convex-core

---

name: convex-core description: |- Build Convex schemas, queries, mutations, actions, and client usage with strict validators and indexes. Use for data modeling, function authoring, argument/return validation, and performance guidance. Use proactively when work touches convex/schema.ts, functions, or api.* references.

Examples:

• user: "Design tables for multi-tenant app" → defineSchema/defineTable with indexes
• user: "Write a mutation" → args/returns validators + auth checks
• user: "Optimize query" → add index and withIndex range expression
• user: "Use useQuery" → show generated hook usage

---

Schema Rules

• You MUST define all tables in convex/schema.ts with defineSchema / defineTable.
• System Fields: _id (v.id(tableName)) and _creationTime (v.number()) are added automatically.
• You MUST use v.* validators for every field; SHOULD avoid v.any() unless necessary.
• Index naming: include all fields in the name, e.g., "by_field1_and_field2".
• Index rules:
  • You MUST use .index(name, [fields...]).
  • Field order matters; range expressions MUST follow index order.
  • Limits: 16 fields per index, 32 indexes per table.

Function Rules

• You MUST use new function syntax with args, returns, and handler.
• You MUST always validate args and returns (HTTP actions excluded).
• Use query for reads, mutation for writes, and action for external/long-running.
• Actions MUST NOT access ctx.db; You MUST use ctx.runQuery / ctx.runMutation.
• Circular Dependencies: When calling a function in the same file via ctx.run*, You MUST add explicit return type annotations to the receiver variable.

Database Operations

• You MUST provide the explicit table name as the first argument to ctx.db.get, ctx.db.patch, ctx.db.replace, and ctx.db.delete.
• Replacement: Use ctx.db.replace for full document replacement (throws if missing).
• Patching: Use ctx.db.patch for shallow merge updates (throws if missing).
• Deletion: Convex queries do NOT support .delete(). You MUST .collect() results and iterate to call ctx.db.delete(id).
• Unique: Use .unique() for single document results; it MUST throw if multiple documents match.
• You MUST NOT use filter in production queries; use indexes and .withIndex.

TypeScript Best Practices

• You MUST use as const for string literals in discriminated unions.
• You MUST define arrays as const array: Array<T> = [...] and records as const record: Record<K, V> = {...}.
• You MUST prefer Id<"table"> over string for all document identifiers.

Query Performance

• You SHOULD prefer .withIndex over .filter on large tables.
• If using .withIndex without a range, You MUST pair it with take, first, unique, or paginate.
• Search limits: collect() throws if >1024 docs; You SHOULD use take(n), paginate(), or for await iteration for large sets.
• Async iteration: Use for await (const row of query) instead of .collect() for streaming large result sets.

Pagination

• You MUST use paginationOptsValidator in args.
• .paginate() returns { page, isDone, continueCursor }.
• Pages are reactive; size MAY change.
• You SHOULD avoid strict returns validators for the full .paginate() result object; validate page or use v.any().

Client Patterns

• You MUST use api.* references from convex/_generated/api.
• React hooks: useQuery, useMutation, useAction, usePaginatedQuery.
• You MUST NOT call mutations or actions during render.

Safety

• You MUST enforce auth per function; check identity via ctx.auth helpers.
• You MUST NOT expose sensitive logic in public functions; MUST use internal ones.