Fix: Azure KeyVault 401 Unauthorized Error in Visual Studio 2022

The Error

When debugging in Visual Studio 2022:

Azure.RequestFailedException: 401 Unauthorized

Visual Studio Specific Fix - 1 Min

1. In VS2022 go to Tools → Options → Azure Service Authentication.

2. Sign in with the same Azure AD account that has access to KeyVault.

3. Restart Visual Studio and Clean + Rebuild solution.

4. Still failing? Check Output → Azure Service Authentication logs.

Quick Fix - General

1. Local dev: az login. 2. Managed Identity: Enable on App Service. 3. KeyVault Access Policy: Grant Get/List to app. 4. Code: builder.Configuration.AddAzureKeyVault(new Uri(vaultUri), new DefaultAzureCredential())

Root Cause

Visual Studio uses a different token cache than az cli. If VS is signed into wrong tenant, DefaultAzureCredential fails with 401.

Also see: Fix 401 in Docker | Original 401 Fix