OpenAI recently unveiled GPT-5-Codex, a version of their flagship GPT-5 model tuned specifically for programming. Today we’re excited to bring this model to Coplay. By pairing GPT-5-Codex’s adaptive reasoning with Coplay’s editor integration and planning features, you get a smarter, more responsive copilot for your game projects.

What Makes GPT-5-Codex Special?

While GPT-5 is a general-purpose language model, the Codex variant was trained on real-world engineering tasks: building projects from scratch, debugging, large-scale refactoring and code review. It inherits GPT-5’s 400K token context window and matches its pricing, but it behaves very differently:

* Adaptive reasoning. Codex dynamically adjusts its “thinking time” based on the complexity of your request. On simple tasks it can use up to 93% fewer tokens than GPT-5, returning concise answers quickly. For hard debugging or sweeping refactors, it iterates longer—sometimes twice as long as GPT-5—to ensure the code works.

* Purpose-built for coding agents. Codex’s training emphasises following instructions closely and producing clean code. It’s less verbose than many models, giving you working code without unnecessary chatter.

* Variable thinking. When paired with Coplay’s thinking slider, you can let the model decide how much reasoning it needs. Slide it up for tough problems or down for quick fixes—the model adapts accordingly.

These features make GPT-5-Codex a natural fit for Coplay. Game development often involves alternating between small tweaks and complex architecture changes; a model that knows when to think hard and when to move quickly is invaluable.

Using GPT-5-Codex in Coplay

Getting started is straightforward:

1. Select the model. In your Coplay settings, choose gpt-5-codex from the model dropdown. The model is available from the same providers that offer GPT-5.

2. Start your Unity task with a prompt.

Why It Matters

Game development often swings between creative bursts and detail-oriented troubleshooting. GPT-5-Codex is built for that duality. It can spit out a quick prototype of a movement script in seconds, then spend the next few minutes stepping through a complex animation bug until it passes your tests—all without you having to micromanage its behaviour.

In internal testing, GPT-5-Codex consistently outperformed GPT-5 on engineering benchmarks. But the numbers only tell part of the story. The model’s tighter, more disciplined code and variable reasoning feel like a more experienced teammate.

We’re thrilled to offer GPT-5-Codex in Coplay. Give it a try on your next project and let us know how it changes your workflow. As always, we’re listening to feedback and working to make Coplay the most capable AI partner for Unity developers.