# Decision Models

> Low-cost hosted decision models for routing, classification and scoring. One Jev-compatible API, with Peer-to-Peer and EU tiers.

Sign in with a one-time email link or with Google at https://decisionmodels.io/login, create an API key in your dashboard and use a free allowance by invitation or top up from EUR 1. Prepaid credit top-ups use Stripe with invoices. Private individuals and businesses worldwide can sign up and top up. Taxes are shown in checkout before you pay.

## Models and launch pricing
s1-fast (Plumb-4B, text): Peer-to-Peer $0.032 / EU $0.034 per 1M input tokens; output tokens free.
s1-pro (Surogate Rune 26B-A4B v3 (EU) · Winnow-12B Q8 fallback; Rune available on Peer-to-Peer when capacity permits, text): Peer-to-Peer $0.038 / EU $0.040 per 1M input tokens; output tokens free.
s1-vision (Surogate Rune 26B-A4B v3 (EU) · no image fallback on EU tier or Peer-to-Peer without worldwide opt-in; Rune available on Peer-to-Peer when capacity permits; Gemma 4 12B image fallback only for Peer-to-Peer keys with worldwide opt-in, text + image) · text only: Peer-to-Peer $0.038 / EU $0.040 per 1M input tokens; output tokens free.
s1-llm-auto-router (s1-llm-auto-router (CPU routing classifier), text): Peer-to-Peer $0.001 / EU $0.001 per 1M input tokens; output tokens free.
s1-vision with image (requests containing one image, price book S1-LAUNCH-3-IMAGE): Peer-to-Peer $0.217 / EU $0.228 per 1M input tokens; all input tokens of the request (text and image tokens) are billed at this rate; output tokens free. Text-only s1-vision requests use the s1-pro rate.
Image input: s1-vision only, exactly one PNG/JPEG/WebP image per request (data URL or public HTTPS URL); an image is billed as the input tokens the model reads. A request that contains an image is billed at the s1-vision image rate (price book S1-LAUNCH-3-IMAGE) for all its input tokens (text and image tokens), because image processing takes about 3x the GPU time per token of a text request; text-only s1-vision requests use the s1-pro rate. USD rates exclude applicable taxes. EUR rates are published at https://decisionmodels.io/pricing.
Maximum input per request (context window): 4,096 input tokens for s1-fast, 32,000 for s1-pro and 32,000 for s1-vision (state, all questions and options, and the image, counted by the model tokenizer); larger requests get HTTP 400 invalid_request, are never truncated and are not billed. s1-llm-auto-router reads at most 512 tokens and ignores the rest. Details: https://decisionmodels.io/models#input-limits

## Tiers and data
API gateway and database: Hetzner in the EU. EU inference: UpCloud in the EU. EU-tier s1-pro and s1-vision requests run on Surogate Rune 26B-A4B v3; Winnow-12B Q8 is the fallback for s1-pro (text) and also serves the Peer-to-Peer tier. s1-vision has no fallback on the EU tier or on Peer-to-Peer without worldwide opt-in: if Rune is unavailable it returns a retryable 503 (model_unavailable). Peer-to-Peer keys with worldwide processing opt-in may be served by on-demand worldwide GPUs running the Gemma 4 12B image implementation when capacity is busy. s1-fast (Plumb-4B) runs on a batched engine that processes concurrent requests together, so probabilities for identical requests can differ slightly. Peer-to-Peer first uses spare EU capacity, with EU requests taking priority. When busy, Peer-to-Peer may use on-demand GPU capacity rented through Lium (lium.io), operated by independent third-party providers in various countries, including outside the EU/EEA. This happens only for keys with “Allow worldwide processing” enabled. Without opt-in, Peer-to-Peer stays on EU capacity and may be queued or rejected when busy. Existing customers keep EU-only processing unless they opt in. Request and response content is not stored on any node. EU-tier inference always stays in the EU. Connections are encrypted and authenticated. Prompts and outputs are never used for training. New content sub-processors remain subject to the 30-day notice and objection process. Do not send personal data on opted-in worldwide keys unless an adequate transfer basis applies for your use. See the DPA and sub-processor list.

## API and MCP
API base: https://api.decisionmodels.io
POST /v1/systemone: model, state, and up to three typed text questions for s1-pro, or one for s1-fast and s1-vision (noul, choice or score).
GET /v1/models (alias /models): live model registry.
Authenticate inference with Authorization: Bearer <API key>; choose S1-Region: global|eu.
Hosted MCP: https://api.decisionmodels.io/mcp (streamable HTTP, JSON-RPC; Bearer API key). Tools: decide, list_models, get_usage, get_balance.
Swagger UI: https://decisionmodels.io/docs/api/reference
OpenAPI snapshot: https://decisionmodels.io/openapi.json
Authoritative API OpenAPI: https://api.decisionmodels.io/openapi.json

## Resources
- [llms.txt](https://decisionmodels.io/llms.txt)
- [llms-full.txt](https://decisionmodels.io/llms-full.txt)
- [Sign in and create a key](https://decisionmodels.io/login?next=/dashboard)
- [Quickstart](https://decisionmodels.io/docs/quickstart)
- [API reference (Swagger UI)](https://decisionmodels.io/docs/api/reference)
- [OpenAPI JSON](https://decisionmodels.io/openapi.json)
- [Hosted MCP setup](https://decisionmodels.io/mcp)
- [Models](https://decisionmodels.io/models)
- [Launch pricing](https://decisionmodels.io/pricing)
- [EU tier](https://decisionmodels.io/eu)
- [Agent guide](https://decisionmodels.io/agents)
- [DPA](https://decisionmodels.io/legal/dpa)
- [Sub-processors](https://decisionmodels.io/legal/subprocessors)
- [Security](https://decisionmodels.io/security)