diff --git a/.superpowers/sdd/final-fix-4-report.md b/.superpowers/sdd/final-fix-4-report.md
new file mode 100644
index 0000000..217b10e
--- /dev/null
+++ b/.superpowers/sdd/final-fix-4-report.md
@@ -0,0 +1,12 @@
+# Final Fix 4 Report
+
+- Rejected raw server values containing backslashes and malformed HTTP-like prefixes before protocol-less normalization.
+- Added unit and Playwright coverage for malformed slash and backslash server inputs.
+- Added CustomLinkChannel tests for deferred clipboard success, rejection feedback, and unavailable clipboard feedback.
+
+Verification passed:
+
+- `npm test -- --run` (8 files, 48 tests)
+- `npm run build`
+- `npx playwright test` (11 tests)
+- `git diff --check`
diff --git a/apps/web/e2e/project-workbench.spec.ts b/apps/web/e2e/project-workbench.spec.ts
index 55f6ac3..1b67f8f 100644
--- a/apps/web/e2e/project-workbench.spec.ts
+++ b/apps/web/e2e/project-workbench.spec.ts
@@ -25,7 +25,17 @@ test('login and project channel workbench flow', async ({ page }) => {
   await expect(page.getByText('Open external channel')).toBeVisible();
 });
 
-for (const server of ['https://user:secret@example.com', 'http:////example.com', 'http://example..com', 'http://-bad.com']) {
+for (const server of [
+  'https://user:secret@example.com',
+  'http:////example.com',
+  'http//example.com',
+  'https//example.com',
+  'http:/example.com',
+  'https:/example.com',
+  'http://example.com\\path',
+  'http://example..com',
+  'http://-bad.com',
+]) {
   test(`rejects malformed server address: ${server}`, async ({ page }) => {
     await page.goto('/');
 
diff --git a/apps/web/src/features/auth/ServerLogin.svelte b/apps/web/src/features/auth/ServerLogin.svelte
index 32cc241..147724d 100644
--- a/apps/web/src/features/auth/ServerLogin.svelte
+++ b/apps/web/src/features/auth/ServerLogin.svelte
@@ -13,7 +13,7 @@
       return { error: 'Enter a server address.' };
     }
 
-    if (hasWhitespace(value) || hasUnsupportedProtocol(value)) {
+    if (hasWhitespace(value) || value.includes('\\') || hasMalformedHttpProtocol(value) || hasUnsupportedProtocol(value)) {
       return { error: 'Enter a valid HTTP or HTTPS server address.' };
     }
 
@@ -58,6 +58,10 @@
     return /^[a-z][a-z\d+.-]*:(?!\d)/i.test(value);
   }
 
+  function hasMalformedHttpProtocol(value: string): boolean {
+    return /^https?:\/(?!\/)/i.test(value) || /^https?\/{2}(?!\/)/i.test(value);
+  }
+
   function hasCredentials(value: string): boolean {
     const authority = value.replace(/^https?:\/\//i, '').split(/[/?#]/, 1)[0];
     return authority.includes('@');
diff --git a/apps/web/src/features/auth/ServerLogin.test.ts b/apps/web/src/features/auth/ServerLogin.test.ts
index 0343ba7..e8a617c 100644
--- a/apps/web/src/features/auth/ServerLogin.test.ts
+++ b/apps/web/src/features/auth/ServerLogin.test.ts
@@ -76,6 +76,12 @@ describe('ServerLogin', () => {
     ['http://', 'Enter a valid HTTP or HTTPS server address.'],
     ['ftp://example.com', 'Enter a valid HTTP or HTTPS server address.'],
     ['http:////example.com', 'Enter a valid HTTP or HTTPS server address.'],
+    ['http//example.com', 'Enter a valid HTTP or HTTPS server address.'],
+    ['https//example.com', 'Enter a valid HTTP or HTTPS server address.'],
+    ['http:/example.com', 'Enter a valid HTTP or HTTPS server address.'],
+    ['https:/example.com', 'Enter a valid HTTP or HTTPS server address.'],
+    ['http://example.com\\path', 'Enter a valid HTTP or HTTPS server address.'],
+    ['example.com\\path', 'Enter a valid HTTP or HTTPS server address.'],
     ['http://example..com', 'Enter a valid HTTP or HTTPS server address.'],
     ['http://-bad.com', 'Enter a valid HTTP or HTTPS server address.'],
     ['http://bad-.com', 'Enter a valid HTTP or HTTPS server address.'],
diff --git a/apps/web/src/features/workbench/channels/CustomLinkChannel.test.ts b/apps/web/src/features/workbench/channels/CustomLinkChannel.test.ts
index 8f8e845..e968295 100644
--- a/apps/web/src/features/workbench/channels/CustomLinkChannel.test.ts
+++ b/apps/web/src/features/workbench/channels/CustomLinkChannel.test.ts
@@ -1,6 +1,6 @@
 import '@testing-library/jest-dom/vitest';
 import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/svelte';
-import { afterEach, describe, expect, it } from 'vitest';
+import { afterEach, describe, expect, it, vi } from 'vitest';
 import CustomLinkChannel from './CustomLinkChannel.svelte';
 
 const channel = {
@@ -14,6 +14,13 @@ const channel = {
 };
 const originalClipboard = Object.getOwnPropertyDescriptor(navigator, 'clipboard');
 
+function setClipboard(writeText: Clipboard['writeText']) {
+  Object.defineProperty(navigator, 'clipboard', {
+    configurable: true,
+    value: { writeText } as Clipboard,
+  });
+}
+
 afterEach(() => {
   cleanup();
   if (originalClipboard) {
@@ -24,6 +31,33 @@ afterEach(() => {
 });
 
 describe('CustomLinkChannel', () => {
+  it('shows copy success only after clipboard writing resolves', async () => {
+    let resolveWrite: (() => void) | undefined;
+    const writeText = vi.fn(
+      () =>
+        new Promise<void>((resolve) => {
+          resolveWrite = resolve;
+        }),
+    );
+    setClipboard(writeText);
+    render(CustomLinkChannel, { props: { channel } });
+
+    await fireEvent.click(screen.getByRole('button', { name: 'Copy URL' }));
+
+    expect(screen.queryByText('URL copied.')).not.toBeInTheDocument();
+    resolveWrite?.();
+    await waitFor(() => expect(screen.getByText('URL copied.')).toBeInTheDocument());
+  });
+
+  it('reports a copy failure when clipboard writing rejects', async () => {
+    setClipboard(vi.fn().mockRejectedValue(new Error('Permission denied')));
+    render(CustomLinkChannel, { props: { channel } });
+
+    await fireEvent.click(screen.getByRole('button', { name: 'Copy URL' }));
+
+    await waitFor(() => expect(screen.getByText('Unable to copy URL.')).toBeInTheDocument());
+  });
+
   it('reports unavailable clipboard access without showing URL copied', async () => {
     Reflect.deleteProperty(navigator, 'clipboard');
     render(CustomLinkChannel, { props: { channel } });