Dari Auto Router

The Dari Auto Router is a hosted routing policy. Instead of writing your own selector, you send Dari the candidates and the conversation — Dari’s routing model picks the best model for each turn and bills your org per call.

The Auto Router is a paid service. You need a Dari API key with billing enabled. Self-hosted routing without the Auto Router is free and works without any network calls — use a custom policy instead.

Quickstart

Drop createAutoRouter into createRouter as the policy. That’s it.

import { createAutoRouter, createPiRuntime, createRouter } from "@dari/router-core";

const pi = await createPiRuntime({
  apiKey: ({ provider }) => {
    const key = process.env[`${provider.toUpperCase()}_API_KEY`];
    if (!key) throw new Error(`Missing ${provider.toUpperCase()}_API_KEY`);
    return key;
  },
});

const router = createRouter({
  models: [
    pi.model("openai/gpt-5.6-sol"),
    pi.model("anthropic/claude-sonnet-5"),
  ],
  policy: createAutoRouter({ apiKey: process.env.DARI_API_KEY! }),
  runtime: pi,
});

const response = await router.fetch(
  new Request("https://your-app/v1/chat/completions", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({
      model: "dari/routing",
      messages: [{ role: "user", content: "Write a palindrome function" }],
    }),
  }),
);

The apiKey resolver receives { provider, model, api, purpose }, so one runtime can serve every declared provider. pi.model() fills in each model’s capabilities from Pi’s catalog — see Models.

How It Works

Every request goes through three phases — the first two run locally, only the selection call hits Dari:

Prepare

Router Core narrows your models to compatible candidates based on capabilities, tools, and request shape. This runs in your process.

Select

The Auto Router sends the candidates and conversation to https://routing.dari.dev/v1/auto-router/select. Dari’s routing model evaluates them and returns a decision. This is the only network call — it’s one HTTP request per turn.

Execute

Router Core dispatches the selected model to your executor (Pi runtime or custom). The response flows back through the same protocol.

What The Selection Call Contains

The selection call carries no provider credentials — Dari never sees your model API keys. It does receive the conversation text verbatim: system prompts, user and assistant turns, tool arguments and results, and readable reasoning text are all part of the selector input, alongside the candidate list, eval scores, and cost estimates. Before the call, image bytes are replaced with an <image omitted> placeholder and encrypted reasoning continuations are stripped. Request metadata, user, and prompt_cache_key never leave your process. The anonymous selection protocol hides model names from the routing policy — it does not hide conversation content from Dari.

Leases

The Auto Router supports multi-turn leases. When the routing model commits to a model for N turns, the decision includes leaseTurnsRemaining and Router Core skips the selection call for subsequent turns in the same conversation.

How leases work

Turn 1: The Auto Router selects gpt-5.6-sol/high with a 10-turn lease.
Turns 2–10: Router Core serves the same model without calling Dari. You’re not billed for these turns.
Turn 11: The lease expires. The Auto Router evaluates the conversation again and may pick a different model or renew.

Leases are managed automatically — no configuration needed. The routing model decides whether to lease based on conversation context. Lease state lives in createRouter’s lease store — in-memory by default; pass a leaseStore to share leases across processes. On ephemeral or replicated hosts (Cloud Run, Lambda), use a shared store: every lease lost to a cold start is a billed re-selection on the next turn — see Serverless Deployments.

Lease short-circuiting requires a prompt_cache_key on your requests so Router Core can correlate turns within a conversation. Without it, every turn calls /select and leases are reported on each decision but not skipped.

Thinking Traces

The routing model’s reasoning is included in the response as a thinking field. It’s accessible from the routing decision’s details:

const selection = await router.select(request);
const details = selection.policyDetails as { selectorOutput: string };
const parsed = JSON.parse(details.selectorOutput);
console.log(parsed.thinking); // "I chose gpt-5.6-sol because the request needs deep reasoning..."

Configuration

createAutoRouter accepts all options that createDariRoutingPolicy accepts, except selector, runtime, selectorModel, and selectorContextWindowChars (those are managed by the Auto Router) and strategy/customConfig. Custom routing rules are rejected with a configuration error — the hosted Auto Router serves only the default policy. For custom rules, self-host the selector with createDariRoutingPolicy or use the managed platform.

createAutoRouter({
  apiKey: process.env.DARI_API_KEY!,
  endpoint: "https://routing.dari.dev/v1/auto-router", // default; override for testing
  pricing: (model) => modelPricing[model],          // your model pricing for cost estimation
  evals: yourEvals,                                 // optional benchmark evals
})

The endpoint defaults to https://routing.dari.dev/v1/auto-router. Override it for local development or testing — the client appends /select, and tolerates an endpoint pasted with a trailing slash or /select already on it. To build a compatible endpoint, decode the POSTed body with the exported decodeUntrustedSelectorRequest() wire codec.

Pricing

The Auto Router bills per selection call. Each call to the /select endpoint counts as one billable event, regardless of how many candidates are evaluated or how many tokens the conversation contains (max 8k tokens per call). Usage appears in your Dari dashboard under the dari/auto-router model with provider dari.

When To Use The Auto Router

Use Auto Router

You want Dari’s routing intelligence without managing a selector model. You’re fine with one network call per turn (or fewer, with leases).

Use A Custom Policy

You want full control over model selection, need offline routing, or have domain-specific rules that don’t require an LLM selector.

Use The Managed Platform

You want Dari to host everything — routing, execution, billing, and telemetry. No self-hosting required.

Get Started

Build A Router

Advanced

Dari Auto Router

Quickstart

How It Works

What The Selection Call Contains

Leases

Thinking Traces

Configuration

Pricing

When To Use The Auto Router

Use Auto Router

Use A Custom Policy

Use The Managed Platform

​Quickstart

​How It Works

​What The Selection Call Contains

​Leases

​Thinking Traces

​Configuration

​Pricing

​When To Use The Auto Router

Use Auto Router

Use A Custom Policy

Use The Managed Platform

Quickstart

How It Works

What The Selection Call Contains

Leases

Thinking Traces

Configuration

Pricing

When To Use The Auto Router