Function fetch

packages/arctic/src/auth/codex-oauth/index.ts:146–264

* Custom fetch implementation for Codex API * * Handles: * - Token refresh when expired * - URL rewriting for Codex backend * - Request body transformation * - OAuth header injection * - SSE to JSON conversion for non-tool requests * - Error handling a

(
						input: Request | string | URL,
						init?: RequestInit,
					)

					 * @returns Response from Codex API
					 */
					async fetch(
						input: Request | string | URL,
						init?: RequestInit,
					): Promise<Response> {
						// Step 1: Check and refresh token if needed
						let currentAuth = await getAuth();
						if (shouldRefreshToken(currentAuth)) {
							const refreshResult = await refreshAndUpdateToken(
								getAuth,
								client,
							);
							if (!refreshResult.success) {
								return refreshResult.response;
							}
							// Reload auth after refresh to get updated tokens
							currentAuth = refreshResult.auth;
						}

						// Step 2: Extract and rewrite URL for Codex backend
						const originalUrl = extractRequestUrl(input);
						const url = rewriteUrlForCodex(originalUrl);
						// Step 3: Transform request body with model-specific Codex instructions
						// Instructions are fetched per model family (codex-max, codex, gpt-5.1)
						// Capture original stream value before transformation
						// generateText() sends no stream field, streamText() sends stream=true
						const originalBody = init?.body ? JSON.parse(init.body as string) : {};
						const isStreaming = originalBody.stream === true;

						const transformation = await transformRequestForCodex(
							init,
							url,
							userConfig,
							codexMode,
						);
						const requestInit = transformation?.updatedInit ?? init;

						// Step 4: Create headers with OAuth and ChatGPT account info
						const accessToken = (currentAuth as any).accessToken ?? (currentAuth as any).access ?? "";
						const headers = createCodexHeaders(
							requestInit,
							accountId,
							accessToken,
							{
								model: transformation?.body.model,
								promptCacheKey: (transformation?.body as any)?.prompt_cache_key,
							},
						);

						// Step 5: Make request to Codex API
						let response = await fetch(url, {
							...requestInit,
							headers,
						});

						// Check for 401 or token_invalidated error
						let shouldRetry = response.status === 401;
						if (!shouldRetry && !response.ok) {
							try {