Function transform

sdk/src/impl/chatgpt-backend-fetch.ts:413–434

(chunk, controller)

  return new TransformStream<Uint8Array, Uint8Array>({
    transform(chunk, controller) {
      buffer += decoder.decode(chunk, { stream: true })

      const lines = buffer.split('\n')
      buffer = lines.pop() ?? ''

      for (const line of lines) {
        if (!line.startsWith('data: ')) continue

        const jsonStr = line.slice(6).trim()
        if (!jsonStr || jsonStr === '[DONE]') {
          continue
        }

        try {
          const parsed = JSON.parse(jsonStr) as Record<string, unknown>
          processEvent(controller, parsed)
        } catch {
          // Skip unparseable lines
        }
      }
    },

    flush(controller) {
      if (buffer.trim().startsWith('data: ')) {