Grok 4.1 Fast vs Step 3.7 Flash
Grok 4.1 Fast (2025) and Step 3.7 Flash (2026) are frontier-tier reasoning models from xAI and StepFun. Grok 4.1 Fast ships a 2m-token context window, while Step 3.7 Flash ships a 256k-token context window. On pricing, both list $0.20/1M input tokens on the cheapest tracked route. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Grok 4.1 Fast fits 8x more tokens; pick it for long-context work and Step 3.7 Flash for tighter calls.
Decision scorecard
Local evidence first| Signal | Grok 4.1 Fast | Step 3.7 Flash |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | RAG, Agents, and Long context | Coding, RAG, and Agents |
| Context window | 2m | 256k |
| Cheapest output | $0.50/1M tokens | $1.15/1M tokens |
| Provider routes | 2 tracked | 3 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Grok 4.1 Fast has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Grok 4.1 Fast has the lower cheapest tracked output price at $0.50/1M tokens.
- Local decision data tags Grok 4.1 Fast for RAG, Agents, and Long context.
- Step 3.7 Flash has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Step 3.7 Flash for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Grok 4.1 Fast
$285
Cheapest tracked route/tier: OpenRouter
Step 3.7 Flash
$448
Cheapest tracked route/tier: StepFun
Estimated monthly gap: $163. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Step 3.7 Flash is $0.65/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Grok 4.1 Fast is $0.65/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-11-19 | 2026-05-29 |
| Context window | 2m | 256k |
| Parameters | — | 198B (11B active) |
| Architecture | - | mixture of experts |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use with conditions | Commercial use with conditions |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | Grok 4.1 Fast | Step 3.7 Flash |
|---|---|---|
| Input price | $0.20/1M tokens | $0.20/1M tokens |
| Output price | $0.50/1M tokens | $1.15/1M tokens |
| Providers |
Capabilities
| Capability | Grok 4.1 Fast | Step 3.7 Flash |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
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, Grok 4.1 Fast lists $0.20/1M input and $0.50/1M output tokens on the cheapest tracked provider, while Step 3.7 Flash lists $0.20/1M input and $1.15/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Grok 4.1 Fast lower by about $0.20 per million blended tokens. Availability is 2 providers versus 3, so concentration risk also matters.
Choose Grok 4.1 Fast when long-context analysis and larger context windows are central to the workload. Choose Step 3.7 Flash when vision-heavy evaluation 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, Grok 4.1 Fast or Step 3.7 Flash?
Grok 4.1 Fast supports 2m tokens, while Step 3.7 Flash 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, Grok 4.1 Fast or Step 3.7 Flash?
Grok 4.1 Fast is cheaper on tracked token pricing. Grok 4.1 Fast costs $0.20/1M input and $0.50/1M output tokens. Step 3.7 Flash costs $0.20/1M input and $1.15/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Grok 4.1 Fast or Step 3.7 Flash open source?
Grok 4.1 Fast is listed under Proprietary. Step 3.7 Flash 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, Grok 4.1 Fast or Step 3.7 Flash?
Both Grok 4.1 Fast and Step 3.7 Flash 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, Grok 4.1 Fast or Step 3.7 Flash?
Both Grok 4.1 Fast and Step 3.7 Flash 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 Grok 4.1 Fast and Step 3.7 Flash?
Grok 4.1 Fast is available on OpenRouter and xAI Console. Step 3.7 Flash is available on StepFun, OpenRouter, and NVIDIA NIM. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-29. Data sourced from public model cards and provider documentation.