Upcoming Change to the Microsoft Teams Desktop Client on Windows: New Module Host for Calling

2025-12-04 3 min read Teams Communications Microsoft Teams "Erwin Bierens"

Upcoming Change to the Microsoft Teams Desktop Client on Windows: New Module Host for Calling

Microsoft is introducing an important architectural update to the Teams Desktop Client for Windows that enhances performance, reduces startup time, and improves the reliability of calling features. For IT administrators, UC engineers, and organizations using Microsoft Teams Calling, this update requires a few proactive adjustments.

What Is Changing?

In the current Teams architecture, the main application process ms-teams.exe also launches and manages the calling stack. To improve performance and create cleaner separation, Microsoft is introducing a dedicated child process for handling all calling-related functionality.

Processes

You will now see the following process structure in Task Manager:

ms-teams.exe – main application
ms-teams_modulehost.exe – new child process responsible for the calling stack

This change applies only to Windows clients.

Microsoft has already included ms-teams_modulehost.exe in the Teams Run directory, so organizations can begin preparing their endpoint and quality-of-service policies ahead of full enablement.

Why the Change Matters

Separating the calling stack into its own process enables:

Faster initialization of audio and calling components
Better overall stability during calls
Clearer process isolation for diagnostics
More granular policy and QoS control
Reduced likelihood of full-client instability

For environments with strict QoS, EDR, or firewall configurations, this architectural change matters particularly because these systems often target executable names directly.

Required Administrative Actions

To avoid interruptions to Teams Calling, organizations should update their configurations as soon as possible.

1. Allowlist the New Calling Process

Add ms-teams_modulehost.exe to:

Endpoint security tools
Antivirus/EDR allowlists
App control and whitelisting policies
Firewall rules
Monitoring systems

It must receive the same permissions currently assigned to ms-teams.exe.

Because the new executable already appears in the run directory, administrators can safely include it in policies now.

2. Duplicate QoS Settings for the New Process

If your environment applies QoS to Teams Calling, ensure that the configuration covers both executables.

Important:

Do not remove existing QoS settings for ms-teams.exe
Add the same QoS configuration for ms-teams_modulehost.exe

For a complete walkthrough of QoS configuration, see my earlier guide:
Quality of Service Script for Microsoft Teams
https://erwinbierens.com/quality-of-service-script-for-microsoft-teams/

Official Microsoft guidance can be found here:
https://learn.microsoft.com/en-us/microsoftteams/qos-in-teams-clients

3. Review Your Endpoint and Network Policies

Confirm that the following policies reference both processes:

Intune device configuration and App Protection Policies
GPO-based rules targeting Teams executables
Firewall and routing prioritization rules
SBC and VoIP infrastructure QoS configurations
Local machine allowlists and application control policies

Any environment that identifies processes by name must be updated to prevent dropped calls or degraded call quality.

Final Thoughts

The introduction of ms-teams_modulehost.exe marks a significant improvement to Teams calling performance and stability. By preparing your endpoint, network, and QoS configurations now—before the new architecture becomes active—you ensure a seamless calling experience for users.