arch-review

name	arch-review
description	Mid-session codebase architecture review. All exploration runs in isolated subagents so findings never pollute main context. Surfaces shallow modules, coupling smells, and testability gaps as an HTML report. Use between tasks to retrospect on architecture without bloating the session context window.

Architecture Review

Surface architectural friction in the current codebase without polluting the main session context. All heavy exploration runs in subagents — only distilled findings enter your conversation.

Glossary (use these terms exactly in all findings and reports)

• Module — anything with an interface and an implementation (function, class, package, file)
• Deep module — high leverage: significant behaviour behind a small interface
• Shallow module — low leverage: interface nearly as complex as the implementation
• Seam — where an interface lives; where behaviour can be altered without editing in place
• Locality — change, bugs, and knowledge concentrated in one place
• Deletion test — delete the module mentally: does complexity vanish (it was a pass-through) or reappear across N callers (it was earning its keep)?

Context hygiene — choose your isolation level

This skill runs subagents to keep raw exploration output out of context, but the findings summary and grilling conversation still land in your main session. Two native Claude Code commands let you go further:

Want	Do
Full branch isolation — review findings disappear if you don't like them	Type /fork, then invoke /groundwork:arch-review. Type /resume to roll back entirely, or keep the branch if findings are useful.
One quick question without any context cost	Skip this skill. Type /btw [your architecture question] directly — it's read-only, ephemeral, and never enters history. Best for "is this pattern ok?" asides, not full reviews.
Findings in main context (discuss and act on immediately)	Invoke /groundwork:arch-review directly — no fork needed.

Recommended default: /fork before invoking. The branch costs nothing if you discard it.

When to Use

• Between tasks: "how does the architecture look so far?"
• After implementing a feature: did we introduce new coupling or shallow modules?
• When repeated friction appears: same files touched in every change, test setup growing unwieldy
• User says "review the structure", "any concerns about the codebase?", "improve architecture"

Process

Phase 1 — Explore in parallel subagents

NEVER explore directly. Every byte of exploration output must stay out of main context.

Spawn multiple Explore subagents simultaneously — one per codebase area. Adapt the areas to the actual project shape, but typical targets:

• Core domain / business logic
• Entry points (routers, controllers, CLI commands, event handlers)
• Data layer (persistence, queries, models)
• Shared utilities / helpers
• Test structure

Each subagent prompt (fill in [AREA]):

Explore [AREA] in this codebase. Return ONLY structured findings — no prose padding.

For each issue found, return:
- file: path/to/file.ts (+ line range if relevant)
- type: shallow_module | tight_coupling | testability_gap | pass_through | naming_inconsistency
- summary: one sentence describing the friction
- deletion_test: pass | fail | n/a
- strength: strong | worth_exploring | speculative

Limit: top 5 findings per area. Be specific — file paths and function names, not vague descriptions.

Collect all findings as Task return values. Do not log them into your conversation.

After all subagents return: deduplicate by file, discard speculative findings that duplicate stronger ones, and keep ≤15 candidates total for the report.

Phase 2 — HTML report

Write a self-contained HTML report to the OS temp directory:

• Resolve temp dir: $TMPDIR → /tmp (Linux/macOS) → %TEMP% (Windows)
• Filename: arch-review-<timestamp>.html
• Use Tailwind via CDN for layout and Mermaid via CDN for graph-shaped diagrams
• Open with: xdg-open (Linux), open (macOS), start (Windows)
• Print the absolute path

Each candidate renders as a card:

Field	Content
Files	Which files/modules are involved (with paths)
Problem	Why this causes friction — use Glossary terms
Solution	What deepening would look like
Benefit	Locality gained, leverage gained, testability improvement
Before/After diagram	Side-by-side — Mermaid for call graphs/dependencies; hand-crafted divs for depth/mass
Strength badge	Strong · Worth exploring · Speculative

End the report with a Top recommendation section: which candidate to tackle first and why.

Do NOT propose concrete interfaces or implementation details in the report.

After writing the report, present a compact list to the user (≤12 lines total):

Architecture review complete. Found N candidates:

1. [Title] — [one-line problem] (Strong)
2. [Title] — [one-line problem] (Worth exploring)
...

Report: /tmp/arch-review-<timestamp>.html
Which would you like to explore?

Phase 3 — Grilling loop

Once the user picks a candidate, enter a conversational grilling loop:

• Walk through constraints, dependencies, the shape of the deepened module
• What sits behind the seam? What callers simplify? What tests would survive?
• Challenge shallow reasoning: "if we deleted this module, where does the complexity go?"

Side effects as decisions crystallize:

• New concept not in project docs? → Offer to add it to CONTEXT.md (create lazily if absent). Use project domain vocabulary, not generic terms.
• User rejects with a load-bearing reason? → Offer an ADR: "Want me to record this so future reviews don't re-suggest it?" Only offer when the reason would genuinely matter to a future explorer — skip ephemeral reasons ("not now") or self-evident ones.
• Ready to act? → Route to groundwork:general-purpose with: the candidate description, agreed interface shape, and success criteria.

Context budget rules

These are mandatory, not advisory:

1. Phase 1 output never enters your context directly. Collect findings via Task return values only.
2. If a subagent returns more than 20 lines, ask it to summarise to ≤10 bullets before returning.
3. Use ctx_batch_execute for any file-count or structural analysis — never sequential Bash grepping.
4. Your summary to the user after Phase 2 is ≤12 lines. The HTML file is the full artifact.
5. No files created in the repo. Temp dir only.

Completion gate

After Phase 2, invoke advisor-gate with:

• Total candidates found and their strength distribution
• Top recommendation + rationale
• Any ADRs that would be contradicted

advisor-gate response governs:

• APPROVE → present to user as written
• REVISE → tighten recommendations (too speculative? re-rank) and re-run advisor-gate
• REJECT → tell user "analysis too speculative for this codebase shape — need to scope narrower" and re-enter Phase 1 with a single focused area

What NOT to Do

• Do not read raw file contents into your conversation to find patterns — that's subagents' job
• Do not propose implementation details before the user picks a candidate
• Do not run sequential grep calls — one ctx_batch_execute covers all discovery
• Do not create files in the repo — temp dir only
• Do not skip advisor-gate even when findings seem obvious
• Do not conflate this with diagnose — this skill finds architectural friction, not bugs