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Gemini 3.1 Pro Preview vs GPT-5.6 Luna

SpecGemini 3.1 Pro PreviewGPT-5.6 Luna
Respan Index43.9 (#51)48.8 (#37)
Blended price per 1M$2.25$0.225
Context window1.0M1.1M
Input / output per 1M$1 / $6$0.1 / $0.6
Max output66K128K
Inputtext, vision, audiotext, vision
Released2026-02-192026-07-09

Respan Index by category

Each category is scored 0 to 100, and how far ahead the winner is. Leads under a point are close to even.

CategoryGemini 3.1 Pro PreviewGPT-5.6 Luna
Coding15.6 Gemini 3.1 Pro Preview27.8 GPT-5.6 Luna
Agents53.6 Gemini 3.1 Pro Preview56.9 GPT-5.6 Luna
Reasoning46.2 Gemini 3.1 Pro Preview62.6 GPT-5.6 Luna
Knowledge & language72.5 Gemini 3.1 Pro Preview38.7 GPT-5.6 Luna
Human preference52.2 Gemini 3.1 Pro Preview53.8 GPT-5.6 Luna

How the Respan Index works

Benchmarks both report

They split the 28 benchmarks both report evenly. Higher is better. Each score links to where it was published.

BenchmarkGemini 3.1 Pro PreviewGPT-5.6 Luna
APEX-Agents (Mercor)35.1%43%
Chess Puzzles (Epoch AI)51%43%
LMArena Agent (LMArena)-0.0445-0.0081
LMArena Elo14871453
LMArena WebDev (LMArena)14471519
LMArena Vision (LMArena)12801257
DeepSWE v1.1 (Datacurve)11.7%67.2%
FrontierMath Tier 4 v2 (Epoch AI)26.8%61%
FrontierMath Tiers 1-3 v2 (Epoch AI)59.6%82.1%
Furniture Assembly (Epoch AI)26.7%42.5%
GPQA Diamond94.3%92.3%
LiveBench Agentic Coding (LiveBench)44.1%48.4%
LiveBench Coding (LiveBench)76.5%82.9%
LiveBench Data Analysis (LiveBench)78.5%78%
LiveBench Instruction Following (LiveBench)79.1%60.1%
LiveBench Language (LiveBench)85.4%72.6%
LiveBench Mathematics (LiveBench)91%87.2%
LiveBench Reasoning (LiveBench)84%85.6%
Mystery Game Puzzles (Epoch AI)34%21%
OTIS Mock AIME 2024-2025 (Epoch AI)95.6%98.3%
SAGE (Vals AI)48.7%44.2%
SimpleQA Verified73.5%41%
Terminal-Bench 4.0 (Vals AI)2.5%11.6%
Vending-Bench 2 (Andon Labs)3774.254094.71
WeirdML (Håvard Tveit Ihle)72.1%60.9%
SWE-Bench Pro54.2%62.7%
BALROG (BALROG)57%45.6%
SimpleBench (SimpleBench)79.6%46.8%

FAQ

Is Gemini 3.1 Pro Preview better than GPT-5.6 Luna?

GPT-5.6 Luna scores 48.8 on the Respan Index (#37), ahead of Gemini 3.1 Pro Preview at 43.9 (#51). They split the 28 benchmarks both report evenly.

Which is cheaper, Gemini 3.1 Pro Preview or GPT-5.6 Luna?

Gemini 3.1 Pro Preview lists at $1 input and $6 output per 1M tokens; GPT-5.6 Luna at $0.1 and $0.6. GPT-5.6 Luna is 10x cheaper per token at list price.

Which has the larger context window?

Gemini 3.1 Pro Preview accepts 1.0M tokens and GPT-5.6 Luna 1.1M tokens.

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