Unity Addressables Design

Addressables - Design Rules

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

• 1.22.3 — [email protected] (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: Documentation only — no REST skills to gate; load freely under any operating mode (Approval / Auto / Bypass).

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.