# GPT-5.1-Codex vs Grok 4.1 Fast

> Side-by-side benchmark comparison for GPT-5.1-Codex and Grok 4.1 Fast across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-1-codex-vs-grok-4-1-fast
- Last updated: September 4, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Evidence is too thin for a benchmark verdict: GPT-5.1-Codex and Grok 4.1 Fast share only 1 sourced benchmark row.

## Summary

- Only 1 shared sourced benchmark row is available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Grok 4.1 Fast has the lower published output-token price.
- Grok 4.1 Fast has the larger published context window at 1M.

## Model Snapshot

| Property | GPT-5.1-Codex | Grok 4.1 Fast |
|----------|----------|----------|
| Creator | OpenAI | xAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Non-Reasoning |
| Context | 400K | 1M |
| Independent public score (not head-to-head) | 51.62 | 49.8 |
| Benchmarks Covered | 3 | 1 |
| Pricing (input/output) | $1.25 / $10.00 | $0.20 / $0.50 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 51.4 (Estimated · #54/151)
- Grok 4.1 Fast public-lane score: Coming soon

| Benchmark | GPT-5.1-Codex | Grok 4.1 Fast | Winner |
|-----------|-----------|-----------|--------|
| Gert Labs | 49.68% | 47.32% | GPT-5.1-Codex |
| JobBench | 26.2% | Coming soon | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 47.4 (Estimated · #89/183)
- Grok 4.1 Fast public-lane score: 47.5 (Estimated · #88/183)

| Benchmark | GPT-5.1-Codex | Grok 4.1 Fast | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 13.12% | Coming soon | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 66.8 (Unranked · 1 rankable row)
- Grok 4.1 Fast public-lane score: 31.3 (Unranked · 1 rankable row)

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 70.6 (Unranked · 2 rankable rows)
- Grok 4.1 Fast public-lane score: 41.7 (Unranked · 2 rankable rows)

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 53.3 (Estimated · #69/181)
- Grok 4.1 Fast public-lane score: 42.1 (Estimated · #130/181)

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.1-Codex public-lane score: 85.3 (#42/120)
- Grok 4.1 Fast public-lane score: 41.8 (#99/120)

## FAQ

### Is there enough evidence to pick between GPT-5.1-Codex and Grok 4.1 Fast?

Not yet. The models share only 1 sourced benchmark row, 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 Grok 4.1 Fast (Reasoning)](/compare/gpt-5-1-codex-vs-grok-4-1-fast-reasoning)
- [Grok 4.1 Fast vs Grok 4.1 Fast (Reasoning)](/compare/grok-4-1-fast-vs-grok-4-1-fast-reasoning)
- [GPT-5.1-Codex vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-gpt-5-1-codex)
- [Grok 4.1 Fast vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-grok-4-1-fast)

## Explore More

- [GPT-5.1-Codex profile](/models/gpt-5-1-codex)
- [Grok 4.1 Fast profile](/models/grok-4-1-fast)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)