fix(engine): default transparent to true in queue_frame

crates/engine/src/commands/comp_more.rs

@@ -91,14 +91,13 @@ fn queue_frame(s: &mut Session, p: &Value) -> Result<Value> {
     it.settings = s.project.render_templates.default_render_settings(TemplateSlot::Still);
     it.settings.time_span = TimeSpan::Custom { start: t, end: t + comp.frame_duration() };
     it.output = s.project.render_templates.default_output_module(TemplateSlot::Still);
-    if let Some(transparent) = b_p(p, "transparent") {
-        if !transparent {
-            it.output.channels = Channels::Rgb;
-        } else if it.output.supports_alpha() {
-            it.output.channels = Channels::Rgba;
-        } else {
-            return Err(bad("comp.saveFrameAs", format!("{} doesn't support an alpha channel", it.output.format.label())));
-        }
+    let transparent = b_p(p, "transparent").unwrap_or(true);
+    if !transparent {
+        it.output.channels = Channels::Rgb;
+    } else if it.output.supports_alpha() {
+        it.output.channels = Channels::Rgba;
+    } else {
+        return Err(bad("comp.saveFrameAs", format!("{} doesn't support an alpha channel", it.output.format.label())));
     }
     if let Some(path) = str_p(p, "path") {
         it.output.output = path.to_string();

crates/engine/src/tests_frame_export.rs

@@ -219,3 +219,22 @@ fn save_frame_as_defaults_to_png_sequence_with_alpha() {
     assert_eq!(it.output.name, "PNG Sequence with Alpha");
     assert_eq!(it.output.channels, effectcraft_project::render_queue::Channels::Rgba);
 }
+
+#[test]
+fn save_frame_as_defaults_to_transparent_even_with_rgb_frame_template() {
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"name": "Comp", "width": 32, "height": 32, "frameRate": 24, "duration": 1})).unwrap();
+
+    // Set Frame Default to an RGB output template ("PNG Sequence")
+    s.execute_checked("renderQueue.setTemplateDefault", json!({"kind": "outputModule", "slot": "still", "name": "PNG Sequence"})).unwrap();
+
+    // Omitting `transparent` must default to true and promote to Channels::Rgba
+    s.execute_checked("comp.saveFrameAs", json!({"queue": true})).unwrap();
+    let it = s.project.render_queue.last().unwrap();
+    assert_eq!(it.output.channels, effectcraft_project::render_queue::Channels::Rgba);
+
+    // Explicit `transparent: false` respects the request and stays Channels::Rgb
+    s.execute_checked("comp.saveFrameAs", json!({"queue": true, "transparent": false})).unwrap();
+    let it = s.project.render_queue.last().unwrap();
+    assert_eq!(it.output.channels, effectcraft_project::render_queue::Channels::Rgb);
+}