SentinelGate

<h1 align="center">SentinelGate</h1>

<p align="center"> <strong>Your AI agent has unrestricted access to your machine.</strong><br> Every tool call, shell command, and file read — unchecked.<br><br> SentinelGate intercepts every action before it executes.<br> Deterministic rules. Full audit trail. Single binary.<br><br> _{For developers and security teams running AI agents with MCP.} </p>

<p align="center"> <a href="https://github.com/Sentinel-Gate/Sentinelgate/actions/workflows/ci.yml"><img src="https://img.shields.io/github/actions/workflow/status/Sentinel-Gate/Sentinelgate/ci.yml?style=flat-square&label=CI" alt="CI"></a> <a href="LICENSE"><img src="https://img.shields.io/badge/License-AGPL--3.0-blue?style=flat-square" alt="License: AGPL-3.0"></a> <a href="https://go.dev"><img src="https://img.shields.io/badge/Go-1.25+-00ADD8?style=flat-square&logo=go&logoColor=white" alt="Go 1.24+"></a> <a href="https://github.com/Sentinel-Gate/Sentinelgate/releases"><img src="https://img.shields.io/badge/Release-v2.0-brightgreen?style=flat-square" alt="Release v2.0"></a> </p>

<p align="center"> <a href="#quick-start">Get Started</a> · <a href="https://www.sentinelgate.co.uk">Website</a> · <a href="docs/Guide.md">Docs</a> </p>

<p align="center"> <img src="assets/sentinelgate-demo.gif" width="720" alt="SentinelGate demo"> </p>

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How SentinelGate works

One prompt injection or one hallucination is all it takes.

SentinelGate sits between the AI agent and your system. Every action is intercepted, evaluated against your policies, and logged — before it reaches anything. Denied actions are blocked at the proxy.

<p align="center"> <img src="assets/diagram-how-it-works-2.svg" width="720" alt="How SentinelGate works"> </p>

No code changes. No agent modifications. Single binary, zero dependencies, sub-millisecond overhead.

<p align="center"> <img src="assets/screenshot-hero.png" width="820" alt="Tools & Rules with per-tool Allow/Deny enforcement"> </p>

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Quick start

Install (macOS / Linux):

curl -sSfL https://raw.githubusercontent.com/Sentinel-Gate/Sentinelgate/main/install.sh | sh

Install (Windows PowerShell):

irm https://raw.githubusercontent.com/Sentinel-Gate/Sentinelgate/main/install.ps1 | iex

<details> <summary>Manual download or build from source</summary>

Download from GitHub Releases:

Platform	Archive
macOS (Apple Silicon)	sentinel-gate_darwin_arm64.tar.gz
macOS (Intel)	sentinel-gate_darwin_amd64.tar.gz
Linux (x86_64)	sentinel-gate_linux_amd64.tar.gz
Linux (ARM64)	sentinel-gate_linux_arm64.tar.gz
Windows (x86_64)	sentinel-gate_windows_amd64.zip
Windows (ARM64)	sentinel-gate_windows_arm64.zip

macOS / Linux:

tar xzf sentinel-gate_*.tar.gz
chmod +x sentinel-gate
sudo mv sentinel-gate /usr/local/bin/

Windows: extract the .zip and add sentinel-gate.exe to your PATH.

Build from source (Go 1.24+):

macOS / Linux:

git clone https://github.com/Sentinel-Gate/Sentinelgate.git
cd Sentinelgate && go build -o sentinel-gate ./cmd/sentinel-gate

Windows:

git clone https://github.com/Sentinel-Gate/Sentinelgate.git
cd Sentinelgate; go build -o sentinel-gate.exe ./cmd/sentinel-gate

</details>

Start:

$ sentinel-gate start

  SentinelGate 2.0.0
  ─────────────────────────────────────
  Admin UI:      http://localhost:8080/admin
  Proxy:         http://localhost:8080/mcp
  Upstreams:     1 connected / 1 configured
  Tools:         12 discovered
  Rules:         0 active
  ─────────────────────────────────────

Output may vary depending on your configuration.

Open http://localhost:8080/admin to manage policies, upstreams, and identities. The MCP endpoint is http://localhost:8080/mcp — configure your agent to connect there with an API key.

<p align="center"> <video src="https://github.com/user-attachments/assets/2cb6864e-f00e-4b9e-9c39-b3523c77d50b" width="720" controls autoplay loop muted></video> </p>

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Playground

See SentinelGate block a prompt injection attack — 30 seconds, no setup:

macOS / Linux:

cd examples/playground
./playground.sh

Windows PowerShell:

cd examples\playground
.\playground.ps1

The script creates 3 policies, simulates 4 agent tool calls (1 allowed, 3 blocked), and cleans up after. Only needs bash + curl or PowerShell. Full walkthrough: examples/playground/READMEplayground.md.

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Connect your agent

SentinelGate works with any MCP-compatible client. Point your agent to http://localhost:8080/mcp with an API key:

Client	Setup
Claude Code	claude mcp add --transport http sentinelgate http://localhost:8080/mcp --header "Authorization: Bearer <key>"
Cursor / IDE	Add MCP server in settings with URL http://localhost:8080/mcp
Gemini CLI	MCP config with http transport
Codex CLI	MCP config with http transport
Python / Node.js / cURL	Standard HTTP with Authorization: Bearer <key> header

Full setup snippets for each client: Connect Your Agent

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Features

Deterministic enforcement — Explicit rules, not AI judgment. deny delete_* means denied. Always.

MCP-native — Built as an MCP proxy. Aggregates multiple upstream servers, applies per-tool policies, exposes a single endpoint.

CEL-powered rules — Common Expression Language, the same engine behind Kubernetes, Firebase, and Envoy:

action_arg_contains(arguments, "secret")                      // block by content
action_name == "bash" && !("admin" in identity_roles)             // role-based shell control
dest_domain_matches(dest_domain, "*.pastebin.com")             // outbound blocking

Simple tool patterns (read_*, delete_*) cover most cases. CEL handles the rest.

Full audit trail — Every action logged with identity, decision, timestamp, and arguments. Stream live via SSE, filter, or export.

Admin UI — Browser-based policy editor, test playground, security settings, audit viewer. No config files, no restarts.

Identity and access control — API keys, roles, per-identity policies. Each agent gets isolated credentials.

Content scanning — Bidirectional PII, secrets, and IPI detection on tool arguments and responses. Configurable whitelist with contextual exemptions.

Session-aware policies — CEL functions that use session history for context-dependent rules. Detect patterns like read-then-exfiltrate across multiple tool calls: session_call_count, session_write_count, session_sequence, and more.

Red team testing — 30 built-in attack patterns across 6 categories (prompt injection, tool poisoning, exfiltration, privilege escalation, evasion, resource abuse). Interactive report with one-click remediation.

 

<details> <summary><strong>More features (13)</strong></summary>

Policy templates — Seven pre-built security profiles (Safe Coding, Read Only, Research Mode, Full Lockdown, Audit Only, Data Protection, Anti-Exfiltration). One click to apply, fully customizable after.

Budget and quota — Per-identity usage limits: max calls, writes, deletes per session, rate limiting per minute. Deny or warn when limits are reached. Live progress tracking on the dashboard.

Response transformation — Five transform types applied to tool responses before they reach the agent: redact (regex-based), truncate (size limits), inject (prepend/append warnings), dry-run (mock responses), mask (partial reveal). Test in the built-in sandbox.

Session recording — Record every tool call with full request/response payloads. Timeline replay in the UI, export to JSON or CSV, configurable retention, privacy mode (record metadata only).

Cryptographic evidence — Every decision signed with ECDSA P-256 and hash-chained. Tamper-proof audit receipts for compliance. EU AI Act-ready compliance bundles with coverage mapping.

Tool integrity — Hash-based baseline for tool definitions, drift detection on schema changes, quarantine for mutated tools, diff viewer.

Behavioral drift detection — 14-day baseline vs current behavior comparison. Detects tool distribution shifts, deny rate changes, temporal anomalies, and argument pattern drift.

Agent health dashboard — Per-agent health metrics (deny rate, drift score, violations) with 30-day sparklines, baseline comparison, and cross-agent overview. CEL variables for health-based policies.

Permission health & shadow mode — Identifies over-privileged agents by comparing granted vs actual tool usage. Auto-tighten suggestions with one-click apply.

FinOps cost explorer — Per-tool cost estimation, per-identity budgets with threshold alerts, cost drill-down, budget guardrail creation via Policy Builder.

Namespace isolation — Role-based tool visibility with whitelist/blacklist glob patterns.

OpenTelemetry export — Stdout span export for every tool call with identity, decision, and latency.

Human-in-the-loop — Escrow workflow for sensitive operations. Approve/deny with decision context, session trail, and signed audit note.

</details>

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Admin UI

Tools & Rules	Audit Log
<img src="assets/screenshot-rules.png" width="410" alt="Tools & Rules with per-tool Allow/Deny enforcement">	<img src="assets/screenshot-audit.png" width="410" alt="Audit log viewer">

Content Scanning	Policy Test
<img src="assets/screenshot-security.png" width="410" alt="Content scanning with Monitor and Enforce modes">	<img src="assets/screenshot-policy-test.png" width="410" alt="Policy test playground">

13 pages: Dashboard, Getting Started, Tools & Rules (with Transforms, Policy Test, and Simulation tabs), Access (with Quota management), Audit Log, Sessions, Notifications, Compliance, Permissions, Security, Red Team, FinOps, and Clients (with Agent Health).

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Configuration

[!NOTE] Works with zero configuration. Everything is managed from the Admin UI and persisted automatically.

For infrastructure tuning, an optional YAML config is available:

server:
  http_addr: ":8080"
rate_limit:
  enabled: true
  ip_rate: 100

Full reference: Configuration · CLI · API

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Limitations

[!CAUTION] SentinelGate is an MCP proxy — it controls what tools and data your agents can access through the MCP protocol. It is effective against mistakes, prompt injection, and overreach. For full OS-level isolation, combine with container or VM sandboxes.

Full threat model.

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SentinelGate Pro

Extended retention · SIEM integration · SSO · Multi-tenancy · Advanced FinOps with billing API integration · Cross-agent health export — sentinelgate.co.uk

Contributing

Bug fixes, features, docs, and feedback welcome. See CONTRIBUTING.md. A CLA is required for code contributions — see CLA.md.

License

AGPL-3.0 — free to use, modify, and self-host. For commercial licensing, contact us.

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<p align="center"> <a href="https://www.sentinelgate.co.uk">Website</a> · <a href="docs/Guide.md">Docs</a> · <a href="https://github.com/Sentinel-Gate/Sentinelgate/releases">Releases</a> </p>