Does Godot preserve internal resource IDs when restoring a project backup and re‑importing missing .import files?

Answer

No — and more importantly, the premise needs correcting. Godot's internal resource IDs (RIDs, as returned by Resource.get_rid()) are runtime object handles assigned fresh each time the engine loads a resource. They are not derived from your source assets or import settings, and they are never stable across editor or game sessions, regardless of whether you restore a backup, re-import assets, or change nothing at all. A backup restore and .import regeneration is therefore not the actual risk: RIDs were never safe to serialize in the first place.

What is confirmed

• An RID identifies a resource instance in the currently running engine. Two sessions loading the identical project will assign different RIDs.
• Re-importing assets (regenerating missing .import files) does not "preserve" or "break" RIDs, because RIDs are not stored in .import files and are not computed from them.
• Godot 4.x introduced a separate mechanism, ResourceUID (the uid:// paths you see in scene and script files), which is designed to be a persistent identifier for resources on disk. UIDs are stored alongside the project and survive re-imports and backup restores as long as the files carrying them are part of the backup.
• Resource paths (res://...) remain the most portable stable reference, provided files are not moved or renamed.

Likely explanation for the observed concern

If saved-game data broke after a restore, the cause was almost certainly that raw RIDs (or instance IDs) were written into the save file. Those values were already invalid the moment the original session ended; the backup restore merely made the failure visible. Changes to import presets or engine versions can alter imported resource content, but that is a different issue from RID stability.

What to do instead

1. In save data, reference assets by their res:// path or, on Godot 4.x, their uid:// path (ResourceUID.id_to_text() / ResourceLoader.load() with a UID).
2. For your own game objects, assign explicit identifiers (e.g., a UUID field) rather than engine-assigned handles.
3. Never persist get_rid(), get_instance_id(), or similar runtime values.

Uncertainty and verification

Exact UID behavior across engine upgrades and edge cases (e.g., restoring a backup that omits the project's UID cache) is version-dependent; check the documentation for your specific Godot version. You can confirm the core point quickly: print Resource.get_rid() for a loaded resource, restart the editor without changing anything, and print it again — the values will differ even with no backup or re-import involved.