The AI arena is free today

Open Superagent

Claude Sonnet 4.5 vs GPT OSS 120B

Claude Sonnet 4.5 and GPT OSS 120B are closely matched at 32.1 and 28.8 on the LLM Stats Score. GPT OSS 120B is 85.4x cheaper per token.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Sonnet 4.5 and GPT OSS 120B are closely matched on the overall LLM Stats Score at 32.1 and 28.8.

In the 2 individual benchmarks reported for both models, Claude Sonnet 4.5 wins 2; this is a narrower head-to-head signal than the composite indexes.

On price, GPT OSS 120B is roughly 85.4x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Sonnet 4.5 also accepts a larger context window (200,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Sonnet 4.5

  • your work emphasizes reasoning — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 2 of 2 exact shared results
  • you process long inputs — it offers a 200,000 token context window
  • you want the most recent training data — it shipped Sep 2025

Choose GPT OSS 120B

  • cost matters — it's about 85.4x cheaper per token
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Sonnet 4.5
Anthropic
GPT OSS 120B
OpenAI
Core performance indexes
LLM Stats Score
32.1
#107
28.8
#132
Reasoning
31.3
#108
23.0
#166
Cost, coverage & limits
Benchmark wins
2 of 2
0 of 2
Input price
$3.00 / M
$0.04 / M
Output price
$15.00 / M
$0.17 / M
Context window
200,000
131,072

Capability indexes

Additional strengths measured across groups of related public benchmarks

1 shared
Index
Claude Sonnet 4.5
GPT OSS 120B
Math
25.0#115
23.3#131
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

9 reported for Claude Sonnet 4.5 · 7 for GPT OSS 120B

2 shared

Claude Sonnet 4.5 outperforms in 2 benchmarks (GPQA, TAU-bench Retail), while GPT OSS 120B is better at 0 benchmarks.

Claude Sonnet 4.5 significantly outperforms across most benchmarks.

Mon Sep 21 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

GPT OSS 120B costs less

For input processing, Claude Sonnet 4.5 ($3.00/1M tokens) is 81.1x more expensive than GPT OSS 120B ($0.04/1M tokens).

For output processing, Claude Sonnet 4.5 ($15.00/1M tokens) is 88.2x more expensive than GPT OSS 120B ($0.17/1M tokens).

In conclusion, Claude Sonnet 4.5 is more expensive than GPT OSS 120B.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Mon Sep 21 2026 • llm-stats.com
Anthropic
Claude Sonnet 4.5
Input tokens$3.00
Output tokens$15.00
Best providerAnthropic
OpenAI
GPT OSS 120B
Input tokens$0.04
Output tokens$0.17
Best providerDeepinfra
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Claude Sonnet 4.5 accepts 200,000 input tokens compared to GPT OSS 120B's 131,072 tokens. GPT OSS 120B can generate longer responses up to 131,072 tokens, while Claude Sonnet 4.5 is limited to 64,000 tokens.

Anthropic
Claude Sonnet 4.5
Input200,000 tokens
Output64,000 tokens
OpenAI
GPT OSS 120B
Input131,072 tokens
Output131,072 tokens
Mon Sep 21 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Sonnet 4.5 supports multimodal inputs, whereas GPT OSS 120B does not.

Claude Sonnet 4.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Sonnet 4.5

Text
Images
Audio
Video

GPT OSS 120B

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Sonnet 4.5 is licensed under a proprietary license, while GPT OSS 120B uses Apache 2.0.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Sonnet 4.5

Proprietary

Closed source

GPT OSS 120B

Apache 2.0

Open weights

Release Timeline

When each model was launched

Claude Sonnet 4.5 was released on 2025-09-29, while GPT OSS 120B was released on 2025-08-05.

Claude Sonnet 4.5 is 2 months newer than GPT OSS 120B.

Claude Sonnet 4.5

Sep 29, 2025

11 months ago

1mo newer
GPT OSS 120B

Aug 5, 2025

1.1 years ago

Knowledge Cutoff

When training data ends

Claude Sonnet 4.5 has a documented knowledge cutoff of 2025-01-31, while GPT OSS 120B's cutoff date is not specified.

We can confirm Claude Sonnet 4.5's training data extends to 2025-01-31, but cannot make a direct comparison without GPT OSS 120B's cutoff date.

Claude Sonnet 4.5

Jan 2025

GPT OSS 120B

—

Provider Availability

Claude Sonnet 4.5 is available from Anthropic. GPT OSS 120B is available from DeepInfra, Novita, OpenAI, Fireworks, Groq.

Claude Sonnet 4.5

anthropic logo
Anthropic
Input Price:Input: $3.00/1MOutput Price:Output: $15.00/1M

GPT OSS 120B

deepinfra logo
Deepinfra
Input Price:Input: $0.04/1MOutput Price:Output: $0.17/1M
novita logo
Novita
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
openai logo
OpenAI
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
fireworks logo
Fireworks
Input Price:Input: $0.15/1MOutput Price:Output: $0.60/1M
groq logo
Groq
Input Price:Input: $0.15/1MOutput Price:Output: $0.60/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Sonnet 4.5 and GPT OSS 120B side-by-side, then vote on the output you prefer.

Claude Sonnet 4.5
✓ Preferred
GPT OSS 120B
Open in Playground

FAQ

Common questions about Claude Sonnet 4.5 vs GPT OSS 120B.

Which is better, Claude Sonnet 4.5 or GPT OSS 120B?

Claude Sonnet 4.5 and GPT OSS 120B are closely matched on the LLM Stats Score at 32.1 and 28.8. Claude Sonnet 4.5 is made by Anthropic and GPT OSS 120B is made by OpenAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Sonnet 4.5 compare to GPT OSS 120B in benchmarks?

Claude Sonnet 4.5 scores MMMLU: 89.1%, AIME 2025: 87.0%, TAU-bench Retail: 86.2%, GPQA: 83.4%, MMMUval: 77.8%. GPT OSS 120B scores MMLU: 90.0%, CodeForces: 82.1%, GPQA: 80.1%, TAU-bench Retail: 67.8%, HealthBench: 57.6%.

Is Claude Sonnet 4.5 cheaper than GPT OSS 120B?

GPT OSS 120B is 81.1x cheaper for input tokens. Claude Sonnet 4.5 costs $3.00/M input and $15.00/M output via anthropic. GPT OSS 120B costs $0.04/M input and $0.17/M output via deepinfra.

What are the context window sizes for Claude Sonnet 4.5 and GPT OSS 120B?

Claude Sonnet 4.5 supports 200K tokens and GPT OSS 120B supports 131K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Sonnet 4.5 and GPT OSS 120B?

Key differences include LLM Stats Score (32.1 vs 28.8), context window (200K vs 131K), input pricing ($3.00 vs $0.04/M), multimodal support (yes vs no), licensing (Proprietary vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 4.5 and GPT OSS 120B?

Claude Sonnet 4.5 is developed by Anthropic and GPT OSS 120B is developed by OpenAI.

Related comparisons