diff --git a/langchain4j-http-client/src/main/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParser.java b/langchain4j-http-client/src/main/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParser.java
index 271c0a0dd4..c7988c3f64 100644
--- a/langchain4j-http-client/src/main/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParser.java
+++ b/langchain4j-http-client/src/main/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParser.java
@@ -36,10 +36,15 @@ public class DefaultServerSentEventParser implements ServerSentEventParser {
                     event = line.substring("event:".length()).trim();
                 } else if (line.startsWith("data:")) {
                     String content = line.substring("data:".length());
+                    // Per the WHATWG HTML Living Standard (Server-sent events), if the field value
+                    // starts with a single U+0020 SPACE, only that one space is removed.
+                    if (content.startsWith(" ")) {
+                        content = content.substring(1);
+                    }
                     if (!data.isEmpty()) {
                         data.append("\n");
                     }
-                    data.append(content.trim());
+                    data.append(content);
                 }
             }
 
diff --git a/langchain4j-http-client/src/test/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParserTest.java b/langchain4j-http-client/src/test/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParserTest.java
index ec5212c98e..25d093a90f 100644
--- a/langchain4j-http-client/src/test/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParserTest.java
+++ b/langchain4j-http-client/src/test/java/dev/langchain4j/http/client/sse/DefaultServerSentEventParserTest.java
@@ -130,6 +130,48 @@ class DefaultServerSentEventParserTest {
         verify(listener, never()).onEvent(any());
     }
 
+    @Test
+    void shouldPreserveAdditionalLeadingWhitespaceInData() {
+
+        // given
+        String input = "data:   indented\n\n";
+        InputStream stream = new ByteArrayInputStream(input.getBytes(UTF_8));
+
+        // when
+        parser.parse(stream, listener);
+
+        // then
+        verify(listener).onEvent(eq(new ServerSentEvent(null, "  indented")), any());
+    }
+
+    @Test
+    void shouldPreserveTrailingWhitespaceInData() {
+
+        // given
+        String input = "data: trailing  \n\n";
+        InputStream stream = new ByteArrayInputStream(input.getBytes(UTF_8));
+
+        // when
+        parser.parse(stream, listener);
+
+        // then
+        verify(listener).onEvent(eq(new ServerSentEvent(null, "trailing  ")), any());
+    }
+
+    @Test
+    void shouldNotRemoveAnyCharacterWhenDataHasNoLeadingSpace() {
+
+        // given
+        String input = "data:nospace\n\n";
+        InputStream stream = new ByteArrayInputStream(input.getBytes(UTF_8));
+
+        // when
+        parser.parse(stream, listener);
+
+        // then
+        verify(listener).onEvent(eq(new ServerSentEvent(null, "nospace")), any());
+    }
+
     @Test
     void shouldHandleIOException() {