Bug:
When Cursor Agent runs (especially shell/network tools), Windows user proxy is set to:
ProxyEnable = 1
ProxyServer = http://127.0.0.1:57126 (port varies)
Effect:
Browser, Claude, ChatGPT, and other apps lose internet
Cursor itself stays connected
Clearing the proxy is temporary; next agent tool use re-enables it
Hey, thanks for the detailed report. Let’s dig into what’s going on here.
The local listener on 127.0.0.1:<port> you’re seeing is the agent’s per-command network filter sandbox. It’s expected, and by default it only affects the command processes the agent launches. Cursor itself does not change the system Windows proxy settings in the registry HKCU\...\Internet Settings.
If that proxy is getting written system-wide and breaking other apps, on Windows it usually means the agent ran a command during an auto-run session that changed the registry or system proxy. On Windows the sandbox doesn’t isolate the registry, and in auto-run mode commands run without confirmation.
Can you check the agent transcripts for those sessions and look for commands like Set-ItemProperty ... Internet Settings, reg add ... Internet Settings, or netsh? That would confirm the mechanism. If you find anything, paste it here, it’d be super helpful.
What you can do right now:
Review your auto-run settings. Switch to requiring confirmation for system-touching commands, or add reg, Set-ItemProperty, netsh to the command denylist.
Add a project rule that explicitly forbids the agent from changing system proxy settings.
Your scheduled task that resets ProxyEnable when it’s 127.0.0.1 or localhost is a fine stopgap. You can keep it for now.
On its own, the system proxy staying broken for other apps shouldn’t happen. I’ve passed this to the team so they can look at it on the sandbox side. I’ll post here if there’s an update.