Claude Mythos Preview vs Codex (OpenAI)
Which one should you pick? Here's the full breakdown.
Claude Mythos Preview
Anthropic's most capable model -- a gated research preview via Project Glasswing, cybersecurity-specialized. 73% success on expert CTF tasks, 32-step autonomous network attacks. Not generally available.
Codex (OpenAI)
OpenAI's cloud-based coding agent -- runs parallel tasks, proposes PRs, and lives inside ChatGPT
Powered by GPT-5.3-Codex / GPT-5.4
| Category | Claude Mythos Preview | Codex (OpenAI) |
|---|---|---|
| Ease of Use | 2.0 | 8.0 |
| Output Quality | 10.0 | 8.0 |
| Value | 5.0 | 8.0 |
| Features | 9.0 | 9.0 |
| Overall | 6.5 | 8.3 |
Pricing Comparison
| Feature | Claude Mythos Preview | Codex (OpenAI) |
|---|---|---|
| Free Tier | No | Yes |
| Starting Price | Invite only | $0 |
Benchmark Head-to-Head
GPT-5.3-Codex benchmarks — Claude Mythos Preview has no published benchmarks
| Benchmark | Description | Score |
|---|---|---|
| SWE-bench | Real GitHub issue fixing | 72% |
| HumanEval | Python code generation | 95% |
Which Should You Pick?
Pick Claude Mythos Preview if...
- ✓Higher output quality (10 vs 8)
Partner organizations in Project Glasswing doing cybersecurity research, defensive red-teaming, threat intelligence, or large-scale vulnerability triage. If your use case is legitimate cybersecurity and you have enterprise Anthropic contact, ask about Glasswing admission.
Visit Claude Mythos PreviewPick Codex (OpenAI) if...
- ✓Easier to use (8 vs 2)
- ✓Better value for money (8/10)
- ✓Has a free tier
Developers already paying for ChatGPT Plus who want a coding agent at no extra cost. Especially good for parallel task execution -- assign multiple bug fixes or feature branches and let Codex work them simultaneously.
Visit Codex (OpenAI)Our Verdict
Codex (OpenAI) is the clear winner here with 8.3/10 vs 6.5/10. Claude Mythos Preview isn't bad, but Codex (OpenAI) outperforms it across the board. Pick Claude Mythos Preview only if partner organizations in project glasswing doing cybersecurity research, defensive red-teaming, threat intelligence, or large-scale vulnerability triage.