initial refactoring

2024-07-15 17:45:08 -04:00
parent ed815d8b3d
commit 53902e6fe2
39 changed files with 598 additions and 503 deletions
--- a/models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/AnthropicChatModel.java
+++ b/models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/AnthropicChatModel.java
@@ -32,7 +32,7 @@ import org.springframework.ai.anthropic.api.AnthropicApi.ChatCompletionResponse;
 import org.springframework.ai.anthropic.api.AnthropicApi.ContentBlock;
 import org.springframework.ai.anthropic.api.AnthropicApi.ContentBlock.ContentBlockType;
 import org.springframework.ai.anthropic.api.AnthropicApi.Role;
-import org.springframework.ai.anthropic.metadata.AnthropicChatResponseMetadata;
+import org.springframework.ai.anthropic.metadata.AnthropicChatResponseMetadataUtils;
 import org.springframework.ai.chat.messages.AssistantMessage;
 import org.springframework.ai.chat.messages.Message;
 import org.springframework.ai.chat.messages.MessageType;
@@ -228,7 +228,7 @@ public class AnthropicChatModel extends AbstractToolCallSupport<ChatCompletionRe
 				.withGenerationMetadata(ChatGenerationMetadata.from(chatCompletion.stopReason(), null));
 		}).toList();

-		return new ChatResponse(generations, AnthropicChatResponseMetadata.from(chatCompletion));
+		return new ChatResponse(generations, AnthropicChatResponseMetadataUtils.from(chatCompletion));
 	}

 	private String fromMediaData(Object mediaData) {
--- a/models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/metadata/AnthropicChatResponseMetadata.java
+++ b/models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/metadata/AnthropicChatResponseMetadata.java
@@ -1,103 +0,0 @@
-/*
- * Copyright 2023 - 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.ai.anthropic.metadata;
-
-import org.springframework.ai.anthropic.api.AnthropicApi;
-import org.springframework.ai.chat.metadata.ChatResponseMetadata;
-import org.springframework.ai.chat.metadata.EmptyRateLimit;
-import org.springframework.ai.chat.metadata.EmptyUsage;
-import org.springframework.ai.chat.metadata.RateLimit;
-import org.springframework.ai.chat.metadata.Usage;
-import org.springframework.lang.Nullable;
-import org.springframework.util.Assert;
-
-import java.util.HashMap;
-
-/**
- * {@link ChatResponseMetadata} implementation for {@literal AnthropicApi}.
- *
- * @author Christian Tzolov
- * @author Thomas Vitale
- * @see ChatResponseMetadata
- * @see RateLimit
- * @see Usage
- * @since 1.0.0
- */
-public class AnthropicChatResponseMetadata extends HashMap<String, Object> implements ChatResponseMetadata {
-
-	protected static final String AI_METADATA_STRING = "{ @type: %1$s, id: %2$s, model: %3$s, usage: %4$s, rateLimit: %5$s }";
-
-	public static AnthropicChatResponseMetadata from(AnthropicApi.ChatCompletionResponse result) {
-		Assert.notNull(result, "Anthropic ChatCompletionResult must not be null");
-		AnthropicUsage usage = AnthropicUsage.from(result.usage());
-		return new AnthropicChatResponseMetadata(result.id(), result.model(), usage);
-	}
-
-	private final String id;
-
-	private final String model;
-
-	@Nullable
-	private RateLimit rateLimit;
-
-	private final Usage usage;
-
-	protected AnthropicChatResponseMetadata(String id, String model, AnthropicUsage usage) {
-		this(id, model, usage, null);
-	}
-
-	protected AnthropicChatResponseMetadata(String id, String model, AnthropicUsage usage,
-			@Nullable AnthropicRateLimit rateLimit) {
-		this.id = id;
-		this.model = model;
-		this.usage = usage;
-		this.rateLimit = rateLimit;
-	}
-
-	@Override
-	public String getId() {
-		return this.id;
-	}
-
-	@Override
-	public String getModel() {
-		return this.model;
-	}
-
-	@Override
-	@Nullable
-	public RateLimit getRateLimit() {
-		RateLimit rl = this.rateLimit;
-		return rl != null ? rl : new EmptyRateLimit();
-	}
-
-	@Override
-	public Usage getUsage() {
-		Usage usage = this.usage;
-		return usage != null ? usage : new EmptyUsage();
-	}
-
-	public AnthropicChatResponseMetadata withRateLimit(RateLimit rateLimit) {
-		this.rateLimit = rateLimit;
-		return this;
-	}
-
-	@Override
-	public String toString() {
-		return AI_METADATA_STRING.formatted(getClass().getName(), getId(), getModel(), getUsage(), getRateLimit());
-	}
-
-}
--- a/models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/metadata/AnthropicChatResponseMetadataUtils.java
+++ b/models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/metadata/AnthropicChatResponseMetadataUtils.java
@@ -0,0 +1,54 @@
+/*
+ * Copyright 2023 - 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.ai.anthropic.metadata;
+
+import org.springframework.ai.anthropic.api.AnthropicApi;
+import org.springframework.ai.chat.metadata.ChatResponseMetadata;
+import org.springframework.ai.chat.metadata.EmptyRateLimit;
+import org.springframework.ai.chat.metadata.EmptyUsage;
+import org.springframework.ai.chat.metadata.RateLimit;
+import org.springframework.ai.chat.metadata.Usage;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+import java.util.HashMap;
+
+/**
+ * {@link ChatResponseMetadata} implementation for {@literal AnthropicApi}.
+ *
+ * @author Christian Tzolov
+ * @author Thomas Vitale
+ * @see ChatResponseMetadata
+ * @see RateLimit
+ * @see Usage
+ * @since 1.0.0
+ */
+public abstract class AnthropicChatResponseMetadataUtils {
+
+	public static ChatResponseMetadata from(AnthropicApi.ChatCompletionResponse result) {
+		Assert.notNull(result, "Anthropic ChatCompletionResult must not be null");
+		AnthropicUsage usage = AnthropicUsage.from(result.usage());
+		return ChatResponseMetadata.builder()
+			.withId(result.id())
+			.withModel(result.model())
+			.withUsage(usage)
+			.withKeyValue("stop-reason", result.stopReason())
+			.withKeyValue("stop-sequence", result.stopSequence())
+			.withKeyValue("type", result.type())
+			.build();
+	}
+
+}
--- a/models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/AzureOpenAiChatModel.java
+++ b/models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/AzureOpenAiChatModel.java
@@ -43,7 +43,7 @@ import com.azure.core.util.BinaryData;
 import com.azure.core.util.IterableStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.springframework.ai.azure.openai.metadata.AzureOpenAiChatResponseMetadata;
+import org.springframework.ai.azure.openai.metadata.AzureOpenAiChatResponseMetadataUtils;
 import org.springframework.ai.chat.messages.Message;
 import org.springframework.ai.chat.metadata.ChatGenerationMetadata;
 import org.springframework.ai.chat.metadata.PromptMetadata;
@@ -155,7 +155,7 @@ public class AzureOpenAiChatModel extends
 		PromptMetadata promptFilterMetadata = generatePromptMetadata(chatCompletions);

 		return new ChatResponse(generations,
-				AzureOpenAiChatResponseMetadata.from(chatCompletions, promptFilterMetadata));
+				AzureOpenAiChatResponseMetadataUtils.from(chatCompletions, promptFilterMetadata));
 	}

 	@Override
--- a/models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/metadata/AzureOpenAiChatResponseMetadataUtils.java
+++ b/models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/metadata/AzureOpenAiChatResponseMetadataUtils.java
@@ -22,8 +22,6 @@ import org.springframework.ai.chat.metadata.PromptMetadata;
 import org.springframework.ai.chat.metadata.Usage;
 import org.springframework.util.Assert;

-import java.util.HashMap;
-
 /**
 * {@link ChatResponseMetadata} implementation for
 * {@literal Microsoft Azure OpenAI Service}.
@@ -33,51 +31,22 @@ import java.util.HashMap;
 * @see ChatResponseMetadata
 * @since 0.7.1
 */
-public class AzureOpenAiChatResponseMetadata extends HashMap<String, Object> implements ChatResponseMetadata {
-
-	protected static final String AI_METADATA_STRING = "{ @type: %1$s, id: %2$s, usage: %3$s, rateLimit: %4$s }";
+public abstract class AzureOpenAiChatResponseMetadataUtils {

 	@SuppressWarnings("all")
-	public static AzureOpenAiChatResponseMetadata from(ChatCompletions chatCompletions,
-			PromptMetadata promptFilterMetadata) {
+	public static ChatResponseMetadata from(ChatCompletions chatCompletions, PromptMetadata promptFilterMetadata) {
 		Assert.notNull(chatCompletions, "Azure OpenAI ChatCompletions must not be null");
 		String id = chatCompletions.getId();
 		AzureOpenAiUsage usage = AzureOpenAiUsage.from(chatCompletions);
-		AzureOpenAiChatResponseMetadata chatResponseMetadata = new AzureOpenAiChatResponseMetadata(id, usage,
-				promptFilterMetadata);
+		ChatResponseMetadata chatResponseMetadata = ChatResponseMetadata.builder()
+			.withId(id)
+			.withUsage(usage)
+			.withModel(chatCompletions.getModel())
+			.withPromptMetadata(promptFilterMetadata)
+			.withKeyValue("system-fingerprint", chatCompletions.getSystemFingerprint())
+			.build();
+
 		return chatResponseMetadata;
 	}

-	private final String id;
-
-	private final Usage usage;
-
-	private final PromptMetadata promptMetadata;
-
-	protected AzureOpenAiChatResponseMetadata(String id, AzureOpenAiUsage usage, PromptMetadata promptMetadata) {
-		this.id = id;
-		this.usage = usage;
-		this.promptMetadata = promptMetadata;
-	}
-
-	@Override
-	public String getId() {
-		return this.id;
-	}
-
-	@Override
-	public Usage getUsage() {
-		return this.usage;
-	}
-
-	@Override
-	public PromptMetadata getPromptMetadata() {
-		return this.promptMetadata;
-	}
-
-	@Override
-	public String toString() {
-		return AI_METADATA_STRING.formatted(getClass().getTypeName(), getId(), getUsage(), getRateLimit());
-	}
-
 }
--- a/models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/metadata/AzureOpenAiImageResponseMetadata.java
+++ b/models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/metadata/AzureOpenAiImageResponseMetadata.java
@@ -2,6 +2,7 @@ package org.springframework.ai.azure.openai.metadata;

 import com.azure.ai.openai.models.ImageGenerations;
 import org.springframework.ai.image.ImageResponseMetadata;
+import org.springframework.ai.model.MutableResponseMetadata;
 import org.springframework.util.Assert;

 import java.util.HashMap;
@@ -15,7 +16,7 @@ import java.util.Objects;
 * @author Benoit Moussaud
 * @since 1.0.0 M1
 */
-public class AzureOpenAiImageResponseMetadata extends HashMap<String, Object> implements ImageResponseMetadata {
+public class AzureOpenAiImageResponseMetadata extends ImageResponseMetadata {

 	private final Long created;

--- a/models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/MistralAiChatModel.java
+++ b/models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/MistralAiChatModel.java
@@ -30,7 +30,7 @@ import org.springframework.ai.mistralai.api.MistralAiApi.ChatCompletionChunk;
 import org.springframework.ai.mistralai.api.MistralAiApi.ChatCompletionMessage;
 import org.springframework.ai.mistralai.api.MistralAiApi.ChatCompletionMessage.ToolCall;
 import org.springframework.ai.mistralai.api.MistralAiApi.ChatCompletionRequest;
-import org.springframework.ai.mistralai.metadata.MistralAiChatResponseMetadata;
+import org.springframework.ai.mistralai.metadata.MistralAiChatResponseMetadataUtils;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.AbstractFunctionCallSupport;
 import org.springframework.ai.model.function.FunctionCallbackContext;
@@ -120,7 +120,7 @@ public class MistralAiChatModel extends
 					.withGenerationMetadata(ChatGenerationMetadata.from(choice.finishReason().name(), null)))
 				.toList();

-			return new ChatResponse(generations, MistralAiChatResponseMetadata.from(chatCompletion));
+			return new ChatResponse(generations, MistralAiChatResponseMetadataUtils.from(chatCompletion));
 		});
 	}

--- a/models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/metadata/MistralAiChatResponseMetadata.java
+++ b/models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/metadata/MistralAiChatResponseMetadata.java
@@ -1,62 +0,0 @@
-package org.springframework.ai.mistralai.metadata;
-
-import org.springframework.ai.chat.metadata.ChatResponseMetadata;
-import org.springframework.ai.chat.metadata.EmptyUsage;
-import org.springframework.ai.chat.metadata.Usage;
-import org.springframework.ai.mistralai.api.MistralAiApi;
-import org.springframework.util.Assert;
-
-import java.util.HashMap;
-
-/**
- * {@link ChatResponseMetadata} implementation for {@literal Mistral AI}.
- *
- * @author Thomas Vitale
- * @see ChatResponseMetadata
- * @see Usage
- * @since 1.0.0
- */
-public class MistralAiChatResponseMetadata extends HashMap<String, Object> implements ChatResponseMetadata {
-
-	protected static final String AI_METADATA_STRING = "{ @type: %1$s, id: %2$s, model: %3$s, usage: %4$s }";
-
-	public static MistralAiChatResponseMetadata from(MistralAiApi.ChatCompletion result) {
-		Assert.notNull(result, "Mistral AI ChatCompletion must not be null");
-		MistralAiUsage usage = MistralAiUsage.from(result.usage());
-		return new MistralAiChatResponseMetadata(result.id(), result.model(), usage);
-	}
-
-	private final String id;
-
-	private final String model;
-
-	private final Usage usage;
-
-	protected MistralAiChatResponseMetadata(String id, String model, MistralAiUsage usage) {
-		this.id = id;
-		this.model = model;
-		this.usage = usage;
-	}
-
-	@Override
-	public String getId() {
-		return this.id;
-	}
-
-	@Override
-	public String getModel() {
-		return this.model;
-	}
-
-	@Override
-	public Usage getUsage() {
-		Usage usage = this.usage;
-		return usage != null ? usage : new EmptyUsage();
-	}
-
-	@Override
-	public String toString() {
-		return AI_METADATA_STRING.formatted(getClass().getName(), getId(), getModel(), getUsage());
-	}
-
-}
--- a/models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/metadata/MistralAiChatResponseMetadataUtils.java
+++ b/models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/metadata/MistralAiChatResponseMetadataUtils.java
@@ -0,0 +1,32 @@
+package org.springframework.ai.mistralai.metadata;
+
+import org.springframework.ai.chat.metadata.ChatResponseMetadata;
+import org.springframework.ai.chat.metadata.EmptyUsage;
+import org.springframework.ai.chat.metadata.Usage;
+import org.springframework.ai.mistralai.api.MistralAiApi;
+import org.springframework.util.Assert;
+
+import java.util.HashMap;
+
+/**
+ * {@link ChatResponseMetadata} implementation for {@literal Mistral AI}.
+ *
+ * @author Thomas Vitale
+ * @see ChatResponseMetadata
+ * @see Usage
+ * @since 1.0.0
+ */
+public abstract class MistralAiChatResponseMetadataUtils {
+
+	public static ChatResponseMetadata from(MistralAiApi.ChatCompletion result) {
+		Assert.notNull(result, "Mistral AI ChatCompletion must not be null");
+		MistralAiUsage usage = MistralAiUsage.from(result.usage());
+		return ChatResponseMetadata.builder()
+			.withId(result.id())
+			.withModel(result.model())
+			.withUsage(usage)
+			.withKeyValue("created", result.created())
+			.build();
+	}
+
+}
--- a/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java
+++ b/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaChatModel.java
@@ -19,7 +19,7 @@ import java.util.Base64;
 import java.util.List;

 import org.springframework.ai.chat.model.ChatModel;
-import org.springframework.ai.ollama.metadata.OllamaChatResponseMetadata;
+import org.springframework.ai.ollama.metadata.OllamaChatResponseMetadataUtils;
 import reactor.core.publisher.Flux;

 import org.springframework.ai.chat.model.ChatResponse;
@@ -102,7 +102,7 @@ public class OllamaChatModel implements ChatModel {
 		if (response.promptEvalCount() != null && response.evalCount() != null) {
 			generator = generator.withGenerationMetadata(ChatGenerationMetadata.from("unknown", null));
 		}
-		return new ChatResponse(List.of(generator), OllamaChatResponseMetadata.from(response));
+		return new ChatResponse(List.of(generator), OllamaChatResponseMetadataUtils.from(response));
 	}

 	@Override
@@ -116,7 +116,7 @@ public class OllamaChatModel implements ChatModel {
 			if (Boolean.TRUE.equals(chunk.done())) {
 				generation = generation.withGenerationMetadata(ChatGenerationMetadata.from("unknown", null));
 			}
-			return new ChatResponse(List.of(generation), OllamaChatResponseMetadata.from(chunk));
+			return new ChatResponse(List.of(generation), OllamaChatResponseMetadataUtils.from(chunk));
 		});
 	}

--- a/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/metadata/OllamaChatResponseMetadataUtils.java
+++ b/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/metadata/OllamaChatResponseMetadataUtils.java
@@ -28,30 +28,23 @@ import java.util.HashMap;
 * @see ChatResponseMetadata
 * @author Fu Cheng
 */
-public class OllamaChatResponseMetadata extends HashMap<String, Object> implements ChatResponseMetadata {
+public abstract class OllamaChatResponseMetadataUtils {

-	protected static final String AI_METADATA_STRING = "{ @type: %1$s, usage: %2$s, rateLimit: %3$s }";
-
-	public static OllamaChatResponseMetadata from(OllamaApi.ChatResponse response) {
+	public static ChatResponseMetadata from(OllamaApi.ChatResponse response) {
 		Assert.notNull(response, "OllamaApi.ChatResponse must not be null");
-		Usage usage = OllamaUsage.from(response);
-		return new OllamaChatResponseMetadata(usage);
-	}
+		return ChatResponseMetadata.builder()
+			.withUsage(OllamaUsage.from(response))
+			.withModel(response.model())
+			.withKeyValue("created-at", response.createdAt())
+			.withKeyValue("eval-duration", response.evalDuration())
+			.withKeyValue("eval-count", response.evalCount())
+			.withKeyValue("load-duration", response.loadDuration())
+			.withKeyValue("eval-duration", response.promptEvalDuration())
+			.withKeyValue("eval-count", response.promptEvalCount())
+			.withKeyValue("total-duration", response.totalDuration())
+			.withKeyValue("done", response.done())
+			.build();

-	private final Usage usage;
-
-	protected OllamaChatResponseMetadata(Usage usage) {
-		this.usage = usage;
-	}
-
-	@Override
-	public Usage getUsage() {
-		return this.usage;
-	}
-
-	@Override
-	public String toString() {
-		return AI_METADATA_STRING.formatted(getClass().getTypeName(), getUsage(), getRateLimit());
 	}

 }
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/ImageResponseMetadata.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/ImageResponseMetadata.java
@@ -1,5 +1,5 @@
 package org.springframework.ai.openai;

-public class ImageResponseMetadata {
+public interface ImageResponseMetadata {

 }
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatModel.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatModel.java
@@ -15,14 +15,6 @@
 */
 package org.springframework.ai.openai;

-import java.util.ArrayList;
-import java.util.Base64;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.ai.chat.messages.AssistantMessage;
@@ -49,7 +41,7 @@ import org.springframework.ai.openai.api.OpenAiApi.ChatCompletionMessage.ChatCom
 import org.springframework.ai.openai.api.OpenAiApi.ChatCompletionMessage.MediaContent;
 import org.springframework.ai.openai.api.OpenAiApi.ChatCompletionMessage.ToolCall;
 import org.springframework.ai.openai.api.OpenAiApi.ChatCompletionRequest;
-import org.springframework.ai.openai.metadata.OpenAiChatResponseMetadata;
+import org.springframework.ai.openai.metadata.OpenAiChatResponseMetadataUtils;
 import org.springframework.ai.openai.metadata.support.OpenAiResponseHeaderExtractor;
 import org.springframework.ai.retry.RetryUtils;
 import org.springframework.http.ResponseEntity;
@@ -57,10 +49,17 @@ import org.springframework.retry.support.RetryTemplate;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.MimeType;
-
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;

+import java.util.ArrayList;
+import java.util.Base64;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
 /**
 * {@link ChatModel} and {@link StreamingChatModel} implementation for {@literal OpenAI}
 * backed by {@link OpenAiApi}.
@@ -165,7 +164,7 @@ public class OpenAiChatModel extends AbstractToolCallSupport<ChatCompletion> imp
 			}

 			// Non function calling.
-			RateLimit rateLimits = OpenAiResponseHeaderExtractor.extractAiResponseHeaders(completionEntity);
+			RateLimit rateLimit = OpenAiResponseHeaderExtractor.extractAiResponseHeaders(completionEntity);

 			List<Choice> choices = chatCompletion.choices();
 			if (choices == null) {
@@ -187,7 +186,7 @@ public class OpenAiChatModel extends AbstractToolCallSupport<ChatCompletion> imp
 			}).toList();

 			return new ChatResponse(generations,
-					OpenAiChatResponseMetadata.from(completionEntity.getBody()).withRateLimit(rateLimits));
+					OpenAiChatResponseMetadataUtils.from(completionEntity.getBody(), rateLimit));
 		});
 	}

@@ -237,7 +236,7 @@ public class OpenAiChatModel extends AbstractToolCallSupport<ChatCompletion> imp
 						}).toList();

 						if (chatCompletion2.usage() != null) {
-							return new ChatResponse(generations, OpenAiChatResponseMetadata.from(chatCompletion2));
+							return new ChatResponse(generations, OpenAiChatResponseMetadataUtils.from(chatCompletion2));
 						}
 						else {
 							return new ChatResponse(generations);
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiImageModel.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiImageModel.java
@@ -15,8 +15,6 @@
 */
 package org.springframework.ai.openai;

-import java.util.List;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.ai.image.Image;
@@ -29,12 +27,13 @@ import org.springframework.ai.image.ImageResponseMetadata;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.openai.api.OpenAiImageApi;
 import org.springframework.ai.openai.metadata.OpenAiImageGenerationMetadata;
-import org.springframework.ai.openai.metadata.OpenAiImageResponseMetadata;
 import org.springframework.ai.retry.RetryUtils;
 import org.springframework.http.ResponseEntity;
 import org.springframework.retry.support.RetryTemplate;
 import org.springframework.util.Assert;

+import java.util.List;
+
 /**
 * OpenAiImageModel is a class that implements the ImageModel interface. It provides a
 * client for calling the OpenAI image generation API.
@@ -130,7 +129,7 @@ public class OpenAiImageModel implements ImageModel {
 					new OpenAiImageGenerationMetadata(entry.revisedPrompt()));
 		}).toList();

-		ImageResponseMetadata openAiImageResponseMetadata = OpenAiImageResponseMetadata.from(imageApiResponse);
+		ImageResponseMetadata openAiImageResponseMetadata = new ImageResponseMetadata(imageApiResponse.created());
 		return new ImageResponse(imageGenerationList, openAiImageResponseMetadata);
 	}

--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/OpenAiChatResponseMetadata.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/OpenAiChatResponseMetadata.java
@@ -1,103 +0,0 @@
-/*
- * Copyright 2023 - 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.ai.openai.metadata;
-
-import org.springframework.ai.chat.metadata.ChatResponseMetadata;
-import org.springframework.ai.chat.metadata.EmptyRateLimit;
-import org.springframework.ai.chat.metadata.EmptyUsage;
-import org.springframework.ai.chat.metadata.RateLimit;
-import org.springframework.ai.chat.metadata.Usage;
-import org.springframework.ai.openai.api.OpenAiApi;
-import org.springframework.lang.Nullable;
-import org.springframework.util.Assert;
-
-import java.util.HashMap;
-
-/**
- * {@link ChatResponseMetadata} implementation for {@literal OpenAI}.
- *
- * @author John Blum
- * @author Thomas Vitale
- * @see ChatResponseMetadata
- * @see RateLimit
- * @see Usage
- * @since 0.7.0
- */
-public class OpenAiChatResponseMetadata extends HashMap<String, Object> implements ChatResponseMetadata {
-
-	protected static final String AI_METADATA_STRING = "{ @type: %1$s, id: %2$s, model: %3$s, usage: %4$s, rateLimit: %5$s }";
-
-	public static OpenAiChatResponseMetadata from(OpenAiApi.ChatCompletion result) {
-		Assert.notNull(result, "OpenAI ChatCompletionResult must not be null");
-		OpenAiUsage usage = OpenAiUsage.from(result.usage());
-		return new OpenAiChatResponseMetadata(result.id(), result.model(), usage);
-	}
-
-	private final String id;
-
-	private final String model;
-
-	@Nullable
-	private RateLimit rateLimit;
-
-	private final Usage usage;
-
-	protected OpenAiChatResponseMetadata(String id, String model, OpenAiUsage usage) {
-		this(id, model, usage, null);
-	}
-
-	protected OpenAiChatResponseMetadata(String id, String model, OpenAiUsage usage,
-			@Nullable OpenAiRateLimit rateLimit) {
-		this.id = id;
-		this.model = model;
-		this.usage = usage;
-		this.rateLimit = rateLimit;
-	}
-
-	@Override
-	public String getId() {
-		return this.id;
-	}
-
-	@Override
-	public String getModel() {
-		return this.model;
-	}
-
-	@Override
-	@Nullable
-	public RateLimit getRateLimit() {
-		RateLimit rateLimit = this.rateLimit;
-		return rateLimit != null ? rateLimit : new EmptyRateLimit();
-	}
-
-	@Override
-	public Usage getUsage() {
-		Usage usage = this.usage;
-		return usage != null ? usage : new EmptyUsage();
-	}
-
-	public OpenAiChatResponseMetadata withRateLimit(RateLimit rateLimit) {
-		this.rateLimit = rateLimit;
-		return this;
-	}
-
-	@Override
-	public String toString() {
-		return AI_METADATA_STRING.formatted(getClass().getName(), getId(), getModel(), getUsage(), getRateLimit());
-	}
-
-}
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/OpenAiChatResponseMetadataUtils.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/OpenAiChatResponseMetadataUtils.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2023 - 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.ai.openai.metadata;
+
+import org.springframework.ai.chat.metadata.ChatResponseMetadata;
+import org.springframework.ai.chat.metadata.RateLimit;
+import org.springframework.ai.chat.metadata.Usage;
+import org.springframework.ai.openai.api.OpenAiApi;
+import org.springframework.util.Assert;
+
+/**
+ * {@link ChatResponseMetadata} implementation for {@literal OpenAI}.
+ *
+ * @author John Blum
+ * @author Thomas Vitale
+ * @see ChatResponseMetadata
+ * @see RateLimit
+ * @see Usage
+ * @since 0.7.0
+ */
+public abstract class OpenAiChatResponseMetadataUtils {
+
+	public static ChatResponseMetadata from(OpenAiApi.ChatCompletion result) {
+		Assert.notNull(result, "OpenAI ChatCompletionResult must not be null");
+		return ChatResponseMetadata.builder()
+			.withId(result.id())
+			.withUsage(OpenAiUsage.from(result.usage()))
+			.withModel(result.model())
+			.withKeyValue("created", result.created())
+			.withKeyValue("system-fingerprint", result.systemFingerprint())
+			.build();
+	}
+
+	public static ChatResponseMetadata from(OpenAiApi.ChatCompletion result, RateLimit rateLimit) {
+		Assert.notNull(result, "OpenAI ChatCompletionResult must not be null");
+		return ChatResponseMetadata.builder()
+			.withId(result.id())
+			.withUsage(OpenAiUsage.from(result.usage()))
+			.withModel(result.model())
+			.withRateLimit(rateLimit)
+			.withKeyValue("created", result.created())
+			.withKeyValue("system-fingerprint", result.systemFingerprint())
+			.build();
+	}
+
+}
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/OpenAiImageResponseMetadata.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/OpenAiImageResponseMetadata.java
@@ -1,62 +0,0 @@
-/*
- * Copyright 2023 - 2024 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.ai.openai.metadata;
-
-import org.springframework.ai.image.ImageResponseMetadata;
-import org.springframework.ai.openai.api.OpenAiImageApi;
-import org.springframework.util.Assert;
-
-import java.util.HashMap;
-import java.util.Objects;
-
-public class OpenAiImageResponseMetadata extends HashMap<String, Object> implements ImageResponseMetadata {
-
-	private final Long created;
-
-	public static OpenAiImageResponseMetadata from(OpenAiImageApi.OpenAiImageResponse openAiImageResponse) {
-		Assert.notNull(openAiImageResponse, "OpenAiImageResponse must not be null");
-		return new OpenAiImageResponseMetadata(openAiImageResponse.created());
-	}
-
-	protected OpenAiImageResponseMetadata(Long created) {
-		this.created = created;
-	}
-
-	@Override
-	public Long getCreated() {
-		return this.created;
-	}
-
-	@Override
-	public String toString() {
-		return "OpenAiImageResponseMetadata{" + "created=" + created + '}';
-	}
-
-	@Override
-	public boolean equals(Object o) {
-		if (this == o)
-			return true;
-		if (!(o instanceof OpenAiImageResponseMetadata that))
-			return false;
-		return Objects.equals(created, that.created);
-	}
-
-	@Override
-	public int hashCode() {
-		return Objects.hash(created);
-	}
-
-}
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/audio/OpenAiAudioSpeechResponseMetadata.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/audio/OpenAiAudioSpeechResponseMetadata.java
@@ -18,6 +18,7 @@ package org.springframework.ai.openai.metadata.audio;

 import org.springframework.ai.chat.metadata.EmptyRateLimit;
 import org.springframework.ai.chat.metadata.RateLimit;
+import org.springframework.ai.model.MutableResponseMetadata;
 import org.springframework.ai.model.ResponseMetadata;
 import org.springframework.ai.openai.api.OpenAiAudioApi;
 import org.springframework.lang.Nullable;
@@ -31,7 +32,7 @@ import java.util.HashMap;
 * @author Ahmed Yousri
 * @see RateLimit
 */
-public class OpenAiAudioSpeechResponseMetadata extends HashMap<String, Object> implements ResponseMetadata {
+public class OpenAiAudioSpeechResponseMetadata extends MutableResponseMetadata {

 	protected static final String AI_METADATA_STRING = "{ @type: %1$s, requestsLimit: %2$s }";

--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/audio/OpenAiAudioTranscriptionResponseMetadata.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/metadata/audio/OpenAiAudioTranscriptionResponseMetadata.java
@@ -17,6 +17,7 @@ package org.springframework.ai.openai.metadata.audio;

 import org.springframework.ai.chat.metadata.EmptyRateLimit;
 import org.springframework.ai.chat.metadata.RateLimit;
+import org.springframework.ai.model.MutableResponseMetadata;
 import org.springframework.ai.model.ResponseMetadata;
 import org.springframework.ai.openai.api.OpenAiAudioApi;
 import org.springframework.ai.openai.metadata.OpenAiRateLimit;
@@ -32,7 +33,7 @@ import java.util.HashMap;
 * @since 0.8.1
 * @see RateLimit
 */
-public class OpenAiAudioTranscriptionResponseMetadata extends HashMap<String, Object> implements ResponseMetadata {
+public class OpenAiAudioTranscriptionResponseMetadata extends MutableResponseMetadata {

 	protected static final String AI_METADATA_STRING = "{ @type: %1$s, rateLimit: %4$s }";

--- a/models/spring-ai-postgresml/src/main/java/org/springframework/ai/postgresml/PostgresMlEmbeddingModel.java
+++ b/models/spring-ai-postgresml/src/main/java/org/springframework/ai/postgresml/PostgresMlEmbeddingModel.java
@@ -200,9 +200,13 @@ public class PostgresMlEmbeddingModel extends AbstractEmbeddingModel implements
 			}
 		}

-		var metadata = new EmbeddingResponseMetadata(
-				Map.of("transformer", optionsToUse.getTransformer(), "vector-type", optionsToUse.getVectorType().name(),
-						"kwargs", ModelOptionsUtils.toJsonString(optionsToUse.getKwargs())));
+		var metadata = new EmbeddingResponseMetadata();
+		Map<String, Object> embeddingMetadata = Map.of("transformer", optionsToUse.getTransformer(), "vector-type",
+				optionsToUse.getVectorType().name(), "kwargs",
+				ModelOptionsUtils.toJsonString(optionsToUse.getKwargs()));
+		for (Map.Entry<String, Object> entry : embeddingMetadata.entrySet()) {
+			metadata.put(entry.getKey(), entry.getValue());
+		}

 		return new EmbeddingResponse(data, metadata);
 	}
--- a/models/spring-ai-postgresml/src/test/java/org/springframework/ai/postgresml/PostgresMlEmbeddingModelIT.java
+++ b/models/spring-ai-postgresml/src/test/java/org/springframework/ai/postgresml/PostgresMlEmbeddingModelIT.java
@@ -30,6 +30,7 @@ import org.junit.jupiter.params.provider.ValueSource;
 import org.springframework.ai.embedding.EmbeddingOptions;
 import org.springframework.ai.embedding.EmbeddingRequest;
 import org.springframework.ai.embedding.EmbeddingResponse;
+import org.springframework.ai.embedding.EmbeddingResponseMetadata;
 import org.springframework.ai.postgresml.PostgresMlEmbeddingModel.VectorType;

 import org.testcontainers.containers.PostgreSQLContainer;
@@ -144,7 +145,21 @@ class PostgresMlEmbeddingModelIT {

 		assertThat(embeddingResponse).isNotNull();
 		assertThat(embeddingResponse.getResults()).hasSize(3);
-		assertThat(embeddingResponse.getMetadata()).containsExactlyInAnyOrderEntriesOf(
+		EmbeddingResponseMetadata metadata = embeddingResponse.getMetadata();
+
+		assertThat(metadata.get("transformer").toString())
+			.as("Transformer in metadata should be 'distilbert-base-uncased'")
+			.isEqualTo("distilbert-base-uncased");
+
+		assertThat(metadata.get("vector-type").toString())
+			.as("Vector type in metadata should match expected vector type")
+			.isEqualTo(vectorType);
+
+		assertThat(metadata.get("kwargs").toString()).as("kwargs in metadata should be '{}'").isEqualTo("{}");
+
+		assertThat(metadata.getRawMap().keySet()).as("Metadata should contain exactly the expected keys")
+			.containsExactlyInAnyOrder("transformer", "vector-type", "kwargs");
+		assertThat(embeddingResponse.getMetadata().getRawMap()).containsExactlyInAnyOrderEntriesOf(
 				Map.of("transformer", "distilbert-base-uncased", "vector-type", vectorType, "kwargs", "{}"));
 		assertThat(embeddingResponse.getResults().get(0).getIndex()).isEqualTo(0);
 		assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(768);
@@ -170,7 +185,7 @@ class PostgresMlEmbeddingModelIT {

 		assertThat(embeddingResponse).isNotNull();
 		assertThat(embeddingResponse.getResults()).hasSize(3);
-		assertThat(embeddingResponse.getMetadata()).containsExactlyInAnyOrderEntriesOf(Map.of("transformer",
+		assertThat(embeddingResponse.getMetadata().getRawMap()).containsExactlyInAnyOrderEntriesOf(Map.of("transformer",
 				"distilbert-base-uncased", "vector-type", VectorType.PG_VECTOR.name(), "kwargs", "{}"));
 		assertThat(embeddingResponse.getResults().get(0).getIndex()).isEqualTo(0);
 		assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(768);
@@ -192,7 +207,7 @@ class PostgresMlEmbeddingModelIT {

 		assertThat(embeddingResponse).isNotNull();
 		assertThat(embeddingResponse.getResults()).hasSize(3);
-		assertThat(embeddingResponse.getMetadata()).containsExactlyInAnyOrderEntriesOf(Map.of("transformer",
+		assertThat(embeddingResponse.getMetadata().getRawMap()).containsExactlyInAnyOrderEntriesOf(Map.of("transformer",
 				"intfloat/e5-small", "vector-type", VectorType.PG_ARRAY.name(), "kwargs", "{\"device\":\"cpu\"}"));

 		assertThat(embeddingResponse.getResults().get(0).getIndex()).isEqualTo(0);
--- a/models/spring-ai-stability-ai/src/main/java/org/springframework/ai/stabilityai/StabilityAiImageModel.java
+++ b/models/spring-ai-stability-ai/src/main/java/org/springframework/ai/stabilityai/StabilityAiImageModel.java
@@ -119,7 +119,7 @@ public class StabilityAiImageModel implements ImageModel {
 					new StabilityAiImageGenerationMetadata(entry.finishReason(), entry.seed()));
 		}).toList();

-		return new ImageResponse(imageGenerationList, ImageResponseMetadata.NULL);
+		return new ImageResponse(imageGenerationList, new ImageResponseMetadata());
 	}

 	private StabilityAiImageOptions convertOptions(ImageOptions runtimeOptions) {
--- a/models/spring-ai-transformers/src/test/java/org/springframework/ai/transformers/TransformersEmbeddingModelTests.java
+++ b/models/spring-ai-transformers/src/test/java/org/springframework/ai/transformers/TransformersEmbeddingModelTests.java
@@ -24,6 +24,7 @@ import org.springframework.ai.document.Document;
 import org.springframework.ai.embedding.EmbeddingResponse;

 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertTrue;

 /**
 * @author Christian Tzolov
@@ -76,7 +77,7 @@ public class TransformersEmbeddingModelTests {
 		embeddingModel.afterPropertiesSet();
 		EmbeddingResponse embed = embeddingModel.embedForResponse(List.of("Hello world", "World is big"));
 		assertThat(embed.getResults()).hasSize(2);
-		assertThat(embed.getMetadata()).isEmpty();
+		assertTrue(embed.getMetadata().isEmpty(), "Expected embed metadata to be empty, but it was not.");

 		assertThat(embed.getResults().get(0).getOutput()).hasSize(384);
 		assertThat(DF.format(embed.getResults().get(0).getOutput().get(0))).isEqualTo(DF.format(-0.19744634628295898));
--- a/models/spring-ai-vertex-ai-embedding/src/main/java/org/springframework/ai/vertexai/embedding/VertexAiEmbeddingUsage.java
+++ b/models/spring-ai-vertex-ai-embedding/src/main/java/org/springframework/ai/vertexai/embedding/VertexAiEmbeddingUsage.java
@@ -0,0 +1,28 @@
+package org.springframework.ai.vertexai.embedding;
+
+import org.springframework.ai.chat.metadata.Usage;
+
+public class VertexAiEmbeddingUsage implements Usage {
+
+	private final Integer totalTokens;
+
+	public VertexAiEmbeddingUsage(Integer totalTokens) {
+		this.totalTokens = totalTokens;
+	}
+
+	@Override
+	public Long getPromptTokens() {
+		return 0L;
+	}
+
+	@Override
+	public Long getGenerationTokens() {
+		return 0L;
+	}
+
+	@Override
+	public Long getTotalTokens() {
+		return Long.valueOf(this.totalTokens);
+	}
+
+}
--- a/models/spring-ai-vertex-ai-embedding/src/main/java/org/springframework/ai/vertexai/embedding/multimodal/VertexAiMultimodalEmbeddingModel.java
+++ b/models/spring-ai-vertex-ai-embedding/src/main/java/org/springframework/ai/vertexai/embedding/multimodal/VertexAiMultimodalEmbeddingModel.java
@@ -24,6 +24,7 @@ import com.google.protobuf.Value;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.ai.chat.messages.Media;
+import org.springframework.ai.chat.metadata.Usage;
 import org.springframework.ai.document.Document;
 import org.springframework.ai.embedding.DocumentEmbeddingModel;
 import org.springframework.ai.embedding.DocumentEmbeddingRequest;
@@ -35,6 +36,7 @@ import org.springframework.ai.embedding.EmbeddingResultMetadata;
 import org.springframework.ai.embedding.EmbeddingResultMetadata.ModalityType;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.vertexai.embedding.VertexAiEmbeddigConnectionDetails;
+import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUsage;
 import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUtils;
 import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUtils.ImageBuilder;
 import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUtils.MultimodalInstanceBuilder;
@@ -239,10 +241,11 @@ public class VertexAiMultimodalEmbeddingModel implements DocumentEmbeddingModel

 	}

-	private EmbeddingResponseMetadata generateResponseMetadata(String model, Integer tokenCount) {
+	private EmbeddingResponseMetadata generateResponseMetadata(String model, Integer totalTokens) {
 		EmbeddingResponseMetadata metadata = new EmbeddingResponseMetadata();
-		metadata.put("model", model);
-		metadata.put("total-tokens", tokenCount);
+		metadata.setModel(model);
+		Usage usage = new VertexAiEmbeddingUsage(totalTokens);
+		metadata.setUsage(usage);
 		return metadata;
 	}

--- a/models/spring-ai-vertex-ai-embedding/src/main/java/org/springframework/ai/vertexai/embedding/text/VertexAiTextEmbeddingModel.java
+++ b/models/spring-ai-vertex-ai-embedding/src/main/java/org/springframework/ai/vertexai/embedding/text/VertexAiTextEmbeddingModel.java
@@ -20,6 +20,7 @@ import com.google.cloud.aiplatform.v1.PredictRequest;
 import com.google.cloud.aiplatform.v1.PredictResponse;
 import com.google.cloud.aiplatform.v1.PredictionServiceClient;
 import com.google.protobuf.Value;
+import org.springframework.ai.chat.metadata.Usage;
 import org.springframework.ai.document.Document;
 import org.springframework.ai.embedding.AbstractEmbeddingModel;
 import org.springframework.ai.embedding.Embedding;
@@ -32,6 +33,7 @@ import org.springframework.ai.vertexai.embedding.VertexAiEmbeddigConnectionDetai
 import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUtils;
 import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUtils.TextInstanceBuilder;
 import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUtils.TextParametersBuilder;
+import org.springframework.ai.vertexai.embedding.VertexAiEmbeddingUsage;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;

@@ -135,10 +137,11 @@ public class VertexAiTextEmbeddingModel extends AbstractEmbeddingModel {
 		}
 	}

-	private EmbeddingResponseMetadata generateResponseMetadata(String model, Integer tokenCount) {
+	private EmbeddingResponseMetadata generateResponseMetadata(String model, Integer totalTokens) {
 		EmbeddingResponseMetadata metadata = new EmbeddingResponseMetadata();
-		metadata.put("model", model);
-		metadata.put("total-tokens", tokenCount);
+		metadata.setModel(model);
+		Usage usage = new VertexAiEmbeddingUsage(totalTokens);
+		metadata.setUsage(usage);
 		return metadata;
 	}

--- a/models/spring-ai-vertex-ai-embedding/src/test/java/org/springframework/ai/vertexai/embedding/multimodal/VertexAiMultimodelEmbeddingModelIT.java
+++ b/models/spring-ai-vertex-ai-embedding/src/test/java/org/springframework/ai/vertexai/embedding/multimodal/VertexAiMultimodelEmbeddingModelIT.java
@@ -68,8 +68,13 @@ class VertexAiMultimodelEmbeddingModelIT {
 			.isEqualTo(embeddingRequest.getInstructions().get(1).getId());
 		assertThat(embeddingResponse.getResults().get(1).getOutput()).hasSize(1408);

-		assertThat(embeddingResponse.getMetadata()).containsEntry("model", "multimodalembedding@001");
-		assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 0);
+		assertThat(embeddingResponse.getMetadata().getModel())
+			.as("Model in metadata should be 'multimodalembedding@001'")
+			.isEqualTo("multimodalembedding@001");
+
+		assertThat(embeddingResponse.getMetadata().getUsage().getTotalTokens())
+			.as("Total tokens in metadata should be 0")
+			.isEqualTo("0");

 		assertThat(multiModelEmbeddingModel.dimensions()).isEqualTo(1408);
 	}
@@ -90,8 +95,8 @@ class VertexAiMultimodelEmbeddingModelIT {
 			.isEqualTo(MimeTypeUtils.TEXT_PLAIN);
 		assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(1408);

-		assertThat(embeddingResponse.getMetadata()).containsEntry("model", "multimodalembedding@001");
-		assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 0);
+		assertThat(embeddingResponse.getMetadata().getModel()).isEqualTo("multimodalembedding@001");
+		assertThat(embeddingResponse.getMetadata().getUsage()).isEqualTo(0);

 		assertThat(multiModelEmbeddingModel.dimensions()).isEqualTo(1408);
 	}
@@ -113,8 +118,8 @@ class VertexAiMultimodelEmbeddingModelIT {
 			.isEqualTo(MimeTypeUtils.TEXT_PLAIN);
 		assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(1408);

-		assertThat(embeddingResponse.getMetadata()).containsEntry("model", "multimodalembedding@001");
-		assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 0);
+		assertThat(embeddingResponse.getMetadata().getModel()).isEqualTo("multimodalembedding@001");
+		assertThat(embeddingResponse.getMetadata().getUsage().getTotalTokens()).isEqualTo(0);

 		assertThat(multiModelEmbeddingModel.dimensions()).isEqualTo(1408);
 	}
@@ -139,8 +144,8 @@ class VertexAiMultimodelEmbeddingModelIT {

 		assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(1408);

-		assertThat(embeddingResponse.getMetadata()).containsEntry("model", "multimodalembedding@001");
-		assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 0);
+		assertThat(embeddingResponse.getMetadata().getModel()).isEqualTo("multimodalembedding@001");
+		assertThat(embeddingResponse.getMetadata().getUsage().getTotalTokens()).isEqualTo(0);

 		assertThat(multiModelEmbeddingModel.dimensions()).isEqualTo(1408);
 	}
@@ -164,8 +169,8 @@ class VertexAiMultimodelEmbeddingModelIT {
 			.isEqualTo(new MimeType("video", "mp4"));
 		assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(1408);

-		assertThat(embeddingResponse.getMetadata()).containsEntry("model", "multimodalembedding@001");
-		assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 0);
+		assertThat(embeddingResponse.getMetadata().getModel()).isEqualTo("multimodalembedding@001");
+		assertThat(embeddingResponse.getMetadata().getUsage().getTotalTokens()).isEqualTo(0);

 		assertThat(multiModelEmbeddingModel.dimensions()).isEqualTo(1408);
 	}
@@ -198,8 +203,8 @@ class VertexAiMultimodelEmbeddingModelIT {
 			.isEqualTo(EmbeddingResultMetadata.ModalityType.VIDEO);
 		assertThat(embeddingResponse.getResults().get(2).getOutput()).hasSize(1408);

-		assertThat(embeddingResponse.getMetadata()).containsEntry("model", "multimodalembedding@001");
-		assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 0);
+		assertThat(embeddingResponse.getMetadata().getModel()).isEqualTo("multimodalembedding@001");
+		assertThat(embeddingResponse.getMetadata().getUsage()).isEqualTo(0);

 		assertThat(multiModelEmbeddingModel.dimensions()).isEqualTo(1408);
 	}
--- a/models/spring-ai-vertex-ai-embedding/src/test/java/org/springframework/ai/vertexai/embedding/text/VertexAiTextEmbeddingModelIT.java
+++ b/models/spring-ai-vertex-ai-embedding/src/test/java/org/springframework/ai/vertexai/embedding/text/VertexAiTextEmbeddingModelIT.java
@@ -53,8 +53,12 @@ class VertexAiTextEmbeddingModelIT {
 		assertThat(embeddingResponse.getResults()).hasSize(2);
 		assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(768);
 		assertThat(embeddingResponse.getResults().get(1).getOutput()).hasSize(768);
-		assertThat(embeddingResponse.getMetadata()).containsEntry("model", modelName);
-		assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 5);
+		assertThat(embeddingResponse.getMetadata().getModel()).as("Model name in metadata should match expected model")
+			.isEqualTo(modelName);
+
+		assertThat(embeddingResponse.getMetadata().getUsage().getTotalTokens())
+			.as("Total tokens in metadata should be 5")
+			.isEqualTo(5L);

 		assertThat(embeddingModel.dimensions()).isEqualTo(768);
 	}
--- a/models/spring-ai-vertex-ai-gemini/src/main/java/org/springframework/ai/vertexai/gemini/VertexAiGeminiChatModel.java
+++ b/models/spring-ai-vertex-ai-gemini/src/main/java/org/springframework/ai/vertexai/gemini/VertexAiGeminiChatModel.java
@@ -29,6 +29,7 @@ import org.springframework.ai.chat.messages.MessageType;
 import org.springframework.ai.chat.messages.SystemMessage;
 import org.springframework.ai.chat.messages.ToolResponseMessage;
 import org.springframework.ai.chat.messages.UserMessage;
+import org.springframework.ai.chat.metadata.ChatResponseMetadata;
 import org.springframework.ai.chat.model.ChatModel;
 import org.springframework.ai.chat.model.ChatResponse;
 import org.springframework.ai.chat.model.Generation;
@@ -38,7 +39,7 @@ import org.springframework.ai.model.ChatModelDescription;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.AbstractToolCallSupport;
 import org.springframework.ai.model.function.FunctionCallbackContext;
-import org.springframework.ai.vertexai.gemini.metadata.VertexAiChatResponseMetadata;
+import org.springframework.ai.vertexai.gemini.metadata.VertexAiChatResponseMetadataUtils;
 import org.springframework.ai.vertexai.gemini.metadata.VertexAiUsage;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.lang.NonNull;
@@ -244,8 +245,8 @@ public class VertexAiGeminiChatModel extends AbstractToolCallSupport<GenerateCon
 		}
 	}

-	private VertexAiChatResponseMetadata toChatResponseMetadata(GenerateContentResponse response) {
-		return new VertexAiChatResponseMetadata(new VertexAiUsage(response.getUsageMetadata()));
+	private ChatResponseMetadata toChatResponseMetadata(GenerateContentResponse response) {
+		return VertexAiChatResponseMetadataUtils.from(response.getUsageMetadata());
 	}

 	@JsonInclude(Include.NON_NULL)
--- a/models/spring-ai-vertex-ai-gemini/src/main/java/org/springframework/ai/vertexai/gemini/metadata/VertexAiChatResponseMetadataUtils.java
+++ b/models/spring-ai-vertex-ai-gemini/src/main/java/org/springframework/ai/vertexai/gemini/metadata/VertexAiChatResponseMetadataUtils.java
@@ -15,8 +15,10 @@
 */
 package org.springframework.ai.vertexai.gemini.metadata;

+import com.google.cloud.vertexai.api.GenerateContentResponse;
 import org.springframework.ai.chat.metadata.ChatResponseMetadata;
 import org.springframework.ai.chat.metadata.Usage;
+import org.springframework.util.Assert;

 import java.util.HashMap;

@@ -24,17 +26,11 @@ import java.util.HashMap;
 * @author Christian Tzolov
 * @since 0.8.1
 */
-public class VertexAiChatResponseMetadata extends HashMap<String, Object> implements ChatResponseMetadata {
+public abstract class VertexAiChatResponseMetadataUtils {

-	private final VertexAiUsage usage;
-
-	public VertexAiChatResponseMetadata(VertexAiUsage usage) {
-		this.usage = usage;
-	}
-
-	@Override
-	public Usage getUsage() {
-		return this.usage;
+	public static ChatResponseMetadata from(GenerateContentResponse.UsageMetadata usageMetadata) {
+		Assert.notNull(usageMetadata, "GenerateContentResponse.UsageMetadata must not be null");
+		return ChatResponseMetadata.builder().withUsage(new VertexAiUsage(usageMetadata)).build();
 	}

 }
--- a/spring-ai-core/src/main/java/org/springframework/ai/chat/metadata/ChatResponseMetadata.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/chat/metadata/ChatResponseMetadata.java
@@ -15,40 +15,46 @@
 */
 package org.springframework.ai.chat.metadata;

-import org.springframework.ai.model.ResponseMetadata;
+import org.springframework.ai.model.MutableResponseMetadata;

-import java.util.HashMap;
+import java.util.Objects;

 /**
- * Abstract Data Type (ADT) modeling common AI provider metadata returned in an AI
- * response.
+ * Models common AI provider metadata returned in an AI response.
 *
 * @author John Blum
 * @author Thomas Vitale
 * @since 0.7.0
 */
-public interface ChatResponseMetadata extends ResponseMetadata {
+public class ChatResponseMetadata extends MutableResponseMetadata {

-	class DefaultChatResponseMetadata extends HashMap<String, Object> implements ChatResponseMetadata {
+	private static final String AI_METADATA_STRING = "{ id: %2$s, usage: %3$s, rateLimit: %4$s }";

-	}
+	private String id = ""; // Set to blank to preserve backward compat with previous
+							// interface default methods

-	ChatResponseMetadata NULL = new DefaultChatResponseMetadata();
+	private String model = "";
+
+	private RateLimit rateLimit = new EmptyRateLimit();
+
+	private Usage usage = new EmptyUsage();
+
+	private PromptMetadata promptMetadata = PromptMetadata.empty();

 	/**
 	 * A unique identifier for the chat completion operation.
 	 * @return unique operation identifier.
 	 */
-	default String getId() {
-		return "";
+	public String getId() {
+		return this.id;
 	}

 	/**
 	 * The model that handled the request.
 	 * @return the model that handled the request.
 	 */
-	default String getModel() {
-		return "";
+	public String getModel() {
+		return this.model;
 	}

 	/**
@@ -56,8 +62,8 @@ public interface ChatResponseMetadata extends ResponseMetadata {
 	 * @return AI provider specific metadata on rate limits.
 	 * @see RateLimit
 	 */
-	default RateLimit getRateLimit() {
-		return new EmptyRateLimit();
+	public RateLimit getRateLimit() {
+		return this.rateLimit;
 	}

 	/**
@@ -65,12 +71,85 @@ public interface ChatResponseMetadata extends ResponseMetadata {
 	 * @return AI provider specific metadata on API usage.
 	 * @see Usage
 	 */
-	default Usage getUsage() {
-		return new EmptyUsage();
+	public Usage getUsage() {
+		return this.usage;
 	}

-	default PromptMetadata getPromptMetadata() {
-		return PromptMetadata.empty();
+	/**
+	 * Returns the prompt metadata gathered by the AI during request processing.
+	 * @return the prompt metadata.
+	 */
+	public PromptMetadata getPromptMetadata() {
+		return this.promptMetadata;
+	}
+
+	public static class Builder {
+
+		private final ChatResponseMetadata chatResponseMetadata;
+
+		public Builder() {
+			this.chatResponseMetadata = new ChatResponseMetadata();
+		}
+
+		public Builder withKeyValue(String key, Object value) {
+			this.chatResponseMetadata.put(key, value);
+			return this;
+		}
+
+		public Builder withId(String id) {
+			this.chatResponseMetadata.id = id;
+			return this;
+		}
+
+		public Builder withModel(String model) {
+			this.chatResponseMetadata.model = model;
+			return this;
+		}
+
+		public Builder withRateLimit(RateLimit rateLimit) {
+			this.chatResponseMetadata.rateLimit = rateLimit;
+			return this;
+		}
+
+		public Builder withUsage(Usage usage) {
+			this.chatResponseMetadata.usage = usage;
+			return this;
+		}
+
+		public Builder withPromptMetadata(PromptMetadata promptMetadata) {
+			this.chatResponseMetadata.promptMetadata = promptMetadata;
+			return this;
+		}
+
+		public ChatResponseMetadata build() {
+			return this.chatResponseMetadata;
+		}
+
+	}
+
+	public static Builder builder() {
+		return new Builder();
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o)
+			return true;
+		if (!(o instanceof ChatResponseMetadata that))
+			return false;
+		return Objects.equals(id, that.id) && Objects.equals(model, that.model)
+				&& Objects.equals(rateLimit, that.rateLimit) && Objects.equals(usage, that.usage)
+				&& Objects.equals(promptMetadata, that.promptMetadata);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(id, model, rateLimit, usage, promptMetadata);
+	}
+
+	@Override
+	public String toString() {
+		return AI_METADATA_STRING.formatted(getId(), getUsage(), getRateLimit());
 	}

 }
--- a/spring-ai-core/src/main/java/org/springframework/ai/chat/model/ChatResponse.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/chat/model/ChatResponse.java
@@ -40,7 +40,7 @@ public class ChatResponse implements ModelResponse<Generation> {
 	 * provider.
 	 */
 	public ChatResponse(List<Generation> generations) {
-		this(generations, ChatResponseMetadata.NULL);
+		this(generations, new ChatResponseMetadata());
 	}

 	/**
--- a/spring-ai-core/src/main/java/org/springframework/ai/embedding/EmbeddingResponseMetadata.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/embedding/EmbeddingResponseMetadata.java
@@ -21,6 +21,7 @@ import java.util.Map;

 import org.springframework.ai.chat.metadata.EmptyUsage;
 import org.springframework.ai.chat.metadata.Usage;
+import org.springframework.ai.model.MutableResponseMetadata;
 import org.springframework.ai.model.ResponseMetadata;

 /**
@@ -29,10 +30,7 @@ import org.springframework.ai.model.ResponseMetadata;
 * @author Christian Tzolov
 * @author Thomas Vitale
 */
-public class EmbeddingResponseMetadata extends HashMap<String, Object> implements ResponseMetadata {
-
-	@Serial
-	private static final long serialVersionUID = 1L;
+public class EmbeddingResponseMetadata extends MutableResponseMetadata {

 	private String model;

@@ -42,12 +40,15 @@ public class EmbeddingResponseMetadata extends HashMap<String, Object> implement
 	}

 	public EmbeddingResponseMetadata(String model, Usage usage) {
-		this.model = model;
-		this.usage = usage;
+		this(model, usage, Map.of());
 	}

-	public EmbeddingResponseMetadata(Map<String, ?> metadata) {
-		super(metadata);
+	public EmbeddingResponseMetadata(String model, Usage usage, Map<String, Object> metadata) {
+		this.model = model;
+		this.usage = usage;
+		for (Map.Entry<String, Object> entry : metadata.entrySet()) {
+			this.put(entry.getKey(), entry.getValue());
+		}
 	}

 	/**
--- a/spring-ai-core/src/main/java/org/springframework/ai/image/ImageResponse.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/image/ImageResponse.java
@@ -43,7 +43,7 @@ public class ImageResponse implements ModelResponse<ImageGeneration> {
 	 * provider.
 	 */
 	public ImageResponse(List<ImageGeneration> generations) {
-		this(generations, ImageResponseMetadata.NULL);
+		this(generations, new ImageResponseMetadata());
 	}

 	/**
--- a/spring-ai-core/src/main/java/org/springframework/ai/image/ImageResponseMetadata.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/image/ImageResponseMetadata.java
@@ -15,6 +15,7 @@
 */
 package org.springframework.ai.image;

+import org.springframework.ai.model.MutableResponseMetadata;
 import org.springframework.ai.model.ResponseMetadata;

 import java.util.HashMap;
@@ -28,16 +29,20 @@ import java.util.HashMap;
 * @author Thomas Vitale
 * @since 1.0.0
 */
-public interface ImageResponseMetadata extends ResponseMetadata {
+public class ImageResponseMetadata extends MutableResponseMetadata {

-	class DefaultImageResponseMetadata extends HashMap<String, Object> implements ImageResponseMetadata {
+	private Long created;

+	public ImageResponseMetadata() {
+		this.created = System.currentTimeMillis();
 	}

-	ImageResponseMetadata NULL = new DefaultImageResponseMetadata();
+	public ImageResponseMetadata(Long created) {
+		this.created = created;
+	}

-	default Long getCreated() {
-		return System.currentTimeMillis();
+	public Long getCreated() {
+		return this.created;
 	}

 }
--- a/spring-ai-core/src/main/java/org/springframework/ai/model/MutableResponseMetadata.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/model/MutableResponseMetadata.java
@@ -0,0 +1,115 @@
+package org.springframework.ai.model;
+
+import io.micrometer.common.lang.NonNull;
+import io.micrometer.common.lang.Nullable;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Function;
+
+public class MutableResponseMetadata implements ResponseMetadata {
+
+	private final Map<String, Object> map = new ConcurrentHashMap<>();
+
+	/**
+	 * Puts an element to the context.
+	 * @param key key
+	 * @param object value
+	 * @param <T> value type
+	 * @return this for chaining
+	 */
+	public <T> MutableResponseMetadata put(String key, T object) {
+		this.map.put(key, object);
+		return this;
+	}
+
+	/**
+	 * Gets an entry from the context. Returns {@code null} when entry is not present.
+	 * @param key key
+	 * @param <T> value type
+	 * @return entry or {@code null} if not present
+	 */
+	@Override
+	@Nullable
+	public <T> T get(String key) {
+		return (T) this.map.get(key);
+	}
+
+	/**
+	 * Removes an entry from the context.
+	 * @param key key by which to remove an entry
+	 * @return the previous value associated with the key, or null if there was no mapping
+	 * for the key
+	 */
+	public Object remove(Object key) {
+		return this.map.remove(key);
+	}
+
+	/**
+	 * Gets an entry from the context. Throws exception when entry is not present.
+	 * @param key key
+	 * @param <T> value type
+	 * @throws IllegalArgumentException if not present
+	 * @return entry
+	 */
+	@Override
+	@NonNull
+	public <T> T getRequired(Object key) {
+		T object = (T) this.map.get(key);
+		if (object == null) {
+			throw new IllegalArgumentException("Context does not have an entry for key [" + key + "]");
+		}
+		return object;
+	}
+
+	/**
+	 * Checks if context contains a key.
+	 * @param key key
+	 * @return {@code true} when the context contains the entry with the given key
+	 */
+	@Override
+	public boolean containsKey(Object key) {
+		return this.map.containsKey(key);
+	}
+
+	/**
+	 * Returns an element or default if not present.
+	 * @param key key
+	 * @param defaultObject default object to return
+	 * @param <T> value type
+	 * @return object or default if not present
+	 */
+	@Override
+	public <T> T getOrDefault(Object key, T defaultObject) {
+		return (T) this.map.getOrDefault(key, defaultObject);
+	}
+
+	@Override
+	public boolean isEmpty() {
+		return this.map.isEmpty();
+	}
+
+	/**
+	 * Returns an element or calls a mapping function if entry not present. The function
+	 * will insert the value to the map.
+	 * @param key key
+	 * @param mappingFunction mapping function
+	 * @param <T> value type
+	 * @return object or one derived from the mapping function if not present
+	 */
+	public <T> T computeIfAbsent(String key, Function<Object, ? extends T> mappingFunction) {
+		return (T) this.map.computeIfAbsent(key, mappingFunction);
+	}
+
+	/**
+	 * Clears the entries from the context.
+	 */
+	public void clear() {
+		this.map.clear();
+	}
+
+	public Map<String, Object> getRawMap() {
+		return map;
+	}
+
+}
--- a/spring-ai-core/src/main/java/org/springframework/ai/model/ResponseMetadata.java
+++ b/spring-ai-core/src/main/java/org/springframework/ai/model/ResponseMetadata.java
@@ -15,7 +15,11 @@
 */
 package org.springframework.ai.model;

-import java.util.Map;
+import io.micrometer.common.KeyValues;
+import io.micrometer.common.lang.NonNull;
+import io.micrometer.common.lang.Nullable;
+
+import java.util.function.Supplier;

 /**
 * Interface representing metadata associated with an AI model's response. This interface
@@ -27,6 +31,60 @@ import java.util.Map;
 * @author Mark Pollack
 * @since 0.8.0
 */
-public interface ResponseMetadata extends Map<String, Object> {
+public interface ResponseMetadata {
+
+	/**
+	 * Gets an entry from the context. Returns {@code null} when entry is not present.
+	 * @param key key
+	 * @param <T> value type
+	 * @return entry or {@code null} if not present
+	 */
+	@Nullable
+	<T> T get(String key);
+
+	/**
+	 * Gets an entry from the context. Throws exception when entry is not present.
+	 * @param key key
+	 * @param <T> value type
+	 * @throws IllegalArgumentException if not present
+	 * @return entry
+	 */
+	@NonNull
+	<T> T getRequired(Object key);
+
+	/**
+	 * Checks if context contains a key.
+	 * @param key key
+	 * @return {@code true} when the context contains the entry with the given key
+	 */
+	boolean containsKey(Object key);
+
+	/**
+	 * Returns an element or default if not present.
+	 * @param key key
+	 * @param defaultObject default object to return
+	 * @param <T> value type
+	 * @return object or default if not present
+	 */
+	<T> T getOrDefault(Object key, T defaultObject);
+
+	/**
+	 * Returns an element or default if not present.
+	 * @param key key
+	 * @param defaultObjectSupplier supplier for default object to return
+	 * @param <T> value type
+	 * @return object or default if not present
+	 * @since 1.11.0
+	 */
+	default <T> T getOrDefault(String key, Supplier<T> defaultObjectSupplier) {
+		T value = get(key);
+		return value != null ? value : defaultObjectSupplier.get();
+	}
+
+	/**
+	 * Returns {@code true} if this map contains no key-value mappings.
+	 * @return {@code true} if this map contains no key-value mappings
+	 */
+	boolean isEmpty();

 }
--- a/spring-ai-core/src/test/java/org/springframework/ai/chat/client/ChatClientResponseEntityTests.java
+++ b/spring-ai-core/src/test/java/org/springframework/ai/chat/client/ChatClientResponseEntityTests.java
@@ -29,7 +29,6 @@ import org.mockito.junit.jupiter.MockitoExtension;
 import org.springframework.ai.chat.messages.Message;
 import org.springframework.ai.chat.messages.MessageType;
 import org.springframework.ai.chat.metadata.ChatResponseMetadata;
-import org.springframework.ai.chat.metadata.ChatResponseMetadata.DefaultChatResponseMetadata;
 import org.springframework.ai.chat.model.ChatModel;
 import org.springframework.ai.chat.model.ChatResponse;
 import org.springframework.ai.chat.model.Generation;
@@ -58,7 +57,7 @@ public class ChatClientResponseEntityTests {
 	@Test
 	public void responseEntityTest() {

-		ChatResponseMetadata metadata = new DefaultChatResponseMetadata();
+		ChatResponseMetadata metadata = new ChatResponseMetadata();
 		metadata.put("key1", "value1");

 		var chatResponse = new ChatResponse(List.of(new Generation("""
@@ -75,7 +74,7 @@ public class ChatClientResponseEntityTests {
 			.responseEntity(MyBean.class);

 		assertThat(responseEntity.getResponse()).isEqualTo(chatResponse);
-		assertThat(responseEntity.getResponse().getMetadata().get("key1")).isEqualTo("value1");
+		assertThat(responseEntity.getResponse().getMetadata().get("key1").toString()).isEqualTo("value1");

 		assertThat(responseEntity.getEntity()).isEqualTo(new MyBean("John", 30));

--- a/spring-ai-spring-boot-autoconfigure/src/test/java/org/springframework/ai/autoconfigure/vertexai/embedding/VertexAiTextEmbeddingModelAutoConfigurationIT.java
+++ b/spring-ai-spring-boot-autoconfigure/src/test/java/org/springframework/ai/autoconfigure/vertexai/embedding/VertexAiTextEmbeddingModelAutoConfigurationIT.java
@@ -112,8 +112,8 @@ public class VertexAiTextEmbeddingModelAutoConfigurationIT {
 				.isEqualTo(EmbeddingResultMetadata.ModalityType.TEXT);
 			assertThat(embeddingResponse.getResults().get(0).getOutput()).hasSize(1408);

-			assertThat(embeddingResponse.getMetadata()).containsEntry("model", "multimodalembedding@001");
-			assertThat(embeddingResponse.getMetadata()).containsEntry("total-tokens", 0);
+			assertThat(embeddingResponse.getMetadata().getModel()).isEqualTo("multimodalembedding@001");
+			assertThat(embeddingResponse.getMetadata().getUsage()).isEqualTo(0);

 			assertThat(multiModelEmbeddingModel.dimensions()).isEqualTo(1408);