diff --git a/src/test/java/io/github/nbclaudecodegui/ui/ClaudeSessionTabDiffTest.java b/src/test/java/io/github/nbclaudecodegui/ui/ClaudeSessionTabDiffTest.java
new file mode 100644
index 00000000..4dd2807d
--- /dev/null
+++ b/src/test/java/io/github/nbclaudecodegui/ui/ClaudeSessionTabDiffTest.java
@@ -0,0 +1,175 @@
+package io.github.nbclaudecodegui.ui;
+
+import java.awt.CardLayout;
+import java.awt.Component;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.JSplitPane;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Tests for the two embedded-diff bugs fixed in 0.22.2:
+ * <ol>
+ *   <li>Stale {@code CARD_DIFF} accumulates in the CardLayout when
+ *       {@link ClaudeSessionTab#showEmbeddedDiff} is called multiple times.</li>
+ *   <li>Wrong divider position when the diff card first appears ({@link
+ *       ClaudeSessionTab#computeBottomHeight} default logic).</li>
+ * </ol>
+ */
+class ClaudeSessionTabDiffTest {
+
+    // -------------------------------------------------------------------------
+    // Bug 1 — computeBottomHeight default values
+    // -------------------------------------------------------------------------
+
+    @Test
+    void computeBottomHeight_savedValue_returnsSaved() {
+        assertEquals(123, ClaudeSessionTab.computeBottomHeight("diff", 900, 123, -1, 50));
+    }
+
+    @Test
+    void computeBottomHeight_diffCard_noSaved_returnsTwoThirdsTotal() {
+        int total = 900;
+        int expected = total * 2 / 3;  // 600
+        assertEquals(expected, ClaudeSessionTab.computeBottomHeight("diff", total, -1, -1, 50));
+    }
+
+    @Test
+    void computeBottomHeight_promptCard_noSaved_legacyPresent_returnsLegacy() {
+        assertEquals(200, ClaudeSessionTab.computeBottomHeight("prompt", 900, -1, 200, 50));
+    }
+
+    @Test
+    void computeBottomHeight_promptCard_noSaved_noLegacy_returnsPreferred() {
+        assertEquals(50, ClaudeSessionTab.computeBottomHeight("prompt", 900, -1, -1, 50));
+    }
+
+    @Test
+    void computeBottomHeight_diffCard_savedZeroIgnored_returnsTwoThirds() {
+        // saved == 0 is treated as "not saved" (condition is saved > 0)
+        int total = 600;
+        assertEquals(total * 2 / 3, ClaudeSessionTab.computeBottomHeight("diff", total, 0, -1, 50));
+    }
+
+    // -------------------------------------------------------------------------
+    // getSavedCardKeyFor
+    // -------------------------------------------------------------------------
+
+    @Test
+    void savedCardKey_promptCard_returnsBackwardCompatKey() {
+        ClaudeSessionTab tab = new ClaudeSessionTab();
+        assertEquals("bottomHeight", tab.getSavedCardKeyFor("prompt"));
+    }
+
+    @Test
+    void savedCardKey_nullCard_returnsBackwardCompatKey() {
+        ClaudeSessionTab tab = new ClaudeSessionTab();
+        assertEquals("bottomHeight", tab.getSavedCardKeyFor(null));
+    }
+
+    @Test
+    void savedCardKey_diffCard_returnsDiffHeight() {
+        ClaudeSessionTab tab = new ClaudeSessionTab();
+        assertEquals("diffHeight", tab.getSavedCardKeyFor("diff"));
+    }
+
+    // -------------------------------------------------------------------------
+    // Bug 2 — stale CARD_DIFF accumulates in CardLayout
+    // -------------------------------------------------------------------------
+
+    /**
+     * Sets up a minimal south-card environment on a tab (without starting a PTY)
+     * so that {@link ClaudeSessionTab#showEmbeddedDiff} can be called.
+     * {@code switchSouthCard} is overridden to a no-op to avoid needing a full
+     * JediTerm widget and splitPane.
+     */
+    private ClaudeSessionTab tabWithSouthCard() {
+        ClaudeSessionTab tab = new ClaudeSessionTab() {
+            @Override
+            void switchSouthCard(String card) {
+                // no-op: avoids splitPane / terminalWidget dependency in tests
+                activeCard = card;
+            }
+        };
+        CardLayout layout = new CardLayout();
+        JPanel south = new JPanel(layout);
+        tab.southCard = south;
+        tab.southCardLayout = layout;
+        tab.activeCard = "prompt";
+        return tab;
+    }
+
+    @Test
+    void showEmbeddedDiff_firstCall_addsDiffCard() {
+        ClaudeSessionTab tab = tabWithSouthCard();
+
+        boolean shown = tab.showEmbeddedDiff(false, null, null,
+                new JLabel("diff1"),
+                new FileDiffPermissionPanel(() -> {}, r -> {}, () -> {}, () -> {}, null),
+                null);
+
+        assertTrue(shown, "showEmbeddedDiff must return true when southCard is set");
+        assertNotNull(tab.currentDiffCard, "currentDiffCard must be set after first call");
+        // southCard now contains exactly one CARD_DIFF panel
+        assertEquals(1, countComponents(tab.southCard));
+    }
+
+    @Test
+    void showEmbeddedDiff_secondCall_replacesOldCard() {
+        ClaudeSessionTab tab = tabWithSouthCard();
+
+        tab.showEmbeddedDiff(false, null, null,
+                new JLabel("diff1"),
+                new FileDiffPermissionPanel(() -> {}, r -> {}, () -> {}, () -> {}, null),
+                null);
+        JPanel firstCard = tab.currentDiffCard;
+
+        tab.showEmbeddedDiff(false, null, null,
+                new JLabel("diff2"),
+                new FileDiffPermissionPanel(() -> {}, r -> {}, () -> {}, () -> {}, null),
+                null);
+        JPanel secondCard = tab.currentDiffCard;
+
+        assertNotSame(firstCard, secondCard, "currentDiffCard must be replaced on second call");
+        // Only the new card should remain in southCard — no stale accumulation
+        assertEquals(1, countComponents(tab.southCard),
+                "southCard must contain exactly one diff card after second showEmbeddedDiff");
+        assertFalse(isChildOf(tab.southCard, firstCard),
+                "Old diff card must be removed from southCard");
+        assertTrue(isChildOf(tab.southCard, secondCard),
+                "New diff card must be present in southCard");
+    }
+
+    @Test
+    void hideEmbeddedDiff_removesCardAndClearsField() {
+        ClaudeSessionTab tab = tabWithSouthCard();
+
+        tab.showEmbeddedDiff(false, null, null,
+                new JLabel("diff"),
+                new FileDiffPermissionPanel(() -> {}, r -> {}, () -> {}, () -> {}, null),
+                null);
+
+        tab.hideEmbeddedDiff();
+
+        assertNull(tab.currentDiffCard, "currentDiffCard must be null after hide");
+        assertEquals(0, countComponents(tab.southCard),
+                "southCard must have no diff card after hide");
+    }
+
+    // -------------------------------------------------------------------------
+    // Helpers
+    // -------------------------------------------------------------------------
+
+    private static int countComponents(JPanel panel) {
+        return panel.getComponentCount();
+    }
+
+    private static boolean isChildOf(JPanel parent, Component child) {
+        for (int i = 0; i < parent.getComponentCount(); i++) {
+            if (parent.getComponent(i) == child) return true;
+        }
+        return false;
+    }
+}