# Claude Sonnet 4.5 Thinking vs GPT-5.1-Codex

> Side-by-side benchmark comparison for Claude Sonnet 4.5 Thinking and GPT-5.1-Codex across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-sonnet-4-5-thinking-vs-gpt-5-1-codex
- 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: Claude Sonnet 4.5 Thinking and GPT-5.1-Codex 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.
- GPT-5.1-Codex has the larger published context window at 400K.

## Model Snapshot

| Property | Claude Sonnet 4.5 Thinking | GPT-5.1-Codex |
|----------|----------|----------|
| Creator | Anthropic | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 200K | 400K |
| Independent public score (not head-to-head) | null | 51.62 |
| Benchmarks Covered | 1 | 3 |
| Pricing (input/output) | N/A | $1.25 / $10.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Claude Sonnet 4.5 Thinking public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 51.4 (Estimated · #54/151)

| Benchmark | Claude Sonnet 4.5 Thinking | GPT-5.1-Codex | Winner |
|-----------|-----------|-----------|--------|
| Gert Labs | Coming soon | 49.68% | Coming soon |
| JobBench | Coming soon | 26.2% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Claude Sonnet 4.5 Thinking public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 47.4 (Estimated · #89/183)

| Benchmark | Claude Sonnet 4.5 Thinking | GPT-5.1-Codex | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 22.62% | 13.12% | Claude Sonnet 4.5 Thinking |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Claude Sonnet 4.5 Thinking public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 66.8 (Unranked · 1 rankable row)

### Reasoning

- Winner: Insufficient shared evidence
- Claude Sonnet 4.5 Thinking public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 70.6 (Unranked · 2 rankable rows)

### Knowledge

- Winner: Insufficient shared evidence
- Claude Sonnet 4.5 Thinking public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 53.3 (Estimated · #69/181)

### Instruction Following

- Winner: Insufficient shared evidence
- Claude Sonnet 4.5 Thinking public-lane score: Coming soon
- GPT-5.1-Codex public-lane score: 85.3 (#42/120)

## FAQ

### Is there enough evidence to pick between Claude Sonnet 4.5 Thinking and GPT-5.1-Codex?

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

- [Claude Sonnet 4.5 Thinking vs Claude Sonnet 4.5](/compare/claude-sonnet-4-5-vs-claude-sonnet-4-5-thinking)
- [GPT-5.1-Codex vs Claude Sonnet 4.5](/compare/claude-sonnet-4-5-vs-gpt-5-1-codex)
- [Claude Sonnet 4.5 Thinking vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-claude-sonnet-4-5-thinking)
- [GPT-5.1-Codex vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-gpt-5-1-codex)

## Explore More

- [Claude Sonnet 4.5 Thinking profile](/models/claude-sonnet-4-5-thinking)
- [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)