IndexedDB migrations

On open, stored model definitions are compared with the configured models. Compatible changes are handled automatically; incompatible changes require a migration handler. A Partial outcome persists progress and pauses opening; reopen with the same target to resume through MigrationContext.previousState. Version-update callbacks run after required index backfills and can query them.

Opening an older store

Read the storage upgrade guide before opening a released store. Engine-specific collection and incrementing-map recovery requirements are in the storage layout.

Pending migrations and other browser contexts

Target-schema matching and unfinished-checkpoint recovery follow the shared migration contract.

Existing browser contexts reject both reads and writes after a pending migration or schema change. Read responses are checked again before publication, and stale live listeners stop before decoding another schema’s journal entries.