alexei-led/improving-codebase-architecture

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.

Role-gated action

This skill produces a candidate list and an agreed design, not edits. Both roles run it the same way; the difference is what happens after DESIGN AGREED:

• Write-capable role (engineer): hand the agreed design to refactoring-code to apply.
• Read-only role (reviewer): stop at DESIGN AGREED — it is the deliverable. Apply nothing.

Language detection and references

Detect the language from the file extensions in scope and load the matching reference for language-specific deepening patterns:

• Go → references/go.md
• Python → references/python.md
• TypeScript → references/typescript.md
• Web → references/web.md

Mixed languages: load each matching reference. Unknown language: use the language-agnostic vocabulary and process below only.

Critical Boundary Rules

• Do not use this skill for line-level cleanup: renames, formatting, comment cleanup, or one-file cosmetic edits.
• For line-level cleanup, say once: "This is not an architecture-deepening task." Route to reviewing-code, refactoring-code, or normal editing, and keep scope limited to the requested cleanup if proceeding.
• For line-level cleanup, do not mention modules, interfaces, seams, depth, leverage, locality, or other design terms. Ask once: "Do you want deeper architecture analysis, or should I keep this to the requested cleanup?"
• Seam discipline: do not add interfaces/ports for hypothetical variation. State that real variation is required before adding an interface/port: one adapter means hypothetical; two real adapters or confirmed variation means real.
• For valid architecture workflow descriptions, explicitly contrast deepening work with cosmetic or line-level cleanup.

Glossary

Use the module-depth vocabulary exactly in every suggestion — module, interface, implementation, depth, seam, adapter, leverage, locality — plus the deletion test, the interface-is-the-test-surface principle, and the one-adapter-vs-two seam rule. Full definitions and the complete principle list are in LANGUAGE.md; read it before naming candidates. Don't drift into "component," "service," "API," or "boundary."

This skill is informed by the project's domain model. The domain language gives names to good seams; ADRs record decisions the skill should not re-litigate.

Process

1. Explore

Read the project's domain glossary (CONTEXT.md / CONTEXT-MAP.md) and any ADRs in docs/adr/ for the area you're touching first. If the project uses brainstorming-ideas-style domain docs, that's where vocabulary and decisions live.

Then use the Agent tool with subagent_type=Explore 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 — 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

Present a numbered list of deepening opportunities. For each candidate:

• 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 also in how tests would improve

Use CONTEXT.md vocabulary for the domain, and LANGUAGE.md vocabulary for the architecture. If CONTEXT.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 (e.g. "contradicts ADR-0007 — but worth reopening because…"). Don't list every theoretical refactor an ADR forbids.

Do NOT propose interfaces yet. Ask the user: "Which of these would you like to explore?"

3. Grilling loop

Once the user picks a candidate, drop into a grilling conversation (see the brainstorming-ideas skill's references/grill-protocol.md for the interview discipline). Walk the design 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:

• Naming a deepened module after a concept not in CONTEXT.md? Add the term to CONTEXT.md with a tight one-sentence definition, same discipline as brainstorming-ideas. 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 in docs/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? See INTERFACE-DESIGN.md.

Failure handling

• No CONTEXT.md or ADRs found → proceed with exploration; note the absence; do not invent domain vocabulary.
• User asks for line-level cleanup (rename, formatting) → say once: "This is not an architecture-deepening task." Route to reviewing-code or refactoring-code and stop using architecture terminology.
• Candidate list rejected entirely → ask: "Is the friction you're experiencing in a specific area I haven't surfaced?" Narrow the explore scope before re-running.

Output format

ARCHITECTURE CANDIDATES
=======================
1. Files: <list>
   Problem: <friction description>
   Solution: <plain-English change>
   Benefits: locality — <how>; leverage — <how>; tests — <how>

2. ...

Which of these would you like to explore?

After the grilling loop resolves a candidate, output a brief summary:

DESIGN AGREED
=============
Candidate: <name>
Seam: <where>
Depth gained: <what moves behind the interface>
CONTEXT.md updated: yes | no
ADR offered: yes | no | n/a
Next step: use refactoring-code to apply