diff --git a/ui/tests/unit/components/ui/code-editor-usage-contract.test.ts b/ui/tests/unit/components/ui/code-editor-usage-contract.test.ts
new file mode 100644
index 00000000..7175b8d8
--- /dev/null
+++ b/ui/tests/unit/components/ui/code-editor-usage-contract.test.ts
@@ -0,0 +1,42 @@
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+import { describe, expect, it } from 'vitest';
+
+const boundedConsumers = [
+  {
+    file: 'src/pages/cliproxy-ai-providers.tsx',
+    expectedCount: 2,
+  },
+  {
+    file: 'src/components/cliproxy/provider-editor/raw-editor-section.tsx',
+    expectedCount: 1,
+  },
+  {
+    file: 'src/components/profiles/editor/raw-editor-section.tsx',
+    expectedCount: 1,
+  },
+  {
+    file: 'src/components/copilot/config-form/raw-editor-section.tsx',
+    expectedCount: 1,
+  },
+  {
+    file: 'src/components/compatible-cli/raw-json-settings-editor-panel.tsx',
+    expectedCount: 1,
+  },
+  {
+    file: 'src/components/shared/settings-dialog.tsx',
+    expectedCount: 1,
+  },
+] as const;
+
+describe('bounded CodeEditor consumers', () => {
+  it.each(boundedConsumers)('$file opts into fill-parent mode for every bounded editor', ({
+    file,
+    expectedCount,
+  }) => {
+    const source = readFileSync(resolve(process.cwd(), file), 'utf8');
+    const matches = source.match(/heightMode="fill-parent"/g) ?? [];
+
+    expect(matches).toHaveLength(expectedCount);
+  });
+});
diff --git a/ui/tests/unit/components/ui/code-editor.test.tsx b/ui/tests/unit/components/ui/code-editor.test.tsx
new file mode 100644
index 00000000..3a8d71cc
--- /dev/null
+++ b/ui/tests/unit/components/ui/code-editor.test.tsx
@@ -0,0 +1,60 @@
+import { describe, expect, it, vi } from 'vitest';
+import { render, screen } from '@tests/setup/test-utils';
+
+import { CodeEditor } from '@/components/shared/code-editor';
+
+vi.mock('@/hooks/use-theme', () => ({
+  useTheme: () => ({ isDark: false }),
+}));
+
+describe('CodeEditor', () => {
+  it('creates an internal scroll viewport in fill-parent mode and keeps status outside it', () => {
+    const { container } = render(
+      <CodeEditor
+        value={'{\n  "provider": "openrouter"\n}'}
+        onChange={vi.fn()}
+        language="json"
+        minHeight="100%"
+        heightMode="fill-parent"
+      />
+    );
+
+    const viewport = container.querySelector('[data-slot="code-editor-viewport"]');
+
+    expect(viewport).toBeInTheDocument();
+    expect(viewport).toHaveStyle({ height: '100%' });
+    expect(viewport).not.toContainElement(screen.getByText('Valid JSON'));
+  });
+
+  it('keeps readonly status outside the scroll viewport for bounded editors', () => {
+    const { container } = render(
+      <CodeEditor
+        value={'{\n  "provider": "openrouter"\n}'}
+        onChange={vi.fn()}
+        language="json"
+        readonly
+        minHeight="calc(60vh - 120px)"
+        heightMode="fill-parent"
+      />
+    );
+
+    const viewport = container.querySelector('[data-slot="code-editor-viewport"]');
+    const textarea = container.querySelector('textarea');
+
+    expect(viewport).toHaveStyle({ height: 'calc(60vh - 120px)' });
+    expect(textarea).toBeDisabled();
+    expect(viewport).not.toContainElement(screen.getByText('(Read-only)'));
+  });
+
+  it('preserves content mode as the default layout contract', () => {
+    const { container } = render(
+      <CodeEditor
+        value={'{\n  "provider": "openrouter"\n}'}
+        onChange={vi.fn()}
+        language="json"
+      />
+    );
+
+    expect(container.querySelector('[data-slot="code-editor-viewport"]')).not.toBeInTheDocument();
+  });
+});