Include thinking text in Anthropic streaming chunks

models/spring-ai-anthropic/src/main/java/org/springframework/ai/anthropic/AnthropicChatModel.java

@@ -440,12 +440,14 @@ else if (contentBlock.isWebSearchToolResult()) {
 				return null;
 			}
 
-			// Thinking chunk — emit with thinking metadata
+			// Thinking chunk — emit with thinking metadata. The text is exposed in
+			// metadata, not content, so it is not aggregated into the message text.
 			if (delta.isThinking()) {
 				String thinkingText = delta.asThinking().thinking();
 				streamingState.appendThinking(thinkingText);
 				Map<String, Object> thinkingProperties = new HashMap<>();
 				thinkingProperties.put("thinking", Boolean.TRUE);
+				thinkingProperties.put("thinkingText", thinkingText);
 				AssistantMessage assistantMessage = AssistantMessage.builder().properties(thinkingProperties).build();
 				return new ChatResponse(List.of(new Generation(assistantMessage)));
 			}

models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/AnthropicChatModelTests.java

@@ -393,6 +393,37 @@ void streamingThinkingBlockIsReplayedBeforeToolUseBlock() {
 		assertThat(replayedAssistantBlocks.get(1).isToolUse()).isTrue();
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	void streamingThinkingDeltasExposeThinkingTextInMetadata() {
+		List<RawMessageStreamEvent> events = List.of(messageStartEvent(), thinkingStartEvent(),
+				thinkingDeltaEvent("thinking "), thinkingDeltaEvent("text"), signatureDeltaEvent("thinking-signature"),
+				contentBlockStopEvent(0), messageDeltaEvent(StopReason.END_TURN));
+		StreamResponse<RawMessageStreamEvent> streamResponse = mock(StreamResponse.class);
+		given(streamResponse.stream()).willReturn(events.stream());
+
+		HttpResponseFor<StreamResponse<RawMessageStreamEvent>> rawResponse = mock(HttpResponseFor.class);
+		given(rawResponse.parse()).willReturn(streamResponse);
+		given(rawResponse.headers()).willReturn(Headers.builder().build());
+
+		given(this.anthropicClientAsync.messages()).willReturn(this.messageServiceAsync);
+		given(this.messageServiceAsync.withRawResponse()).willReturn(this.messageServiceAsyncWithRawResponse);
+		given(this.messageServiceAsyncWithRawResponse.createStreaming(any(MessageCreateParams.class),
+				any(RequestOptions.class)))
+			.willReturn(CompletableFuture.completedFuture(rawResponse));
+
+		List<ChatResponse> responses = this.chatModel.stream(new Prompt("Think about it.")).collectList().block();
+
+		assertThat(responses).isNotNull();
+		List<AssistantMessage> thinkingDeltas = responses.stream()
+			.map(response -> response.getResult().getOutput())
+			.filter(message -> message.getMetadata().containsKey("thinking"))
+			.toList();
+		assertThat(thinkingDeltas).extracting(message -> message.getMetadata().get("thinkingText"))
+			.containsExactly("thinking ", "text");
+		assertThat(thinkingDeltas).allSatisfy(message -> assertThat(message.getText()).isNull());
+	}
+
 	@Test
 	void cacheOptionsIsMergedFromRuntimePrompt() {
 		AnthropicChatModel model = AnthropicChatModel.builder()

spring-ai-docs/src/main/antora/modules/ROOT/pages/api/chat/anthropic-chat.adoc

@@ -485,10 +485,9 @@ stream.subscribe(response -> {
     AssistantMessage message = generation.getOutput();
 
     if (message.getMetadata().containsKey("thinking")) {
-        // Thinking delta — getText() returns null; the full accumulated thinking text
-        // is available via AnthropicAssistantMessage.getThinkingContents() on the
-        // aggregated response after streaming completes.
-        System.out.println("[thinking...]");
+        // Thinking delta — getText() returns null so thinking does not mix into the
+        // answer; the incremental thinking text is in the "thinkingText" metadata key.
+        System.out.print(message.getMetadata().get("thinkingText"));
     }
     else if (message.getMetadata().containsKey("signature")) {
         // Thinking block signature (emitted at end of thinking)
@@ -512,7 +511,7 @@ When thinking is enabled, the response contains different types of content:
 | **Thinking Block** | `signature` | Claude's reasoning text with a cryptographic signature. In sync mode, the thinking text is in `getText()` and the signature is in `getMetadata().get("signature")`.
 | **Redacted Thinking** | `data` | Safety-redacted reasoning. Contains only a `data` marker, no visible text.
 | **Signature (streaming)** | `signature` | In streaming mode, the signature arrives as a separate delta at the end of a thinking block.
-| **Thinking Delta (streaming)** | `thinking` | Incremental thinking chunks during streaming. The `thinking` metadata key is set to `true`. `getText()` returns null on these chunks; the full thinking text is available via `AnthropicAssistantMessage.getThinkingContents()` on the aggregated response.
+| **Thinking Delta (streaming)** | `thinking`, `thinkingText` | Incremental thinking chunks during streaming. The `thinking` metadata key is set to `true` and `thinkingText` holds the incremental thinking text. `getText()` returns null on these chunks, so thinking is not aggregated into the answer text; the full thinking text is also available via `AnthropicAssistantMessage.getThinkingContents()` on the aggregated response.
 | **Text Block** | _(none)_ | The final answer text in `getText()`.
 |====