Skip to main content
You can connect as many agents as you like. They share one companion and access to its connected browser profiles and developer contexts, while each keeps its own tab ownership and recordings. Chrome, Brave, Firefox and Zen extensions and separate developer contexts can connect together. See Using multiple browsers. The dashboard’s Graph page shows established agent sessions, connected browser profiles and developer contexts linked through that companion. It updates as connections change and can be hidden with Settings → Connection graph.

​
One companion, many clients

The first companion process to start owns port 9223. Every companion started afterwards, by any other client, finds the port taken and becomes a relay: a thin stdio server that forwards tools/list and tools/call to the owner over the HTTP endpoint. From the client’s point of view nothing changes. Each extension profile connects once to that owner, regardless of how many agents are using it. Stdio clients, HTTP clients and relays reach one companion, which connects multiple Chromium and Firefox profiles and separate developer browsers Stdio clients, HTTP clients and relays reach one companion, which connects multiple Chromium and Firefox profiles and separate developer browsers The diagram shows transport routing. Moving dots illustrate the connections; they do not display live activity. Reduced-motion settings show a still diagram. The relay passes the downstream client’s name through, so the owner still knows which agent is calling. When the owner stops (its client quit or it was killed), the first relay to notice takes the port over and keeps serving its own client; the other relays reconnect to it on their next call, and each extension reconnects on its own. Inspection sessions and developer browsers of the old owner do not survive the hand-over. Call browser_status again to get current browser and tab IDs.
If the port is taken by something that is not a companion, the relay retries for a few seconds and then answers every tool call with an error asking you to stop the other process or use --port. It never guesses a different port on its own, because the extension is configured for one specific port.

​
What is per agent

When two agents both leave tabId empty, each gets its own most recently opened tab. If neither owns a tab and several tabs are shared, the tool asks for an explicit tabId rather than guessing. When working across browsers, pass the returned tabId explicitly on page tools. Use browserId to open a tab in an extension browser and context to open one in a developer session. Tab ownership chooses a default target; it does not prevent another agent from using an accessible tab by ID.

​
Verifying

shows exactly one bun process listening. pgrep -fl browspark-mcp shows one owner plus one relay per additional stdio client. Each dashboard’s Activity page (when the log is on) lists which agent issued commands to that profile.