Sys1

Sys1 gives coding agents tools to review code, check completion claims, and get structured answers from Jev or a local model. Jev is TypeSafe’s hosted decision model. Project skills work with Codex, Claude Code, and Devin; applications can use the same tools through a CLI, Node/Bun client, or HTTP API.

Latest release: v0.19.1. Install the GitHub release with npm and run it with Bun 1.3.14 or newer. MIT licensed.

Get started · Agent skills · Documentation · Releases

Choose what helps your workflow

You want to	Use	What you receive
Save a check and continue its review later	sys1 workflow	A saved execution record, a private command log, and input checks before resume.
Check a change against a repository rule	sys1 review	Candidates tied to the rule and diff, with feedback and reuse of unchanged reviews.
Check a proposed completion message	sys1 verify	A comparison with Git state, linked pull requests, and live pages.
Add a decision to application code	Client and HTTP API	Yes/no, choice, or score answers with probabilities and validated response shapes.
Keep long test logs out of the agent’s context	System One Skills, a separate package	A short result, the command’s exit status, and the full log saved locally. No model or API key.

Install

Install Bun 1.3.14 or newer and have npm available, then run:

npm install --global --allow-scripts=node-llama-cpp \
  https://github.com/hraness/sys1/releases/download/v0.19.1/hraness-sys1-0.19.1.tgz
sys1 --version

The version command prints the installed release number. The release supports macOS, Linux, and Windows. --allow-scripts=node-llama-cpp allows the optional local inference runtime’s install script; installation downloads no model weights and enables no hosted backend. The release includes a SHA-256 checksum.

CLI updates

Sys1 0.19.0 and newer support automatic updates for Bun and npm globals on macOS and Linux. Use sys1 update disable to keep a version. See update controls and supported installations.

Save a check and continue its review

From a Git worktree on macOS or Linux, run your repository’s check command:

sys1 workflow check -- bun test
sys1 workflow list

Sys1 saves the result and command output locally. This check needs no model or API key. After configuring a backend, sys1 workflow review can run the check and then review the selected changes. You can pause after the check and resume with the same inputs; uncertain interrupted steps are never silently repeated. ALGAL handles execution and saved state inside Sys1.

The workflow guide covers scoped reviews, resume, private logs, and inspecting a saved run. Keep running fresh required checks before delivery.

Review changes with your agent

Run these commands inside the Git repository you are working on. They install project instructions and preview a review without calling a model:

sys1 review setup codex
sys1 review checkpoint --worktree --model typesafe/jev-1.13.0 \
  --max-requests 10 --dry-run --json -- src test

For Claude Code, use setup claude-code; for Devin, use setup devin. Replace src test with the paths you changed. The preview lists selected files, rules, skipped evidence, and the number of requests. If no requests are planned, inspect the skipped evidence, selected paths, and active rules. Setup adds no automatic hooks and preserves existing instructions.

The bundled rules cover newly empty catch blocks and removed test assertions in JavaScript and TypeScript. Add your repository’s rules for conventions that need judgment. For an exact syntax pattern, use a linter. Review and completion checks are experimental and advisory: investigate findings and keep the repository’s normal tests and review.

Add hosted Jev

Get a key from TypeSafe and provide it as TYPESAFE_API_KEY through your shell or secret manager. Then enable Jev:

sys1 jev enable
sys1 jev status

The key stays in the environment. Enabling Jev selects hosted-only routing, so a failed hosted request cannot silently use a local model. Selected source and diff context go to Jev; inspect the preview before sending them. Provider usage is billed by TypeSafe at its published rates.

Run the previewed check by removing --dry-run:

sys1 review checkpoint --worktree --model typesafe/jev-1.13.0 \
  --max-requests 10 --json -- src test

No background gateway is needed for this hosted workflow. Investigate each candidate and record it as useful, incorrect, or unverifiable. Complete, unchanged batches reuse their review for up to 24 hours. The review guide covers feedback, rechecks, and rule drafts; sys1 audit runs a check without saved review history.

Check an agent’s completion message

After setting up a backend, install the standalone verification instructions:

sys1 verify setup codex

Use setup claude-code or setup devin for those agents. Ask the agent to save its proposed final message outside the Git worktree, then compare the draft with available evidence:

sys1 verify --message /tmp/final-message.txt \
  --model typesafe/jev-1.13.0 --dry-run --json

Choose an equivalent external file path on Windows. The preview reports the input type and model route without model calls or page fetches. Read the message file and inspect its links before rerunning without --dry-run; the message and any fetched page excerpts go to the selected backend. Use --message - for piped text and --url https://example.com to include a live page the message does not link.

Contradictions exit 7; unavailable evidence is marked unverifiable. A clean report does not prove completion. File input works with any coding agent; check-command evidence requires local Devin transcript discovery. See the verification guide for input modes, evidence, and exit codes.

Use as a module

For an application using Node 24 or Bun, install the portable client:

npm install --omit=optional \
  https://github.com/hraness/sys1/releases/download/v0.19.1/hraness-sys1-0.19.1.tgz

With a backend configured, run sys1 up to start the gateway, then call it:

import { createClient } from "@hraness/sys1/client";

const sys1 = createClient(); // http://127.0.0.1:13900
const { response } = await sys1.evaluate({
  model: "typesafe/jev-1.13.0",
  state: "Customers cannot complete checkout after today’s release.",
  questions: {
    urgent: {
      type: "noul",
      instructions: "Does this describe an active customer-impacting incident?",
    },
  },
}, { signal: AbortSignal.timeout(5_000) });

console.log(response.answers.urgent);

The answer contains the model’s probability of yes. Sys1 validates requests and responses, supports cancellation, and returns stable error codes. Your application decides which actions are allowed and evaluates the model on its own examples. A valid answer can still be wrong.

The client and embedded router guide covers custom endpoints, the in-process Bun router, and existing Jev applications.

The endpoint

The loopback gateway serves POST /v1/systemone for decisions, GET /v1/models for discovery, and GET /healthz for liveness. HTTP request and response reference.

Local models

Local Qwen models are experimental. In the broader recorded studies, Qwen3 1.7B answered 32/72 cases correctly; Qwen3.5 4B answered 44/72 on a different fresh fixture. Evaluate the selected model on your task before relying on it. Model studies.

Preview the download with sys1 setup --dry-run --json. The local setup guide covers supported platforms, downloads, and model selection. Setup explicitly downloads and selects Qwen3 1.7B; other installed models are never automatic substitutes.

External System One backends

Connect a server that implements the System One API, including OpenJev or Kev. Register and check the server, then select it in each request. Adding a server does not change default routing. Compatible server setup · Kev and decision profiles.

Reference and troubleshooting

• sys1 doctor and diagnostics: inspect the runtime, routing, model store, and gateway after setup.
• Routing: select a model and control fallback.
• Configuration: settings, credentials, and gateway access.
• Commands: CLI reference and JSON output.
• Decision profiles: reuse questions across application requests.
• Model comparison and evaluation reports: inspect model-specific evidence.

If sys1 is missing after installation, check that npm’s global binary directory is on your PATH and that bun --version works. If a request cannot find a model, inspect sys1 jev status and sys1 doctor. Restart an existing gateway after changing its credential environment.

Releases

An annotated v<version> tag at the exact current main head requests a release and must match package.json. The release workflow reruns the complete gate, creates one npm-format tarball and SHA256SUMS, and installs those exact bytes with the native dependency on Ubuntu, macOS, and Windows before publishing an immutable GitHub Release. Release notes come from CHANGELOG.md. The optional npm mirror publishes that same tarball after the package’s one-time registry setup.

Development

git clone https://github.com/hraness/sys1.git
cd sys1
bun install
bun run check

See CONTRIBUTING.md for the development and release workflow. Report a bug in GitHub Issues, or follow SECURITY.md for a security report.