improve-codebase-architecture

Files (3)

• HTML-REPORT.md
• SKILL.md
• openai.yaml · agents/

SKILL.md (first lines)

# Improve codebase architecture

Surface architectural friction and propose **deepening opportunities** that turn shallow modules into deep ones. The aim is testability and fewer modules to trace for one concept.

This command is _informed_ by the project's domain model and built on a shared design vocabulary:

- Run the `codebase-design` skill 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. Don't drift into "component," "service," "API," or "boundary."
- The domain language in `CONTEXT.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 module, subsystem, or pain point, start there and skip the inference below.
- Otherwise, inspect a useful stretch of commit history with `git log --oneline`. Start with the files and areas that change often. Widen the search if the history has no clear hot spot.

Read the project's domain glossary (`CONTEXT.md`) and any ADRs in the area you're touching first.

Then use the available subagent tool to start an exploration subagent. Ask it to note where it experiences 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 operating system's temporary directory so nothing lands in the repo. Resolve the directory from `$TMPDIR`, with `/tmp` as the Unix fallback and `%TEMP%` as the Windows fallback. Use `<tmpdir>/architecture-review-<timestamp>.html` so each run creates a new file.

Open the report with `xdg-open <path>` on Linux, `open <path>` on macOS, or `start <path>` on Windows. Tell the user its absolute path.

Use **Tailwind via CDN** for layout and styling. Use **Mermaid via CDN** for call graphs, dependency graphs, and sequences. Use custom CSS or SVG for mass diagrams, cross-sections, and collapse animations. Give each candidate a **before/after visualisation**.

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 CONTEXT.md vocabulary for the domain, and the `codebase-design` vocabulary for the architecture.** If `CONTEXT.md` defines "Order," talk about "the Order intake module", not "the FooBarHandler" or "the Order service".

**ADR conflicts.** Include a candidate that contradicts an ADR only when observed friction justifies reconsidering the decision. Mark the conflict in a warning callout and name the evidence. Do not list theoretical refactors that an ADR forbids.

See [HTML-REPORT.md](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. Planning loop

Once the user picks a candidate, run the `lets-plan-code` skill to explore its constraints, dependencies, module shape, seam, and surviving tests.

Side effects happen inline as decisions crystallize. Run the `domain-modeling` skill to keep the domain model current as you go:

- **Naming a deepened module after a concept not in `CONTEXT.md`?** Add the term to `CONTEXT.md`. Create the file lazily if it doesn't exist.
- **Sharpening a fuzzy term during the conversation?** Update `CONTEXT.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?** Run the `codebase-design` skill and use its design-it-twice parallel sub-agent pattern.

From terebentina/skills, MIT.

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