Introducing GPT-5 for developers

Introduction

Today, we’re releasing GPT‑5 in our API platform—our best model yet for coding and agentic tasks.

GPT‑5 is state-of-the-art (SOTA) across key coding benchmarks, scoring 74.9% on SWE-bench Verified and 88% on Aider polyglot. We trained GPT‑5 to be a true coding collaborator. It excels at producing high-quality code and handling tasks such as fixing bugs, editing code, and answering questions about complex codebases. The model is steerable and collaborative—it can follow very detailed instructions with high accuracy and can provide upfront explanations of its actions before and between tool calls.  The model also excels at front-end coding, beating OpenAI o3 at frontend web development 70% of the time in internal testing.

We trained GPT‑5 on real-world coding tasks in collaboration with early testers across startups and enterprises. Cursor says GPT‑5 is “the smartest model [they’ve] used” and “remarkably intelligent, easy to steer, and even has a personality [they] haven’t seen in other models.” Windsurf shared GPT‑5 is SOTA on their evals and “has half the tool calling error rate over other frontier models.” Vercel says “it’s the best frontend AI model, hitting top performance across both the aesthetic sense and the code quality, putting it in a category of its own.”

We’re introducing new features in our API to give developers more control over model responses. GPT‑5 supports a new verbosity parameter (values: low, medium, high) to help control whether answers are short and to the point or long and comprehensive. GPT‑5’s reasoning_effort parameter can now take a minimal value to get answers back faster, without extensive reasoning first. We’ve also added a new tool type—custom tools—to let GPT‑5 call tools with plaintext instead of JSON. Custom tools support constraining by developer-supplied context-free grammars.