I want to know the roaming threshold for MS OS.

Hello,

Microsoft hasn't published the exact details for dBm threshold into wireless connections, but the industry standards are:

-50 dBm: This is considered an excellent signal strength.
-60 dBm: This is a good signal strength.
-70+ dBm: This is an unreliable signal strenght.

In Windows you can adjust the sensitivity for roaming BSSID signals following the next steps:

1.Open Device Manager.
2.Locate Network Adapters.
3.Select your network or wireless device
4.Right-click > Properties > Select the Advanced tab.
5.Choose Roaming Aggressiveness (or Sensitivity)
6.Set the preferred value from the drop-down menu:
-Lowest
-Medium-low
-Medium
-Medium-High
-High

Explanation:
Lowest: Your device will not roam.
Medium-Low: Roaming is allowed.
Medium: It is a balanced setting between roaming and performance.
Medium-High: Roaming is more frequent.
Highest: The device continuously tracks the WiFi quality. If any degradation occurs, it tries to find and roam to a better access point.

--If the reply is helpful, please Upvote and Accept as answer--

There is no official documentation from Microsoft, but you can change WiFi Roaming Sensitivity.

Check this article:

Change WiFi Roaming Sensitivity or Aggressiveness to improve Wi-Fi reception & performance