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The Char Extension is a Chrome extension that connects browsers to the Tool Hub. It adds tools to legacy portals, third-party SaaS, and any application where you can’t embed Char directly.

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The problem

Not every application will add a script tag for you. Legacy portals maintained by another team. Third-party SaaS you don’t control. Internal tools built years ago that nobody wants to touch. You want AI agents to interact with these applications. But you can’t modify them.

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How it works

The extension’s service worker connects to the Tool Hub via WebSocket—same protocol as the embedded agent, different runtime. User scripts inject into matching pages via Chrome’s user scripts API. They call registerTool() to expose functionality. The extension aggregates tools from all tabs and uplinks them to the Hub.

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Where it runs

EnvironmentUse case
Local browserAdd tools to apps you use daily
Cloud browserAutonomous Char for unattended execution
The architecture is identical. Same extension, same Hub connection, different runtime.

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What you get

Tools where you couldn’t have them. Legacy applications become AI-accessible without modifying their source code. Org-level scripts. Scripts are defined at the org level and shared across users. Everyone gets the same tools for the same applications. Same governance. Tool calls from the extension flow through the same governance layer as everything else—access control, guardrails, approvals, audit.

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See also

User Scripts

Write scripts that inject tools

Testing with CDP

Test extension tools from Claude Code

Autonomous Char

Run unattended in cloud browsers