$Secret: syntax returns empty for Azure Key Vault backed variables in custom environments — 2026.2.0 regression

Description:

• Affected version: 2026.2.0
• Working version: 2026.1.6
• Environment: Windows, custom PowerShell 7.5 environment, Azure Key Vault via Az.KeyVault

Issue: All AKV-backed secret variables return empty when accessed via $Secret:<name> syntax in a custom PS 7.5 environment after upgrading from 2026.1.6 to 2026.2.0.

What works:

• Get-Secret -Name <name> -Vault AzureKeyVault retrieves the value correctly
• Get-SecretVault shows AzureKeyVault registered and set as default
• Plain PSU variables (e.g. $AzureTenantID) resolve correctly
• Same secrets resolve correctly on a separate instance still running 2026.1.6

What doesn't work:

• $Secret:<name> returns empty for any AKV-backed variable
• Affects all AKV secrets, not specific to one variable