Jev-chooses-a-LLM

Jev Router for Cursor

Cursor executes. LLMs write and build. Jev decides how much intelligence the task deserves.

Honest promise: pick the cheapest available route likely to complete successfully under policy — not a mathematically optimal model.

TypeSafe Jev is a decision layer only (Choice / Score / Noul). It does not browse, write prose, edit files, or operate accounts. Env: TYPESAFE_API_KEY.

Personal smoke test

In the Cursor Agents window for this project, paste:

Find today's most popular public posts about TypeSafe Jev on X/Twitter (by views if available). Rank the top 5 and say why each is popular. Do not log in or post anything.

Expected: Jev routes first (often BALANCED), then work uses web/research tools. In chat this is soft routing; for hard model switch use SDK --run.

Related MCP server: DeepMyst MCP Server

Chat vs SDK (read this)

Approval gates (production_deploy, financial_transaction, …) stop SDK runs unless you pass --approve.

What this product is

Hard routing rules (deterministic)

1. confidence < 0.70 → BALANCED

2. Security-sensitive → at least INTELLIGENCE

3. Financial / production deploy → INTELLIGENCE + human approval flag

4. Send/delete email, publish → approval required

5. Read-only research OK; simple reversible edit may be COST

6. COST fail → BALANCED → INTELLIGENCE → stop

7. Max 2 escalations; no infinite retry; no same-tier retry unless error says retry can succeed

8. Jev unavailable → BALANCED + degradedRouting: true

What you need for a working system

This repo is enough to run end-to-end if you bring keys and follow the right mode.

Required for routing (Jev)

1. Node.js 20+ (22.13+ recommended; 22+ for --use-system-ca on Windows TLS issues)

2. TYPESAFE_API_KEY in local .env (never commit)

3. npm install && npm test && npm run demo

Required for real model switching (SDK)

4. CURSOR_API_KEY in .env

5. npm install @cursor/sdk (optionalDependency / peer)

6. Run:

npx tsx sdk-runner/cli.ts --run "your task"
# Windows TLS/antivirus MITM:
# $env:NODE_OPTIONS="--use-system-ca"

Cursor Chat (soft mode)

7. Symlink/copy this folder into ~/.cursor/plugins/local/Jev-chooses-a-LLM (see scripts/setup.sh)

8. Enable MCP jev-router

9. Honest limit: chat parent model is not hot-swapped. Jev decides the tier; the parent (e.g. Grok) may still execute unless you use SDK --run.

Not included / not claimed

• Your personal API keys

• Guaranteed Cursor Router auto-smart (account-dependent; we fall back to catalog models)

• Automatic X login / posting

• Dollar cost when the plan does not expose billed cents

Clone

git clone https://github.com/Bodila51/Jev-chooses-a-LLM.git
cd jev-router-for-cursor
cp .env.example .env
# put TYPESAFE_API_KEY (and CURSOR_API_KEY for SDK --run) in .env — never commit it
npm install
npm test
npm run demo

Install

cd jev-router-for-cursor
cp .env.example .env   # set TYPESAFE_API_KEY; CURSOR_API_KEY for live SDK
npm install
npm test
npm run demo

Cursor Chat plugin (local)

./scripts/setup.sh
# or: ln -s "$(pwd)" ~/.cursor/plugins/local/jev-router-for-cursor

Enable the plugin in Cursor. Set variable TYPESAFE_API_KEY (Plugins → Configure) or export it for the MCP process. Restart Cursor if needed.

MCP only

npm run mcp
# or: npx tsx mcp/server.ts

Tools: jev_route, jev_dry_run, jev_status.

mcp.json wires the server for the plugin via ${CURSOR_PLUGIN_ROOT}.

Commands (Chat)

SDK runner

# Dry-run (no CURSOR_API_KEY required for routing path)
npm run dry-run -- "Rename foo to bar in util.ts"

# Route only
npm run route -- "Research TS test runners"

# Status
npx tsx sdk-runner/cli.ts --status

# Live run (needs CURSOR_API_KEY and Node >= 22.13 for @cursor/sdk)
npx tsx sdk-runner/cli.ts --run "Fix the failing auth test"

Programmatic:

import { runRoutedTask } from "./sdk-runner/index.js";

const result = await runRoutedTask({
  facts: { task: "…", repoPresent: true, needsEdit: true },
  dryRun: true,
});

Models

• Prefer Cursor Router: auto-smart + optimize_for: cost | balanced | intelligence when Cursor.models.list() shows it.

• If missing: pick real catalog IDs for the three tiers; never invent IDs.

• Offline/static fallback in config.example.json documents composer-2.5 only as a last resort label.

Cost

run.usage / agent.getUsage() — if cost is unavailable it is labeled unavailable. This product never invents dollar amounts.

Config

See config.example.json:

{
  "enabled": true,
  "defaultMode": "balanced",
  "confidenceThreshold": 0.7,
  "maximumEscalations": 2,
  "maximumTaskCostUsd": 1.0,
  "showRoutingTrace": true,
  "logPromptContent": false,
  "requireApprovalFor": ["send_email","delete_data","publish","production_deploy","financial_transaction"]
}

Kill switch: "enabled": false or /jev-bypass.

Architecture

User task
  ├─ Chat: rule → MCP jev_route → subagent jev-{cost|balanced|intelligence}
  └─ SDK:  facts → Jev → policy → model catalog → Agent.create/send → escalate

Shared: shared/config.ts, shared/telemetry.ts, shared/redaction.ts
MCP: mcp/server.ts, mcp/router.ts, mcp/policy.ts, mcp/typesafe-client.ts
SDK: sdk-runner/*

Skills (optional)

• email-triage — Jev classify/rank only; no send

• research-rank — Jev ranks candidates; Cursor browses/writes

Testing

npm test

Uses mock TypeSafe client and fixtures (11 product scenarios). No real API keys required in CI.

Chat mode is soft-enforced (rule + agents). SDK mode is hard-enforced in code.

Security

See SECURITY.md. Never commit .env. Telemetry redacts secrets; prompts off by default.

Limitations

• Chat cannot force the parent model ID; it delegates to subagents.

• Live @cursor/sdk needs Node >= 22.13 and CURSOR_API_KEY.

• Without TYPESAFE_API_KEY, dry-run/demo uses a deterministic mock; live Chat routing should set the key or expect degradedRouting.

• Optional Gmail/X are not bundled OAuth apps — skills document the pattern only.

Uninstall

rm -f ~/.cursor/plugins/local/jev-router-for-cursor
# remove MCP entry / disable plugin in Cursor

License

MIT — see LICENSE.