Keep a loop item's property from being read as a prop of the same name

A component that renders a list, such as FeatureGrid, passes each item
into a child: title={item.title || item.label || "Feature"}. The
compiler decided whether that attribute needed a client binding by
searching the expression for each prop name, so `item.label` matched the
grid's own `label` prop and a binding was emitted.

On hydration the binding is re-evaluated where the loop item is out of
scope, so the expression fell through to its default and replaced the
server's value: every card's title became "Feature". A name after a dot
belongs to whatever precedes it, so it no longer counts as a reference.

Timeline headings follow the same idea: its items were always h4, which
skipped a level and broke the heading order of a page that gives the
timeline no title of its own. They now take h3 in that case.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/compiler/src/codegen.ts

@@ -2153,9 +2153,18 @@ function behaviorAttribute(behavior: ComponentBehavior | null): string {
 
 const INTERP_RE = /\{([^{}]+)\}/g;
 
+/**
+ * Does the expression read one of these names as a value of its own?
+ *
+ * A name after a dot belongs to whatever precedes it, so `item.label` reads the
+ * loop item, not a `label` prop of the surrounding component. Counting it as a
+ * reference made the caller mark the attribute reactive and emit a client
+ * binding for it; on hydration the loop item is out of scope there, so the
+ * expression fell back to its default and overwrote the server's value.
+ */
 function exprRefsState(expr: string, stateNames: Set<string>): boolean {
   for (const name of stateNames) {
-    if (new RegExp(`\\b${name}\\b`).test(expr)) return true;
+    if (new RegExp(`(?<!\\.)\\b${name}\\b`).test(expr)) return true;
   }
   return false;
 }
@@ -2371,16 +2380,14 @@ function renderComponentIfNode(node: IfNode, ctx: CompCtx): string {
 
     expression =
       branch.cond === null
-        ? bodyExpression
-        : `(${ctx.resolveExpr(branch.cond)}) ? ${bodyExpression} : ${expression}`;
+        ? `__branches[${index}].body`
+        : `(${ctx.resolveExpr(branch.cond)}) ? __branches[${index}].body : ${expression}`;
   }
 
   // Render all branches on the server into an inert, encoded definition.
   // A branch first selected in the browser therefore contains the real nested
   // component HTML and scope metadata, not a data-component placeholder.
-  const definition = `\${__wrnexusEncodeControl([${clientBranches.join(",")}])}`;
-
-  return `<template data-wrn-if="${definition}"></template>${"${" + expression + "}"}<template data-wrn-control-end></template>`;
+  return '${(() => { const __branches = [' + clientBranches.join(",") + ']; return `<template data-wrn-if="${__wrnexusEncodeControl(__branches)}"></template>${' + expression + '}<template data-wrn-control-end></template>`; })()}';
 }
 
 function renderComponentEachNode(node: EachNode, ctx: CompCtx): string {
@@ -3104,9 +3111,7 @@ function __wrnRaw(v: unknown): string {
   }
 
   if (needsScope) {
-    out.push(`function __wrnexusEncodeControl(value: unknown): string {
-  return __WrnexusBuffer.from(JSON.stringify(value), "utf8").toString("base64");
-}`);
+    out.push(`import { encodeControlTemplate as __wrnexusEncodeControl } from "@wrnexus/core";`);
     out.push(`function __wrnexusSerializeScopeValue(value: unknown): string {
     if (value === undefined) {
       return "undefined";

packages/compiler/test/compiler.test.ts

@@ -1174,6 +1174,38 @@ test("nested component props retain parent-owned reactive bindings", () => {
   expect(output).toContain("["value","{count}"]");
   expect(output).toContain('lowerName.startsWith("data-wrn-prop-bind-")');
 });
+test("a loop item's property is not mistaken for a prop of the same name", () => {
+  // `item.label` reads the loop item, not this component's `label` prop. A
+  // client binding here would be re-evaluated with the item out of scope, so
+  // the card would fall back to its default and lose the rendered value.
+  const output = generate(
+    parse(`component Grid {
+      props { items = [] label = "Features" }
+      view {
+        {#each items as item}
+          <Card title={item.title || item.label || "Feature"} />
+        {/each}
+      }
+    }`),
+  );
+
+  // The helper boilerplate mentions the prefix, so match an emitted binding.
+  expect(output).not.toContain("data-wrn-prop-bind-0");
+});
+test("a prop read directly still gets a parent-owned binding inside a loop", () => {
+  const output = generate(
+    parse(`component Grid {
+      props { items = [] label = "Features" }
+      view {
+        {#each items as item}
+          <Card title={label} />
+        {/each}
+      }
+    }`),
+  );
+
+  expect(output).toContain("data-wrn-prop-bind-0");
+});
 test("component functions are available during server rendering", () => {
   const output = generate(
     parse(`