grit sync — multi-surface

With four frontends, type drift is the silent killer. Web thinks price is a number; mobile thinks it's a string; desktop forgot to update after the API renamed it. Cue the production bug. grit sync exists to kill that whole category.

One Go model, four frontends

The Go model is the source of truth

package models

import "time"

type Product struct {
  ID         uint      `gorm:"primaryKey" json:"id"`
  Name       string    `gorm:"not null"   json:"name"`
  Slug       string    `gorm:"uniqueIndex" json:"slug"`
  PriceCents int       `gorm:"not null"   json:"price_cents"`
  Currency   string    `gorm:"default:USD" json:"currency"`
  InStock    bool      `json:"in_stock"`
  Tags       string    `gorm:"type:text" json:"tags"`  // CSV
  CreatedAt  time.Time `json:"created_at"`
  UpdatedAt  time.Time `json:"updated_at"`
}

Run grit sync

grit sync
# scans apps/api/internal/models/*.go
# writes packages/shared/types/*.ts
# writes packages/shared/zod/*.ts

What gets generated

// Generated by grit sync. Do not edit.
export interface Product {
  id: number
  name: string
  slug: string
  price_cents: number
  currency: string
  in_stock: boolean
  tags: string
  created_at: string
  updated_at: string
}

export interface CreateProductInput {
  name: string
  slug: string
  price_cents: number
  currency?: string
  in_stock?: boolean
  tags?: string
}

Notice: CreateProductInput drops the server-managed fields (ID, timestamps) and makes defaulted-fields optional. That's what you POST to /api/products.

The naming rule — snake vs. camel

Go convention is PriceCents; JSON convention is price_cents. The TS file mirrors the JSON tag, NOT the Go field name, because that's what comes off the wire.

If you prefer camelCase on the frontend, change the JSON tag in Go: json:"priceCents". The frontend type will update next sync. Pick one and stay consistent.

Add the field once — all frontends gain it

Suppose marketing asks for a Featured badge. Steps:

1. Add IsFeatured bool to the Go struct.
2. grit sync.
3. Web, admin, mobile, desktop — all four IDEs now show the field.
4. Run a DB migration (grit generates one too) so the column exists.

Five seconds of typing, zero copies, zero drift.

What sync does NOT do

• Doesn't generate API client code. The shared package gives you the types; each surface still calls fetch (web/admin/desktop) or the mobile API wrapper. Types make the calls safe, not automatic.
• Doesn't touch your existing UI. Add a field, the type changes; whether the UI shows it is on you. TS will flag where you destructure the type but ignore the new field as a soft warning if you enable it.
• Doesn't roll back a deleted Go field. Remove a field in Go, sync, and the TS shape becomes narrower. Any code referencing the old field now type-errors — which is the point.

What's next

Next lesson — Shared Zod schemas. Types tell you what shape data has; Zod validates that the runtime data actually matches that shape. Both sides of the input boundary.