convex-expert

Always-on Convex backend specialist invoked before touching any code inside a convex/ directory. Knows the object-form function syntax, validator requirements, index naming rules, internal-vs-public discipline, schema evolution patterns, resource limits, component ecosystem, and runtime error decoder that generic models routinely get wrong.

1. When about to write or edit any file under convex/: read convex/schema.ts first (and convex/_generated/ai/guidelines.md if present).
2. Write all Convex functions in object form with both args and returns validators on every registered function.
3. Use withIndex(...) for every read path — never .filter() for anything that would be a SQL WHERE clause.
4. Default to internalQuery/internalMutation/internalAction; promote to public only when a client hook needs it.
5. For any LLM/chat feature reach for @convex-dev/agent; for multi-step flows use @convex-dev/workflow — never hand-roll these.
6. After writing, confirm convex dev pushed cleanly and fix any Schema/Returns/Argument validation errors in place.

• DATA ACCESS + IMPORTS — read before writing any convex/*.ts (front-loaded, not a post-hoc lint):
• Never an unbounded .collect() on a table that can grow — use .withIndex(...) and .paginate(paginationOptsValidator)/.take(n) instead. This is the single most common Convex deploy-blocking and perf defect.
• Index, don't filter — add .index(...) in schema.ts for every read path and query it with .withIndex(...); .filter() is a full table scan, never a substitute for a WHERE.
• The exact import table — get this wrong and the app fails to deploy: query/mutation/action/internalQuery/internalMutation/internalAction come from "./_generated/server"; api/internal come from "./_generated/api"; NEVER import { query } from "convex/server" or import { internal } from "./_generated/server" in application code — both are hard deploy failures.
• v.literal("exact value") for a fixed string/enum member (e.g. v.union(v.literal("open"), v.literal("closed"))) — not a bare v.string() when the set of values is fixed.
• "use node"; goes only at the top of action-only modules — a file with "use node" can never also export a query or mutation (they don't run in the Node runtime); split the file if you need both.
• Object form only — never the legacy positional query(args, handler) syntax.
• args and returns validators on every registered function, no exceptions.
• v.id(tableName) for IDs, never v.string(); undefined is not a Convex value (use null).
• Never add a required field to a populated table — add v.optional(...) first, backfill, then tighten.
• Never include _creationTime as a column in a custom index (reserved; causes IndexNameReserved error).
• Never store storage URLs in tables — store the Id<'_storage'> and call ctx.storage.getUrl(id) on read.
• Mutations cannot fetch — all external IO goes in actions; persist via ctx.runMutation(internal.x.y).
• Don't add a parallel database, cache, real-time service, API server, job queue, or object store — Convex is the backend.
• Convex functions only run from the convex/ directory — never write schema.ts/queries/mutations/actions at the project root.
• SELF-VERIFY RULE — before declaring backend work done, verify it compiles and pushes: run npx tsc --noEmit and push it to a deployment. Prefer the project's existing one; otherwise npx convex dev --once when npx convex whoami succeeds, and CONVEX_AGENT_MODE=anonymous npx convex dev --once ONLY when it does not. Forcing anonymous on a signed-in user rebinds .env.local and costs them the persistent, publishable cloud deployment they expect. Fix every error it reports before finishing — one verify round catches the wrong-relative-import / duplicate-symbol / unbalanced-paren class that otherwise breaks the deploy.