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Fish shell Agent Skill

Fish 4.9.x on this machine — the login shell: house style, language, builtins, config layout, startup cost, and verified caveats.

Install this skill Read the source first Free Written by hogdanish
Context cost
123k tokensestimated from the bundle, loaded when it triggers
Bundle
15 of 16 fileshanded out here; the rest is at its source
Licence
not declarednone named by its author
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Fish 4.9.x on this machine — the login shell: house style, language, builtins, config layout, startup cost, and verified caveats. Load before any .fish work.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

developer tools
Filed under

Developer Tools & Repos

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md13.7 kB · preview
--- name: fish ---
6# Fish shell
7
8fish **4.9.x** (/opt/homebrew/bin/fish) is the **login** shell on this machine and the default for any script a human runs. This skill covers **all** fish work in **any** directory — a script in a project, a one-off function, a port from bash, a debugging session — not only ~/.config/fish.
9
10⚠ fish became the login shell on **2026-09-12** (chsh), replacing /bin/zsh. Nothing pins it per tool any more — Ghostty, Herdr and VS Code resolve it from $SHELL then the passwd entry. ⚠ chsh does **not** update $SHELL, and a GUI session that predates it keeps the old value, so conf.d/_init.fish exports $SHELL from the running fish — without that line those same tools open **zsh** while dscl reports fish (caveats.md). /bin/zsh is still installed and still deliberately unconfigured, but it is no longer inert: Claude Code and Codex both force /bin/zsh for their own tool shells regardless of $SHELL, so ~/.zshenv, ~/.zshrc and ~/.zprofile must stay exactly where they are.
11
12**Do not ration your reading.** [style-guide.md](references/style-guide.md) is mandatory for every .fish file. Then read **every file in the Required-reading row matching your task** — the rows are floors, not menus. Each reference is 287–613 lines and the count is listed, so the cost is never a guess: reading four of them is cheaper than one set -gx that silently rewrites fish_variables. When two rows apply, read both. Skipping a listed file to save tokens is the most common way fish work goes wrong.
13
14⚠ **Bash tool calls run under zsh.** Fish functions and abbreviations do not exist for you. Call fish explicitly: /opt/homebrew/bin/fish -c '...'. Add --no-config when this machine's config must not mask the result — ⚠ but --no-config also leaves $fish_function_path unset and demotes set -U to global, so it cannot test autoloading or universals.
15
16## The style guide is law
17
18Five load-bearing rules. [style-guide.md](references/style-guide.md) has the reasoning, the naming and scope discipline, and annotated templates for a conf.d snippet, a function, a namespaced helper, a completion and a standalone script.
19
201. set -l by default; -gx only for real environment variables; **never set -U** in a file.
212. --on-event / --on-variable / --on-signal handlers register only when a file is *sourced* → they belong in conf.d/, never functions/.
223. Guard everything external: type -q <cmd> before a tool, test -r <file> before an optional file.
234. string and path builtins instead of sed/grep/cut/basename — a startup fork is the only fish performance mistake that matters.
245. fish_indent decides all formatting. 4 spaces. No alias. --description on every function.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md1,883 words
Files15
Licencenot declared
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈50
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
122,925
on trigger
The instruction body and 14 supporting files, read only when the skill fires.
61.5%
of a 200k window
Ten skills this size would not fit in the window together.
050k100k150k200k context window

123k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

The download carries 15 of the 16 files in its source folder; the list here names 15 files, 491.9 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in. The other one is not in the download — listed after these, with why.

  • SKILL.md13.7 kB
  • agents/openai.yaml0.2 kB
  • references/bash-to-fish.md35.8 kB
  • references/builtins.md54.2 kB
  • references/caveats.md39.9 kB
  • references/completions.md17.9 kB
  • references/config-layout.md76.9 kB
  • references/fishconf-patterns.md47.2 kB
  • references/fisher.md22.3 kB
  • references/interactive.md31.8 kB
  • references/language.md29.7 kB
  • references/prompt-and-colours.md33.7 kB
  • references/style-guide.md17.4 kB
  • references/text-processing.md29.3 kB
  • references/variables.md41.9 kB

Not in the download

Not carried is a type a skill download does not hold. Marked read: its SKILL.md or scripts name the file, so without it the skill works only in part. Take it from its source.

  • scripts/gen-fish-theme.fishread · not carried
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the download is 15 files — not the whole of its source: 1 file is left out, and the skill reads it. It is listed under the files, with why.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Fish shell · 123k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/fish-shell/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/fish-shell" ] && { [ ! -e .claude/skills/fish-shell ] || { mv .claude/skills/fish-shell "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/fish-shell" .claude/skills/ && echo "Installed .claude/skills/fish-shell"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add hogdanish/fish-shell

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/fish-shell/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/fish-shell/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/fish-shell" ] && { [ ! -e ~/.claude/skills/fish-shell ] || { mv ~/.claude/skills/fish-shell "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/fish-shell" ~/.claude/skills/ && echo "Installed ~/.claude/skills/fish-shell" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/fish-shell/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as fish in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, fish-shell. Not in this download: 1 file of its source, which its SKILL.md or scripts read (which one, and why). Take it from its source.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referencehogdanish/fish-shell

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

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Who wrote it

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hogdanish

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