# Julia 1

Julia 1 is Supersonic Labs' first open-weights decision model: a 144M-parameter multilingual encoder that answers typed yes/no, choice and score questions about a piece of state in one forward pass. It is built for classification and routing over options you supply, and is most accurate when every option carries a short descriptive sentence. Its published context window is 8,192 tokens. The advertised input rate is $0.025 per million input tokens. The advertised output rate is $0.00 per million output tokens.

- Model identifier: ` supersoniclabs/julia-1 `
- Creator: Supersonic Labs
- Providers: Impossibl
- Model type: Evaluation
- Canonical model page: [Julia 1](<https://impossibl.com/supersoniclabs/julia-1>)
- API availability: Listed as serving through Impossibl.
- Creator release date: 2026-09-23

## Providers

Impossibl hosts Julia 1. Impossibl routes your request intelligently and handles failover automatically when a provider is down.

| Provider | Endpoint location | Routes | Verified context window | Tool calling |
| --- | --- | --- | --- | --- |
| Impossibl | Not specified | 1 | Not verified | Not supported |

The model price applies whichever provider serves the request. Endpoint locations do not guarantee inference residency.

## Specs and Capabilities

- Context window: 8,192 tokens
- Maximum output tokens: Not published in the public catalog; this is separate from the context window.
- Inputs: text
- Outputs: typed answers with probabilities
- Tool calling: Not supported

## API access

Use ` supersoniclabs/julia-1 ` as the model identifier through the Impossibl API.

Published API endpoints:

- ` /v1/systemone `

[API quickstart](<https://impossibl.com/docs/agent-quickstart>) · [Models and billing documentation](<https://impossibl.com/docs/models>)

## Published API prices

All rates are in USD. An unpublished rate is unknown, not zero. Workspace-specific pricing, taxes, balance-purchase fees, billing adjustments, and tool charges can affect the amount paid.

| Usage | Published base rate | Billing unit |
| --- | --- | --- |
| Input | $0.025 | per million input tokens |
| Output | $0.00 | per million output tokens |
| Cache read | Not published | per million cached input tokens |
| Cache write (default retention) | Not published | per million tokens |
| Cache write (one-hour retention) | Not published | per million tokens |
| Audio input | Not published | per million audio input tokens |

## Availability and retirement

The model is listed as serving. No retirement is announced in the current public catalog.

## Frequently asked questions

### What is Julia 1?

Julia 1 is Supersonic Labs' first open-weights decision model: a 144M-parameter multilingual encoder that answers typed yes/no, choice and score questions about a piece of state in one forward pass. It is built for classification and routing over options you supply, and is most accurate when every option carries a short descriptive sentence.

Sources: [Julia 1 model card](<https://huggingface.co/SupersonicLabs/Julia-1>); [mmBERT-small base model card](<https://huggingface.co/jhu-clsp/mmBERT-small>)

### How much does Julia 1 cost?

Julia 1 costs $0.025 per million input tokens and $0.00 per million output tokens through the Impossibl API. All rates are in USD.

### What is the context length of Julia 1?

Julia 1 has a 8,192-token context window through the Impossibl API.

### Does Julia 1 support tool calling?

No. Julia 1 does not support tool calling through the Impossibl API.

### What inputs and outputs does Julia 1 support?

Julia 1 accepts text as input. Julia 1 returns typed answers with probabilities.

### How do I use Julia 1 through an API?

Julia 1 is available through the Impossibl API. Use supersoniclabs/julia-1 as the model identifier with /v1/systemone. The quickstart explains how to create an API key and send your first request.

### When was Julia 1 released?

Supersonic Labs released Julia 1 on September 23, 2026.

Sources: [Creator release announcement](<https://huggingface.co/SupersonicLabs/Julia-1/commits/main>)

## Sources and related links

Prices, limits, capabilities, endpoints, and availability come from the public Impossibl catalog. Creator documentation supplies descriptions and release dates where available; it does not override the published API offering.

- [Public Impossibl model catalog](<https://api.impossibl.com/v1/models>)
- [Full model directory as JSON](<https://impossibl.com/models.json>)
- [Julia 1: model details and pricing](<https://impossibl.com/supersoniclabs/julia-1>)
- [Model directory](<https://impossibl.com/models>)
- [Julia 1 model card](<https://huggingface.co/SupersonicLabs/Julia-1>)
- [mmBERT-small base model card](<https://huggingface.co/jhu-clsp/mmBERT-small>)