tRPC Scaffolder

Automate creation of type-safe tRPC endpoints with Zod validation.

TL;DR: Run scripts to create routers/schemas, register in _app.ts, validate with scripts.

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Auto-Triggers

Auto-triggered by keywords:

• "new endpoint", "create endpoint", "tRPC procedure"
• "new router", "API", "Zod schema"

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Quick Standards

File Locations

lib/trpc/routers/
  _app.ts          # Register all routers here ⚠️
  {name}.ts        # Router files

lib/trpc/schemas/
  {entity}.schema.ts  # Zod schemas

Router Pattern

export const nameRouter = router({
  doThing: publicProcedure
    .input(inputSchema)
    .output(outputSchema)
    .mutation(async ({ input }) => { /* logic */ }),
});

Schema Pattern

export const inputSchema = z.object({
  field: z.string().min(1),
});

export type Input = z.infer<typeof inputSchema>;  // ⚠️ Required!

Registration (Required!)

// In _app.ts
export const appRouter = router({
  ai: aiRouter,
  name: nameRouter,  // ⬅️ Add new routers here
});

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Run Scripts

Create Router

./.claude/skills/trpc-scaffolder/scripts/create-router.sh user
# Creates: lib/trpc/routers/user.ts
# ⚠️ Remember to register in _app.ts!

Add Procedure

./.claude/skills/trpc-scaffolder/scripts/add-procedure.sh ai getHints query
# Outputs code snippet to add to router

Create Schema

./.claude/skills/trpc-scaffolder/scripts/create-schema.sh hint
# Creates: lib/trpc/schemas/hint.schema.ts

Validate Setup

./.claude/skills/trpc-scaffolder/scripts/validate-trpc.sh
# Checks: router registration, type exports

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Quick Reference

Query vs Mutation

Type	Use For	Method
Query	Fetch data (GET)	.query(async ({ input }) => ...)
Mutation	Modify data (POST/PUT/DELETE)	.mutation(async ({ input }) => ...)

Common Zod Patterns

Type	Pattern	Example
String	z.string().min(1).max(100)	Name validation
Number	z.number().int().min(0).max(10)	Difficulty 0-10
Email	z.string().email()	Email validation
Optional	z.string().optional()	Optional field
Array	z.array(z.string()).min(1)	At least 1 item
Enum	z.enum(["a", "b", "c"])	Fixed choices
Object	z.object({ field: z.string() })	Nested object

Naming Conventions

• Routers: {domain}Router (e.g., aiRouter, userRouter)
• Procedures: camelCase (e.g., generateQuestions, getHints)
• Schemas: {action}{Entity}{Input\|Output}Schema
• Files: {entity}.schema.ts, {domain}.ts

Error Codes

Code	When	Example
NOT_FOUND	Resource doesn't exist	User not found
BAD_REQUEST	Invalid input	Validation failed
UNAUTHORIZED	Not authenticated	Login required
FORBIDDEN	Not authorized	Access denied
INTERNAL_SERVER_ERROR	Server error	API failure

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Common Fixes

Router Not Registered

// ❌ Forgot this step
// ✅ Add to _app.ts:
import { userRouter } from "./user";
export const appRouter = router({ ai: aiRouter, user: userRouter });

Missing Type Exports

// ❌ Schema without types
export const userSchema = z.object({ name: z.string() });

// ✅ Always export inferred types
export type User = z.infer<typeof userSchema>;

Wrong Procedure Type

// ❌ Using mutation for fetching data
getData: publicProcedure.mutation(...)

// ✅ Use query for GET operations
getData: publicProcedure.query(...)

Schema Validation Error

// ❌ No validation
field: z.string()

// ✅ Add constraints
field: z.string().min(1, "Field is required")

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When to Load Additional Docs

SKILL.md is self-sufficient for:

• Creating routers and schemas
• Running scripts
• Fixing common errors

Load additional docs when needed:

Need	Load
Step-by-step tutorial	docs/quick-start-guide.md
Advanced Zod patterns	docs/trpc-patterns.md (lines 1-80)
Error handling strategies	docs/trpc-patterns.md (lines 150-220)
Testing procedures	docs/trpc-patterns.md (lines 220-270)
Context & middleware	docs/trpc-patterns.md (lines 80-150)

Code examples:

• ✅ Perfect: examples/good-router.ts, examples/good-schema.ts

Full project docs: Docs/api-design.md, Docs/api-transition/trpc-migration.md

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Version: 1.0.0 | Updated: October 2025 Pattern: Follows quality-reviewer structure (optimized)