Document EXTOBS0003: HybridCacheOptions.DisableCompression is obsolete

docs/fundamentals/syslib-diagnostics/extobs0003.md

@@ -0,0 +1,30 @@
+---
+title: EXTOBS0003 warning
+description: Learn about the obsolete HybridCacheOptions.DisableCompression property that generates compile-time warning EXTOBS0003.
+ms.date: 10/29/2026
+f1_keywords:
+  - extobs0003
+ai-usage: ai-generated
+---
+
+# EXTOBS0003: HybridCacheOptions.DisableCompression is obsolete
+
+The <xref:Microsoft.Extensions.Caching.Hybrid.HybridCacheOptions.DisableCompression?displayProperty=nameWithType> property is obsolete. Use of this property generates warning `EXTOBS0003` at compile time.
+
+The default `HybridCache` implementation doesn't provide built-in compression, so the property has no effect, regardless of its value.
+
+Note that the `HybridCacheEntryFlags.DisableCompression` flag isn't obsolete. The flag belongs to the shared abstraction, and while the default `HybridCache` implementation doesn't honor it, other `HybridCache` implementations might.
+
+## Workarounds
+
+Remove references to `HybridCacheOptions.DisableCompression` from your code. For the default `HybridCache` implementation, you don't need a replacement setting because the property never enabled or disabled compression.
+
+To compress cached data, configure a serializer that performs compression. For information about custom serializers, see [HybridCache serialization](../../core/extensions/caching.md#serialization).
+
+## Suppress a warning
+
+If you can't remove references to the obsolete property, suppress `EXTOBS0003` with a `#pragma warning` directive in your source code or a `<NoWarn>` property in your project file. For more information, see [Suppress warnings](obsoletions-overview.md#suppress-warnings).
+
+## See also
+
+- [HybridCache in .NET](../../core/extensions/caching.md#hybrid-caching)

docs/fundamentals/syslib-diagnostics/obsoletions-overview.md

@@ -100,6 +100,7 @@ The following table lists the `EXTOBS0XXX` obsoletions from the `Microsoft.Exten
 |---------------|------------------|-------------|
 | [EXTOBS0001](extobs0001.md) | Warning | <xref:Microsoft.Extensions.Diagnostics.ResourceMonitoring.IResourceMonitor> is obsolete and will be removed in a future version. Consider using [Resource Monitoring observable instruments](../../core/diagnostics/built-in-metrics-diagnostics.md#microsoftextensionsdiagnosticsresourcemonitoring). |
 | [EXTOBS0002](extobs0002.md) | Warning | The `AddServiceLogEnricher` extension methods have been marked as obsolete starting in package version 10.1.0. The methods enrich application logs, not service logs, so they have been replaced with correctly named `AddApplicationLogEnricher` methods. |
+| [EXTOBS0003](extobs0003.md) | Warning | <xref:Microsoft.Extensions.Caching.Hybrid.HybridCacheOptions.DisableCompression?displayProperty=nameWithType> is obsolete because the default `HybridCache` implementation doesn't provide built-in compression and the property has no effect. |
 
 ## Suppress warnings
 

docs/navigate/tools-diagnostics/toc.yml

@@ -4358,6 +4358,8 @@ items:
         href: ../../fundamentals/syslib-diagnostics/extobs0001.md
       - name: EXTOBS0002
         href: ../../fundamentals/syslib-diagnostics/extobs0002.md
+      - name: EXTOBS0003
+        href: ../../fundamentals/syslib-diagnostics/extobs0003.md
   - name: API compatibility
     items:
       - name: Overview