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OpenAIGPT-5.5 ProVSOpenAIGPT-5.6 Terra

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 GPT-5.5 Pro and GPT-5.6 Terra directly in their respective provider playgrounds to see which fits your specific prompt styles best.
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Model Specs

GPT-5.5 Pro

Benchmarks & Scores

Coding (swe-bench-pro)
N/A

excellent at multi-file repositories, autonomous agents, and industrial codebases

Reasoning (gpqa-diamond)Winner (+3.3%)
96.2%

graduate-level science QA

Cost & Context

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

GPT-5.6 Terra

Benchmarks & Scores

Coding (swe-bench-pro)
63.4%

excellent at multi-file repositories, autonomous agents, and industrial codebases

Reasoning (gpqa-diamond)
92.9%

graduate-level science QA

Cost & Context

Cost (per 1M tokens)12.0x cheaper
$5.63Input: $2.50 | Output: $15.00
Context Window
1.05M tokens

Frequently Asked Questions about GPT-5.5 Pro vs GPT-5.6 Terra

GPT-5.6 Terra is cheaper than GPT-5.5 Pro. GPT-5.6 Terra has a blended cost of $5.63/1M tokens, which is about 12.0x cheaper than GPT-5.5 Pro at $67.50/1M tokens.

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