On February 5, 2026, something unprecedented happened: OpenAI and Anthropic released their flagship coding models on the exact same day.
GPT-5.3-Codex and Claude Opus 4.6 both claim to be the best agentic coding model. Here's how they actually compare.
The Same-Day Release
Whether by coincidence or competitive intelligence, both companies dropped their biggest coding updates within hours of each other:
- Claude Opus 4.6 — Anthropic's smartest model with agent teams and 1M context
- GPT-5.3-Codex — OpenAI's most capable agentic coder, 25% faster than 5.2
The AI coding war just got real.
Head-to-Head Comparison
| Feature | Claude Opus 4.6 | GPT-5.3-Codex |
|---|---|---|
| Context Window | 1M tokens (beta) | Not disclosed |
| Multi-Agent | Agent Teams (native) | No (single agent) |
| Terminal-Bench 2.0 | #1 | #2 |
| SWE-Bench Pro | State-of-the-art | State-of-the-art |
| Self-Training | No | Yes (trained itself) |
| Interactive Steering | Limited | Real-time feedback |
| Speed | Standard | 25% faster than 5.2 |
| Pricing (Input) | $5/M tokens | Not disclosed |
| Pricing (Output) | $25/M tokens | Not disclosed |
Opus 4.6 Unique Features
Agent Teams
Opus 4.6's headline feature. Instead of one agent working sequentially, you can spawn multiple specialized agents working in parallel:
- One agent handles frontend
- Another works on the API
- A third writes tests
- They coordinate autonomously
No other model has this capability built-in.
1 Million Token Context
First Opus-class model with the massive context window previously reserved for Sonnet. Load entire codebases in one session.
500 Zero-Days Found
Within hours of release, Opus 4.6 discovered 500+ previously unknown security vulnerabilities in open-source code. Demonstrates exceptional code analysis capabilities.
GPT-5.3-Codex Unique Features
Self-Improvement
GPT-5.3-Codex is the first model instrumental in creating itself. The Codex team used early versions to:
- Debug its own training
- Manage its own deployment
- Diagnose test results
This recursive self-improvement is a significant milestone.
Interactive Steering
You can interact with Codex while it's working without losing context. Ask questions, discuss approaches, and steer toward solutions in real-time.
Speed
25% faster than GPT-5.2-Codex while being more capable. Uses fewer tokens to achieve the same results.
Benchmark Showdown
Terminal-Bench 2.0
Measures agentic coding capabilities. Winner: Opus 4.6
SWE-Bench Pro
Real-world software engineering across 4 languages. Both achieve state-of-the-art
GDPval-AA
Knowledge work (finance, legal). Winner: Opus 4.6 (+144 Elo vs GPT-5.2)
OSWorld
Computer use and desktop tasks. Winner: GPT-5.3-Codex
Which Should You Use?
Choose Opus 4.6 if you need:
- Multi-agent parallel workflows
- Massive context (1M tokens)
- Best-in-class code review
- Security vulnerability detection
- Transparent, predictable pricing
Choose GPT-5.3-Codex if you need:
- Interactive real-time steering
- Maximum speed
- Computer use / desktop automation
- OpenAI ecosystem integration
The Bigger Picture
This same-day release signals we're in a new era of AI competition. Both companies are pushing hard on agentic coding—the ability for AI to not just write code, but to plan, execute, debug, and iterate autonomously.
For developers, this means:
- Better tools — Competition drives innovation
- Lower prices — Eventually
- More choice — Pick the right tool for each task
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Conclusion
There's no clear winner. Opus 4.6 leads on multi-agent capabilities and context. GPT-5.3-Codex leads on speed and interactivity.
The real winner? Developers who now have two incredibly powerful AI coding assistants to choose from.
The AI coding war is just getting started.