diff --git a/gui/main.qml b/gui/main.qml
index 690e628..aadc675 100644
--- a/gui/main.qml
+++ b/gui/main.qml
@@ -622,7 +622,7 @@ ApplicationWindow {
             Text {
                 id: callText
                 Layout.fillWidth: true
-                text: visible ? chatModel.prettyJson(block.blockContent) : ""
+                text: visible ? chatModel.prettyJson(block.blockContent || "") : ""
                 textFormat: Text.RichText
                 wrapMode: Text.Wrap
                 font.family: "monospace"
@@ -653,8 +653,9 @@ ApplicationWindow {
                 Layout.fillWidth: true
                 text: {
                     if (!visible) return ""
-                    let content = block.blockContent
-                    let trimmed = content.trimStart()
+                    let content = block.blockContent || ""
+                    if (!content) return ""
+                    let trimmed = content.trim()
                     if (trimmed.startsWith("{") || trimmed.startsWith("["))
                         return chatModel.prettyJson(content)
                     if (trimmed.startsWith("---") || trimmed.startsWith("diff "))