fatal: Authentication failed

Git submodules add a layer of complexity to Authentication Failed that standard documentation does not cover. Each submodule is an independent repository with its own HEAD, branches, and remote — so Authentication Failed may occur in the outer repository, inside a submodule, or both. When cloning a repository with submodules, always use git clone --recurse-submodules. If you cloned without this flag, run git submodule update --init --recursive. For CI pipelines, ensure the pipeline configuration checks out submodules — GitHub Actions requires submodules: recursive in the checkout step, and CircleCI requires submodules: true. For sparse checkouts (enabled with git sparse-checkout), some files are intentionally absent from your working directory, which causes Authentication Failed if a script expects those files to exist. Run git sparse-checkout list to see which paths are included and add missing paths with git sparse-checkout add <path> before retrying the failing operation.