feat: add support for GitHub Models provider

- Introduced environment variable CLAUDE_CODE_USE_GITHUB to enable GitHub Models.
- Added checks for GITHUB_TOKEN or GH_TOKEN for authentication.
- Updated base URL handling to include GitHub Models default.
- Enhanced provider detection and error handling for GitHub Models.
- Updated relevant functions and components to accommodate the new provider.

src/services/api/providerConfig.ts

@@ -2,8 +2,12 @@ import { existsSync, readFileSync } from 'node:fs'
 import { homedir } from 'node:os'
 import { join } from 'node:path'
 
+import { isEnvTruthy } from '../../utils/envUtils.js'
+
 export const DEFAULT_OPENAI_BASE_URL = 'https://api.openai.com/v1'
 export const DEFAULT_CODEX_BASE_URL = 'https://chatgpt.com/backend-api/codex'
+/** Default GitHub Models API model when user selects copilot / github:copilot */
+export const DEFAULT_GITHUB_MODELS_API_MODEL = 'openai/gpt-4.1'
 
 const CODEX_ALIAS_MODELS: Record<
   string,
@@ -171,6 +175,20 @@ export function isCodexBaseUrl(baseUrl: string | undefined): boolean {
   }
 }
 
+/**
+ * Normalize user model string for GitHub Models inference (models.github.ai).
+ * Mirrors runtime devsper `github._normalize_model_id`.
+ */
+export function normalizeGithubModelsApiModel(requestedModel: string): string {
+  const noQuery = requestedModel.split('?', 1)[0] ?? requestedModel
+  const segment =
+    noQuery.includes(':') ? noQuery.split(':', 2)[1]!.trim() : noQuery.trim()
+  if (!segment || segment.toLowerCase() === 'copilot') {
+    return DEFAULT_GITHUB_MODELS_API_MODEL
+  }
+  return segment
+}
+
 export function resolveProviderRequest(options?: {
   model?: string
   baseUrl?: string
@@ -192,10 +210,16 @@ export function resolveProviderRequest(options?: {
       ? 'codex_responses'
       : 'chat_completions'
 
+  const resolvedModel =
+    transport === 'chat_completions' &&
+    isEnvTruthy(process.env.CLAUDE_CODE_USE_GITHUB)
+      ? normalizeGithubModelsApiModel(requestedModel)
+      : descriptor.baseModel
+
   return {
     transport,
     requestedModel,
-    resolvedModel: descriptor.baseModel,
+    resolvedModel,
     baseUrl:
       (rawBaseUrl ??
         (transport === 'codex_responses'