$ diff claude-sonnet-5-5 deepseek-v4-1-flash

Claude Sonnet 5.5 vs DeepSeek V4.1-Flash

Values come from Claude Sonnet 5.5 and DeepSeek V4.1-Flash, where each is cited to its source. This page states no benchmark result and ranks neither model — it puts two published specifications next to each other. Where a lab has not published a figure, the row says so rather than guessing.

AnthropicClaude Sonnet 5.5

context: 1M
weights: closed
$/M in: $2
$/M out: $10

DeepSeekDeepSeek V4.1-Flash

context: 1M
weights: open
$/M in: $0.15
$/M out: $0.6

What actually differs

Context window: Identical — both accept 1M tokens, so context length is not a reason to pick either.
Input price: DeepSeek V4.1-Flash at $0.15/M against $2/M — 13.3× cheaper to feed. Standard rates: one of these labs also quotes a lower cached-input tier, which applies only when a prefix is reused — see the full spec below.
Output price: DeepSeek V4.1-Flash at $0.6/M against $10/M — 16.7× cheaper to generate. Output dominates the bill on most agentic workloads, where the model writes far more than it reads.
Weights: DeepSeek V4.1-Flash publishes weights (MIT (open-weight)); Claude Sonnet 5.5 is API-only. That decides self-hosting, air-gapped deployment and fine-tuning before any capability question does.
Recency: Claude Sonnet 5.5 shipped 18 days after DeepSeek V4.1-Flash (2026-09-28 vs 2026-09-10).

Full spec

Attribute	Claude Sonnet 5.5	DeepSeek V4.1-Flash
Developer	Anthropic	DeepSeek
Released	2026-09-28	2026-09-10
Context window	1M tokens	1,000,000
Pricing	$2/M input · $10/M output · cache reads 10% of base input	$0.15/M input (cache miss) · $0.003/M input (cache hit) · $0.60/M output, off-peak; peak rates double — see Pricing
License	proprietary (API-only; no weight release)	MIT (open-weight)
Availability	Claude apps, Claude API as `claude-sonnet-5-5`, Amazon Bedrock, Google Cloud Vertex AI, Microsoft Foundry, Claude Platform on AWS	DeepSeek API, Hugging Face (`deepseek-ai/DeepSeek-V4.1-Flash`)

How these pages are produced

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