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Mental Model

• Components are isolated mini backends with their own schema, tables, file storage, and functions.
• Components MUST NOT access app tables/functions/env unless passed explicitly.
• Calls into components are transactional with the caller, but component mutations are sub-transactions.

Installing Components

• Install package: npm i @convex-dev/<component>.
• Add convex/convex.config.ts:
  • import { defineApp } from "convex/server";
  • app.use(component); use app.use(component, { name: "custom" }) for multiple instances.
• You MUST run npx convex dev to generate component code.
• Access via components.<name> in convex/_generated/api.

Calling Component APIs

• Use ctx.runQuery/Mutation/Action with components.<name>.<fn>.
• Public component functions MUST NOT be called directly from clients (they are internal references).
• Queries remain reactive; mutations are transactional.

Transaction Semantics

• Top-level mutation commits all writes across components together.
• If a component mutation throws, only its writes are rolled back; the caller MAY catch and continue.

Component API Differences

• components.<name> exposes ONLY public component functions.
• Id types cross boundaries as string; You MUST NOT use v.id("table") for external tables.
• Each component has its own _generated directory; You MUST use the app's components references.

Environment Variables

• Components MUST NOT access process.env directly.
• You MUST pass env values as arguments from the app, or store config in a component table.

HTTP Actions

• Components MUST NOT expose routes directly; app MUST mount handlers in convex/http.ts.

Auth in Components

• ctx.auth is NOT available inside component functions.
• You MUST authenticate in the app and pass identifiers (userId) to component functions.

Pagination

• Built-in .paginate() is NOT supported inside components.
• You SHOULD use convex-helpers paginator and usePaginatedQuery from convex-helpers if needed.

Authoring Components

• Component folder MUST include convex.config.ts, schema.ts, functions, and _generated.
• defineComponent("name") defines component; use component.use(...) for child components.
• Local components MAY live in convex/components/ or any folder.
• NPM components SHOULD export:
  • @pkg/convex.config.js
  • @pkg/_generated/component.js
  • @pkg/test helpers

Function Handles

• You SHOULD use createFunctionHandle(api.foo.bar) to pass callbacks across boundaries.
• Handles are strings; use v.string() validators and cast back to FunctionHandle.

Testing Components

• You SHOULD register component with convex-test using component schema/modules or provided test helpers.
• For component packages, You SHOULD use @pkg/test register helper.

Best Practices

• You MUST always validate args/returns on public component functions.
• You SHOULD prefer app-level wrappers to add auth/rate limiting when re-exporting component APIs.
• You SHOULD use a single-row globals/config table for static configuration.