UltraGPT
OpenAI: gpt-oss-20b
gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for...
Intelligence overview
131.1K tok
Context window
118.0K tok
Max output
What OpenAI: gpt-oss-20b can do.
Reasoning
Extended reasoning
Works through problems step by step before answering, trading latency for accuracy on harder tasks.
Adjustable effort
Choose how much the model deliberates per request — trade speed for depth as the task demands.
Development
Tool calling
Calls external functions mid-response, then continues reasoning from the result.
Structured output
Returns responses constrained to a JSON schema, ready to parse without cleanup.
Streaming
Streams tokens as they're generated instead of waiting on the full response.
Performance
Design Arena — ranked #112 across 2 categories
Pay for what you use.
Every model in UltraGPT runs behind one flat subscription — this is the underlying per-token cost the catalog tracks.
$0.03 / 1M tok
$0.13 / 1M tok
Built for serious work.
Build
Generate and refactor code, with the ability to run and verify tool calls and return structured, parseable output.
Think
Works through hard problems with adjustable reasoning effort — high, medium, low.
Research
Holds up to 131.1K tokens of source material in context without losing the thread.
Automate
Chains tool calls across multi-step workflows, reasoning between each one.
Ask OpenAI: gpt-oss-20b anything.
A preview of the real UltraGPT composer — the model you see here is the model you get.
Continues in the UltraGPT app — one login, every model.
How OpenAI: gpt-oss-20b stacks up.
The closest models in the catalog by provider, capability and score — real entries, pulled from the same directory.
Technical details.
Specification
- Context window
- 131.1K tokens
- Max output
- 118.0K tokens
- Input modalities
- Text
- Output modalities
- Text
- Knowledge cutoff
- Jun 30, 2024
- Release date
- Aug 5, 2025
- Reasoning effort
- high, medium, low (always on)
- Streaming
- Supported
- Tool calling
- Supported
- JSON mode
- Supported
Reasoning
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