Model Comparison
GPT-5.6 Terra vs GPT OSS 20BWhich is better in 2026?
GPT-5.6 Terra significantly outperforms across most benchmarks. GPT OSS 20B is 64.3x cheaper per token.
Verdict: GPT-5.6 Terra vs GPT OSS 20B — which is better?
GPT-5.6 Terra (by OpenAI) and GPT OSS 20B (by OpenAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.
GPT-5.6 Terra outperforms in 3 benchmarks (GPQA, HealthBench, HealthBench Hard), while GPT OSS 20B is better at 0 benchmarks. GPT-5.6 Terra significantly outperforms across most benchmarks.
On price, GPT OSS 20B is roughly 64.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.6 Terra also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.
Choose GPT-5.6 Terra if…
- you want the strongest raw capability — it leads on 3 of 3 shared benchmarks
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Jul 2026
Choose GPT OSS 20B if…
- cost matters — it's about 64.3x cheaper per token
- you need open weights you can self-host or fine-tune
Performance Benchmarks
Comparative analysis across standard metrics
GPT-5.6 Terra outperforms in 3 benchmarks (GPQA, HealthBench, HealthBench Hard), while GPT OSS 20B is better at 0 benchmarks.
GPT-5.6 Terra significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.6 Terra ($2.50/1M tokens) is 50.0x more expensive than GPT OSS 20B ($0.05/1M tokens).
For output processing, GPT-5.6 Terra ($15.00/1M tokens) is 75.0x more expensive than GPT OSS 20B ($0.20/1M tokens).
In conclusion, GPT-5.6 Terra is more expensive than GPT OSS 20B.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.6 Terra accepts 1,050,000 input tokens compared to GPT OSS 20B's 131,072 tokens. GPT-5.6 Terra can generate longer responses up to 128,000 tokens, while GPT OSS 20B is limited to 32,768 tokens.
Input Capabilities
Supported data types and modalities
GPT-5.6 Terra supports multimodal inputs, whereas GPT OSS 20B does not.
GPT-5.6 Terra can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-5.6 Terra
GPT OSS 20B
License
Usage and distribution terms
GPT-5.6 Terra is licensed under a proprietary license, while GPT OSS 20B uses Apache 2.0.
License differences may affect how you can use these models in commercial or open-source projects.
Proprietary
Closed source
Apache 2.0
Open weights
Release Timeline
When each model was launched
GPT-5.6 Terra was released on 2026-07-09, while GPT OSS 20B was released on 2025-08-05.
GPT-5.6 Terra is 11 months newer than GPT OSS 20B.
Jul 9, 2026
2 weeks ago
11mo newerAug 5, 2025
11 months ago
Knowledge Cutoff
When training data ends
GPT-5.6 Terra has a documented knowledge cutoff of 2026-02-16, while GPT OSS 20B's cutoff date is not specified.
We can confirm GPT-5.6 Terra's training data extends to 2026-02-16, but cannot make a direct comparison without GPT OSS 20B's cutoff date.
Feb 2026
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Provider Availability
GPT-5.6 Terra is available from OpenAI. GPT OSS 20B is available from Novita, Fireworks, Groq, OpenAI.
GPT-5.6 Terra
GPT OSS 20B
Outputs Comparison
Key Takeaways
GPT OSS 20B
View detailsOpenAI
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against GPT-5.6 Terra and GPT OSS 20B side-by-side, then vote on the output you prefer.
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FAQ
Common questions about GPT-5.6 Terra vs GPT OSS 20B.