aid: trpc-vocabulary
name: tRPC Vocabulary
description: >-
  Domain vocabulary for the tRPC TypeScript framework covering RPC concepts,
  type safety, procedure types, router composition, and the HTTP protocol
  tRPC uses for client-server communication.
created: '2026-05-03'
modified: '2026-05-03'
tags:
  - tRPC
  - TypeScript
  - RPC
  - API Framework

terms:
  - term: Procedure
    definition: >-
      A typed function on a tRPC router that can be a query, mutation,
      or subscription. Procedures are the primary building blocks of a
      tRPC API and are invoked by clients with full type safety.
    tags:
      - Core Concepts

  - term: Query
    definition: >-
      A tRPC procedure type for read-only operations. Queries map to HTTP
      GET requests and should not cause side effects. They support caching
      and request batching.
    tags:
      - Procedures

  - term: Mutation
    definition: >-
      A tRPC procedure type for write operations that cause side effects.
      Mutations map to HTTP POST requests. Examples include creating,
      updating, or deleting data.
    tags:
      - Procedures

  - term: Subscription
    definition: >-
      A tRPC procedure type for real-time, server-push updates. Subscriptions
      use WebSockets or Server-Sent Events for bidirectional streaming.
    tags:
      - Procedures
      - Real-Time

  - term: Router
    definition: >-
      A collection of related tRPC procedures grouped under a common
      namespace. Routers can be nested to create hierarchical API structures.
      The root router is the AppRouter exported from the server.
    tags:
      - Core Concepts

  - term: AppRouter
    definition: >-
      The root tRPC router exported from the server. The AppRouter type is
      imported on the client side as a type-only import to enable end-to-end
      type inference without runtime overhead.
    tags:
      - Core Concepts
      - Type Safety

  - term: initTRPC
    definition: >-
      The tRPC initialization function that creates the builder used to
      define routers and procedures. Called once per application with
      optional context and meta types.
    tags:
      - Core Concepts

  - term: Context
    definition: >-
      Per-request data passed to every tRPC procedure, typically including
      authentication state, database clients, and session information.
      Created via the createContext function in the server adapter.
    tags:
      - Core Concepts
      - Authentication

  - term: Middleware
    definition: >-
      A function that runs before a tRPC procedure and can modify the context,
      add authorization checks, or perform logging. Applied via `.use()` on
      a procedure builder.
    tags:
      - Middleware

  - term: Input Validation
    definition: >-
      tRPC uses Zod (or other validation libraries like Valibot, Yup) for
      schema-based input validation. Input validators are declared via
      `.input(schema)` on a procedure.
    tags:
      - Validation
      - Type Safety

  - term: httpBatchLink
    definition: >-
      A tRPC client link that automatically batches multiple concurrent
      procedure calls into a single HTTP request, reducing network overhead.
    tags:
      - Client
      - Performance

  - term: End-to-End Type Safety
    definition: >-
      The core tRPC value proposition: TypeScript types flow automatically
      from server procedure definitions to the client without code generation,
      providing compile-time safety for API contracts.
    tags:
      - Type Safety
      - Core Concepts

  - term: trpc-openapi
    definition: >-
      A community package (now archived) that adds OpenAPI/REST endpoint
      support to tRPC procedures via metadata annotations. Succeeded by
      trpc-to-openapi for active maintenance.
    tags:
      - OpenAPI
      - REST

  - term: Adapter
    definition: >-
      A tRPC server integration layer that connects tRPC to a specific HTTP
      framework (Express, Fastify, Next.js, AWS Lambda, Fetch/Edge runtimes).
    tags:
      - Adapters
      - Server

  - term: TRPCError
    definition: >-
      The error class used to throw typed errors from tRPC procedures. Accepts
      a code (UNAUTHORIZED, NOT_FOUND, etc.) and message, automatically mapping
      to the appropriate HTTP status code.
    tags:
      - Error Handling