Taffybar NixOS Flake Chain

How the taffybar ecosystem packages are consumed by the NixOS configuration through a chain of nested flakes, and what flake.lock updates may be needed when something changes.

See also: taffybar-ecosystem-release for the package dependency graph, release workflow, and Hackage publishing.

The Three-Layer Flake Chain

The NixOS system build pulls in taffybar through three nested flake.nix files:

nixos/flake.nix                              (top — `just switch` reads this)
│ ├── taffybar         path:.../taffybar/taffybar
│ ├── imalison-taffybar  path:../dotfiles/config/taffybar
│ └── gtk-sni-tray, gtk-strut, etc.          (GitHub inputs)
│
dotfiles/config/taffybar/flake.nix           (middle — imalison-taffybar config)
│ ├── taffybar         path:.../taffybar/taffybar
│ └── gtk-sni-tray, gtk-strut, etc.          (GitHub inputs)
│
dotfiles/config/taffybar/taffybar/flake.nix  (bottom — taffybar library)
│ └── gtk-sni-tray, gtk-strut, etc.          (flake = false GitHub inputs)

All three flakes declare their own top-level inputs for the ecosystem packages and use follows to keep versions consistent within each layer.

Why Bottom-Up Updates Matter

path: inputs snapshot the target flake including its flake.lock at lock time. If you only run nix flake update at the top (nixos) layer, the middle and bottom layers keep whatever was previously locked in their own flake.lock files.

So when propagating a change to a system rebuild, you generally need to update flake.lock files from the bottom up — the bottom layer first so the middle layer picks up fresh locks when it re-resolves, then the middle so the top picks up fresh locks.

# Bottom (if an ecosystem dep changed):
cd ~/.config/taffybar/taffybar && nix flake update <pkg>

# Middle:
cd ~/.config/taffybar && nix flake update <pkg> taffybar

# Top:
cd ~/dotfiles/nixos && nix flake update <pkg> imalison-taffybar taffybar

Not every change requires touching all three layers. Think about which flake.lock files actually contain stale references:

• Changed taffybar itself — it's the bottom layer, so start at the middle (nix flake update taffybar) then the top.
• Changed a leaf ecosystem package (e.g. gtk-strut) — start at the bottom since taffybar's flake.lock references it, then cascade up.
• The nixos flake also has direct GitHub inputs for ecosystem packages with follows overrides. Updating those at the top level may be sufficient if nothing changed in the middle/bottom flake.lock files themselves.

Rebuilding

cd ~/dotfiles/nixos && just switch

If taffybar seems stale after a rebuild, check whether the flake.lock at each layer actually points at the expected revision — a missed cascade step is the usual cause.