fix: require line-start anchor in thinking section title pattern to prevent ghost sections

Author: xinyi-gong

com.microsoft.copilot.eclipse.ui.test/src/com/microsoft/copilot/eclipse/ui/chat/ThinkingBlockParseTest.java

@@ -62,6 +62,49 @@ void parseSections_handlesLfOnlyTitleBoundary() throws Exception {
     assertEquals("plan body", body(sections.get(1)));
   }
 
+  @Test
+  void parseSections_inlineBoldNotTreatedAsTitle() throws Exception {
+    // Inline bold at end of string should NOT be parsed as a section title.
+    String raw = "combined with **The Ship of Theseus**";
+    List<?> sections = invokeParseSections(raw);
+    assertEquals(1, sections.size());
+    assertNull(title(sections.get(0)));
+    assertEquals("combined with **The Ship of Theseus**", body(sections.get(0)));
+  }
+
+  @Test
+  void parseSections_inlineBoldFollowedByText() throws Exception {
+    // Inline bold mid-line should remain as body text.
+    String raw = "text with **bold** and more text";
+    List<?> sections = invokeParseSections(raw);
+    assertEquals(1, sections.size());
+    assertNull(title(sections.get(0)));
+    assertEquals("text with **bold** and more text", body(sections.get(0)));
+  }
+
+  @Test
+  void parseSections_mixOfInlineBoldAndStandaloneTitle() throws Exception {
+    // Inline bold on one line, standalone title on next line.
+    String raw = "text with **inline bold** here\n**Standalone Title**\nbody after title";
+    List<?> sections = invokeParseSections(raw);
+    assertEquals(2, sections.size());
+    assertNull(title(sections.get(0)));
+    assertEquals("text with **inline bold** here", body(sections.get(0)));
+    assertEquals("Standalone Title", title(sections.get(1)));
+    assertEquals("body after title", body(sections.get(1)));
+  }
+
+  @Test
+  void parseSections_titleAtStartOfText() throws Exception {
+    String raw = "**First**\nbody one\n**Second**\nbody two";
+    List<?> sections = invokeParseSections(raw);
+    assertEquals(2, sections.size());
+    assertEquals("First", title(sections.get(0)));
+    assertEquals("body one", body(sections.get(0)));
+    assertEquals("Second", title(sections.get(1)));
+    assertEquals("body two", body(sections.get(1)));
+  }
+
   private static String invokeStripTrailingNewlines(String input) throws Exception {
     Method m = ThinkingBlock.class.getDeclaredMethod("stripTrailingNewlines", String.class);
     m.setAccessible(true);

com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/ThinkingBlock.java

@@ -34,7 +34,8 @@
  */
 public class ThinkingBlock extends Composite {
   private static final String SECONDARY_TEXT_CSS_CLASS = "text-secondary";
-  private static final Pattern TITLE_PATTERN = Pattern.compile("\\*\\*([^*\\r\\n]+?)\\*\\*(?=\\r?\\n|$)");
+  private static final Pattern TITLE_PATTERN =
+      Pattern.compile("(?:^|\\n)\\*\\*([^*\\r\\n]+?)\\*\\*(?=\\r?\\n|$)");
 
   private Composite header;
   private Label iconLabel;