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DeepSeekDeepSeek V4 FlashVSOpenAIGPT-5.5 Pro

Analysis by:the whichllmmodel Editorial Team|Updated: June 2026

Our Take

Standardized reasoning and coding benchmarks are currently pending verification for one or both of these models. We recommend testing DeepSeek V4 Flash and GPT-5.5 Pro directly in their respective provider playgrounds to see which fits your specific prompt styles best.
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Model Specs

DeepSeek V4 Flash

Open SourceAPI Available

Benchmarks & Scores

Coding (swe-bench-pro)
49.1%

complex codebases, multi-file repositories, and architectural planning

Reasoning (gpqa-diamond)
80%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)385.7x cheaper
$0.17Input: $0.14 | Output: $0.28
Context Window
1.05M tokens
Model Specs

GPT-5.5 Pro

Benchmarks & Scores

Coding (swe-bench-pro)
N/A

complex codebases, multi-file repositories, and architectural planning

Reasoning (gpqa-diamond)Winner (+16.2%)
96.2%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)
$67.50Input: $30.00 | Output: $180.00
Context WindowLarger
1.05M tokens

Frequently Asked Questions about DeepSeek V4 Flash vs GPT-5.5 Pro

DeepSeek V4 Flash is cheaper than GPT-5.5 Pro. DeepSeek V4 Flash has a blended cost of $0.17/1M tokens, which is about 385.7x cheaper than GPT-5.5 Pro at $67.50/1M tokens.

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