A plugin installs into a directory named after it, so two specs resolving to the same name compete for it. vim.pack.add finds out only when git refuses the second clone with destination path '.../ZSnip.nvim' already exists and is not an empty directory — a message that names neither spec and aborts setup() for the whole config.

Hit while migrating a config: one spec file declared zuqini/ZSnip.nvim, another listed zuqini/zsnip.nvim in its dependencies.

Same repository, different casing. Git hosts match owner and repo case-insensitively, so these are one plugin. They now fold onto the casing imported first and their specs merge, exactly as if both had been written alike. Folding happens in normalize_source — the single funnel both import_one_spec and register_dependencies go through, so dependency_graph is keyed by the surviving source too. Local sources are deliberately not folded: on a case-sensitive filesystem two paths differing in case are two directories.

Genuinely different plugins claiming one name (alice/shared.nvim vs bob/shared.nvim). Reported against both sources, keeping the one imported first:

zpack: skipping https://github.com/bob/shared.nvim — it resolves to the same
plugin directory (shared.nvim) as https://github.com/alice/shared.nvim.
Set `name = "..."` on one of them to install both.

Names differing only in case (alice/shared.nvim vs bob/Shared.nvim) are warned about but both kept — they are two directories on ext4, and dropping one there would remove a plugin that installs perfectly well. The warning is what explains the vim.pack error on macOS or Windows.

Collision resolution runs after prune_disabled, so a disabled spec cannot win a directory it was never going to occupy, and walks the registry in import order so the winner does not vary between starts. Drops go through the same worklist as prune_disabled, so a skipped plugin takes its dep-only dependencies with it instead of leaving them installed and orphaned.

Prior art: lazy.nvim keys its plugin registry by derived name, which is what makes the same plugin referenced two ways collapse into one. zpack keys by source, so the fold happens at import instead.

Tests

14 cases in tests/name_collision_test.lua covering folding, spec merging across casings, dependency-graph keying, lazy-parent dependency loading, first-casing-wins, local dirs staying separate, the collision report, case-variants coexisting, name breaking the tie, disabled specs not winning, and orphan cleanup. Full suite 497 passing; luacheck and lua-language-server clean.

Docs: doc/zpack.txt (zpack-gotcha-name-collision, cross-referenced from zpack-Spec.name), docs/tips.md, docs/spec.md.