Claude Mythos Preview vs Kimi K2.5
Claude Mythos Preview (2026) and Kimi K2.5 (2026) are agentic coding models from Anthropic and Moonshot AI. Claude Mythos Preview ships a 1M-token context window, while Kimi K2.5 ships a 256K-token context window. On Google-Proof Q&A, Claude Mythos Preview leads by 6.7 pts. On pricing, Kimi K2.5 costs $0.44/1M input tokens versus $25/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Kimi K2.5 is ~5582% cheaper at $0.44/1M; pay for Claude Mythos Preview only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Mythos Preview | Kimi K2.5 |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 256K |
| Cheapest output | $125/1M tokens | $2/1M tokens |
| Provider routes | 2 tracked | 8 tracked |
| Shared benchmarks | Google-Proof Q&A leader | 2 rows |
Decision tradeoffs
- Claude Mythos Preview leads the largest shared benchmark signal on Google-Proof Q&A by 6.7 points.
- Claude Mythos Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Claude Mythos Preview uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
- Kimi K2.5 has the lower cheapest tracked output price at $2/1M tokens.
- Kimi K2.5 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Kimi K2.5 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
Kimi K2.5
$852
Cheapest tracked route: OpenRouter
Estimated monthly gap: $50,398. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
- Kimi K2.5 is $123/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
- Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
- Claude Mythos Preview is $123/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Claude Mythos Preview adds Vision, Multimodal, and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-07 | 2026-03-15 |
| Context window | 1M | 256K |
| Parameters | — | 1T (MoE, 384 experts) |
| Architecture | decoder only | mixture of experts |
| License | Proprietary | MIT |
| Knowledge cutoff | 2025-12 | - |
Pricing and availability
| Pricing attribute | Claude Mythos Preview | Kimi K2.5 |
|---|---|---|
| Input price | $25/1M tokens | $0.44/1M tokens |
| Output price | $125/1M tokens | $2/1M tokens |
| Providers |
Capabilities
| Capability | Claude Mythos Preview | Kimi K2.5 |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | No |
| Function calling | Yes | Yes |
| Tool use | Yes | No |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
Benchmarks
| Benchmark | Claude Mythos Preview | Kimi K2.5 |
|---|---|---|
| Google-Proof Q&A | 94.6 | 87.9 |
| τ-bench | 89.2 | 74.2 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has Claude Mythos Preview at 94.6 and Kimi K2.5 at 87.9, with Claude Mythos Preview ahead by 6.7 points; τ-bench has Claude Mythos Preview at 89.2 and Kimi K2.5 at 74.2, with Claude Mythos Preview ahead by 15 points. The largest visible gap is 15 points on τ-bench, 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 differs most on vision: Claude Mythos Preview, multimodal input: Claude Mythos Preview, reasoning mode: Claude Mythos Preview, tool use: Claude Mythos Preview, and code execution: Claude Mythos Preview. Both models share function calling and structured outputs, 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 Kimi K2.5 lists $0.44/1M input and $2/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Kimi K2.5 lower by about $54.09 per million blended tokens. Availability is 2 providers versus 8, so concentration risk also matters.
Choose Claude Mythos Preview when coding workflow support and larger context windows are central to the workload. Choose Kimi K2.5 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 Kimi K2.5?
Claude Mythos Preview supports 1M tokens, while Kimi K2.5 supports 256K 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 Kimi K2.5?
Kimi K2.5 is cheaper on tracked token pricing. Claude Mythos Preview costs $25/1M input and $125/1M output tokens. Kimi K2.5 costs $0.44/1M input and $2/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Claude Mythos Preview or Kimi K2.5 open source?
Claude Mythos Preview is listed under Proprietary. Kimi K2.5 is listed under MIT. 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 Kimi K2.5?
Claude Mythos Preview has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for multimodal input, Claude Mythos Preview or Kimi K2.5?
Claude Mythos Preview has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Claude Mythos Preview and Kimi K2.5?
Claude Mythos Preview is available on Anthropic and Microsoft Foundry. Kimi K2.5 is available on Fireworks AI, OpenRouter, Together AI, Fireworks AI, and NVIDIA NIM. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-16. Data sourced from public model cards and provider documentation.