# GPT-5.3 Codex vs Grok 4.1 Fast (Reasoning)

> Side-by-side benchmark comparison for GPT-5.3 Codex and Grok 4.1 Fast (Reasoning) across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-3-codex-vs-grok-4-1-fast-reasoning
- 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-5.3 Codex and Grok 4.1 Fast (Reasoning) 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 (Reasoning) has the larger published context window at 2M.

## Model Snapshot

| Property | GPT-5.3 Codex | Grok 4.1 Fast (Reasoning) |
|----------|----------|----------|
| Creator | OpenAI | xAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 400K | 2M |
| Independent public score (not head-to-head) | 65.22 | 58.18 |
| Benchmarks Covered | 8 | 1 |
| Pricing (input/output) | $1.75 / $14.00 | N/A |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.3 Codex public-lane score: 62.3 (Estimated · #19/151)
- Grok 4.1 Fast (Reasoning) public-lane score: Coming soon

| Benchmark | GPT-5.3 Codex | Grok 4.1 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | 77.3% | Coming soon | Coming soon |
| OSWorld-Verified | 64.7% | Coming soon | Coming soon |
| Gert Labs | 57.47% | Coming soon | Coming soon |
| JobBench | 33.7% | Coming soon | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.3 Codex public-lane score: 62.7 (Supported · #16/183)
- Grok 4.1 Fast (Reasoning) public-lane score: 48.7 (Estimated · #85/183)

| Benchmark | GPT-5.3 Codex | Grok 4.1 Fast (Reasoning) | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 85% | Coming soon | Coming soon |
| SWE-bench Pro | 56.8% | Coming soon | Coming soon |
| SWE-Rebench | 58.2% | Coming soon | Coming soon |
| Vibe Code Bench | 61.77% | 1.20% | GPT-5.3 Codex |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.3 Codex public-lane score: 75.6 (Unranked · 1 rankable row)
- Grok 4.1 Fast (Reasoning) public-lane score: 53.3 (Unranked · 1 rankable row)

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.3 Codex public-lane score: 77.3 (Unranked · 2 rankable rows)
- Grok 4.1 Fast (Reasoning) public-lane score: 71.6 (Unranked · 2 rankable rows)

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.3 Codex public-lane score: 66.3 (Estimated · #22/181)
- Grok 4.1 Fast (Reasoning) public-lane score: 51.5 (Estimated · #82/181)

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.3 Codex public-lane score: 92.3 (#15/120)
- Grok 4.1 Fast (Reasoning) public-lane score: 62.8 (#69/120)

## FAQ

### Is there enough evidence to pick between GPT-5.3 Codex and Grok 4.1 Fast (Reasoning)?

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-5.3 Codex vs GPT-5.3-Codex-Spark](/compare/gpt-5-3-codex-vs-gpt-5-3-codex-spark)
- [Grok 4.1 Fast (Reasoning) vs GPT-5.3-Codex-Spark](/compare/gpt-5-3-codex-spark-vs-grok-4-1-fast-reasoning)
- [GPT-5.3 Codex vs Grok 4.1 Fast](/compare/gpt-5-3-codex-vs-grok-4-1-fast)
- [Grok 4.1 Fast (Reasoning) vs Grok 4.1 Fast](/compare/grok-4-1-fast-vs-grok-4-1-fast-reasoning)

## Explore More

- [GPT-5.3 Codex profile](/models/gpt-5-3-codex)
- [Grok 4.1 Fast (Reasoning) profile](/models/grok-4-1-fast-reasoning)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)