Claude Mythos Preview vs GPT-5.3 Codex
Claude Mythos Preview leads the LLM Stats Score 54.9 to 36.5. GPT-5.3 Codex is 10.4x cheaper per token.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Mythos Preview leads the overall LLM Stats Score 54.9 to 36.5, ranking #4 overall.
In the 3 individual benchmarks reported for both models, Claude Mythos Preview wins 3; this is a narrower head-to-head signal than the composite indexes.
On price, GPT-5.3 Codex is roughly 10.4x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Mythos Preview
- overall performance matters — it scores 54.9 and ranks #4 on LLM Stats
- your work emphasizes reasoning and coding — it leads those capability indexes
- you value its reported benchmark strengths — it wins 3 of 3 exact shared results
Choose GPT-5.3 Codex
- cost matters — it's about 10.4x cheaper per token
At a glance
The differences that matter most.
Individual benchmarks
16 reported for Claude Mythos Preview · 6 for GPT-5.3 Codex
Claude Mythos Preview outperforms in 3 benchmarks (OSWorld-Verified, SWE-Bench Pro, Terminal-Bench 2.0), while GPT-5.3 Codex is better at 0 benchmarks.
Claude Mythos Preview significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Mythos Preview ($25.00/1M tokens) is 14.3x more expensive than GPT-5.3 Codex ($1.75/1M tokens).
For output processing, Claude Mythos Preview ($125.00/1M tokens) is 8.9x more expensive than GPT-5.3 Codex ($14.00/1M tokens).
In conclusion, Claude Mythos Preview is more expensive than GPT-5.3 Codex.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Only GPT-5.3 Codex specifies input context (400,000 tokens). Only GPT-5.3 Codex specifies output context (128,000 tokens).
Input capabilities
Documented input modalities across available providers
Both Claude Mythos Preview and GPT-5.3 Codex support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Mythos Preview
GPT-5.3 Codex
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
GPT-5.3 Codex was released on 2026-02-05, while Claude Mythos Preview's release date is not specified.
We can confirm GPT-5.3 Codex's release timeline, but cannot make a direct age comparison without Claude Mythos Preview's release date.
—
Feb 5, 2026
7 months ago
Knowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
Claude Mythos Preview is available from Anthropic. GPT-5.3 Codex is available from OpenAI.
Claude Mythos Preview
GPT-5.3 Codex
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Mythos Preview and GPT-5.3 Codex side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Mythos Preview vs GPT-5.3 Codex.