Claude Mythos Preview vs Claude Sonnet 4.5
Claude Mythos Preview (2026) and Claude Sonnet 4.5 (2025) are frontier-tier reasoning models from Anthropic. Claude Mythos Preview ships a 1M-token context window, while Claude Sonnet 4.5 ships a 200K-token context window. On pricing, Claude Sonnet 4.5 costs $3/1M input tokens versus $25/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
Claude Sonnet 4.5 is ~733% cheaper at $3/1M; pay for Claude Mythos Preview only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Mythos Preview | Claude Sonnet 4.5 |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | RAG, Agents, and Long context |
| Context window | 1M | 200K |
| Cheapest output | $125/1M tokens | $15/1M tokens |
| Provider routes | 2 tracked | 7 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Claude Mythos Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Claude Mythos Preview uniquely exposes Code execution in local model data.
- Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
- Claude Sonnet 4.5 has the lower cheapest tracked output price at $15/1M tokens.
- Claude Sonnet 4.5 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Claude Sonnet 4.5 for RAG, Agents, and Long context.
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 Sonnet 4.5
$6,150
Cheapest tracked route: Microsoft Foundry
Estimated monthly gap: $45,100. 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 Sonnet 4.5 is $110/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Code execution before moving production traffic.
- Provider overlap exists on Anthropic and Microsoft Foundry; start route-level A/B tests there.
- Claude Mythos Preview is $110/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Claude Mythos Preview adds Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-07 | 2025-09-29 |
| 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 Sonnet 4.5 |
|---|---|---|
| Input price | $25/1M tokens | $3/1M tokens |
| Output price | $125/1M tokens | $15/1M tokens |
| Providers |
Capabilities
| Capability | Claude Mythos Preview | Claude Sonnet 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 | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on code execution: Claude Mythos Preview. Both models share vision, multimodal input, reasoning mode, and function calling, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Claude Mythos Preview lists $25/1M input and $125/1M output tokens, while Claude Sonnet 4.5 lists $3/1M input and $15/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Claude Sonnet 4.5 lower by about $48.40 per million blended tokens. Availability is 2 providers versus 7, so concentration risk also matters.
Choose Claude Mythos Preview when coding workflow support and larger context windows are central to the workload. Choose Claude Sonnet 4.5 when vision-heavy evaluation, 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. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, Claude Mythos Preview or Claude Sonnet 4.5?
Claude Mythos Preview supports 1M tokens, while Claude Sonnet 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 Sonnet 4.5?
Claude Sonnet 4.5 is cheaper on tracked token pricing. Claude Mythos Preview costs $25/1M input and $125/1M output tokens. Claude Sonnet 4.5 costs $3/1M input and $15/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Claude Mythos Preview or Claude Sonnet 4.5 open source?
Claude Mythos Preview is listed under Proprietary. Claude Sonnet 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 Sonnet 4.5?
Both Claude Mythos Preview and Claude Sonnet 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 Sonnet 4.5?
Both Claude Mythos Preview and Claude Sonnet 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 Sonnet 4.5?
Claude Mythos Preview is available on Anthropic and Microsoft Foundry. Claude Sonnet 4.5 is available on Microsoft Foundry, Anthropic, Snowflake Cortex, GCP Vertex AI, and AWS Bedrock. 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.