Add support for prompt caching directives in BedrockChatClient for MEAI

Author: jdaigle

extensions/src/AWSSDK.Extensions.Bedrock.MEAI/BedrockChatClient.cs

@@ -392,12 +392,31 @@ private static List<SystemContentBlock> CreateSystem(List<SystemContentBlock>? r
 
         if (options?.Instructions is { } instructions)
         {
-            system.Add(new SystemContentBlock() { Text = instructions });
+            system.Add(new SystemContentBlock()
+            {
+                Text = instructions,
+            });
         }
 
-        system.AddRange(messages
-            .Where(m => m.Role == ChatRole.System && m.Contents.Any(c => c is TextContent))
-            .Select(m => new SystemContentBlock() { Text = string.Concat(m.Contents.OfType<TextContent>()) }));
+        foreach (var message in messages
+                     .Where(m => m.Role == ChatRole.System && m.Contents.Any(c => c is TextContent)))
+        {
+            system.Add(new SystemContentBlock()
+            {
+                Text = string.Concat(message.Contents.OfType<TextContent>()),
+            });
+
+            if (message.AdditionalProperties?.TryGetValue(nameof(ContentBlock.CachePoint), out var maybeCachePoint) == true)
+            {
+                if (maybeCachePoint is CachePointBlock cachePointBlock)
+                {
+                    system.Add(new SystemContentBlock()
+                    {
+                        CachePoint = cachePointBlock,
+                    });
+                }
+            }
+        }
 
         return system;
     }
@@ -440,6 +459,17 @@ private static List<Message> CreateMessages(List<Message>? rawMessages, IEnumera
                     }
                 }
 
+                if (chatMessage.AdditionalProperties?.TryGetValue(nameof(ContentBlock.CachePoint), out var maybeCachePoint) == true)
+                {
+                    if (maybeCachePoint is CachePointBlock cachePointBlock)
+                    {
+                        contents.Add(new()
+                        {
+                            CachePoint = cachePointBlock
+                        });
+                    }
+                }
+
                 messages.Add(new()
                 {
                     Role = chatMessage.Role == ChatRole.Assistant ? ConversationRole.Assistant : ConversationRole.User,
@@ -573,6 +603,18 @@ private static List<ContentBlock> CreateContents(ChatMessage message)
                     });
                     break;
             }
+
+
+            if (content.AdditionalProperties?.TryGetValue(nameof(ContentBlock.CachePoint), out var maybeCachePoint) == true)
+            {
+                if (maybeCachePoint is CachePointBlock cachePointBlock)
+                {
+                    contents.Add(new()
+                    {
+                        CachePoint = cachePointBlock
+                    });
+                }
+            }
         }
 
         return contents;

generator/.DevConfigs/23b92a6e-3ec2-4193-9ae1-89c242b1e8f6.json

@@ -0,0 +1,11 @@
+{
+  "extensions": [
+    {
+      "extensionName": "Extensions.Bedrock.MEAI",
+      "type": "minor",
+      "changeLogMessages": [
+        "Add support for prompt caching in BedrockChatClient for MEAI"
+      ]
+    }
+  ]
+}