diff --git a/api/src/main/java/io/xpipe/api/DataSource.java b/api/src/main/java/io/xpipe/api/DataSource.java
index 4f230a20a..7c2271897 100644
--- a/api/src/main/java/io/xpipe/api/DataSource.java
+++ b/api/src/main/java/io/xpipe/api/DataSource.java
@@ -17,6 +17,22 @@ import java.util.Map;
  */
 public interface DataSource {
 
+    /**
+     * Creates a new supplier data source that will be interpreted as the generated data source.
+     * In case this program should be a data source generator, this method has to be called at
+     * least once to register that it actually generates a data source.
+     *
+     * All content that is written to this data source until the generator program terminates is
+     * will be available later on when the data source is used as a supplier later on.
+     *
+     * In case this method is called multiple times, the same data source is returned.
+     *
+     * @return the generator data source
+     */
+    static DataSource supplySource() {
+        return null;
+    }
+
     /**
      * Wrapper for {@link #get(DataSourceId)}.
      *
diff --git a/api/src/main/java/io/xpipe/api/DataTable.java b/api/src/main/java/io/xpipe/api/DataTable.java
index 1522e50e5..33af114a8 100644
--- a/api/src/main/java/io/xpipe/api/DataTable.java
+++ b/api/src/main/java/io/xpipe/api/DataTable.java
@@ -9,6 +9,13 @@ import java.util.stream.Stream;
 
 public interface DataTable extends Iterable<TupleNode>, DataSource {
 
+    /**
+     * @see DataSource#supplySource()
+     */
+    static DataTable supplySource() {
+        return null;
+    }
+
     Stream<TupleNode> stream();
 
     int getRowCount();
diff --git a/core/src/main/java/io/xpipe/core/source/DataSourceId.java b/core/src/main/java/io/xpipe/core/source/DataSourceId.java
index 0453aeb21..9f9707d26 100644
--- a/core/src/main/java/io/xpipe/core/source/DataSourceId.java
+++ b/core/src/main/java/io/xpipe/core/source/DataSourceId.java
@@ -89,6 +89,6 @@ public class DataSourceId {
 
     @Override
     public String toString() {
-        return collectionName.toLowerCase() + SEPARATOR + (entryName != null ? entryName.toLowerCase() : "");
+        return (collectionName != null ? collectionName.toLowerCase() : "") + SEPARATOR + entryName;
     }
 }
diff --git a/extension/src/main/java/io/xpipe/extension/DataSourceProvider.java b/extension/src/main/java/io/xpipe/extension/DataSourceProvider.java
index 339da00bc..d312612f6 100644
--- a/extension/src/main/java/io/xpipe/extension/DataSourceProvider.java
+++ b/extension/src/main/java/io/xpipe/extension/DataSourceProvider.java
@@ -1,9 +1,6 @@
 package io.xpipe.extension;
 
-import io.xpipe.core.source.DataSourceConfig;
-import io.xpipe.core.source.DataSourceDescriptor;
-import io.xpipe.core.source.DataSourceInfo;
-import io.xpipe.core.source.TableReadConnection;
+import io.xpipe.core.source.*;
 import io.xpipe.core.store.DataStore;
 import io.xpipe.core.store.StreamDataStore;
 import javafx.beans.property.Property;
@@ -77,6 +74,8 @@ public interface DataSourceProvider {
         List<String> getPossibleNames();
     }
 
+    DataSourceType getType();
+
     boolean supportsStore(DataStore store);
 
     FileProvider getFileProvider();
diff --git a/extension/src/main/java/io/xpipe/extension/comp/CharsetChoiceComp.java b/extension/src/main/java/io/xpipe/extension/comp/CharsetChoiceComp.java
index ed0de26cb..4f9417e4a 100644
--- a/extension/src/main/java/io/xpipe/extension/comp/CharsetChoiceComp.java
+++ b/extension/src/main/java/io/xpipe/extension/comp/CharsetChoiceComp.java
@@ -4,14 +4,14 @@ import io.xpipe.fxcomps.Comp;
 import io.xpipe.fxcomps.CompStructure;
 import io.xpipe.fxcomps.comp.ReplacementComp;
 import javafx.beans.property.Property;
-import javafx.scene.control.ChoiceBox;
+import javafx.scene.control.ComboBox;
 import org.apache.commons.collections4.bidimap.DualLinkedHashBidiMap;
 
 import java.nio.charset.Charset;
 import java.util.LinkedHashMap;
 import java.util.function.Supplier;
 
-public class CharsetChoiceComp extends ReplacementComp<CompStructure<ChoiceBox<Charset>>> {
+public class CharsetChoiceComp extends ReplacementComp<CompStructure<ComboBox<Charset>>> {
 
     private final Property<Charset> charset;
 
@@ -20,7 +20,7 @@ public class CharsetChoiceComp extends ReplacementComp<CompStructure<ChoiceBox<C
     }
 
     @Override
-    protected Comp<CompStructure<ChoiceBox<Charset>>> createComp() {
+    protected Comp<CompStructure<ComboBox<Charset>>> createComp() {
         var map = new LinkedHashMap<Charset, Supplier<String>>();
         for (var e : Charset.availableCharsets().entrySet()) {
             map.put(e.getValue(), e::getKey);
diff --git a/extension/src/main/java/io/xpipe/extension/comp/ChoiceComp.java b/extension/src/main/java/io/xpipe/extension/comp/ChoiceComp.java
index 3f46ecbdc..60b4bfbf2 100644
--- a/extension/src/main/java/io/xpipe/extension/comp/ChoiceComp.java
+++ b/extension/src/main/java/io/xpipe/extension/comp/ChoiceComp.java
@@ -5,13 +5,13 @@ import io.xpipe.fxcomps.CompStructure;
 import io.xpipe.fxcomps.util.PlatformUtil;
 import javafx.beans.property.Property;
 import javafx.collections.FXCollections;
-import javafx.scene.control.ChoiceBox;
+import javafx.scene.control.ComboBox;
 import javafx.util.StringConverter;
 import org.apache.commons.collections4.BidiMap;
 
 import java.util.function.Supplier;
 
-public class ChoiceComp<T> extends Comp<CompStructure<ChoiceBox<T>>> {
+public class ChoiceComp<T> extends Comp<CompStructure<ComboBox<T>>> {
 
     private final Property<T> value;
     private final BidiMap<T, Supplier<String>> range;
@@ -22,9 +22,9 @@ public class ChoiceComp<T> extends Comp<CompStructure<ChoiceBox<T>>> {
     }
 
     @Override
-    public CompStructure<ChoiceBox<T>> createBase() {
+    public CompStructure<ComboBox<T>> createBase() {
         var list = FXCollections.observableArrayList(range.keySet());
-        var cb = new ChoiceBox<>(list);
+        var cb = new ComboBox<>(list);
         cb.setConverter(new StringConverter<>() {
             @Override
             public String toString(T object) {
diff --git a/extension/src/main/java/io/xpipe/extension/comp/CodeSnippetComp.java b/extension/src/main/java/io/xpipe/extension/comp/CodeSnippetComp.java
index fa7a8af11..1379f019e 100644
--- a/extension/src/main/java/io/xpipe/extension/comp/CodeSnippetComp.java
+++ b/extension/src/main/java/io/xpipe/extension/comp/CodeSnippetComp.java
@@ -20,9 +20,11 @@ import java.awt.datatransfer.StringSelection;
 
 public class CodeSnippetComp extends Comp<CompStructure<StackPane>> {
 
+    private final ObservableValue<Boolean> showLineNumbers;
     private final ObservableValue<CodeSnippet> value;
 
-    public CodeSnippetComp(ObservableValue<CodeSnippet> value) {
+    public CodeSnippetComp(ObservableValue<Boolean> showLineNumbers, ObservableValue<CodeSnippet> value) {
+        this.showLineNumbers = showLineNumbers;
         this.value = PlatformUtil.wrap(value);
     }
 
@@ -88,22 +90,40 @@ public class CodeSnippetComp extends Comp<CompStructure<StackPane>> {
         value.addListener((c,o,n) -> {
             PlatformUtil.runLaterIfNeeded(() -> {
                 fillArea(lineNumbers, s);
+                s.setMaxHeight(5);
             });
         });
 
         var spacer = new Region();
         spacer.getStyleClass().add("spacer");
 
-        var content = new HBox(lineNumbers, spacer, s);
+        var content = new HBox(s);
+        spacer.prefHeightProperty().bind(content.heightProperty());
+        if (showLineNumbers.getValue()) {
+            content.getChildren().add(0, lineNumbers);
+            content.getChildren().add(1, spacer);
+        }
+        PlatformUtil.wrap(showLineNumbers).addListener((c,o,n) -> {
+            if (n) {
+                content.getChildren().add(0, lineNumbers);
+                content.getChildren().add(1, spacer);
+            } else {
+                content.getChildren().remove(lineNumbers);
+                content.getChildren().remove(spacer);
+            }
+        });
         HBox.setHgrow(s, Priority.ALWAYS);
         var container = new ScrollPane(content);
         container.setFitToWidth(true);
+        container.setFitToHeight(true);
 
         var c = new StackPane(container);
+        container.prefHeightProperty().bind(c.heightProperty());
         c.getStyleClass().add("code-snippet-container");
 
         var copyButton = createCopyButton(c);
         var pane = new AnchorPane(copyButton);
+        pane.setPickOnBounds(false);
         AnchorPane.setTopAnchor(copyButton, 10.0);
         AnchorPane.setRightAnchor(copyButton, 10.0);
         c.getChildren().add(pane);
diff --git a/extension/src/main/java/io/xpipe/extension/event/ErrorEvent.java b/extension/src/main/java/io/xpipe/extension/event/ErrorEvent.java
index c47192528..c99befa91 100644
--- a/extension/src/main/java/io/xpipe/extension/event/ErrorEvent.java
+++ b/extension/src/main/java/io/xpipe/extension/event/ErrorEvent.java
@@ -11,6 +11,17 @@ import java.util.List;
 @Getter
 public class ErrorEvent {
 
+    public static class ErrorEventBuilder {
+
+        public ErrorEventBuilder omit() {
+            return omitted(true);
+        }
+
+        public void handle() {
+            build().handle();
+        }
+    }
+
     public static ErrorEventBuilder fromThrowable(Throwable t) {
         return builder().throwable(t)
                 .description(ExceptionConverter.convertMessage(t));
diff --git a/extension/src/main/java/io/xpipe/extension/event/ExceptionConverter.java b/extension/src/main/java/io/xpipe/extension/event/ExceptionConverter.java
index f13a0deb8..6c8897a2c 100644
--- a/extension/src/main/java/io/xpipe/extension/event/ExceptionConverter.java
+++ b/extension/src/main/java/io/xpipe/extension/event/ExceptionConverter.java
@@ -12,6 +12,10 @@ public class ExceptionConverter {
             return I18n.get("fileNotFound", msg);
         }
 
+        if (ex instanceof ClassNotFoundException) {
+            return I18n.get("classNotFound", msg);
+        }
+
         return msg;
     }
 }
diff --git a/extension/src/main/resources/io/xpipe/extension/resources/style/code-snippet.css b/extension/src/main/resources/io/xpipe/extension/resources/style/code-snippet.css
index d2fad34e4..af5798a4d 100644
--- a/extension/src/main/resources/io/xpipe/extension/resources/style/code-snippet.css
+++ b/extension/src/main/resources/io/xpipe/extension/resources/style/code-snippet.css
@@ -1,6 +1,6 @@
 .code-snippet {
 -fx-padding: 0.3em 0.5em 0.3em 0.5em;
--fx-border-width: 0 0 0 1px;
+-fx-border-width: 0;
 -fx-border-color: -xp-border;
 -fx-spacing: 0;
 -fx-font-family: Monospace;
@@ -30,12 +30,7 @@
 -fx-background-color: #073B4C11;
 }
 
-.code-snippet .line {
--fx-padding: 0.1em 0 0 0;
--fx-background-color: transparent;
-}
-
-.code-snippet .spacer {
+.code-snippet-container .spacer {
 -fx-pref-width: 1px;
--fx-background-color: #073B4C43;
+-fx-background-color: -xp-border;
 }