Keyboard Input Lost in RouteMatch Application When Using Seamless Mode in Parallels RAS

Symptoms

Users accessing the RouteMatch application through Parallels Remote Application Server in Seamless Mode (Published Application / memshell) may experience intermittent keyboard input issues.

The issue may present as follows:

• Keyboard input is lost after switching applications
  When switching from the RouteMatch session to a local application (e.g., Notepad or a web browser) and then returning, keyboard input is no longer accepted.
• Temporary input followed by failure
  After returning to the remote session, keyboard input may work for approximately 1–2 seconds, then stop completely.
• Window appears active but does not accept input
  The RouteMatch window remains active at the OS level (e.g., ALT+SPACE opens the system menu), but text fields do not accept keystrokes.
• Manual interaction restores input
  Keyboard functionality is restored only after the user clicks directly inside a text field.

Cause

This issue is caused by an application-specific interaction between RouteMatch and the Parallels RAS seamless engine (memshell).

RouteMatch may take additional time to process internal focus changes. When users switch back to the session, this can lead to a timing conflict between the application's internal focus handling and the memshell window activation process.

As a result, the application window appears active, but keyboard input is not properly routed to text input controls.

Resolution

Option 1: Apply registry workaround

Apply the following registry setting on each affected RDSH server:

Path: HKLM\Software\Parallels\Wow6432Node\MemShell
Value Name: ActivationMode
Value Type: REG_DWORD
Value Data: 1

This setting adjusts the memshell activation behavior and prevents input handling issues.

Note: This workaround requires Parallels RAS 21.1 Update 1 or later.

Important considerations

Setting ActivationMode = 1 disables the use of AttachThreadInput().

While this improves keyboard input reliability, it may introduce minor side effects, such as:

• Remote windows not restoring focus automatically
• Remote windows appearing in front of local windows
• Inconsistent window z-order behavior when multiple sessions are active

Option 2 (Recommended): Upgrade RAS

For a permanent resolution without side effects, upgrade to Parallels RAS 21.2 or later.

This version includes improvements to the seamless engine activation logic and resolves the issue without requiring registry changes.

Additional Notes

• This issue is specific to certain application behaviors and may not affect other published applications.
• If similar symptoms occur in other applications, further investigation may be required.