Claude 3.5 Sonnet v2 vs Step 3.7 Flash
Claude 3.5 Sonnet v2 (2025) and Step 3.7 Flash (2026) are frontier reasoning models from Anthropic and StepFun. Claude 3.5 Sonnet v2 ships a 200k-token context window, while Step 3.7 Flash ships a 256k-token context window. On pricing, Step 3.7 Flash costs $0.20/1M input tokens versus $6/1M 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.
Step 3.7 Flash is ~2900% cheaper at $0.20/1M; pay for Claude 3.5 Sonnet v2 only for vision-heavy evaluation.
Decision scorecard
Local evidence first| Signal | Claude 3.5 Sonnet v2 | Step 3.7 Flash |
|---|---|---|
| Best for | multimodal apps and provider-routed production | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | RAG, Long context, and Vision | Coding, RAG, and Agents |
| Context window | 200k | 256k |
| Cheapest output | $30/1M tokens | $1.15/1M tokens |
| Provider routes | 2 tracked | 3 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- Local decision data tags Claude 3.5 Sonnet v2 for RAG, Long context, and Vision.
- Step 3.7 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Step 3.7 Flash has the lower cheapest tracked output price at $1.15/1M tokens.
- Step 3.7 Flash has broader tracked provider coverage for fallback and procurement flexibility.
- Step 3.7 Flash uniquely exposes Reasoning, Function calling, and Tool use in local model data.
- 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.
Claude 3.5 Sonnet v2
$12,300
Cheapest tracked route/tier: AWS Bedrock
Step 3.7 Flash
$448
Cheapest tracked route/tier: StepFun
Estimated monthly gap: $11,853. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Claude 3.5 Sonnet v2 and Step 3.7 Flash; plan for SDK, billing, or endpoint changes.
- Step 3.7 Flash is $28.85/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Step 3.7 Flash adds Reasoning, Function calling, and Tool use in local capability data.
- No overlapping tracked provider route is sourced for Step 3.7 Flash and Claude 3.5 Sonnet v2; plan for SDK, billing, or endpoint changes.
- Claude 3.5 Sonnet v2 is $28.85/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning, Function calling, and Tool use before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-12-01 | 2026-05-29 |
| Context window | 200k | 256k |
| Parameters | — | 198B (11B active) |
| Architecture | - | Mixture of Experts |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2024-04 | - |
Pricing and availability
| Pricing attribute | Claude 3.5 Sonnet v2 | Step 3.7 Flash |
|---|---|---|
| Input price | $6/1M tokens | $0.20/1M tokens |
| Output price | $30/1M tokens | $1.15/1M tokens |
| Providers |
Capabilities
| Capability | Claude 3.5 Sonnet v2 | Step 3.7 Flash |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | Yes |
| Function calling | No | Yes |
| Tool use | No | 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 scores are currently available for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Step 3.7 Flash, function calling: Step 3.7 Flash, and tool use: Step 3.7 Flash. Both models share vision, multimodal input, and structured outputs, 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 3.5 Sonnet v2 lists $6/1M input and $30/1M 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 Step 3.7 Flash lower by about $12.71 per million blended tokens. Availability is 2 providers versus 3, so concentration risk also matters.
Choose Claude 3.5 Sonnet v2 when vision-heavy evaluation are central to the workload. Choose Step 3.7 Flash when reasoning depth, larger context windows, 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, Claude 3.5 Sonnet v2 or Step 3.7 Flash?
Step 3.7 Flash supports 256k tokens, while Claude 3.5 Sonnet v2 supports 200k 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 3.5 Sonnet v2 or Step 3.7 Flash?
Step 3.7 Flash is cheaper on tracked token pricing. Claude 3.5 Sonnet v2 costs $6/1M input and $30/1M 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 Claude 3.5 Sonnet v2 or Step 3.7 Flash open source?
Claude 3.5 Sonnet v2 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, Claude 3.5 Sonnet v2 or Step 3.7 Flash?
Both Claude 3.5 Sonnet v2 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, Claude 3.5 Sonnet v2 or Step 3.7 Flash?
Both Claude 3.5 Sonnet v2 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 Claude 3.5 Sonnet v2 and Step 3.7 Flash?
Claude 3.5 Sonnet v2 is available on AWS Bedrock and Anthropic. 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: 2026-06-29. Data sourced from public model cards and provider documentation.