gstack

Hi, I'm Garry Tan. I'm President & CEO of Y Combinator, where I've worked with thousands of startups including Coinbase, Instacart, and Rippling when the founders were just one or two people in a garage — companies now worth tens of billions of dollars. Before YC, I designed the Palantir logo and was one of the first eng manager/PM/designers there. I cofounded Posterous, a blog platform we sold to Twitter. I built Bookface, YC's internal social network, back in 2013. I've been building products as a designer, PM, and eng manager for a long time.

And right now I am in the middle of something that feels like a new era entirely.

In the last 60 days I have written over 600,000 lines of production code — 35% tests — and I am doing 10,000 to 20,000 usable lines of code per day as a part-time part of my day while doing all my duties as CEO of YC. That is not a typo. My last /retro (developer stats from the last 7 days) across 3 projects: 140,751 lines added, 362 commits, ~115k net LOC. The models are getting dramatically better every week. We are at the dawn of something real — one person shipping at a scale that used to require a team of twenty.

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 is my open source software factory. It turns Claude Code into a virtual engineering team you actually manage — a CEO who rethinks the product, an eng manager who locks the architecture, a designer who catches AI slop, a paranoid reviewer who finds production bugs, a QA lead who opens a real browser and clicks through your app, and a release engineer who ships the PR. Fifteen specialists and six power tools, all as slash commands, all Markdown, all free, MIT license, available right now.

I am learning how to get to the edge of what agentic systems can do as of March 2026, and this is my live experiment. I am sharing it because I want the whole world on this journey with me.

Fork it. Improve it. Make it yours. Don't player hate, appreciate.

Who this is for:

• Founders and CEOs — especially technical ones who still want to ship. This is how you build like a team of twenty.
• First-time Claude Code users — gstack is the best way to start. Structured roles instead of a blank prompt.
• Tech leads and staff engineers — bring rigorous review, QA, and release automation to every PR

Quick start: your first 10 minutes

1. Install gstack (30 seconds — see below)
2. Run /office-hours — describe what you're building. It will reframe the problem before you write a line of code.
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.

Expect first useful run in under 5 minutes on any repo with tests already set up.

If you only read one more section, read this one.

Install — takes 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 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, /review, /ship, /browse, /qa, /qa-only, /design-review, /setup-browser-cookies, /retro, /investigate, /document-release, /codex, /careful, /freeze, /guard, /unfreeze, /gstack-upgrade. 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, /review, /ship, /browse, /qa, /qa-only, /design-review, /setup-browser-cookies, /retro, /investigate, /document-release, /codex, /careful, /freeze, /guard, /unfreeze, /gstack-upgrade, 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.

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.

git clone https://github.com/garrytan/gstack.git ~/.codex/skills/gstack
cd ~/.codex/skills/gstack && ./setup --host codex

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

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

This installs to ~/.claude/skills/gstack and/or ~/.codex/skills/gstack depending on what's available. All 21 skills work across all supported agents. Hook-based safety skills (careful, freeze, guard) use inline safety advisory prose on non-Claude hosts.

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. Then it challenged your premises, generated three approaches, recommended the narrowest wedge, and wrote a design doc that fed into every downstream skill. Eight commands. That is not a copilot. That is a team.

The sprint

gstack is a process, not a collection of tools. The skills are ordered the way 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.

One sprint, one person, one feature — that takes about 30 minutes with gstack. But here's what changes everything: you can run 10-15 of these sprints in parallel. Different features, different branches, different agents — all at the same time. That is how I ship 10,000+ lines of production code per day while doing my actual job.

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.
/design-consultation	Design Partner	Build a complete design system from scratch. Knows the landscape, proposes creative risks, generates realistic product mockups. Design at the heart of all other phases.
/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.
/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. Use when you want a pure bug report without code changes.
/ship	Release Engineer	Sync main, run tests, audit coverage, push, open PR. Bootstraps test frameworks if you don't have one. One command.
/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.
/browse	QA Engineer	Give the agent eyes. Real Chromium browser, real clicks, real screenshots. ~100ms per command.
/setup-browser-cookies	Session Manager	Import cookies from your real browser (Chrome, Arc, Brave, Edge) into the headless session. Test authenticated pages.

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.
/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 →

What's new and why it matters

/office-hours reframes your product before you write code. You say "daily briefing app." It listens to your actual pain, pushes back on the framing, tells you you're really building a personal chief of staff AI, challenges your premises, and generates three implementation approaches with effort estimates. The design doc it writes feeds directly into /plan-ceo-review and /plan-eng-review — so every downstream skill starts with real clarity instead of a vague feature request.

Design is at the heart. /design-consultation doesn't just pick fonts. It researches what's out there in your space, proposes safe choices AND creative risks, generates realistic mockups of your actual product, and writes DESIGN.md — and 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.

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.

---

Come ride the wave

This is free, MIT licensed, open source, available now. No premium tier. No waitlist. No strings.

I open sourced how I do development and I am actively upgrading my own software factory here. You can fork it and make it your own. That's the whole point. I want everyone on this journey.

Same tools, different outcome — because gstack gives you structured roles and review gates, not generic agent chaos. That governance is the difference between shipping fast and shipping reckless.

The models are getting better fast. The people who figure out how to work with them now — really work with them, not just dabble — are going to have a massive advantage. This is that window. Let's go.

Fifteen specialists and six power tools. All slash commands. All Markdown. All free. github.com/garrytan/gstack — MIT License

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)
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/001_telemetry.sql — 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 restrict it to insert-only access.

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

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, /review, /ship, /browse, /qa, /qa-only, /design-review,
/setup-browser-cookies, /retro, /investigate, /document-release, /codex, /careful,
/freeze, /guard, /unfreeze, /gstack-upgrade.

License

MIT. Free forever. Go build something.