DeepSeek V3.1 Terminus vs Qwen3.5-Plus
DeepSeek V3.1 Terminus (2025) and Qwen3.5-Plus (2026) are general-purpose language models from DeepSeek and Alibaba. DeepSeek V3.1 Terminus ships a 164K-token context window, while Qwen3.5-Plus ships a 1M-token context window. On pricing, DeepSeek V3.1 Terminus costs $0.21/1M input tokens versus $0.4/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
DeepSeek V3.1 Terminus is ~90% cheaper at $0.21/1M; pay for Qwen3.5-Plus only for long-context analysis.
Decision scorecard
Local evidence first| Signal | DeepSeek V3.1 Terminus | Qwen3.5-Plus |
|---|---|---|
| Decision fit | RAG, Long context, and Classification | Long context and Vision |
| Context window | 164K | 1M |
| Cheapest output | $0.79/1M tokens | $2.4/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- DeepSeek V3.1 Terminus has the lower cheapest tracked output price at $0.79/1M tokens.
- DeepSeek V3.1 Terminus uniquely exposes Structured outputs in local model data.
- Local decision data tags DeepSeek V3.1 Terminus for RAG, Long context, and Classification.
- Qwen3.5-Plus has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Qwen3.5-Plus uniquely exposes Multimodal in local model data.
- Local decision data tags Qwen3.5-Plus for Long context and Vision.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
DeepSeek V3.1 Terminus
$366
Cheapest tracked route: OpenRouter
Qwen3.5-Plus
$920
Cheapest tracked route: Alibaba Cloud PAI-EAS
Estimated monthly gap: $555. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Qwen3.5-Plus is $1.61/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Structured outputs before moving production traffic.
- Qwen3.5-Plus adds Multimodal in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- DeepSeek V3.1 Terminus is $1.61/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Multimodal before moving production traffic.
- DeepSeek V3.1 Terminus adds Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-04-01 | 2026-02-15 |
| Context window | 164K | 1M |
| Parameters | — | — |
| Architecture | decoder only | - |
| License | Open Source | Proprietary |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | DeepSeek V3.1 Terminus | Qwen3.5-Plus |
|---|---|---|
| Input price | $0.21/1M tokens | $0.4/1M tokens |
| Output price | $0.79/1M tokens | $2.4/1M tokens |
| Providers |
Capabilities
| Capability | DeepSeek V3.1 Terminus | Qwen3.5-Plus |
|---|---|---|
| Vision | No | No |
| Multimodal | No | Yes |
| Reasoning | No | No |
| Function calling | No | No |
| Tool use | No | No |
| Structured outputs | Yes | No |
| Code execution | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on multimodal input: Qwen3.5-Plus and structured outputs: DeepSeek V3.1 Terminus. 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, DeepSeek V3.1 Terminus lists $0.21/1M input and $0.79/1M output tokens, while Qwen3.5-Plus lists $0.4/1M input and $2.4/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts DeepSeek V3.1 Terminus lower by about $0.62 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose DeepSeek V3.1 Terminus when provider fit and lower input-token cost are central to the workload. Choose Qwen3.5-Plus when long-context analysis and larger context windows 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. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, DeepSeek V3.1 Terminus or Qwen3.5-Plus?
Qwen3.5-Plus supports 1M tokens, while DeepSeek V3.1 Terminus supports 164K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, DeepSeek V3.1 Terminus or Qwen3.5-Plus?
DeepSeek V3.1 Terminus is cheaper on tracked token pricing. DeepSeek V3.1 Terminus costs $0.21/1M input and $0.79/1M output tokens. Qwen3.5-Plus costs $0.4/1M input and $2.4/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is DeepSeek V3.1 Terminus or Qwen3.5-Plus open source?
DeepSeek V3.1 Terminus is listed under Open Source. Qwen3.5-Plus is listed under Proprietary. 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 multimodal input, DeepSeek V3.1 Terminus or Qwen3.5-Plus?
Qwen3.5-Plus has the clearer documented multimodal input signal in this comparison. If multimodal input 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, DeepSeek V3.1 Terminus or Qwen3.5-Plus?
DeepSeek V3.1 Terminus 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 DeepSeek V3.1 Terminus and Qwen3.5-Plus?
DeepSeek V3.1 Terminus is available on NVIDIA NIM and OpenRouter. Qwen3.5-Plus is available on Alibaba Cloud PAI-EAS and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-11. Data sourced from public model cards and provider documentation.