Optimize evaluator hot path: prototype-chain envs, imperative kwarg parsing

Three key optimizations to the JS evaluator platform layer:

1. envMerge uses Object.create() instead of copying all keys — O(own) vs O(all)
2. renderDomComponent/renderDomElement override: imperative kwarg/attr
   parsing replaces reduce+assoc pattern (no per-arg dict allocation)
3. callComponent/parseKeywordArgs override: same imperative pattern
   for the eval path (not just DOM rendering)

Wire format and spec semantics unchanged — these are host-level
performance overrides in the platform JS.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/static/scripts/sx-browser.js

@@ -14,7 +14,7 @@
   // =========================================================================
 
   var NIL = Object.freeze({ _nil: true, toString: function() { return "nil"; } });
-  var SX_VERSION = "2026-03-07T01:23:32Z";
+  var SX_VERSION = "2026-03-07T01:41:53Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
@@ -174,8 +174,12 @@
   function envHas(env, name) { return name in env; }
   function envGet(env, name) { return env[name]; }
   function envSet(env, name, val) { env[name] = val; }
-  function envExtend(env) { return merge(env); }
+  function envExtend(env) { return Object.create(env); }
-  function envMerge(base, overlay) { return merge(base, overlay); }
+  function envMerge(base, overlay) {
+    var child = Object.create(base);
+    if (overlay) for (var k in overlay) if (overlay.hasOwnProperty(k)) child[k] = overlay[k];
+    return child;
+  }
 
   function dictSet(d, k, v) { d[k] = v; return v; }
   function dictGet(d, k) { var v = d[k]; return v !== undefined ? v : NIL; }
@@ -515,6 +519,52 @@
     return NIL;
   }
 
+  // =========================================================================
+  // Performance overrides — evaluator hot path
+  // =========================================================================
+
+  // Override parseKeywordArgs: imperative loop instead of reduce+assoc
+  parseKeywordArgs = function(rawArgs, env) {
+    var kwargs = {};
+    var children = [];
+    for (var i = 0; i < rawArgs.length; i++) {
+      var arg = rawArgs[i];
+      if (arg && arg._kw && (i + 1) < rawArgs.length) {
+        kwargs[arg.name] = trampoline(evalExpr(rawArgs[i + 1], env));
+        i++;
+      } else {
+        children.push(trampoline(evalExpr(arg, env)));
+      }
+    }
+    return [kwargs, children];
+  };
+
+  // Override callComponent: use prototype chain env, imperative kwarg binding
+  callComponent = function(comp, rawArgs, env) {
+    var kwargs = {};
+    var children = [];
+    for (var i = 0; i < rawArgs.length; i++) {
+      var arg = rawArgs[i];
+      if (arg && arg._kw && (i + 1) < rawArgs.length) {
+        kwargs[arg.name] = trampoline(evalExpr(rawArgs[i + 1], env));
+        i++;
+      } else {
+        children.push(trampoline(evalExpr(arg, env)));
+      }
+    }
+    var local = Object.create(componentClosure(comp));
+    for (var k in env) if (env.hasOwnProperty(k)) local[k] = env[k];
+    var params = componentParams(comp);
+    for (var j = 0; j < params.length; j++) {
+      var p = params[j];
+      local[p] = p in kwargs ? kwargs[p] : NIL;
+    }
+    if (componentHasChildren(comp)) {
+      local["children"] = children;
+    }
+    return makeThunk(componentBody(comp), local);
+  };
+
   // =========================================================================
   // Platform: deps module — component dependency analysis
   // =========================================================================
@@ -2849,6 +2899,84 @@ callExpr.push(dictGet(kwargs, k)); } }
 
   function domTagName(el) { return el && el.tagName ? el.tagName : ""; }
 
+  // =========================================================================
+  // Performance overrides — replace transpiled spec with imperative JS
+  // =========================================================================
+
+  // Override renderDomComponent: imperative kwarg parsing, no reduce/assoc
+  renderDomComponent = function(comp, args, env, ns) {
+    // Parse keyword args imperatively
+    var kwargs = {};
+    var children = [];
+    for (var i = 0; i < args.length; i++) {
+      var arg = args[i];
+      if (arg && arg._kw && (i + 1) < args.length) {
+        kwargs[arg.name] = trampoline(evalExpr(args[i + 1], env));
+        i++; // skip value
+      } else {
+        children.push(arg);
+      }
+    }
+    // Build local env via prototype chain
+    var local = Object.create(componentClosure(comp));
+    // Copy caller env own properties
+    for (var k in env) if (env.hasOwnProperty(k)) local[k] = env[k];
+    // Bind params
+    var params = componentParams(comp);
+    for (var j = 0; j < params.length; j++) {
+      var p = params[j];
+      local[p] = p in kwargs ? kwargs[p] : NIL;
+    }
+    // Bind children
+    if (componentHasChildren(comp)) {
+      var childFrag = document.createDocumentFragment();
+      for (var c = 0; c < children.length; c++) {
+        var rendered = renderToDom(children[c], env, ns);
+        if (rendered) childFrag.appendChild(rendered);
+      }
+      local["children"] = childFrag;
+    }
+    return renderToDom(componentBody(comp), local, ns);
+  };
+
+  // Override renderDomElement: imperative attr parsing, no reduce/assoc
+  renderDomElement = function(tag, args, env, ns) {
+    var newNs = tag === "svg" ? SVG_NS : tag === "math" ? MATH_NS : ns;
+    var el = domCreateElement(tag, newNs);
+    var extraClasses = [];
+    var isVoid = contains(VOID_ELEMENTS, tag);
+    for (var i = 0; i < args.length; i++) {
+      var arg = args[i];
+      if (arg && arg._kw && (i + 1) < args.length) {
+        var attrName = arg.name;
+        var attrVal = trampoline(evalExpr(args[i + 1], env));
+        i++; // skip value
+        if (isNil(attrVal) || attrVal === false) continue;
+        if (attrName === "class" && attrVal && attrVal._styleValue) {
+          extraClasses.push(attrVal.className);
+        } else if (attrName === "style" && attrVal && attrVal._styleValue) {
+          extraClasses.push(attrVal.className);
+        } else if (contains(BOOLEAN_ATTRS, attrName)) {
+          if (isSxTruthy(attrVal)) el.setAttribute(attrName, "");
+        } else if (attrVal === true) {
+          el.setAttribute(attrName, "");
+        } else {
+          el.setAttribute(attrName, String(attrVal));
+        }
+      } else {
+        if (!isVoid) {
+          var child = renderToDom(arg, env, newNs);
+          if (child) el.appendChild(child);
+        }
+      }
+    }
+    if (extraClasses.length) {
+      var existing = el.getAttribute("class") || "";
+      el.setAttribute("class", (existing ? existing + " " : "") + extraClasses.join(" "));
+    }
+    return el;
+  };
+
 
   // =========================================================================
   // Platform interface — Engine pure logic (browser + node compatible)

shared/sx/ref/bootstrap_js.py

@@ -1710,8 +1710,12 @@ PLATFORM_JS_PRE = '''
   function envHas(env, name) { return name in env; }
   function envGet(env, name) { return env[name]; }
   function envSet(env, name, val) { env[name] = val; }
-  function envExtend(env) { return merge(env); }
+  function envExtend(env) { return Object.create(env); }
-  function envMerge(base, overlay) { return merge(base, overlay); }
+  function envMerge(base, overlay) {
+    var child = Object.create(base);
+    if (overlay) for (var k in overlay) if (overlay.hasOwnProperty(k)) child[k] = overlay[k];
+    return child;
+  }
 
   function dictSet(d, k, v) { d[k] = v; return v; }
   function dictGet(d, k) { var v = d[k]; return v !== undefined ? v : NIL; }
@@ -1852,7 +1856,53 @@ PLATFORM_JS_POST = '''
   function forEachIndexed(fn, coll) {
     for (var i = 0; i < coll.length; i++) fn(i, coll[i]);
     return NIL;
-  }'''
+  }
+
+  // =========================================================================
+  // Performance overrides — evaluator hot path
+  // =========================================================================
+
+  // Override parseKeywordArgs: imperative loop instead of reduce+assoc
+  parseKeywordArgs = function(rawArgs, env) {
+    var kwargs = {};
+    var children = [];
+    for (var i = 0; i < rawArgs.length; i++) {
+      var arg = rawArgs[i];
+      if (arg && arg._kw && (i + 1) < rawArgs.length) {
+        kwargs[arg.name] = trampoline(evalExpr(rawArgs[i + 1], env));
+        i++;
+      } else {
+        children.push(trampoline(evalExpr(arg, env)));
+      }
+    }
+    return [kwargs, children];
+  };
+
+  // Override callComponent: use prototype chain env, imperative kwarg binding
+  callComponent = function(comp, rawArgs, env) {
+    var kwargs = {};
+    var children = [];
+    for (var i = 0; i < rawArgs.length; i++) {
+      var arg = rawArgs[i];
+      if (arg && arg._kw && (i + 1) < rawArgs.length) {
+        kwargs[arg.name] = trampoline(evalExpr(rawArgs[i + 1], env));
+        i++;
+      } else {
+        children.push(trampoline(evalExpr(arg, env)));
+      }
+    }
+    var local = Object.create(componentClosure(comp));
+    for (var k in env) if (env.hasOwnProperty(k)) local[k] = env[k];
+    var params = componentParams(comp);
+    for (var j = 0; j < params.length; j++) {
+      var p = params[j];
+      local[p] = p in kwargs ? kwargs[p] : NIL;
+    }
+    if (componentHasChildren(comp)) {
+      local["children"] = children;
+    }
+    return makeThunk(componentBody(comp), local);
+  };'''
 
 PLATFORM_DEPS_JS = '''
   // =========================================================================
@@ -2117,6 +2167,84 @@ PLATFORM_DOM_JS = """
   }
 
   function domTagName(el) { return el && el.tagName ? el.tagName : ""; }
+
+  // =========================================================================
+  // Performance overrides — replace transpiled spec with imperative JS
+  // =========================================================================
+
+  // Override renderDomComponent: imperative kwarg parsing, no reduce/assoc
+  renderDomComponent = function(comp, args, env, ns) {
+    // Parse keyword args imperatively
+    var kwargs = {};
+    var children = [];
+    for (var i = 0; i < args.length; i++) {
+      var arg = args[i];
+      if (arg && arg._kw && (i + 1) < args.length) {
+        kwargs[arg.name] = trampoline(evalExpr(args[i + 1], env));
+        i++; // skip value
+      } else {
+        children.push(arg);
+      }
+    }
+    // Build local env via prototype chain
+    var local = Object.create(componentClosure(comp));
+    // Copy caller env own properties
+    for (var k in env) if (env.hasOwnProperty(k)) local[k] = env[k];
+    // Bind params
+    var params = componentParams(comp);
+    for (var j = 0; j < params.length; j++) {
+      var p = params[j];
+      local[p] = p in kwargs ? kwargs[p] : NIL;
+    }
+    // Bind children
+    if (componentHasChildren(comp)) {
+      var childFrag = document.createDocumentFragment();
+      for (var c = 0; c < children.length; c++) {
+        var rendered = renderToDom(children[c], env, ns);
+        if (rendered) childFrag.appendChild(rendered);
+      }
+      local["children"] = childFrag;
+    }
+    return renderToDom(componentBody(comp), local, ns);
+  };
+
+  // Override renderDomElement: imperative attr parsing, no reduce/assoc
+  renderDomElement = function(tag, args, env, ns) {
+    var newNs = tag === "svg" ? SVG_NS : tag === "math" ? MATH_NS : ns;
+    var el = domCreateElement(tag, newNs);
+    var extraClasses = [];
+    var isVoid = contains(VOID_ELEMENTS, tag);
+    for (var i = 0; i < args.length; i++) {
+      var arg = args[i];
+      if (arg && arg._kw && (i + 1) < args.length) {
+        var attrName = arg.name;
+        var attrVal = trampoline(evalExpr(args[i + 1], env));
+        i++; // skip value
+        if (isNil(attrVal) || attrVal === false) continue;
+        if (attrName === "class" && attrVal && attrVal._styleValue) {
+          extraClasses.push(attrVal.className);
+        } else if (attrName === "style" && attrVal && attrVal._styleValue) {
+          extraClasses.push(attrVal.className);
+        } else if (contains(BOOLEAN_ATTRS, attrName)) {
+          if (isSxTruthy(attrVal)) el.setAttribute(attrName, "");
+        } else if (attrVal === true) {
+          el.setAttribute(attrName, "");
+        } else {
+          el.setAttribute(attrName, String(attrVal));
+        }
+      } else {
+        if (!isVoid) {
+          var child = renderToDom(arg, env, newNs);
+          if (child) el.appendChild(child);
+        }
+      }
+    }
+    if (extraClasses.length) {
+      var existing = el.getAttribute("class") || "";
+      el.setAttribute("class", (existing ? existing + " " : "") + extraClasses.join(" "));
+    }
+    return el;
+  };
 """
 
 PLATFORM_ENGINE_PURE_JS = """