# Gemini 3.1 Flash-Lite vs GPT-5.1-Codex

> Side-by-side benchmark comparison for Gemini 3.1 Flash-Lite and GPT-5.1-Codex across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gemini-3-1-flash-lite-vs-gpt-5-1-codex
- Last updated: September 29, 2026

- Shared sourced benchmarks: 3
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.7

## Quick Verdict

Evidence is too thin for a benchmark verdict: Gemini 3.1 Flash-Lite and GPT-5.1-Codex share only 3 sourced benchmark rows.

## Summary

- Only 3 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Gemini 3.1 Flash-Lite has the lower published output-token price.
- Gemini 3.1 Flash-Lite has the larger published context window at 1M.

## Model Snapshot

| Property | Gemini 3.1 Flash-Lite | GPT-5.1-Codex |
|----------|----------|----------|
| Creator | Google | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 1M | 400K |
| Independent public score (not head-to-head) | 50.01 | 44.38 |
| Benchmarks Covered | 8 | 4 |
| Pricing (input/output) | $0.25 / $1.50 | $1.25 / $10.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Gemini 3.1 Flash-Lite public-lane score: 30 (Estimated · #80/117)
- GPT-5.1-Codex public-lane score: Coming soon

| Benchmark | Gemini 3.1 Flash-Lite | GPT-5.1-Codex | Winner |
|-----------|-----------|-----------|--------|
| Gert Labs | 38.46% | 49.68% | GPT-5.1-Codex |
| Terminal-Bench 2.1 (Vals) | 34.1% | Coming soon | Coming soon |
| JobBench | Coming soon | 26.2% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Gemini 3.1 Flash-Lite public-lane score: 27.7 (Estimated · #97/143)
- GPT-5.1-Codex public-lane score: 32.7 (Estimated · #85/143)

| Benchmark | Gemini 3.1 Flash-Lite | GPT-5.1-Codex | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 0.00% | 13.12% | GPT-5.1-Codex |
| LiveCodeBench (Vals) | 80.1% | 85.6% | GPT-5.1-Codex |
| SWE-bench (Vals) | 62.8% | Coming soon | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Gemini 3.1 Flash-Lite public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 69.9 (Unranked · 2 rankable rows)

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Gemini 3.1 Flash-Lite public-lane score: 38.5 (Unranked · 1 rankable row)
- GPT-5.1-Codex public-lane score: 67.9 (Unranked · 1 rankable row)

| Benchmark | Gemini 3.1 Flash-Lite | GPT-5.1-Codex | Winner |
|-----------|-----------|-----------|--------|
| CharXiv | 73.2% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Gemini 3.1 Flash-Lite public-lane score: 47.6 (Estimated · #72/169)
- GPT-5.1-Codex public-lane score: 48.1 (Estimated · #69/169)

| Benchmark | Gemini 3.1 Flash-Lite | GPT-5.1-Codex | Winner |
|-----------|-----------|-----------|--------|
| GPQA Diamond (Vals) | 81.1% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 86.2% | Coming soon | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Gemini 3.1 Flash-Lite public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 84.2 (#42/124)

## FAQ

### Is there enough evidence to pick between Gemini 3.1 Flash-Lite and GPT-5.1-Codex?

Not yet. The models share only 3 sourced benchmark rows, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [Gemini 3.1 Flash-Lite vs GPT-6 Astra](/compare/gemini-3-1-flash-lite-vs-gpt-6-astra)
- [GPT-5.1-Codex vs GPT-6 Astra](/compare/gpt-5-1-codex-vs-gpt-6-astra)
- [Gemini 3.1 Flash-Lite vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gemini-3-1-flash-lite)
- [GPT-5.1-Codex vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gpt-5-1-codex)

## Explore More

- [Gemini 3.1 Flash-Lite profile](/models/gemini-3-1-flash-lite)
- [GPT-5.1-Codex profile](/models/gpt-5-1-codex)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)