jev-lsp

Warning

Proof of concept / WIP. Interface, contract, and config keys may change. Nothing here should be relied on yet.

Landing · Tutorial · Guide

Jev is a classifier, not a chat model. A rule asks one typed question about one line; the answer is a value and a probability — never prose. jev-lsp runs .jev/rules/*.json as ordinary LSP diagnostics, code actions, and code lens while you edit or a harness writes.

Demo

Silent action loop across OpenCode, Neovim, and VS Code: paste an AI-slop comment, get a finding, apply the fix.

Watch (~32s) · landing page

Loop

1. Spec — what the code must do.
2. Rules — .jev/rules/*.json (words + pattern for candidate lines), versioned like code.
3. Steer — jev-lsp on save (human or harness).
4. Stay on track — findings are ordinary diagnostics.

Semi-deterministic: pattern is exact; judgement must clear the rule’s floor before publish. Not a correctness oracle. A repository with no .jev/rules/ of its own is inspected by the rule set shipped in the binary.

Cost

Well-defined rules let cheap / local models work: conventions live in the rule, the model answers about one line. No matching pattern → no model call.

Measured 2026-09-20 on this repo (jev inspect --force, decide jev-1.13 vs jev review / gemini-2.5-flash-lite):

	rules pass	chat review (same file)
server.rs ~2.6k lines	5,341 in / 345 out · 2 findings · $0.00022	30,562 in / 9 out · 0 findings · $0.00306
30 crates/**/*.rs	82,478 in / 3,831 out · 20 calls · $0.0034	—

10 of 30 docs had no candidate (cost nothing). Prices from the decide route’s usage.cost ($0.0395/MTok) and chat cost_details ($0.10 in / $0.40 out per MTok). Does not include generation cost; chat tiers stay on-demand. No local decide tier run end-to-end here — method in docs/MODEL.md.

Install

Requires Rust ≥ 1.75. Puts jev-lsp and jev on PATH (~/.cargo/bin):

cargo install --git https://github.com/makefunstuff/jev-lsp --locked jev-lsp jev

Neovim (primary)

ln -s /path/to/jev-lsp/nvim ~/.local/share/nvim/site/pack/jev/start/jev

require('jev').setup({})

Then: export a decide key, open a file, save.

export TYPESAFE_API_KEY=…   # hosted Jev default (api.typesafe.ai)

A repository with no .jev/rules/ is inspected all the same: the rule set the binary ships runs on it, those findings carry rule_source: "builtin", and :Jev inspect prints [builtin] or [repository] after each label. jev rules init writes the shipped set into .jev/rules/ as prose-…json / code-…json to read and edit; a file you edit shadows the shipped rule of the same id, and rules.defaults: false turns the shipped set off.

• First rule of your own: docs/TUTORIAL.md §3 · schema: docs/GUIDE.md §4
• Without the plugin (Neovim ≥ 0.12):

vim.lsp.config('jev', { cmd = { 'jev-lsp' }, filetypes = { 'rust' }, root_markers = { '.git' } })
vim.lsp.enable('jev')

Lazy.nvim: { dir = '/path/to/jev-lsp/nvim', name = 'jev', lazy = false, config = function() require('jev').setup {} end }.

Keymaps (plugin)

Key	Action
<leader>ja	code-action picker (visual = selection scope)
<leader>ju	undo last applied edit
<leader>jq	ask about the file
<leader>js	status: queue, budgets, endpoints

:Jev inspect — what the rules pass did (counts, findings, skips). :Jev inspect --force re-runs unchanged files. Tab-completes. Plugin needs Neovim ≥ 0.12.

Other clients

jev-lsp --stdio is a standard language server — any client that can start one works. Plugin is Neovim-only extras (attach, keymaps, :Jev).

Export endpoints before launch (JEV_DECIDE_*, JEV_BASE_URL, …) or set them in the client config. Other routes / local decide: docs/MODEL.md §8.

Chat tiers (actions / plans / explanations) — only when needed:

export JEV_BASE_URL=http://127.0.0.1:8080/v1
export JEV_MODEL=your-model-name
export JEV_API_KEY_ENV=OPENROUTER_API_KEY   # name of the env var, not the key

OMP

{"servers":{"jev-lsp":{"command":"/path/to/jev-lsp/target/release/jev-lsp","args":["--stdio"],
  "fileTypes":[".rs",".py",".md",".toml",".json",".lua",".sh"],"rootMarkers":[".git"],
  "settings":{"jev":{"models":{"decide":{"wire":"system_one","base_url":"https://opencode.ai/zen/v1",
    "model":"jev-1.13","api_key_env":"TYPESAFE_API_KEY","timeout_ms":15000}}}}}}}

api_key_env names the variable — export the value yourself. Env wins over settings. Helper: verify/omp_lsp.sh.

OpenCode

{"lsp":{"jev-lsp":{"command":["/path/to/jev-lsp/target/release/jev-lsp","--stdio"],"extensions":[".rs"],
  "env":{"JEV_DECIDE_BASE_URL":"http://127.0.0.1:8009/v1","JEV_DECIDE_MODEL":"kev-latest"}}}}

Cursor / VS Code

Needs the extension in editors/cursor/ (no settings-only LSP route). See docs/CURSOR.md.

ln -s "$PWD/editors/cursor" ~/.cursor/extensions/makefunstuff.jev-0.1.0   # reload window
# or: bash editors/cursor/pack.sh /tmp/jev-0.1.0.vsix && cursor --install-extension /tmp/jev-0.1.0.vsix

{
  "jev.server.path": "/path/to/jev-lsp/target/release/jev-lsp",
  "jev.decide.baseUrl": "https://api.typesafe.ai/v1",
  "jev.decide.model": "jev-latest",
  "jev.decide.wire": "system_one",
  "jev.decide.apiKeyEnv": "TYPESAFE_API_KEY",
  "jev.decide.apiKeyFile": "~/.bash_profile"
}

This repo

Conventions live in .jev/rules/*.json. Saving a file runs the pass. With hosted Jev, export TYPESAFE_API_KEY. At shipped floors this repo publishes zero findings (at the old 0.75 unwrap floor: two lines in one file); 12 of 30 Rust files had no candidate.

Docs

Doc	What
docs/TUTORIAL.md	First run end-to-end — start here
docs/GUIDE.md	Surfaces, settings, schema, CLI, troubleshooting
docs/CURSOR.md	Cursor extension + limits
docs/MODEL.md	Tiers, routing, cost method, local routes
docs/UX.md	Surfaces & product decisions
docs/LANGUAGE.md	Attachment, language resolution, gates
docs/ARCHITECTURE.md	Components, store, scheduler
PROTOCOL.md	Frozen LSP surface, commands, schemas, exit codes
docs/VERIFICATION.md	How claims are proven
STATUS.md	State & dated log
docs/ROADMAP.md	Work units
docs/STYLE.md	Writing register

Verify: bash verify/run-suite.sh /tmp/suite.log

Licence

MIT — see LICENSE.