Account deletion cascades to AI conversation data

GDPR Article 17 (Right to Erasure) and CCPA §1798.105 require that deletion of a user's account removes all associated personal data — not just the primary user record. CWE-459 (Incomplete Cleanup) covers exactly this pattern: a delete operation that removes the primary entity but leaves related records orphaned. AI conversation history typically contains some of the most sensitive personal data in the system — verbatim user statements about their problems, circumstances, and intentions. Orphaned conversation records after account deletion mean the user's data persists in the database indefinitely under a now-deleted user ID, violating the erasure right and potentially creating ghost data that can be queried without ownership context.

Configure database-level cascade deletes so conversation records are automatically removed when the parent user is deleted — no application code change required for each new deletion path.

// schema.prisma
model Conversation {
  userId String
  user   User   @relation(fields: [userId], references: [id], onDelete: Cascade)
}

If explicit deletion is required (e.g., audit requirements demand a logged deletion event), use a transaction in your account deletion action:

await db.$transaction([
  db.message.deleteMany({ where: { conversation: { userId } } }),
  db.conversation.deleteMany({ where: { userId } }),
  db.user.delete({ where: { id: userId } })
])

Verify by writing an integration test: create a user, add conversations, delete the user, and assert db.conversation.count({ where: { userId } }) returns 0.