diff --git a/assets/style.css b/assets/style.css
index f19b6ee..f1a7338 100644
--- a/assets/style.css
+++ b/assets/style.css
@@ -27,6 +27,9 @@
 
     --border: 1px solid var(--secondary);
     --border-dashed: 1px dashed var(--secondary);
+    /* Subtle vertical rail for tree-nesting depth — quieter than --border so
+       it reads as a guide, not a divider. */
+    --border-guide: 1px solid var(--bg-panel-hover);
 
     --space-1: 0.25rem;
     --space-2: 0.5rem;
@@ -593,14 +596,16 @@ aside.sidebar:empty { display: none; }
 }
 
 /* === Tree picker === */
-.tree-picker { max-height: 60vh; overflow-y: auto; }
+/* Rows are click targets (navigate / toggle), not prose — suppress the
+   text-selection highlight that double/drag clicks would otherwise leave,
+   matching the persistent .tree-sidebar rail. */
+.tree-picker { max-height: 60vh; overflow-y: auto; user-select: none; }
 .tree-row {
     display: flex;
     align-items: center;
-    gap: var(--space-2);
-    padding: 0.4rem var(--space-2);
+    gap: var(--space-1);
+    padding: 0.25rem var(--space-1);
     cursor: pointer;
-    min-height: 2rem;
 }
 .tree-row:hover, .tree-row.is-selected { background: var(--bg-panel-hover); }
 .tree-row.is-selected {
@@ -613,7 +618,13 @@ aside.sidebar:empty { display: none; }
 .tree-chevron { width: 1.25rem; color: var(--secondary); }
 .tree-chevron.is-leaf { visibility: hidden; }
 .tree-name { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
-.tree-children { padding-left: var(--space-2); }
+/* Each nesting level gets a vertical guide rail down its left edge so depth
+   stays scannable in the compact view (cf. VS Code / file-explorer trees). */
+.tree-children {
+    margin-left: var(--space-2);
+    padding-left: var(--space-2);
+    border-left: var(--border-guide);
+}
 .tree-selected-path {
     font-size: var(--font-sm);
     padding: var(--space-1) 0;