# Span-01

> Span-01 is a behavior-scoring classifier from Respan, a 4B model trained with RLAIF on classification reasoning rather than fixed taxonomies. Send a conversation span and a set of plain-language behavior definitions and get a present / absent / not_observable probability per behavior in a single forward pass, with no token-by-token generation. It is the full tier of the family; Span-01 Lite is the lighter tier. Call POST /api/v1/decisions (POST /api/v1/systemone is the same handler).

**ID**: `respan/span-01`  
**Creator**: respan  
**Category**: text  
**Context**: Not published  
**Pricing**: $0.02 / $0 per 1M · billed by your provider (BYOK)  
**Released**: 2026-09-26  
**Web page**: https://anyrouter.dev/model/respan/span-01

**Input modalities**: text  
**Output modalities**: text  

**Capabilities**: systemone, noul-only

**Supported parameters**: state, model, questions

## Usage

**Endpoint**: `POST https://anyrouter.dev/api/v1/decisions`

```bash
curl https://anyrouter.dev/api/v1/decisions \
  -H "Authorization: Bearer $ANYROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "state": "Help! My payouts have been failing for 3 days.",
  "model": "respan/span-01",
  "questions": {
    "is_urgent": {
      "type": "noul",
      "instructions": "Does this convey urgency?"
    }
  }
}'
```

Decisions is not chat: send `state` and typed `questions` (noul / choice / score). Requires a BYOK key for TypeSafe, LLM Gateway, Vercel AI Gateway, AIHubMix, AutoJev, or Fastino.

## Providers

| Provider | Input | Output |
| --- | --- | --- |
| openrouter-byok | $0.02/M (list) | $0 (list) |
| hue | $0 | $0 |

BYOK routes are billed by your own provider key — AnyRouter charges $0. Rates marked (list) are the provider's published list price.

## Source

- Upstream docs: https://openrouter.ai/respan/span-01