diff --git a/gui/chatblockmodel.cpp b/gui/chatblockmodel.cpp
index e69c633..f71dd4a 100644
--- a/gui/chatblockmodel.cpp
+++ b/gui/chatblockmodel.cpp
@@ -8,6 +8,8 @@
 #include <QTextDocument>
 #include <QGuiApplication>
 #include <QClipboard>
+#include <QJsonDocument>
+#include <QJsonParseError>
 #include <QPalette>
 
 static KSyntaxHighlighting::Repository *s_repo = nullptr;
@@ -368,6 +370,20 @@ QString ChatBlockModel::highlightedHtml(const QString &code, const QString &lang
     return html;
 }
 
+QString ChatBlockModel::prettyJson(const QString &text) const
+{
+    // Try to parse and pretty-print JSON, then syntax highlight
+    QJsonParseError err;
+    QJsonDocument doc = QJsonDocument::fromJson(text.toUtf8(), &err);
+    QString formatted;
+    if (err.error == QJsonParseError::NoError) {
+        formatted = QString::fromUtf8(doc.toJson(QJsonDocument::Indented));
+    } else {
+        formatted = text;
+    }
+    return highlightedHtml(formatted, QStringLiteral("JSON"));
+}
+
 void ChatBlockModel::copyToClipboard(const QString &text) const
 {
     QGuiApplication::clipboard()->setText(text);
diff --git a/gui/chatblockmodel.h b/gui/chatblockmodel.h
index bea9821..5bbb823 100644
--- a/gui/chatblockmodel.h
+++ b/gui/chatblockmodel.h
@@ -60,6 +60,7 @@ public:
     void setRawText(const QString &text);
 
     Q_INVOKABLE QString highlightedHtml(const QString &code, const QString &language) const;
+    Q_INVOKABLE QString prettyJson(const QString &text) const;
     Q_INVOKABLE void copyToClipboard(const QString &text) const;
     Q_INVOKABLE bool loadEarlier(); // returns true if more blocks were loaded
 
diff --git a/gui/main.qml b/gui/main.qml
index 9e72f1a..690e628 100644
--- a/gui/main.qml
+++ b/gui/main.qml
@@ -622,27 +622,14 @@ ApplicationWindow {
             Text {
                 id: callText
                 Layout.fillWidth: true
-                text: block.blockContent
-                textFormat: Text.PlainText
+                text: visible ? chatModel.prettyJson(block.blockContent) : ""
+                textFormat: Text.RichText
                 wrapMode: Text.Wrap
                 font.family: "monospace"
                 font.pixelSize: Qt.application.font.pixelSize * 0.85
                 opacity: 0.7
                 visible: false
                 color: palette.text
-
-                onVisibleChanged: {
-                    if (visible && textFormat === Text.PlainText) {
-                        try {
-                            let obj = JSON.parse(block.blockContent)
-                            let pretty = JSON.stringify(obj, null, 2)
-                            text = chatModel.highlightedHtml(pretty, "json")
-                        } catch(e) {
-                            text = chatModel.highlightedHtml(block.blockContent, "json")
-                        }
-                        textFormat = Text.RichText
-                    }
-                }
             }
         }
     }
@@ -664,8 +651,17 @@ ApplicationWindow {
             Text {
                 id: toolText
                 Layout.fillWidth: true
-                text: block.blockContent
-                textFormat: Text.PlainText
+                text: {
+                    if (!visible) return ""
+                    let content = block.blockContent
+                    let trimmed = content.trimStart()
+                    if (trimmed.startsWith("{") || trimmed.startsWith("["))
+                        return chatModel.prettyJson(content)
+                    if (trimmed.startsWith("---") || trimmed.startsWith("diff "))
+                        return chatModel.highlightedHtml(content, "diff")
+                    return content.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/\n/g, '<br>')
+                }
+                textFormat: Text.RichText
                 wrapMode: Text.Wrap
                 font.family: "monospace"
                 font.pixelSize: Qt.application.font.pixelSize * 0.85
@@ -674,30 +670,6 @@ ApplicationWindow {
                 color: palette.text
                 maximumLineCount: 80
                 elide: Text.ElideRight
-
-                onVisibleChanged: {
-                    if (visible && textFormat === Text.PlainText) {
-                        let content = block.blockContent
-                        let trimmed = content.trimStart()
-                        let lang = ""
-                        if (trimmed.startsWith("{") || trimmed.startsWith("[")) lang = "json"
-                        else if (trimmed.startsWith("---") || trimmed.startsWith("diff ")) lang = "diff"
-
-                        if (lang === "json") {
-                            try {
-                                let obj = JSON.parse(content)
-                                let pretty = JSON.stringify(obj, null, 2)
-                                text = chatModel.highlightedHtml(pretty, "json")
-                            } catch(e) {
-                                text = chatModel.highlightedHtml(content, "json")
-                            }
-                            textFormat = Text.RichText
-                        } else if (lang) {
-                            text = chatModel.highlightedHtml(content, lang)
-                            textFormat = Text.RichText
-                        }
-                    }
-                }
             }
         }
     }