Claude Mythos Preview vs Claude Opus 4.5
Claude Mythos Preview (2026) and Claude Opus 4.5 (2025) are frontier-tier reasoning models from Anthropic. Claude Mythos Preview ships a 1M-token context window, while Claude Opus 4.5 ships a 200K-token context window. On SWE-bench Verified, Claude Mythos Preview leads by 13 pts. On pricing, Claude Opus 4.5 costs $5/1M input tokens versus $25/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Claude Opus 4.5 is ~400% cheaper at $5/1M; pay for Claude Mythos Preview only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 200K |
| Cheapest output | $125/1M tokens | $25/1M tokens |
| Provider routes | 2 tracked | 5 tracked |
| Shared benchmarks | SWE-bench Verified leader | 1 rows |
Decision tradeoffs
- Claude Mythos Preview leads the largest shared benchmark signal on SWE-bench Verified by 13 points.
- Claude Mythos Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
- Claude Opus 4.5 has the lower cheapest tracked output price at $25/1M tokens.
- Claude Opus 4.5 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Claude Opus 4.5 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Claude Mythos Preview
$51,250
Cheapest tracked route: Anthropic
Claude Opus 4.5
$10,250
Cheapest tracked route: Microsoft Foundry
Estimated monthly gap: $41,000. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on Microsoft Foundry and Anthropic; start route-level A/B tests there.
- Claude Opus 4.5 is $100/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Provider overlap exists on Anthropic and Microsoft Foundry; start route-level A/B tests there.
- Claude Mythos Preview is $100/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-07 | 2025-11-01 |
| Context window | 1M | 200K |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-12 | 2025-12 |
Pricing and availability
| Pricing attribute | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| Input price | $25/1M tokens | $5/1M tokens |
| Output price | $125/1M tokens | $25/1M tokens |
| Providers |
Capabilities
| Capability | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
Benchmarks
| Benchmark | Claude Mythos Preview | Claude Opus 4.5 |
|---|---|---|
| SWE-bench Verified | 93.9 | 80.9 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has Claude Mythos Preview at 93.9 and Claude Opus 4.5 at 80.9, with Claude Mythos Preview ahead by 13 points. The largest visible gap is 13 points on SWE-bench Verified, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint is close: both models cover vision, multimodal input, reasoning mode, function calling, and tool use. That makes context budget, benchmark fit, and provider maturity more important than a simple checklist. If your application depends on one integration detail, verify it against the provider route you plan to use, not just the base model listing.
For cost, Claude Mythos Preview lists $25/1M input and $125/1M output tokens, while Claude Opus 4.5 lists $5/1M input and $25/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Claude Opus 4.5 lower by about $44 per million blended tokens. Availability is 2 providers versus 5, so concentration risk also matters.
Choose Claude Mythos Preview when coding workflow support and larger context windows are central to the workload. Choose Claude Opus 4.5 when coding workflow support, lower input-token cost, and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Claude Mythos Preview or Claude Opus 4.5?
Claude Mythos Preview supports 1M tokens, while Claude Opus 4.5 supports 200K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Claude Mythos Preview or Claude Opus 4.5?
Claude Opus 4.5 is cheaper on tracked token pricing. Claude Mythos Preview costs $25/1M input and $125/1M output tokens. Claude Opus 4.5 costs $5/1M input and $25/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Claude Mythos Preview or Claude Opus 4.5 open source?
Claude Mythos Preview is listed under Proprietary. Claude Opus 4.5 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Claude Mythos Preview or Claude Opus 4.5?
Both Claude Mythos Preview and Claude Opus 4.5 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, Claude Mythos Preview or Claude Opus 4.5?
Both Claude Mythos Preview and Claude Opus 4.5 expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run Claude Mythos Preview and Claude Opus 4.5?
Claude Mythos Preview is available on Anthropic and Microsoft Foundry. Claude Opus 4.5 is available on Microsoft Foundry, Anthropic, GCP Vertex AI, AWS Bedrock, and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-16. Data sourced from public model cards and provider documentation.