Best practices for building and maintaining applications with PowerSync: Cloud and self-hosted setup, sync configuration, client SDK usage, backend integration (Supabase, custom Postgres, MongoDB, Azure DocumentDB, MySQL, MSSQL), schema changes, watch and reactive queries (useQuery), attachments, th

PowerSync Skills Use this skill to onboard a project onto PowerSync and to keep it healthy afterwards, without trial and error. Treat this as a guided workflow first and a reference library second. Agents: Read [AGENTS.md](AGENTS.md) before proceeding. It contains the mandatory compliance rules and onboarding playbook. The Quick Rules below are a reminder, not a substitute. powersync login is PowerSync Cloud only (PAT); self hosted does not use it. Terminology Operator — the human directing this agent (whose request you are fulfilling). User — an end user of the operator's PowerSync app (JWT subjects, the row a sync stream filters by, the person calling disconnectAndClear() ). If a sentence is ambiguous, default to the operator interpretation. Full legend in AGENTS.md . Quick Rules CLI first. Use the [PowerSync CLI](https://docs.powersync.com/tools/cli.md) for all operations. Do not hand write config files. See references/powersync cli.md . Ask, don't assume. Ask the operator: Cloud vs self hosted, and which backend (Supabase, Postgres, MongoDB, Azure DocumentDB, MySQL, MSSQL). Do not default to Supabase. Backend before frontend. Deploy sync config and verify the service before writing app code. Sync Streams for new projects. Sync Rules are legacy. Keep credentials in .env , never hardcoded. Record URLs and keys in .env as they become available; config ( !env ) and app code read from there. Default scope on existing projects: sync config only. Do not edit service.yaml or cli.yaml unless the operator explicitly authorized service/infra changes in this conversation. Confirm the target instance before any mutating command ( deploy , destroy , stop , link create , pull instance ). Never deploy to an instance not authorized by the operator. Treat production as off limits unless explicitly approved. Use project memory. If your harness supports it, persist the CLI invocation, sync config path, authorized instance ids + environment (dev/staging/prod), and allowed scope of changes. Verify saved values still match reality before acting on them. See AGENTS.md § "Continuous Use & Guardrails". First Use in a Repo: Offer to Trim (agents) This copy ships reference files for every PowerSync platform. On your first use of this skill in a repo, check for .trim state.json next to this file. If it exists, the operator already decided; skip this section. Otherwise run node scripts/trim.mjs from this skill's directory. The default run is a read only report: it detects which PowerSync platforms this repo uses and lists the reference files this copy does not need. It works on this installed copy only, makes no network requests, and is reversible by reinstalling the skill. If it refuses (shared or source install) or detects no PowerSync usage yet, skip this section silently. Otherwise show the report to the operator and ask whether to trim this installed copy. Never trim without explicit operator approval. Operator approves: run node scripts/trim.mjs apply (add keep <platforms for platforms the operator wants to keep anyway). Operator declines: run node scripts/trim.mjs decline so the operator is not asked again. Reinstalling or npx skills update restores the full copy and clears the recorded decision; offering again after an update is expected. What to Load for Your Task Task Start with Load on demand Supabase + PowerSync references/onboarding supabase.md references/supabase auth.md , references/sync config.md , SDK files Custom backend (non Supabase) references/onboarding custom.md references/custom backend.md , references/sync config.md , SDK files New project setup references/powersync cli.md + references/powersync service.md references/sync config.md , SDK files Migrating from Electric Cloud references/migration from electric.md references/sync config.md , SDK files Self hosting / service config references/powersync service.md + references/powersync cli.md references/sync config.md Terraform / IaC provisioning references/terraform.md references/sync config.md , references/supabase auth.md (if Supabase source) Writing sync config references/sync config.md — Debugging sync issues references/powersync debug.md — Raw Tables (advanced) references/raw tables.md — Attachments references/attachments.md — Architecture overview references/powersync overview.md — SQLite extensions (vector search, FTS5, custom tokenizers) references/sqlite extensions.md — SDK Reference Files JavaScript / TypeScript Always load references/sdks/powersync js.md for any JS/TS project, then load the applicable framework file. Framework File Load early if… React / Next.js references/sdks/powersync js react.md Vite + React project — contains the required vite.config.ts setup ( optimizeDeps.exclude , worker.format: 'es' ) needed before installing packages React Native / Expo references/sdks/powersync js react native.md Vue / Nuxt references/sdks/powersync js vue.md Node.js / Electron references/sdks/powersync js node.md TanStack references/sdks/powersync js tanstack.md Drizzle / Kysely ORM references/sdks/powersync js orm.md Project uses Drizzle or Kysely Other SDKs Platform File Dart / Flutter references/sdks/powersync dart.md .NET references/sdks/powersync dotnet.md Kotlin references/sdks/powersync kotlin.md Swift references/sdks/powersync swift.md Key Rules to Apply Without Being Asked Never define the id column in a PowerSync table schema; it is created automatically. Use column.integer for booleans and column.text for ISO date strings. connect() is fire and forget. Use waitForFirstSync() if you need readiness. Call .connect() once per session. Do not call it again on window focus events, token refreshes, or network changes; redundant calls open additional sync connections. transaction.complete() is mandatory or the upload queue stalls permanently. On user sign out, use disconnectAndClear() when another user may access the device or security requires wiping local data. If the same user will return to their own device and retaining local data is safe, use disconnect() instead. The client resumes from its saved sync position rather than re downloading everything. Never retain one user's data for a different user. A 4xx response from uploadData blocks the upload queue permanently; return 2xx for validation errors.