Model comparison
Claude Mythos 5 vs GPT-5.5 Pro
Head-to-head evidence from 3 shared benchmark results across 2 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Mythos 5 #2 (Supported); GPT-5.5 Pro #41 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Mythos 5 and GPT-5.5 Pro share 3 comparable benchmark results. 3 of 8 categories are comparable. 12 results are unique to Claude Mythos 5; 4 to GPT-5.5 Pro.
Updated July 24, 2026- Shared results
- 3
- Claude Mythos 5 only
- 12
- GPT-5.5 Pro only
- 4
- Comparable categories
- 3 / 8
Pick Claude Mythos 5 if you want the stronger benchmark profile. GPT-5.5 Pro only becomes the better choice if agentic is the priority.
Confidence note. This is a partial-evidence comparison with 3 shared benchmark results across 2 evidence categories; 3 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
Claude Mythos 5 is clearly ahead on the BenchAlign aggregate, 83.01 to 62.83. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Mythos 5's sharpest advantage is in mathematics, where it averages 97.6 against 48.1. The single biggest benchmark swing on the page is HLE, 64.5% to 57.2%. GPT-5.5 Pro does hit back in agentic, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $10.00 input / $50.00 output per 1M tokens for Claude Mythos 5. That is roughly 3.6x on output cost alone. Claude Mythos 5 gives you the larger context window at 1M+, compared with 1M for GPT-5.5 Pro.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | Claude Mythos 5 | Δ | GPT-5.5 Pro |
|---|---|---|---|
| Math | Claude Mythos 597.6 | Margin← 49.5 | GPT-5.5 Pro48.1 |
| Knowledge | Claude Mythos 568.5 | Margin← 11.3 | GPT-5.5 Pro57.2 |
| Agentic | Claude Mythos 587.0 | Margin→ 3.1 | GPT-5.5 Pro90.1 |
| Coding | Claude Mythos 589.7 | MarginNo overlap | GPT-5.5 ProNot measured |
| Multimodal | Claude Mythos 593.5 | MarginNo overlap | GPT-5.5 ProNot measured |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
HLE
KnowledgeA 64.5%B 57.2%Winner: Claude Mythos 5Δ 7.3HLE: Claude Mythos 5 scored 64.5%; GPT-5.5 Pro scored 57.2%. Claude Mythos 5 wins this benchmark. - Source ↗
BrowseComp
AgenticA 88%B 90.1%Winner: GPT-5.5 ProΔ 2.1BrowseComp: Claude Mythos 5 scored 88%; GPT-5.5 Pro scored 90.1%. GPT-5.5 Pro wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Mythos 5 | GPT-5.5 Pro | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Mythos 5$10 input / $50 output | GPT-5.5 Pro$30 input / $180 output | Claude Mythos 5 has the lower combined listed price. |
| Generation speedtokens per second | Claude Mythos 5Not available | GPT-5.5 ProNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Mythos 5Not available | GPT-5.5 ProNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Mythos 51M+ | GPT-5.5 Pro1M | Claude Mythos 5 lists the larger context window. |
Benchmark Deep Dive
AgenticGPT-5.5 Pro wins4 benchmarks
Coding3 benchmarks
Reasoning1 benchmarks
| Benchmark | Claude Mythos 5 | GPT-5.5 Pro | Result |
|---|---|---|---|
| CritPtSource | — | 30.6% | Not comparable |
KnowledgeClaude Mythos 5 wins3 benchmarks
MathClaude Mythos 5 wins4 benchmarks
Multilingual1 benchmarks
| Benchmark | Claude Mythos 5 | GPT-5.5 Pro | Result |
|---|---|---|---|
| SWE MultilingualSource | 92.2% | — | Not comparable |
Frequently Asked Questions (4)
Which is better, Claude Mythos 5 or GPT-5.5 Pro?
Claude Mythos 5 is ahead on BenchLM's BenchAlign leaderboard, 83.01 to 62.83. The biggest single separator in this matchup is HLE, where the scores are 64.5% and 57.2%.
Which is better for knowledge tasks, Claude Mythos 5 or GPT-5.5 Pro?
Claude Mythos 5 has the edge for knowledge tasks in this comparison, averaging 68.5 versus 57.2. Inside this category, HLE w/o tools is the benchmark that creates the most daylight between them.
Which is better for math, Claude Mythos 5 or GPT-5.5 Pro?
Claude Mythos 5 has the edge for math in this comparison, averaging 97.6 versus 48.1. GPT-5.5 Pro stays close enough that the answer can still flip depending on your workload.
Which is better for agentic tasks, Claude Mythos 5 or GPT-5.5 Pro?
GPT-5.5 Pro has the edge for agentic tasks in this comparison, averaging 90.1 versus 87. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.