sim/CLAUDE.md

Sim Studio Development Guidelines

You are a professional software engineer. All code must follow best practices: accurate, readable, clean, and efficient.

Global Standards

• Logging: Import createLogger from @sim/logger. Use logger.info, logger.warn, logger.error instead of console.log
• Comments: Use TSDoc for documentation. No ==== separators. No non-TSDoc comments
• Styling: Never update global styles. Keep all styling local to components
• Package Manager: Use bun and bunx, not npm and npx

Architecture

Core Principles

1. Single Responsibility: Each component, hook, store has one clear purpose
2. Composition Over Complexity: Break down complex logic into smaller pieces
3. Type Safety First: TypeScript interfaces for all props, state, return types
4. Predictable State: Zustand for global state, useState for UI-only concerns

Root Structure

apps/sim/
├── app/           # Next.js app router (pages, API routes)
├── blocks/        # Block definitions and registry
├── components/    # Shared UI (emcn/, ui/)
├── executor/      # Workflow execution engine
├── hooks/         # Shared hooks (queries/, selectors/)
├── lib/           # App-wide utilities
├── providers/     # LLM provider integrations
├── stores/        # Zustand stores
├── tools/         # Tool definitions
└── triggers/      # Trigger definitions

Naming Conventions

• Components: PascalCase (WorkflowList)
• Hooks: use prefix (useWorkflowOperations)
• Files: kebab-case (workflow-list.tsx)
• Stores: stores/feature/store.ts
• Constants: SCREAMING_SNAKE_CASE
• Interfaces: PascalCase with suffix (WorkflowListProps)

Imports

Always use absolute imports. Never use relative imports.

// ✓ Good
import { useWorkflowStore } from '@/stores/workflows/store'

// ✗ Bad
import { useWorkflowStore } from '../../../stores/workflows/store'

Use barrel exports (index.ts) when a folder has 3+ exports. Do not re-export from non-barrel files; import directly from the source.

Import Order

1. React/core libraries
2. External libraries
3. UI components (@/components/emcn, @/components/ui)
4. Utilities (@/lib/...)
5. Stores (@/stores/...)
6. Feature imports
7. CSS imports

Use import type { X } for type-only imports.

TypeScript

1. No any - Use proper types or unknown with type guards
2. Always define props interface for components
3. as const for constant objects/arrays
4. Explicit ref types: useRef<HTMLDivElement>(null)

Components

'use client' // Only if using hooks

const CONFIG = { SPACING: 8 } as const

interface ComponentProps {
  requiredProp: string
  optionalProp?: boolean
}

export function Component({ requiredProp, optionalProp = false }: ComponentProps) {
  // Order: refs → external hooks → store hooks → custom hooks → state → useMemo → useCallback → useEffect → return
}

Extract when: 50+ lines, used in 2+ files, or has own state/logic. Keep inline when: < 10 lines, single use, purely presentational.

Hooks

interface UseFeatureProps { id: string }

export function useFeature({ id }: UseFeatureProps) {
  const idRef = useRef(id)
  const [data, setData] = useState<Data | null>(null)
  
  useEffect(() => { idRef.current = id }, [id])
  
  const fetchData = useCallback(async () => { ... }, []) // Empty deps when using refs
  
  return { data, fetchData }
}

Zustand Stores

Stores live in stores/. Complex stores split into store.ts + types.ts.

import { create } from 'zustand'
import { devtools } from 'zustand/middleware'

const initialState = { items: [] as Item[] }

export const useFeatureStore = create<FeatureState>()(
  devtools(
    (set, get) => ({
      ...initialState,
      setItems: (items) => set({ items }),
      reset: () => set(initialState),
    }),
    { name: 'feature-store' }
  )
)

Use devtools middleware. Use persist only when data should survive reload with partialize to persist only necessary state.

React Query

All React Query hooks live in hooks/queries/.

export const entityKeys = {
  all: ['entity'] as const,
  list: (workspaceId?: string) => [...entityKeys.all, 'list', workspaceId ?? ''] as const,
}

export function useEntityList(workspaceId?: string) {
  return useQuery({
    queryKey: entityKeys.list(workspaceId),
    queryFn: () => fetchEntities(workspaceId as string),
    enabled: Boolean(workspaceId),
    staleTime: 60 * 1000,
    placeholderData: keepPreviousData,
  })
}

Styling

Use Tailwind only, no inline styles. Use cn() from @/lib/utils for conditional classes.

<div className={cn('base-classes', isActive && 'active-classes')} />

EMCN Components

Import from @/components/emcn, never from subpaths (except CSS files). Use CVA when 2+ variants exist.

Testing

Use Vitest. Test files: feature.ts → feature.test.ts

/**
 * @vitest-environment node
 */

// Mocks BEFORE imports
vi.mock('@sim/db', () => ({ db: { select: vi.fn() } }))

// Imports AFTER mocks
import { describe, expect, it, vi } from 'vitest'
import { createSession, loggerMock } from '@sim/testing'

describe('feature', () => {
  beforeEach(() => vi.clearAllMocks())
  it.concurrent('runs in parallel', () => { ... })
})

Use @sim/testing factories over manual test data.

Utils Rules

• Never create utils.ts for single consumer - inline it
• Create utils.ts when 2+ files need the same helper
• Check existing sources in lib/ before duplicating

Adding Integrations

New integrations require: Tools → Block → Icon → (optional) Trigger

Always look up the service's API docs first.

1. Tools (tools/{service}/)

tools/{service}/
├── index.ts      # Barrel export
├── types.ts      # Params/response types
└── {action}.ts   # Tool implementation

Tool structure:

export const serviceTool: ToolConfig<Params, Response> = {
  id: 'service_action',
  name: 'Service Action',
  description: '...',
  version: '1.0.0',
  oauth: { required: true, provider: 'service' },
  params: { /* ... */ },
  request: { url: '/api/tools/service/action', method: 'POST', ... },
  transformResponse: async (response) => { /* ... */ },
  outputs: { /* ... */ },
}

Register in tools/registry.ts.

2. Block (blocks/blocks/{service}.ts)

export const ServiceBlock: BlockConfig = {
  type: 'service',
  name: 'Service',
  description: '...',
  category: 'tools',
  bgColor: '#hexcolor',
  icon: ServiceIcon,
  subBlocks: [ /* see SubBlock Properties */ ],
  tools: { access: ['service_action'], config: { tool: (p) => `service_${p.operation}` } },
  inputs: { /* ... */ },
  outputs: { /* ... */ },
}

Register in blocks/registry.ts (alphabetically).

SubBlock Properties:

{
  id: 'field', title: 'Label', type: 'short-input', placeholder: '...',
  required: true,                    // or condition object
  condition: { field: 'op', value: 'send' },  // show/hide
  dependsOn: ['credential'],         // clear when dep changes
  mode: 'basic',                     // 'basic' | 'advanced' | 'both' | 'trigger'
}

condition examples:

• { field: 'op', value: 'send' } - show when op === 'send'
• { field: 'op', value: ['a','b'] } - show when op is 'a' OR 'b'
• { field: 'op', value: 'x', not: true } - show when op !== 'x'
• { field: 'op', value: 'x', not: true, and: { field: 'type', value: 'dm', not: true } } - complex

dependsOn: ['field'] or { all: ['a'], any: ['b', 'c'] }

3. Icon (components/icons.tsx)

export function ServiceIcon(props: SVGProps<SVGSVGElement>) {
  return <svg {...props}>/* SVG from brand assets */</svg>
}

4. Trigger (triggers/{service}/) - Optional

triggers/{service}/
├── index.ts      # Barrel export
├── webhook.ts    # Webhook handler
└── {event}.ts    # Event-specific handlers

Register in triggers/registry.ts.

Integration Checklist

• Look up API docs
• Create tools/{service}/ with types and tools
• Register tools in tools/registry.ts
• Add icon to components/icons.tsx
• Create block in blocks/blocks/{service}.ts
• Register block in blocks/registry.ts
• (Optional) Create and register triggers