Claude Sonnet 5.5 vs Kimi K3

As of October 21, 2026, Kimi K3 costs 50% more per input token than Claude Sonnet 5.5 ($3.00 vs $2.00 per 1M) and has a 1,048,576-token context window versus 1,000,000.

Prices from LiteLLM's price fileChecked October 21, 2026

Claude Sonnet 5.5 vs Kimi K3 side by side

Headline prices in US dollars per 1M tokens: each model's own lab where it sells it, otherwise its cheapest provider. Source: LiteLLM model price file, as of October 21, 2026.
	Claude Sonnet 5.5	Kimi K3
Input, per 1M tokens	$2.00	$3.00
Output, per 1M tokens	$10.00	$15.00
Cache read, per 1M tokens	$0.10	$0.30
Cache write, per 1M tokens	$2.50	–
Context window	1,000,000 tokens	1,048,576 tokens
Max output	128,000 tokens	1,048,576 tokens
Image input	Yes	Yes
Tool calling	Yes	Yes
Structured output (JSON)	Yes	Yes
Prompt caching	Yes	Yes
Reasoning	Yes	Yes
Providers on LiteLLM	7	15
Price shown is from	Anthropic	Moonshot AI
Added to LiteLLM	September 28, 2026	August 16, 2026

Cheapest provider for each

Claude Sonnet 5.5: Anthropic at $2.00 input and $10.00 output per 1M tokens (claude-sonnet-5-5)
Kimi K3: Sail at $2.50 input and $12.50 output per 1M tokens (sail/moonshotai/Kimi-K3)

Benchmark scores

From the Epoch AI Benchmarking Hub (CC BY 4.0), data as of September 29, 2026. Some results were run by Epoch and others collected by Epoch from each benchmark's own leaderboard, linked in the first column. Each model's best reported reasoning setting is shown in brackets. Higher is better. Only benchmarks with a score for both models are shown.
Benchmark	Claude Sonnet 5.5	Kimi K3
Overall
Epoch Capabilities Index	166.2	157.9
Coding and agents
FrontierCode	52.1% (xhigh)	44.2%
FrontierSWE	61.9% (max)	25.9% (max)
APEX-Agents	75.5% (max)	47.8%
Reasoning and knowledge
GPQA Diamond	95.6% (max)	93.1% (max)
SimpleQA Verified	46.5% (max)	50.6% (max)
Math
FrontierMath (tiers 1-3)	88.8% (max)	72.2% (max)
FrontierMath (tier 4)	80.5% (max)	39.0% (max)
OTIS Mock AIME 2024-2025	100.0% (max)	97.2% (max)

When to pick which

Pick Claude Sonnet 5.5 for

Costs 33% less per input token: $2.00 vs $3.00 per 1M.

Pick Kimi K3 for

Returns up to 1,048,576 tokens per response, vs 128,000.
Available from 15 providers through LiteLLM, vs 7.

From differences in the data above only; where the data is equal, no reason is given.

Call Claude Sonnet 5.5 or Kimi K3 with LiteLLM

Both use the OpenAI format through LiteLLM, so switching is a model name change. Set each provider's API key in the environment first.

Python SDK

from litellm import completion

messages = [{"role": "user", "content": "Hello!"}]

# Claude Sonnet 5.5
response = completion(model="claude-sonnet-5-5", messages=messages)

# Kimi K3
response = completion(model="moonshot/kimi-k3", messages=messages)

# Claude Sonnet 5.5, falling back to Kimi K3 if the call fails
response = completion(model="claude-sonnet-5-5", messages=messages, fallbacks=["moonshot/kimi-k3"])

FAQ

Which is cheaper, Claude Sonnet 5.5 or Kimi K3?

Claude Sonnet 5.5 is cheaper at 3 input tokens per output token: $4.00 per 1M tokens blended ($2.00 input, $10.00 output), versus $6.00 ($3.00 and $15.00) for Kimi K3, as of October 21, 2026.

Which has the larger context window, Claude Sonnet 5.5 or Kimi K3?

Kimi K3 has the larger context window: 1,048,576 tokens, versus 1,000,000 for Claude Sonnet 5.5.

Can I switch from Claude Sonnet 5.5 to Kimi K3 without changing my code?

Yes. Through LiteLLM both use the OpenAI format, so switching means changing the model name from "claude-sonnet-5-5" to "moonshot/kimi-k3", or pointing a LiteLLM gateway model alias at the other model. You can also use one as a fallback for the other.