Which is cheaper, Claude Sonnet 5.5 and Kimi K3?

Claude Sonnet 5.5 has the lowest input price. Per 1M input tokens: Claude Sonnet 5.5 from $2.00 and Kimi K3 from $2.70.

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

Kimi K3 has the largest context window: Claude Sonnet 5.5 1,000,000 tokens and Kimi K3 1,048,576 tokens.

Can I switch between Claude Sonnet 5.5 and Kimi K3 without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (anthropic/claude-sonnet-5.5, moonshotai/kimi-k3).

Claude Sonnet 5.5 vs Kimi K3

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

Claude Sonnet 5.5 Anthropicanthropic/claude-sonnet-5.5

Kimi K3 MoonshotAImoonshotai/kimi-k3

Creator

Anthropic

MoonshotAI

Released

Sep 28, 2026

Jul 16, 2026

Context window

1.05M

Max output

128K

1.05M

Input / 1MLowest provider price

$2.00

$2.70$2.70–$3.00 across 4

Output / 1MLowest provider price

$10.00

$13.50$13.50–$15.00 across 4

Providers

IntelligenceArtificial Analysis index

56.0

43.6

CodingArtificial Analysis index

—

76.2

LatencyMedian time to first token

—

7.4s

ThroughputMedian tokens per second

—

<1 t/s

Accepts

Text, Image

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Claude Sonnet 5.5 vs Kimi K3: summary

Claude Sonnet 5.5 and Kimi K3 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Claude Sonnet 5.5, from Anthropic, has a 1,000,000-token context window, costs $2.00/1M input and $10.00/1M output tokens and scores 56.0 on the Artificial Analysis Intelligence Index.

Kimi K3, from MoonshotAI, has a 1,048,576-token context window, costs from $2.70/1M input and $13.50/1M output tokens across 4 providers and scores 43.6 on the Artificial Analysis Intelligence Index.

Claude Sonnet 5.5 is the cheapest on input, 1.4× cheaper than the next model, Kimi K3 has the largest context window and Claude Sonnet 5.5 scores highest for intelligence.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="anthropic/claude-sonnet-5.5", messages=[...]) # or client.chat.completions.create(model="moonshotai/kimi-k3", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis