Claude 3.5 Sonnet v2 vs Step 3.5 Flash
Claude 3.5 Sonnet v2 (2025) and Step 3.5 Flash (2026) are frontier reasoning models from Anthropic and StepFun. Claude 3.5 Sonnet v2 ships a 200k-token context window, while Step 3.5 Flash ships a 256k-token context window. On pricing, Step 3.5 Flash costs $0.10/1M input tokens versus $6/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Step 3.5 Flash is ~5900% cheaper at $0.10/1M; pay for Claude 3.5 Sonnet v2 only for provider fit.
Decision scorecard
Local evidence first| Signal | Claude 3.5 Sonnet v2 | Step 3.5 Flash |
|---|---|---|
| Best for | provider-routed production | reasoning-heavy apps |
| Decision fit | RAG, Long context, and Classification | Long context |
| Context window | 200k | 256k |
| Cheapest output | $30/1M tokens | $0.30/1M tokens |
| Provider routes | 2 tracked | 1 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Claude 3.5 Sonnet v2 has broader tracked provider coverage for fallback and procurement flexibility.
- Claude 3.5 Sonnet v2 uniquely exposes Structured outputs in local model data.
- Local decision data tags Claude 3.5 Sonnet v2 for RAG, Long context, and Classification.
- Step 3.5 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- 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 Long context.
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 3.5 Flash
$155
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $12,145. 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 3.5 Flash; plan for SDK, billing, or endpoint changes.
- Step 3.5 Flash is $29.70/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Structured outputs before moving production traffic.
- Step 3.5 Flash adds Reasoning in local capability data.
- No overlapping tracked provider route is sourced for Step 3.5 Flash and Claude 3.5 Sonnet v2; plan for SDK, billing, or endpoint changes.
- Claude 3.5 Sonnet v2 is $29.70/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning before moving production traffic.
- Claude 3.5 Sonnet v2 adds Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-12-01 | 2026-01-29 |
| Context window | 200k | 256k |
| Parameters | — | 196B (11B active) |
| Architecture | - | mixture of experts |
| License | Proprietary | Open Source |
| Knowledge cutoff | 2024-04 | - |
Pricing and availability
| Pricing attribute | Claude 3.5 Sonnet v2 | Step 3.5 Flash |
|---|---|---|
| Input price | $6/1M tokens | $0.10/1M tokens |
| Output price | $30/1M tokens | $0.30/1M tokens |
| Providers |
Capabilities
| Capability | Claude 3.5 Sonnet v2 | Step 3.5 Flash |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| Function calling | No | No |
| Tool use | No | No |
| Structured outputs | Yes | No |
| 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 differs most on reasoning mode: Step 3.5 Flash and structured outputs: Claude 3.5 Sonnet v2. 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, Claude 3.5 Sonnet v2 lists $6/1M input and $30/1M 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 $13.04 per million blended tokens. Availability is 2 providers versus 1, so concentration risk also matters.
Choose Claude 3.5 Sonnet v2 when provider fit and broader provider choice are central to the workload. Choose Step 3.5 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 3.5 Flash?
Step 3.5 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 3.5 Flash?
Step 3.5 Flash is cheaper on tracked token pricing. Claude 3.5 Sonnet v2 costs $6/1M input and $30/1M 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 Claude 3.5 Sonnet v2 or Step 3.5 Flash open source?
Claude 3.5 Sonnet v2 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, Claude 3.5 Sonnet v2 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 structured outputs, Claude 3.5 Sonnet v2 or Step 3.5 Flash?
Claude 3.5 Sonnet v2 has the clearer documented structured outputs signal in this comparison. If structured outputs is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Claude 3.5 Sonnet v2 and Step 3.5 Flash?
Claude 3.5 Sonnet v2 is available on AWS Bedrock and Anthropic. 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.