# Preserve Published Layers

> How sb-mig migrates dirty published Storyblok stories without publishing editor drafts.
Storyblok stories can have two meaningful content layers:

* draft/current content returned by the Management API
* published production content from Story Versions API

When a story is published and has unpublished changes, those layers are intentionally different.

## The problem [#the-problem]

A single-layer migration has to choose a bad tradeoff:

* publish the latest draft and expose editor work early
* save the migrated draft and leave production JSON unmigrated

`--publicationMode preserve-layers` avoids that tradeoff for in-place space migrations.

## Command [#command]

```bash
sb-mig migrate content --all \
  --from 12345 \
  --to 12345 \
  --migration migration-name \
  --publicationMode preserve-layers \
  --publicationLanguages all \
  --dry-run
```

`preserve-layers` currently requires:

* `--migrate-from space`
* the same Storyblok space for `--from` and `--to`

## Dirty published write order [#dirty-published-write-order]

For stories where `published === true` and `unpublished_changes === true`, sb-mig:

1. reads draft/current content from Management API
2. reads the latest `status === "published"` version content
3. migrates both layers independently in memory
4. writes migrated published-layer content
5. publishes that migrated published layer
6. restores migrated draft/current content with `publish:false`

The final state keeps the production and draft split:

```txt
published JSON: migrated production content
draft JSON:     migrated editor draft content
story state:    published=true and unpublished_changes=true
```

## Safety checks [#safety-checks]

Before the dual-layer write, sb-mig re-fetches the story and compares `current_version_id` or `updated_at`. If the story changed after migration input was read, it refuses to overwrite new editor work.