DeepSeek V3 vs Step 3.5 Flash
DeepSeek V3 (2024) and Step 3.5 Flash (2026) are frontier reasoning models from DeepSeek and StepFun. DeepSeek V3 ships a 64k-token context window, while Step 3.5 Flash ships a 256k-token context window. On LiveCodeBench, Step 3.5 Flash leads by 36.8 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 V3 only for already-validated prompts or route constraints.
Decision scorecard
Local evidence first| Signal | DeepSeek V3 | Step 3.5 Flash |
|---|---|---|
| Best for | tool-calling agents and provider-routed production | reasoning-heavy apps |
| Decision fit | Coding, Agents, and Classification | Coding, Agents, and Long context |
| Context window | 64k | 256k |
| Cheapest output | $0.30/1M tokens | $0.30/1M tokens |
| Provider routes | 13 tracked | 1 tracked |
| Shared benchmarks | 1 shared | LiveCodeBench leader |
Decision tradeoffs
- DeepSeek V3 has broader tracked provider coverage for fallback and route flexibility.
- DeepSeek V3 uniquely exposes JSON / Tool use and Structured outputs in local model data.
- Local decision data tags DeepSeek V3 for Coding, Agents, and Classification.
- Step 3.5 Flash holds a shared-benchmark lead on LiveCodeBench, ahead by 36.8 points.
- Step 3.5 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Step 3.5 Flash uniquely exposes Reasoning in local model data.
- 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 V3
$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 JSON / Tool use and Structured outputs before moving production traffic.
- Step 3.5 Flash adds Reasoning in local capability data.
- 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 Reasoning before moving production traffic.
- DeepSeek V3 adds JSON / Tool use and Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2024-12-26 | 2026-01-29 |
| Context window | 64k | 256k |
| Parameters | 671B | 196B (11B active) |
| Architecture | Mixture of Experts | 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 | 2024-04 | - |
Pricing and availability
| Pricing attribute | DeepSeek V3 | 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 V3 | Step 3.5 Flash |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| JSON / Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | DeepSeek V3 | Step 3.5 Flash |
|---|---|---|
| LiveCodeBench | 49.6 | 86.4 |
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.