Organizing code around “features” (sometimes called a “feature-slice” or “modular monolith” layout) pairs naturally with barrel files (`index.ts`).  Here’s a pragmatic way to adopt it incrementally:

────────────────────────────────────────
1. Folder structure per feature/tab
────────────────────────────────────────
```
frontend/src/
└─ features/
   ├─ portfolio/
   │   ├─ hooks/
   │   │   ├─ usePortfolioList.ts
   │   │   ├─ usePortfolioMutations.ts
   │   │   └─ index.ts          ← barrel (re-exports hooks)
   │   ├─ adapters/
   │   │   ├─ RiskScoreAdapter.ts
   │   │   └─ index.ts
   │   ├─ services/             ← wrappers around APIService if any
   │   ├─ components/
   │   │   ├─ PortfolioList.tsx
   │   │   ├─ EditPortfolioModal.tsx
   │   │   └─ index.ts
   │   ├─ state/                ← Zustand slice or Redux slice (optional)
   │   └─ index.ts              ← *feature* barrel (re-exports public API)
   ├─ risk/
   │   ├─ hooks/
   │   ├─ adapters/
   │   ├─ components/
   │   └─ index.ts
   └─ auth/
       └─ …
```

Rules  
• Everything *only* that portfolio/risk/ui feature needs lives inside that folder.  
• Cross-feature utilities stay in `src/lib/` or `src/shared/`.

────────────────────────────────────────
2. Barrel files: public surface
────────────────────────────────────────
`features/portfolio/index.ts`
```ts
export * from './hooks';
export * from './components';
export { PortfolioRepository } from '../../repository/PortfolioRepository';
```
Now consumers import from a single path:
```ts
import { usePortfolioList, PortfolioList } from 'features/portfolio';
```

Benefits  
1. Clear **boundaries** – feature internals aren’t imported elsewhere unless exported in the barrel.  
2. Faster refactors – move a file inside the feature without breaking imports.  
3. Auto-tree-shaking – bundlers drop any feature the route tree doesn’t hit.

────────────────────────────────────────
3. Incremental migration plan
────────────────────────────────────────
Phase 1: New feature code only  
   • Place all CRUD work (hooks, components, manager wrappers) into `features/portfolio/…` right away.  
   • Export a minimal barrel.

Phase 2: Move adapters & hooks already created  
   • Relocate `RiskScoreAdapter`, `useRiskAnalysis`, etc. into `features/risk/…`.  
   • Update import paths (barrel makes that only a couple lines).

Phase 3: Providers / cache / repository  
   • “Infrastructure” (PortfolioRepository, PortfolioCacheService) can stay where they are (`chassis/`, `repository/`).  
   • Feature folders *import* those—but don’t expose them publicly unless truly needed.

Phase 4: Delete old duplicate barrels  
   • When everything for “portfolio” lives under `features/portfolio`, remove the old `src/hooks/usePortfolioFlow.ts`, etc.

────────────────────────────────────────
4. Tips for smooth adoption
────────────────────────────────────────
• Keep a **lint rule** (`no-restricted-imports`) so code outside `features/portfolio` cannot deep-import `../../hooks/usePortfolioList`. They must go through the barrel.  
• Document each feature’s *public API* in its barrel comment—makes code review easy.  
• If two features need the same adapter/util, extract it to `src/shared/` and barrel it there.

────────────────────────────────────────
5. Example: creating the CRUD barrel first
────────────────────────────────────────
`features/portfolio/hooks/index.ts`
```ts
export { usePortfolioList } from './usePortfolioList';
export { usePortfolioMutations } from './usePortfolioMutations';
```
`features/portfolio/components/index.ts`
```ts
export { PortfolioList } from './PortfolioList';
export { EditPortfolioModal } from './EditPortfolioModal';
```
`features/portfolio/index.ts` (feature barrel)
```ts
export * from './hooks';
export * from './components';
```

Your **App** or **router** then imports:
```ts
import { PortfolioList } from 'features/portfolio';
```

────────────────────────────────────────
Bottom-line recommendation
────────────────────────────────────────
1. Start the new CRUD work **inside a `features/portfolio` folder** right away.  
2. Move related existing hooks/adapters there gradually.  
3. Introduce barrel files (`index.ts`) at each folder level to expose only the intended public surface.  
4. Use ESLint to prevent reach-through imports, keeping feature boundaries clean.

That gives you an organised, discoverable codebase without a disruptive big-bang refactor.

________________________________________

Here’s a lightweight next-step checklist you can tackle whenever you’re ready:

1. Skeleton folders  
   • `frontend/src/features/portfolio/`  
     – `components/`, `hooks/`, `adapters/`, `services/`, `state/` (optional)  

2. Initial barrel files (empty exports are fine for now)  
   ```
   features/portfolio/hooks/index.ts
   features/portfolio/components/index.ts
   features/portfolio/index.ts
   ```

3. Start new CRUD work (list / add / edit / delete portfolios) inside those folders.  
   – Put the first hook (`usePortfolioList.ts`) and component (`PortfolioList.tsx`) in place and export them through the barrels.

4. Add an ESLint guard (optional but recommended)  
   – `no-restricted-imports` rule that bans deep imports such as `../../hooks/usePortfolioList` from outside the feature; enforce `import { … } from 'features/portfolio'` instead.

5. Migrate existing pieces only when you touch them anyway.  
   – e.g. next time you edit `RiskScoreAdapter`, move it to `features/risk/adapters/` and update its imports.

Doing those small steps keeps the repo stable while nudging everything toward the new structure. Let me know whenever you want to generate the folders/barrels or move any files—I can script it quickly.