cursor-jev

Route Cursor subagents with TypeSafe Jev, and ask typed Choice / Score / Noul questions from any agent.

Jev is not a chat model. It cannot write code, call tools, or be used as a Cursor model ID (jev, jev-latest, and typesafe-ai/jev are invalid there). Jev classifies and scores; Cursor LLMs execute.

The value is not “another AI”. Expensive Cursor hops become cheaper and rarer. Jev answers yes / no / which option in about 100ms. It does not write the patch.

Parent agent
  → Task / Write / shell
    → hook
    → TypeSafe Jev (~100ms)
    → allow / deny / ask / rewrite
    → MCP jev_judge / jev_ask / jev_route / jev_auth

Why this helps

It saves three things.

1. Extra subagents. Task is a costly hop: new context, a second search, sometimes nesting. The plugin cuts that itself. A local edit stays on the current agent. A second Task in the same turn is blocked. A nested subagent is denied. That matters when the model likes to spawn explore / generalPurpose “just in case”.

2. Extra repo reads. After Grep / Glob, Jev keeps about three relevant files and denies Read of README, sibling modules, and other noise. On a large monorepo that is where an agent burns a turn on fifteen files instead of two.

3. Scope creep. “Fix the bug” should not become a neighbor refactor plus extra tests. The scope gate denies writes the user did not ask for. Destructive shell (reset --hard, push --force) asks you instead of running silently.

The agent can also call Jev instead of a long thinking pass: which of four files, done or not, one job or three. That is faster than another reasoning loop.

Almost useless on a one-file tweak, with no TypeSafe key (hooks fail open), or when a hook blocks a Read / Write you actually needed — then it is friction, not speed.

Cursor still writes the code. Jev only decides whether that hop is worth taking.

Related MCP server: Jev MCP

Install

Requires Node.js 22.13+ (node:sqlite is unflagged there). Zero runtime npm dependencies.

git clone https://github.com/mywwave/cursor-jev.git
cd cursor-jev
node bin/cli.mjs install

On Windows you can use cursor-jev.cmd install instead.

Then fully restart Cursor (or Developer: Reload Window).

install merges into existing Cursor config and copies a local plugin (logo + Configure form):

node bin/cli.mjs uninstall

Uninstall keeps ~/.cursor/cursor-jev.env and the SQLite file. Enable local plugins in Cursor if the Jev plugin does not appear under Customize → Plugins.

Connect (pick one)

1. Cursor UI (recommended): Customize → Plugins → Jev → Configure → paste a TypeSafe API key from console.typesafe.ai.

2. CLI: node bin/cli.mjs set-key (saves ~/.cursor/cursor-jev.env, never git).

3. In chat: ask the agent to call MCP jev_auth.

Do not put the key in git, mcp.json, hooks.json, or a committed .env.

CLI

cursor-jev set-key                 Save the TypeSafe key to ~/.cursor/cursor-jev.env
cursor-jev key                     Show whether a key is saved (does not print the secret)
cursor-jev install [--no-rule] [--no-skill]
cursor-jev uninstall
cursor-jev mcp                     Stdio MCP server (Cursor launches this)
cursor-jev hook                    Cursor hooks (Cursor launches this)

MCP tools

After Cursor reconnects, the server is named Jev. Tools:

Resources: jev://status. Prompts: connect-typesafe, route-task.

Do not send secrets, .env files, credentials, or full transcripts as state.

install registers both a user MCP server (jev) and the plugin server (plugin-cursor-jev-jev). They are the same process; keep whichever you prefer.

Speed

Jev is ~100ms per judgment. A Cursor Task subagent is seconds to minutes. The plugin speeds agents by cutting hops, not by replacing the coding model. Missing key, HTTP error, or timeout fail open.

The Task prompt also gets a one-pass contract (Jev speed: fast|standard|thorough).

This is the same pattern as TypeSafe's cookbooks: Choice/Noul is ~7–100× faster than asking a chat model the same closed question. Wall-clock for a whole coding session still depends on the Cursor LLM; Jev removes the extra loops around it.

Gates

Hooks call the same questions as MCP jev_judge. Thresholds live in src/roles.mjs. Missing key, HTTP error, or timeout fail open.

Routine shells (git status, git diff, node --test, …) skip the model.

Rerank is additive. Existing Task / scope / split / ready / shell gates stay. SQLite adds a reads table next to asks and fanout; those tables are not dropped. No allowlist yet (or a TypeSafe miss) fail-opens and every Read is allowed. File bodies are never sent to TypeSafe — only path + short snippet.

Prefers jev_judge over inventing jev_ask questions. jev_ask stays for custom Choice / Score / Noul.

Session state is a SQLite file at ~/.cursor/cursor-jev.sqlite (node:sqlite, WAL, 2s busy timeout). Concurrent hook processes share it without an extra npm dependency. Secrets are stripped before write.

Routing

On every Task call the hook sends the task text to POST https://api.typesafe.ai/v1/systemone (jev-latest) with:

• Choice role — Cursor subagent_type (explore, generalPurpose, cursor-guide, docs-researcher, ci-investigator, ai-architect, deployment-expert, performance-optimizer, plus bugbot / security-review only when the parent already requested them)

• Noul needs_specialist — whether a specialist beats generalPurpose

Code decides:

The subagent model is never changed. Questions and thresholds live in src/roles.mjs.

Plugin layout

This repo is a Cursor plugin as well as a CLI:

• .cursor-plugin/plugin.json — name Jev, logo, optional TYPESAFE_API_KEY

• mcp.json — plugin stdio MCP (${CURSOR_PLUGIN_ROOT}, no secrets)

• hooks/hooks.json — Task, Write, prompt, shell, and ready hooks

• assets/logo.svg — plugin and MCP avatar

• rules/jev-typesafe.mdc and skills/jev-subagents/SKILL.md

For building TypeSafe features in your own apps, install the official skill separately:

npx skills add typesafe-ai/skills --skill typesafe-ai

Docs: TypeSafe introduction, API, intent routing.

Outside Cursor

The plugin is Cursor-only. The same TypeSafe call (POST /v1/systemone, then branch in your code) is how you use Jev in tickets, moderation, matching, or dates. This repo does not ship a second service.

Keep questions atomic. Combine answers in code. Never send secrets or full transcripts as state.

Develop

Zero runtime dependencies.

node --test
node scripts/mcp-smoke.mjs

npm test runs the same unit suite. The smoke script talks to TypeSafe if TYPESAFE_API_KEY or ~/.cursor/cursor-jev.env is set.

If Cursor shows Jev as loading, reload the window after install. Stdio uses newline-delimited JSON (MCP spec), not LSP Content-Length.

License

MIT