GPT-5.5vsClaude Mythos Preview
Across 6 shared benchmarks, Claude Mythos Preview leads overall: GPT-5.5 wins 1, Claude Mythos Preview wins 5, with 0 ties and an average score difference of -5.57.
GPT-5.5
OpenAI · 2026-04-23 · Reasoning model
Claude Mythos Preview
Anthropic · 2026-04-07 · AI model
GPT-5.51 win(17%)(83%)5 winsClaude Mythos Preview
Benchmark scores
Grouped by capability, sorted by largest gap within each. 6 shared benchmarks.
AI Agent - Tool Usage
Even 2/2| Benchmark | GPT-5.5 | Claude Mythos Preview | Diff |
|---|---|---|---|
| OSWorld-Verified | 78.702 / 14Thinking High (With Tools) | 79.601 / 14Extended (with tools) | -0.90 |
| Terminal Bench 2.0 | 82.701 / 43Thinking High (With Tools) | 822 / 43Extended (with tools) | +0.70 |
General Knowledge
Claude Mythos Preview 2/2Specs
| Field | GPT-5.5 | Claude Mythos Preview |
|---|---|---|
| Publisher | OpenAI | Anthropic |
| Release date | 2026-04-23 | 2026-04-07 |
| Model type | Reasoning model | AI model |
| Architecture | Dense | Dense |
| Parameters | 0.0 | 0.0 |
| Context length | 1000K | Not available |
| Max output | 131072 | 8192 |
API pricing
Prices use DataLearner records when available; missing fields are not inferred.
| Item | GPT-5.5 | Claude Mythos Preview |
|---|---|---|
| Text input | $0.5 / 1M tokens | $25 / 1M tokens |
| Text output | $30 / 1M tokens | $125 / 1M tokens |
| Cache read | $0.5 / 1M tokens | Not public |
| Cache write | $6.25 / 1M tokens | Not public |
Summary
- Claude Mythos Previewleads in:General Knowledge (2/2), AI Agent - Information Search (1/1), Coding and Software Engineer (1/1)
- Tied in:AI Agent - Tool Usage
On average across the 6 shared benchmarks, Claude Mythos Preview scores 5.57 higher.
Largest single-benchmark gap: SWE-Bench Pro - Public — GPT-5.5 58.60 vs Claude Mythos Preview 77.80 (-19.20).
Page generated from structured model, pricing and benchmark records. No real-time LLM is used to write the prose.