OpenAI GPT-5.3-Codex and Anthropic Claude Opus 4.6 Launch in Dramatic Simultaneous Release

A Dramatic Simultaneous Launch

On February 5, 2026, the AI industry witnessed a dramatic moment. OpenAI and Anthropic had originally planned to release their agentic coding tools at exactly 10 AM PST, but Anthropic moved its launch up by 15 minutes, releasing Claude Opus 4.6 first. OpenAI responded immediately with GPT-5.3-Codex at 10:01 AM.

This incident symbolizes the intense competition in the AI industry. Both companies sought first-mover advantage in the agentic coding tools market, believing that even a few minutes could impact market perception.

GPT-5.3-Codex: The Self-Building AI

OpenAI's GPT-5.3-Codex is an agentic coding model designed to handle nearly all developer tasks. Most notably, this is OpenAI's first model that was instrumental in creating itself.

The Codex team used early versions to debug its own training, manage its own deployment, and diagnose test results and evaluations. This demonstrates a new paradigm where AI directly contributes to AI development.

In terms of performance, GPT-5.3-Codex combines the frontier coding performance of GPT-5.2-Codex with the reasoning and professional knowledge capabilities of GPT-5.2 in a single model, while also being 25% faster.

Claude Opus 4.6: Anthropic's Response

Anthropic's Claude Opus 4.6 was developed with similar agentic coding capabilities. While specific technical specifications haven't been publicly detailed, Anthropic actively sought market advantage by moving up its announcement time.

Both models emphasize capabilities beyond simple code writing, including the ability to build complex applications over multiple days.

Security Concerns and Staged Rollout

OpenAI warned that GPT-5.3-Codex's powerful coding capabilities could pose unprecedented cybersecurity risks, rolling out the model with unusually tight controls. Full developer access is delayed, with only paid ChatGPT users able to use the model for everyday software development tasks (writing, debugging, testing).

Fortune reported concerns that the model could be used to generate sophisticated malware or exploit vulnerabilities, leading OpenAI to adopt a staged release strategy.

The AI Coding Wars Accelerate

This simultaneous launch highlights how competitive the AI coding tools market has become. With Big Tech players like Microsoft (GitHub Copilot), Google (Gemini Code Assist), and Amazon (CodeWhisperer) all competing in this space, OpenAI and Anthropic are differentiating through the most advanced agentic capabilities.

The developer community is closely comparing both models, with real-world project performance, cost, and usability expected to determine the ultimate winner.

Sources

TechCrunch: OpenAI launches new agentic coding model only minutes after Anthropic drops its own

OpenAI: Introducing GPT-5.3-Codex

Fortune: OpenAI's new model leaps ahead in coding capabilities—but raises unprecedented cybersecurity risks