Minimum Environment Permissions (Security Roles) for Copilot Studio Agent in Teams?

Hi Copilot Studio Community!

I’m facing a strange permissions (Security Roles) challenge when sharing an Agent with users on Teams, and I’m looking for the best practice to determine the minimum required privileges.

The Scenario:
I built an Agent grounded in a SharePoint Knowledge Base.
The end-users currently have:
- Read access to the SharePoint Document Libraries.
- View-only access to the Agent when shared from Copilot Studio.
- No permissions at the Environment level in Dataverse.

The Issue:
When I share the Agent link on Teams, users add it successfully. However, when they ask a question, the Agent immediately triggers the Fallback Topic (acting as if it has no information to pull from or can't access SharePoint).

The Strange Behavior (Workaround):
I discovered that if I temporarily grant the user the following high privileges:
1. Environment Maker role.
2. Bot roles (Bot Contributor, Bot Transcript Viewer, Bot Viewer).
3. Editor permission on the Agent.

Then, if the user tests a question inside the Copilot Studio canvas, it answers correctly. After that, if they test it in Teams, it works perfectly there too!
The weirdest part: if I immediately revoke all these high privileges (returning the user to a simple Viewer with no Environment Access), the Agent continues to work normally for them in Teams and fetches answers from SharePoint without any issues!

My Question to the Experts:
1. Since I don't want (and for security reasons, shouldn't) grant end-users roles like Maker or Editor, what are the exact minimum basic permissions (Security Roles) at the Environment/Dataverse level (e.g., Basic User) that a user must have just to chat with the Agent in Teams successfully from the first try?
2. Is there a technical explanation for why the Agent keeps working in Teams after revoking the permissions? Is it just Token Caching, or is there something else at play?

I would highly appreciate your insights!