# GPT-5.1-Codex vs Kimi K2.5 (Reasoning)

> Side-by-side benchmark comparison for GPT-5.1-Codex and Kimi K2.5 (Reasoning) across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-1-codex-vs-kimi-k2-5-reasoning
- Last updated: September 29, 2026

- Shared sourced benchmarks: 2
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.7

## Quick Verdict

Evidence is too thin for a benchmark verdict: GPT-5.1-Codex and Kimi K2.5 (Reasoning) share only 2 sourced benchmark rows.

## Summary

- Only 2 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Kimi K2.5 (Reasoning) has the lower published output-token price.
- GPT-5.1-Codex has the larger published context window at 400K.

## Model Snapshot

| Property | GPT-5.1-Codex | Kimi K2.5 (Reasoning) |
|----------|----------|----------|
| Creator | OpenAI | Moonshot AI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 400K | 128K |
| Independent public score (not head-to-head) | 44.38 | null |
| Benchmarks Covered | 4 | 9 |
| Pricing (input/output) | $1.25 / $10.00 | $0.60 / $3.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: Coming soon
- Kimi K2.5 (Reasoning) public-lane score: Coming soon

| Benchmark | GPT-5.1-Codex | Kimi K2.5 (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| Gert Labs | 49.68% | 32.58% | GPT-5.1-Codex |
| JobBench | 26.2% | Coming soon | Coming soon |
| Terminal-Bench 2.0 | Coming soon | 50.8% | Coming soon |
| BrowseComp | Coming soon | 60.6% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 32.7 (Estimated · #85/143)
- Kimi K2.5 (Reasoning) public-lane score: Coming soon

| Benchmark | GPT-5.1-Codex | Kimi K2.5 (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 13.12% | 17.54% | Kimi K2.5 (Reasoning) |
| LiveCodeBench (Vals) | 85.6% | Coming soon | Coming soon |
| SWE-bench Verified | Coming soon | 76.8% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 69.9 (Unranked · 2 rankable rows)
- Kimi K2.5 (Reasoning) public-lane score: Coming soon

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 67.9 (Unranked · 1 rankable row)
- Kimi K2.5 (Reasoning) public-lane score: 64.4 (Unranked · 1 rankable row)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | Coming soon | 78.5% | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 48.1 (Estimated · #69/169)
- Kimi K2.5 (Reasoning) public-lane score: Coming soon

| Benchmark | GPT-5.1-Codex | Kimi K2.5 (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| GPQA | Coming soon | 87.6% | Coming soon |
| MMLU-Pro | Coming soon | 87.1% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 84.2 (#42/124)
- Kimi K2.5 (Reasoning) public-lane score: Coming soon

### Mathematics

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: Coming soon
- Kimi K2.5 (Reasoning) public-lane score: Coming soon

| Benchmark | GPT-5.1-Codex | Kimi K2.5 (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| AIME 2025 | Coming soon | 96.1% | Coming soon |

## FAQ

### Is there enough evidence to pick between GPT-5.1-Codex and Kimi K2.5 (Reasoning)?

Not yet. The models share only 2 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

- [GPT-5.1-Codex vs Kimi K2.5](/compare/gpt-5-1-codex-vs-kimi-k2-5)
- [Kimi K2.5 (Reasoning) vs Kimi K2.5](/compare/kimi-k2-5-vs-kimi-k2-5-reasoning)
- [GPT-5.1-Codex vs GPT-6 Astra](/compare/gpt-5-1-codex-vs-gpt-6-astra)
- [Kimi K2.5 (Reasoning) vs GPT-6 Astra](/compare/gpt-6-astra-vs-kimi-k2-5-reasoning)

## Explore More

- [GPT-5.1-Codex profile](/models/gpt-5-1-codex)
- [Kimi K2.5 (Reasoning) profile](/models/kimi-k2-5-reasoning)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)