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meituan/longcat-flash-chat
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LongCat Flash Chat

LongCat-Flash-Chat is a large-scale Mixture-of-Experts (MoE) model with 560B total parameters, of which 18.6B–31.3B (≈27B on average) are dynamically activated per input. It introduces a shortcut-connected MoE design to reduce communication overhead and achieve high throughput while maintaining training stability through advanced scaling strategies such as hyperparameter transfer, deterministic computation, and multi-stage optimization. This release, LongCat-Flash-Chat, is a non-thinking foundation model optimized for conversational and agentic tasks. It supports long context windows up to 128K tokens and shows competitive performance across reasoning, coding, instruction following, and domain benchmarks, with particular strengths in tool use and complex multi-step interactions.

9/9/2025
131,072 tokens
#107 Text (Coding)

Specifications

Modalities

Input
text
Output
text

Supported Parameters

max_tokens
response_format
structured_outputs
temperature
tool_choice
tools
top_p

Max Output Tokens

32,768

Frequently asked questions

Is LongCat Flash Chat available on FastMetal?
Not at the moment. GLM 5.3 Flash, from the same lab, is available on the FastMetal API today.
What is the context window of LongCat Flash Chat?
131,072 tokens, shared between the prompt and the response.
How does LongCat Flash Chat rank?
#149 on the public arena's Japanese board (ELO 1,307). Ranks move as the leaderboard is updated.

Leaderboard

Text
OverallELO: 1,401
#145
JapaneseELO: 1,307
#149
ChineseELO: 1,435
#135
KoreanELO: 1,325
#146
EnglishELO: 1,422
#134
frenchELO: 1,430
#115
germanELO: 1,377
#141
spanishELO: 1,409
#115
russianELO: 1,378
#158
CodingELO: 1,473
#107
MathELO: 1,415
#119
Creative WritingELO: 1,330
#188
Instruction FollowingELO: 1,388
#148
Hard PromptsELO: 1,426
#137
Multi-TurnELO: 1,392
#161