<p>Simon Willison provides a comprehensive technical analysis of OpenAI's GPT-5 announcement, breaking down the key specifications, pricing structure, and safety considerations detailed in the official system card.</p> <p>The analysis highlights GPT-5's technical specifications: 272,000 input tokens and 128,000 output tokens, representing a significant context window expansion. The model introduces four reasoning levels, allowing users to balance speed and accuracy based on their specific needs.</p> <p>Willison examines the three-tier pricing model: GPT-5 at $1.25/$10, GPT-5 Mini at $0.25/$2, and GPT-5 Nano at $0.05/$0.40 per million tokens. He particularly notes the 90% caching discount, which could dramatically reduce costs for applications with repeated context.</p> <p>The system card reveals OpenAI's extensive safety testing, including red-teaming exercises and alignment research. Key improvements include reduced hallucination rates, better factual accuracy, and enhanced reasoning capabilities compared to GPT-4.</p> <p>"The knowledge cutoff differences are interesting," Willison observes. "Full GPT-5 uses data through September 2024, while the smaller variants only go to May 2024. This suggests different training approaches for different model sizes."</p> <p>The analysis concludes that GPT-5's combination of increased context length, improved accuracy, and competitive pricing positions it as a significant advancement in the large language model landscape.</p>