| name | development |
| description | Develop new features, functionality, and enhancements. Use when creating, adding, building, implementing new features, components, endpoints, pages, or modules. Also trigger when user asks to add functionality, create a form, implement a filter, build a new UI section, or add an API endpoint. |
| allowed-tools | Read, Write, Bash, Grep, Glob |
| model | sonnet |
| user-invocable | true |
Feature Development
Build features methodically. Check first, build second.
Pre-Action (before writing any code)
1. Duplicate Check
Search semantically, grep, and file search. If similar functionality exists, extend it instead of creating a duplicate. Duplicates create maintenance burden — when the original changes, the copy becomes a silent source of bugs.
2. JTBD Analysis (for user-facing features)
Job Story: When [context], user wants [action], to get [result]
Three questions before coding:
- What task is the user actually solving?
- What is blocking them right now?
- How will they know the job is done?
This prevents building features nobody uses because the feature solves the wrong problem.
3. Find Working Example
For UI: find a working pattern in the project first. Copy the pattern, then adapt. Inventing CSS class combinations from scratch leads to inconsistent UI and wasted debugging time.
4. Control File Size
Plan logic across multiple files before starting. Soft limits: routes 300 lines, services 400, components 200. Large files become hard to review and often hide multiple responsibilities.
Backend Pattern
module.types.ts -> module.repository.ts -> module.service.ts -> module.routes.ts
Types define the contract. Repository handles DB. Service contains business logic. Routes wire HTTP to services. This separation exists so changes to DB queries don't require touching HTTP handlers.
Frontend Pattern
- App Router for pages (
apps/web/app/)
- Feature components (
apps/web/features/)
- Tailwind CSS v4 (no responsive prefixes like
md:)
- shadcn/ui components, KtCard wrapper
Common Pitfalls
- UI patterns: Always find a working example in the project first. Don't guess CSS classes.
- Types: Database bigint returns as JSON string. Always
Number() in code.
- External APIs: List/Enum fields may contain IDs, not text. Check field mapping.
- Entry points: Use high-level orchestrator services (
*SummaryService.syncDay()), not low-level methods.
Verification
- 0 linter errors
- Tests pass (if tests exist)
- JTBD job is fulfilled
- All changed files opened and verified
- If deploying: service restarted after build
