AgentGate

One-line firewall for AI coding agents. Intercepts every tool call, network request, and human approval — let Claude Code / Cursor / Codex touch what you allow, block what you don't, ask for the rest.

AgentGate sits between your AI coding agent and the rest of your system. It ships as three small pieces you wire up in 60 seconds:

1. agentgate install-hook — registers a PreToolUse hook with Claude Code (or any MCP-compatible agent) that intercepts Bash / Read / Write / Edit / WebFetch / Grep / Glob calls.
2. agentgate proxy — a mitmproxy add-on that intercepts every outbound HTTP(S) request and applies your domain allow/deny list.
3. agentgate dashboard — a single-page HTML viewer for the audit log, with live stats, time series, and per-rule breakdowns.

When an ask action fires, AgentGate posts to a Slack incoming webhook and waits (up to 60s by default) for a human to click Allow or Deny at http://your-host:8765/approve/<token>.

Quick start

# 1. Install
git clone https://github.com/FelixMa01/agentgate && cd agentgate
uv sync

# 2. Init a policy + audit DB in your project
cd ~/code/my-project
agentgate init --dir .                 # writes ./policy.yaml + ./audit.db

# 3. Wire it into Claude Code (writes .claude/settings.local.json)
agentgate install-hook \
    --policy ./policy.yaml \
    --db ./audit.db \
    --target .                         # project scope (or --scope user for all projects)

# 4. (optional) Start the network proxy
agentgate proxy -p ./policy.yaml --db ./audit.db   # listens on :8080
export HTTP_PROXY=http://127.0.0.1:8080
export HTTPS_PROXY=http://127.0.0.1:8080

# 5. (optional) Start the approval server (for ASK actions)
agentgate approval-server --port 8765

# 6. Watch the dashboard
agentgate dashboard --db ./audit.db   # http://127.0.0.1:8766

Policy format (policy.yaml)

version: 1
default: allow       # what to do when no rule matches

rules:
  # Match glob-style — * matches across slashes
  - id: deny-rm-rf
    name: Block destructive rm
    match:
      tool: Bash
      command: "rm -rf /*"
    action: deny
    reason: "Mass deletion outside repo"

  # Match a list of patterns — any match fires
  - id: deny-secrets
    name: Block reading secrets
    match:
      tool: Read
      file_glob: ["*.pem", ".env*", "*id_rsa*"]
    action: deny

  # Use ~regex~ prefix to drop into regex land
  - id: ask-outbound
    name: Require approval for outbound network
    match:
      tool: Bash
      command: "~\bcurl\b|\bwget\b"
    action: ask
    reason: "Outbound network from agent"

network:
  allowed_domains:
    - github.com
    - "*.pypi.org"
    - openai.com
    - "*.openai.com"
  denied_domains:
    - pastebin.com
    - "*.transfer.sh"
  require_https: true

Actions

Pattern matching

• Plain strings are exact matches.
• Glob (*, ?) patterns use Python's fnmatch.translate, so * does match /.
• A leading ~ switches to regex mode: "~\\brm\\s+-rf\\b".
• Patterns can be a list — any match fires.
• Suffix _glob on a key (e.g. file_glob) tries the base name (file) if the suffixed key isn't in the event.

Architecture

   ┌──────────────────────────┐
   │   Claude Code / Codex    │
   │   (Bash, Read, Write,    │
   │    Edit, WebFetch, ...)  │
   └────────────┬─────────────┘
                │ tool call
                ▼
   ┌──────────────────────────┐         ┌─────────────────┐
   │  bin/agentgate-hook.py   │ ──────▶ │  policy.yaml    │
   │  (PreToolUse, JSON stdin │         │  + SQLite audit │
   │   JSON stdout response)  │ ◀────── │  (events table) │
   └────────────┬─────────────┘         └─────────────────┘
                │ if ask → Slack + wait
                ▼
   ┌──────────────────────────┐
   │  approval server :8765   │
   │  GET /approve/<token>?d= │
   └──────────────────────────┘

   ┌──────────────────────────┐         ┌─────────────────┐
   │  mitmproxy add-on :8080  │ ──────▶ │  policy.yaml    │
   │  (every HTTP request)    │         │  network section│
   └──────────────────────────┘         └─────────────────┘

The hook, proxy, and approval server all read the same policy.yaml and write to the same audit.db. The dashboard reads only the DB.

CLI

agentgate init                       # scaffold a default policy.yaml + audit.db
agentgate eval -p policy.yaml --db audit.db --event-json '{"tool":"Bash","command":"x"}'
agentgate audit --db audit.db --limit 20
agentgate stats --db audit.db
agentgate validate -p policy.yaml

agentgate install-hook -p policy.yaml --db audit.db --target .
agentgate uninstall-hook --target .

agentgate proxy -p policy.yaml --db audit.db --listen-port 8080
agentgate approval-server --port 8765
agentgate dashboard --db audit.db --port 8766

agentgate ask-test -p policy.yaml --db audit.db --event-json '{...}'

Slack approval flow

Set AGENTGATE_SLACK_WEBHOOK=https://hooks.slack.com/services/... and AgentGate will post a Block Kit message with Allow / Deny buttons. Without a webhook, it falls back to writing the JSON to /tmp/agentgate-asks.jsonl so you can wire your own channel.

When the human clicks Allow / Deny, the request hits http://your-host:8765/approve/<token>?d=allow. The approval server writes the decision into the SQLite approvals table; the waiting hook (which may be a different process) sees the update via in-process notification + DB poll fallback.

If no human responds within AGENTGATE_ASK_TIMEOUT (default 60s), the hook denies by default — fail-closed.

Why not just use the agent's built-in permissions?

You can — but AgentGate gives you:

1. Network egress control. Built-in permissions don't see what your agent calls over the wire.
2. Centralized policy. One YAML for the whole team, instead of scattered .claude/settings.json files.
3. Cross-tool unified audit. One DB for every tool, hook, and proxy — searchable, time-seriesed, shareable.
4. Human-in-the-loop without leaving your chat. Slack approve/deny buttons beat terminal prompts.
5. Postmortem-friendly. Every decision has a rule_id, reason, and full event payload.

Status

🟢 Day 5 shipped. See /api/stats on the dashboard for live numbers.

48 unit tests passing. End-to-end verified on macOS (Apple Silicon, Python 3.13 via uv).

License

Apache 2.0.