diff --git a/.Jules/palette.md b/.Jules/palette.md
new file mode 100644
index 0000000..6f311d1
--- /dev/null
+++ b/.Jules/palette.md
@@ -0,0 +1,3 @@
+## 2024-05-18 - Async Loading States with Mock APIs
+**Learning:** When adding UI loading states (spinners, disabled buttons) to applications using an in-memory mock client that bypasses the native `fetch` API, transitions happen instantly, making the loading state imperceptible to users and untestable. Furthermore, using `e.submitter` to manipulate the submit button requires carefully handling the original state restoration within a `finally` block to guarantee recovery regardless of API outcome.
+**Action:** Always introduce an explicit awaitable delay (e.g., `await new Promise(resolve => setTimeout(resolve, delay))`) when simulating mock async behavior so UX loading states are visible. When manipulating submit buttons during forms, capture the `e.submitter` context safely, apply states (`disabled`, `aria-busy`), and strictly reset those states in a `finally` block.
diff --git a/web-demo/js/app.js b/web-demo/js/app.js
index 11508de..45b2dab 100644
--- a/web-demo/js/app.js
+++ b/web-demo/js/app.js
@@ -144,9 +144,19 @@ class ClimaAI {
         e.preventDefault();
         const email = document.getElementById('loginEmail').value;
         const password = document.getElementById('loginPassword').value;
+        const submitBtn = e.submitter;
+        let originalContent = '';
+
+        if (submitBtn) {
+            originalContent = submitBtn.innerHTML;
+            submitBtn.disabled = true;
+            submitBtn.setAttribute('aria-busy', 'true');
+            submitBtn.innerHTML = 'Signing in...';
+        }
 
         try {
             this.showToast('Logging in...', 'info');
+            await new Promise(resolve => setTimeout(resolve, 500)); // Make mock loading perceptible
             const response = await api.login(email, password);
             this.user = response.user;
             this.showToast('Welcome back! 🌤️', 'success');
@@ -155,6 +165,12 @@ class ClimaAI {
             this.checkSubscription();
         } catch (error) {
             this.showToast(error.message || 'Login failed', 'error');
+        } finally {
+            if (submitBtn) {
+                submitBtn.disabled = false;
+                submitBtn.removeAttribute('aria-busy');
+                submitBtn.innerHTML = originalContent;
+            }
         }
     }
 
@@ -163,9 +179,19 @@ class ClimaAI {
         const name = document.getElementById('registerName').value;
         const email = document.getElementById('registerEmail').value;
         const password = document.getElementById('registerPassword').value;
+        const submitBtn = e.submitter;
+        let originalContent = '';
+
+        if (submitBtn) {
+            originalContent = submitBtn.innerHTML;
+            submitBtn.disabled = true;
+            submitBtn.setAttribute('aria-busy', 'true');
+            submitBtn.innerHTML = 'Signing up...';
+        }
 
         try {
             this.showToast('Creating account...', 'info');
+            await new Promise(resolve => setTimeout(resolve, 500)); // Make mock loading perceptible
             const response = await api.register(email, password, name);
             this.user = response.user;
             this.showToast('Account created! Welcome! 🎉', 'success');
@@ -174,6 +200,12 @@ class ClimaAI {
             this.checkSubscription();
         } catch (error) {
             this.showToast(error.message || 'Registration failed', 'error');
+        } finally {
+            if (submitBtn) {
+                submitBtn.disabled = false;
+                submitBtn.removeAttribute('aria-busy');
+                submitBtn.innerHTML = originalContent;
+            }
         }
     }