diff --git a/apps/desktop/src/security.test.ts b/apps/desktop/src/security.test.ts
index 25cc01f05..0a88499f1 100644
--- a/apps/desktop/src/security.test.ts
+++ b/apps/desktop/src/security.test.ts
@@ -85,6 +85,25 @@ describe('desktop URL security', () => {
     assert.equal(normalizeDesktopDashboardPath('/tasks?status=open#recent'), '/tasks?status=open#recent');
   });
 
+  it('revalidates open links after canonical serialization', () => {
+    const rawPath = `/tasks/${'é '.repeat(300)}end`;
+    const rawLink = `propr://open?path=${rawPath}`;
+    const expandedCanonicalLink = new URL(rawLink).href;
+    assert.ok(rawLink.length < 2_048);
+    assert.ok(expandedCanonicalLink.length > 2_048);
+    assert.notEqual(dashboardPathFromDeepLink(rawLink), null);
+    assert.equal(dashboardPathFromDeepLink(expandedCanonicalLink), null);
+    assert.equal(normalizeDeepLink(rawLink), null);
+
+    const canonicalPrefix = 'propr://open?path=%2Ftasks%2F';
+    const suffix = 'a'.repeat(2_048 - canonicalPrefix.length);
+    const boundaryCanonicalLink = `${canonicalPrefix}${suffix}`;
+    assert.equal(boundaryCanonicalLink.length, 2_048);
+    assert.equal(new URL(boundaryCanonicalLink).href, boundaryCanonicalLink);
+    assert.equal(dashboardPathFromDeepLink(boundaryCanonicalLink), `/tasks/${suffix}`);
+    assert.equal(normalizeDeepLink(boundaryCanonicalLink), boundaryCanonicalLink);
+  });
+
   it('rejects encoded delimiters combined with encoded traversal', () => {
     const rejectedPaths = [
       '/tasks%23/%2e%2e/login',
diff --git a/apps/desktop/src/security.ts b/apps/desktop/src/security.ts
index f6d9a13d0..8b1695840 100644
--- a/apps/desktop/src/security.ts
+++ b/apps/desktop/src/security.ts
@@ -138,8 +138,16 @@ export const normalizeDeepLink = (value: string): string | null => {
   const url = parseUrl(value);
   if (!url || url.protocol !== `${DESKTOP_PROTOCOL}:` || hasCredentials(url)) return null;
   if (!DEEP_LINK_ACTIONS.has(url.hostname) || url.port || url.hash) return null;
-  if (url.hostname === 'open' && !dashboardPathFromDeepLink(value)) return null;
-  return url.href;
+  const dashboardPath = url.hostname === 'open' ? dashboardPathFromDeepLink(value) : null;
+  if (url.hostname === 'open' && dashboardPath === null) return null;
+
+  const canonicalCandidate = url.href;
+  if (canonicalCandidate.length > 2_048 || /[\u0000-\u001F\u007F]/.test(canonicalCandidate)) return null;
+  if (
+    url.hostname === 'open'
+    && dashboardPathFromDeepLink(canonicalCandidate) !== dashboardPath
+  ) return null;
+  return canonicalCandidate;
 };
 
 export const deepLinkFromArguments = (argv: readonly string[]): string | null => {
diff --git a/propr-ui/src/desktop-deep-link.test.ts b/propr-ui/src/desktop-deep-link.test.ts
index 8e42cb6db..b431da2ff 100644
--- a/propr-ui/src/desktop-deep-link.test.ts
+++ b/propr-ui/src/desktop-deep-link.test.ts
@@ -34,6 +34,28 @@ describe('desktop open deep-link navigation', () => {
     expect(navigate).toHaveBeenCalledWith('/tasks?status=open#recent');
   });
 
+  it('rejects an expanded canonical link and accepts one at the length limit', () => {
+    const navigate = vi.fn();
+    const navigation = new DesktopDeepLinkNavigation(navigate);
+    navigation.setDashboardReady();
+
+    const rawPath = `/tasks/${'é '.repeat(300)}end`;
+    const rawLink = `propr://open?path=${rawPath}`;
+    const expandedCanonicalLink = new URL(rawLink).href;
+    expect(rawLink.length).toBeLessThan(2_048);
+    expect(expandedCanonicalLink.length).toBeGreaterThan(2_048);
+    expect(navigation.receive(expandedCanonicalLink)).toBe(false);
+
+    const canonicalPrefix = 'propr://open?path=%2Ftasks%2F';
+    const suffix = 'a'.repeat(2_048 - canonicalPrefix.length);
+    const boundaryCanonicalLink = `${canonicalPrefix}${suffix}`;
+    expect(boundaryCanonicalLink).toHaveLength(2_048);
+    expect(new URL(boundaryCanonicalLink).href).toBe(boundaryCanonicalLink);
+    expect(navigation.receive(boundaryCanonicalLink)).toBe(true);
+    expect(navigate).toHaveBeenCalledOnce();
+    expect(navigate).toHaveBeenCalledWith(`/tasks/${suffix}`);
+  });
+
   it('does not route malformed or unsafe links before or after dashboard load', () => {
     const navigate = vi.fn();
     const navigation = new DesktopDeepLinkNavigation(navigate);