In order to support advanced use cases where only a subset of stories would be included in a Storybook, the --preserve-missing flag could be used to prevent excluded stories from being marked as "removed" in Chromatic. This behavior could lead to problematic situations regarding infrastructure upgrades and cause truly removed stories to never be removed from Chromatic. That's why we are sunsetting the "preserve missing" behavior. As of v6.8.0, using this flag will raise a warning message in the CLI. In a future major version, the flag will be removed completely, and continuing to use it with an older CLI version will start to fail your build.

To upgrade, you should remove the --preserve-missing flag from your CI and/or package.json scripts. If you use our GitHub Action, you should remove the preserveMissing input (with: ...) from your workflow config file. Furthermore, you should make sure that your build-storybook script builds all stories, not just a subset. Check your stories configuration in .storybook/main.js so it doesn't omit any stories (e.g. based on an environment variable).

Most likely you were using preserveMissing to cut down on the number of snapshots taken by Chromatic. To achieve the same goal, you have three options:

Recommended: Use TurboSnap to automatically only snapshot stories for which related source files have changed.
Use --only-story-names to only snapshot stories matching a glob pattern by component/story name.
(Soon) Use --only-story-files to only snapshot stories matching a glob pattern by story filename.