Kimi K2 Turbo Preview vs Step 3.5 Flash
Kimi K2 Turbo Preview (2025) and Step 3.5 Flash (2026) are frontier reasoning models from Moonshot AI and StepFun. Kimi K2 Turbo Preview ships a 262k-token context window, while Step 3.5 Flash ships a 256k-token context window. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
Step 3.5 Flash is safer overall; choose Kimi K2 Turbo Preview when long-context analysis matters.
Decision scorecard
Local evidence first| Signal | Kimi K2 Turbo Preview | Step 3.5 Flash |
|---|---|---|
| Best for | tool-calling agents | reasoning-heavy apps |
| Decision fit | RAG, Agents, and Long context | Long context |
| Context window | 262k | 256k |
| Cheapest output | - | $0.30/1M tokens |
| Provider routes | 0 tracked | 1 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Kimi K2 Turbo Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Kimi K2 Turbo Preview uniquely exposes Function calling in local model data.
- Local decision data tags Kimi K2 Turbo Preview for RAG, Agents, and Long context.
- Step 3.5 Flash has broader tracked provider coverage for fallback and procurement flexibility.
- 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.
Kimi K2 Turbo Preview
Unavailable
No complete token price in local provider data
Step 3.5 Flash
$155
Cheapest tracked route/tier: OpenRouter
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for Kimi K2 Turbo Preview and Step 3.5 Flash; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Function calling 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 Kimi K2 Turbo Preview; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Reasoning before moving production traffic.
- Kimi K2 Turbo Preview adds Function calling in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-08-01 | 2026-01-29 |
| Context window | 262k | 256k |
| Parameters | 1K | 196B (11B active) |
| Architecture | - | mixture of experts |
| License | Proprietary | Open Source |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | Kimi K2 Turbo Preview | Step 3.5 Flash |
|---|---|---|
| Input price | - | $0.10/1M tokens |
| Output price | - | $0.30/1M tokens |
| Providers | - |
Capabilities
| Capability | Kimi K2 Turbo Preview | Step 3.5 Flash |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| Function calling | Yes | No |
| Tool use | No | No |
| Structured outputs | No | 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 function calling: Kimi K2 Turbo Preview. 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.
Pricing coverage is uneven: Kimi K2 Turbo Preview has no token price sourced yet and Step 3.5 Flash has $0.10/1M input tokens. Provider availability is 0 tracked routes versus 1. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose Kimi K2 Turbo Preview when long-context analysis and larger context windows are central to the workload. Choose Step 3.5 Flash when reasoning depth and broader provider choice 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, Kimi K2 Turbo Preview or Step 3.5 Flash?
Kimi K2 Turbo Preview supports 262k tokens, while Step 3.5 Flash supports 256k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Is Kimi K2 Turbo Preview or Step 3.5 Flash open source?
Kimi K2 Turbo Preview 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, Kimi K2 Turbo Preview 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 function calling, Kimi K2 Turbo Preview or Step 3.5 Flash?
Kimi K2 Turbo Preview has the clearer documented function calling signal in this comparison. If function calling is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Kimi K2 Turbo Preview and Step 3.5 Flash?
Kimi K2 Turbo Preview is available on the tracked providers still being sourced. Step 3.5 Flash is available on OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
When should I pick Kimi K2 Turbo Preview over Step 3.5 Flash?
Step 3.5 Flash is safer overall; choose Kimi K2 Turbo Preview when long-context analysis matters. If your workload also depends on long-context analysis, start with Kimi K2 Turbo Preview; if it depends on reasoning depth, run the same evaluation with Step 3.5 Flash.
Continue comparing
Last reviewed: 2026-05-29. Data sourced from public model cards and provider documentation.