o3
o3 is OpenAI's advanced reasoning model that succeeds o1, delivering stronger chain-of-thought performance on mathematical, scientific, and coding problems with improved efficiency and full tool support.
import { streamText } from 'ai'
const result = streamText({ model: 'openai/o3', prompt: 'Why is the sky blue?'})What To Consider When Choosing a Provider
Zero Data Retention
AI Gateway does not currently support Zero Data Retention for this model. See the documentation for models that support ZDR.Authentication
AI Gateway authenticates requests using an API key or OIDC token. You do not need to manage provider credentials directly.
o3 generates internal reasoning tokens that work through problems step by step before producing a visible response. This trades latency for accuracy on hard problems.
Unlike earlier reasoning previews, o3 ships with function calling, structured outputs, vision, and system messages from day one.
When to Use o3
Best For
Advanced mathematical reasoning:
Competition-level math, proofs, and quantitative analysis
Complex coding problems:
Algorithm design, optimization, and architectural reasoning
Scientific analysis:
Multi-step derivations in physics, chemistry, and biology
Agentic reasoning:
Agent backbones that need deep deliberation before acting
Hard problem solving:
Any task where extended chain-of-thought produces measurably better results
Consider Alternatives When
General-purpose tasks:
GPT-5 or GPT-5.2 for conversational and generative workloads that don't need chain-of-thought
Cost-sensitive reasoning:
O4-mini for reasoning at a lower price point
Maximum reasoning compute:
O3-pro for the hardest problems that benefit from extended computation
Fast responses:
GPT-5.1 instant or GPT-4o when latency matters more than reasoning depth
Conclusion
o3 advances reasoning model capability beyond o1, delivering stronger performance and greater efficiency than o1 with full production API features. For the hardest analytical, mathematical, and coding problems routed through AI Gateway, it is the standard reasoning model.
FAQ
It delivers stronger performance on reasoning benchmarks while using reasoning tokens more efficiently, resulting in better accuracy at comparable or lower cost per request.
Yes. It ships with function calling, structured outputs, vision input, and system messages, the full production API feature set.
It controls how deeply the model reasons per request. Low effort for simple queries saves cost; high effort for hard problems enables maximum deliberation.
200K tokens, supporting lengthy inputs for complex reasoning tasks.
AI Gateway accepts a single API key or OIDC token for all requests. You don't embed OpenAI credentials in your application; AI Gateway routes and authenticates on your behalf.
Use o3 for problems that benefit from extended chain-of-thought reasoning (math, science, hard coding). Use GPT-5 for general-purpose tasks, creative writing, and conversational workloads.
This page shows live throughput and time-to-first-token metrics measured across real AI Gateway traffic.
