Refactor Copilot auth routing to use shared GitHub server host classification (#6400)

* Initial plan

* refactor(api-proxy): dedupe GitHub server host classification

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: Copilot

containers/api-proxy/copilot-auth.test.js

@@ -3,6 +3,7 @@ const {
     resolveCopilotAuthToken,
     resolveApiKey,
     stripBearerPrefix,
+    classifyGithubServerHost,
     isGhesInstance,
     copilotTargetRequiresGitHubTokenPrefix,
   },
@@ -227,6 +228,28 @@ describe('isGhesInstance', () => {
   });
 });
 
+describe('classifyGithubServerHost', () => {
+  it('classifies github.com as github', () => {
+    expect(classifyGithubServerHost({ GITHUB_SERVER_URL: 'https://github.com' })).toEqual({ kind: 'github' });
+  });
+
+  it('classifies *.ghe.com hosts as ghec and returns the tenant subdomain', () => {
+    expect(classifyGithubServerHost({ GITHUB_SERVER_URL: 'https://myorg.ghe.com' })).toEqual({
+      kind: 'ghec',
+      subdomain: 'myorg',
+    });
+  });
+
+  it('classifies non-ghe.com enterprise hosts as ghes', () => {
+    expect(classifyGithubServerHost({ GITHUB_SERVER_URL: 'https://ghes.mycompany.com' })).toEqual({ kind: 'ghes' });
+  });
+
+  it('classifies invalid or missing values safely', () => {
+    expect(classifyGithubServerHost({ GITHUB_SERVER_URL: 'not-a-url' })).toEqual({ kind: 'invalid' });
+    expect(classifyGithubServerHost({})).toEqual({ kind: 'missing' });
+  });
+});
+
 describe('copilotTargetRequiresGitHubTokenPrefix', () => {
   it('returns true for the Enterprise Copilot endpoint', () => {
     expect(copilotTargetRequiresGitHubTokenPrefix('api.enterprise.githubcopilot.com', {})).toBe(true);

containers/api-proxy/providers/copilot-auth.js

@@ -71,6 +71,27 @@ function resolveCopilotAuthToken(env = process.env) {
   return resolveApiKey(env) || stripBearerPrefix(env.COPILOT_GITHUB_TOKEN);
 }
 
+/**
+ * Classify GITHUB_SERVER_URL by host type for auth-routing derivation logic.
+ *
+ * @param {Record<string, string|undefined>} env - Environment variables
+ * @returns {{kind: 'missing'|'invalid'|'github'|'ghec'|'ghes', subdomain?: string}}
+ */
+function classifyGithubServerHost(env = process.env) {
+  const serverUrl = env.GITHUB_SERVER_URL;
+  if (!serverUrl) return { kind: 'missing' };
+  try {
+    const hostname = new URL(serverUrl).hostname;
+    if (hostname === 'github.com') return { kind: 'github' };
+    if (hostname.endsWith('.ghe.com')) {
+      return { kind: 'ghec', subdomain: hostname.slice(0, -8) };
+    }
+    return { kind: 'ghes' };
+  } catch {
+    return { kind: 'invalid' };
+  }
+}
+
 /**
  * Derive the Copilot API target hostname from environment variables.
  *
@@ -91,21 +112,9 @@ function deriveCopilotApiTarget(env = process.env) {
     // fall through to auto-derivation when the value is malformed.
     if (target) return target;
   }
-  const serverUrl = env.GITHUB_SERVER_URL;
-  if (serverUrl) {
-    try {
-      const hostname = new URL(serverUrl).hostname;
-      if (hostname !== 'github.com') {
-        if (hostname.endsWith('.ghe.com')) {
-          const subdomain = hostname.slice(0, -8); // Remove '.ghe.com'
-          return `copilot-api.${subdomain}.ghe.com`;
-        }
-        return 'api.enterprise.githubcopilot.com';
-      }
-    } catch {
-      // Invalid URL — fall through to default
-    }
-  }
+  const serverHost = classifyGithubServerHost(env);
+  if (serverHost.kind === 'ghec') return `copilot-api.${serverHost.subdomain}.ghe.com`;
+  if (serverHost.kind === 'ghes') return 'api.enterprise.githubcopilot.com';
   return 'api.githubcopilot.com';
 }
 
@@ -125,18 +134,8 @@ function deriveGitHubApiTarget(env = process.env) {
     const target = normalizeApiTarget(env.GITHUB_API_URL);
     if (target) return target;
   }
-  const serverUrl = env.GITHUB_SERVER_URL;
-  if (serverUrl) {
-    try {
-      const hostname = new URL(serverUrl).hostname;
-      if (hostname !== 'github.com' && hostname.endsWith('.ghe.com')) {
-        const subdomain = hostname.slice(0, -8);
-        return `api.${subdomain}.ghe.com`;
-      }
-    } catch {
-      // Invalid URL — fall through to default
-    }
-  }
+  const serverHost = classifyGithubServerHost(env);
+  if (serverHost.kind === 'ghec') return `api.${serverHost.subdomain}.ghe.com`;
   return 'api.github.com';
 }
 
@@ -228,15 +227,7 @@ function isGhesInstance(resolvedTarget, env = process.env) {
   if (env.AWF_PLATFORM_TYPE && env.AWF_PLATFORM_TYPE !== 'ghes') return false;
 
   if (resolvedTarget === 'api.enterprise.githubcopilot.com') return true;
-
-  const serverUrl = env.GITHUB_SERVER_URL;
-  if (!serverUrl) return false;
-  try {
-    const hostname = new URL(serverUrl).hostname;
-    return hostname !== 'github.com' && !hostname.endsWith('.ghe.com');
-  } catch {
-    return false;
-  }
+  return classifyGithubServerHost(env).kind === 'ghes';
 }
 
 /**
@@ -303,6 +294,7 @@ module.exports = {
   deriveGitHubApiBasePath,
   isGithubCopilotCatalogTarget,
   isGhesInstance,
+  classifyGithubServerHost,
   copilotTargetRequiresGitHubTokenPrefix,
   getCopilotModelFallbackPolicy,
   // Exported for unit-test access only; not part of the public API.
@@ -315,6 +307,7 @@ module.exports = {
     deriveGitHubApiBasePath,
     isGithubCopilotCatalogTarget,
     isGhesInstance,
+    classifyGithubServerHost,
     copilotTargetRequiresGitHubTokenPrefix,
     getCopilotModelFallbackPolicy,
   },