Preloop: The Policy Engine for AI Agents

Preloop is a comprehensive MCP firewall that gives you complete control over what AI agents can do. Define access policies, approval workflows, and audit trails. Allow, deny, or require approval based on conditions.

Preloop is also evolving into an AI workforce control plane for managed runtimes. Flows can now route model traffic through a Preloop-owned OpenAI-compatible gateway so usage, spend, runtime identity, and budgets can be enforced centrally.

Works with OpenClaw, Claude Code, Cursor, Codex, and any MCP-compatible agent.

Read the official documentation: Full guides and tutorials are available at docs.preloop.ai.

Why Preloop?

AI agents like Claude Code, Cursor, and OpenClaw are transforming how we work. But with great power comes great risk:

• Accidental deletions. One wrong command and your production database is gone.

• Leaked secrets. API keys pushed to public repos before anyone notices.

• Runaway costs. Agents spinning up expensive resources without limits.

• Breaking changes. Untested deployments to production at 3am.

Most teams face an impossible choice: give AI full access and move fast (but dangerously), or lock everything down and lose the productivity gains.

Preloop solves this. Define policies that allow safe operations, deny dangerous ones, and require human approval for everything in between. You stay in control. AI handles the routine work.

Core Capabilities

Access Policies

Define fine-grained access controls for any AI tool or operation:

• Tools support multiple ordered access rules (not just simple approval/deny)

• Rules are evaluated in priority order; first matching rule wins

• Each rule has an action (allow/deny/require_approval), optional CEL condition, and optional denial message

• Rules can be reordered via drag-and-drop in the UI

Approval Workflows

When AI attempts a protected operation, Preloop pauses and notifies you:

• Instant notifications via mobile app, email, Slack, or Mattermost

• One-tap approvals from your phone, watch, or desktop

• Async approval mode — tool returns immediately with a polling handle; the agent polls get_approval_status until approved, then receives the tool result (Enterprise)

• Per-tool justification — require or optionally request agents to explain why a tool is being called before approval (Enterprise)

• Team-based approvals with quorum requirements (Enterprise)

• Escalation policies for time-sensitive operations (Enterprise)

Policy-as-Code

Define policies in YAML, manage via CLI or API:

# Example: Require approval for production deployments
version: "1.0"
metadata:
  name: "Production Safeguards"
  description: "Require approval before deploying to production"
  tags: [security, production]

approval_workflows:
  - name: "deploy-approval"
    timeout_seconds: 600
    required_approvals: 1
    async_approval: true          # Agent polls instead of blocking

tools:
  - name: "bash"
    source: mcp
    approval_workflow: "deploy-approval"
    justification: required        # Agent must explain the call
    conditions:
      - expression: "args.command.contains('deploy') && args.command.contains('production')"
        action: require_approval
        description: "Production deployments require approval"

• Version control your policies alongside your code

• GitOps workflows for policy changes

• CLI management for automation and scripting

• API access for programmatic policy management

Complete Audit Trail

Every AI action is logged with full context:

• What was attempted (tool, parameters, context)

• Which policy matched and why

• Who approved or rejected (and when)

• Execution result and duration

Essential for security reviews, compliance, and debugging.

AI Model Gateway

Preloop can terminate model traffic on behalf of managed runtimes instead of handing provider credentials directly to agent containers:

• OpenAI-compatible gateway endpoints: GET /openai/v1/models, POST /openai/v1/chat/completions, POST /openai/v1/responses

• Anthropic-compatible gateway endpoint: POST /anthropic/v1/messages

• SSE streaming support for chat completions and responses

• Per-request attribution to account, flow, flow execution, API key, and runtime principal

• Token and estimated-cost accounting persisted to the gateway usage ledger

• Account-level and flow-level budget enforcement with soft-limit annotations and hard stops

• Product-facing usage summary endpoints for account and flow monitoring

• Account-scoped runtime session explorer endpoints for browsing managed sessions beyond flows

• Execution-scoped gateway event inspection via GET /api/v1/flows/executions/{execution_id}/gateway-events

• Console surfaces for browsing recent runtime sessions and searching captured gateway interactions

Secret Custody

Preloop now stores AI model credentials behind a provider-agnostic secret abstraction:

• Built-in local_encrypted backend for simple self-hosted deployments

• Hash-only runtime API tokens for flow executions

• Optional external secret backend path for Vault/OpenBao-compatible KV v2 stores

• Agent runtimes can receive short-lived Preloop gateway tokens instead of provider secrets

Comparison with AWS Agent Core

Preloop is the open-source alternative to AWS Agent Core for teams who want vendor-neutral, self-hosted AI governance.

AI Agent -> Preloop -> [Policy check] -> Allow / Deny / Require Approval -> Execute

How it works:

1. Define policies for each tool: allow, deny, or require approval

2. Policies can be fine-grained, checking parameter values and context

3. AI agents call tools through Preloop's MCP proxy

4. Actions are allowed, denied, or paused for approval based on your policies

5. Full audit trail of every action and decision

Key Features

Safety & Control

• Policy Engine. Define allow, deny, and approval workflows for any tool or action.

• Access Rules. Multiple ordered rules per tool with allow/deny/require approval actions.

• Drag-and-Drop Priority. Reorder rule evaluation priority visually.

• Fine-Grained Rules. Policies can check tool names, parameter values, and context.

• Instant Notifications. Get alerts on mobile, email, Slack, or Mattermost.

• One-Tap Approvals. Approve or reject from your phone, watch, or desktop.

• Full Audit Trail. Complete log of every AI action and policy decision.

• Async Approval Mode. Non-blocking approval: tool returns immediately, agent polls get_approval_status until the human decides.

• Per-Tool Justification. Require agents to provide a reason for each tool call. Mode: required (blocks without it) or optional (agent may provide one).

• Flexible Conditions. Use CEL expressions for context-aware rules (Enterprise).

• AI Approval (Enterprise). AI-driven approval with configurable model, prompt, confidence threshold, and fallback behavior.

• Team Approvals. Require quorum from multiple team members for critical ops (Enterprise).

Integration & Compatibility

• MCP Proxy. Works with any Model Context Protocol-compatible AI agent.

• Zero Infrastructure Changes. Drop-in solution, no code modifications needed.

• Built-in Tools. 11 tools for issue and PR/MR management included.

• External MCP Servers. Proxy any external MCP server through Preloop's safety layer.

• Issue Tracker Sync. Connect Jira, GitHub, GitLab for full context.

Automation Platform

• Agentic Flows. Build event-driven workflows triggered by webhooks, schedules, or tracker events.

• Gateway-Routed Model Access. Managed flows can use a Preloop-owned model gateway for centralized cost controls, telemetry, and key custody.

• Vector Search. Intelligent similarity search using embeddings.

• Duplicate Detection. Automatically identify overlapping issues.

• Compliance Metrics. Evaluate and improve issue quality.

• Web UI. Modern interface built with Lit, Vite, and Shoelace.

Looking for Enterprise features? Preloop Enterprise Edition adds RBAC, team-based approvals, advanced audit logging, and more. See Enterprise Features below.

Open Source vs Enterprise (important)

• Open Source: single-user approvals with email, mobile app, Slack, and Mattermost notifications.

• Enterprise: adds advanced conditions (CEL), team-based approvals (quorum), and escalation.

• Mobile & Watch apps: the iOS/Watch and Android apps can be used with self-hosted / open-source Preloop deployments.

Supported Issue Trackers

• Jira Cloud and Server

• GitHub Issues

• GitLab Issues

• (More to be added in future releases, including Azure DevOps and Linear)

Architecture

Preloop features a modular architecture designed to provide a secure control plane for AI agents, separating the core API server, database models, backend synchronization services, and the web frontend console.

For a complete conceptual overview of the system components, data flows, and infrastructure, please see the Architecture Document.

Frontend & CLI

• Preloop Console (Frontend): Located in the frontend directory, the web interface gives you governance controls, tool management, and dashboard visibility. See frontend/README.md for details.

• Preloop CLI: Manage policies and system state from the command line. See cli/README.md for usage.

Installation

Prerequisites

• Python 3.11+

• PostgreSQL 14+

• PGVector extension for PostgreSQL (for vector search capabilities)

Local Setup

# Clone the repository
git clone https://github.com/preloop/preloop.git
cd preloop

# Create and activate a virtual environment
python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

# Install dependencies
pip install -e ".[dev]"

# Set up the database

# Configure your environment
cp .env.example .env
# Edit .env with your settings

Configuration

Environment Variables

Preloop is configured via environment variables. Copy .env.example to .env and customize as needed.

Core Settings

Model Gateway & Secrets

Feature Flags

Disabling Self-Registration

For private deployments where you want to control who can access the system:

# In your .env file or Docker environment
REGISTRATION_ENABLED=false

When registration is disabled:

• The "Sign Up" button is hidden from the UI

• The /register page redirects to /login

• The /api/v1/auth/register API endpoint returns 403 Forbidden - preventing direct API registration attempts

• New users must be invited by an administrator

Security Note: With REGISTRATION_ENABLED=false, the backend API enforces the restriction at the endpoint level. Any attempt to register via the API (including scripts or direct HTTP requests) will be rejected with a 403 status code.

To invite users when registration is disabled, use the admin API or CLI (Enterprise Edition includes a full admin dashboard for user management).

GitHub App (Optional)

For enhanced GitHub integration including PR status checks and bot reactions:

These are optional and only needed if you're using a GitHub App for authentication or advanced features like reaction management on PRs.

OAuth Sign-In (Enterprise)

Enable OAuth sign-in/sign-up via GitHub, Google, and/or GitLab. Users can authenticate with their existing provider accounts instead of creating a Preloop-specific password.

GitHub OAuth sign-in reuses the GitHub App credentials above. Enable via Helm values:

mcpOauth:
  enabled: true
googleOauth:
  enabled: true
  clientId: "your-google-client-id"
  clientSecret: "your-google-client-secret"
gitlabOauth:
  enabled: true
  clientId: "your-gitlab-client-id"
  clientSecret: "your-gitlab-client-secret"

Supported flows:

• GitHub: Sign-in + automatic tracker setup prompt

• Google: Sign-in only (no tracker created)

• GitLab: Sign-in + automatic tracker setup prompt

MCP OAuth 2.1 Server

Preloop includes a built-in OAuth 2.1 Authorization Server for MCP client authentication (e.g., Claude Desktop). This is enabled automatically when mcpOauth.enabled=true.

Discovery endpoints:

• GET /.well-known/oauth-authorization-server — RFC 8414 metadata

• GET /.well-known/oauth-protected-resource — RFC 9728 metadata

OAuth endpoints:

• POST /oauth/register — Dynamic Client Registration (RFC 7591)

• GET /oauth/authorize — Authorization endpoint (redirects to consent page)

• POST /oauth/token — Token exchange (Authorization Code + PKCE for MCP, JWT for CLI)

• POST /oauth/revoke — Token revocation

Docker Setup

# Clone the repository
git clone https://github.com/preloop/preloop.git
cd preloop

# Run the full development stack (backend + workers + frontend with HMR)
docker compose up

# Run with tagged release images (production)
PRELOOP_VERSION=0.8.0 SECRET_KEY=$(openssl rand -hex 32) \
  docker compose -f docker-compose.release.yaml up -d

Quick installers are also available:

# Install the standalone CLI
curl -fsSL https://preloop.ai/install/cli | sh

# Install the OSS stack
curl -fsSL https://preloop.ai/install/oss | sh

Set PRELOOP_VERSION=0.8.0 before either command to pin a specific release, or use https://preloop.ai/install/?version=0.8.0`.

The default docker compose up command uses docker-compose.override.yml for local development, so source changes in backend/ and frontend/ are mounted directly into the containers. The frontend runs via Vite on http://localhost:5173, while the backend API stays on http://localhost:8000.

See docker-compose.release.yaml for full configuration and required environment variables.

Release Management

Use the release script to prepare a new version across the main release surfaces:

./scripts/release.sh 0.8.0

The script can also optionally commit the release prep, create and push v<version>, and watch the GitHub Release workflow with gh.

See RELEASING.md for the full checklist and scripts/release.sh for the release prep helper.

Kubernetes Setup

Preloop can be deployed to Kubernetes using the provided Helm chart:

# Add the Spacecode Helm repository (if available)
# helm repo add spacecode https://charts.spacecode.ai
# helm repo update

# Install from the local chart
helm install preloop ./helm/preloop

# Or install the packaged chart from a GitHub release
# helm install preloop https://github.com/preloop/preloop/releases/download/v0.8.0-beta.3/preloop-0.8.0-beta.3.tgz

# Or install with custom values
helm install preloop ./helm/preloop --values custom-values.yaml

For more details about the Helm chart, see the chart README.

Usage

Starting the Server

1. Set Environment Variables: Ensure you have a .env file configured with the necessary environment variables (see .env.example). Key variables include database connection details, API keys, etc.

2. Start Preloop API: Use the provided script to start the main API server:

   ./start.sh

   This script typically handles activating the virtual environment and running the server (e.g., python -m preloop.server).

3. Start Preloop Sync Service: In a separate terminal, start the synchronization service to begin indexing data from your configured trackers:

   # Activate the virtual environment if not already active
   # source .venv/bin/activate
   preloop-sync scan all

   This command tells Preloop Sync to scan all configured trackers and update the database.

API Documentation

When running, the API documentation is available at:

http://localhost:8000/docs

The OpenAPI specification is also available at:

http://localhost:8000/openapi.json

Using the REST API

Preloop provides a RESTful HTTP API:

import requests
import json

# Base URL for the Preloop API
base_url = "http://localhost:8000/api/v1"

# Authenticate and get a token
auth_response = requests.post(
    f"{base_url}/auth/token",
    json={"username": "your-username", "password": "your-password"}
)
token = auth_response.json()["access_token"]
headers = {"Authorization": f"Bearer {token}"}

# Test a tracker connection
connection = requests.post(
    f"{base_url}/projects/test-connection",
    headers=headers,
    json={
        "organization": "spacecode",
        "project": "astrobot"
    }
)
print(json.dumps(connection.json(), indent=2))

# Search for issues related to authentication
results = requests.get(
    f"{base_url}/issues/search",
    headers=headers,
    params={
        "organization": "spacecode",
        "project": "astrobot",
        "query": "authentication problems",
        "limit": 5
    }
)
print(json.dumps(results.json(), indent=2))

# Create a new issue
issue = requests.post(
    f"{base_url}/issues",
    headers=headers,
    json={
        "organization": "spacecode",
        "project": "astrobot",
        "title": "Improve login error messages",
        "description": "Current error messages are not clear enough...",
        "labels": ["enhancement", "authentication"],
        "priority": "High"
    }
)
print(json.dumps(issue.json(), indent=2))

API Endpoints

Preloop provides a comprehensive REST API for authentication, tool management, approval workflows, policy generation, and integrations.

For the complete REST API reference, including interactive Swagger endpoints, please see the official API documentation.

Unified WebSocket

Preloop uses a unified WebSocket connection for real-time updates across the application:

Connection: ws://localhost:8000/api/v1/ws/unified

Message Routing:

• Flow execution updates (flow_executions topic)

• Approval request notifications (approvals topic)

• System activity updates (activity topic)

• Session events (system topic)

Features:

• Automatic reconnection with exponential backoff

• Pub/sub message routing to subscribers

• Topic-based filtering for efficient message delivery

• Session management with activity tracking

• Heartbeat monitoring

Usage in Frontend:

import { unifiedWebSocketManager } from './services/unified-websocket-manager';

// Subscribe to flow execution updates
const unsubscribe = unifiedWebSocketManager.subscribe(
  'flow_executions',
  (message) => console.log('Flow update:', message),
  (message) => message.execution_id === myExecutionId  // Optional filter
);

// Clean up when done
unsubscribe();

Using MCP Tools via API

The Preloop API includes integrated MCP tool endpoints with dynamic tool filtering, allowing any HTTP-based MCP client to connect directly.

Read the MCP Integration Guide in docs.preloop.ai for details on authenticating clients like Claude Code, Cursor, and Windsurf, and setting up workflows or timeouts.

Mobile Push Notifications (iOS/Android)

Open-source users can enable mobile push notifications by proxying requests through the production Preloop server at https://preloop.ai.

Setup Steps:

1. Create an account at https://preloop.ai

2. Generate an API key with push_proxy scope from the Settings page

3. Configure your instance with these environment variables:

# Push notification proxy configuration
PUSH_PROXY_URL=https://preloop.ai/api/v1/push/proxy
PUSH_PROXY_API_KEY=your-api-key-here

4. Enable push notifications in the Notification Preferences page in your Preloop Console

5. Register your mobile device by scanning the QR code shown in Notification Preferences

Once configured, approval requests will trigger push notifications on your registered iOS or Android devices.

Note: The mobile apps (iOS/Watch and Android) are designed to work with self-hosted Preloop instances. They connect to your server URL extracted from the QR code.

Version Checking & Updates

By default, Preloop checks for version updates by contacting https://preloop.ai on startup and once daily. This helps you stay informed about new releases and security updates.

Privacy: Only instance UUID, version number, and IP address are sent. No user data is transmitted.

Opt-out: Set PRELOOP_DISABLE_TELEMETRY=true or DISABLE_VERSION_CHECK=true to disable version checking and telemetry entirely.

For detailed architecture, see ARCHITECTURE.md.

Testing

Preloop uses pytest for unit and integration testing. The test suite covers API endpoints, database models, and tracker integrations.

Running Tests

To run all tests:

# Run all tests
pytest

# Run with verbose output
pytest -v

# Run a specific test file
pytest tests/endpoints/test_webhooks.py

# Run a specific test case
pytest tests/endpoints/test_webhooks.py::TestWebhooksEndpoint::test_github_webhook_valid_signature

Test Structure

• Unit Tests: Located in tests/ directory, testing individual components in isolation

• Integration Tests: Test the interaction between components

• Endpoint Tests: Test API endpoints with mocked database sessions

Testing Webhooks

The webhook endpoint tests (tests/endpoints/test_webhooks.py) validate:

1. Authentication via signatures/tokens for GitHub and GitLab webhooks

2. Error handling for invalid signatures, missing tokens, etc.

3. Organization identifier resolution

4. Database updates (last_webhook_update timestamp)

5. Error handling for database failures

These tests use mocking to isolate the webhook handling logic from external dependencies.

Roadmap

Preloop is evolving into a comprehensive control plane for AI agents. Here's what's coming:

• 🔜 Agent Registry — Register, credential, and manage AI agents as first-class entities

• 🔜 AI Model Gateway — Unified model proxy with cost tracking, rate limits, and usage analytics

• 🔜 Agent Monitoring — Real-time visibility into agent activity, spending, and health

• 🔜 Budget Controls — Per-agent spending caps with alerts and enforcement

Star the repo and watch for updates!

Enterprise Features

Preloop Enterprise Edition extends the open-source core with additional features for teams and organizations:

Contact sales@preloop.ai for Enterprise Edition licensing.

Contributing

Contributions are welcome! Please see our Contributing Guidelines for details on how to get started.

1. Fork the repository

2. Create your feature branch (git checkout -b feature/amazing-feature)

3. Commit your changes (git commit -m 'Add some amazing feature')

4. Push to the branch (git push origin feature/amazing-feature)

5. Open a Pull Request

License

Preloop is open source software licensed under the Apache License 2.0.

Copyright (c) 2026 Spacecode AI Inc.