Part 1: gstack Pros, Cons, and Mode Selection

gstack is one of the most ambitious AI-assisted engineering systems available today. It gives you a full stack of opinionated workflows for planning, implementation, review, QA, security, release, and retros.

That power is real. So is the overhead.

What gstack Gets Right

Strong process guardrails across plan -> build -> review -> QA -> ship
Specialized skills for security, design, performance, and release quality
Great for parallel workstreams and larger feature programs
Better consistency when multiple contributors are using AI agents

Where gstack Can Hurt Day-to-Day Development

Too much ceremony for small bug fixes or one-file changes
Heavier cognitive load when you just need to move quickly
More prompts, reviews, and orchestration than many teams need per ticket
Can slow fast feedback loops for routine product iteration

For many teams, gstack is best treated as a high-rigor mode, not the default for every commit.

That is exactly why this series exists: you get a lighter workflow that still keeps quality high, using reusable skills shared across Claude Code and Codex.

Skill for This Post: `tooling-mode-selector`

This skill decides whether the current task should run in:

Lean mode (simple day-to-day ticket flow), or
gstack mode (high-risk, multi-team, or production-critical work)

Create .ai/skills/tooling-mode-selector/SKILL.md:

---
name: tooling-mode-selector
description: Choose lean workflow or gstack workflow based on risk, scope, and coordination needs.
---
 
# Tooling Mode Selector
 
## Decision Rules
Use gstack mode if ANY are true:
- cross-team coordination is required
- high blast radius (auth, billing, deploy infra, data migration)
- launch requires formal QA/security/release signoffs
- scope spans multiple subsystems with parallel streams
 
Use lean mode when:
- task is isolated and reversible
- requirements are clear
- standard code review + QA are enough
 
## Required Output
Return:
1) selected mode: lean | gstack
2) rationale in 3 bullets
3) next 5 actions

Share This Skill Across Claude and Codex with Symlinks

mkdir -p ~/.claude/skills ~/.codex/skills
ln -sfn "$PWD/.ai/skills/tooling-mode-selector" ~/.claude/skills/tooling-mode-selector
ln -sfn "$PWD/.ai/skills/tooling-mode-selector" ~/.codex/skills/tooling-mode-selector

If your Codex setup uses ~/.agents/skills instead of ~/.codex/skills, point the second symlink there.

What to Do Next

In Part 2, we define the exact day-to-day workflow:

PRD/Specs -> Task Breakdown -> Development -> Code Review -> QA -> UAT -> Production Deployment and Sanity

Then we encode that flow as one shared orchestrator skill used by both Claude Code and Codex.