GPT 5.3 Codex Now Available on AI Gateway

Vercel has made GPT 5.3 Codex available through its AI Gateway platform. This new model consolidates the coding strengths of GPT-5.2-Codex with the reasoning depth of GPT-5.2, delivering a 25% performance improvement while reducing token consumption.

Key Capabilities

The model is purpose-built for long-running agentic work, handling:

• Research and analysis across codebases
• Multi-step execution spanning the full software development lifecycle
• Debugging, deployment, monitoring, and product documentation
• Data analysis and transformation tasks
• Web development with better handling of underspecified prompts and production-ready defaults

A standout feature is the ability to steer the model mid-task without losing context, enabling more dynamic and iterative workflows.

Integration & Usage

To use the model, set the model identifier to openai/gpt-5.3-codex in the Vercel AI SDK:

import { streamText } from 'ai';

const result = streamText({
  model: 'openai/gpt-5.3-codex',
  prompt: `Research our current API architecture, identify performance
     bottlenecks, refactor the slow endpoints, add monitoring,
     and deploy the changes to staging.`,
});

AI Gateway Benefits

Beyond the new model, developers gain access to AI Gateway's unified infrastructure:

• Usage tracking and cost monitoring across multiple providers
• Built-in observability and performance analytics
• Bring Your Own Key (BYOK) support for flexible provider management
• Intelligent routing, retries, and failover for enterprise-grade reliability
• Model leaderboards to benchmark performance across options

Visit the AI Gateway model playground to get started.