relaunch VS Code.
  7. Select the Accounts icon (bottom left) and "Turn on Settings Sync" or click the Copilot icon to trigger a fresh OAuth flow.

This forces the extension to request a completely new JSON Web Token (JWT) rather than refreshing the cached (and likely corrupted) one.

Solution 2: Handling Enterprise Proxies

If you work in a corporate environment, the "Invalid Authorization Header" is frequently caused by VS Code trying to verify SSL certificates that your company's proxy has re-signed.

You must configure settings.json to handle the proxy correctly.

  1. Open your User Settings JSON (Ctrl+Shift+P -> "Preferences: Open User Settings (JSON)").
  2. Add or modify the following configurations:
{
  // Allow VS Code to read proxy settings from your OS environment variables
  "http.proxySupport": "override",

  // STRICT SSL configuration
  // Set to 'false' TEMPORARILY to test if the proxy certificate is the issue.
  // Ideally, keep this 'true' and install your company's root CA.
  "http.proxyStrictSSL": false,

  // Advanced Copilot network settings
  "github.copilot.advanced": {
    "debug.useNodeFetcher": true
  }
}

Why useNodeFetcher matters

By default, Copilot might use an internal networking stack. Setting debug.useNodeFetcher to true forces the extension to use the Node.js networking stack, which respects the global http_proxy and https_proxy environment variables more reliably than the internal VS Code fetcher.

Solution 3: The "Chat View" Reset

Sometimes the authorization is valid, but the UI thread handling the Chat window freezes. This looks like an auth error but is actually a render process hang.

Instead of restarting the whole IDE, you can restart just the extension host.

  1. Open the Command Palette.
  2. Type: "Developer: Restart Extension Host".

This reloads all extensions without closing your open files or terminal sessions. It is the fastest way to recover from a "spinning loading indicator" in Copilot Chat.

Deep Dive: Inspecting Copilot Logs

To prevent this from recurring, you need to know exactly what the API is rejecting.

  1. Open the bottom panel in VS Code (Ctrl+J).
  2. Navigate to the Output tab.
  3. In the dropdown menu (usually showing "Tasks" or "Extensions"), select GitHub Copilot Chat.

Look for lines resembling this:

[ERROR] [default] [2023-10-27T14:20:00.000Z] Request to https://api.githubusercontent.com/failed: 401 Unauthorized

If you see 407 Proxy Authentication Required, your http.proxySupport setting (Solution 2) is incorrect. If you see 401, it is the token mismatch (Solution 1).

Summary

The "Invalid Authorization Header" is a synchronization drift between your local VS Code keychain and GitHub's identity provider.

  1. Run the Node.js diagnostic to rule out total network failure.
  2. Perform a Hard Token Flush to purge corrupted JWTs.
  3. Adjust http.proxySupport if you are behind a corporate firewall.
  4. Restart the Extension Host to fix UI freezes without losing work.

By treating the authentication mechanism as a volatile state that requires periodic flushing, you can maintain a stable connection and keep your AI workflow uninterrupted.

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