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A browser may discard a background tab to save memory. A discarded Penpot tab reloads when the user returns to it and loses its MCP session. Add mcp/packages/browser-extension, a Manifest V3 extension for Chrome and Firefox, built from one source into dist/chrome and dist/firefox. It is written in TypeScript, bundled with esbuild and imports the protocol types from mcp-common. The package joins the mcp workspace, so the build, test and fmt scripts of mcp/ cover it; the server release build skips it. Its content script runs on design.penpot.app, on the test environments under penpot.dev and on local development instances. It asks the page for its MCP session on load, again when the page says it is ready and when the page returns from the back/forward cache, and forwards each valid session announcement to the background. It accepts only messages the page posted on its own window from its own origin, and posts its hello to that origin only. It also tells the background when the page is hidden. The background records which tab holds each MCP session. A tab holds the session it last announced as connected, until its page announces a disconnect, is hidden, or the tab is closed or replaced. The map lives in chrome.storage.session, so it survives restarts of the background and clears when the browser closes. While a tab holds a session, the browser may not discard it automatically. The extension asks only for the storage permission. Chrome runs the background as a service worker; Firefox runs it as an event page and needs the add-on ID, mcp-extension@penpot.app, and Firefox 140. The toolbar popup lists the connected tabs. The icon is the Penpot logo, white on a black rounded square, with the SVG source next to the PNGs. A README explains how the extension works and how to build and load it.