groundwork: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 is a periodic, standalone check, not a required stop in the brainstorm -> ... -> build -> validate -> code-review chain. Run it whenever the codebase feels like it's accumulating friction, independent of any single feature in flight.

0. Preconditions

Read docs/groundwork/config.json. If it doesn't exist, don't stop - bootstrap it per the "Lazy bootstrap" section of the groundwork setup skill: detect tracker and project type, write the config with defaults, state the assumptions in one line, and continue. Running setup explicitly is only for customizing.

Glossary

Use these terms exactly in every suggestion. Consistent language is the point - don't drift into "component," "service," "API," or "boundary." Full definitions in LANGUAGE.md.

• Module - anything with an interface and an implementation (function, class, package, slice).
• Interface - everything a caller must know to use the module: types, invariants, error modes, ordering, config. Not just the type signature.
• Implementation - the code inside.
• Depth - leverage at the interface: a lot of behavior behind a small interface. Deep = high leverage. Shallow = interface nearly as complex as the implementation.
• Seam - where an interface lives; a place behavior can be altered without editing in place. (Use this, not "boundary.")
• Adapter - a concrete thing satisfying an interface at a seam.
• Leverage - what callers get from depth.
• Locality - what maintainers get from depth: change, bugs, knowledge concentrated in one place.

Key principles (see LANGUAGE.md for the full list):

• Deletion test: imagine deleting the module. If complexity vanishes, it was a pass-through. If complexity reappears across N callers, it was earning its keep.
• The interface is the test surface.
• One adapter = hypothetical seam. Two adapters = real seam.

This skill is informed by the project's domain model. docs/groundwork/glossary.md gives names to good seams; accepted ADRs record decisions the skill should not re-litigate.

Process

1. Explore

Read docs/groundwork/glossary.md and any ADRs in the area you're touching first - check docs/groundwork/adr/ for system-wide decisions not tied to one feature, and the relevant feature's docs/groundwork/features/NNNN-slug/adr/ if the area maps to work already in flight.

Then walk the codebase - through a read-only exploration worker if this runtime has one, directly if not. 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 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 <tmpdir>/architecture-review-<timestamp>.html so each run gets a fresh file. Open it for the user - xdg-open <path> on Linux, open <path> on macOS, start "" "<path>" on Windows (the empty "" avoids cmd treating a quoted path as the window title) - 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, before/after call-graph collapse). Each candidate gets a before/after visualization - static side-by-side, not an animation; the report has no interactivity beyond Mermaid's own rendering. Be visual.

For each candidate, the same template as before, but rendered as a card:

• 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 docs/groundwork/glossary.md vocabulary for the domain, and LANGUAGE.md vocabulary for the architecture. If the glossary 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 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. Interview loop

Once the user picks a candidate, drop into a groundwork:interview-loop session. 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 the glossary? Add or update an entry in docs/groundwork/glossary.md - a term and the one thing a newcomer must know to use it correctly, same format survey uses.
• Sharpening a fuzzy term during the conversation? Update docs/groundwork/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.

  Write it in Nygard format, same as survey:

  # MMMM. Title
  
  ## Status
  Accepted
  
  ## Context
  What forces are at play, including the option(s) considered.
  
  ## Decision
  What was decided.
  
  ## Consequences
  What becomes easier or harder as a result.

  If the candidate belongs to a feature already in flight, number it into that feature's docs/groundwork/features/NNNN-slug/adr/, scoped and sequenced the same way survey does. Otherwise - most deepening work isn't tied to a single feature - write it to docs/groundwork/adr/MMMM-title.md (create the directory lazily if it doesn't exist yet), numbered with the same four-digit sequence rule as feature-scoped ADRs but scoped to this directory - starting at 0001, next available after that - and sequenced independently of any feature. Either way, ADRs are append-only once Accepted: a change of mind is a new ADR that supersedes the old one, never an edit to a decided one.

• Want to explore alternative interfaces for the deepened module? See INTERFACE-DESIGN.md, which specialises the competing-designs pattern in ../_shared/COMPETING-DESIGNS.md - several candidates produced independently, then ranked by a worker that did not write any of them.

Write everything in the language the conversation has been in. No em dashes in any generated document.