diff --git a/packages/chess/e2e/full-flow.spec.ts b/packages/chess/e2e/full-flow.spec.ts
new file mode 100644
index 0000000..fd0eb92
--- /dev/null
+++ b/packages/chess/e2e/full-flow.spec.ts
@@ -0,0 +1,122 @@
+import { test, expect } from '@playwright/test';
+
+/**
+ * Full Phase-3 gate scenario:
+ *   preset-toggle → Scholar's Mate play → undo → save/reload → export → import → checkmate
+ *
+ * Undo is exercised on the *original* page before reload, where moveHistoryRef
+ * still holds all moves since start (loadEngine resets history, so undo is only
+ * meaningful there). Export/import is verified by restoring that same 8-move
+ * position in a fresh browser context, then completing the Scholar's Mate.
+ */
+test("full game flow: preset toggle, Scholar's Mate, save/reload, export/import, undo, checkmate", async ({ page, browser }) => {
+
+  // ── Step 1: Preset toggles ─────────────────────────────────────────────────
+  await page.goto('/rules');
+  // pawns-move-backward: incompatibleWith ["double-pawn-sprint"] only
+  await page.locator('[data-preset="pawns-move-backward"] [data-role="toggle"]').click();
+  // knights-leap-twice: incompatibleWith []
+  await page.locator('[data-preset="knights-leap-twice"] [data-role="toggle"]').click();
+  // These two presets are compatible — no compat warning
+  await expect(page.locator('[data-testid="compat-warning"]')).not.toBeVisible();
+
+  await page.locator('[data-action="start-new-game"]').click();
+  await page.waitForURL('**/game');
+
+  // ── Step 2: Play all 8 moves before any reload ────────────────────────────
+  //
+  // We play ALL 8 moves here on the pristine page so that moveHistoryRef still
+  // holds the full sequence. loadEngine() resets moveHistoryRef to [], so any
+  // subsequent reload/import invalidates the undo chain; doing undo NOW (before
+  // the first reload) is the only way to test it correctly without source changes.
+  //
+  // Targeting `[data-square="${from}"] [data-piece]` places the drag origin on
+  // the draggable piece element so that dragstart fires on it. The target is the
+  // square div that has onDrop/onDragOver.
+  const drag = async (from: string, to: string) => {
+    await page
+      .locator(`[data-square="${from}"] [data-piece]`)
+      .dragTo(page.locator(`[data-square="${to}"]`));
+  };
+
+  // Scholar's Mate setup — moves 1-5
+  await drag('e2', 'e4'); // 1. e4
+  await drag('e7', 'e5'); // 1...e5
+  await drag('f1', 'c4'); // 2. Bc4
+  await drag('b8', 'c6'); // 2...Nc6
+  await drag('d1', 'h5'); // 3. Qh5
+
+  await expect(page.locator('[data-testid="turn-indicator"]')).toContainText('Black');
+
+  // Continuation — moves 6-8
+  await drag('d7', 'd6'); // 3...d6  (random; Qf7 still covers d7 via rank-7)
+  await drag('a2', 'a3'); // 4. a3   (random)
+  await drag('g8', 'f6'); // 4...Nf6?? — will be undone
+
+  // ── Step 3: Undo Nf6, verify knight back on g8 ────────────────────────────
+  // History = [e4,e5,Bc4,Nc6,Qh5,d6,a3,Nf6] → pop → [e4,e5,Bc4,Nc6,Qh5,d6,a3]
+  // Rebuild replays all 7 moves from initial; g8 kingside knight is untouched
+  // (only the b8 queenside knight moved to c6 in move 4).
+  await page.locator('[data-action="undo"]').click();
+  await expect(page.locator('[data-square="g8"] [data-piece="black-knight"]')).toBeVisible();
+
+  // Re-play Nf6 to restore the 8-move export state (White's turn)
+  await drag('g8', 'f6'); // 4...Nf6?? again
+
+  // ── Step 4: Save named slot ────────────────────────────────────────────────
+  await page.goto('/save');
+  await page.fill('input[type="text"]', 'scholars-test');
+  await page.locator('[data-action="save"]').click();
+  await expect(page.locator('[data-testid="save-slot-scholars-test"]')).toBeVisible();
+
+  // ── Step 5: Reload → autosave restore ─────────────────────────────────────
+  // Each applyMove() calls saveAutoSave(); App.useEffect restores it on mount.
+  // The last applyMove was Nf6 → autosave = 8-move state.
+  // Queen on h5 and bishop on c4 are present in that state (neither moved
+  // during moves 6-8).
+  await page.reload();
+  await page.goto('/game');
+  await expect(page.locator('[data-square="h5"] [data-piece="white-queen"]')).toBeVisible();
+  await expect(page.locator('[data-square="c4"] [data-piece="white-bishop"]')).toBeVisible();
+
+  // ── Step 6: Export JSON (8-move state, White's turn) ──────────────────────
+  await page.goto('/save');
+  const downloadPromise = page.waitForEvent('download');
+  await page.locator('[data-action="export"]').click();
+  const download = await downloadPromise;
+  const exportPath = `/tmp/chess-export-${Date.now()}.json`;
+  await download.saveAs(exportPath);
+
+  // ── Step 7: Import in a fresh browser context ──────────────────────────────
+  const freshContext = await browser.newContext();
+  const freshPage = await freshContext.newPage();
+  await freshPage.goto('http://localhost:5173/save');
+
+  // setInputFiles works on hidden inputs; onChange → FileReader → onLoad(facts)
+  // → handleLoad in SaveWrapper → loadEngine → saveAutoSave → navigate('/game')
+  const fileInput = freshPage.locator('input[type="file"]');
+  await fileInput.setInputFiles(exportPath);
+  await freshPage.waitForURL('**/game');
+
+  // Verify the 8-move position was restored in the fresh context
+  await expect(freshPage.locator('[data-square="h5"] [data-piece="white-queen"]')).toBeVisible();
+  await expect(freshPage.locator('[data-square="c4"] [data-piece="white-bishop"]')).toBeVisible();
+
+  // ── Step 8: Scholar's Mate — Qxf7# ───────────────────────────────────────
+  // It is White's turn (after Black's Nf6 in the imported 8-move state).
+  // h5→f7 is a 2-square diagonal via empty g6. f7 has the black f7 pawn.
+  // Queen on f7 is defended by Bc4 (c4-d5-e6-f7 diagonal).
+  // Black king on e8 cannot escape:
+  //   d8 = own queen (occupied),  d7 = attacked by Qf7 along rank-7,
+  //   e7 = attacked by Qf7 (adjacent on rank-7),  f8 = own bishop (occupied),
+  //   f7 = queen (defended by Bc4).
+  // Nf6 cannot capture f7 (not an L-shaped jump from f6).
+  await freshPage
+    .locator('[data-square="h5"] [data-piece]')
+    .dragTo(freshPage.locator('[data-square="f7"]'));
+
+  // ── Step 9: Assert checkmate ──────────────────────────────────────────────
+  await expect(freshPage.locator('[data-testid="game-over"]')).toBeVisible();
+
+  await freshContext.close();
+});
diff --git a/packages/chess/tsconfig.json b/packages/chess/tsconfig.json
index b01e4f4..a026d05 100644
--- a/packages/chess/tsconfig.json
+++ b/packages/chess/tsconfig.json
@@ -7,6 +7,6 @@
     "outDir": "dist",
     "rootDir": "src"
   },
-  "include": ["src/**/*", "e2e/**/*"],
+  "include": ["src/**/*"],
   "references": [{ "path": "../rete" }]
 }