Claude Code Router with Nadir

Prompt-aware model choice for Claude Code Router (CCR), as a route script. CCR already sends Claude Code to the providers you configure. The script adds one question before each request whose model is auto: is this turn simple, medium or complex? CCR then sends it to the model you picked for that tier.

Nadir only returns the tier. Your provider keys stay in CCR and the completion never passes through Nadir.

Setup

1. Save the script

Save this as nadir.js in your CCR config directory. CCR runs route scripts in a sandboxed worker and passes the request summary as input.

// CCR Node.js route script body. Configure the environment before enabling.
// API contract: https://getnadir.com/docs/decision-api
if (api.env("CCR_NADIR_ROUTING_ENABLED") !== "1" || input.model !== "auto") return null;
if (input.summary.hasImage || !input.summary.lastUserText.trim()) return null;
const simple = api.env("CCR_NADIR_SIMPLE_MODEL");
const complex = api.env("CCR_NADIR_COMPLEX_MODEL");
if (!simple || !complex) return null;
// Without a medium model, medium prompts go to the complex model.
const targets = { simple, medium: api.env("CCR_NADIR_MEDIUM_MODEL") || complex, complex };
const key = api.env("NADIR_API_KEY");
const base = (api.env("CCR_NADIR_BASE_URL") || "https://api.getnadir.com").replace(/\/+$/, "").replace(/\/v1$/, "");
try {
  const response = await api.fetch(base + "/v1/bucket", {
    method: "POST",
    headers: { "content-type": "application/json", ...(key ? { "x-api-key": key } : {}) },
    body: JSON.stringify({ prompt: input.summary.lastUserText.slice(0, 8192), source: "claude-code-router" })
  });
  if (!response.ok) return null;
  const bucket = JSON.parse(response.body)?.bucket;
  if (typeof bucket !== "string" || !Object.hasOwn(targets, bucket)) return null;
  return { model: targets[bucket] };
} catch {
  return null;
}

2. Set the environment

Set these where CCR starts. Model values use CCR's provider/model form and must be models you have already configured in CCR.

export CCR_NADIR_ROUTING_ENABLED=1
export CCR_NADIR_SIMPLE_MODEL=deepseek/deepseek-chat
export CCR_NADIR_MEDIUM_MODEL=openrouter/anthropic/claude-sonnet-4.6   # optional
export CCR_NADIR_COMPLEX_MODEL=openrouter/anthropic/claude-opus-4.6
export NADIR_API_KEY=ndr_...                                          # optional

3. Add the rule

In CCR's Routing page, add a Node.js script rule, select nadir.js, and start with a 1500 ms timeout. Put a static rule for auto after it, so a request the script skips still has a model.

Then point Claude Code at CCR with the model auto. Request logs show the resolved model per turn.

Behavior

• Only requests whose model is auto are classified. A model named explicitly is never changed.
• Without CCR_NADIR_MEDIUM_MODEL, medium turns go to the complex model.
• Images, empty turns, missing configuration, an unknown tier, an error or a timeout all return no decision, and CCR moves on to the next rule. The script fails open.
• The script sends up to 8,192 characters of the latest user message and nothing else: no headers, system prompt, tools or earlier turns.

With or without a key

Without NADIR_API_KEY the script uses the free anonymous tier of api.getnadir.com. It is rate-limited per IP and keeps no per-request record, only aggregate counts. With a key, decisions appear in your Nadir dashboard. CCR_NADIR_BASE_URL points the script at a self-hosted Nadir deployment instead; a trailing /v1 is stripped.

See the Decision API for the full contract.