Setting chat.agent.sandbox.fileSystem.mac forcefully enables chat.agent.sandbox.enabled on restart

[jruales]

Issue Description

When configuring chat.agent.sandbox.fileSystem.mac in user settings, the chat.agent.sandbox.enabled setting is forcefully enabled on every VS Code restart, preventing users from opting out of the sandbox even if they explicitly disable it.

Steps to Reproduce

1. Add the following to your user settings:

   "chat.agent.sandbox.fileSystem.mac": {
     "denyRead": [],
     "allowWrite": ["."],
     "denyWrite": []
   }

2. Set chat.agent.sandbox.enabled to "off" via the settings pane (This will remove it from the settings JSON, since "off" is the default)
3. Restart VS Code
4. 🐛Observe that chat.agent.sandbox.enabled is automatically set back to "on"

Expected Behavior

Setting a filesystem configuration should not forcefully override the parent enabled setting.

Additional Context

Initially, I thought this might be related to ExP experiments changing from "setting defaults" to "forcefully setting values," but it appears this behavior is specific to the chat.agent.sandbox.enabled setting when filesystem configurations are present.

This seems like either:

1. Unintended coupling between the filesystem config and the enabled flag
2. Missing documentation that the presence of filesystem config implies enablement
3. A policy enforcement that should be made more explicit to users

[jruales]

Verified that the same issue happens when setting the linux sandbox setting and not only the mac one

[eleanorjboyd]

I was seeing the default value for chat.agent.sandbox.enabled is on- is that impacted by a exp? If this is the case, do these steps still work to verify or does the second one switch to Set chat.agent.sandbox.enabled to "on"