Addressables - Design Rules

Advisory module. Every rule is distilled from Unity Addressables source at two versions:

• 1.22.3 — com.unity.addressables@1.22.3 (Unity 2022, min 2019.4)
• 2.9.1 — com.unity.addressables@8460f1c9c927 (Unity 6, min 2023.1)

Each rule cites a concrete file/line so the reasoning is auditable and the AI does not improvise against stale memory.

Mode: Both (Semi-Auto + Full-Auto) — documentation only, no REST skills.

When to Load This Module

Load before writing or reviewing any of:

• Addressables.InitializeAsync() / LoadContentCatalogAsync() bootstrap code
• LoadAssetAsync<T> / LoadAssetsAsync<T> / InstantiateAsync and their handle release
• LoadSceneAsync / UnloadSceneAsync — especially with SceneReleaseMode (2.9.1)
• CheckForCatalogUpdates → UpdateCatalogs → CleanBundleCache patch flow
• GetDownloadSizeAsync / DownloadDependenciesAsync / ClearDependencyCacheAsync
• AssetReference / AssetReferenceT<T> field declarations and load/release
• Any code that calls WaitForCompletion() or uses AsyncOperationHandle directly
• Migration from 1.22.3 to 2.9.1 — removed APIs, changed overload signatures

Version Difference Matrix

Area	1.22.3 (Unity 2022)	2.9.1 (Unity 6)
Non-Async variants (LoadAsset, Instantiate, LoadScene, etc.)	[Obsolete] — compile warning	Removed — compile error
IList<object> multi-key overloads	Present	Replaced by IEnumerable
SceneReleaseMode enum	Does not exist	New — controls bundle lifetime on scene unload
LoadSceneAsync releaseMode param	Absent	SceneReleaseMode.ReleaseSceneWhenSceneUnloaded default
LoadAssetsAsync<T>(string key, ...)	Does not exist	New string-key overload
UpdateCatalogs(bool autoCleanBundleCache, ...)	Does not exist	New overload
LegacyResourcesLocator / LegacyResourcesProvider	Present	Removed
DiagnosticEvent / DiagnosticEventCollector	Present	Removed
ResourceManagerEventCollector	Present	Removed
ResourceManager.RegisterDiagnosticCallback()	[Obsolete]	Removed
InitializationOperation property	[Obsolete], returns default	Removed
BinaryCatalogInitializationData	Does not exist	New
CachedFileProvider	Does not exist	New

Critical Rule Summary

#	Rule	Version	Source anchor
1	All non-Async variants (LoadAsset, Instantiate, LoadScene, UnloadScene, GetDownloadSize, DownloadDependencies, Initialize, LoadContentCatalog) are [Obsolete] in 1.22.3 and removed in 2.9.1. Always use the *Async form.	Both	Addressables.cs:1.22.3:862-2226, Addressables.cs:2.9.1 (absent)
2	Every AsyncOperationHandle returned by a Load/Instantiate call MUST be released via Addressables.Release(handle). Forgetting leaks the AssetBundle in memory indefinitely — even after the scene unloads.	Both	AsyncOperationHandle.cs:2.9.1:178-203
3	WaitForCompletion() blocks the calling thread synchronously. On WebGL it is unsupported and throws. Never call it on the main thread in production; use await handle.Task or the Completed event instead.	Both	AsyncOperationHandle.cs:2.9.1:178-203
4	LoadSceneAsync in 2.9.1 adds SceneReleaseMode releaseMode (default ReleaseSceneWhenSceneUnloaded). If a Single-mode load unloads your additive scene and you need the bundle to stay alive, pass OnlyReleaseSceneOnHandleRelease and release the handle manually.	2.9.1	ISceneProvider.cs:2.9.1:14-26, Addressables.cs:2.9.1:1914
5	Multi-key overloads changed from IList<object> to IEnumerable in 2.9.1. The old IList<object> overloads no longer exist — pass IEnumerable or string[].	2.9.1	Addressables.cs:2.9.1:1148,1566,1636
6	LegacyResourcesLocator and LegacyResourcesProvider were removed in 2.9.1. Do not reference them in code targeting Unity 6.	2.9.1	Runtime/ResourceLocators/ (absent in 2.9.1)
7	ResourceManager.RegisterDiagnosticCallback() was [Obsolete] in 1.22.3 and removed in 2.9.1. Use the Addressables Profiler window instead.	2.9.1	ResourceManager.cs:1.22.3:353 (absent in 2.9.1)
8	Catalog update flow is strictly ordered: CheckForCatalogUpdates → UpdateCatalogs. In 2.9.1, UpdateCatalogs(bool autoCleanBundleCache, ...) can auto-clean stale bundles in one call.	Both	Addressables.cs:2.9.1:2092-2147
9	AssetReference.LoadAssetAsync<T>() returns a handle that must be released via assetRef.ReleaseAsset(), NOT Addressables.Release(handle). Mixing the two causes double-release exceptions.	Both	AssetReference.cs:1.22.3:44-46
10	InitializationOperation property (1.22.3) is [Obsolete] and returns default. Do not await it. Use await Addressables.InitializeAsync() instead.	1.22.3	Addressables.cs:1.22.3:981-982

Sub-doc Routing

Sub-doc	When to read
INIT.md	InitializeAsync / LoadContentCatalogAsync / catalog loading order / autoReleaseHandle semantics
HANDLES.md	AsyncOperationHandle<T> lifecycle — Completed, WaitForCompletion, Release, IsDone, Status, OperationException, ref-counting
LOADING.md	LoadAssetAsync, LoadAssetsAsync (all overloads + version diff), MergeMode, InstantiateAsync, ReleaseInstance
SCENE.md	LoadSceneAsync / UnloadSceneAsync / SceneInstance.ActivateAsync / SceneReleaseMode (2.9.1) / activateOnLoad=false pattern
UPDATE.md	CheckForCatalogUpdates → UpdateCatalogs flow / autoCleanBundleCache (2.9.1) / CleanBundleCache / ResourceLocatorInfo
DOWNLOAD.md	GetDownloadSizeAsync / DownloadDependenciesAsync / ClearDependencyCacheAsync / DownloadStatus struct
ASSETREF.md	AssetReference / AssetReferenceT<T> / LoadAssetAsync / ReleaseAsset / OperationHandle property / IsDone guard
PITFALLS.md	30 concrete hallucination pitfalls with version tags + legacy API migration section

Routing to Other Modules

• Asmdef layout for Addressables consumers → load asmdef
• Async orchestration across multiple Addressables operations → load async
• Architecture-level decisions (Addressables vs YooAsset, group strategy) → load architecture
• Performance review of load/release hot paths → load performance

Version Scope

This document targets two versions:

• 1.22.3 — shipped with Unity 2022 LTS. Contains [Obsolete] non-Async variants still present for migration.
• 2.9.1 — shipped with Unity 6 (2023.1+). All [Obsolete] APIs removed. New SceneReleaseMode, binary catalog format, AutoGroupGenerator.

When a rule applies to only one version it is tagged [1.22.3] or [2.9.1]. Untagged rules apply to both.

Migration Notes (hallucination shield)

Legacy API	Status	Replacement	Source
Addressables.Initialize()	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.InitializeAsync()	Addressables.cs:1.22.3:862-864
Addressables.LoadAsset<T>(key)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.LoadAssetAsync<T>(key)	Addressables.cs:1.22.3:992-1007
Addressables.LoadAssets<T>(keys, cb, mode)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.LoadAssetsAsync<T>(keys, cb, mode)	Addressables.cs:1.22.3:1242-1276
Addressables.Instantiate(key, ...)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.InstantiateAsync(key, ...)	Addressables.cs:1.22.3:1892-1972
Addressables.LoadScene(key, ...)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.LoadSceneAsync(key, ...)	Addressables.cs:1.22.3:2090-2106
Addressables.UnloadScene(handle, ...)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.UnloadSceneAsync(handle, ...)	Addressables.cs:1.22.3:2180-2226
Addressables.GetDownloadSize(key)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.GetDownloadSizeAsync(key)	Addressables.cs:1.22.3:1547
Addressables.DownloadDependencies(key)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables.DownloadDependenciesAsync(key)	Addressables.cs:1.22.3:1608
Addressables.InitializationOperation	[Obsolete] in 1.22.3, removed in 2.9.1	await Addressables.InitializeAsync()	Addressables.cs:1.22.3:981-982
LoadResourceLocationsAsync(IList<object> keys, ...)	Present in 1.22.3, removed in 2.9.1	LoadResourceLocationsAsync(IEnumerable keys, ...)	Addressables.cs:2.9.1:1148
GetDownloadSizeAsync(IList<object> keys)	Present in 1.22.3, removed in 2.9.1	GetDownloadSizeAsync(IEnumerable keys)	Addressables.cs:2.9.1:1566
DownloadDependenciesAsync(IList<object> keys, mode, ...)	Present in 1.22.3, removed in 2.9.1	DownloadDependenciesAsync(IEnumerable keys, mode, ...)	Addressables.cs:2.9.1:1636
LegacyResourcesLocator / LegacyResourcesProvider	Present in 1.22.3, removed in 2.9.1	Use Addressables groups for all assets	Runtime/ResourceLocators/LegacyResourcesLocator.cs:1.22.3
ResourceManager.RegisterDiagnosticCallback(...)	[Obsolete] in 1.22.3, removed in 2.9.1	Addressables Profiler window	ResourceManager.cs:1.22.3:353
DiagnosticEvent / DiagnosticEventCollector	Present in 1.22.3, removed in 2.9.1	Addressables Profiler / custom IProfilerEmitter	Runtime/ResourceManager/Diagnostics/:1.22.3

When in doubt, read the cited source — not your memory.