Model comparison

Gemini 3.1 Flash-Lite vs GPT-5.6 Luna

Google against OpenAI, compared on context, price, and verified benchmark results.

Catalog record checked September 26, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

Google

Gemini 3.1 Flash-Lite

Budget

OpenAI

GPT-5.6 Luna

Budget

AI model capability comparison
Specification	Gemini 3.1 Flash-Lite	GPT-5.6 Luna
Provider
Provider	Google	OpenAI
Tier
Tier	Budget	Budget
Context window
Context window	1.05M	Winner: 1.05M
Max output
Max output	66K	Winner: 128K
Input / 1M tokens
Input / 1M tokens	$0.25	Winner: $0.20
Output / 1M tokens
Output / 1M tokens	$1.50	Winner: $1.20
Weights
Weights	Closed	Closed
Parameters
Parameters	Not disclosedUnverified	previous-generation GPT-5.6 small tier
Reasoning levels
Reasoning levels	Not verifiedUnverified	none, low, medium, high, xhigh, max
Modalities
Modalities	text, image, video, audio, pdf	text, image
API model id
API model id	gemini-3.1-flash-lite	gpt-5.6-luna
Released
Released	May 7, 2026	July 9, 2026
Artificial Analysis Intelligence Index (2026-09-26)
Artificial Analysis Intelligence Index (2026-09-26)	15.6	Not verifiedUnverified
Artificial Analysis Intelligence Index [max] (2026-09-26)
Artificial Analysis Intelligence Index [max] (2026-09-26)	Not verifiedUnverified	37.3
SWE-bench Verified (2026-09-01)
SWE-bench Verified (2026-09-01)	Not verifiedUnverified	93
Terminal-Bench 2.1 (2026-07-09)
Terminal-Bench 2.1 (2026-07-09)	Not verifiedUnverified	84.7
LiveBench (2026-09-05)
LiveBench (2026-09-05)	Not verifiedUnverified	73.6

Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

2026-09-26
Artificial Analysis
Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.
Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check measuredAt.
2026-09-05
LiveBench official leaderboard (benchmark-owned), max effort
Contamination-resistant general capability across reasoning, coding, math, data analysis, and language, with monthly question refreshes.
Comparable with caveatRolling question set: observations months apart measure different question mixes. Record the measurement date and compare within ~1 month windows.
2026-09-01
vals.ai SWE-bench Verified leaderboard (independent, mini-swe-agent bash-only) (independent; OpenAI did not report SWE-bench Verified for the GPT-5.6 family)
Real GitHub issue resolution: does the model's patch pass the hidden tests.
Comparable with caveatPost-audit vendor claims and pre-audit scores sit on different task trust levels; scaffolding (agent harness, compute budget) also dominates results. Never aggregate across scaffolds.
2026-07-09
OpenAI GPT-5.6 announcement (vendor; chart transcribed by Vellum)
Agentic terminal work: multi-step tasks executed in a sandboxed shell environment.
Comparable with caveatNot comparable with Terminal-Bench 3.0 or 4.0 (different task sets) or v1; harness configuration (container, time limits) also shifts results.

Pricing tiers

Gemini 3.1 Flash-Lite: $0.25 input (text, image, video; $0.50 audio) / $1.50 output per MTok; cached input $0.025. GA 2026-05-07 after a 2026-03-03 preview; shutdown no earlier than 2027-05-07.

GPT-5.6 Luna: Launch list was $1/$6; cut to $0.20/$1.20 on 2026-07-30. Above 272K input the whole request bills 2x input / 1.5x output. Cached input $0.02/MTok; cache writes 1.25x input; batch $0.10/$0.60.

BudgetRecord checked September 26, 2026

Gemini 3.1 Flash-Lite

Gemini 3.1 Flash-Lite is Google's cheapest current Gemini API model for high-volume, latency-sensitive pipelines.

Best for

High-volume extraction
Classification
Cheap multimodal input

Watch out

Google recommends 3.5 Flash-Lite for new work, and 3.1 Flash-Lite's earliest shutdown date is 2027-05-07; well behind Flash models on reasoning.

BudgetRecord checked September 26, 2026

GPT-5.6 Luna

GPT-5.6 Luna was OpenAI's cheapest GPT-5.6 tier; GPT-6 Luna replaced it on 2026-09-22 at half the price ($0.10/$0.50).

Best for

Classification
High-volume chat
Latency-sensitive pipelines

Watch out

Superseded by GPT-6 Luna, which costs half as much and matches it on the Artificial Analysis index; still served, not deprecated.

When the cheaper one wins

GPT-5.6 Luna is cheaper on output at $1.20 per million tokens against $1.50 for Gemini 3.1 Flash-Lite — about 1.3×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.

Run the model picker

Evidence confidence: High

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

Pricing verified on both sides — Input and output rates are verified for both models.
3/5 core specs verified on both sides — Not published for at least one side: parameter count, reasoning levels.
1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
Verified within the last 90 days — Newest catalog check was 2 days ago.
Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Gemini 3.1 Flash-Lite: Gemini API pricing (gemini-3.1-flash-lite $0.25/$1.50) (accessed 2026-09-26)
Gemini 3.1 Flash-Lite: Gemini API — gemini-3.1-flash-lite model card (accessed 2026-09-26)
Gemini 3.1 Flash-Lite: Gemini API deprecations (earliest shutdown 2027-05-07) (accessed 2026-09-26)
GPT-5.6 Luna: OpenAI — GPT-5.6 (accessed 2026-08-29)
GPT-5.6 Luna: OpenAI API pricing (gpt-5.6-luna $0.20/$1.20) (accessed 2026-08-29)
GPT-5.6 Luna: OpenAI — Introducing GPT-6 Sol and Luna (GPT-5.6 Luna successor) (accessed 2026-09-26)

Related comparisons

Diving deeper on one model? Gemini 3.1 Flash-Lite · GPT-5.6 Luna

Common questions

Gemini 3.1 Flash-Lite vs GPT-5.6 Luna

Answered from the verified figures on this page rather than general guidance.

Is Gemini 3.1 Flash-Lite or GPT-5.6 Luna cheaper for input?

GPT-5.6 Luna is cheaper at $0.20 per million input tokens, against $0.25 for Gemini 3.1 Flash-Lite — roughly 1.3× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Gemini 3.1 Flash-Lite has tiered pricing: $0.25 input (text, image, video; $0.50 audio) / $1.50 output per MTok; cached input $0.025. GA 2026-05-07 after a 2026-03-03 preview; shutdown no earlier than 2027-05-07. GPT-5.6 Luna has tiered pricing: Launch list was $1/$6; cut to $0.20/$1.20 on 2026-07-30. Above 272K input the whole request bills 2x input / 1.5x output. Cached input $0.02/MTok; cache writes 1.25x input; batch $0.10/$0.60.

Is Gemini 3.1 Flash-Lite or GPT-5.6 Luna cheaper for output?

GPT-5.6 Luna is cheaper at $1.20 per million output tokens, against $1.50 for Gemini 3.1 Flash-Lite — roughly 1.3× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Gemini 3.1 Flash-Lite has tiered pricing: $0.25 input (text, image, video; $0.50 audio) / $1.50 output per MTok; cached input $0.025. GA 2026-05-07 after a 2026-03-03 preview; shutdown no earlier than 2027-05-07. GPT-5.6 Luna has tiered pricing: Launch list was $1/$6; cut to $0.20/$1.20 on 2026-07-30. Above 272K input the whole request bills 2x input / 1.5x output. Cached input $0.02/MTok; cache writes 1.25x input; batch $0.10/$0.60.

Which has the larger context window, Gemini 3.1 Flash-Lite or GPT-5.6 Luna?

Both accept about 1.05M tokens of context, so document length will not decide between them.

Should I use Gemini 3.1 Flash-Lite or GPT-5.6 Luna?

Both sit in the budget tier, so the choice usually comes down to price and context rather than capability. Gemini 3.1 Flash-Lite suits high-volume extraction; GPT-5.6 Luna suits classification.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

Input price: GPT-5.6 Luna costs $0.20 per 1M tokens versus $0.25 for Gemini 3.1 Flash-Lite — a 1.3x difference at the headline tier.
Context: GPT-5.6 Luna takes 1.05M against 1.05M for Gemini 3.1 Flash-Lite — only decisive if your prompts approach the smaller window.
Measured capability: GPT-5.6 Luna leads Artificial Analysis Intelligence Index 37.3 to 15.6 (measured 2026-09-26).

Run the model picker Estimate stack cost All model comparisons

Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.