model-router

1import type { AgentSpawnInput, Register } from 'claude-code'
2
3// subagent type → model; a call that names its own model is left alone
4const ROUTES: Record<string, string> = { Explore: 'haiku', 'general-purpose': 'sonnet' }
5
6export const route = (e: Pick<AgentSpawnInput, 'subagentType' | 'model' | 'fork' | 'workflow'>) =>
7  e.model || e.fork || e.workflow ? undefined : ROUTES[e.subagentType]
8
9// With `/router jev on` and TYPESAFE_API_KEY set, Jev (a System One model) reads a general-purpose
10// task and picks its tier. Its pick wins only when it is confident; a slow,
11// failed or unsure answer keeps the rule's model.
12const JEV_URL = 'https://api.typesafe.ai/v1/systemone'
13const JEV_TIMEOUT_MS = 1500
14export const MIN_CONFIDENCE = 0.8
15// ponytail: the task is cut to its head, so a long prompt is judged by its start
16const MAX_TASK_CHARS = 4000
17
18export const TIERS = {
19  haiku: 'Simple, mechanical work: find or list files, read and summarize a little code, run a command and report, small obvious edits.',
20  sonnet: 'Ordinary engineering: implement a feature, write tests, review code, fix a bug with a clear cause, research across a few files.',
21  opus: 'Hard reasoning: subtle or hard-to-find bugs, large refactors, architecture or design decisions, tricky concurrency, security analysis.',
22} as const
23type Tier = keyof typeof TIERS
24type JevChoice = { choice?: string; confidence?: number }
25
26export const pick = (answer: JevChoice | undefined): { model: Tier; confidence: number } | undefined =>
27  answer?.choice && answer.choice in TIERS && (answer.confidence ?? 0) >= MIN_CONFIDENCE
28    ? { model: answer.choice as Tier, confidence: answer.confidence! }
29    : undefined
30
31export const register: Register = on => {
32  on('session.start', async ($, e, next) => {
33    await $.command.register({ name: 'router', description: 'Let Jev pick general-purpose subagent models (jev on | jev off); sends task text to TypeSafe' })
34    return next(e)
35  })
36
37  // off by default: turning it on sends every general-purpose task to TypeSafe
38  on('command.run', { command: 'router' }, async ($, e) => {
39    const arg = e.args.trim()
40    if (arg !== 'jev on' && arg !== 'jev off') {
41      return { text: `🪙 Jev routing is ${(await $.store.get('jev')) === true ? 'on' : 'off'}. Use /router jev on | jev off.` }
42    }
43    const enable = arg === 'jev on'
44    if (enable && !(await $.env.get('TYPESAFE_API_KEY'))) return { text: '🪙 Set TYPESAFE_API_KEY first, then restart Claude Code.' }
45    await $.store.set('jev', enable)
46    return { text: enable ? '🪙 Jev routing on: general-purpose tasks are sent to TypeSafe to pick a model.' : '🪙 Jev routing off.' }
47  })
48
49  on('agent.spawn', async ($, e, next) => {
50    const rule = route(e)
51    if (!rule) return next(e)
52
53    const useJev = e.subagentType === 'general-purpose' && (await $.store.get('jev')) === true
54    const key = useJev ? await $.env.get('TYPESAFE_API_KEY') : undefined
55    const judged = key ? await ask($, key, e) : undefined
56    const model = judged?.model ?? rule
57    $.ui.toast(`🪙 ${e.subagentType} → ${model}${judged ? ` · jev ${judged.confidence.toFixed(2)}` : ''}`)
58    return next({ ...e, model })
59  })
60}
61
62const ask = async ($: Parameters<Parameters<Register>[0]>[2] extends never ? never : any, key: string, e: AgentSpawnInput) => {
63  const request = $.http.fetch(JEV_URL, {
64    method: 'POST',
65    headers: { Authorization: `Bearer ${key}`, 'Content-Type': 'application/json' },
66    body: JSON.stringify({
67      model: 'jev-latest',
68      state: { description: e.description, task: e.prompt.slice(0, MAX_TASK_CHARS) },
69      questions: {
70        tier: {
71          type: 'choice',
72          instructions: 'Which model tier does a coding agent need to do `task` well? Pick the cheapest tier that will still do it well.',
73          criteria: TIERS,
74        },
75      },
76    }),
77  })
78    .then((r: { ok: boolean; text: string }) => (r.ok ? pick(JSON.parse(r.text).answers?.tier) : undefined))
79    .catch(() => undefined) // network, auth or parse failure: the rule decides
80  return Promise.race([request, $.clock.sleep(JEV_TIMEOUT_MS).then(() => undefined)])
81}
82