Function transformRequestBody

sdk/src/impl/chatgpt-backend-fetch.ts:163–206

(
  body: Record<string, unknown>,
)

}

function transformRequestBody(
  body: Record<string, unknown>,
): Record<string, unknown> {
  const messages = (body.messages ?? []) as ChatCompletionsMessage[]
  const tools = body.tools as ChatCompletionsTool[] | undefined

  // Extract system messages into the top-level `instructions` field
  // (required by the ChatGPT backend API)
  const systemMessages = messages.filter((m) => m.role === 'system')
  const nonSystemMessages = messages.filter((m) => m.role !== 'system')
  const instructions = systemMessages
    .map((m) => (typeof m.content === 'string' ? m.content : JSON.stringify(m.content)))
    .join('\n\n')

  const transformed: Record<string, unknown> = {
    model: body.model,
    instructions: instructions || 'You are a helpful assistant.',
    input: convertMessages(nonSystemMessages),
    stream: true,
    store: false,
    include: ['reasoning.encrypted_content'],
  }

  if (tools?.length) {
    transformed.tools = convertTools(tools)
  }
  if (body.tool_choice != null) {
    transformed.tool_choice = body.tool_choice
  }

  // The ChatGPT backend does not support: max_output_tokens, max_tokens,
  // temperature, top_p, stop, frequency_penalty, presence_penalty, logprobs,
  // n, stream_options — omit them all.

  const reasoningEffort = body.reasoning_effort as string | undefined
  transformed.reasoning = {
    effort: reasoningEffort || 'high',
    summary: 'auto',
  }

  transformed.text = { verbosity: 'medium' }

  return transformed
}

// ============================================================================
// Response Transform: Responses API SSE → Chat Completions SSE