Claude 3.5 Sonnet vs Step 3.7 Flash
Claude 3.5 Sonnet (2024) and Step 3.7 Flash (2026) are frontier-tier reasoning models from Anthropic and StepFun. Claude 3.5 Sonnet 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 $3/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Step 3.7 Flash is ~1400% cheaper at $0.20/1M; pay for Claude 3.5 Sonnet only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude 3.5 Sonnet | 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 | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 200k | 256k |
| Cheapest output | $15/1M tokens | $1.15/1M tokens |
| Provider routes | 6 tracked | 3 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Claude 3.5 Sonnet has broader tracked provider coverage for fallback and procurement flexibility.
- Claude 3.5 Sonnet uniquely exposes Code execution in local model data.
- Local decision data tags Claude 3.5 Sonnet for Coding, RAG, and Agents.
- 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 uniquely exposes 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
$6,150
Cheapest tracked route/tier: GCP Vertex AI
Step 3.7 Flash
$448
Cheapest tracked route/tier: StepFun
Estimated monthly gap: $5,703. 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 $13.85/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Code execution before moving production traffic.
- Step 3.7 Flash adds Tool use in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Claude 3.5 Sonnet is $13.85/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Tool use before moving production traffic.
- Claude 3.5 Sonnet adds Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2024-06-20 | 2026-05-29 |
| Context window | 200k | 256k |
| Parameters | 70B | 198B (11B active) |
| Architecture | decoder only | mixture of experts |
| License | Unknown | Apache 2.0 |
| Knowledge cutoff | 2024-04 | - |
Pricing and availability
| Pricing attribute | Claude 3.5 Sonnet | Step 3.7 Flash |
|---|---|---|
| Input price | $3/1M tokens | $0.20/1M tokens |
| Output price | $15/1M tokens | $1.15/1M tokens |
| Providers |
Capabilities
| Capability | Claude 3.5 Sonnet | Step 3.7 Flash |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | No | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | 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 differs most on tool use: Step 3.7 Flash and code execution: Claude 3.5 Sonnet. Both models share vision, multimodal input, reasoning mode, and function calling, 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 lists $3/1M input and $15/1M 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 $6.11 per million blended tokens. Availability is 6 providers versus 3, so concentration risk also matters.
Choose Claude 3.5 Sonnet when coding workflow support and broader provider choice are central to the workload. Choose Step 3.7 Flash when long-context analysis, 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 or Step 3.7 Flash?
Step 3.7 Flash supports 256k tokens, while Claude 3.5 Sonnet 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 or Step 3.7 Flash?
Step 3.7 Flash is cheaper on tracked token pricing. Claude 3.5 Sonnet costs $3/1M input and $15/1M 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 or Step 3.7 Flash open source?
Claude 3.5 Sonnet is listed under Unknown. Step 3.7 Flash is listed under Apache 2.0. 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 or Step 3.7 Flash?
Both Claude 3.5 Sonnet 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 or Step 3.7 Flash?
Both Claude 3.5 Sonnet 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 and Step 3.7 Flash?
Claude 3.5 Sonnet is available on GCP Vertex AI, AWS Bedrock, Anthropic, OpenRouter, and Microsoft Foundry. 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.