Cognito AdminUpdateUserAttributes fails - user name "failed to satisfy constraint" with an incorrect RegEx

The error message you're receiving, "INVALID_PARAMETER 1 validation error detected: Value at 'username' failed to satisfy constraint: Member must satisfy regular expression pattern: [\p{L}\p{M}\p{S}\p{N}\p{P}]+", is indicating that the username you're trying to update does not match the required pattern.

The regular expression [\p{L}\p{M}\p{S}\p{N}\p{P}]+ is a Unicode-aware pattern that matches one or more characters of the following types:

• \p{L}: Any letter character from any language
• \p{M}: Any spacing or combining mark character
• \p{S}: Any symbol character
• \p{N}: Any numeric character
• \p{P}: Any punctuation character

The issue you're facing is likely due to the presence of the parentheses () in the username. The parentheses are not considered valid characters in the regular expression pattern.

To resolve this issue, you can try the following:

1. Modify the username format: Consider modifying the format of the username to remove the parentheses, such as "Bill_Admin" instead of "Bill (Admin)". This should allow the AdminUpdateUserAttributes operation to succeed.

2. Use a different attribute: Instead of updating the username, you can try updating a different user attribute, such as the preferred_username attribute, which may have a different validation pattern.

3. Perform a workaround: As a workaround, you could first use the AdminGetUser operation to retrieve the current user attributes, then use AdminUpdateUserAttributes to update the desired attributes, excluding the username.

Here's an example of how you could perform the workaround:

// Retrieve the current user attributes
GetUserResponse getUserResponse = cognitoIdentityProvider.AdminGetUser(GetUserRequest()
    .WithUsername(username)
    .WithUserPoolId(userPoolId));

// Update the desired attributes, excluding the username
UpdateUserAttributesRequest updateRequest;
updateRequest.SetUserAttributes(getUserResponse.GetUser().GetAttributes());
// Modify the desired attributes here
updateRequest.SetUserPoolId(userPoolId);
updateRequest.SetUsername(username);

// Update the user attributes
UpdateUserAttributesOutcome updateOutcome = cognitoIdentityProvider.AdminUpdateUserAttributes(updateRequest);

If none of these approaches work, you may need to consider contacting AWS Support to investigate further or provide feedback on the SDK behavior.