GPT-5.5 Prompting Guide (simonwillison.net)

OpenAI has released a comprehensive prompting guide for its latest model, GPT-5.5, aimed at helping developers effectively transition from earlier iterations like GPT-5.2 and GPT-5.4. The guide emphasizes an important approach: instead of simply migrating existing prompts, it encourages users to treat GPT-5.5 as a distinct model family, starting from a clean baseline to optimize performance. This is particularly significant as it highlights the need for tailored prompts to leverage the model's improved capabilities, ensuring that developers recalibrate rather than assume previous structures will function the same way. One recommended strategy is to provide initial user-visible updates during multi-step tasks. This technique, already implemented in OpenAI’s Codex app, improves user experience by confirming the task is in progress, thus alleviating concerns that the model has stalled. Furthermore, the migration process involves specific instructions for updating code, ensuring that developers can seamlessly integrate the new model with minimal disruption. Overall, these guidelines not only enhance user interaction but also represent a thoughtful evolution in how developers are encouraged to interact with advanced AI models, fostering a more effective use of AI capabilities.