Head-to-head comparison
Claude Mythos 5.1 vs. GPT-5.4
Compare published benchmark results from matching versions and cohorts, API pricing, and technical specifications. Any documented test setup differences remain visible.
- shared result series
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- distinct benchmarks
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- latest retrieval
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Specifications
General specifications
Release date, availability, context window, architecture, and published parameter counts at a glance. Undisclosed details remain marked as unavailable.
| Attribute | Claude Mythos 5.1 | GPT-5.4 |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Released | Sep 1, 2026 | Mar 2026 |
| Availability | Limited access | Active |
| Model type | Proprietary | Proprietary |
| Parameters | Not published | Not published |
| Architecture | Not published | Not published |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Knowledge cutoff | June 2026 | August 31, 2025 |
| Technical sources | Model | Model |
Pricing
API pricing compared
The table compares official standard API rates per 1M tokens, including published cache pricing. Batch, fast, priority, regional surcharges, tool calls, and cloud platform pricing are excluded.
| Price type | Claude Mythos 5.1 | GPT-5.4 |
|---|---|---|
| API input | $10 | $2.5 ≤272K / $5 >272K |
| API output | $50 | $15 ≤272K / $22.5 >272K |
| Cache read | $0.25 | $0.25 ≤272K / $0.5 >272K |
| Cache write (5 min.) | $12.5 | Not listed |
| Cache write (1 hr.) | $20 | Not listed |
| Price verified | 09/02/2026 Source | 07/30/2026 Source |
Key to the marks:better valuebetter, but not conclusivetie
Pricing by provider
Direct developer pricing and provider endpoint tariffs routed through OpenRouter are listed separately. Prices are in USD per 1M tokens. Context-dependent direct tiers plus regional, Flex, Priority, and other OpenRouter tariffs remain individually identifiable.
No provider tariff for Claude Mythos 5.1 is available in the stored OpenRouter snapshot. The official direct price is still shown.
| Model | Provider | Purchase route and tariff | Input per 1M tokens | Output per 1M tokens | Source |
|---|---|---|---|---|---|
| Claude Mythos 5.1 | Anthropic | Direct from developerStandard API | Lowest listed price: $10 | Lowest listed price: $50 | Source09/02/2026 |
| GPT-5.4 | OpenAI | Direct from developerUp to 272,000 context tokens | $2.5 | $15 | Source07/30/2026 |
| OpenAI | Direct from developerAbove 272,000 context tokens | $5 | $22.5 | Source07/30/2026 | |
| Amazon Bedrock | Via OpenRouteramazon-bedrock/us-east-1 | $2.75 | $16.5 | Source09/02/2026 | |
| Azure | Via OpenRouterazure | $2.5 | $15 | Source09/02/2026 | |
| Azure | Via OpenRouterazure/eu | $2.75 | $16.5 | Source09/02/2026 | |
| Azure | Via OpenRouterazure/us | $2.75 | $16.5 | Source09/02/2026 | |
| OpenAI | Via OpenRouteropenai | $2.5 | $15 | Source09/02/2026 | |
| OpenAI | Via OpenRouteropenai/fast | $5 | $30 | Source09/02/2026 | |
| OpenAI | Via OpenRouteropenai/flex | Lowest listed price: $1.25 | Lowest listed price: $7.5 | Source09/02/2026 |
Performance
Shared benchmarks
Only published results with the same benchmark version, task, metric, and comparison cohort are paired. Different reasoning levels, agents, harnesses, or output limits appear directly in the table.
Capability profile from matched benchmarks
Each axis averages directly matched benchmark families. A value of 100 means the stronger value within this pair, not a universal quality score.
Not enough directly matched categories for a reliable radar
Only 0 of at least 5 categories have comparable, direct model measurements. The benchmark tables below show the available evidence without filling missing axes.
No directly comparable result series yet
No published benchmark for Claude Mythos 5.1 and GPT-5.4 currently matches in version, task, metric, and comparison cohort. We therefore show no estimated or blended values.
How to read this comparison
Winning one benchmark is not an overall verdict
Your workload, budget, and required context length matter most. A coding benchmark says little about visual understanding or agent performance.
The standard price table uses direct developer rates. The provider comparison labels OpenRouter endpoints, regions, and special tariffs separately.
Every result links to its measurement source and retrieval date. Labels distinguish vendor reports, official benchmark leaderboards, and independent evaluations. Disputed or archived results are excluded.
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