Enso

After this page you know how Enso picks a model, how to bound and steer the pick, how to teach it, and which Enso id to send.

Enso is the router. Every request it sees is classified, priced against what your org can serve, and sent to the model that should answer it — a Zen model, another provider's, or one you host. The decision runs on a CPU: HIP-0510 measures 300 ns for the rule router and 12 µs for the learned one, before a model call that takes seconds.

Two ways in

curl -si https://api.hanzo.ai/v1/chat/completions \
  -H "Authorization: Bearer $HANZO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "auto", "messages": [{"role": "user", "content": "Summarize this changelog in one line."}]}'

The rewrite happens before provider, pricing and billing are resolved, so the request is priced, metered and reported as exactly the model that served it. That model is in the X-Routed-Model response header and in the body's model field; the two always match. zen-router is accepted as an alias for auto.

How it picks

1. Classify. Media, length and keywords put the request in one task class: code, reasoning, math, creative, vision, long_context, cheap_chat or general.
2. Narrow. Only models your org can actually serve are eligible — a route exists and your tier or grant admits it — then only the ones your org enabled, then only the ones under your cost ceiling. A narrower scope can only narrow; it never reaches a model another scope could not.
3. Choose, in this order, first answer wins:
   • an override your org pinned for that task class;
   • the learned policy: a bilinear utility xᵀW p over request features and per-model profiles, fit by ridge regression and adapted per user with LinUCB; it defers when it is unsure;
   • an optional exploration share that samples a non-champion model, so every model in the pool keeps earning feedback;
   • the rule table: an ordered list of models per task class, Zen first; the first servable one wins.

With routing on for your org, auto always resolves: when the learned policy is unreachable or unsure, the rule table answers.

Bound it

Two optional headers set a ceiling per request without touching the body:

An org can also set, once: a cost ceiling that fills an unset X-Max-Cost, per-task overrides, the enabled-model list, and the strategy — enso (the learned policy leads; the default) or heuristic (rules only, for routing you can audit line by line). An explicit header always wins when it is lower. Smart routing covers where those switches live.

Teach it

Tell Enso how a routed answer went. The request_id is the response id you already hold (chatcmpl-…):

curl https://api.hanzo.ai/v1/ai/feedback \
  -H "Authorization: Bearer $HANZO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"request_id": "chatcmpl-…", "signal": "accept"}'

The ledger holds features and a reward, never prompt text. A reward can land only on your own org's requests, and an org that turns training contribution off records none. Each cycle fits a candidate, deploys it only if it beats the incumbent on held-out reward, and otherwise keeps the incumbent: a regression cannot ship. Your org's own policy trains on your org's rewards alone.

The Enso family

The managed ids, from the gateway:

curl -s https://api.hanzo.ai/v1/models \
  | jq -r '.data[] | select(.id | startswith("enso")) | "\(.id)\t\(.context_window)\t\(.pricing.input)/\(.pricing.output)"'

Reasoning is the serving catalogue's setting today. Rates and windows are the command's, not this page's: the gateway is the source of truth, and Pricing is generated from it.

Kai inside Enso

Routing is one bounded decision; an agent loop makes many more — how much context, which tool, how much reasoning, whether the step made progress, whether the task is done, whether a command may run. Kai is being built into Enso as the in-process controller for those, one Decision Program each, starting in shadow. Status: in progress.

Also named Enso

Source

The router and learned policy: hanzoai/engine (enso, hanzo-router). The family: hanzoai/enso.

Specification: HIP-0510.

Measurements and economics: the Enso paper.