fix(ai): collapse completed design steps

crates/op-editor-ui/src/widgets/ai_chat_transcript.rs

@@ -93,6 +93,7 @@ pub(crate) struct ActionStep {
     pub rect: Rect,
     pub label: String,
     pub details: Vec<String>,
+    pub expanded: bool,
     pub done: bool,
     pub active: bool,
     pub failed: bool,
@@ -258,11 +259,13 @@ fn build_item(
             .iter()
             .flat_map(|line| wrap_units(line, budget.saturating_sub(4)))
             .collect();
-        let step_h = action_step_height(details.len());
+        let expanded = active;
+        let step_h = action_step_height(expanded, details.len());
         steps.push(ActionStep {
             rect: Rect::xywh(x, y, bubble_w, step_h),
             label: step.title.clone(),
             details,
+            expanded,
             done,
             active,
             failed,
@@ -395,8 +398,8 @@ fn build_item(
     )
 }
 
-fn action_step_height(detail_count: usize) -> f32 {
-    if detail_count == 0 {
+fn action_step_height(expanded: bool, detail_count: usize) -> f32 {
+    if !expanded || detail_count == 0 {
         ACTION_STEP_H
     } else {
         ACTION_STEP_H + ACTION_DETAIL_GAP + detail_count as f32 * ACTION_DETAIL_LINE_H
@@ -528,7 +531,22 @@ fn paint_action_step(cx: &mut PaintCx<'_>, theme: &Theme, step: &ActionStep) {
         11.0,
         label_color,
     );
-    if !step.details.is_empty() {
+    draw_icon(
+        cx.backend,
+        if step.expanded {
+            Icon::ChevronDown
+        } else {
+            Icon::ChevronRight
+        },
+        Point2D::new(
+            step.rect.origin.x + step.rect.size.x - 20.0,
+            step.rect.origin.y + 7.0,
+        ),
+        14.0,
+        theme.muted_foreground,
+        1.5,
+    );
+    if step.expanded && !step.details.is_empty() {
         cx.backend.save();
         cx.backend.clip_rect(step.rect);
         let mut baseline = step.rect.origin.y + ACTION_STEP_H + ACTION_DETAIL_GAP + 9.0;

crates/op-editor-ui/src/widgets/ai_chat_transcript_tests.rs

@@ -344,6 +344,67 @@ render: captured frame
     );
 }
 
+#[test]
+fn completed_step_with_content_defaults_collapsed_like_ts_accordion() {
+    let mut message = ChatMessage::assistant(
+        r#"<step title="Validate design" status="done">
+lint: fixed spacing
+render: captured frame
+</step>"#,
+    );
+    message.streaming = false;
+
+    let items = build_transcript(
+        std::slice::from_ref(&message),
+        body(),
+        op_editor_core::Locale::EnUs,
+    );
+
+    assert_eq!(items[0].steps.len(), 1);
+    assert!(items[0].steps[0].done);
+    assert!(!items[0].steps[0].active);
+    assert!(
+        (items[0].steps[0].rect.size.y - ACTION_STEP_H).abs() < 1e-4,
+        "TS ActionStepItem defaults completed accordions closed"
+    );
+}
+
+#[test]
+fn paint_completed_step_hides_details_like_collapsed_ts_accordion() {
+    let message = ChatMessage::assistant(
+        r#"<step title="Validate design" status="done">
+lint: fixed spacing
+render: captured frame
+</step>"#,
+    );
+    let mut backend = TranscriptPaintBackend::default();
+    let mut cx = PaintCx {
+        backend: &mut backend,
+    };
+
+    paint_transcript(
+        &mut cx,
+        &crate::Theme::dark(),
+        body(),
+        &[message],
+        0,
+        op_editor_core::Locale::EnUs,
+    );
+
+    assert!(
+        backend.texts.iter().any(|text| text == "Validate design"),
+        "collapsed accordion still paints its title"
+    );
+    assert!(
+        !backend
+            .texts
+            .iter()
+            .any(|text| text.contains("lint: fixed spacing")
+                || text.contains("render: captured frame")),
+        "collapsed TS accordions hide details until opened"
+    );
+}
+
 #[test]
 fn assistant_design_json_code_fence_renders_compact_design_block() {
     let message = ChatMessage::assistant(