## TL;DR

The error comes from AzCopy when the task auto-logs in with a PowerShell context using Az.Accounts 5+ (or latest Az modules 14.x), which changed the token JSON shape that AzCopy parses.

## Steps

1. AzureFileCopy@6 fails with: Failed to perform Auto-login: json: cannot unmarshal object into Go struct field .Token of type string. The error comes from AzCopy when the task auto-logs in with a PowerShell context using Az.Accounts 5+ (or latest Az modules 14.x), which changed the token JSON shape that AzCopy parses.

2. The task team shipped a fix for this in the AzureFileCopy task itself (deployed to all rings): make sure you are on a task version newer than the one referenced in the fix PR. If you cannot pick up the new task version, pin the Az.Accounts PowerShell module to a pre-5.x version on the agent as a workaround.

## When to use

You are seeing this: AzureFileCopy@6 fails with: Failed to perform Auto-login: json: cannot unmarshal object into Go struct field.Token of type string. Use this skill when you run into "AzureFileCopy@6: Auto-login with PowerShell context fails".

## When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

## Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

## Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.