PowerShell Universal Bug Report: `ArgumentOutOfRangeException` in `UDRunspaceFactory.GetRunspace()` when `SessionTimeout = 0`

Product: PowerShell Universal
Version: 5.6.12

Summary

We experienced intermittent API failures in PowerShell Universal where API endpoints would return HTTP 400 and log a System.ArgumentOutOfRangeException during runspace creation. The exception is thrown inside PowerShell Universal (UDRunspaceFactory.GetRunspace()), before any endpoint script code is executed.

The issue was resolved by changing SessionTimeout from 0 (infinite) to a positive integer (e.g., 60 minutes).

Symptoms

• Some requests succeed, but periodically requests fail with:
• HTTP 400
• Error log: System.ArgumentOutOfRangeException: The added or subtracted value results in an un-representable DateTime. (Parameter 'value')
• The failure happens before the endpoint code starts executing.

Stack Trace (excerpt)

System.ArgumentOutOfRangeException: The added or subtracted value results in an un-representable DateTime. (Parameter 'value')

at System.DateTime.ThrowDateArithmetic(Int32 param)

at System.DateTime.AddMinutes(Double value)

at UniversalDashboard.Services.UDRunspaceFactory.GetRunspace() in ...\UDRunspaceFactory.cs:line 37

at UniversalAutomation.Host.PowerShellApiService.ExecuteRequest(ApiRequest request) in ...\ApiService.cs:line 171

Configuration that triggers the issue

In .universal/settings.ps1:

$Parameters = @{

# ...

SessionTimeout = 0

# ...

}

Set-PSUSetting @Parameters

Expected behavior

• SessionTimeout = 0 (“no limit / infinite”) should not cause API failures.
• Runspace creation should be stable and should not throw ArgumentOutOfRangeException.

Actual behavior

• With SessionTimeout = 0, PowerShell Universal intermittently fails to create a runspace.
• PSU internally calls DateTime.AddMinutes(...) (seen in stack trace) and triggers a DateTime overflow (ArgumentOutOfRangeException).
• Endpoint execution is aborted and the API returns HTTP 400.

Workaround / Fix

Changing SessionTimeout to a positive value resolves the issue:

$Parameters = @{

# ...

SessionTimeout = 60

# ...

}

Set-PSUSetting @Parameters

After this change:

• The intermittent ArgumentOutOfRangeException stopped occurring.
• API endpoints became stable again.

Why this appears to be a platform bug

• The stack trace points entirely to PowerShell Universal internals (UDRunspaceFactory.GetRunspace()), not to endpoint scripts.
• The failure occurs before the endpoint code runs, suggesting a runspace/session housekeeping edge-case.
• Even if SessionTimeout=0 is considered a special value, the platform should handle it gracefully and not crash during runspace creation.

Request

Please:

• Confirm whether SessionTimeout = 0 is a supported configuration.
• Investigate and fix the DateTime.AddMinutes overflow in UDRunspaceFactory.GetRunspace() when SessionTimeout=0.
• Provide recommended configuration guidance if 0 should not be used.