AI model comparison
GPT-5.1-Codex vs Claude Sonnet 4.5
Pricing, context window, benchmarks, and features compared side by side. Or skip the guesswork and send one prompt to both.
OpenAI
GPT-5.1-Codex
GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows.
- Input / 1M
- $1.25
- Output / 1M
- $10
- Context
- 400K
Anthropic
Claude Sonnet 4.5
Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows.
- Input / 1M
- $3
- Output / 1M
- $15
- Context
- 1M
At a glance
Quick verdict
How the two models stack up on the things people ask about most.
Lower price
GPT-5.1-Codex
1.8x cheaper for a typical chat
Higher intelligence score
GPT-5.1-Codex
23.7 vs 20.7 on Artificial Analysis
Larger context window
Claude Sonnet 4.5
1M vs 400K tokens
Newer release
GPT-5.1-Codex
Released November 13, 2025
Benchmarks
Benchmark scores
Independent scores from Artificial Analysis. Higher is better.
Intelligence index
GPT-5.1-Codex23.7Claude Sonnet 4.520.7Coding index
GPT-5.1-CodexNot availableClaude Sonnet 4.552.1Agentic index
GPT-5.1-CodexNot availableClaude Sonnet 4.515.8Pricing
GPT-5.1-Codex vs Claude Sonnet 4.5 API pricing
Per-token API rates. Cheaper option highlighted.
| Metric | GPT-5.1-Codex | Claude Sonnet 4.5 |
|---|---|---|
| Input tokensPer 1M tokens | $1.25 | $3 |
| Output tokensPer 1M tokens | $10 | $15 |
| Cached input (read)Per 1M tokens | $0.13 | $0.30 |
| Cache writePer 1M tokens | Not available | $3.75 |
| Long-context pricingPer 1M tokens, for very long prompts | Same rate at any length | $6 in / $22.50 out above 200K |
| Web searchPer request | $0.01 | $0.01 |
What it costs in practice
Estimated cost per 1,000 requests at standard rates. Coding and long-document figures also show the cost when the input is already cached.
Chat message
2K in, 500 out
GPT-5.1-Codex$7.50Claude Sonnet 4.5$13.50Coding task
30K in, 4K out
GPT-5.1-Codex$77.50$43.90 cachedClaude Sonnet 4.5$150$69 cachedLong document summary
150K in, 2K out
GPT-5.1-Codex$207.50$39.50 cachedClaude Sonnet 4.5$480$75 cachedSpecs
Context window and capabilities
How much each model can read, how much it can write, and what it accepts as input.
| Metric | GPT-5.1-Codex | Claude Sonnet 4.5 |
|---|---|---|
| Context window | 400K tokens | 1M tokens |
| Max output | 128K tokens | 64K tokens |
| Input types | Image, Text | File, Image, Text |
| Output types | Text | Text |
| Reasoning effort levels | High, Medium, Low | Not available |
| Default reasoning effort | Medium | Not available |
| Release date | November 13, 2025 | September 29, 2025 |
Features
Supported features
API features available for each model.
| Metric | GPT-5.1-Codex | Claude Sonnet 4.5 |
|---|---|---|
| Tool calling | Supported | Supported |
| Structured outputs | Supported | Supported |
| JSON mode | Supported | Supported |
| Reasoning | Supported | Supported |
| Temperature | Not supported | Supported |
| Stop sequences | Not supported | Supported |
| Deterministic seed | Supported | Not supported |
| Verbosity control | Supported | Not supported |
Keep exploring
More on these models
Other head-to-heads, the full model page, and the alternatives list for each model.
GPT-5.1-CodexView full model details- GPT-5.1-Codex vs GPT-5.2
- GPT-5.1-Codex vs GPT-5.2-Codex
- GPT-5.1-Codex vs Gemini 3 Flash Preview
- GPT-5.1-Codex vs GPT-5.1
- GPT-5.1-Codex vs DeepSeek V4 Flash 0423
- GPT-5.1-Codex vs GPT-5.4 Mini
- GPT-5.1-Codex vs GPT-5
- GPT-5.1-Codex vs Claude Opus 4.1
- GPT-5.1-Codex vs o3 Pro
- GPT-5.1-Codex vs GPT-5 Mini
- GPT-5.1-Codex vs o3
- GPT-5.1-Codex vs Claude Sonnet 4
Claude Sonnet 4.5View full model details- Claude Sonnet 4.5 vs Claude Sonnet 4.6
- Claude Sonnet 4.5 vs Claude Haiku 4.5
- Claude Sonnet 4.5 vs Claude Opus 4.5
- Claude Sonnet 4.5 vs GPT-5.1
- Claude Sonnet 4.5 vs Gemini 2.5 Pro
- Claude Sonnet 4.5 vs GPT-5
- Claude Sonnet 4.5 vs Claude Opus 4.1
- Claude Sonnet 4.5 vs o3 Pro
- Claude Sonnet 4.5 vs Qwen3.5 397B A17B
- Claude Sonnet 4.5 vs o3
- Claude Sonnet 4.5 vs Claude Sonnet 4
- Claude Sonnet 4.5 vs o1
Our take
GPT-5.1-Codex is 1.8x cheaper for a typical chat. GPT-5.1-Codex scores higher on the Artificial Analysis Intelligence Index (23.7 vs 20.7). Claude Sonnet 4.5 has the larger context window (1M vs 400K tokens). The right pick depends on your workload, so the quickest way to settle it is to send the same prompt to both and compare.
FAQ
Frequently asked questions
Is GPT-5.1-Codex or Claude Sonnet 4.5 cheaper?
GPT-5.1-Codex is cheaper for a typical chat (2K input tokens and 500 output tokens). GPT-5.1-Codex costs $1.25 per 1M input tokens and $10 per 1M output tokens, while Claude Sonnet 4.5 costs $3 per 1M input tokens and $15 per 1M output tokens.
Which has a bigger context window, GPT-5.1-Codex or Claude Sonnet 4.5?
Claude Sonnet 4.5 supports up to 1M tokens of context, compared with 400K for GPT-5.1-Codex.
Is GPT-5.1-Codex smarter than Claude Sonnet 4.5?
On the Artificial Analysis Intelligence Index, GPT-5.1-Codex scores 23.7 and Claude Sonnet 4.5 scores 20.7, putting GPT-5.1-Codex ahead. Benchmarks don't capture everything, so the best test is running your own prompts through both.
Can I use GPT-5.1-Codex and Claude Sonnet 4.5 at the same time?
Yes. Shortcut Chat sends one prompt to multiple models at once, so you can see GPT-5.1-Codex and Claude Sonnet 4.5 answer side by side and keep the better response.
Why choose? Ask both.
Send one prompt to GPT-5.1-Codex and Claude Sonnet 4.5 at the same time. Compare the answers side by side and keep the best one.