fstack

engineer-mode

fstack engineering execution. 23 playbooks, 24 principles, verified work, no slop. Use for /engineer-mode, /poteto-mode, or any non-trivial engineering task.

figure-it-out

Design an auditable playbook when no narrower one fits: a large migration, an ambitious multi-part change, or work a human reviews after stepping away. Scales rigor to the task, runs a hypothesis loop, and logs decisions via show-me-your-work. Use for /figure-it-out, 'figure it out', a large migration, or when no narrower playbook applies.

fix-ci

Find failing PR checks, inspect logs or external check links, and apply focused fixes

fix-merge-conflicts

Resolve merge conflicts non-interactively, validate build and tests, and finalize conflict resolution

founder-mode

High-agency founder execution mode. Takes end-to-end ownership across product, code, copy, customers, and speed-to-market. Cuts bureaucracy, refuses generic AI hedges, enforces obsessive taste, and prioritizes commercial impact. Use for /founder-mode, "founder mode", or cross-functional shipping.

founder-voice

Manages and maintains the founder's persistent voice profile, tone preferences, vocabulary rules, and platform styles across X and LinkedIn. Use for /founder-voice, "configure my voice", or establishing writing persona.

fstack

Master orchestrator for fstack. Routes founder operations (sales, support, social, strategy) and engineering work through /engineer-mode. Use for /fstack, /fabio-mode, or founder/engineering requests.

geo-page

Generates high-authority GEO (Generative Engine Optimization) and documentation pages designed to be accurately cited by AI search engines (Perplexity, SearchGPT, ChatGPT, Gemini) without keyword-stuffed SEO slop. Use for /geo-page, "create comparison page", or SEO content.

get-pr-comments

Fetch and summarize review comments from the active pull request

how

Use for "how does X work", code walkthroughs before changing something, and placement / ownership / layering questions ("where should this live", "which package owns this", "is this the right layer"). Explains subsystem architecture, runtime flow, onboarding mental models. Can critique architecture. Use why for motivation.

inbox-triage

Ingests pasted email threads or inbox batches, ranks by business and customer urgency, surfaces top priorities, and generates concise notes and 1-click draft responses. Use for /inbox-triage, "triage inbox", or sorting customer/sales messages.

interrogate

Use for "interrogate", "adversarial review", "multi-model review", "challenge this", "stress test this code", "find blind spots", or "tear this apart". Multiple LLM reviewers challenge changes from independent angles.

lead-reply

Draft high-conversion, charming, consultative, and non-salesy replies to inbound leads and inquiries. Considers real product capabilities, persona, and next steps without AI slop. Use for /lead-reply, "draft reply to lead", or sales inquiries.

maintain-verification-skill

Periodic pass that keeps a project's verification skill and feature map honest: parallel source readers per feature, one live session driving every feature, at most one PR of proven corrections. Use for /maintain-verification-skill or "audit the verify skill".

make-pr-easy-to-review

Prepare PRs for review by cleaning noisy history, improving PR descriptions, and adding reviewer guidance without changing code behavior. Use for "make this easy to review", "tidy this PR", "clean up commits", or "annotate the diff".

no-comments

Spawn the comment-sicko subagent, fix accepted findings, and offer encodings for claimed constraints.

office-hours

YC-style founder sparring and product interrogation. Asks 6 forcing questions on demand reality, status quo, desperate specificity, narrowest wedge, observation, and future-fit before writing code. Use for /office-hours, "brainstorm this idea", or product stress-test.

poteto-mode

Compatibility alias for /engineer-mode and credit to Lauren Tan's pstack, which set the foundation of playbooks and principles for fstack's engineer-mode. Use for /poteto-mode or legacy prompts.

principle-attack-the-premise

Apply when two or more fixes that share one premise have failed the same gate. Take a census of which actors hold the imbalance before the next fix, then question the premise instead of writing another fix that assumes it.

principle-boundary-discipline

Apply when wiring validation, error handling, or framework adapters. Concentrate guards at system boundaries (CLI, config, network, external APIs); trust internal types and keep business logic in pure functions.

principle-build-the-lever

Apply to any non-trivial work, not just bulk work: edits, migrations, analyses, checks. Build the tool that does it or proves it (codemod, script, generator, or a skill your subagents follow) instead of working by hand. The tool is the artifact a reviewer can rerun.

principle-clear-naming

Apply when naming variables, functions, types, files, or endpoints. Enforces the 6-month amnesia test, language conventions, intent-based naming, and cross-boundary consistency.

principle-encode-lessons-in-structure

Apply when you catch yourself writing the same instruction a second time, or notice a recurring correction. Encode the rule as a lint, metadata flag, runtime check, or script instead of more text.

principle-exhaust-the-design-space

Apply when facing a novel UI interaction or architectural decision with no precedent in the codebase. Build 2-3 competing prototypes and compare side by side before committing.

principle-experience-first

Apply when product, UX, or feature-scope tradeoffs come up. Choose user delight over implementation convenience; ship fewer polished features over more rough ones.

principle-fix-root-causes

Apply when debugging. Trace each symptom to its root cause and fix it there; reproduce first, ask why until you reach it, resist nil-check guards that silence crashes.

principle-foundational-thinking

Apply before writing logic: choosing core types and data structures, sequencing scaffold-vs-feature work, asking what concurrent actors share. Get the data structures right so downstream code becomes obvious.

principle-guard-the-context-window

Apply when context is filling up: large outputs, long files, repeated reads, fan-out planning. Route bulk to subagents; keep summaries in the main thread, not raw payloads.

principle-laziness-protocol

Apply when refactoring, evaluating diff size, or tempted to add abstractions, layers, or signal threading. Enforces Occam's Razor: bias toward deletion and the simplest change that solves the problem.

principle-make-operations-idempotent

Apply when designing commands, lifecycle steps, or processing loops that run amid crashes, restarts, and retries. Converge to the same end state regardless of partial prior runs.

principle-migrate-callers-then-delete-legacy-apis

Apply when introducing a new internal API while old callers still exist. Migrate callers and delete the old API in the same wave instead of preserving compatibility layers.

principle-minimize-reader-load

Apply when reviewing or shaping code that's hard to trace. Count layers between question and answer, and hidden state in the reader's head; collapse one-caller wrappers and shrink mutable scope.

principle-model-the-domain

Apply when writing stateful logic, or when code branches a lot or repeats a shape assumption across files. Encode the domain in a structure instead of scattered conditionals.

principle-never-block-on-the-human

Apply when tempted to ask 'should I do X?' on reversible work. Proceed, present the result, let the human course-correct after the fact; reserve confirmation for irreversible actions.

principle-outcome-oriented-execution

Apply during planned rewrites and migrations with explicit phase boundaries. Converge on the target architecture; don't preserve smooth intermediate states with throwaway compatibility code.

principle-prove-it-works

Apply after completing a task, before declaring done. Verify against the real artifact (run the feature, read the actual value, inspect the diff), not a proxy, self-report, or 'it compiles.'

principle-redesign-from-first-principles

Apply when integrating a new requirement into an existing design. Redesign as if the requirement had been a foundational assumption from day one, instead of bolting it on.

principle-separate-before-serializing-shared-state

Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first; serialize structurally only when one shared writer is a real invariant.

principle-sequence-verifiable-units

Apply to multi-step work (sweeps, migrations, runs of similar edits) and to how you stack commits and PRs. Break work into small units that each end in a verifiable state, check each before the next, and order delivery so the sequence proves itself to a reviewer.

principle-subtract-before-you-add

Apply when sequencing an addition, refactor, or rewrite. Remove dead weight, redundant validators, and stub references first, then build on the simpler base.

principle-test-behavior-not-implementation

Apply when you write, change, or keep a test. Call the code the way its users do and assert the result they observe against a literal expected value. If the test would still pass when every imported function returns undefined, rewrite the assertion or delete the test.

principle-type-system-discipline

Apply when designing types, reviewing a function signature, or writing code in any statically-typed language. Make illegal states unrepresentable, brand semantic primitives, parse external data at boundaries, refuse to lie to the compiler, exhaust variants, derive from authoritative schemas.

recall

Reconstruct your recent working context from your own chat history, live state, and the shared record (user reports, prior fixes, incidents), then hand back a tight current-state brief. Use for 'recall my work on X', 'catch me up', 'what have I been working on', 'where did I leave off', before starting or resuming work.

reflect

Spawn three parallel review subagents over the active transcript, surface learnings, and route each to a concrete edit on an existing skill. Use when the user says reflect.

retro

Weekly founder momentum, engineering velocity, customer feedback, and tech debt review. Keeps founders honest about real progress vs busywork. Use for /retro, "weekly review", or team retrospective.

setup-fstack

Configure which models fstack uses per role and at what reasoning budget. Detects available models and writes a per-harness override sheet. Use for /setup-fstack, "configure fstack models", "fstack budget", or changing model choices.

show-me-your-work

Keep a reviewable decision trail for long-running or unattended work: a TSV log with one row per decision (what, why, evidence, result). Local by default; commit it when a reviewer needs the trail to trust the result. Use for /show-me-your-work, autonomous or multi-phase runs, or work a human reviews after stepping away.

social-post

Drafts authentic, high-signal social media posts from founder thoughts, engineering wins, or product updates. Generates tailored, distinct styles for X (punchy, witty, no fluff) and LinkedIn (tactical, story-driven, structured). Use for /social-post, "draft tweet", "draft linkedin post", or founder content.

social-reply

Crafts high-leverage, non-slop replies to trending and viral posts on X and LinkedIn. The

stfu

Forces ultra-terse, zero-chatter, quiet execution mode. Cuts all conversational filler, preambles, narrations, polite throat-clearing, and verbose diff explanations. Executes actions directly and reports minimal necessary status. Use for /stfu, /shutup, "shut up", or "quiet mode".

sudo

Root operator execution override. Disables unsolicited moralizing, paternalistic refusals, sycophantic pushback, and false-positive safety friction for authorized technical systems, security auditing, and scientific research. Use for /sudo, "sudo", or root override mode.

support-loop

End-to-end founder customer support loop. Ingests a customer bug report or inquiry, investigates the codebase, reproduces the issue, triggers engineer-mode bug-fix if valid, or prepares a workaround, and drafts an empathetic, contextual customer reply. Use for /support-loop, "handle support ticket", or customer bug triage.

swarm

Fan out N parallel workers, drain them, and return one report. Use for /swarm, 'swarm this', or parallel coverage, races, gauntlets, and exploration.

tdd

Use only when the user explicitly asks for TDD, a failing test, or a regression test, OR when the bug has an obvious cheap local test target. Skip when the test path is unclear, expensive, integration-heavy, or not requested.

teach

Explain a body of work plainly so a person actually understands it. Runs the `how` and `why` skills and weaves what they find into one clear explanation. Use for 'teach me this', 'help me really understand X', 'explain this change or subsystem to me'.

teardown

Conducts deep competitor, product, and pricing teardowns using web browsing and market intelligence. Analyzes positioning, pricing packaging, customer friction, sentiment on Reddit/X, and architectural vulnerabilities. Use for /teardown, "analyze competitor", or competitor teardown.

technical-writing

Layered technical-writing standard: Diátaxis structure, Google developer style sentences, STE instruction rules, Global English syntax. Use for /technical-writing or when writing or reviewing docs, RFCs, readmes, PR descriptions, or commit messages.

thermo-nuclear-code-quality-review

Run an extremely strict maintainability review for abstraction quality, giant files, and spaghetti-condition growth. Use for a thermo-nuclear code quality review, thermonuclear review, deep code quality audit, or especially harsh maintainability review.

typescript-best-practices

TypeScript best practices. Use when reading or editing any .ts or .tsx file.

unslop

Cut AI tells from any writing. Must always apply.

unslop-email

De-slop and humanize email drafts. Strips AI clichés, corporate buzzwords, robotic pleasantries, and forced enthusiasm. Injects authentic founder warmth, brevity, and conversational charm. Use for /unslop-email, "humanize this email", or cleaning up messages.

what-did-i-get-done

Summarize authored commits over a user-specified time period into a concise update

why

Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed thresholds. Discovers available MCPs and queries each evidence category (source control, issue tracker, long-form docs, real-time chat, infrastructure observability, error tracking, product analytics warehouse) in parallel, then returns a cited read on decisions and tradeoffs. Use how for runtime behavior.