System selector and conversion

Choose the smallest system that meets the need

Situation	Default choice	Reason
Continuous traversable world with bounded residency	World Partition, streaming enabled	Automatic source-distance streaming and one persistent authoring world
Small map that fits budget	World Partition, streaming disabled, or a normal level	Avoid runtime streaming complexity while retaining the desired authoring workflow
Repeated point of interest or gameplay assembly	Level Instance	Reusable sublevel edited in context
Repeated static architectural/mesh assembly	Packed Level Blueprint	Packs supported static content into an optimized actor
Existing UE5 World Partition project	Extend current model	Avoid a second overlapping streaming authority
Legacy/discrete sublevel architecture	Existing level streaming until migration is justified	Conversion risk may exceed its value

World Partition is Epic's recommended UE5 large-world approach. It is not proof that every map needs cell streaming.

Conversion safety workflow

1. Work on a source-controlled branch or verified backup.
2. Inventory Level Blueprints, streaming volumes, scripted sublevel transitions, world settings, always-loaded managers, actor references, foliage, navigation, and HLODs.
3. Resave the source level and correct unstable actor GUID warnings before conversion.
4. Run the conversion commandlet with -ReportOnly first.
5. Review actors that cannot be externalized, reference clusters, sublevel handling, and generated configuration.
6. Convert a copy or use -ConversionSuffix until the result passes validation.
7. Rebuild derived data: HLOD, navigation, foliage, PCG, minimap, or RVT as applicable.
8. Compare gameplay and memory in a cooked build; keep the old map until parity is demonstrated.

General form:

UnrealEditor.exe <Project.uproject> <MapName> -run=WorldPartitionConvertCommandlet -ReportOnly

Useful flags include:

• -ConversionSuffix: preserve the source and write a converted map with a suffix.
• -ReportOnly: analyze without converting.
• -GenerateIni: emit conversion settings that can be reviewed and reused.
• -OnlyMergeSubLevels: merge sublevels without otherwise converting the result to World Partition.

Avoid -SkipStableGUIDValidation as a routine fix. Stable GUIDs are required for repeatable conversion; resave and repair the map instead.

Reject the conversion when

• success depends on Level Blueprint state or streaming callbacks not yet replaced;
• non-OFPA actors inside Level Instances must exist at runtime but the design assumes Embedded Mode;
• reference bundles make most of the world resident;
• target-device memory or traversal hitching regresses with no credible mitigation;
• the team cannot rebuild and validate derived content reproducibly.

Version-sensitive note

UE 5.8 adds World Partition streaming analysis in Unreal Insights and improves scoped HLOD building. Treat these as new workflow capabilities, not permission to skip before/after performance captures.