dotfiles/.claude/tasks/0005-fish-shell-module.md

spec, blocked-by

spec	blocked-by
laptop-mvi	0001-skeleton-and-building-host

What to build

A fish Module, configured natively via home-manager, that makes the shell feel like the current CachyOS setup but is correct for NixOS. Translate the existing cachyos-config.fish and the rest of the fish snapshot under reference/home/.config/fish/: the greeting, the bat-manpager, the done and bang-bang plugins, the helper functions, and the eza/nav aliases. Drop or replace every Arch/pacman-specific part with its NixOS equivalent. Set fish as the default login shell.

Configure the plugins natively through home-manager rather than a fish plugin manager.

Acceptance criteria

• A fish Module (following the Enable convention) is enabled on neogaia and configured natively via home-manager.
• The greeting, bat-manpager, done and bang-bang plugins, helper functions, and eza/nav aliases from the reference config are reproduced.
• All Arch/pacman-specific parts are dropped or replaced with NixOS equivalents.
• fish is the user's default login shell.
• The neogaia toplevel still builds with the fish Module enabled.

Implementation Notes

• Plugins are native, not inlined. done and bang-bang come from pkgs.fishPlugins.* via programs.fish.plugins; home-manager drops them into ~/.config/fish/conf.d/ where fish auto-sources them. The reference config inlined the bang-bang __history_previous_command functions and binds by hand; the plugin supplies those, so they are not re-inlined.
• done tuning uses set -g, not set -U. The reference set __done_min_cmd_duration/__done_notification_urgency_level as universal variables, which persist to the universal-variable file and then ignore config changes. A declarative config must own these each session, so they are set global (set -g) in interactiveShellInit.
• Arch/pacman aliases dropped: grubup, fixpacman, mirror (cachyos-rate-mirrors), apt/apt-get (man pacman), big (expac), gitpkg, rip (expac). Replaced with NixOS equivalents: update → sudo nixos-rebuild switch (was pacman -Syu), cleanup → sudo nix-collect-garbage -d (was pacman -Rns).
• Machine-specific PATH hacks dropped, per spec story 6 ("no impure environment lookup"). The hardcoded BUN_INSTALL, the node-v24... tarball path, and ~/Applications/depot_tools from config.fish are absolute/impure and are not reproduced; such tooling should be Nix-provided when its own Module arrives. The portable bits are kept: ~/.local/bin on PATH (guarded) and sourcing ~/.fish_profile.
• env.fish and rustup.fish deliberately not carried over. ANDROID_HOME/platform-tools (Android SDK) and source ~/.cargo/env.fish (rust) are dev-toolchain integrations outside the MVI's core tooling (fish/tmux/nvim/Claude Code); they belong to future per-toolchain Modules that provide those tools through Nix rather than sourcing an impure env file.
• hw (hwinfo --short) and tb (nc termbin.com 9999) dropped. These are generic rather than pacman-specific, but each needs an extra package (hwinfo, a netcat) that the minimal install does not otherwise pull in; left out of the MVI and easy to add later.
• copy kept verbatim (including the upstream trim-right call) to preserve exact parity with the current shell.
• Verification. The neogaia system toplevel builds (the spec's primary seam). The rendered ~/.config/fish/ was inspected in the build output: aliases, the three helper functions, the fastfetch greeting, the bat manpager, the done tuning vars, and the conf.d/plugin-done.fish + conf.d/plugin-bang-bang.fish plugin files are all present; users.users.alexion.shell resolves to pkgs.fish.

Post-review adjustments

• defaultShell option. Setting fish as the login shell moved behind modules.fish.defaultShell (default false, gated with mkIf); neogaia opts in explicitly. Enabling the Module alone no longer changes the login shell.
• Abbreviation-first. Every non-eza alias is now a shellAbbr (the eza ls family stays an alias), preferAbbrs = true, and generateCompletions = true is pinned rather than left to the upstream default.
• vi command-line editing. interactiveShellInit sets fish_key_bindings fish_vi_key_bindings; the bang-bang plugin re-binds !/$ in insert mode via its own --on-variable fish_key_bindings handler, so the switch keeps them working.
• Trimmed aliases. Navigation capped at four dots (...../...... dropped); psmem, psmem10, dir, vdir, and please removed.
• Interactive init lives in a real fish file. The Module lives at modules/fish/fish.nix; its interactiveShellInit is builtins.readFile ./config.fish, so the interactive init is written as one editable fish file (vi editing, EDITOR/VISUAL, the bat manpager, the done plugin tuning, and ~/.local/bin/~/.fish_profile) that home-manager renders into ~/.config/fish/config.fish. The file is small enough that splitting it into fragments was not worth the indirection; Nix inlines it at build time, so nothing of ours is autoloaded from a separate runtime file.
• copy stays a function file. functions/copy.fish holds the non-trivial copy body, read into the functions option; fish autoloads function files lazily, so that is the idiomatic home for a function. Trivial one-liner functions stay inline in fish.nix.
• The Auto-loader only collects .nix, so every .fish file under modules/fish/ is inert to it.