Grok Code Fast 1 vs Step 3.5 Flash
Grok Code Fast 1 (2025) and Step 3.5 Flash (2026) compare a coding-specialized model against a standalone API model. Grok Code Fast 1 ships a 262k-token context window, while Step 3.5 Flash ships a 256k-token context window. On SWE-bench Verified, Step 3.5 Flash leads by 3.6 pts. On pricing, Step 3.5 Flash costs $0.10/1M input tokens versus $0.20/1M for the alternative. This page treats the result as workflow and deployment fit, not a universal model winner.
Treat this as a product-type comparison: Grok Code Fast 1 is coding-specialized model, while Step 3.5 Flash is standalone API model. Choose based on workflow fit before reading any benchmark or price row as decisive.
Decision scorecard
Local evidence first| Signal | Grok Code Fast 1 | Step 3.5 Flash |
|---|---|---|
| Product type | Coding-specialized model | Standalone API model |
| Best for | custom coding agents, code generation, and tool loops | reasoning-heavy apps |
| Decision fit | Coding, RAG, and Agents | Coding, Agents, and Long context |
| Context window | 262k | 256k |
| Cheapest output | $1.50/1M tokens | $0.30/1M tokens |
| Provider routes | 3 tracked | 1 tracked |
| Shared benchmarks | 1 rows | SWE-bench Verified leader |
Decision tradeoffs
- Grok Code Fast 1 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Grok Code Fast 1 has broader tracked provider coverage for fallback and procurement flexibility.
- Grok Code Fast 1 uniquely exposes Function calling, Tool use, and Structured outputs in local model data.
- Local decision data tags Grok Code Fast 1 for Coding, RAG, and Agents.
- Step 3.5 Flash holds a shared-benchmark lead on SWE-bench Verified, ahead by 3.6 points.
- Step 3.5 Flash has the lower cheapest tracked output price at $0.30/1M tokens.
- Step 3.5 Flash uniquely exposes Reasoning in local model data.
- Local decision data tags Step 3.5 Flash for Coding, Agents, and Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Grok Code Fast 1
$535
Cheapest tracked route/tier: OpenRouter
Step 3.5 Flash
$155
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $380. 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 3.5 Flash is $1.20/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Function calling, Tool use, and Structured outputs before moving production traffic.
- Step 3.5 Flash adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Grok Code Fast 1 is $1.20/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning before moving production traffic.
- Grok Code Fast 1 adds Function calling, Tool use, and Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| 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 | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use with conditions | Commercial use with conditions |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | Grok Code Fast 1 | Step 3.5 Flash |
|---|---|---|
| Input price | $0.20/1M tokens | $0.10/1M tokens |
| Output price | $1.50/1M tokens | $0.30/1M tokens |
| Providers |
Capabilities
| Capability | Grok Code Fast 1 | Step 3.5 Flash |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| Function calling | Yes | No |
| Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Grok Code Fast 1 | Step 3.5 Flash |
|---|---|---|
| SWE-bench Verified | 70.8 | 74.4 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has Grok Code Fast 1 at 70.8 and Step 3.5 Flash at 74.4, with Step 3.5 Flash ahead by 3.6 points. The largest visible gap is 3.6 points on SWE-bench Verified, 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 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 $0.20/1M input and $1.50/1M output tokens on the cheapest tracked provider, while Step 3.5 Flash lists $0.10/1M input and $0.30/1M 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 3 providers versus 1, so concentration risk also matters.
Choose Grok Code Fast 1 when coding workflow support, larger context windows, and broader provider choice 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.
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 $0.20/1M input and $1.50/1M output tokens. Step 3.5 Flash costs $0.10/1M input and $0.30/1M 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 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 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, Microsoft Foundry, and xAI Console. Step 3.5 Flash is available on OpenRouter. 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.