Your players' saves outlive your builds. NEXUS Persistence treats them that way.
Every save is a versioned envelope: a header with the schema version, app version, timestamps, playtime and a SHA-256 checksum, wrapped around an opaque JSON payload your code owns. On load, the engine verifies integrity first, then upgrades old schemas stepwise through a registered migration chain — automatically, once per player, re-persisting the result.
What this buys you: - Version upgrades that never bite.
Change your save format, register a migration, bump the version. Old saves keep working. Missing steps fail with the exact dead-end version named — diagnosable from the log alone.
- Corruption that quarantines, not crashes. Checksum mismatch or a mangled file raises a typed event with a readable reason; the game keeps running; the file stays intact for recovery.
- Writes that survive crashes. Temp file, rotate to .bak, move into place — a mid-write crash costs a backup, never a slot.
- Editor-side truth. The Save Inspector shows headers, sizes and integrity for any save folder; duplicate, delete and reveal are one click.
- A pure-C# core. The domain assembly compiles with no engine references — structural purity, unit-tested headless, server-ready.
- Storage you can swap. Filesystem (atomic) and memory (tests) ship in-box; five members put your cloud provider behind the same store.
The demo scene is the pitch: press Play and save, load, migrate a real legacy file (v0 coins → v1 gold) and quarantine a corrupted one — every step narrated in the on-screen log.
Engineering facts: Unity 2021.3 LTS+. Built-in/URP/HDRP. 17 C# sources, 1,389 lines of pure-C# domain, 29 EditMode tests, XML documentation on every public member, ten documentation artifacts, zero third-party code. Support: every ticket answered within 48h on business days; Notion hub with live FAQ, known issues and roadmap.