Multi-device simultaneous sessions broken since v1.0.15/1.0.16 — logging in on Device B automatically logs out Device A

[lamro-artsuew]

Describe the bug

Bug Report

Description

Since approximately v1.0.15–1.0.16, logging into Copilot CLI on a second device
automatically invalidates/logs out the session on the first device.

This worked correctly for months before this regression appeared.

Steps to Reproduce

1. Log in on Device A → session works fine
2. Log in on Device B (same GitHub account)
3. Device A is immediately logged out / session invalidated

Expected Behavior

Both devices should maintain independent, simultaneous active sessions
(as was the case before v1.0.15).

Actual Behavior

New login on any device invalidates all other active sessions for the same account.

Environment

• Copilot CLI version: 1.0.18
• OS: Windows
• Plan: Copilot Pro
• Auth method: OAuth device flow

Additional Context

This is a regression. Multi-device usage worked fine for months prior to
the auth/user-switcher changes introduced in v1.0.15–1.0.16:

• 1.0.16: "MCP servers load correctly after login, user switch, and /mcp reload"
• 1.0.15: "User switcher and /user list display accounts in alphabetical order"

These changes appear to have introduced a side effect where sessions are
now treated as single-instance per account rather than per-device.

Affected version

No response

Steps to reproduce the behavior

No response

Expected behavior

No response

Additional context

No response