Kimi K3
Overview
Kimi K3 is Moonshot AI's flagship model, announced on July 16, 2026. Available through the API as kimi-k3, it combines a sparse Mixture-of-Experts architecture, native image and video understanding, always-on reasoning, and a 1,048,576-token context window for long-horizon coding, knowledge work, and agentic workflows.
Key Features
- Sparse MoE Architecture: Uses Kimi Delta Attention (KDA), Attention Residuals (AttnRes), and Stable LatentMoE, activating a subset of experts per request for efficient large-scale inference.
- Long-Horizon Agentic Work: Designed to navigate large repositories, coordinate terminal tools, conduct multi-step research, and produce complete software or knowledge-work artifacts with limited supervision.
- Native Visual Understanding: Accepts text, image, and video input and can use visual feedback in frontend engineering, game development, CAD, document analysis, animation, and video-editing workflows.
- 1M Context and Large Outputs: Provides a 1,048,576-token context window with automatic context caching.
max_completion_tokensdefaults to 131,072 and can be configured up to 1,048,576, subject to the combined context limit. - Production API Controls: Supports streaming, function calling,
tool_choice, dynamic tool loading, strict JSON Schema output, Partial Mode, and official Formula tools through an OpenAI-compatible Chat Completions API.
Best Use Cases
- Large-Repository Software Engineering: Long-running implementation, debugging, repository navigation, terminal orchestration, GPU kernel optimization, compiler work, and visually guided frontend or game development.
- End-to-End Knowledge Work: Research, financial and scientific analysis, document synthesis, spreadsheet tasks, presentation creation, and interactive reports that combine evidence, code, and visualizations.
- Multimodal Agent Workflows: Tasks that require text, screenshots, images, video, tools, and iterative visual feedback within the same agent loop.
- Long-Context Applications: Codebase assistants, fixed-corpus analysis, document Q&A, and agents that benefit from a stable repeated prefix and automatic cache hits.
Capabilities and Limitations
| Capability | Description |
|---|---|
| Reasoning | Always uses thinking mode; reasoning_effort currently supports only max. |
| Coding | Suitable for long-running coding, repository navigation, terminal workflows, compiler work, GPU kernel optimization, debugging, and visually guided frontend or game development. |
| Creative Writing | Supports general and long-form text generation. |
| Multimodal | Text, image, and video input with text output. |
| Response Speed | Latency depends on reasoning length, output length, media inputs, and tool use. |
| Context Window | 1,048,576 tokens, with automatic caching for repeated initial context. |
| Max Output | 131,072 tokens by default; configurable up to 1,048,576 tokens, subject to the combined context-window limit. |
| Tool Use | Function calling, tool_choice, dynamic tool loading, structured output, JSON Mode, Partial Mode, and official Formula tools. |
| Multilingual | Supports Chinese and English usage; provider-side language coverage may evolve with the Kimi API. |
Known Limitations
- Kimi K3 currently supports only
reasoning_effort="max";temperature,top_p,n, presence penalty, and frequency penalty are fixed by the API. - Multi-turn and tool-calling requests must return the complete assistant message, including thinking history. Omitting that history or switching to Kimi K3 midway through a session can make output quality unstable.
- Applications with strict boundaries should provide explicit constraints in the system prompt or
AGENTS.md. - Public image URLs are not accepted directly. Images must use base64 or an
ms://file reference, and videos must be uploaded before use. - Built-in web-search support is not listed in the current B.AI pricing table for this model. Check the platform model catalog for the latest runtime availability.
Credits Usage
| Model | Input (Credits/Token) | Cache Write (Credits/Token) | Cache Read (Credits/Token) | Output (Credits/Token) | Web Search (Credits/Use) | Billing Notes |
|---|---|---|---|---|---|---|
| Kimi K3 | 3.00 | 3.00 | 0.30 | 15.00 | - | Cache write is billed at the same rate as input; cache read is billed at 0.1x input |
Pricing note
Prices shown in the documentation are B.AI standard reference prices for base billing purposes. B.AI may provide lower actual usage costs through top-up bonuses and account benefits. Specific prices, bonus Credits, and account benefits are subject to the platform display and final billing records.