diff --git a/cli/src/test/java/io/github/dfa1/vortex/cli/tui/TuiTestSupport.java b/cli/src/test/java/io/github/dfa1/vortex/cli/tui/TuiTestSupport.java
index bcc591f9..86217365 100644
--- a/cli/src/test/java/io/github/dfa1/vortex/cli/tui/TuiTestSupport.java
+++ b/cli/src/test/java/io/github/dfa1/vortex/cli/tui/TuiTestSupport.java
@@ -79,6 +79,33 @@ static Path writeMultiTypeVortex(Path dir, String name) throws IOException {
         return file;
     }
 
+    /// Writes a single-chunk file with a low-cardinality `label` Utf8 column and an
+    /// `n` I64 column. The repeated labels trip the global-dictionary encoder, so the
+    /// `label` column decodes to a `vortex.dict` layout — letting the inspector render
+    /// its dictionary-preview detail pane (alongside the I64 data-preview pane).
+    ///
+    /// The global dictionary only forms within a single chunk, so all `rows` are
+    /// written in one `writeChunk`.
+    static Path writeRichVortex(Path dir, String name, int rows) throws IOException {
+        Path file = dir.resolve(name);
+        DType.Struct schema = new DType.Struct(
+                List.of("label", "n"),
+                List.of(new DType.Utf8(false), new DType.Primitive(PType.I64, false)),
+                false);
+        String[] labels = {"red", "green", "blue"};
+        String[] label = new String[rows];
+        long[] n = new long[rows];
+        for (int i = 0; i < rows; i++) {
+            label[i] = labels[i % labels.length];
+            n[i] = i;
+        }
+        try (FileChannel ch = FileChannel.open(file, StandardOpenOption.CREATE, StandardOpenOption.WRITE);
+             VortexWriter writer = VortexWriter.create(ch, schema, WriteOptions.defaults())) {
+            writer.writeChunk(Map.of("label", label, "n", n));
+        }
+        return file;
+    }
+
     /// Opens `file` on the worker thread and returns the handle. The caller must
     /// close the returned handle on the same worker (see [#closeOnWorker]).
     ///
diff --git a/cli/src/test/java/io/github/dfa1/vortex/cli/tui/VortexInspectorTuiTest.java b/cli/src/test/java/io/github/dfa1/vortex/cli/tui/VortexInspectorTuiTest.java
index 4441b23b..187f0e21 100644
--- a/cli/src/test/java/io/github/dfa1/vortex/cli/tui/VortexInspectorTuiTest.java
+++ b/cli/src/test/java/io/github/dfa1/vortex/cli/tui/VortexInspectorTuiTest.java
@@ -3,12 +3,15 @@
 import io.github.dfa1.vortex.cli.tui.term.Key;
 import io.github.dfa1.vortex.cli.tui.term.Terminal;
 import io.github.dfa1.vortex.inspect.InspectorTree;
+import io.github.dfa1.vortex.reader.VortexHandle;
 import io.github.dfa1.vortex.reader.VortexReader;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
 import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -67,4 +70,66 @@ void quitsOnEscapeWithoutRenderingDetails() throws Exception {
 
         assertThat(term.output()).contains("vortex-inspect");
     }
+
+    @Test
+    void deepExpand_rendersDictAndDataPanes_synchronously() throws Exception {
+        // Given — a rich fixture (low-cardinality dict column + an I64 column) and a
+        // script that expands the whole tree, then visits every row so each node's
+        // detail pane renders. worker == null runs all previews inline.
+        Path file = TuiTestSupport.writeRichVortex(tmp, "rich.vortex", 200);
+        FakeTerminal term = new FakeTerminal(new Terminal.Size(40, 120), expandAndVisitAll());
+
+        // When
+        try (VortexReader handle = VortexReader.open(file)) {
+            InspectorTree tree = InspectorTree.buildShallow(handle);
+            VortexInspectorTui.run(term, tree, handle, null);
+        }
+
+        // Then — the dictionary-preview and data-preview panes both rendered
+        String out = term.output();
+        assertThat(out).contains("Dictionary");
+        assertThat(out).contains("Data (column");
+    }
+
+    @Test
+    void deepExpand_overWorker_drivesAsyncPreviews() throws Exception {
+        // Given — same rich fixture, but a real IoWorker so the async submit branches
+        // (dict/stats/data load via worker.submit, indexStatsChildrenOnWorker, peek
+        // prefetch) are exercised instead of the synchronous render-thread path.
+        Path file = TuiTestSupport.writeRichVortex(tmp, "rich.vortex", 200);
+        FakeTerminal term = new FakeTerminal(new Terminal.Size(40, 120), expandAndVisitAll(), 3);
+
+        // When — handle and tree are built on the worker thread (confined arena)
+        try (IoWorker worker = new IoWorker("inspect-test-io")) {
+            VortexHandle handle = TuiTestSupport.openOnWorker(worker, file);
+            try {
+                AtomicReference<InspectorTree> tree = new AtomicReference<>();
+                worker.runAndAwait(() -> tree.set(InspectorTree.buildShallow(handle)));
+                VortexInspectorTui.run(term, tree.get(), handle, worker);
+            } finally {
+                TuiTestSupport.closeOnWorker(worker, handle);
+            }
+        }
+
+        // Then — completes and rendered the inspector chrome
+        assertThat(term.output()).contains("vortex-inspect");
+    }
+
+    /// Script: expand every node along the traversal, then return to the top and step
+    /// through all now-visible rows so each node is selected (and its detail pane
+    /// rendered) at least once.
+    private static List<Key> expandAndVisitAll() {
+        List<Key> script = new ArrayList<>();
+        script.add(Key.Home.INSTANCE);
+        for (int i = 0; i < 40; i++) {
+            script.add(Key.ArrowRight.INSTANCE);
+            script.add(Key.ArrowDown.INSTANCE);
+        }
+        script.add(Key.Home.INSTANCE);
+        for (int i = 0; i < 80; i++) {
+            script.add(Key.ArrowDown.INSTANCE);
+        }
+        script.add(new Key.Char('q'));
+        return script;
+    }
 }