Which is cheaper, Claude Sonnet 5.5 and DeepSeek V4 Pro?

DeepSeek V4 Pro has the lowest input price. Per 1M input tokens: Claude Sonnet 5.5 from $2.00 and DeepSeek V4 Pro from $1.74.

Which has the larger context window, Claude Sonnet 5.5 and DeepSeek V4 Pro?

DeepSeek V4 Pro has the largest context window: Claude Sonnet 5.5 1,000,000 tokens and DeepSeek V4 Pro 1,048,576 tokens.

Which is smarter, Claude Sonnet 5.5 and DeepSeek V4 Pro?

Claude Sonnet 5.5 scores highest on the Artificial Analysis Intelligence Index: Claude Sonnet 5.5 54.2 and DeepSeek V4 Pro 23.1.

Can I switch between Claude Sonnet 5.5 and DeepSeek V4 Pro 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, deepseek/deepseek-v4-pro).

Claude Sonnet 5.5 vs DeepSeek V4 Pro

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

Estimate monthly cost for these models

Claude Sonnet 5.5 Anthropicanthropic/claude-sonnet-5.5

DeepSeek V4 Pro DeepSeekdeepseek/deepseek-v4-pro

Creator

Anthropic

DeepSeek

Released

Sep 28, 2026

Apr 24, 2026

Context window

1.05M

Max output

128K

384K

Input / 1MLowest provider price

$2.00

$1.74$1.74–$2.40 across 3

Output / 1MLowest provider price

$10.00

$3.48$3.48–$4.80 across 3

Providers

IntelligenceArtificial Analysis index

54.2

23.1

LatencyMedian time to first token

—

4.9s

ThroughputMedian tokens per second

—

<1 t/s

Accepts

Text, Image

Text

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Claude Sonnet 5.5 vs DeepSeek V4 Pro: summary

Claude Sonnet 5.5 and DeepSeek V4 Pro 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 from $2.00/1M input and $10.00/1M output tokens across 3 providers and scores 54.2 on the Artificial Analysis Intelligence Index.

DeepSeek V4 Pro, from DeepSeek, has a 1,048,576-token context window, costs from $1.74/1M input and $3.48/1M output tokens across 3 providers and scores 23.1 on the Artificial Analysis Intelligence Index.

DeepSeek V4 Pro is the cheapest on input, 1.1× cheaper than the next model, DeepSeek V4 Pro 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="deepseek/deepseek-v4-pro", messages=[...])

Full API docs

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Benchmark scores sourced from ArtificialAnalysis