Claude Opus 4.6 vs Grok 4 Fast Reasoning
Claude Opus 4.6 (2026) and Grok 4 Fast Reasoning (2025) are frontier-tier reasoning models from Anthropic and xAI. Claude Opus 4.6 ships a 1m-token context window, while Grok 4 Fast Reasoning ships a 2m-token context window. On pricing, Grok 4 Fast Reasoning costs $1.25/1M input tokens versus $5/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Grok 4 Fast Reasoning is ~300% cheaper at $1.25/1M; pay for Claude Opus 4.6 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Opus 4.6 | Grok 4 Fast Reasoning |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and long-context analysis |
| Decision fit | Coding, RAG, and Agents | Long context and Vision |
| Context window | 1m | 2m |
| Cheapest output | $25/1M tokens | $2.50/1M tokens |
| Provider routes | 6 tracked | 2 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- Claude Opus 4.6 has broader tracked provider coverage for fallback and route flexibility.
- Claude Opus 4.6 uniquely exposes JSON / Tool use, Structured outputs, and Code execution in local model data.
- Local decision data tags Claude Opus 4.6 for Coding, RAG, and Agents.
- Grok 4 Fast Reasoning has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Grok 4 Fast Reasoning has the lower cheapest tracked output price at $2.50/1M tokens.
- Local decision data tags Grok 4 Fast Reasoning for Long context and Vision.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Claude Opus 4.6
$10,250
Cheapest tracked route/tier: Anthropic
Grok 4 Fast Reasoning
$1,625
Cheapest tracked route/tier: xAI Console
Estimated monthly gap: $8,625. 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 Fast Reasoning is $22.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for JSON / Tool use, Structured outputs, and Code execution before moving production traffic.
- Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
- Claude Opus 4.6 is $22.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Claude Opus 4.6 adds JSON / Tool use, Structured outputs, and Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-05 | 2025-09-01 |
| Context window | 1m | 2m |
| Parameters | — | — |
| Architecture | Decoder Only | 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 | - |
Pricing and availability
| Pricing attribute | Claude Opus 4.6 | Grok 4 Fast Reasoning |
|---|---|---|
| Input price | $5/1M tokens | $1.25/1M tokens |
| Output price | $25/1M tokens | $2.50/1M tokens |
| Providers |
Capabilities
| Capability | Claude Opus 4.6 | Grok 4 Fast Reasoning |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| JSON / Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark scores are currently available for this pair.
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Last reviewed: 2026-07-26. Data sourced from public model cards and provider documentation.