[chianyungcode]

Closes CHE-21

Why

Every new shell ran atuin, starship, direnv, jw and zoxide just to print their setup scripts. zsh also set up completions twice (once in nix-darwin's /etc/zshrc, once in .zshrc), and it loaded oh-my-zsh plugins that start extra processes before the first prompt.

Result (hyperfine, <shell> -i -c exit):

Shell	Before	After
fish	79 ms	29 ms
zsh	98 ms	34.5 ms

Summary

fish (89f7c41)

• Add __cached_source, which saves each tool's setup script under ~/.cache/fish/init/ and only re-runs the tool when its binary changes.
• Load the direnv hook from the cache, via a conf.d/direnv.fish that replaces Homebrew's copy.
• Make the atuin session ID in fish instead of running atuin uuid.
• Stop loading jw completions at startup; completions/jw.fish already covers them.
• Only load the herdr hook inside a herdr pane.

zsh (6b25d5a)

• The same caching (000-cached-init.zsh) for starship, jw, atuin and zoxide. Starship's PROMPT2 is cached too, and cleared when starship.toml changes.
• Skip nix-darwin's /etc/zshrc (NOSYSZSHRC=1).
• Run compinit after conf.d, holding earlier compdef calls and replaying them. Fix the daily full check, and compile the dump in the background.
• Load the oh-my-zsh brew, git and npm plugins just after the first prompt.
• The same jw and herdr changes as fish.

zsh bun aliases (97fb088)

• The deferred brew plugin now loads after bun.sh, so its ba, bi and bu replaced the bun aliases (ba ran brew autoremove). Rename the bun ones to bna, bni and bnu. Fish keeps ba, bi and bu.

Tradeoffs

• The startup numbers leave out work that now runs just after the prompt. zsh -i -c shells never get the git, brew or npm plugin aliases.
• New completions can take up to a day to appear (rm ~/.cache/zsh/zcompdump-* to refresh).
• The cache only notices binary upgrades. After changing a tool's arguments, a wrapper function or zoxide's _ZO_* variables, run rm -rf ~/.cache/{zsh,fish}/init.
• If many shells start at once right after an upgrade, one may load a half-written script for that launch. A failed starship generation in zsh can stay cached until starship's next upgrade.
• Skipping /etc/zshrc drops HIST_FCNTL_LOCK and any zsh settings added in nix-darwin later.
• The atuin session ID is fully random, where atuin's own ID starts with a timestamp.

Test plan

• Startup times above measured with hyperfine
• Live zsh after the deferred plugins load: bna/bni/bnu run bun, ba/bi/bu run brew
• CI passes
• Open new fish and zsh shells: prompt, atuin (Up/Ctrl-R), zoxide, direnv and completions work

🤖 Generated with Claude Code

[linear-code]

CHE-21