OpenAI's latest "Build Hour" session, featuring Bill Chen (Applied AI), Eric Han (Research), and Anoop Kotha (Applied AI), unveiled GPT-5, positioning it as a significant leap in steerable reasoning models. The discussion centered on the model's enhanced capabilities in coding, front-end/UI generation, and agentic task reliability, alongside new parameters designed for optimal developer control and performance. This deep dive offered founders, VCs, and AI professionals a glimpse into the practical applications and strategic implications of OpenAI's most advanced model yet.
GPT-5 is not merely an incremental update; it represents a fundamental shift in AI's role within development workflows. Bill Chen emphatically stated, "GPT-5 is a true coding collaborator." This assertion underscores the model's ability to integrate deeply into development cycles, offering advancements across several critical areas.
The model demonstrates a "step function increase in code quality" and significantly improved front-end UI generation, making it a powerful tool for accelerating development. Beyond raw code, its enhanced collaborativeness and steerability mean developers can guide the AI with unprecedented precision. This allows for more intuitive interactions, moving beyond simple prompt-response to a genuine partnership in building complex systems.
A core insight from the session highlighted GPT-5's robust performance in long-running agentic tasks. Bill Chen explained, "GPT-5 is very reliable at long-running agentic tasks... it does exactly what it's told to do, when conditions arise." This capability signifies a move towards more autonomous AI agents capable of executing multi-step processes, providing detailed explanations, and even proactively correcting their own errors. Such reliability is crucial for complex software engineering tasks, where sequences of tool calls and intricate instruction following are common.
The introduction of the "Responses API" further refines developer interaction with GPT-5. Bill Chen described it as "a V2 version of the Completions API. It's a better and more feature-rich version... that really allows you to take advantage of the full capabilities of reasoning models like GPT-5." This API enables developers to pass back 'reasoning items' for maximum intelligence, ensuring the model retains context and its chain of thought over extended interactions, leading to more coherent and effective outputs. Additionally, parameters like 'minimal reasoning' allow developers to balance intelligence with latency, while 'verbosity' tunes the output length, offering fine-grained control over the model's responses. These features contribute to a more efficient and cost-effective development process, as demonstrated by improved caching performance.
