Claude Sonnet 4.6 vs Step 3.5 Flash
Claude Sonnet 4.6 (2026) and Step 3.5 Flash (2026) are frontier-tier reasoning models from Anthropic and StepFun. Claude Sonnet 4.6 ships a 1m-token context window, while Step 3.5 Flash ships a 256k-token context window. On SWE-bench Verified, Claude Sonnet 4.6 leads by 5.2 pts. On pricing, Step 3.5 Flash costs $0.10/1M input tokens versus $3/1M 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 3.5 Flash is ~2900% cheaper at $0.10/1M; pay for Claude Sonnet 4.6 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Sonnet 4.6 | Step 3.5 Flash |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps |
| Decision fit | Coding, RAG, and Agents | Coding, Agents, and Long context |
| Context window | 1m | 256k |
| Cheapest output | $15/1M tokens | $0.30/1M tokens |
| Provider routes | 6 tracked | 1 tracked |
| Shared benchmarks | SWE-bench Verified leader | 3 shared |
Decision tradeoffs
- Claude Sonnet 4.6 holds a shared-benchmark lead on SWE-bench Verified, ahead by 5.2 points.
- Claude Sonnet 4.6 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Claude Sonnet 4.6 has broader tracked provider coverage for fallback and route flexibility.
- Claude Sonnet 4.6 uniquely exposes Vision, Multimodal, and JSON / Tool use in local model data.
- Local decision data tags Claude Sonnet 4.6 for Coding, RAG, and Agents.
- Step 3.5 Flash holds a shared-benchmark lead on AIME 2025, ahead by 3.3 points.
- Step 3.5 Flash has the lower cheapest tracked output price at $0.30/1M tokens.
- 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.
Claude Sonnet 4.6
$6,150
Cheapest tracked route/tier: OpenRouter
Step 3.5 Flash
$155
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $5,995. 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 $14.70/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision, Multimodal, and JSON / Tool use before moving production traffic.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Claude Sonnet 4.6 is $14.70/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Claude Sonnet 4.6 adds Vision, Multimodal, and JSON / Tool use in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-17 | 2026-01-29 |
| Context window | 1m | 256k |
| Parameters | — | 196B (11B active) |
| Architecture | Decoder Only | 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 | 2025-08 | - |
Pricing and availability
| Pricing attribute | Claude Sonnet 4.6 | Step 3.5 Flash |
|---|---|---|
| Input price | $3/1M tokens | $0.10/1M tokens |
| Output price | $15/1M tokens | $0.30/1M tokens |
| Providers |
Capabilities
| Capability | Claude Sonnet 4.6 | Step 3.5 Flash |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | Yes |
| JSON / Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | Yes | No |
| Parallel agents | Yes | No |
Benchmarks
| Benchmark | Claude Sonnet 4.6 | Step 3.5 Flash |
|---|---|---|
| SWE-bench Verified | 79.6 | 74.4 |
| AIME 2025 | 94.0 | 97.3 |
| LiveCodeBench | 80.0 | 86.4 |
Continue comparing
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- Claude Sonnet 4.6 vs DeepSeek V4 Flash
- Claude Sonnet 4.6 vs DeepSeek V4 Pro
- Claude Sonnet 4.6 vs Kimi K2.6
- Claude Sonnet 4.6 vs Composer 2.5
- Claude Sonnet 4.6 vs GPT-5.5 Pro
- Claude Sonnet 4.6 vs Gemini 3.5 Flash
- Claude Sonnet 4.6 vs GLM-5.1
Popular comparisons for Claude Sonnet 4.6
Popular comparisons for Step 3.5 Flash
Last reviewed: 2026-07-26. Data sourced from public model cards and provider documentation.