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Lean Build

Guides the agent to build features narrowly, reuse existing code, and stop once acceptance passes.

Source Download skill
Repository
JuliusBrussee/caveman
Stars
116,835
Licence
Apache-2.0
Files
2 files

What it does

When installed, this skill changes how the agent approaches feature work in a codebase. Before writing code, it pushes the agent to define what success looks like and what is explicitly out of scope, trace the request through the layers that own the relevant behavior, and reuse existing code where it fits instead of adding extra modes, configuration, or extensibility nobody asked for. It also tells the agent to stop once the acceptance criteria pass and report only material omissions.

Great for

  • Developers adding a new behavior, product slice, or integration to an existing repository who want to avoid overbuilding
  • Teams that want an AI agent to keep changes scoped and reuse current architecture
  • People who have seen agents add unnecessary abstractions or config and want tighter output

Skip it if

  • Greenfield projects or quick throwaway scripts where broad design freedom is wanted, since the skill pushes toward reuse and narrow scope
  • Tasks with no repository context, because the skill assumes an existing codebase to trace and reuse
  • Anyone expecting a security review; the skill says to preserve safety but does not provide security checks

Try asking

  • “Add a CSV export option to the reports feature, keeping the change narrow and reusing the existing export path”
  • “Implement a webhook integration for order updates following the layers already used by the payments module”
  • “Build the new user-preferences toggle end to end, then stop once the stated acceptance tests pass”
Step-by-step guide: how to use Lean BuildInstall, first run, examples, tips and FAQs

Install in 3 steps

  1. 1

    Download the skill

    The ZIP contains the 2 original files, the Apache-2.0 licence and an attribution note.

    lean-build.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

    mkdir -p ~/.claude/skills && unzip lean-build.zip -d ~/.claude/skills/

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip lean-build.zip -d .claude/skills/

    Claude apps (web/desktop): Settings → Capabilities → Skills → Upload skill, and choose the ZIP.

  3. 3

    Ask for the task

    No special command needed — the agent reads the skill's description and loads it when your request matches. Try one of the prompts above.

Get better results

  • State your acceptance criteria and non-goals explicitly in the request so the agent has a clear stop condition.
  • Point the agent at the entry point or relevant module if you know it, to help it trace the path through layers.
  • Review the tradeoffs the agent reports, since it is instructed to state material tradeoffs for any added dependency or config.

What's inside

  • agents/openai.yaml
  • SKILL.md

Redistributed unmodified from JuliusBrussee/caveman under the Apache-2.0 licence. The assessment was drafted with AI from the skill's files on 2026-10-29. Skills can instruct your agent to run code — read SKILL.md and any scripts before installing.