Claude Mythos Preview vs Claude Opus 4.8: Specs & Benchmark Comparison
Claude Mythos Preview and Claude Opus 4.8 both come from Anthropic, Claude Mythos Preview was released in April 2026, and Claude Opus 4.8 followed a month later in May 2026.
The two models share 12 published benchmarks. Claude Mythos Preview leads on 11 of them, Claude Opus 4.8 on 1. The widest gaps are on SWE-Bench Multimodal, where Claude Mythos Preview scores 59.0% against 38.4%; Graphwalks BFS >128k, where Claude Mythos Preview scores 80.0% against 68.1%. Averaged across everything we track, Claude Mythos Preview sits at 85.1% and Claude Opus 4.8 at 71.0%.
Claude Opus 4.8 is the cheaper API at $5 per million input tokens and $25 per million output tokens, roughly 5 times cheaper than Claude Mythos Preview at $25 and $125. Both accept text and images as input. On tooling, only Claude Opus 4.8 supports function calling and only Claude Opus 4.8 offers structured output.
| Characteristic | Claude Mythos Preview | Claude Opus 4.8 |
|---|---|---|
| Company | Anthropic | Anthropic |
| Release Date | April 7, 2026 | May 28, 2026 |
| Parameters | — | — |
| Multimodal | Yes | Yes |
| Context (input) | — | 1.0M |
| Context (output) | — | 128K |
| Input Price / 1M | $25.00 | $5.00 |
| Output Price / 1M | $125.00 | $25.00 |
| Average Score | 85.1% | 71.0% |
| Benchmarks | ||
| SWE-Bench Multimodal | 59.0% | 38.4% |
| Graphwalks BFS >128k | 80.0% | 68.1% |
| SWE-Bench Pro | 77.8% | 69.2% |
| Terminal-Bench 2.0 | 82.0% | 74.6% |
| Humanity's Last Exam | 64.7% | 57.9% |
| SWE-Bench Verified | 93.9% | 88.6% |
| CyberGym | 83.1% | 78.8% |
| OSWorld-Verified | 79.6% | 83.4% |
| CharXiv-R | 93.2% | 89.9% |
| SWE-bench Multilingual | 87.3% | 84.4% |
| BrowseComp | 86.9% | 84.3% |
| GPQA | 94.6% | 93.6% |
Visual Benchmark Comparison
Verdict
Claude Opus 4.8 leads in 2 out of 4 comparison categories.
Both models show comparable average scores: Claude Mythos Preview — 0.9, Claude Opus 4.8 — 0.7.
On SWE-Bench, both models are nearly equal: Claude Mythos Preview — 0.9, Claude Opus 4.8 — 0.9.
Claude Opus 4.8 is 5.0x cheaper: input $5.00/1M vs $25.00/1M tokens.
Claude Opus 4.8 is newer: released 5/28/2026 vs 4/7/2026.
More About These Models
Frequently Asked Questions
Which is better for coding — Claude Mythos Preview or Claude Opus 4.8?
Which model is cheaper — Claude Mythos Preview or Claude Opus 4.8?
Which has a larger context window — Claude Mythos Preview or Claude Opus 4.8?
The Claude Mythos Preview and Claude Opus 4.8 comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the Claude Mythos Preview or Claude Opus 4.8 page. See also the complete list of AI model comparisons.