Claude Mythos Preview vs Grok 4.3
Claude Mythos Preview (2026) and Grok 4.3 (2026) are frontier-tier reasoning models from Anthropic and xAI. Claude Mythos Preview ships a 1m-token context window, while Grok 4.3 ships a 1m-token context window. On Google-Proof Q&A, Claude Mythos Preview leads by 4.5 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Grok 4.3 is safer overall; choose Claude Mythos Preview when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Claude Mythos Preview | Grok 4.3 |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | RAG, Agents, and Long context |
| Context window | 1m | 1m |
| Cheapest output | $125/1M tokens | $2.50/1M tokens |
| Provider routes | 2 tracked | 5 tracked |
| Shared benchmarks | Google-Proof Q&A leader | 1 shared |
Decision tradeoffs
- Claude Mythos Preview holds a shared-benchmark lead on Google-Proof Q&A, ahead by 4.5 points.
- Claude Mythos Preview uniquely exposes Code execution in local model data.
- Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
- Grok 4.3 has the lower cheapest tracked output price at $2.50/1M tokens.
- Grok 4.3 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Grok 4.3 for RAG, Agents, and Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Claude Mythos Preview
$51,250
Cheapest tracked route/tier: Anthropic
Grok 4.3
$1,625
Cheapest tracked route/tier: xAI Console
Estimated monthly gap: $49,625. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
- Grok 4.3 is $123/1M 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 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 Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-01 | 2026-05-06 |
| Context window | 1m | 1m |
| Parameters | — | ~0.5T |
| Architecture | Decoder Only | - |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-12 | 2024-11 |
Pricing and availability
| Pricing attribute | Claude Mythos Preview | Grok 4.3 |
|---|---|---|
| Input price | $25/1M tokens |
|
| Output price | $125/1M tokens |
|
| Providers |
Capabilities
| Capability | Claude Mythos Preview | Grok 4.3 |
|---|---|---|
| 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 |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Claude Mythos Preview | Grok 4.3 |
|---|---|---|
| Google-Proof Q&A | 94.6 | 90.1 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has Claude Mythos Preview at 94.6 and Grok 4.3 at 90.1, with Claude Mythos Preview ahead by 4.5 points. The largest visible gap is 4.5 points on Google-Proof Q&A, 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 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 on the cheapest tracked provider, while Grok 4.3 lists tiered pricing: 0-200,001t is $1.25/1M input and $2.50/1M output; 200,001t+ is $2.50/1M input and $5/1M output. A 70/30 input-output blend puts Grok 4.3 lower by about $53.38 per million blended tokens. For tiered rows, this cheapest-track view can understate interactive or fast-lane spend, so compare the tier you will actually use. Availability is 2 providers versus 5, so concentration risk also matters.
Choose Claude Mythos Preview when coding workflow support are central to the workload. Choose Grok 4.3 when vision-heavy evaluation, lower cheapest-tier 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 Grok 4.3?
Claude Mythos Preview supports 1m tokens, while Grok 4.3 supports 1m 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 Grok 4.3?
Claude Mythos Preview lists $25/1M input and $125/1M output tokens on the cheapest tracked provider. Grok 4.3 lists tiered pricing: 0-200,001t is $1.25/1M input and $2.50/1M output; 200,001t+ is $2.50/1M input and $5/1M output. Compare the tier you will actually use; cheap async pricing can overstate savings for interactive workflows. Provider discounts or batch pricing can still change the final bill.
Is Claude Mythos Preview or Grok 4.3 open source?
Claude Mythos Preview is listed under Proprietary. Grok 4.3 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 Grok 4.3?
Both Claude Mythos Preview and Grok 4.3 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Claude Mythos Preview or Grok 4.3?
Both Claude Mythos Preview and Grok 4.3 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 Grok 4.3?
Claude Mythos Preview is available on Anthropic and Microsoft Foundry. Grok 4.3 is available on xAI Console, OpenRouter, Microsoft Foundry, Vercel AI Gateway, and AWS Bedrock. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-07-10. Data sourced from public model cards and provider documentation.