From 173c1c8b6165ccffd4d46abdf005e6aa7fe64cf9 Mon Sep 17 00:00:00 2001
From: Seongho Bae <me@seonghobae.me>
Date: Tue, 11 Aug 2026 19:38:12 +0900
Subject: [PATCH 1/3] test: prove editor direction fails closed at runtime

---
 .../editorAccessibilityRuntime.test.ts           | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 src/components/editorAccessibilityRuntime.test.ts

diff --git a/src/components/editorAccessibilityRuntime.test.ts b/src/components/editorAccessibilityRuntime.test.ts
new file mode 100644
index 00000000..1f42c9df
--- /dev/null
+++ b/src/components/editorAccessibilityRuntime.test.ts
@@ -0,0 +1,16 @@
+import { describe, expect, it } from 'vitest';
+import { buildEditorAccessibilityAttributes } from './editorAccessibility.js';
+
+describe('editor accessibility runtime contracts', () => {
+  it('rejects a runtime text direction outside the public enumerated states', () => {
+    expect(() =>
+      buildEditorAccessibilityAttributes({
+        defaultLabel: 'Editor',
+        editable: true,
+        textDirection: 'sideways' as never,
+      }),
+    ).toThrowError(
+      new RangeError('Editor text direction must be ltr, rtl, or auto.'),
+    );
+  });
+});

From 579e803ff2497936f304d3c63dbcca443fb13d05 Mon Sep 17 00:00:00 2001
From: Seongho Bae <me@seonghobae.me>
Date: Tue, 11 Aug 2026 19:44:24 +0900
Subject: [PATCH 2/3] test: cover every supported editor direction

---
 src/components/editorAccessibilityRuntime.test.ts | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/components/editorAccessibilityRuntime.test.ts b/src/components/editorAccessibilityRuntime.test.ts
index 1f42c9df..04ce1ea4 100644
--- a/src/components/editorAccessibilityRuntime.test.ts
+++ b/src/components/editorAccessibilityRuntime.test.ts
@@ -2,6 +2,19 @@ import { describe, expect, it } from 'vitest';
 import { buildEditorAccessibilityAttributes } from './editorAccessibility.js';
 
 describe('editor accessibility runtime contracts', () => {
+  it.each(['ltr', 'rtl', 'auto'] as const)(
+    'preserves the valid %s text direction',
+    (textDirection) => {
+      expect(
+        buildEditorAccessibilityAttributes({
+          defaultLabel: 'Editor',
+          editable: true,
+          textDirection,
+        }).dir,
+      ).toBe(textDirection);
+    },
+  );
+
   it('rejects a runtime text direction outside the public enumerated states', () => {
     expect(() =>
       buildEditorAccessibilityAttributes({

From 16d6a12f87bcf487102329b7ebbc5ca2b8652a56 Mon Sep 17 00:00:00 2001
From: Seongho Bae <me@seonghobae.me>
Date: Tue, 11 Aug 2026 19:45:14 +0900
Subject: [PATCH 3/3] fix: reject invalid runtime editor direction

---
 src/components/editorAccessibility.ts | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/components/editorAccessibility.ts b/src/components/editorAccessibility.ts
index f2cc1779..376a9a0b 100644
--- a/src/components/editorAccessibility.ts
+++ b/src/components/editorAccessibility.ts
@@ -37,6 +37,20 @@ function normalizedAccessibilityValue(
   return normalized ? normalized : undefined;
 }
 
+/** Reject runtime direction values outside Inkspan's public finite contract. */
+function validateEditorTextDirection(
+  value: EditorTextDirection | undefined,
+): void {
+  if (
+    value !== undefined &&
+    value !== 'ltr' &&
+    value !== 'rtl' &&
+    value !== 'auto'
+  ) {
+    throw new RangeError('Editor text direction must be ltr, rtl, or auto.');
+  }
+}
+
 /**
  * Normalize the shared visual and semantic empty-editor guidance.
  *
@@ -61,6 +75,7 @@ export function normalizeEditorPlaceholder(
 export function buildEditorAccessibilityAttributes(
   options: EditorAccessibilityOptions,
 ): Record<string, string> {
+  validateEditorTextDirection(options.textDirection);
   const placeholder = normalizeEditorPlaceholder(options.placeholder);
   const languageTag = normalizedAccessibilityValue(options.languageTag);
   const labelledBy = normalizedAccessibilityValue(options.ariaLabelledBy);