Look at the code and the attached movie.

Initially, when I create TabPane, its size respond to the size of control, which is in its tab. But, when I start to change its size, TabPane doesn't track it any more.

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Slider;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class JavaApplication59 extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        Button b = new Button("Some button");
        
        Slider slider = new Slider(0, 200, 100);
        slider.setShowTickLabels(true);
        slider.setShowTickMarks(true);
        b.minWidthProperty().bind(slider.valueProperty());
        
        Pane pane = new Pane();
        pane.setMinSize(200, 200);
        pane.setPrefSize(200, 200);
        pane.setMaxSize(200, 200);
        
        Tab tab = new Tab();
        tab.setContent(b);
        
        TabPane tp = new TabPane();
        tp.getTabs().add(tab);
        
        pane.getChildren().add(tp);
        
        VBox vb = new VBox();
        vb.getChildren().addAll(pane, slider);
        Scene scene = new Scene(vb, 300, 300);
        stage.setScene(scene);
        stage.show();
    }
}

On movie: I added button in tab in tabPane. I showed their widths. After that I changed width of button. But TabPane's size didn;t change.

This lead to the situation, when I have ScrollPane in Tab in TabPane in HBox, and TabPane is compressed, because it doesn't know anything about ScrollPane's size, especially when I set size of scrollPane according to scrollPane's content size.