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Kimi K3.1 Pro

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MoonshotAIReleased Oct 23, 2026moonshotai/kimi-k3.1-pro
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Kimi K3.1 Pro is Moonshot AI's flagship open-weight multimodal reasoning model and the first in the K3.1 series, a post-trained version of Kimi K3 with substantially more post-training compute, built on the same Kimi Delta Attention and Attention Residuals architecture (K3: 2.8T total, 104B active parameters; Moonshot calls K3.1 Pro 3T-class). It has a 1M-token context window with flat pricing across the full window, accepts text and images, and returns text, with always-on reasoning (effort: low, high, or max; default max) that cannot be turned off. It is designed for long-horizon coding, agentic and tool-using workflows, and complex knowledge work, and is exposed through an OpenAI-compatible chat completions API. Moonshot has said full weights will be released by November 4, 2026.

Context
1.05M
Max output
1.05M
Input /1M
$2.00
Output /1M
$10.00
Blended /1M
$4.00
AcceptsTextImageProducesTextTokenizer Other

Providers

FastRouter routes your requests to this provider. You can also bring your own key.

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Moonshot AI
moonshotai
Input /1M$2.00
Output /1M$10.00
Context1.05M
Max output1.05M
Latency—
Throughput—
Supports tool callingSupports structured (JSON) output

Supported parameters

Request parameters you can send with this model.

Parameter
Type
Moonshot AI
Core (Sampling & basic generation)
max_tokensMaximum tokens to generate.
number
1 to 1048576
stopSequences where generation stops.
array
temperatureControls randomness of output.
number
0 to 2
top_kLimits sampling to top K tokens.
number
≥ 0
top_pNucleus sampling threshold.
number
0 to 1
Reasoning (Reasoning Controls)
reasoning_effortReasoning effort before answering.
string
"low", "high", "max"default: max
Tool Use (Function Calls & Tools)
tool_choiceHow the model should use tools.
string
"auto", "required", "none"
toolsTool/function definitions available to the model.
array
Output & Format (Response Formatting)
response_formatStructured output format configuration.
string
"text", "json_object", "json_schema"

Performance

Median throughput and time to first token per provider over the last week.

Throughput

Latency

Make your first API call

OpenAI-compatible. Point your SDK at FastRouter, or call the API directly.

Full API docs
Replace <FASTROUTER_API_KEY> with your key · Get your key →Install
OpenAI SDKHTTP
from openai import OpenAI
client = OpenAI(
base_url="https://api.fastrouter.ai/api/v1", # FastRouter base URL
api_key= "<FASTROUTER_API_KEY>", # Replace with your FastRouter API key
)
completion = client.chat.completions.create(
model="moonshotai/kimi-k3.1-pro", # Replace with your model ID
messages=[
{ "role": "user", "content": "What is the meaning of life?" }
]
)
print(completion.choices[0].message.content)

Frequently asked questions

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Model scores sourced from ArtificialAnalysis