gstack

"I don't think I've typed like a line of code probably since December, basically, which is an extremely large change." — Andrej Karpathy, No Priors podcast, March 2026

When I heard Karpathy say this, I wanted to find out how. How does one person ship like a team of twenty? Peter Steinberger built OpenClaw — 247K GitHub stars — essentially solo with AI agents. The revolution is here. A single builder with the right tooling can move faster than a traditional team.

I'm Garry Tan, President & CEO of Y Combinator. I've worked with thousands of startups — Coinbase, Instacart, Rippling — when they were one or two people in a garage. Before YC, I was one of the first eng/PM/designers at Palantir, cofounded Posterous (sold to Twitter), and built Bookface, YC's internal social network.

gstack is my answer. I've been building products for twenty years, and right now I'm shipping more code than I ever have. In the last 60 days: 600,000+ lines of production code (35% tests), 10,000-20,000 lines per day, part-time, while running YC full-time. Here's my last /retro across 3 projects: 140,751 lines added, 362 commits, ~115k net LOC in one week.

2026 — 1,237 contributions and counting:

2013 — when I built Bookface at YC (772 contributions):

Same person. Different era. The difference is the tooling.

gstack is how I do it. It turns Claude Code into a virtual engineering team — a CEO who rethinks the product, an eng manager who locks architecture, a designer who catches AI slop, a reviewer who finds production bugs, a QA lead who opens a real browser, a security officer who runs OWASP + STRIDE audits, and a release engineer who ships the PR. Twenty-three specialists and eight power tools, all slash commands, all Markdown, all free, MIT license.

This is my open source software factory. I use it every day. I'm sharing it because these tools should be available to everyone.

Fork it. Improve it. Make it yours. And if you want to hate on free open source software — you're welcome to, but I'd rather you just try it first.

Who this is for:

• Founders and CEOs — especially technical ones who still want to ship
• First-time Claude Code users — structured roles instead of a blank prompt
• Tech leads and staff engineers — rigorous review, QA, and release automation on every PR

Quick start

1. Install gstack (30 seconds — see below)
2. Run /office-hours — describe what you're building
3. Run /plan-ceo-review on any feature idea
4. Run /review on any branch with changes
5. Run /qa on your staging URL
6. Stop there. You'll know if this is for you.

Install — 30 seconds

Requirements: Claude Code, Git, Bun v1.0+, Node.js (Windows only)

Step 1: Install on your machine

Open Claude Code and paste this. Claude does the rest.

Install gstack: run git clone --single-branch --depth 1 https://github.com/garrytan/gstack.git ~/.claude/skills/gstack && cd ~/.claude/skills/gstack && ./setup then add a "gstack" section to CLAUDE.md that says to use the /browse skill from gstack for all web browsing, never use mcp__claude-in-chrome__* tools, and lists the available skills: /office-hours, /plan-ceo-review, /plan-eng-review, /plan-design-review, /design-consultation, /design-shotgun, /design-html, /review, /ship, /land-and-deploy, /canary, /benchmark, /browse, /connect-chrome, /qa, /qa-only, /design-review, /setup-browser-cookies, /setup-deploy, /retro, /investigate, /document-release, /codex, /cso, /autoplan, /plan-devex-review, /devex-review, /careful, /freeze, /guard, /unfreeze, /gstack-upgrade, /learn. Then ask the user if they also want to add gstack to the current project so teammates get it.

Step 2: Add to your repo so teammates get it (optional)

Add gstack to this project: run cp -Rf ~/.claude/skills/gstack .claude/skills/gstack && rm -rf .claude/skills/gstack/.git && cd .claude/skills/gstack && ./setup then add a "gstack" section to this project's CLAUDE.md that says to use the /browse skill from gstack for all web browsing, never use mcp__claude-in-chrome__* tools, lists the available skills: /office-hours, /plan-ceo-review, /plan-eng-review, /plan-design-review, /design-consultation, /design-shotgun, /design-html, /review, /ship, /land-and-deploy, /canary, /benchmark, /browse, /connect-chrome, /qa, /qa-only, /design-review, /setup-browser-cookies, /setup-deploy, /retro, /investigate, /document-release, /codex, /cso, /autoplan, /plan-devex-review, /devex-review, /careful, /freeze, /guard, /unfreeze, /gstack-upgrade, /learn, and tells Claude that if gstack skills aren't working, run cd .claude/skills/gstack && ./setup to build the binary and register skills.

Real files get committed to your repo (not a submodule), so git clone just works. Everything lives inside .claude/. Nothing touches your PATH or runs in the background.

Contributing or need full history? The commands above use --depth 1 for a fast install. If you plan to contribute or need full git history, do a full clone instead:

git clone https://github.com/garrytan/gstack.git ~/.claude/skills/gstack

Codex, Gemini CLI, or Cursor

gstack works on any agent that supports the SKILL.md standard. Skills live in .agents/skills/ and are discovered automatically.

Install to one repo:

git clone --single-branch --depth 1 https://github.com/garrytan/gstack.git .agents/skills/gstack
cd .agents/skills/gstack && ./setup --host codex

When setup runs from .agents/skills/gstack, it installs the generated Codex skills next to it in the same repo and does not write to ~/.codex/skills.

Install once for your user account:

git clone --single-branch --depth 1 https://github.com/garrytan/gstack.git ~/gstack
cd ~/gstack && ./setup --host codex

setup --host codex creates the runtime root at ~/.codex/skills/gstack and links the generated Codex skills at the top level. This avoids duplicate skill discovery from the source repo checkout.

Or let setup auto-detect which agents you have installed:

git clone --single-branch --depth 1 https://github.com/garrytan/gstack.git ~/gstack
cd ~/gstack && ./setup --host auto

For Codex-compatible hosts, setup now supports both repo-local installs from .agents/skills/gstack and user-global installs from ~/.codex/skills/gstack. All 31 skills work across all supported agents. Hook-based safety skills (careful, freeze, guard) use inline safety advisory prose on non-Claude hosts.

Factory Droid

gstack works with Factory Droid. Skills install to .factory/skills/ and are discovered automatically. Sensitive skills (ship, land-and-deploy, guard) use disable-model-invocation: true so Droids don't auto-invoke them.

git clone --single-branch --depth 1 https://github.com/garrytan/gstack.git ~/gstack
cd ~/gstack && ./setup --host factory

Skills install to ~/.factory/skills/gstack-*/. Restart droid to rescan skills, then type /qa to get started.

Voice input (AquaVoice, Whisper, etc.)

gstack skills have voice-friendly trigger phrases. Say what you want naturally — "run a security check", "test the website", "do an engineering review" — and the right skill activates. You don't need to remember slash command names or acronyms.

See it work

You:    I want to build a daily briefing app for my calendar.
You:    /office-hours
Claude: [asks about the pain — specific examples, not hypotheticals]

You:    Multiple Google calendars, events with stale info, wrong locations.
        Prep takes forever and the results aren't good enough...

Claude: I'm going to push back on the framing. You said "daily briefing
        app." But what you actually described is a personal chief of
        staff AI.
        [extracts 5 capabilities you didn't realize you were describing]
        [challenges 4 premises — you agree, disagree, or adjust]
        [generates 3 implementation approaches with effort estimates]
        RECOMMENDATION: Ship the narrowest wedge tomorrow, learn from
        real usage. The full vision is a 3-month project — start with
        the daily briefing that actually works.
        [writes design doc → feeds into downstream skills automatically]

You:    /plan-ceo-review
        [reads the design doc, challenges scope, runs 10-section review]

You:    /plan-eng-review
        [ASCII diagrams for data flow, state machines, error paths]
        [test matrix, failure modes, security concerns]

You:    Approve plan. Exit plan mode.
        [writes 2,400 lines across 11 files. ~8 minutes.]

You:    /review
        [AUTO-FIXED] 2 issues. [ASK] Race condition → you approve fix.

You:    /qa https://staging.myapp.com
        [opens real browser, clicks through flows, finds and fixes a bug]

You:    /ship
        Tests: 42 → 51 (+9 new). PR: github.com/you/app/pull/42

You said "daily briefing app." The agent said "you're building a chief of staff AI" — because it listened to your pain, not your feature request. Eight commands, end to end. That is not a copilot. That is a team.

The sprint

gstack is a process, not a collection of tools. The skills run in the order a sprint runs:

Think → Plan → Build → Review → Test → Ship → Reflect

Each skill feeds into the next. /office-hours writes a design doc that /plan-ceo-review reads. /plan-eng-review writes a test plan that /qa picks up. /review catches bugs that /ship verifies are fixed. Nothing falls through the cracks because every step knows what came before it.

Skill	Your specialist	What they do
/office-hours	YC Office Hours	Start here. Six forcing questions that reframe your product before you write code. Pushes back on your framing, challenges premises, generates implementation alternatives. Design doc feeds into every downstream skill.
/plan-ceo-review	CEO / Founder	Rethink the problem. Find the 10-star product hiding inside the request. Four modes: Expansion, Selective Expansion, Hold Scope, Reduction.
/plan-eng-review	Eng Manager	Lock in architecture, data flow, diagrams, edge cases, and tests. Forces hidden assumptions into the open.
/plan-design-review	Senior Designer	Rates each design dimension 0-10, explains what a 10 looks like, then edits the plan to get there. AI Slop detection. Interactive — one AskUserQuestion per design choice.
/plan-devex-review	Developer Experience Lead	Evaluates plans through Addy Osmani's DX framework: zero friction, learn by doing, fight uncertainty. Rates 8 DX dimensions 0-10 with a DX Scorecard. Use for developer-facing products — APIs, CLIs, SDKs, libraries, platforms, docs.
/design-consultation	Design Partner	Build a complete design system from scratch. Researches the landscape, proposes creative risks, generates realistic product mockups.
/review	Staff Engineer	Find the bugs that pass CI but blow up in production. Auto-fixes the obvious ones. Flags completeness gaps.
/investigate	Debugger	Systematic root-cause debugging. Iron Law: no fixes without investigation. Traces data flow, tests hypotheses, stops after 3 failed fixes.
/design-review	Designer Who Codes	Same audit as /plan-design-review, then fixes what it finds. Atomic commits, before/after screenshots.
/devex-review	DX Tester	Live developer experience audit. Actually tests your onboarding: navigates docs, tries the getting started flow, times TTHW, screenshots errors. Compares against /plan-devex-review scores — the boomerang that shows if your plan matched reality.
/design-shotgun	Design Explorer	Generate multiple AI design variants, open a comparison board in your browser, and iterate until you approve a direction. Taste memory biases toward your preferences.
/design-html	Design Engineer	Generates production-quality HTML with Pretext for computed text layout. Works with approved mockups, CEO plans, design reviews, or from scratch. Text reflows on resize, heights adjust to content. Smart API routing picks the right Pretext patterns per design type. Framework detection for React/Svelte/Vue.
/qa	QA Lead	Test your app, find bugs, fix them with atomic commits, re-verify. Auto-generates regression tests for every fix.
/qa-only	QA Reporter	Same methodology as /qa but report only. Pure bug report without code changes.
/cso	Chief Security Officer	OWASP Top 10 + STRIDE threat model. Zero-noise: 17 false positive exclusions, 8/10+ confidence gate, independent finding verification. Each finding includes a concrete exploit scenario.
/ship	Release Engineer	Sync main, run tests, audit coverage, push, open PR. Bootstraps test frameworks if you don't have one.
/land-and-deploy	Release Engineer	Merge the PR, wait for CI and deploy, verify production health. One command from "approved" to "verified in production."
/canary	SRE	Post-deploy monitoring loop. Watches for console errors, performance regressions, and page failures.
/benchmark	Performance Engineer	Baseline page load times, Core Web Vitals, and resource sizes. Compare before/after on every PR.
/document-release	Technical Writer	Update all project docs to match what you just shipped. Catches stale READMEs automatically.
/retro	Eng Manager	Team-aware weekly retro. Per-person breakdowns, shipping streaks, test health trends, growth opportunities. /retro global runs across all your projects and AI tools (Claude Code, Codex, Gemini).
/browse	QA Engineer	Give the agent eyes. Real Chromium browser, real clicks, real screenshots. ~100ms per command. /open-gstack-browser launches GStack Browser with sidebar, anti-bot stealth, and auto model routing.
/setup-browser-cookies	Session Manager	Import cookies from your real browser (Chrome, Arc, Brave, Edge) into the headless session. Test authenticated pages.
/autoplan	Review Pipeline	One command, fully reviewed plan. Runs CEO → design → eng review automatically with encoded decision principles. Surfaces only taste decisions for your approval.
/learn	Memory	Manage what gstack learned across sessions. Review, search, prune, and export project-specific patterns, pitfalls, and preferences. Learnings compound across sessions so gstack gets smarter on your codebase over time.

Which review should I use?

Building for...	Plan stage (before code)	Live audit (after shipping)
End users (UI, web app, mobile)	/plan-design-review	/design-review
Developers (API, CLI, SDK, docs)	/plan-devex-review	/devex-review
Architecture (data flow, perf, tests)	/plan-eng-review	/review
All of the above	/autoplan (runs CEO → design → eng → DX, auto-detects which apply)	—

Power tools

Skill	What it does
/codex	Second Opinion — independent code review from OpenAI Codex CLI. Three modes: review (pass/fail gate), adversarial challenge, and open consultation. Cross-model analysis when both /review and /codex have run.
/careful	Safety Guardrails — warns before destructive commands (rm -rf, DROP TABLE, force-push). Say "be careful" to activate. Override any warning.
/freeze	Edit Lock — restrict file edits to one directory. Prevents accidental changes outside scope while debugging.
/guard	Full Safety — /careful + /freeze in one command. Maximum safety for prod work.
/unfreeze	Unlock — remove the /freeze boundary.
/open-gstack-browser	GStack Browser — launch GStack Browser with sidebar, anti-bot stealth, auto model routing (Sonnet for actions, Opus for analysis), one-click cookie import, and Claude Code integration. Clean up pages, take smart screenshots, edit CSS, and pass info back to your terminal.
/setup-deploy	Deploy Configurator — one-time setup for /land-and-deploy. Detects your platform, production URL, and deploy commands.
/gstack-upgrade	Self-Updater — upgrade gstack to latest. Detects global vs vendored install, syncs both, shows what changed.

Deep dives with examples and philosophy for every skill →

Parallel sprints

gstack works well with one sprint. It gets interesting with ten running at once.

Design is at the heart. /design-consultation builds your design system from scratch, researches the space, proposes creative risks, and writes DESIGN.md. /design-shotgun generates multiple visual variants and opens a comparison board so you can pick a direction. /design-html takes that approved mockup and generates production-quality HTML with Pretext, where text actually reflows on resize instead of breaking with hardcoded heights. Then /design-review and /plan-eng-review read what you chose. Design decisions flow through the whole system.

/qa was a massive unlock. It let me go from 6 to 12 parallel workers. Claude Code saying "I SEE THE ISSUE" and then actually fixing it, generating a regression test, and verifying the fix — that changed how I work. The agent has eyes now.

Smart review routing. Just like at a well-run startup: CEO doesn't have to look at infra bug fixes, design review isn't needed for backend changes. gstack tracks what reviews are run, figures out what's appropriate, and just does the smart thing. The Review Readiness Dashboard tells you where you stand before you ship.

Test everything. /ship bootstraps test frameworks from scratch if your project doesn't have one. Every /ship run produces a coverage audit. Every /qa bug fix generates a regression test. 100% test coverage is the goal — tests make vibe coding safe instead of yolo coding.

/document-release is the engineer you never had. It reads every doc file in your project, cross-references the diff, and updates everything that drifted. README, ARCHITECTURE, CONTRIBUTING, CLAUDE.md, TODOS — all kept current automatically. And now /ship auto-invokes it — docs stay current without an extra command.

Real browser mode. /open-gstack-browser launches GStack Browser, an AI-controlled Chromium with anti-bot stealth, custom branding, and the sidebar extension baked in. Sites like Google and NYTimes work without captchas. The menu bar says "GStack Browser" instead of "Chrome for Testing." Your regular Chrome stays untouched. All existing browse commands work unchanged. $B disconnect returns to headless. The browser stays alive as long as the window is open... no idle timeout killing it while you're working.

Sidebar agent — your AI browser assistant. Type natural language in the Chrome side panel and a child Claude instance executes it. "Navigate to the settings page and screenshot it." "Fill out this form with test data." "Go through every item in this list and extract the prices." The sidebar auto-routes to the right model: Sonnet for fast actions (click, navigate, screenshot) and Opus for reading and analysis. Each task gets up to 5 minutes. The sidebar agent runs in an isolated session, so it won't interfere with your main Claude Code window. One-click cookie import right from the sidebar footer.

Personal automation. The sidebar agent isn't just for dev workflows. Example: "Browse my kid's school parent portal and add all the other parents' names, phone numbers, and photos to my Google Contacts." Two ways to get authenticated: (1) log in once in the headed browser, your session persists, or (2) click the "cookies" button in the sidebar footer to import cookies from your real Chrome. Once authenticated, Claude navigates the directory, extracts the data, and creates the contacts.

Browser handoff when the AI gets stuck. Hit a CAPTCHA, auth wall, or MFA prompt? $B handoff opens a visible Chrome at the exact same page with all your cookies and tabs intact. Solve the problem, tell Claude you're done, $B resume picks up right where it left off. The agent even suggests it automatically after 3 consecutive failures.

Multi-AI second opinion. /codex gets an independent review from OpenAI's Codex CLI — a completely different AI looking at the same diff. Three modes: code review with a pass/fail gate, adversarial challenge that actively tries to break your code, and open consultation with session continuity. When both /review (Claude) and /codex (OpenAI) have reviewed the same branch, you get a cross-model analysis showing which findings overlap and which are unique to each.

Safety guardrails on demand. Say "be careful" and /careful warns before any destructive command — rm -rf, DROP TABLE, force-push, git reset --hard. /freeze locks edits to one directory while debugging so Claude can't accidentally "fix" unrelated code. /guard activates both. /investigate auto-freezes to the module being investigated.

Proactive skill suggestions. gstack notices what stage you're in — brainstorming, reviewing, debugging, testing — and suggests the right skill. Don't like it? Say "stop suggesting" and it remembers across sessions.

10-15 parallel sprints

gstack is powerful with one sprint. It is transformative with ten running at once.

Conductor runs multiple Claude Code sessions in parallel — each in its own isolated workspace. One session running /office-hours on a new idea, another doing /review on a PR, a third implementing a feature, a fourth running /qa on staging, and six more on other branches. All at the same time. I regularly run 10-15 parallel sprints — that's the practical max right now.

The sprint structure is what makes parallelism work. Without a process, ten agents is ten sources of chaos. With a process — think, plan, build, review, test, ship — each agent knows exactly what to do and when to stop. You manage them the way a CEO manages a team: check in on the decisions that matter, let the rest run.

---

Free, MIT licensed, open source. No premium tier, no waitlist.

I open sourced how I build software. You can fork it and make it your own.

We're hiring. Want to ship 10K+ LOC/day and help harden gstack? Come work at YC — ycombinator.com/software Extremely competitive salary and equity. San Francisco, Dogpatch District.

Docs

Doc	What it covers
Skill Deep Dives	Philosophy, examples, and workflow for every skill (includes Greptile integration)
Builder Ethos	Builder philosophy: Boil the Lake, Search Before Building, three layers of knowledge
Architecture	Design decisions and system internals
Browser Reference	Full command reference for /browse
Contributing	Dev setup, testing, contributor mode, and dev mode
Changelog	What's new in every version

Privacy & Telemetry

gstack includes opt-in usage telemetry to help improve the project. Here's exactly what happens:

• Default is off. Nothing is sent anywhere unless you explicitly say yes.
• On first run, gstack asks if you want to share anonymous usage data. You can say no.
• What's sent (if you opt in): skill name, duration, success/fail, gstack version, OS. That's it.
• What's never sent: code, file paths, repo names, branch names, prompts, or any user-generated content.
• Change anytime: gstack-config set telemetry off disables everything instantly.

Data is stored in Supabase (open source Firebase alternative). The schema is in supabase/migrations/ — you can verify exactly what's collected. The Supabase publishable key in the repo is a public key (like a Firebase API key) — row-level security policies deny all direct access. Telemetry flows through validated edge functions that enforce schema checks, event type allowlists, and field length limits.

Local analytics are always available. Run gstack-analytics to see your personal usage dashboard from the local JSONL file — no remote data needed.

Troubleshooting

Skill not showing up? cd ~/.claude/skills/gstack && ./setup

/browse fails? cd ~/.claude/skills/gstack && bun install && bun run build

Stale install? Run /gstack-upgrade — or set auto_upgrade: true in ~/.gstack/config.yaml

Want shorter commands? cd ~/.claude/skills/gstack && ./setup --no-prefix — switches from /gstack-qa to /qa. Your choice is remembered for future upgrades.

Want namespaced commands? cd ~/.claude/skills/gstack && ./setup --prefix — switches from /qa to /gstack-qa. Useful if you run other skill packs alongside gstack.

Codex says "Skipped loading skill(s) due to invalid SKILL.md"? Your Codex skill descriptions are stale. Fix: cd ~/.codex/skills/gstack && git pull && ./setup --host codex — or for repo-local installs: cd "$(readlink -f .agents/skills/gstack)" && git pull && ./setup --host codex

Windows users: gstack works on Windows 11 via Git Bash or WSL. Node.js is required in addition to Bun — Bun has a known bug with Playwright's pipe transport on Windows (bun#4253). The browse server automatically falls back to Node.js. Make sure both bun and node are on your PATH.

Claude says it can't see the skills? Make sure your project's CLAUDE.md has a gstack section. Add this:

## gstack
Use /browse from gstack for all web browsing. Never use mcp__claude-in-chrome__* tools.
Available skills: /office-hours, /plan-ceo-review, /plan-eng-review, /plan-design-review,
/design-consultation, /design-shotgun, /design-html, /review, /ship, /land-and-deploy,
/canary, /benchmark, /browse, /open-gstack-browser, /qa, /qa-only, /design-review,
/setup-browser-cookies, /setup-deploy, /retro, /investigate, /document-release, /codex,
/cso, /autoplan, /careful, /freeze, /guard, /unfreeze, /gstack-upgrade, /learn.

License

MIT. Free forever. Go build something.