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 · Chat 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 | 78.704 / 18Thinking High (With Tools) | 79.603 / 18Extended (with tools) | -0.90 |
| Terminal Bench 2.0 | 82.701 / 46Thinking High (With Tools) | 822 / 46Extended (with tools) | +0.70 |
General Knowledge
Claude Mythos Preview 2/2| Benchmark | GPT-5.5 | Claude Mythos Preview | Diff |
|---|---|---|---|
| HLE | 52.2013 / 157Thinking High (With Tools) | 64.701 / 157Extended (with tools) | -12.50 |
| GPQA Diamond | 93.606 / 178Thinking High (No Tools) | 94.601 / 178Extended (no tools) | -1 |
AI Agent - Information Search
Claude Mythos Preview 1/1| Benchmark | GPT-5.5 | Claude Mythos Preview | Diff |
|---|---|---|---|
| BrowseComp | 84.405 / 45Thinking High (With Tools + Internet) | 84.904 / 45Extended (with tools) | -0.50 |
Coding and Software Engineer
Claude Mythos Preview 1/1| Benchmark | GPT-5.5 | Claude Mythos Preview | Diff |
|---|---|---|---|
| SWE-Bench Pro - Public | 58.607 / 43Thinking High (With Tools) | 77.802 / 43Extended (with tools) | -19.20 |
Specs
| Field | GPT-5.5 | Claude Mythos Preview |
|---|---|---|
| Publisher | OpenAI | Anthropic |
| Release date | 2026-04-23 | 2026-04-07 |
| Model type | Reasoning model | Chat model |
| Architecture | Dense | Dense |
| Parameters | Not available | Not available |
| Context length | 1000K | Not available |
| Max output | 128K | 8K |
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.