fstack, the simple stack

I built my own agent skill collection. It’s called fstack. The f stands for Flavio.

You can install it right now:

npx skills@latest add flaviocopes/fstack

It works with Cursor, Claude Code, Codex, and anything else that reads skills.

Why another stack

There are a lot of skill collections around. I studied several of them, and I borrowed ideas from all of them.

But they kept growing. 30+ skills, personas, pipelines, voice triggers. I couldn’t hold them in my head, so I stopped using them.

The complexity also showed up in the code. A process full of phases, personas, and ceremony produced layers, abstractions, and options nobody asked for.

fstack is my response to that. Agent skills that ask: can this be less?

The core loop

fstack is 13 skills. Plain names, one job each.

Five of them form the core loop:

fstack-nail (when unclear) → fstack-plan → fstack-build → fstack-check → fstack-push

• /fstack-nail asks up to 5 questions and turns an unclear task into a 3-line summary you approve
• /fstack-plan writes a one-page plan with a mandatory “what we’re NOT doing” section
• /fstack-build implements the plan one small step at a time, asking at real choices
• /fstack-check asks three questions: does it work, does it match the plan, is it simple
• /fstack-push commits the current task’s changes and pushes them. Nothing else.

The nail step is only for unclear tasks. If the task is already clear, I start with the plan.

Notice the loop ends with a push. I commit the current task’s changes and push to the branch I’m on. That’s it. fstack reflects how I actually work.

Before you write code

Two skills run before any code exists.

/fstack-roast stress-tests a product idea. It asks you multiple-choice questions about demand, competition, and distribution, then gives you a verdict and the smallest version worth building. Honest pushback before you waste a weekend.

/fstack-interview asks about the business behind the project, including who the customer is, how they find you, and what they pay. It records the answers in AGENTS.md, so every agent session has that context.

The skill I care most about

/fstack-simplify exists only to remove things.

Point it at a file, or at the whole codebase. It finds unnecessary abstractions, dead configuration, wrappers around wrappers, and proposes deletions. Only deletions. It never adds.

I don’t know another stack with a skill whose entire job is removing code. To me it’s the most important one.

The rest

A few more you sprinkle in when needed:

• /fstack-design pulls AI-generated UI back to your existing styles
• /fstack-document writes layered docs for the project, from ELI5 to deep. Run it again to update them
• /fstack-learn captures one lesson in three lines, so future sessions start smarter
• /fstack-counselors sends the same question to the 3 most capable models available and synthesizes one verdict, including where they disagree

And if you don’t know where to start, type /fstack alone. It lists every skill. Give it a task, and it picks one skill to run.

The human drives

fstack stops at real decision points and asks. You invoke each step. Nothing continues automatically.

No long autonomous runs. No agent disappearing for an hour and coming back with 4,000 changed lines. Small steps, small diffs, your judgment in the loop.

That’s the whole philosophy. The skills have plain names, avoid jargon, and prefer deletion. Every skill fits in about 150 lines. If it doesn’t, it’s doing too much.

Try it

npx skills@latest add flaviocopes/fstack

The code is on GitHub, MIT licensed.

I wrote a full guide with examples for every skill at aiworkshop.sh/fstack.

fstack distills ideas from gstack, pstack, Compound Engineering, Matt Pocock’s skills, and Aaron Francis’s counselors. Credits and links are in the guide. They’re all generous, thoughtful work.

Want me to talk about your product? You can sponsor this site.