diff --git a/docs/apk-repos.md b/docs/apk-repos.md
index 25c762a..d04ae1d 100644
--- a/docs/apk-repos.md
+++ b/docs/apk-repos.md
@@ -53,8 +53,10 @@ Adding fetches and validates the complete index **before saving** the source.
 Without a fingerprint, Frame Control verifies the JAR signature and remembers
 its signer: trust on first use (TOFU). This establishes continuity with the
 first server response, not independent publisher identity. Obtain the published
-fingerprint through a trusted channel when possible. Re-adding an existing URL
-preserves its pin; changing it requires deliberately removing and re-adding it.
+fingerprint through a trusted channel when possible; the store's Add a source
+form shows the pinned one ("Trusted on first use: …") so you can compare it.
+Re-adding an existing URL preserves its pin; changing it requires deliberately
+removing and re-adding it.
 
 The API for the search/server integration is in `ui/apk_sources/fdroid.py`:
 `add_repo(url, fingerprint=None, name=None)`, `remove_repo(source_id)`,
diff --git a/tests/test_apk_search.py b/tests/test_apk_search.py
index ec92e54..b7edfe1 100644
--- a/tests/test_apk_search.py
+++ b/tests/test_apk_search.py
@@ -243,9 +243,32 @@ class EndpointTests(SettingsTest):
         self.assertEqual(code, 400)
         self.assertIn('not available', reply['error'])
         mod = fake('fdroid')
-        mod.add_repo, mod.remove_repo, mod.set_enabled = Mock(), Mock(), Mock()
+        added = {'id': 'fdroid-user-1', 'name': 'repo.example', 'fingerprint': 'ab' * 32, 'trust_on_first_use': True}
+        mod.add_repo, mod.remove_repo, mod.set_enabled = Mock(return_value=added), Mock(), Mock()
         with patch.object(search, 'modules', return_value=([mod], [])):
-            self.assertEqual(self.request('POST', '/api/sources', {'action': 'add', 'url': 'https://repo.example/repo'})[0], 200)
+            code, reply = self.request('POST', '/api/sources', {'action': 'add', 'url': 'https://repo.example/repo'})
+            self.assertEqual(code, 200)
+            job = self.wait(reply['job'])
+            self.assertEqual(job['message'], 'Added repo.example. Trusted on first use: ' + 'AB' * 32)
+            self.assertEqual(job['result']['source']['fingerprint'], 'ab' * 32)
             mod.add_repo.assert_called_once_with(url='https://repo.example/repo', fingerprint=None, name=None)
+            link = 'fdroidrepos://repo.example/repo?fingerprint=' + 'ab' * 32
+            mod.add_repo.return_value = dict(added, trust_on_first_use=False)
+            job = self.wait(self.request('POST', '/api/sources', {'action': 'add', 'url': link})[1]['job'])
+            self.assertEqual(job['message'], 'Added repo.example')
+            mod.add_repo.assert_called_with(url=link, fingerprint=None, name=None)
+            mod.add_repo.side_effect = SourceError('repository fingerprint mismatch')
+            job = self.wait(self.request('POST', '/api/sources', {'action': 'add', 'url': link})[1]['job'])
+            self.assertEqual(job['error'], 'repository fingerprint mismatch')  # no "SourceError:" prefix
+            for url in ('http://repo.example/repo', 'fdroidrepo://repo.example/repo', 'https://u@repo.example/'):
+                self.assertEqual(self.request('POST', '/api/sources', {'action': 'add', 'url': url})[0], 400)
             self.assertEqual(self.request('POST', '/api/sources', {'action': 'remove', 'source': 'fdroid'})[0], 200)
             mod.remove_repo.assert_called_once_with(source_id='fdroid')
+
+    def wait(self, job_id):
+        for _ in range(200):
+            job = self.request('GET', '/api/job?id=' + job_id)[1]
+            if job['done']:
+                return job
+            time.sleep(.01)
+        self.fail('job did not finish')
diff --git a/ui/apk_sources/search.py b/ui/apk_sources/search.py
index 197596c..ddc7289 100644
--- a/ui/apk_sources/search.py
+++ b/ui/apk_sources/search.py
@@ -98,10 +98,16 @@ def set_enabled(source_id, enabled):
     return {'message': source['name'] + (' enabled' if enabled else ' disabled')}
 
 
+def repo_module():
+    module = next((m for m in modules()[0] if m.KIND == 'fdroid'), None)
+    if module is None or not hasattr(module, 'add_repo'):
+        raise SourceError('User repositories are not available in this build')
+    return module
+
+
 def manage_repo(action, **kwargs):
-    mods, _ = modules()
-    module = next((m for m in mods if m.KIND == 'fdroid'), None)
-    if module is None or not hasattr(module, action):
+    module = repo_module()
+    if not hasattr(module, action):
         raise SourceError('User repositories are not available in this build')
     return getattr(module, action)(**kwargs)
 
diff --git a/ui/index.html b/ui/index.html
index 833500f..72497b2 100644
--- a/ui/index.html
+++ b/ui/index.html
@@ -2080,7 +2080,14 @@ $("detailBody").onchange=e=>{if(e.target.name==='storeOffer'){sourceState.detail
 $("sourcesOpen").onclick=()=>{loadSources();$('sourcesDialog').showModal();};
 $("sourcesList").onchange=e=>{if(e.target.matches('[data-enable]'))changeSource({action:'enable',source:e.target.dataset.enable,enabled:e.target.checked});};
 $("sourcesList").onclick=e=>{const b=e.target.closest('[data-remove]');if(b)changeSource({action:'remove',source:b.dataset.remove});};
-$("addSource").onsubmit=e=>{e.preventDefault();const f=new FormData(e.target);changeSource({action:'add',url:f.get('url'),fingerprint:f.get('fingerprint')});};
+async function addSource(body) {
+  $("sourceError").textContent="Checking the repository. Large ones can take a minute…";
+  let error="";
+  const result=await runJob('Add repository',`repo:${body.url}`,()=>api('/api/sources',body).catch(e=>{error=e.message;throw e;}),j=>{error=j.error||"";});
+  $("sourceError").textContent=result ? result.message : error || "We couldn't add that repository.";
+  if(result){$("addSource").reset();sourceState.source='';await loadSources();await searchSources();}
+}
+$("addSource").onsubmit=e=>{e.preventDefault();const f=new FormData(e.target);addSource({action:'add',url:f.get('url'),fingerprint:f.get('fingerprint')});};
 document.querySelectorAll('[data-close]').forEach(b=>b.onclick=()=>$(b.dataset.close).close());
 $('appDetail').addEventListener('close',()=>{sourceState.detailRequest++;});
 document.querySelectorAll('[data-store-tab]').forEach(b=>b.onclick=()=>{const browse=b.dataset.storeTab==='browse';$('appStore').hidden=!browse;$('androidLibrary').hidden=browse;$('repNew').hidden=browse;$('sourcesOpen').hidden=!browse;document.querySelectorAll('[data-store-tab]').forEach(t=>{t.classList.toggle('on',t===b);t.setAttribute('aria-pressed',t===b);});if(!browse)loadAndroid();});
diff --git a/ui/server.py b/ui/server.py
index dbc8ad2..e374460 100755
--- a/ui/server.py
+++ b/ui/server.py
@@ -167,6 +167,8 @@ def start_job(label, work, progress=False):
             fields = {"message": result.get("message") or f"{label}: done", "result": result}
         except (Failure, frame_android.FrameError) as e:
             fields = {"error": unreachable(str(e)) or str(e)}
+        except SourceError as e:  # already user-readable, and about a store, not the Frame
+            fields = {"error": str(e)}
         except Exception as e:
             fields = {"error": f"{type(e).__name__}: {e}"}
         finally:
@@ -1278,11 +1280,20 @@ def source_manage(body):
             return apk_search.set_enabled(source_text(body, 'source'), body['enabled'])
         if action == 'add':
             url = source_text(body, 'url')
-            if urlparse(url).scheme != 'https' or not urlparse(url).hostname or urlparse(url).username:
-                raise Failure('Use an HTTPS repository URL without credentials', 400)
-            apk_search.manage_repo('add_repo', url=url, fingerprint=source_text(body, 'fingerprint', True),
-                                   name=source_text(body, 'name', True))
-            return {'message': 'Repository added'}
+            fingerprint, name = source_text(body, 'fingerprint', True), source_text(body, 'name', True)
+            parts = urlparse(url)
+            if parts.scheme not in ('https', 'fdroidrepos') or not parts.hostname or parts.username:
+                raise Failure('Use an HTTPS or fdroidrepos:// repository URL without credentials', 400)
+            apk_search.repo_module()  # fail now if this build can't manage repositories
+
+            def add():  # downloads and verifies the whole index: a job, not a request
+                source = apk_search.manage_repo('add_repo', url=url, fingerprint=fingerprint, name=name)
+                message = 'Added ' + source['name']
+                if source.get('trust_on_first_use'):
+                    message += '. Trusted on first use: ' + source['fingerprint'].upper()
+                return {'message': message, 'source': {k: source.get(k) for k in
+                                                       ('id', 'name', 'fingerprint', 'trust_on_first_use')}}
+            return start_job('Add repository', add)
         if action == 'remove':
             apk_search.manage_repo('remove_repo', source_id=source_text(body, 'source'))
             return {'message': 'Repository removed'}