Bartholomew Keystone — Control What Your AI Agent Can Do

Give your AI agent a signed permission slip. It can only do what you said it could.

What It Does

Right now, AI coding agents work with all-or-nothing access. If you give Cursor or Copilot permission to run code, it can run anything — including things you didn't intend.

Keystone fixes that. You issue a cryptographically signed passkey that defines exactly what the agent can and can't do. Then Keystone enforces those limits on every action the agent attempts.

Guard vs. Keystone — Start Here

	Guard	Keystone (this extension)
What it does	Automatically blocks known-dangerous code and credential leaks	Lets you define custom rules — what files, commands, and actions are allowed
Install order	Install Guard first	Add Keystone for fine-grained control
Get Guard	Install Bartholomew Guard	You're here

What You Can Control

When you issue a passkey, you decide:

Permission	Example
Which files the agent can write	Allow `src/` only, block everything else
Which commands are allowed	Allow `pytest`, `npm test` — block `rm`, `curl`, `sudo`
Which external domains it can reach	Allow `github.com`, block everything else
How long the permission lasts	Session-only, or time-bounded

Every decision the agent makes is logged with a tamper-evident Ed25519 signed receipt — so you always have a record of what it did.

How It Works

Press Ctrl+Shift+P then run Keystone: Issue Agent Capability Passkey
Set your rules — allowed paths, allowed commands, expiry
Keystone generates a signed .btp_keystone.json permission file
The agent can now only act within what you defined — anything outside gets blocked instantly

Commands

Press Ctrl+Shift+P (or Cmd+Shift+P on macOS):

Command	What It Does
`Keystone: Issue Agent Capability Passkey`	Create a new signed permission for your agent
`Keystone: Inspect Active Agent Clearance`	See what the current passkey allows
`Keystone: Revoke Current Agent Passkey`	Immediately remove the agent permissions
`Keystone: Validate Agent Action against Passkey`	Test whether a specific action would be allowed

Open Source

Bartholomew Keystone is MIT licensed and fully open source.

bartholomew.info
Guard Extension — install this first
Python: pip install btp-guard
npm: npm install btp-guard

Bartholomew Keystone — Agent Capability Passkey

Bartholomew