# The decision-model route — GreenPT "Metis" (`/v1/systemone`)

The gateway exposes a **decision model** — GreenPT's **Metis** (System One API) —
as a **pass-through route**, not a chat model.

## What it is, and why it is a route and not a model

Metis is a **decision** endpoint, not a chat completion: it takes a `state` plus up
to 32 typed questions and returns **probabilities / choices / scores**. It
generates no text (`output_tokens` is always 0), so **it cannot be a `model_list`
entry** — LiteLLM's chat pipeline has nothing to parse. It is therefore exposed as
a pass-through:

```
path:    /v1/systemone
target:  https://api.greenpt.ai/v1/systemone
auth:    true        # members call it with their normal co-op API key
```

- **It is API-only and deliberately NOT a chat-picker model.** It never appears in
  the chat model list. Do not add it there.
- **Members authenticate with their own co-op key**, never the provider key — the
  route's `Authorization` header injects the provider key server-side.
- Hosted by GreenPT (policy-based privacy, EU, 100% renewable), same
  `GREENPT_API_KEY` the green chat models use.

## Pricing and the metering fix

- **$0.12 per 1M input tokens; output is free.**

Metering is **exact, from the token count GreenPT reports back**. Because Metis is
not a `model_list` entry, it is priced through the
`coop_passthrough_cost_per_token` map, keyed by the route path
(`/v1/systemone: 0.00000012`). `patch_passthrough_token_cost.py` (built into the
image) reads `usage.input_tokens` from the Metis response body at logging time and
writes the exact figure to member spend.

**Why this exists — record it, it will recur:** **generic pass-through routes
originally logged nothing.** A route that is not a `model_list` entry gets no
automatic pricing, so its calls were metered as $0 — a paid feature silently free.
The pass-through accounting had to be fixed so spend lands against the **calling
member's key**. If another pass-through route is ever added, it needs the same
treatment or it bills nothing.

`cost_per_request: 0.0001` on the route is now only a **fallback** — it applies if
a response arrives without a usable token count, so a call is never silently free.
Keep the two in sync.

## Access control gotcha (community edition)

The route is opened to any authenticated member key via
`coop_passthrough_open_to_keys` (consumed at build time by
`patch_passthrough_key_access.py`). **LiteLLM's own gate for `auth=true`
pass-through routes (`allowed_passthrough_routes`) is an Enterprise-only field**,
so on this community-edition proxy it can never be granted to member keys. The
only alternative, `auth: false`, would expose the route publicly and forward the
co-op's GreenPT key to anonymous callers. **Authentication is unchanged** — the
endpoint still requires a valid key.