diff --git a/packages/runtime-tests/integration/components/box-in-text-validation.test.tsx b/packages/runtime-tests/integration/components/box-in-text-validation.test.tsx
index 7c3487f..866015c 100644
--- a/packages/runtime-tests/integration/components/box-in-text-validation.test.tsx
+++ b/packages/runtime-tests/integration/components/box-in-text-validation.test.tsx
@@ -1,20 +1,14 @@
 import { defineComponent } from "vue";
-import { expect, test, vi } from "vite-plus/test";
+import { expect, test } from "vite-plus/test";
 import { render } from "@vue-tui/testing";
 import { Box, Text } from "@vue-tui/runtime";
 
-test("<Box> inside <Text> emits a dev warning", async () => {
-  const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+test("<Box> inside <Text> throws an error", async () => {
+  const App = defineComponent(() => () => (
+    <Text>
+      <Box />
+    </Text>
+  ));
 
-  await render(
-    defineComponent(() => () => (
-      <Text>
-        <Box>invalid</Box>
-      </Text>
-    )),
-  );
-
-  expect(warnSpy).toHaveBeenCalledWith(expect.stringContaining("<Box>"));
-
-  warnSpy.mockRestore();
+  await expect(render(App)).rejects.toThrow("can’t be nested inside <Text>");
 });
diff --git a/packages/runtime-tests/integration/lifecycle/error-handling.test.tsx b/packages/runtime-tests/integration/lifecycle/error-handling.test.tsx
index 5416988..935b257 100644
--- a/packages/runtime-tests/integration/lifecycle/error-handling.test.tsx
+++ b/packages/runtime-tests/integration/lifecycle/error-handling.test.tsx
@@ -1,7 +1,7 @@
 import { defineComponent, nextTick, shallowRef } from "vue";
 import { expect, test } from "vite-plus/test";
 import { render } from "@vue-tui/testing";
-import { Text, useExit } from "@vue-tui/runtime";
+import { Box, Text, useExit } from "@vue-tui/runtime";
 
 test("setup() throw rejects render()", async () => {
   const Boom = defineComponent(() => {
@@ -77,22 +77,17 @@ test.todo(
 );
 
 // --- Ink error validation tests ---
-// In Ink these tests use React error boundaries to validate that:
-// 1. Raw text strings inside <Box> (not inside <Text>) throw an error
-// 2. A <Box> nested inside <Text> throws an error
-//
-// In vue-tui:
-// - Raw text-leaf nodes inside <Box> are silently allowed (no validation yet)
-// - <Box> inside <Text> causes a WASM yoga crash (table index out of bounds)
-// All three are marked todo until the runtime adds proper validation.
 
-test.todo(
-  "fail when text nodes are not within <Text> component — vue-tui silently allows text-leaf inside box; validation not yet implemented",
-);
+test("fail when Box nested inside Text", async () => {
+  const App = defineComponent(() => () => (
+    <Text>
+      <Box />
+    </Text>
+  ));
+  await expect(render(App)).rejects.toThrow("can’t be nested inside <Text>");
+});
 
-test.todo(
-  "fail when text node is not within <Text> component — vue-tui silently allows text-leaf inside box; validation not yet implemented",
-);
-
-// Resolved: <Box> inside <Text> now emits a dev warning and skips insertion
-// to prevent WASM crash. See box-in-text-validation.test.tsx.
+test("fail when text string not within Text component", async () => {
+  const App = defineComponent(() => () => <Box>bare text</Box>);
+  await expect(render(App)).rejects.toThrow("must be rendered inside <Text>");
+});
diff --git a/packages/runtime/src/host/node-ops.ts b/packages/runtime/src/host/node-ops.ts
index 2cf2b85..0b27676 100644
--- a/packages/runtime/src/host/node-ops.ts
+++ b/packages/runtime/src/host/node-ops.ts
@@ -142,19 +142,20 @@ export function buildNodeOps(options: TtyRendererOptions): RendererOptions<TuiNo
     }
     const parentC = parent as TuiContainer;
 
-    // Dev warning: <Box> inside <Text> is invalid (matches Ink's validation).
-    // Inserting a box into a text context corrupts the yoga WASM layout engine.
+    // <Box> inside <Text> is invalid (matches Ink's validation).
+    if (child.type === "box" && isInsideTextContext(parentC)) {
+      throw new Error("<Box> can’t be nested inside <Text> component");
+    }
+
+    // Text-leaf nodes must live inside a <Text> context.
+    // Skip empty text-leaves — Vue uses them as fragment anchors.
     if (
-      process.env["NODE_ENV"] !== "production" &&
-      child.type === "box" &&
-      isInsideTextContext(parentC)
+      child.type === "text-leaf" &&
+      child.value !== "" &&
+      (parentC.type === "box" || parentC.type === "root" || parentC.type === "static") &&
+      !isInsideTextContext(parentC)
     ) {
-      // eslint-disable-next-line no-console
-      console.warn(
-        "[vue-tui] A <Box> cannot be nested inside a <Text> component. " +
-          "Wrap it in a sibling <Box> instead.",
-      );
-      return; // Skip insertion to prevent WASM crash
+      throw new Error(`Text string "${child.value}" must be rendered inside <Text> component`);
     }
 
     // Move semantics: if the child is already mounted (Vue's keyed reorder