Which is cheaper, Claude Sonnet 5 and DeepSeek V4.1 Flash?

DeepSeek V4.1 Flash has the lowest input price. Per 1M input tokens: Claude Sonnet 5 from $2.00 and DeepSeek V4.1 Flash from $0.20.

Which has the larger context window, Claude Sonnet 5 and DeepSeek V4.1 Flash?

DeepSeek V4.1 Flash has the largest context window: Claude Sonnet 5 1,000,000 tokens and DeepSeek V4.1 Flash 1,048,576 tokens.

Which is smarter, Claude Sonnet 5 and DeepSeek V4.1 Flash?

DeepSeek V4.1 Flash scores highest on the Artificial Analysis Intelligence Index: Claude Sonnet 5 38.2 and DeepSeek V4.1 Flash 39.5.

Can I switch between Claude Sonnet 5 and DeepSeek V4.1 Flash 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, deepseek/deepseek-v4.1-flash).

Claude Sonnet 5 vs DeepSeek V4.1 Flash

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

Claude Sonnet 5 Anthropicanthropic/claude-sonnet-5

DeepSeek V4.1 Flash DeepSeekdeepseek/deepseek-v4.1-flash

Creator

Anthropic

DeepSeek

Released

Jul 1, 2026

Sep 14, 2026

Context window

1.05M

Max output

128K

944K

Input / 1MLowest provider price

$2.00

$0.20$0.20–$0.30 across 5

Output / 1MLowest provider price

$10.00

$0.60$0.60–$1.20 across 5

Providers

IntelligenceArtificial Analysis index

38.2

39.5

CodingArtificial Analysis index

71.5

—

LatencyMedian time to first token

4.4s

—

ThroughputMedian tokens per second

<1 t/s

—

Accepts

Text, Image

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Claude Sonnet 5 vs DeepSeek V4.1 Flash: summary

Claude Sonnet 5 and DeepSeek V4.1 Flash 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, from Anthropic, has a 1,000,000-token context window, costs from $2.00/1M input and $10.00/1M output tokens across 2 providers and scores 38.2 on the Artificial Analysis Intelligence Index.

DeepSeek V4.1 Flash, from DeepSeek, has a 1,048,576-token context window, costs from $0.20/1M input and $0.60/1M output tokens across 5 providers and scores 39.5 on the Artificial Analysis Intelligence Index.

DeepSeek V4.1 Flash is the cheapest on input, 10× cheaper than the next model, DeepSeek V4.1 Flash has the largest context window and DeepSeek V4.1 Flash 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", messages=[...]) # or client.chat.completions.create(model="deepseek/deepseek-v4.1-flash", messages=[...])

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Benchmark scores sourced from ArtificialAnalysis