OpenAI GPT-5.5 Pro VS OpenAI GPT-5.6 Luna

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

Decision Recommendation

⚖️ Editorial Verdict: In our analysis, GPT-5.6 Luna is the premium intelligence choice, scoring 62.7% higher on coding benchmarks. It also maintains strong cost efficiency. If you are building high-volume, simple chatbots or processing massive amounts of text where budget is critical, GPT-5.5 Pro offers excellent cost savings. For agentic reasoning, code refactoring, or complex logical tasks, the accuracy premium of GPT-5.6 Luna fully justifies the cost.

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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 (+3.9%)

96.2%

graduate-level science QA

Cost & Performance

Cost (per 1M tokens)

$67.50Input: $30.00 | Output: $180.00

Context Window

1.05M tokens

Model Specs

GPT-5.6 Luna

Benchmarks & Scores

Coding (swe-bench-pro)

62.7%

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

Reasoning (gpqa-diamond)

92.3%

graduate-level science QA

Cost & Performance

Cost (per 1M tokens)30.0x cheaper

$2.25Input: $1.00 | Output: $6.00

Context Window

1.05M tokens

Read our data collection methodology

Frequently Asked Questions about GPT-5.5 Pro vs GPT-5.6 Luna comparison

GPT-5.6 Luna is cheaper than GPT-5.5 Pro. GPT-5.6 Luna has a blended cost of $2.25/1M tokens, which is about 30.0x cheaper than GPT-5.5 Pro at $67.50/1M tokens.

GPT-5.6 Luna is better for coding tasks on this benchmark. It scores 62.7% on swe-bench-pro (excellent at multi-file repositories, autonomous agents, and industrial codebases) compared to GPT-5.5 Pro which scores N/A.

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