GPT-5.4 Mini & Nano: OpenAI Introduces a Subagent Hierarchy
OpenAI released GPT-5.4 Mini and Nano this week, introducing a revolutionary subagent architecture where the flagship GPT-5.4 acts as a 'Senior Partner' that delegates work to cheaper, faster Mini and Nano 'interns' — fundamentally changing how multi-step AI tasks are structured. GPT-5.4 Mini ($0.75/M tokens) scores 54.4% on SWE-Bench Pro and GPT-5.4 Nano ($0.20/M tokens) directly undercuts rival models.