DeepSeek R1 vs Step 3.5 Flash
DeepSeek R1 (2025) and Step 3.5 Flash (2026) are frontier-tier reasoning models from DeepSeek and StepFun. DeepSeek R1 ships a 128k-token context window, while Step 3.5 Flash ships a 256k-token context window. On SWE-bench Verified, Step 3.5 Flash leads by 25.2 pts. On pricing, both list $0.10/1M input and $0.30/1M output tokens on the cheapest tracked route. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Pick Step 3.5 Flash for coding; token pricing is tied, so keep DeepSeek R1 only for already-validated prompts or route constraints.
Decision scorecard
Local evidence first| Signal | DeepSeek R1 | Step 3.5 Flash |
|---|---|---|
| Best for | reasoning-heavy apps and provider-routed production | reasoning-heavy apps |
| Decision fit | Coding, RAG, and Agents | Coding, Agents, and Long context |
| Context window | 128k | 256k |
| Cheapest output | $0.30/1M tokens | $0.30/1M tokens |
| Provider routes | 14 tracked | 1 tracked |
| Shared benchmarks | 1 shared | SWE-bench Verified leader |
Decision tradeoffs
- DeepSeek R1 has broader tracked provider coverage for fallback and route flexibility.
- DeepSeek R1 uniquely exposes Structured outputs and Code execution in local model data.
- Local decision data tags DeepSeek R1 for Coding, RAG, and Agents.
- Step 3.5 Flash holds a shared-benchmark lead on SWE-bench Verified, ahead by 25.2 points.
- Step 3.5 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- 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.
DeepSeek R1
$155
Cheapest tracked route/tier: Bitdeer AI
Step 3.5 Flash
$155
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $0.00. 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.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- Check replacement coverage for Structured outputs and Code execution before moving production traffic.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- DeepSeek R1 adds Structured outputs and Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-01-20 | 2026-01-29 |
| Context window | 128k | 256k |
| Parameters | 671B, 37B Active | 196B (11B active) |
| Architecture | Decoder Only | Mixture of Experts |
| License | MITOSI-approved | Proprietary |
| Openness | Open source | Proprietary |
| Weights | Available | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: permitted | Commercial use: conditional |
| Knowledge cutoff | 2023-12 | - |
Pricing and availability
| Pricing attribute | DeepSeek R1 | Step 3.5 Flash |
|---|---|---|
| Input price | $0.10/1M tokens | $0.10/1M tokens |
| Output price | $0.30/1M tokens | $0.30/1M tokens |
| Providers |
Capabilities
| Capability | DeepSeek R1 | Step 3.5 Flash |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | Yes | Yes |
| JSON / Tool use | No | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | DeepSeek R1 | Step 3.5 Flash |
|---|---|---|
| SWE-bench Verified | 49.2 | 74.4 |
Continue comparing
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.