diff --git a/flash-messages/flash.tmpl b/flash-messages/flash.tmpl
index 956b796..779241c 100644
--- a/flash-messages/flash.tmpl
+++ b/flash-messages/flash.tmpl
@@ -11,33 +11,19 @@
         <h1>{{.Title}}</h1>
 
         <!-- Flash Messages Section -->
-        {{if .lvt.HasAnyFlash}}
-        <div id="flash-messages">
-            {{if .lvt.HasFlash "success"}}
-            <ins style="display:block;text-decoration:none" data-flash="success">{{.lvt.Flash "success"}}</ins>
-            {{end}}
-            {{if .lvt.HasFlash "error"}}
-            <del style="display:block;text-decoration:none" data-flash="error">{{.lvt.Flash "error"}}</del>
-            {{end}}
-            {{if .lvt.HasFlash "warning"}}
-            <ins style="display:block;text-decoration:none" data-flash="warning">{{.lvt.Flash "warning"}}</ins>
-            {{end}}
-            {{if .lvt.HasFlash "info"}}
-            <ins style="display:block;text-decoration:none" data-flash="info">{{.lvt.Flash "info"}}</ins>
-            {{end}}
-        </div>
-        {{end}}
+        {{.lvt.FlashTag "success"}}
+        {{.lvt.FlashTag "error"}}
+        {{.lvt.FlashTag "warning"}}
+        {{.lvt.FlashTag "info"}}
 
         <!-- Add Item Form -->
         <form method="POST" name="addItem">
             <input type="text"
                    name="item"
                    placeholder="Enter item name"
-                   {{if .lvt.HasError "item"}}aria-invalid="true"{{end}} />
-            <button type="submit" name="addItem">Add Item</button>
-            {{if .lvt.HasError "item"}}
-            <small>{{.lvt.Error "item"}}</small>
-            {{end}}
+                   {{.lvt.AriaInvalid "item"}} />
+            <button type="submit" name="addItem" {{.lvt.AriaDisabled "item"}}>Add Item</button>
+            {{.lvt.ErrorTag "item"}}
         </form>
 
         <!-- Action Buttons -->
@@ -78,7 +64,8 @@
                 <li>They don't affect <code>ResponseMetadata.Success</code></li>
                 <li>Types: <code>success</code>, <code>error</code>, <code>warning</code>, <code>info</code></li>
                 <li>Set via: <code>ctx.SetFlash("success", "message")</code></li>
-                <li>Read via: <code>.lvt.Flash "success"</code>, <code>.lvt.HasFlash "success"</code></li>
+                <li>Render via: <code>.lvt.FlashTag "success"</code> (recommended)</li>
+                <li>Or manually: <code>.lvt.HasFlash "key"</code>, <code>.lvt.Flash "key"</code></li>
             </ul>
         </blockquote>
     </main>
diff --git a/login/main.go b/login/main.go
index b288941..1b878e4 100644
--- a/login/main.go
+++ b/login/main.go
@@ -25,7 +25,6 @@ type AuthController struct {
 type AuthState struct {
 	Username      string    `lvt:"persist"`
 	IsLoggedIn    bool      `lvt:"persist"`
-	Error         string
 	ServerMessage string
 	LoginTime     time.Time `lvt:"persist"`
 }
@@ -35,20 +34,19 @@ func (c *AuthController) Login(state AuthState, ctx *livetemplate.Context) (Auth
 	username := ctx.GetString("username")
 	password := ctx.GetString("password")
 
-	// Simple validation
-	if username == "" || password == "" {
-		state.Error = "Username and password are required"
-		return state, nil
+	// Field-level validation
+	if username == "" {
+		return state, livetemplate.NewFieldError("username", fmt.Errorf("username is required"))
+	}
+	if password == "" {
+		return state, livetemplate.NewFieldError("password", fmt.Errorf("password is required"))
 	}
 
 	// Demo: accept any username with password "secret"
 	if password != "secret" {
-		state.Error = "Invalid credentials"
+		ctx.SetFlash("error", "Invalid credentials")
 		return state, nil
 	}
-
-	// Clear error and set logged in state
-	state.Error = ""
 	state.Username = username
 	state.IsLoggedIn = true
 	state.LoginTime = time.Now()
@@ -76,7 +74,6 @@ func (c *AuthController) Login(state AuthState, ctx *livetemplate.Context) (Auth
 func (c *AuthController) Logout(state AuthState, ctx *livetemplate.Context) (AuthState, error) {
 	state.Username = ""
 	state.IsLoggedIn = false
-	state.Error = ""
 	state.ServerMessage = ""
 
 	// Delete session cookie
diff --git a/login/templates/auth.html b/login/templates/auth.html
index e166d0c..5c4f457 100644
--- a/login/templates/auth.html
+++ b/login/templates/auth.html
@@ -31,18 +31,18 @@ <h1>Dashboard</h1>
         <!-- Login View -->
         <article>
             <h1>Login</h1>
-            {{if .Error}}
-            <del style="display:block;text-decoration:none">{{.Error}}</del>
-            {{end}}
+            {{.lvt.FlashTag "error"}}
             <!-- HTTP login — lvt-no-intercept forces real HTTP POST for cookie + redirect -->
             <form method="POST" lvt-no-intercept>
                 <label for="username">Username
-                    <input type="text" id="username" name="username" placeholder="Enter username" required>
+                    <input type="text" id="username" name="username" placeholder="Enter username" required {{.lvt.AriaInvalid "username"}}>
+                    {{.lvt.ErrorTag "username"}}
                 </label>
                 <label for="password">Password
-                    <input type="password" id="password" name="password" placeholder="Enter password" required>
+                    <input type="password" id="password" name="password" placeholder="Enter password" required {{.lvt.AriaInvalid "password"}}>
+                    {{.lvt.ErrorTag "password"}}
                 </label>
-                <button type="submit" name="login">Login</button>
+                <button type="submit" name="login" {{.lvt.AriaDisabled "username" "password"}}>Login</button>
             </form>
             <small>
                 Demo: Use any username with password <strong>secret</strong><br>
diff --git a/progressive-enhancement/progressive-enhancement.tmpl b/progressive-enhancement/progressive-enhancement.tmpl
index 79921e1..af43bcd 100644
--- a/progressive-enhancement/progressive-enhancement.tmpl
+++ b/progressive-enhancement/progressive-enhancement.tmpl
@@ -39,12 +39,8 @@
         </mark>
 
         <!-- Flash messages -->
-        {{if .lvt.Flash "success"}}
-        <ins style="display:block; text-decoration:none;">{{.lvt.Flash "success"}}</ins>
-        {{end}}
-        {{if .lvt.Flash "error"}}
-        <del style="display:block; text-decoration:none;">{{.lvt.Flash "error"}}</del>
-        {{end}}
+        {{.lvt.FlashTag "success"}}
+        {{.lvt.FlashTag "error"}}
 
         <!-- Add todo form -->
         <!-- Works with JS: client intercepts form and routes via WebSocket/fetch -->
@@ -56,13 +52,11 @@
                     name="title"
                     value="{{.InputTitle}}"
                     placeholder="What needs to be done?"
-                    {{if .lvt.HasError "title"}}aria-invalid="true"{{end}}
+                    {{.lvt.AriaInvalid "title"}}
                     autofocus
                 >
-                {{if .lvt.HasError "title"}}
-                <small>{{.lvt.Error "title"}}</small>
-                {{end}}
-                <button type="submit" name="add">Add Todo</button>
+                {{.lvt.ErrorTag "title"}}
+                <button type="submit" name="add" {{.lvt.AriaDisabled "title"}}>Add Todo</button>
             </form>
         </article>
 
diff --git a/todos/todos.tmpl b/todos/todos.tmpl
index 7da37d3..68962a1 100644
--- a/todos/todos.tmpl
+++ b/todos/todos.tmpl
@@ -11,13 +11,11 @@
         placeholder="What needs to be done?"
         required
         aria-required="true"
-        {{ if .lvt.HasError "text" }}aria-invalid="true"{{ end }}
+        {{.lvt.AriaInvalid "text"}}
       />
-      <button type="submit" name="add">Add</button>
+      <button type="submit" name="add" {{.lvt.AriaDisabled "text"}}>Add</button>
     </fieldset>
-    {{ if .lvt.HasError "text" }}
-      <del style="display:block;text-decoration:none">{{ .lvt.Error "text" }}</del>
-    {{ end }}
+    {{.lvt.ErrorTag "text"}}
   </form>
 {{ end }}
 
diff --git a/ws-disabled/ws-disabled.tmpl b/ws-disabled/ws-disabled.tmpl
index e1af344..bd2871b 100644
--- a/ws-disabled/ws-disabled.tmpl
+++ b/ws-disabled/ws-disabled.tmpl
@@ -12,12 +12,8 @@
         <p><small>WebSocket is disabled. The client library uses HTTP fetch for all actions
         and applies tree-based DOM updates without page reloads.</small></p>
 
-        {{if .lvt.Flash "success"}}
-        <ins style="display:block; text-decoration:none;">{{.lvt.Flash "success"}}</ins>
-        {{end}}
-        {{if .lvt.Flash "error"}}
-        <del style="display:block; text-decoration:none;">{{.lvt.Flash "error"}}</del>
-        {{end}}
+        {{.lvt.FlashTag "success"}}
+        {{.lvt.FlashTag "error"}}
 
         <article>
             <form method="POST" name="add">
@@ -25,21 +21,17 @@
                     <label>
                         Label
                         <input type="text" name="label" placeholder="My favorite site"
-                            {{if .lvt.HasError "label"}}aria-invalid="true"{{end}}>
-                        {{if .lvt.HasError "label"}}
-                        <small>{{.lvt.Error "label"}}</small>
-                        {{end}}
+                            {{.lvt.AriaInvalid "label"}}>
+                        {{.lvt.ErrorTag "label"}}
                     </label>
                     <label>
                         URL
                         <input type="url" name="url" placeholder="https://example.com"
-                            {{if .lvt.HasError "url"}}aria-invalid="true"{{end}}>
-                        {{if .lvt.HasError "url"}}
-                        <small>{{.lvt.Error "url"}}</small>
-                        {{end}}
+                            {{.lvt.AriaInvalid "url"}}>
+                        {{.lvt.ErrorTag "url"}}
                     </label>
                 </div>
-                <button type="submit" name="add">Add Bookmark</button>
+                <button type="submit" name="add" {{.lvt.AriaDisabled "label" "url"}}>Add Bookmark</button>
             </form>
         </article>