# convex-migrations

Walks a live Convex schema change through six steps: optional field, batched backfill, validator flip, cleanup. Useful when npx convex dev rejects existing documents.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 2600 installs · ★ 405
- Author: waynesutton
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/waynesutton/builder-skills/tree/HEAD/skills/convex-migrations/SKILL.md
- Updated: 2026-09-28
- HTML: https://affpapa.org/en/nevibecode/skills/convex-migrations

## What it does

Convex keeps no migration files and has no `migrate` command. `npx convex dev` pushes the schema and validates every existing document against it, but it never transforms your data. The skill enforces one rule: the schema describes the documents that exist right now, not the ones you want. Change the data first, tighten the validator second.

The sequence has six steps: mark the field `v.optional` in `convex/schema.ts`, deploy, update readers and writers, backfill existing documents in batches, flip the validator to its final shape, deploy again. Steps 1 and 2 must ship before the backfill starts, otherwise new writes keep arriving in the old shape while it runs. The skill ships a hand-rolled `internalMutation` that pages with `paginate`, patches only documents that still need it, and reschedules itself with the continue cursor. Each batch is its own transaction, so a large table never hits the per-function limit. Kick it off with `npx convex run migrations:backfillAvatarUrl '{"cursor": null}'`.

Once a project runs more than one or two migrations, the skill points to the `@convex-dev/migrations` component: persisted progress per migration, status checks, dry runs, cancel, and ordered runs. A one-off backfill on a small table does not need it. Whatever you do, don't pass `{ schemaValidation: false }` to `defineSchema` to force a push through — that hides the mismatch and moves the failure into your queries.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add waynesutton/builder-skills --skill convex-migrations -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/convex-migrations/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/convex-migrations/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add waynesutton/builder-skills --skill convex-migrations -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/convex-migrations/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add waynesutton/builder-skills --skill convex-migrations -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/convex-migrations/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install waynesutton/builder-skills convex-migrations
```

2. **Manually: put the files in place**
- File: `.github/skills/convex-migrations/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add waynesutton/builder-skills --skill convex-migrations -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/waynesutton/builder-skills --path skills/convex-migrations
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/convex-migrations/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add waynesutton/builder-skills --skill convex-migrations -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/waynesutton/builder-skills/tree/HEAD/skills/convex-migrations/SKILL.md

## When to use it
- add a required field to a table that already has rows
- rename a field or change its type without breaking the deploy
- split one table into two or merge two into one
- fix `Schema validation failed` after a schema edit
- backfill more rows than a single mutation can handle

## Example prompts
- Rename the `avatarUrl` field to `imageUrl` on the `users` table without downtime
- \`npx convex dev` fails with `Schema validation failed` on `users` — read the error and write the migration
- Set up `@convex-dev/migrations` and dry-run a backfill for the `role` field

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 6616c59f41c94977.

BEGIN THIRD-PARTY FILE 6616c59f41c94977
```text
---
name: convex-migrations
description: Changes a live Convex schema without downtime: make a field optional, backfill in batches, flip the validator, then clean up. Uses the @convex-dev/migrations component where it fits. Use when renaming or removing a field, changing a type, splitting a table, or when deploy fails with a schema validation error on existing documents.
---

# Convex migrations

Produces a schema change plus a batched backfill that keeps every deploy green. The one rule: the schema must describe the documents that exist right now, not the documents you want. Change the data first, then tighten the validator.

Convex has no migration files or `migrate` command. `npx convex dev` pushes the schema and validates every existing document against it. Existing data is never transformed for you.

## When to reach for this

- Adding a field that should be required, but the table already has rows
- Renaming a field, changing its type, or removing it
- Splitting one table into two or merging two into one
- `npx convex dev` fails with `Schema validation failed` after a schema edit
- A backfill needs to touch more rows than one mutation can handle

For step by step recipes (rename, change type, split, merge, add required, remove) open [references/migration-patterns.md](references/migration-patterns.md). For installing and running `@convex-dev/migrations` open [references/migrations-component.md](references/migrations-component.md).

## The safe sequence

Every migration follows the same six steps. Skipping one is how deploys break.

1. Make the field optional in `convex/schema.ts` (or add the new field as `v.optional`).
2. Deploy with `npx convex dev`. Update readers to handle `undefined` and writers to set the new shape.
3. Backfill existing documents in batches with an internal mutation or the migrations component.
4. Flip the validator to its final shape (`v.string()` instead of `v.optional(v.string())`, or drop the old field).
5. Deploy again. Validation now passes because every document already matches.
```
END THIRD-PARTY FILE 6616c59f41c94977

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