--- title: "Matt Pocock Codebase Design: review, setup & limitations · Undominated.ai" canonical: https://undominated.ai/skills/mattpocock-codebase-design/ description: "Evaluates module boundaries through caller complexity, dependency seams and alternative interface designs." --- # Matt Pocock Codebase Design: review, setup & limitations · Undominated.ai > Evaluates module boundaries through caller complexity, dependency seams and alternative interface designs. [← Explore all skills](/skills/) WEB DEVELOPMENT / Matt Pocock # Matt Pocock Codebase Design Evaluates module boundaries through caller complexity, dependency seams and alternative interface designs. See setup guidance ↓Original source ↗ SOURCE REVIEW Reviewed 2026-09-21 Evidence 14 linked sources Publisher Matt Pocock Licence MIT ↗ Revision c55ee46073ed Read what was—and wasn’t—checked ↓ “Shared vocabulary for designing deep modules. Use when the user wants to design or improve a module's interface, find deepening opportunities, decide where a” Matt Pocock · upstream description ↗ Our analysis follows below. 01 / THE REASONING ## Why this made the selection. - Defines a deep module by what callers can accomplish through a small interface, rather than by its line count. - Distinguishes internal dependencies, local substitutes and external boundaries, then compares alternative interfaces before choosing a design. ### A good fit for - Reviewing a proposed module boundary - Planning a refactor that reduces how many files callers must understand ### Weigh up before choosing - The adapter and interface rules are design heuristics, not universal requirements; local substitutes do not prove production integration behavior. - The alternative-design exercise assumes subagents. Advice to delete old tests requires checking that replacement tests preserve their unique coverage. 02 / THE REVIEW RECORD ## What we actually inspected. Source review has boundaries. A clear record is more useful than a “safe” badge. ### Material inspected - skills/engineering/codebase-design/DEEPENING.md - skills/engineering/codebase-design/DESIGN-IT-TWICE.md - skills/engineering/codebase-design/SKILL.md - skills/engineering/codebase-design/agents/openai.yaml - skills/engineering/setup-matt-pocock-skills/SKILL.md - skills/engineering/setup-matt-pocock-skills/agents/openai.yaml - skills/engineering/setup-matt-pocock-skills/domain.md - skills/engineering/setup-matt-pocock-skills/issue-tracker-github.md - skills/engineering/setup-matt-pocock-skills/issue-tracker-gitlab.md - skills/engineering/setup-matt-pocock-skills/issue-tracker-local.md - skills/engineering/setup-matt-pocock-skills/triage-labels.md - README.md (installation, compatibility and licence sections) - LICENSE ### Our findings - The definition, deepening guide and alternative-design guide were all inspected. They give a shared vocabulary and a concrete comparison procedure. - The skill can guide changes to code and tests but supplies no executable check that the resulting interface is better. ### Not established by this review - No refactor or interface comparison was performed. - No claim of reduced defects, token usage or maintenance time was measured. The review applies to the material and revision named here. A newer upstream release can change its behavior. 03 / PUT IT TO WORK ## Add a skill to your workflow. Upstream setup instructions ↗ DOCUMENTED COMMAND npx skills add https://github.com/mattpocock/skills/tree/c55ee46073ed923f86ce59a5eb3b6d895095d1b7 --skill codebase-design --skill setup-matt-pocock-skills Copy command ↗ Copying does not execute this command. It may retrieve a newer version than the reviewed source. - Keep DEEPENING.md and DESIGN-IT-TWICE.md with the installed definition. - Choose a bounded module or seam and review the proposed design before authorizing code or test replacement. - The publisher recommends setup-matt-pocock-skills as a separate companion. Review its repository documentation and issue-tracker changes before running it. - Choose the intended host and project scope in the installer. The source revision is pinned; the installer itself is not executed or version-pinned by this review. ### Before you start - Node.js/npm and git for the documented Skills installer - A codebase and its tests - Subagent support for the optional independent-interface exercise; project domain vocabulary when using that exercise - The separately selected setup companion establishes the repository conventions; review its proposed AGENTS.md or CLAUDE.md and docs/agents edits before accepting them. ### Compatibility Claude Code · Codex ### Code, tests and design notes - Read repository code and tests - Delegate bounded interface research when the host supports it - Edit modules and replace tests only within the requested refactor ### Cost model MIT-licensed instructions; agent and optional subagent calls consume the host account or API allowance. 04 / FOLLOW THE EVIDENCE ## The source trail. Our notes are separate from the original resource. Check upstream before adopting a new version. - Skill definition at reviewed revision ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/codebase-design/SKILL.md Supports: summary, upstreamDescription, whySelected, bestFor, limitations, review, access - Reviewed reference or helper: DEEPENING.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/codebase-design/DEEPENING.md Supports: review, limitations, install, access - Reviewed reference or helper: DESIGN-IT-TWICE.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/codebase-design/DESIGN-IT-TWICE.md Supports: review, limitations, install, access - Reviewed reference or helper: skills/engineering/setup-matt-pocock-skills/SKILL.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/setup-matt-pocock-skills/SKILL.md Supports: review, limitations, install, access - Reviewed reference or helper: skills/engineering/setup-matt-pocock-skills/domain.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/setup-matt-pocock-skills/domain.md Supports: review, limitations, install, access - Reviewed reference or helper: skills/engineering/setup-matt-pocock-skills/issue-tracker-github.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/setup-matt-pocock-skills/issue-tracker-github.md Supports: review, limitations, install, access - Reviewed reference or helper: skills/engineering/setup-matt-pocock-skills/issue-tracker-gitlab.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/setup-matt-pocock-skills/issue-tracker-gitlab.md Supports: review, limitations, install, access - Reviewed reference or helper: skills/engineering/setup-matt-pocock-skills/issue-tracker-local.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/setup-matt-pocock-skills/issue-tracker-local.md Supports: review, limitations, install, access - Reviewed reference or helper: skills/engineering/setup-matt-pocock-skills/triage-labels.md ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/skills/engineering/setup-matt-pocock-skills/triage-labels.md Supports: review, limitations, install, access - Publisher installation, compatibility and licensing guidance ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/README.md Supports: install, compatibility, access, license - Upstream licence at reviewed revision ↗ Checked 2026-09-21 https://github.com/mattpocock/skills/blob/c55ee46073ed923f86ce59a5eb3b6d895095d1b7/LICENSE Supports: license, access.cost - Skills installer: source formats and repeated skill selection ↗ Checked 2026-09-21 https://github.com/vercel-labs/skills/blob/7407f3893ad4dceab546ac002c3ef806e4000c73/README.md Supports: install - Skills installer: full commit SHA checkout support ↗ Checked 2026-09-21 https://github.com/vercel-labs/skills/blob/7407f3893ad4dceab546ac002c3ef806e4000c73/src/git.ts Supports: install - Skills installer: tree revision and subdirectory parsing ↗ Checked 2026-09-21 https://github.com/vercel-labs/skills/blob/7407f3893ad4dceab546ac002c3ef806e4000c73/src/source-parser.ts Supports: install KEEP COMPARING ## Other approaches to consider. Related by category or shared topics. These are alternatives to inspect, not a measured quality order. [### Vercel React Composition Patterns ↗ Replaces growing boolean-mode APIs with explicit component composition and provider-owned state contracts.](/skills/vercel-labs-composition-patterns/)[### Vercel React Best Practices ↗ Organizes React and Next.js performance reviews around request waterfalls, bundles, server work and rendering costs.](/skills/vercel-labs-react-best-practices/)[### Microsoft Wiki Researcher ↗ Traces architecture and data flow through source code to produce an explanation with file references, diagrams and stated uncertainties.](/skills/microsoft-wiki-researcher/) [AI Tools ↗](/tools/)[Skills ↗](/skills/)[Agents ↗](/agents/)[MCP Servers ↗](/mcp-servers/)