diff --git a/src/repo_registry/repo_ingestion/git.py b/src/repo_registry/repo_ingestion/git.py
index c65f243..b327515 100644
--- a/src/repo_registry/repo_ingestion/git.py
+++ b/src/repo_registry/repo_ingestion/git.py
@@ -63,14 +63,20 @@ class GitIngestionService:
     def _run_git(self, args: list[str], *, cwd: Path | None) -> None:
         if shutil.which("git") is None:
             raise RuntimeError("git executable was not found")
-        result = subprocess.run(
-            ["git", *args],
-            cwd=cwd,
-            check=False,
-            capture_output=True,
-            text=True,
-            timeout=120,
-        )
+        command = ["git", *args]
+        try:
+            result = subprocess.run(
+                command,
+                cwd=cwd,
+                check=False,
+                capture_output=True,
+                text=True,
+                timeout=120,
+            )
+        except subprocess.TimeoutExpired as exc:
+            raise RuntimeError(
+                f"git {' '.join(args)} timed out after {exc.timeout} seconds"
+            ) from exc
         if result.returncode != 0:
             message = result.stderr.strip() or result.stdout.strip()
             raise RuntimeError(f"git {' '.join(args)} failed: {message}")
diff --git a/src/repo_registry/web_ui/views.py b/src/repo_registry/web_ui/views.py
index 328d992..b8bbc7f 100644
--- a/src/repo_registry/web_ui/views.py
+++ b/src/repo_registry/web_ui/views.py
@@ -34,6 +34,8 @@ def page(title: str, body: str) -> HTMLResponse:
                 --accent: #0f766e;
                 --accent-dark: #115e59;
                 --warn: #9a3412;
+                --danger: #b42318;
+                --danger-bg: #fff4f2;
               }}
               * {{ box-sizing: border-box; }}
               body {{
@@ -64,6 +66,17 @@ def page(title: str, body: str) -> HTMLResponse:
                 border-radius: 8px;
                 padding: 16px;
               }}
+              .notice {{
+                border: 1px solid var(--line);
+                border-radius: 8px;
+                padding: 10px 12px;
+                margin-bottom: 12px;
+              }}
+              .notice.error {{
+                border-color: #f3b8ae;
+                background: var(--danger-bg);
+                color: var(--danger);
+              }}
               .stack {{ display: grid; gap: 12px; }}
               .muted {{ color: var(--muted); }}
               .pill {{
@@ -111,6 +124,9 @@ def page(title: str, body: str) -> HTMLResponse:
               .tree li {{ margin: 6px 0; }}
               .source {{ color: var(--muted); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: 12px; }}
               .actions {{ display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }}
+              [data-pending] {{ display: none; color: var(--muted); }}
+              form.is-submitting [data-pending] {{ display: inline; }}
+              form.is-submitting button[type="submit"] {{ opacity: .7; cursor: wait; }}
               @media (max-width: 780px) {{
                 header {{ padding: 12px 16px; }}
                 main {{ padding: 16px; }}
@@ -132,14 +148,28 @@ def page(title: str, body: str) -> HTMLResponse:
               </nav>
             </header>
             <main>{body}</main>
+            <script>
+              document.addEventListener("submit", (event) => {{
+                const form = event.target;
+                if (form instanceof HTMLFormElement) {{
+                  form.classList.add("is-submitting");
+                  const button = form.querySelector('button[type="submit"]');
+                  if (button) button.setAttribute("disabled", "disabled");
+                }}
+              }});
+            </script>
           </body>
         </html>
         """
     )
 
 
-@router.get("/ui")
-def repository_index(service: RegistryService = Depends(get_service)) -> HTMLResponse:
+def render_repository_index(
+    service: RegistryService,
+    *,
+    error_message: str | None = None,
+    status_code: int = 200,
+) -> HTMLResponse:
     repositories = service.list_repositories()
     rows = "\n".join(
         f"""
@@ -152,15 +182,29 @@ def repository_index(service: RegistryService = Depends(get_service)) -> HTMLRes
         """
         for repo in repositories
     )
+    error = (
+        f"""
+        <div class="notice error" role="alert">
+          <strong>Registration failed.</strong>
+          <p>{escape(error_message)}</p>
+        </div>
+        """
+        if error_message
+        else ""
+    )
     body = f"""
     <h1>Repositories</h1>
+    {error}
     <div class="grid">
       <section class="panel">
         <h2>Register Repository</h2>
         <form class="stack" method="post" action="/ui/repos">
           <label>Git URL or local path <input name="url" required></label>
           <label>Branch <input name="branch" value="main"></label>
-          <button type="submit">Register</button>
+          <div class="actions">
+            <button type="submit">Register</button>
+            <span data-pending>Registering repository...</span>
+          </div>
         </form>
       </section>
       <section class="panel">
@@ -175,7 +219,14 @@ def repository_index(service: RegistryService = Depends(get_service)) -> HTMLRes
       </section>
     </div>
     """
-    return page("Repositories", body)
+    response = page("Repositories", body)
+    response.status_code = status_code
+    return response
+
+
+@router.get("/ui")
+def repository_index(service: RegistryService = Depends(get_service)) -> HTMLResponse:
+    return render_repository_index(service)
 
 
 @router.get("/ui/discovery")
@@ -360,11 +411,18 @@ def create_repository_from_form(
     url: str = Form(...),
     branch: str = Form("main"),
     service: RegistryService = Depends(get_service),
-) -> RedirectResponse:
-    repository = service.register_repository(
-        url=url,
-        branch=branch or "main",
-    )
+):
+    try:
+        repository = service.register_repository(
+            url=url,
+            branch=branch or "main",
+        )
+    except (RuntimeError, ValueError) as exc:
+        return render_repository_index(
+            service,
+            error_message=str(exc),
+            status_code=400,
+        )
     return RedirectResponse(f"/ui/repos/{repository.id}", status_code=303)
 
 
diff --git a/tests/test_web_api.py b/tests/test_web_api.py
index f07cc73..ec7a59c 100644
--- a/tests/test_web_api.py
+++ b/tests/test_web_api.py
@@ -1073,6 +1073,7 @@ def test_ui_register_analyze_and_approve_loop(tmp_path):
         index_response = client.get("/ui")
         assert index_response.status_code == 200
         assert "Register Repository" in index_response.text
+        assert "Registering repository..." in index_response.text
 
         create_response = client.post(
             "/ui/repos",
@@ -1201,6 +1202,32 @@ def test_ui_register_analyze_and_approve_loop(tmp_path):
         app.dependency_overrides.clear()
 
 
+def test_ui_registration_failure_returns_feedback(tmp_path):
+    def override_settings():
+        return Settings(
+            database_path=str(tmp_path / "ui-error.sqlite3"),
+            checkout_root=str(tmp_path / "ui-error-checkouts"),
+        )
+
+    app.dependency_overrides[get_settings] = override_settings
+    client = TestClient(app)
+    try:
+        response = client.post(
+            "/ui/repos",
+            data={
+                "url": str(tmp_path / "missing-repo"),
+                "branch": "main",
+            },
+        )
+
+        assert response.status_code == 400
+        assert "Registration failed." in response.text
+        assert "git clone" in response.text
+        assert "Register Repository" in response.text
+    finally:
+        app.dependency_overrides.clear()
+
+
 def test_ui_manual_registry_entry_loop(tmp_path):
     source = tmp_path / "manual-repo"
     source.mkdir()
diff --git a/workplans/RREG-WP-0003-automatic-repository-exploration.md b/workplans/RREG-WP-0003-automatic-repository-exploration.md
index 3af9df3..80b4429 100644
--- a/workplans/RREG-WP-0003-automatic-repository-exploration.md
+++ b/workplans/RREG-WP-0003-automatic-repository-exploration.md
@@ -27,7 +27,7 @@ configured trusted automation mode.
 
 ```task
 id: RREG-WP-0003-T01
-status: todo
+status: in_progress
 priority: high
 state_hub_task_id: "ab718ce7-d38f-4080-9385-99be1bf80475"
 ```