diff --git a/prisma/migrations/0478_retry_raster_failed_thumbnails/migration.sql b/prisma/migrations/0478_retry_raster_failed_thumbnails/migration.sql
new file mode 100644
index 000000000..e032a6caa
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+++ b/prisma/migrations/0478_retry_raster_failed_thumbnails/migration.sql
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+-- Give every PDF preview that failed to rasterize one more render.
+--
+-- Until this release the server could load two pdf.js versions. Once a local
+-- text read had claimed the in-process pdf.js worker, every later page render
+-- failed until a restart, and the thumbnail job recorded those documents as
+-- `raster-failed`. The backfill treats that reason as final, so their previews
+-- would never be tried again.
+--
+-- Only `raster-failed`: the clash surfaced as a rasterization that returned a
+-- failure, and the thumbnail path maps that to this reason and to no other.
+-- `error` comes from a throw, and the rasterizer never throws; `empty-render`
+-- and `pixel-cap` are decided after a render that worked.
+--
+-- A stored failure cannot say whether the clash caused it or the page really
+-- renders blank, so every such row goes. The boot-time thumbnail backfill
+-- finds each document again, renders it once, and a page that is really blank
+-- records `raster-failed` with one attempt and settles where it was. Running
+-- this again costs one more render per such document and nothing else.
+DELETE FROM "document_thumbnail_failures"
+ WHERE "reason" = 'raster-failed';