Grok Code Fast 1 vs Step 3.5 Flash
Grok Code Fast 1 (2025) and Step 3.5 Flash (2026) are agentic coding models from xAI and StepFun. Grok Code Fast 1 ships a 262K-token context window, while Step 3.5 Flash ships a 256K-token context window. On pricing, Step 3.5 Flash costs $0.1/1M input tokens versus $0.2/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Step 3.5 Flash is ~100% cheaper at $0.1/1M; pay for Grok Code Fast 1 only for coding workflow support.
Specs
| Released | 2025-08-27 | 2026-01-29 |
| Context window | 262K | 256K |
| Parameters | 314B | 196B (11B active) |
| Architecture | mixture of experts | mixture of experts |
| License | Proprietary | Open Source |
| Knowledge cutoff | - | - |
Pricing and availability
| Grok Code Fast 1 | Step 3.5 Flash | |
|---|---|---|
| Input price | $0.2/1M tokens | $0.1/1M tokens |
| Output price | $1.5/1M tokens | $0.3/1M tokens |
| Providers |
Capabilities
| Grok Code Fast 1 | Step 3.5 Flash | |
|---|---|---|
| Vision | ||
| Multimodal | ||
| Reasoning | ||
| Function calling | ||
| Tool use | ||
| Structured outputs | ||
| Code execution |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Step 3.5 Flash, function calling: Grok Code Fast 1, tool use: Grok Code Fast 1, and structured outputs: Grok Code Fast 1. Both models share the core language-model surface, 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, Grok Code Fast 1 lists $0.2/1M input and $1.5/1M output tokens, while Step 3.5 Flash lists $0.1/1M input and $0.3/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Step 3.5 Flash lower by about $0.43 per million blended tokens. Availability is 1 providers versus 1, so concentration risk also matters.
Choose Grok Code Fast 1 when coding workflow support and larger context windows are central to the workload. Choose Step 3.5 Flash when reasoning depth and lower input-token cost 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.
FAQ
Which has a larger context window, Grok Code Fast 1 or Step 3.5 Flash?
Grok Code Fast 1 supports 262K tokens, while Step 3.5 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 Code Fast 1 or Step 3.5 Flash?
Step 3.5 Flash is cheaper on tracked token pricing. Grok Code Fast 1 costs $0.2/1M input and $1.5/1M output tokens. Step 3.5 Flash costs $0.1/1M input and $0.3/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Grok Code Fast 1 or Step 3.5 Flash open source?
Grok Code Fast 1 is listed under Proprietary. Step 3.5 Flash is listed under Open Source. 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 reasoning mode, Grok Code Fast 1 or Step 3.5 Flash?
Step 3.5 Flash has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for function calling, Grok Code Fast 1 or Step 3.5 Flash?
Grok Code Fast 1 has the clearer documented function calling signal in this comparison. If function calling is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Grok Code Fast 1 and Step 3.5 Flash?
Grok Code Fast 1 is available on OpenRouter. Step 3.5 Flash is available on OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
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Last reviewed: 2026-04-24. Data sourced from public model cards and provider documentation.