This is a known bug on Windows. The plugin loader’s git invocation disables credential helpers (including Windows Credential Manager / GCM) via hard-coded flags, which is why the fetch fails even though your system git can authenticate to the same repo just fine. Your observation about shallowClone succeeding via a different code path is consistent with what we’ve been tracking.
Our team is aware and actively working on a fix. We’re tracking the same issue in detail: Private team marketplace plugin install fails on 3.2.11 – three-stage clone fallback all broken. That thread has two confirmed workarounds:
Option A: _netrc with a PAT (simplest for teams)
winget install GitHub.cli
gh auth login --hostname github.com --git-protocol https --web
$token = gh auth token
@"
machine github.com
login x-access-token
password $token
"@ | Out-File "$env:USERPROFILE\_netrc" -Encoding ASCII -Force
Option B: SSH key with explicit config (no PAT rotation needed)
Set up a dedicated SSH key (id_ed25519_cursor), add an explicit Host github.com block in ~/.ssh/config with IdentityFile + IdentitiesOnly yes, and authorize the key via SSO for your org.
Both workarounds bypass the credential muzzle because _netrc is read natively by curl before credential helpers, and SSH is the first stage attempted before HTTPS.
We’ll post an update here once a fix ships.