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Agent bridge ​

The agent bridge is an Extension.js framework feature. When extension dev runs, the framework loads a privileged companion alongside your extension and opens a channel on 127.0.0.1 that a human (a sidebar), a script (a file), or an AI agent (a live stream) uses to observe every extension context and, when you opt in per session, act on it. It is local and open source, needs no account, and sends nothing off your machine. The data plane, the trust levels, and the honest limits live in the framework's Debugging section.

What the platform adds ​

The MCP server reaches the same machinery from an agent. The tools extension_logs, extension_inspect, extension_eval, extension_storage, extension_reload, extension_open and extension_dom_snapshot connect to the bridge's channel exactly as any other client would, so the agent and the CLI always see the same thing. The platform stores none of it: bridge data stays on the developer's machine.

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