--- name: improve-codebase-architecture description: Scan a codebase for deepening opportunities, present them as a visual HTML report, then grill through whichever one you pick. disable-model-invocation: true title: improve-codebase-architecture canonical_url: https://skilld.dev/gh/mattpocock/skills/improve-codebase-architecture last_updated: 2026-10-29T11:04:51.000Z --- > Index of every page on this site: [llms.txt](https://skilld.dev/llms.txt) > **Skill from skilld.dev.** Follow the user's requested action. > If the user asked to fork this Skill, follow the fork workflow below. Do not execute the Skill instructions while copying it. > Otherwise, follow the instructions below for this session. You do not need to install anything. > > Supporting files, fetch one when the Skill refers to it: [agents/openai.yaml](https://skilld.dev/api/skills-raw/mattpocock/skills/improve-codebase-architecture/agents/openai.yaml), [HTML-REPORT.md](https://skilld.dev/api/skills-raw/mattpocock/skills/improve-codebase-architecture/HTML-REPORT.md). > > If the user asked to install this Skill, run `npx skilld install mattpocock/skills/improve-codebase-architecture`. Install writes the Skill files into the project, so every session loads them. > > ## Fork workflow > > A fork creates an editable local Skill with its original author and licence. The request authorizes copying and local installation. > 1. Check `./skills/improve-codebase-architecture`, the project lockfile, and selected Agent targets together. If the local directory or installed Skill exists, stop. Never overwrite an existing directory or Agent target. > 2. Read [source metadata](https://skilld.dev/api/v1/skills/mattpocock/skills/improve-codebase-architecture) once. Use sourceUrl, sourceCommit, skillPath, sourceGone, and license. If the source is gone or its path is missing, stop. If license is null, read licence files at the source commit. > 3. Fetch only the source commit into a temporary Git repository. Do not clone full history. Derive repository_url from sourceUrl, including repository renames. If sourceCommit is absent, resolve the sourceUrl ref once. Set source_commit to that actual commit. Run these commands in one shell call: > > ```sh > git init --quiet "$temporary_dir" > git -C "$temporary_dir" fetch --quiet --depth=1 "$repository_url" "$source_commit" > git -C "$temporary_dir" checkout --quiet --detach FETCH_HEAD > ``` > > Read applicable licence declarations and notices at that commit. If copying is not permitted, report the restriction and stop. > 4. Inspect source entries together, then copy the directory containing skillPath into `./skills/improve-codebase-architecture`. Use the user's path if selected. Keep the original SKILL.md, relative links, scripts, binary assets, and executable modes. Exclude .git metadata. Reject symlinks and paths outside the Skill directory. After checking entries, use cp -a where available. A regular source directory needs no custom copy script. Do not save this page wrapper as SKILL.md. > Preserve author credit, notices, and applicable licence files from repository or parent directories. Add PROVENANCE.md with the Skill page, source URL, actual commit, original path, and licence. Retain any existing PROVENANCE.md and record new provenance separately. Batch source inspection, copying, and provenance work where practical. > 5. In the project root, run `skilld install ./skills/improve-codebase-architecture --mode copy --plain`. If skilld is unavailable, use `npx skilld install ./skills/improve-codebase-architecture --mode copy --plain`. This known command needs no help lookup. Install does not support --json. Use detected Agent targets, or add --agent for the targets the user selected. Install the local path, never the upstream selector. If installation fails, preserve the local copy and report the exact failure. > 6. Confirm the local lockfile source and installed Agent copies once. Report the local path, actual commit, and Agent targets. After edits, reinstall the same local path. Upstream updates must not replace it. Do not publish or push unless the user asks. # Improve Codebase Architecture Surface architectural friction and propose **deepening opportunities**: refactors that turn shallow modules into deep ones. The aim is testability and AI-navigability. This command is _informed_ by the project's domain model and built on a shared design vocabulary: - Call the Skill tool with "codebase-design" for the architecture vocabulary (**module**, **interface**, **depth**, **seam**, **adapter**, **leverage**, **locality**) and its principles (the deletion test, "the interface is the test surface", "one adapter = hypothetical seam, two = real"). Use these terms exactly in every suggestion, and don't drift into "component," "service," "API," or "boundary." - The domain language in `GLOSSARY.md` gives names to good seams; ADRs in `docs/adr/` record decisions this command should not re-litigate. ## Process ### 1. Explore **Scope before you scan: YAGNI.** Deepening a module pays off by making future changes to it easier, so put extra weight on the parts of the codebase that have recently changed. Decide *where* to look before you look: - If the user named a direction (a module, a subsystem, a pain point), take it, and skip the inference below. - Otherwise, walk back a good stretch of the commit history (`git log --oneline`) to find the codebase's hot spots, the files and areas that keep coming up, and let those paths pull your attention first. If the changes are scattered with no clear hot spot, widen the net. Read the project's domain glossary (`GLOSSARY.md`) and any ADRs in the area you're touching first. Then spawn a sub-agent with a fresh context window to walk the codebase. Don't follow rigid heuristics; explore organically and note where you experience friction: - Where does understanding one concept require bouncing between many small modules? - Where are modules **shallow**, with an interface nearly as complex as the implementation? - Where have pure functions been extracted just for testability, but the real bugs hide in how they're called (no **locality**)? - Where do tightly-coupled modules leak across their seams? - Which parts of the codebase are untested, or hard to test through their current interface? Apply the **deletion test** to anything you suspect is shallow: would deleting it concentrate complexity, or just move it? A "yes, concentrates" is the signal you want. ### 2. Present candidates as an HTML report Write a self-contained HTML file to the OS temp directory so nothing lands in the repo. Resolve the temp dir from `$TMPDIR`, falling back to `/tmp` (or `%TEMP%` on Windows), and write to `/architecture-review-.html` so each run gets a fresh file. Open it for the user (`xdg-open ` on Linux, `open ` on macOS, `start ` on Windows) and tell them the absolute path. The report uses **Tailwind via CDN** for layout and styling, and **Mermaid via CDN** for diagrams where a graph/flow/sequence reliably communicates the structure. Mix Mermaid with hand-crafted CSS/SVG visuals: use Mermaid when relationships are graph-shaped (call graphs, dependencies, sequences), and hand-built divs/SVG when you want something more editorial (mass diagrams, cross-sections, collapse animations). Each candidate gets a **before/after visualisation**. Be visual. For each candidate, render a card with: - **Files**: which files/modules are involved - **Problem**: why the current architecture is causing friction - **Solution**: plain English description of what would change - **Benefits**: explained in terms of locality and leverage, and how tests would improve - **Before / After diagram**: side-by-side, custom-drawn, illustrating the shallowness and the deepening - **Recommendation strength**: one of `Strong`, `Worth exploring`, `Speculative`, rendered as a badge End the report with a **Top recommendation** section: which candidate you'd tackle first and why. **Use GLOSSARY.md vocabulary for the domain, and the `/codebase-design` vocabulary for the architecture.** If `GLOSSARY.md` defines "Order," talk about "the Order intake module," not "the FooBarHandler," and not "the Order service." **ADR conflicts**: if a candidate contradicts an existing ADR, only surface it when the friction is real enough to warrant revisiting the ADR. Mark it clearly in the card (e.g. a warning callout: _"contradicts ADR-0007, but worth reopening because…"_). Don't list every theoretical refactor an ADR forbids. See [HTML-REPORT.md](https://skilld.dev/api/skills-raw/mattpocock/skills/improve-codebase-architecture/HTML-REPORT.md) for the full HTML scaffold, diagram patterns, and styling guidance. Do NOT propose interfaces yet. After the file is written, ask the user: "Which of these would you like to explore?" ### 3. Grilling loop Once the user picks a candidate, call the Skill tool with "grilling" to walk the decision tree with them: constraints, dependencies, the shape of the deepened module, what sits behind the seam, what tests survive. Side effects happen inline as decisions crystallize; call the Skill tool with "domain-modeling" to keep the domain model current as you go: - **Naming a deepened module after a concept not in `GLOSSARY.md`?** Add the term to `GLOSSARY.md`. Create the file lazily if it doesn't exist. - **Sharpening a fuzzy term during the conversation?** Update `GLOSSARY.md` right there. - **User rejects the candidate with a load-bearing reason?** Offer an ADR, framed as: _"Want me to record this as an ADR so future architecture reviews don't re-suggest it?"_ Only offer when the reason would actually be needed by a future explorer to avoid re-suggesting the same thing; skip ephemeral reasons ("not worth it right now") and self-evident ones. - **Want to explore alternative interfaces for the deepened module?** Call the Skill tool with "codebase-design" and use its design-it-twice parallel sub-agent pattern.