Jevbridge

Table of Contents

1. About The Project
   • Core Capabilities
   • Built With
2. Getting Started
   • Prerequisites
   • Installation
3. Usage
4. MCP Server
5. ACP Adapter
6. Computer Use
7. Roadmap
8. Contributing
9. License
10. Contact
11. Acknowledgments

About The Project

TypeSafe Jev is a System One model: unstructured state in, typed probabilistic decisions out. It does not generate text. That makes it a poor chatbot and an excellent function call for routing, gating, scoring, and computer-use action selection.

Jevbridge is the adapter that sits alongside the LLM you already run.

• Native Jev when TYPESAFE_API_KEY is set.
• Any LLM as System One when it is not — Codex, Claude, Grok, OpenCode, or a generic OpenAI-compatible endpoint.
• ACP over stdio so Zed, JetBrains, and other Agent Client Protocol hosts can treat Jev as the decision sidecar for a generating model.
• Confidence gates so a peaked distribution executes, a middling one confirms, and a destructive click does not go unsupervised.

The LLM writes the plan and the explanation. Jevbridge returns noul, choice, and score answers that software can branch on.

Home: tacticocc/Jevbridge.

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Core Capabilities

• Evaluate one state against mixed Choice, Score, and Noul questions.
• Swap backends (jev | llm | heuristic | auto) without changing question shapes.
• Confidence-gate tool calls and computer-use clicks (execute, confirm, escalate, abort).
• Speak MCP (jev_decide, jev_gate, jev_computer_use) and ACP over stdio.
• Ship recipes for support routing, destructive command gates, context keep/drop, and GUI next-action.
• Run offline with the heuristic backend in tests and CI.

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Built With

• 
• 
• 
• 

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Getting Started

Jevbridge is a zero-dependency Node 22 library plus MCP and ACP stdio binaries. You do not need a TypeSafe key to try it: the heuristic backend and any OpenAI-compatible LLM both speak the same protocol.

Prerequisites

• Node.js 22 or newer
• Git
• Optional: a TypeSafe API key
• Optional: an LLM key (XAI_API_KEY, OPENAI_API_KEY, ANTHROPIC_API_KEY, or OPENCODE_API_KEY)

Installation

1. Clone the repo

   git clone https://github.com/tacticocc/Jevbridge.git
   cd Jevbridge
   

   The npm name is @tactico/jevbridge. After a release is published:

   npm install -g @tactico/jevbridge
   

2. Install (no runtime npm dependencies)

   npm install
   

3. Export keys you actually have. Native Jev is preferred; otherwise Jevbridge wraps your LLM.

   export TYPESAFE_API_KEY=ts_...
   export JEVBRIDGE_LLM=xai
   export XAI_API_KEY=xai-...
   

4. Run a recipe without any network

   node --experimental-strip-types src/cli.ts eval support-route
   

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Usage

Library

import { evaluate, gate, noul, choice, score } from "./src/index.ts";

const result = await evaluate({
  state: "I was charged twice for order A-104. Refund the duplicate today.",
  questions: {
    refund: noul("Does this request a refund?"),
    team: choice("Which team should handle this?", {
      billing: "Payments, invoices, refunds.",
      technical: "Bugs, outages, integrations.",
      other: "None of the above.",
    }),
    urgency: score("How urgent is this?", [
      "Can wait a week",
      "Handle today",
      "Blocking now",
    ]),
  },
  backend: "auto",
  jev: process.env.TYPESAFE_API_KEY
    ? { apiKey: process.env.TYPESAFE_API_KEY }
    : undefined,
});

const decision = gate(result.answers, { choiceId: "team" });
if (decision.action === "execute") {
  // branch on result.answers.team.choice
}

CLI

node --experimental-strip-types src/cli.ts recipes
node --experimental-strip-types src/cli.ts eval computer-use
node --experimental-strip-types src/cli.ts mcp
node --experimental-strip-types src/cli.ts acp

Or use the wrapper:

node bin/jevbridge.mjs eval destructive-gate

Environment

backend: "auto" uses Jev when a TypeSafe key is present, otherwise the LLM adapter, otherwise heuristic.

With no API key, auto falls back to the local keyword scorer. The payload reports "backend": "heuristic". That scorer includes question text in its evidence, so asking "would this spend money, delete data, or submit a form?" about "hello world" can still score high from word overlap. Treat heuristic numbers as a smoke test, not a safety signal.

For more examples, see src/recipes.ts and skills/jevbridge/SKILL.md.

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MCP Server

Jevbridge speaks the Model Context Protocol over stdio (newline-delimited JSON-RPC 2.0). Point Claude Desktop, Cursor, Codex, OpenCode, or any MCP host at jevbridge mcp. The generating model keeps writing; Jevbridge is the typed decision tool.

Also exposes jevbridge://recipe/{id} resources and two prompts.

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "jevbridge": {
      "command": "node",
      "args": [
        "--experimental-strip-types",
        "/absolute/path/to/Jevbridge/src/cli.ts",
        "mcp"
      ],
      "env": {
        "TYPESAFE_API_KEY": "ts_..."
      }
    }
  }
}

Codex (~/.codex/config.toml):

[mcp_servers.jevbridge]
command = "node"
args = ["--experimental-strip-types", "/absolute/path/to/Jevbridge/src/cli.ts", "mcp"]

OpenCode (opencode.json) and Cursor (.cursor/mcp.json) live in examples/. Drop-in copies:

• examples/claude-desktop.json
• examples/cursor.mcp.json
• examples/codex.config.toml
• examples/opencode.json
• examples/zed.settings.json
• examples/zed.claude-proxy.json
• examples/zed.codex-proxy.json

Example tool call:

{
  "name": "jev_decide",
  "arguments": {
    "state": "I was charged twice for order A-104. Refund the duplicate today.",
    "questions": {
      "refund": { "type": "noul", "instructions": "Does this request a refund?" },
      "team": {
        "type": "choice",
        "instructions": "Which team should handle this?",
        "criteria": {
          "billing": "Payments, invoices, refunds.",
          "technical": "Bugs, outages, integrations.",
          "other": "None of the above."
        }
      }
    }
  }
}

Call jev_gate before a destructive tool. Call jev_computer_use instead of asking the LLM which CSS selector to click.

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ACP Adapter

Jevbridge implements the Agent Client Protocol over stdio with LSP-style Content-Length framing.

Add to Zed settings.json:

{
  "agent_servers": {
    "Jevbridge": {
      "type": "custom",
      "command": "node",
      "args": [
        "--experimental-strip-types",
        "/absolute/path/to/Jevbridge/src/cli.ts",
        "acp"
      ],
      "env": {
        "TYPESAFE_API_KEY": "ts_...",
        "JEVBRIDGE_LLM": "anthropic",
        "ANTHROPIC_API_KEY": "sk-ant-..."
      }
    }
  }
}

On session/prompt the sidecar:

1. Classifies the turn (question, code edit, computer use, terminal).
2. Calls Jev or the LLM System One adapter.
3. Confidence-gates the result.
4. Streams session/update tool calls and a short agent message.

Sessions persist under ~/.jevbridge/sessions. The adapter advertises loadSession plus sessionCapabilities.resume / list / close / delete, so Zed and other hosts can restore a thread with session/load (replay history) or session/resume (reconnect without replay).

Proxy an upstream agent

Point Jevbridge at Claude Code or Codex. It speaks ACP to the host, forwards the generating agent, and intercepts session/request_permission plus pending tool_call notifications. Jevbridge then allows, asks the user, or denies the call.

jevbridge acp --upstream claude
jevbridge acp --upstream codex
jevbridge acp -- /path/to/custom-acp-agent

Zed settings.json (Codex behind Jevbridge):

{
  "agent_servers": {
    "Jevbridge Codex": {
      "type": "custom",
      "command": "npx",
      "args": ["-y", "@tactico/jevbridge", "acp", "--upstream", "codex"],
      "env": {
        "TYPESAFE_API_KEY": "ts_..."
      }
    }
  }
}

Presets spawn npx -y @agentclientprotocol/claude-agent-acp and npx -y @agentclientprotocol/codex-acp. Destructive execute/delete/edit/move calls that Jev aborts are failed in the client and cancelled upstream.

Codex, Claude Code, Grok Build, and OpenCode keep generating. Jevbridge decides.

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Computer Use

Computer-use loops waste frontier tokens on “what should I click.” Jevbridge scores a GUI observation against a closed action set:

click · type · scroll · wait · screenshot · done · abort

plus target, safety, destructiveness, and goal progress. A refund button that spends money comes back confirm, not execute — destructiveness is an independent gate, so a peaked action distribution does not skip it.

import { computerUseQuestions, observationState, readAction } from "./src/index.ts";

const state = observationState({
  goal: "Refund the duplicate charge on order A-104",
  app: "Billing Console",
  visible: ["Refund duplicate", "Email customer", "Close ticket"],
});

const result = await evaluate({
  state,
  questions: computerUseQuestions(["Refund duplicate", "Email customer", "Close ticket"]),
  backend: "auto",
});

const action = readAction(result.answers);

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Roadmap

• System One client (Jev, LLM adapter, heuristic)
• Confidence gate
• Computer-use recipes
• ACP stdio adapter (initialize, session/new, session/prompt)
• MCP stdio server (jev_decide, jev_gate, jev_computer_use, jev_recipe)
• Proxy an upstream ACP agent (Claude Code, Codex) and intercept tool calls
• Session load / resume
• Published npm package @tactico/jevbridge
• Transfer this repository into the tacticocc organization

See the open issues for a full list of proposed features (and known issues).

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Contributing

Contributions are what make the open source community such an amazing place to learn, inspire, and create. Any contributions you make are greatly appreciated.

If you have a suggestion that would make this better, please fork the repo and create a pull request. You can also simply open an issue with the tag "enhancement". Don't forget to give the project a star! Thanks again!

1. Fork the Project
2. Create your Feature Branch (git checkout -b feature/AmazingFeature)
3. Commit your Changes (git commit -m 'Add some AmazingFeature')
4. Push to the Branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

Please add or update tests under src/*.test.ts for behavioral changes.

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Top contributors:

License

Distributed under the MIT License. See LICENSE for more information.

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Contact

Tactico — github.com/tacticocc

Project Link: https://github.com/tacticocc/Jevbridge

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Acknowledgments

• Best-README-Template
• TypeSafe Jev and the System One adapter
• Agent Client Protocol
• Choose an Open Source License
• Img Shields
• GitHub Pages

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