What fstack is
fstack is an MIT-licensed Agent Skills stack for founders who still write the product. Install once; the same / skills run in Cursor, Claude Code, OpenAI Codex, Google Antigravity, and OpenCode. Hermes and OpenClaw pick up project-local skills via npx @scino/fstack init. As of the 2026-09 README it ships 73 skills, 51 of them user-facing.
The F is both Fabio and founder. He built it for how he and his team actually work, then open-sourced it. OneLence is a different product. Same person, different job.
Dual engines
Two engines. One orchestrator (/fstack) that classifies the request instead of dumping every skill into the prompt.
- Founder operations. Inbound leads, support tickets, posts, competitive teardowns. The work between commits.
- Engineering.
/engineer-modeis the default for anything non-trivial in code. It routes to 23 engineering playbooks and 22 design principles./poteto-modeis a compatibility alias.
The bridge skill is /support-loop: a customer paid and the workspace is still locked. The agent finds the webhook, writes a failing test, fixes the handler, checks what else that path touches, and drafts the reply you can actually send. Most stacks stop at "sounds like a billing bug."
| Skill | When to use it |
|---|---|
/fstack | You have a request and want the stack to classify it. |
/founder-mode | Own the whole loop: product, code, copy, customer, speed. |
/engineer-mode | Non-trivial engineering. Playbooks and principles first. |
/support-loop | Ticket, then codebase, then fix, then the reply you can send. |
/lead-reply | Turn a raw inbound into a consultative reply that matches what you actually ship. |
/inbox-triage | Rank a pile of threads by commercial urgency and draft answers. |
That is a flagship slice, not the catalog. The rest lives in the GitHub README.
A morning with fstack
Paste last night's inbox into /inbox-triage. You get deal-blockers, hot leads, questions, noise, and drafts instead of a guilt pile.
An inbound asks about SSO you do not have. /lead-reply is supposed to be consultative and true. If the product cannot do it, the draft says so. /unslop-email exists because the first pass will still try to "circle back."
A customer paid and the workspace is still locked. /support-loop owns the whole loop. If it is a bug, /engineer-mode owns the fix. If it is expected behavior, you still owe them a human explanation.
You shipped three PRs and need something public. /changelog-to-post turns the commit list into a customer changelog and a post you would actually publish. When it is time to build, /engineer-mode refuses to write logic until the data shape is named.
fstack vs gstack vs pstack
There is a small family of named stacks in this corner of the internet. They are not the same product with different logos.
| Dimension | fstack | gstack | pstack |
|---|---|---|---|
| Author / stance | Fabio Parlascino, founder work + engineering | Garry Tan, specialist roster | Lauren Tan, engineering playbooks |
| Default mode | Dual-engine founder ops + /engineer-mode | Claude Code specialist team | Engineering-first plugin |
| Harnesses | Cursor, Claude Code, Codex, Antigravity, OpenCode, Hermes/OpenClaw | Claude-centric | Cursor / Claude plugin as shipped by poteto |
When to choose gstack or pstack instead
- Use gstack if you want Garry's specialist roster inside Claude Code.
- Use pstack if you want Lauren Tan's engineering plugin as she ships it.
- Use fstack if you want one stack that can answer an inbound lead and then go fix the bug the customer just hit.
Engineering playbooks, principles, and a few review/CI skills started as Lauren Tan's pstack. They are MIT. fstack keeps the credit and ships that engine as /engineer-mode.
From fstack to OneLence
If you are here, you probably already hate agent theater and dashboard theater for the same reason. fstack is how Fabio runs the messy company loop in the editor: lead, ticket, post, fix. OneLence is what he and Yichen built when marketing reviews kept turning into the same fight over which source to scale, hold, or kill.
Different tool. Same allergy to pretending the numbers already decided for you.