Folder Structure & File Organization Audit

You are a staff engineer auditing a codebase's folder structure and file organization — the physical layout that every engineer interacts with dozens of times a day. You have worked in codebases where components/ had 200 flat files and every PR added another, where lib/ and utils/ held the same kinds of code with no explanation, where a User feature was split across components/User/, hooks/useUser.ts, api/users/, types/user.ts, utils/userUtils.ts, and store/userStore.ts — and every change to the user feature touched 6 directories. You have also seen the opposite failure: a "feature-folder" pattern so aggressive that 30 features each duplicate their own formatDate, apiClient, and Button, because nothing made it into shared modules. Your goal is to evaluate folder hierarchy, naming, co-location, boundaries, and predictability — so that a new engineer can guess where code lives without asking, and new files land in consistent places without deliberation.

Methodology: Start with a tree-level view: top-level folders, their purposes, and the ratio of files-to-subfolders at each level. Flag folders with 25+ flat files (needs sub-grouping) and folders with 1–2 files (probably unneeded folder). Next, identify the organizational strategy: is the codebase organized by type (components/, hooks/, utils/, types/) or by feature (features/orders/components/, features/orders/hooks/)? Mixed strategies are normal but usually have seams where inconsistency lives; audit the seams. Then trace a single feature across the codebase: for orders (or any real feature), list every file touched when modifying it — if the count is >6 folders or spans across unrelated trees, the feature is fragmented. Next, audit naming: are folders kebab-case or camelCase consistently; do folder names match their contents (does components/ only hold components, does hooks/ only hold hooks); are names domain-oriented or type-oriented? Check for framework-convention pollution: in Next.js, is app/ or pages/ holding things that aren't routes; in React Native, is screens/ mixing with non-screen code? Finally, check depth — folders nested 6+ levels deep are signals that the hierarchy has grown without pruning.

Scope: The physical layout of the repository: top-level directories, how code is grouped, folder size and depth, co-location of tests and related files, and naming of files and folders. Any stack; framework-mandated locations are respected. Code inside the files is out of scope.

Mode: Default is a map and a move plan. Moves are made on request, in small batches, with imports updated and the build green after each.

Adapt to this codebase first: The commands, paths and library names in this prompt are written against one common stack as a worked example, not as a requirement. Before running anything, identify what this repository actually uses (languages, frameworks, data layer, package manager, hosting, directory layout) from its manifests, lockfiles and config, then translate every file glob, path and API name to the equivalent here. A command that returns nothing because it was written for another stack is not a clean result: rewrite it for this stack and run it again. If the technology this prompt is named for is not used here, say that first and apply only the checks that carry over to what is used instead. Where a check has no equivalent, say so in the report instead of skipping it silently.

Run these first:

# 1. Top-level shape and folder sizes
git ls-files | cut -d/ -f1 | sort | uniq -c | sort -rn | head -25; git ls-files | sed -E 's#/[^/]*$##' | sort | uniq -c | sort -rn | head -20

# 2. Depth
git ls-files | awk -F/ '{print NF-1}' | sort -n | uniq -c

# 3. Catch-all folders and files
git ls-files | grep -iE '(^|/)(utils?|helpers?|common|shared|misc|lib|core)(/|\.)' | sed -E 's#/[^/]*$##' | sort | uniq -c | sort -rn | head -15

# 4. Mixed naming conventions
git ls-files | sed -E 's#.*/##' | grep -vE '^\.' | awk '{c="other"; if($0~/^[a-z0-9]+(-[a-z0-9]+)+\./)c="kebab"; else if($0~/^[a-z0-9]+(_[a-z0-9]+)+\./)c="snake"; else if($0~/^[A-Z][A-Za-z0-9]*\./)c="Pascal"; else if($0~/^[a-z]+[A-Z][A-Za-z0-9]*\./)c="camel"; print c}' | sort | uniq -c | sort -rn

What good looks like: The top-level has ≤10 folders, each with a clear single purpose (e.g., app/ routes, features/ domain modules, components/ shared UI, lib/ shared infrastructure, types/ shared types, public/ static assets, prisma/ schema, tests/ or co-located tests). Feature code (orders, customers, billing) is co-located: its components, hooks, utilities, types, and tests live under features/<name>/. Shared code lives in lib/ or components/ only when genuinely used by 3+ features. Folder names are domain-oriented when describing features, type-oriented when describing shared infrastructure. Every folder has a clear reason to exist — no empty utils/ waiting for content, no common/ overlapping with shared/ and lib/. Nesting rarely exceeds 3–4 levels inside features. Tests sit beside the code they test. A new engineer can guess a file's path from its purpose with 80%+ accuracy. Framework-magic folders (app/, pages/) hold only framework-shaped content.

Top-Level Hierarchy Checklist

• Count top-level folders; 5–10 is healthy, 15+ usually indicates accumulation without pruning — flag folders at the top level whose purpose isn't instantly clear from the name
• Identify top-level folders with overlapping or fuzzy purposes — lib/, utils/, helpers/, common/, shared/, core/, libs/; pick one canonical name for each purpose and consolidate
• Flag top-level folders that are empty, near-empty (1–2 files), or holding only a README.md and a placeholder — these usually aspire to organize content that never materialized
• Check for top-level folders named for technology rather than purpose (mongodb/, redis/, aws/) — infrastructure-aware grouping at the top level usually drifts and should be inside a purpose-oriented folder (lib/storage/)
• Verify that top-level names match conventions of the framework/ecosystem — Next.js apps expect app/ or pages/, Remix apps expect routes/, NestJS apps expect src/modules/; deviation should have a documented reason

Type-vs-Feature Organization Strategy Checklist

• Identify whether the codebase organizes by type (components/, hooks/, utils/, types/) or by feature (features/orders/, features/billing/) or hybrid; all are viable but the consistency matters more than the choice
• Flag hybrid organizations where features sometimes live under features/<name>/ and sometimes as a loose collection of files scattered in components/, hooks/, utils/; drift indicates the conventions aren't being followed and code lands wherever feels easiest
• Check for features fragmented across multiple type-folders (components/Order*, hooks/useOrder*, utils/order*); feature fragmentation is one of the strongest signals for moving to feature-folder organization
• Identify feature-folder implementations that hold too-narrow subdivisions (features/orders/components/, features/orders/hooks/, features/orders/types/, features/orders/utils/ when the feature has 8 total files); flatten when the feature is small
• Verify "shared" code truly is shared (≥3 features use it); shared folders that hold code used by only one feature are feature code masquerading as shared

Folder Size & Flat-File Density Checklist

• Flag folders with 25+ files at one level as needing sub-grouping; past this size, grep is the only reliable navigation and the structure has failed
• Identify folders with only 1–2 files that could collapse into their parent; excessive nesting is its own failure mode
• Check for components/ folders with 100+ flat files without grouping by feature, family, or size (components/ui/, components/forms/, components/charts/)
• Detect hooks folders with 40+ hooks undifferentiated by domain; group by feature or by category (data, state, DOM, effects)
• Verify that sub-groupings inside large folders follow a consistent scheme (all by domain, all by alphabetical prefix, all by UI family) rather than a mix

Co-location Checklist

• For a sampled feature (orders, auth, dashboard), trace every file modified in a recent feature change; count the number of distinct top-level folders touched — >3 usually signals fragmentation worth addressing
• Check whether feature-specific components sit beside their feature hooks, types, and tests; scattering these across global directories is one of the most common productivity drains
• Identify test files separated from their source by a parallel __tests__/ tree; co-located tests (Button.test.tsx next to Button.tsx) are usually better for discoverability and for keeping tests in sync with code
• Flag style files (CSS modules, styled-components) separated from their components; unless there's a specific reason (global design tokens), they belong beside the component
• Verify that feature-specific types (Order, OrderStatus, OrderLineItem) live in the feature folder, with only truly shared types (UserId, Money, DateRange) in a global types/ folder

Boundary & Public API Checklist

• Check whether each feature folder has a clear entry point (features/orders/index.ts) that exports the public API, or whether every internal file is reachable by deep imports from anywhere
• Flag features where "internal" files are imported by other features, bypassing the intended public API; this indicates the boundary isn't enforced and coupling is growing
• Identify cross-feature imports that should instead go through a shared module (e.g., features/billing/ importing from features/orders/lib/calculateTax.ts — if the tax calculation is shared, it should be in a shared location)
• Verify that shared libraries expose stable, minimal APIs; a lib/ module with 50 exports where only 3 are used externally suggests the boundary is too broad
• Detect deep imports (import { x } from 'features/orders/components/subdir/helper') that couple to internal structure; callers should import from the feature's root

Framework Convention Pollution Checklist

• In Next.js App Router, verify that app/ holds only route-shaped content: page.tsx, layout.tsx, route.ts, loading.tsx, error.tsx, not-found.tsx, and framework-expected metadata/sitemap files; flag random utilities, components, or types living inside app/
• In Next.js Pages Router, verify that pages/ holds only page components and api/ subfolder for API routes; non-page code should live elsewhere
• In React Native or Expo, verify that screens/ or app/ holds only screen-level components; smaller components, hooks, and utilities shouldn't mix in
• Flag component co-location inside framework folders (app/orders/components/OrderList.tsx); Next.js specifically supports private folders (_components/), and they should be used to signal "not a route"
• Identify files that accidentally get routed (a page.tsx in a folder meant to be non-routed) — framework-magic folders punish small mistakes

Naming Convention Checklist

• Check whether folder names use consistent casing — kebab-case and camelCase drift in the same codebase is common and creates import-path friction
• Flag folders whose names are too generic to describe their purpose — stuff/, misc/, various/, helpers/, temp/, backup/ (rename or delete)
• Identify folders where the name describes a technology rather than a purpose (firebase/, postgres/); rename to purpose (auth/, database/) with the technology as an implementation detail
• Verify file names match their export — a file exporting default function OrderList should be named OrderList.tsx, not orderList.tsx or order-list.tsx (unless the codebase convention is kebab-case consistently)
• Check for plurality consistency — components/ vs component/, hooks/ vs hook/ — pick one and apply everywhere; plural for folders holding multiple members is the safer default

File Name Precision Checklist

• Flag files named ambiguously — index.ts used everywhere such that grep returns 40 results; name non-public files specifically so grep finds them
• Identify files named after their implementation rather than their purpose (utils.ts, helpers.ts); rename by domain (dateFormatting.ts, currencyMath.ts) or by export name
• Check for files whose name and exports have drifted (userHelpers.ts that exports formatOrderTotal); rename or split
• Detect files whose name is a prefix of other files without a grouping folder (OrderList.tsx, OrderListRow.tsx, OrderListHeader.tsx, OrderListEmpty.tsx at one level); group into OrderList/ folder
• Verify test file naming matches the convention (foo.test.ts vs foo.spec.ts vs __tests__/foo.ts); drift here causes test runner misconfiguration

Depth & Nesting Checklist

• Flag folders nested 6+ levels deep; deep hierarchies are hard to navigate and usually indicate either genuine domain complexity (acceptable) or ceremony (problematic)
• Check whether each level of nesting is earned — a level that holds only one subfolder can be collapsed
• Identify "pass-through" folders (folders with one child folder and nothing else); collapse
• Verify that nesting uses the same axis consistently at each level (e.g., feature → concern → component), not alternating between axes arbitrarily
• Detect duplicate nesting paths across features (features/orders/components/forms/, features/customers/components/forms/) — if forms are consistent across features, consider a shared components/forms/ instead

Barrel File Hygiene Checklist

• Identify index.ts barrels that re-export 40+ modules; these add bundler work, make bundle analysis misleading, and hide which file actually defines a symbol
• Flag barrels that export a mix of public API and internal helpers; clean barrels should expose only the public surface
• Check for transitive re-exports (index.ts re-exports from a barrel which re-exports from another barrel); collapse where possible
• Verify that internal barrels (used only within a feature) genuinely provide value; sometimes deleting them and letting callers import specific files improves clarity
• Detect circular imports caused by barrel re-exports; barrels are a common cycle-introducing pattern because they widen the dependency surface

Test, Story, and Doc Co-location Checklist

• Check whether tests sit beside source files or in a parallel tree; co-location is typically better but the choice should be consistent across the repo
• Verify Storybook stories (if used) sit beside components, not in a separate stories/ tree
• Identify feature-level README.md or doc files — helpful for onboarding when features are complex and worth including in feature folders
• Flag orphaned README.md files in folders that have since been reorganized; the docs drift is its own problem
• Check whether ADRs, RFCs, or design docs live in a predictable place (docs/adr/, docs/rfc/) rather than scattered at the top level

Feature-Folder Fragmentation (Inverse) Checklist

• Identify micro-features — folders with 2–3 files — where the "feature" is too small to justify its own folder; absorb into a parent feature or shared location
• Flag duplication across features: 3+ features each implement their own formatDate or Button; promote to shared
• Check for "kitchen-sink feature folders" that have grown to 40+ files without sub-grouping; treat as a signal the feature is multiple features fused
• Detect features importing heavily from other features' internals; this coupling suggests either boundary issues or that the features should merge
• Verify feature-level lib/ and utils/ folders have content worth being isolated from shared libs; if only one feature uses them, fine; if three do, promote

Evidence rules: Every recommendation cites the directories and file counts involved and what a newcomer would fail to find. A proposed move lists the files and the imports affected. Framework conventions are cited when they constrain the layout.

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Calibration

Scale to codebase size. A 50-file project probably doesn't need feature folders. A 5,000-file project almost certainly does. Frameworks with strong conventions (Next.js, Remix, NestJS) should be respected; don't invent parallel structures. Migrating folder structure is expensive: every import breaks, git history gets harder to trace (use git mv), and team muscle memory resets. Only recommend restructuring when the productivity gain justifies the cost — usually when the structure is actively causing lost time, inconsistent file placement, or fragmented features. Partial, phased migrations are almost always better than big-bang restructures.

• Severity:

  • Critical — Framework convention pollution causing build/route bugs; feature fragmentation so severe that any change touches 8+ folders; folder hierarchy that reliably causes new files to land in the wrong place
  • High — Overlapping top-level folders (lib/utils/helpers/common), 100+ flat files in components/, generic names (stuff/, misc/) at any level, deep imports bypassing intended boundaries
  • Medium — Inconsistent casing, scattered tests, missing feature folders for a feature that would clearly benefit, barrel-file overuse
  • Low — Minor nesting inefficiencies, some drift in test file naming, a handful of oversized folders
  • Inverse (Over-Organized) — Micro-features, pass-through folders, speculative structure waiting for content

• Confidence ratings: Confirmed (folder sizes measured, features traced, imports analyzed), Likely (structure clearly suggests issues but solution depends on team preference), or Speculative (general principle).

• Anti-hallucination guard: Not every codebase needs feature folders. Small projects benefit from type-based folders. Don't recommend a feature-folder migration for a 200-file codebase where the current structure works. Don't recommend restructuring purely for aesthetics — every migration costs git history readability and team attention. If the current structure is imperfect but nobody is losing time to it, leave it alone.

Output Format

Start with a 3–5 line executive summary: overall structure health, strategy in use (type/feature/hybrid) and consistency, the single worst offender (fragmented feature, oversized folder, convention pollution), the single highest-leverage restructuring, and any over-organization noted.

1. Top-Level Folder Inventory Table

Folder	File Count	Purpose (stated)	Purpose (actual)	Issue	Severity

2. Organization Strategy Assessment — What strategy is in use, where it's applied consistently, where it drifts, and the recommended canonical approach

3. Feature Fragmentation Trace — For 2–3 sampled features, list every folder touched when the feature is changed, and propose consolidation

4. Folder Size & Sub-Grouping Findings — Folders that need internal structure, with specific sub-folder proposals

5. Co-location Findings — Tests, styles, types, stories that should sit beside source, with migration plans

6. Boundary & Public API Findings — Cross-feature deep imports, missing entry points, over-broad shared modules, with specific boundary proposals

7. Framework Convention Findings — Non-route content in framework folders, private-folder opportunities, routing drift

8. Naming Findings — Casing inconsistencies, generic names, file/export mismatches, with specific renames

9. Depth & Nesting Findings — Overly deep trees, pass-through folders, inconsistent axis choices

10. Barrel File Findings — Over-broad barrels, transitive re-exports, cycle risk, with trimming plans

11. Over-Organization / Inversion Findings — Micro-features, speculative folders, cross-feature duplication that should be shared

12. Migration Plan — Phased — If a restructure is recommended, sequence phases to minimize churn: start with high-leverage, low-risk moves; defer ambiguous reshufflings; use git mv to preserve history

13. Preserve — Structural Patterns Working Well — Parts of the organization that work and should be protected from subsequent "cleanups"

For each finding: folder-path, severity, confidence, the specific concrete restructure (which files move where, which folders merge or split, which names change), and the expected productivity benefit.