Fix process-bindings scope loss and async-invoke arity, bootstrap async adapter

Two bugs fixed:
1. process-bindings used merge(env) which returns {} for Env objects
   (Env is not a dict subclass). Changed to env-extend in render.sx
   and adapter-async.sx. This caused "Undefined symbol: theme" etc.
2. async-aser-eval-call passed evaled-args list to async-invoke(&rest),
   double-wrapping it. Changed to inline apply + coroutine check.

Also: bootstrap define-async into sx_ref.py (Phase 6), replace ~1000 LOC
hand-written async_eval_ref.py with 24-line thin re-export shim.

Test runner now uses Env (not flat dict) for render envs to catch scope bugs.
8 new regression tests (4 scope chain, 2 native callable arity, 2 render).

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 = "2026-03-11T14:54:55Z";
+  var SX_VERSION = "2026-03-11T16:35:21Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
@@ -204,7 +204,7 @@
 
   // JSON / dict helpers for island state serialization
   function jsonSerialize(obj) {
-    try { return JSON.stringify(obj); } catch(e) { return "{}"; }
+    return JSON.stringify(obj);
   }
   function isEmptyDict(d) {
     if (!d || typeof d !== "object") return true;
@@ -214,11 +214,34 @@
 
   function envHas(env, name) { return name in env; }
   function envGet(env, name) { return env[name]; }
-  function envSet(env, name, val) { env[name] = val; }
+  function envSet(env, name, val) {
+    // Walk prototype chain to find where the variable is defined (for set!)
+    var obj = env;
+    while (obj !== null && obj !== Object.prototype) {
+      if (obj.hasOwnProperty(name)) { obj[name] = val; return; }
+      obj = Object.getPrototypeOf(obj);
+    }
+    // Not found in any parent scope — set on the immediate env
+    env[name] = val;
+  }
   function envExtend(env) { return Object.create(env); }
   function envMerge(base, overlay) {
+    // Same env or overlay is descendant of base — just extend, no copy.
+    // This prevents set! inside lambdas from modifying shadow copies.
+    if (base === overlay) return Object.create(base);
+    var p = overlay;
+    for (var d = 0; p && p !== Object.prototype && d < 100; d++) {
+      if (p === base) return Object.create(base);
+      p = Object.getPrototypeOf(p);
+    }
+    // General case: extend base, copy ONLY overlay properties that don't
+    // exist in the base chain (avoids shadowing closure bindings).
     var child = Object.create(base);
-    if (overlay) for (var k in overlay) if (overlay.hasOwnProperty(k)) child[k] = overlay[k];
+    if (overlay) {
+      for (var k in overlay) {
+        if (overlay.hasOwnProperty(k) && !(k in base)) child[k] = overlay[k];
+      }
+    }
     return child;
   }
 
@@ -732,9 +755,9 @@
   var kwargs = first(parsed);
   var children = nth(parsed, 1);
   var local = envMerge(componentClosure(comp), env);
-  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; local[p] = sxOr(dictGet(kwargs, p), NIL); } }
+  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; envSet(local, p, sxOr(dictGet(kwargs, p), NIL)); } }
   if (isSxTruthy(componentHasChildren(comp))) {
-  local["children"] = children;
+  envSet(local, "children", children);
 }
   return makeThunk(componentBody(comp), local);
 })(); };
@@ -841,7 +864,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   var loopBody = (isSxTruthy((len(body) == 1)) ? first(body) : cons(makeSymbol("begin"), body));
   var loopFn = makeLambda(params, loopBody, env);
   loopFn.name = loopName;
-  lambdaClosure(loopFn)[loopName] = loopFn;
+  envSet(lambdaClosure(loopFn), loopName, loopFn);
   return (function() {
   var initVals = map(function(e) { return trampoline(evalExpr(e, env)); }, inits);
   return callLambda(loopFn, initVals, env);
@@ -865,7 +888,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   if (isSxTruthy((isSxTruthy(isLambda(value)) && isNil(lambdaName(value))))) {
   value.name = symbolName(nameSym);
 }
-  env[symbolName(nameSym)] = value;
+  envSet(env, symbolName(nameSym), value);
   return value;
 })(); };
 
@@ -881,7 +904,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   var affinity = defcompKwarg(args, "affinity", "auto");
   return (function() {
   var comp = makeComponent(compName, params, hasChildren, body, env, affinity);
-  env[symbolName(nameSym)] = comp;
+  envSet(env, symbolName(nameSym), comp);
   return comp;
 })();
 })(); };
@@ -924,7 +947,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   var hasChildren = nth(parsed, 1);
   return (function() {
   var island = makeIsland(compName, params, hasChildren, body, env);
-  env[symbolName(nameSym)] = island;
+  envSet(env, symbolName(nameSym), island);
   return island;
 })();
 })(); };
@@ -939,7 +962,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   var restParam = nth(parsed, 1);
   return (function() {
   var mac = makeMacro(params, restParam, body, env, symbolName(nameSym));
-  env[symbolName(nameSym)] = mac;
+  envSet(env, symbolName(nameSym), mac);
   return mac;
 })();
 })(); };
@@ -956,7 +979,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   var sfDefstyle = function(args, env) { return (function() {
   var nameSym = first(args);
   var value = trampoline(evalExpr(nth(args, 1), env));
-  env[symbolName(nameSym)] = value;
+  envSet(env, symbolName(nameSym), value);
   return value;
 })(); };
 
@@ -996,7 +1019,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   var sfSetBang = function(args, env) { return (function() {
   var name = symbolName(first(args));
   var value = trampoline(evalExpr(nth(args, 1), env));
-  env[name] = value;
+  envSet(env, name, value);
   return value;
 })(); };
 
@@ -1021,7 +1044,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
 })(); }, NIL, range(0, (len(bindings) / 2))));
   (function() {
   var values = map(function(e) { return trampoline(evalExpr(e, local)); }, valExprs);
-  { var _c = zip(names, values); for (var _i = 0; _i < _c.length; _i++) { var pair = _c[_i]; local[first(pair)] = nth(pair, 1); } }
+  { var _c = zip(names, values); for (var _i = 0; _i < _c.length; _i++) { var pair = _c[_i]; envSet(local, first(pair), nth(pair, 1)); } }
   return forEach(function(val) { return (isSxTruthy(isLambda(val)) ? forEach(function(n) { return envSet(lambdaClosure(val), n, envGet(local, n)); }, names) : NIL); }, values);
 })();
   { var _c = slice(body, 0, (len(body) - 1)); for (var _i = 0; _i < _c.length; _i++) { var e = _c[_i]; trampoline(evalExpr(e, local)); } }
@@ -1046,9 +1069,9 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
   // expand-macro
   var expandMacro = function(mac, rawArgs, env) { return (function() {
   var local = envMerge(macroClosure(mac), env);
-  { var _c = mapIndexed(function(i, p) { return [p, i]; }, macroParams(mac)); for (var _i = 0; _i < _c.length; _i++) { var pair = _c[_i]; local[first(pair)] = (isSxTruthy((nth(pair, 1) < len(rawArgs))) ? nth(rawArgs, nth(pair, 1)) : NIL); } }
+  { var _c = mapIndexed(function(i, p) { return [p, i]; }, macroParams(mac)); for (var _i = 0; _i < _c.length; _i++) { var pair = _c[_i]; envSet(local, first(pair), (isSxTruthy((nth(pair, 1) < len(rawArgs))) ? nth(rawArgs, nth(pair, 1)) : NIL)); } }
   if (isSxTruthy(macroRestParam(mac))) {
-  local[macroRestParam(mac)] = slice(rawArgs, len(macroParams(mac)));
+  envSet(local, macroRestParam(mac), slice(rawArgs, len(macroParams(mac))));
 }
   return trampoline(evalExpr(macroBody(mac), local));
 })(); };
@@ -1162,7 +1185,7 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
 
   // process-bindings
   var processBindings = function(bindings, env) { return (function() {
-  var local = merge(env);
+  var local = envExtend(env);
   { var _c = bindings; for (var _i = 0; _i < _c.length; _i++) { var pair = _c[_i]; if (isSxTruthy((isSxTruthy((typeOf(pair) == "list")) && (len(pair) >= 2)))) {
   (function() {
   var name = (isSxTruthy((typeOf(first(pair)) == "symbol")) ? symbolName(first(pair)) : (String(first(pair))));
@@ -1392,9 +1415,9 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return ""; if (_m =
 })(); }, {["i"]: 0, ["skip"]: false}, args);
   return (function() {
   var local = envMerge(componentClosure(comp), env);
-  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; local[p] = (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL); } }
+  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; envSet(local, p, (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL)); } }
   if (isSxTruthy(componentHasChildren(comp))) {
-  local["children"] = makeRawHtml(join("", map(function(c) { return renderToHtml(c, env); }, children)));
+  envSet(local, "children", makeRawHtml(join("", map(function(c) { return renderToHtml(c, env); }, children))));
 }
   return renderToHtml(componentBody(comp), local);
 })();
@@ -1458,20 +1481,20 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return ""; if (_m =
   return (function() {
   var local = envMerge(componentClosure(island), env);
   var islandName = componentName(island);
-  { var _c = componentParams(island); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; local[p] = (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL); } }
+  { var _c = componentParams(island); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; envSet(local, p, (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL)); } }
   if (isSxTruthy(componentHasChildren(island))) {
-  local["children"] = makeRawHtml(join("", map(function(c) { return renderToHtml(c, env); }, children)));
+  envSet(local, "children", makeRawHtml(join("", map(function(c) { return renderToHtml(c, env); }, children))));
 }
   return (function() {
   var bodyHtml = renderToHtml(componentBody(island), local);
-  var stateJson = serializeIslandState(kwargs);
+  var stateSx = serializeIslandState(kwargs);
-  return (String("<span data-sx-island=\"") + String(escapeAttr(islandName)) + String("\"") + String((isSxTruthy(stateJson) ? (String(" data-sx-state=\"") + String(escapeAttr(stateJson)) + String("\"")) : "")) + String(">") + String(bodyHtml) + String("</span>"));
+  return (String("<span data-sx-island=\"") + String(escapeAttr(islandName)) + String("\"") + String((isSxTruthy(stateSx) ? (String(" data-sx-state=\"") + String(escapeAttr(stateSx)) + String("\"")) : "")) + String(">") + String(bodyHtml) + String("</span>"));
 })();
 })();
 })(); };
 
   // serialize-island-state
-  var serializeIslandState = function(kwargs) { return (isSxTruthy(isEmptyDict(kwargs)) ? NIL : jsonSerialize(kwargs)); };
+  var serializeIslandState = function(kwargs) { return (isSxTruthy(isEmptyDict(kwargs)) ? NIL : sxSerialize(kwargs)); };
 
 
   // === Transpiled from adapter-sx ===
@@ -1586,7 +1609,7 @@ return result; }, args);
   var coll = trampoline(evalExpr(nth(args, 1), env));
   return map(function(item) { return (isSxTruthy(isLambda(f)) ? (function() {
   var local = envMerge(lambdaClosure(f), env);
-  local[first(lambdaParams(f))] = item;
+  envSet(local, first(lambdaParams(f)), item);
   return aser(lambdaBody(f), local);
 })() : invoke(f, item)); }, coll);
 })() : (isSxTruthy((name == "map-indexed")) ? (function() {
@@ -1594,8 +1617,8 @@ return result; }, args);
   var coll = trampoline(evalExpr(nth(args, 1), env));
   return mapIndexed(function(i, item) { return (isSxTruthy(isLambda(f)) ? (function() {
   var local = envMerge(lambdaClosure(f), env);
-  local[first(lambdaParams(f))] = i;
+  envSet(local, first(lambdaParams(f)), i);
-  local[nth(lambdaParams(f), 1)] = item;
+  envSet(local, nth(lambdaParams(f), 1), item);
   return aser(lambdaBody(f), local);
 })() : invoke(f, i, item)); }, coll);
 })() : (isSxTruthy((name == "for-each")) ? (function() {
@@ -1604,7 +1627,7 @@ return result; }, args);
   var results = [];
   { var _c = coll; for (var _i = 0; _i < _c.length; _i++) { var item = _c[_i]; (isSxTruthy(isLambda(f)) ? (function() {
   var local = envMerge(lambdaClosure(f), env);
-  local[first(lambdaParams(f))] = item;
+  envSet(local, first(lambdaParams(f)), item);
   return append_b(results, aser(lambdaBody(f), local));
 })() : invoke(f, item)); } }
   return (isSxTruthy(isEmpty(results)) ? NIL : results);
@@ -1662,7 +1685,7 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return createFragme
   var attrExpr = nth(args, (get(state, "i") + 1));
   (isSxTruthy(startsWith(attrName, "on-")) ? (function() {
   var attrVal = trampoline(evalExpr(attrExpr, env));
-  return (isSxTruthy(isCallable(attrVal)) ? domListen(el, slice(attrName, 3), (isSxTruthy((isSxTruthy(isLambda(attrVal)) && (len(lambdaParams(attrVal)) == 0))) ? function(e) { return callLambda(attrVal, [], lambdaClosure(attrVal)); } : attrVal)) : NIL);
+  return (isSxTruthy(isCallable(attrVal)) ? domListen(el, slice(attrName, 3), attrVal) : NIL);
 })() : (isSxTruthy((attrName == "bind")) ? (function() {
   var attrVal = trampoline(evalExpr(attrExpr, env));
   return (isSxTruthy(isSignal(attrVal)) ? bindInput(el, attrVal) : NIL);
@@ -1696,7 +1719,7 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return createFragme
 })(); }, {["i"]: 0, ["skip"]: false}, args);
   return (function() {
   var local = envMerge(componentClosure(comp), env);
-  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; local[p] = (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL); } }
+  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; envSet(local, p, (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL)); } }
   if (isSxTruthy(componentHasChildren(comp))) {
   (function() {
   var childFrag = createFragment();
@@ -1887,7 +1910,7 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return createFragme
   return (function() {
   var local = envMerge(componentClosure(island), env);
   var islandName = componentName(island);
-  { var _c = componentParams(island); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; local[p] = (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL); } }
+  { var _c = componentParams(island); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; envSet(local, p, (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL)); } }
   if (isSxTruthy(componentHasChildren(island))) {
   (function() {
   var childFrag = createFragment();
@@ -3002,9 +3025,9 @@ return postSwap(target); }))) : NIL);
   var exprs = sxParse(body);
   return domListen(el, eventName, function(e) { return (function() {
   var handlerEnv = envExtend({});
-  handlerEnv["event"] = e;
+  envSet(handlerEnv, "event", e);
-  handlerEnv["this"] = el;
+  envSet(handlerEnv, "this", el);
-  handlerEnv["detail"] = eventDetail(e);
+  envSet(handlerEnv, "detail", eventDetail(e));
   return forEach(function(expr) { return evalExpr(expr, handlerEnv); }, exprs);
 })(); });
 })()) : NIL);
@@ -3233,17 +3256,17 @@ callExpr.push(dictGet(kwargs, k)); } }
   // hydrate-island
   var hydrateIsland = function(el) { return (function() {
   var name = domGetAttr(el, "data-sx-island");
-  var stateJson = sxOr(domGetAttr(el, "data-sx-state"), "{}");
+  var stateSx = sxOr(domGetAttr(el, "data-sx-state"), "{}");
   return (function() {
   var compName = (String("~") + String(name));
   var env = getRenderEnv(NIL);
   return (function() {
   var comp = envGet(env, compName);
   return (isSxTruthy(!isSxTruthy(sxOr(isComponent(comp), isIsland(comp)))) ? logWarn((String("hydrate-island: unknown island ") + String(compName))) : (function() {
-  var kwargs = jsonParse(stateJson);
+  var kwargs = sxOr(first(sxParse(stateSx)), {});
   var disposers = [];
   var local = envMerge(componentClosure(comp), env);
-  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; local[p] = (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL); } }
+  { var _c = componentParams(comp); for (var _i = 0; _i < _c.length; _i++) { var p = _c[_i]; envSet(local, p, (isSxTruthy(dictHas(kwargs, p)) ? dictGet(kwargs, p) : NIL)); } }
   return (function() {
   var bodyDom = withIslandScope(function(disposable) { return append_b(disposers, disposable); }, function() { return renderToDom(componentBody(comp), local, NIL); });
   domSetTextContent(el, "");
@@ -3976,8 +3999,11 @@ return (isSxTruthy((_batchDepth == 0)) ? (function() {
   function domListen(el, name, handler) {
     if (!_hasDom || !el) return function() {};
     // Wrap SX lambdas from runtime-evaluated island code into native fns
+    // If lambda takes 0 params, call without event arg (convenience for on-click handlers)
     var wrapped = isLambda(handler)
-      ? function(e) { try { invoke(handler, e); } catch(err) { console.error("[sx-ref] domListen handler error:", name, err); } }
+      ? (lambdaParams(handler).length === 0
+        ? function(e) { try { invoke(handler); } catch(err) { console.error("[sx-ref] domListen handler error:", name, err); } }
+        : function(e) { try { invoke(handler, e); } catch(err) { console.error("[sx-ref] domListen handler error:", name, err); } })
       : handler;
     if (name === "click") logInfo("domListen: click on <" + (el.tagName||"?").toLowerCase() + "> text=" + (el.textContent||"").substring(0,20) + " isLambda=" + isLambda(handler));
     el.addEventListener(name, wrapped);

shared/sx/html.py

@@ -414,10 +414,10 @@ def _render_component(comp: Component, args: list, env: dict[str, Any]) -> str:
 def _render_island(island: Island, args: list, env: dict[str, Any]) -> str:
     """Render an island as static HTML with hydration attributes.
 
-    Produces: <span data-sx-island="name" data-sx-state='{"k":"v",...}'>body HTML</span>
+    Produces: <span data-sx-island="name" data-sx-state="{:k &quot;v&quot;}">body HTML</span>
-    The client hydrates this into a reactive island.
+    The client hydrates this into a reactive island via sx-parse (not JSON).
     """
-    import json as _json
+    from .parser import serialize as _sx_serialize
 
     kwargs: dict[str, Any] = {}
     children: list[Any] = []
@@ -443,26 +443,13 @@ def _render_island(island: Island, args: list, env: dict[str, Any]) -> str:
 
     body_html = _render(island.body, local)
 
-    # Serialize state for hydration — only keyword args
+    # Serialize state for hydration — SX format (not JSON)
-    state = {}
+    state_sx = _escape_attr(_sx_serialize(kwargs)) if kwargs else ""
-    for k, v in kwargs.items():
-        if isinstance(v, (str, int, float, bool)):
-            state[k] = v
-        elif v is NIL or v is None:
-            state[k] = None
-        elif isinstance(v, list):
-            state[k] = v
-        elif isinstance(v, dict):
-            state[k] = v
-        else:
-            state[k] = str(v)
-
-    state_json = _escape_attr(_json.dumps(state, separators=(",", ":"))) if state else ""
     island_name = _escape_attr(island.name)
 
     parts = [f'<span data-sx-island="{island_name}"']
-    if state_json:
+    if state_sx:
-        parts.append(f' data-sx-state="{state_json}"')
+        parts.append(f' data-sx-state="{state_sx}"')
     parts.append(">")
     parts.append(body_html)
     parts.append("</span>")

shared/sx/ref/adapter-async.sx

@@ -450,7 +450,9 @@
 
 (define-async async-process-bindings
   (fn (bindings env ctx)
-    (let ((local (merge env)))
+    ;; env-extend (not merge) — Env is not a dict subclass, so merge()
+    ;; returns an empty dict, losing all parent scope bindings.
+    (let ((local (env-extend env)))
       (if (and (= (type-of bindings) "list") (not (empty? bindings)))
         (if (= (type-of (first bindings)) "list")
           ;; Scheme-style: ((name val) ...)
@@ -669,7 +671,10 @@
           (evaled-args (async-eval-args args env ctx)))
       (cond
         (and (callable? f) (not (lambda? f)) (not (component? f)))
-          (async-invoke f evaled-args)
+          ;; apply directly — async-invoke takes &rest so passing a list
+          ;; would wrap it in another list
+          (let ((r (apply f evaled-args)))
+            (if (async-coroutine? r) (async-await! r) r))
         (lambda? f)
           (let ((local (env-merge (lambda-closure f) env)))
             (for-each-indexed
@@ -1166,19 +1171,20 @@
 
 (define-async async-eval-slot-inner
   (fn (expr env ctx)
-    (let ((result
+    ;; NOTE: Uses statement-form let + set! to avoid expression-context
-            (if (and (list? expr) (not (empty? expr)))
+    ;; let (IIFE lambdas) which can't contain await in Python.
-              (let ((head (first expr)))
+    (let ((result nil))
-                (if (and (= (type-of head) "symbol")
+      (if (and (list? expr) (not (empty? expr)))
-                         (starts-with? (symbol-name head) "~"))
+        (let ((head (first expr)))
-                  (let ((name (symbol-name head))
+          (if (and (= (type-of head) "symbol")
-                        (val (if (env-has? env name) (env-get env name) nil)))
+                   (starts-with? (symbol-name head) "~"))
-                    (if (component? val)
+            (let ((name (symbol-name head))
-                      (async-aser-component val (rest expr) env ctx)
+                  (val (if (env-has? env name) (env-get env name) nil)))
-                      ;; Islands and unknown components — fall through to aser
+              (if (component? val)
-                      (async-maybe-expand-result (async-aser expr env ctx) env ctx)))
+                (set! result (async-aser-component val (rest expr) env ctx))
-                  (async-maybe-expand-result (async-aser expr env ctx) env ctx)))
+                (set! result (async-maybe-expand-result (async-aser expr env ctx) env ctx))))
-              (async-maybe-expand-result (async-aser expr env ctx) env ctx))))
+            (set! result (async-maybe-expand-result (async-aser expr env ctx) env ctx))))
+        (set! result (async-maybe-expand-result (async-aser expr env ctx) env ctx)))
       ;; Normalize result to SxExpr
       (if (sx-expr? result)
         result

shared/sx/ref/adapter-dom.sx

@@ -186,15 +186,10 @@
                       (attr-expr (nth args (inc (get state "i")))))
                   (cond
                     ;; Event handler: evaluate eagerly, bind listener
-                    ;; If handler is a 0-arity lambda, wrap to ignore the event arg
                     (starts-with? attr-name "on-")
                       (let ((attr-val (trampoline (eval-expr attr-expr env))))
                         (when (callable? attr-val)
-                          (dom-listen el (slice attr-name 3)
+                          (dom-listen el (slice attr-name 3) attr-val)))
-                            (if (and (lambda? attr-val)
-                                     (= (len (lambda-params attr-val)) 0))
-                              (fn (e) (call-lambda attr-val (list) (lambda-closure attr-val)))
-                              attr-val))))
                     ;; Two-way input binding: :bind signal
                     (= attr-name "bind")
                       (let ((attr-val (trampoline (eval-expr attr-expr env))))

shared/sx/ref/adapter-html.sx

@@ -433,11 +433,11 @@
 
         ;; Render the island body as HTML
         (let ((body-html (render-to-html (component-body island) local))
-              (state-json (serialize-island-state kwargs)))
+              (state-sx (serialize-island-state kwargs)))
           ;; Wrap in container with hydration attributes
           (str "<span data-sx-island=\"" (escape-attr island-name) "\""
-               (if state-json
+               (if state-sx
-                 (str " data-sx-state=\"" (escape-attr state-json) "\"")
+                 (str " data-sx-state=\"" (escape-attr state-sx) "\"")
                  "")
                ">"
                body-html
@@ -445,17 +445,17 @@
 
 
 ;; --------------------------------------------------------------------------
-;; serialize-island-state — serialize kwargs to JSON for hydration
+;; serialize-island-state — serialize kwargs to SX for hydration
 ;; --------------------------------------------------------------------------
 ;;
-;; Only serializes simple values (numbers, strings, booleans, nil, lists, dicts).
+;; Uses the SX serializer (not JSON) so the client can parse with sx-parse.
-;; Functions, components, and other non-serializable values are skipped.
+;; Handles all SX types natively: numbers, strings, booleans, nil, lists, dicts.
 
 (define serialize-island-state
   (fn (kwargs)
     (if (empty-dict? kwargs)
       nil
-      (json-serialize kwargs))))
+      (sx-serialize kwargs))))
 
 
 ;; --------------------------------------------------------------------------
@@ -476,8 +476,8 @@
 ;; Raw HTML construction:
 ;;   (make-raw-html s)          → wrap string as raw HTML (not double-escaped)
 ;;
-;; JSON serialization (for island state):
+;; Island state serialization:
-;;   (json-serialize dict)      → JSON string
+;;   (sx-serialize val)         → SX source string (from parser.sx)
 ;;   (empty-dict? d)            → boolean
 ;;   (escape-attr s)            → HTML attribute escape
 ;;

shared/sx/ref/boot.sx

@@ -344,15 +344,15 @@
 (define hydrate-island
   (fn (el)
     (let ((name (dom-get-attr el "data-sx-island"))
-          (state-json (or (dom-get-attr el "data-sx-state") "{}")))
+          (state-sx (or (dom-get-attr el "data-sx-state") "{}")))
       (let ((comp-name (str "~" name))
             (env (get-render-env nil)))
         (let ((comp (env-get env comp-name)))
           (if (not (or (component? comp) (island? comp)))
             (log-warn (str "hydrate-island: unknown island " comp-name))
 
-            ;; Parse state and build keyword args
+            ;; Parse state and build keyword args — SX format, not JSON
-            (let ((kwargs (json-parse state-json))
+            (let ((kwargs (or (first (sx-parse state-sx)) {}))
                   (disposers (list))
                   (local (env-merge (component-closure comp) env)))
 
@@ -494,8 +494,8 @@
 ;;   (log-info msg)                → void (console.log with prefix)
 ;;   (log-parse-error label text err) → void (diagnostic parse error)
 ;;
-;; === JSON ===
+;; === Parsing (island state) ===
-;;   (json-parse str)              → dict/list/value (JSON.parse)
+;;   (sx-parse str)                → list of AST expressions (from parser.sx)
 ;;
 ;; === Processing markers ===
 ;;   (mark-processed! el key)      → void

shared/sx/ref/bootstrap_py.py

@@ -49,6 +49,8 @@ class PyEmitter:
 
     def __init__(self):
         self.indent = 0
+        self._async_names: set[str] = set()  # SX names of define-async functions
+        self._in_async: bool = False          # Currently emitting async def body?
 
     def emit(self, expr) -> str:
         """Emit a Python expression from an SX AST node."""
@@ -80,6 +82,8 @@ class PyEmitter:
                 name = head.name
                 if name == "define":
                     return self._emit_define(expr, indent)
+                if name == "define-async":
+                    return self._emit_define_async(expr, indent)
                 if name == "set!":
                     return f"{pad}{self._mangle(expr[1].name)} = {self.emit(expr[2])}"
                 if name == "when":
@@ -275,6 +279,19 @@ class PyEmitter:
             "sf-defisland": "sf_defisland",
             # adapter-sx.sx
             "render-to-sx": "render_to_sx",
+            # adapter-async.sx platform primitives
+            "svg-context-set!": "svg_context_set",
+            "svg-context-reset!": "svg_context_reset",
+            "css-class-collect!": "css_class_collect",
+            "is-raw-html?": "is_raw_html",
+            "async-coroutine?": "is_async_coroutine",
+            "async-await!": "async_await",
+            "is-sx-expr?": "is_sx_expr",
+            "sx-expr?": "is_sx_expr",
+            "io-primitive?": "io_primitive_p",
+            "expand-components?": "expand_components_p",
+            "svg-context?": "svg_context_p",
+            "make-sx-expr": "make_sx_expr",
             "aser": "aser",
             "eval-case-aser": "eval_case_aser",
             "sx-serialize": "sx_serialize",
@@ -417,6 +434,8 @@ class PyEmitter:
         # Regular function call
         fn_name = self._mangle(name)
         args = ", ".join(self.emit(x) for x in expr[1:])
+        if self._in_async and name in self._async_names:
+            return f"(await {fn_name}({args}))"
         return f"{fn_name}({args})"
 
     # --- Special form emitters ---
@@ -513,7 +532,7 @@ class PyEmitter:
         body_parts = expr[2:]
         lines = [f"{pad}if sx_truthy({cond}):"]
         for b in body_parts:
-            lines.append(self.emit_statement(b, indent + 1))
+            self._emit_stmt_recursive(b, lines, indent + 1)
         return "\n".join(lines)
 
     def _emit_cond(self, expr) -> str:
@@ -642,6 +661,16 @@ class PyEmitter:
         val = self.emit(val_expr)
         return f"{pad}{self._mangle(name)} = {val}"
 
+    def _emit_define_async(self, expr, indent: int = 0) -> str:
+        """Emit a define-async form as an async def statement."""
+        name = expr[1].name if isinstance(expr[1], Symbol) else str(expr[1])
+        val_expr = expr[2]
+        if (isinstance(val_expr, list) and val_expr and
+                isinstance(val_expr[0], Symbol) and val_expr[0].name in ("fn", "lambda")):
+            return self._emit_define_as_def(name, val_expr, indent, is_async=True)
+        # Shouldn't happen — define-async should always wrap fn/lambda
+        return self._emit_define(expr, indent)
+
     def _body_uses_set(self, fn_expr) -> bool:
         """Check if a fn expression's body (recursively) uses set!."""
         def _has_set(node):
@@ -654,12 +683,16 @@ class PyEmitter:
         body = fn_expr[2:]
         return any(_has_set(b) for b in body)
 
-    def _emit_define_as_def(self, name: str, fn_expr, indent: int = 0) -> str:
+    def _emit_define_as_def(self, name: str, fn_expr, indent: int = 0,
+                            is_async: bool = False) -> str:
         """Emit a define with fn value as a proper def statement.
 
         This is used for functions that contain set! — Python closures can't
         rebind outer lambda params, so we need proper def + local variables.
         Variables mutated by set! from nested lambdas use a _cells dict.
+
+        When is_async=True, emits 'async def' and sets _in_async so that
+        calls to other async functions receive 'await'.
         """
         pad = "    " * indent
         params = fn_expr[1]
@@ -686,14 +719,19 @@ class PyEmitter:
         py_name = self._mangle(name)
         # Find set! target variables that are used from nested lambda scopes
         nested_set_vars = self._find_nested_set_vars(body)
-        lines = [f"{pad}def {py_name}({params_str}):"]
+        def_kw = "async def" if is_async else "def"
+        lines = [f"{pad}{def_kw} {py_name}({params_str}):"]
         if nested_set_vars:
             lines.append(f"{pad}    _cells = {{}}")
-        # Emit body with cell var tracking
+        # Emit body with cell var tracking (and async context if needed)
         old_cells = getattr(self, '_current_cell_vars', set())
+        old_async = self._in_async
         self._current_cell_vars = nested_set_vars
+        if is_async:
+            self._in_async = True
         self._emit_body_stmts(body, lines, indent + 1)
         self._current_cell_vars = old_cells
+        self._in_async = old_async
         return "\n".join(lines)
 
     def _find_nested_set_vars(self, body) -> set[str]:
@@ -750,7 +788,7 @@ class PyEmitter:
             if is_last:
                 self._emit_return_expr(expr, lines, indent)
             else:
-                lines.append(self.emit_statement(expr, indent))
+                self._emit_stmt_recursive(expr, lines, indent)
 
     def _emit_return_expr(self, expr, lines: list, indent: int) -> None:
         """Emit an expression in return position, flattening control flow."""
@@ -775,6 +813,11 @@ class PyEmitter:
             if name in ("do", "begin"):
                 self._emit_body_stmts(expr[1:], lines, indent)
                 return
+            if name == "for-each":
+                # for-each in return position: emit as statement, return NIL
+                lines.append(self._emit_for_each_stmt(expr, indent))
+                lines.append(f"{pad}return NIL")
+                return
         lines.append(f"{pad}return {self.emit(expr)}")
 
     def _emit_if_return(self, expr, lines: list, indent: int) -> None:
@@ -1034,12 +1077,15 @@ class PyEmitter:
 # ---------------------------------------------------------------------------
 
 def extract_defines(source: str) -> list[tuple[str, list]]:
-    """Parse .sx source, return list of (name, define-expr) for top-level defines."""
+    """Parse .sx source, return list of (name, define-expr) for top-level defines.
+
+    Extracts both (define ...) and (define-async ...) forms.
+    """
     exprs = parse_all(source)
     defines = []
     for expr in exprs:
         if isinstance(expr, list) and expr and isinstance(expr[0], Symbol):
-            if expr[0].name == "define":
+            if expr[0].name in ("define", "define-async"):
                 name = expr[1].name if isinstance(expr[1], Symbol) else str(expr[1])
                 defines.append((name, expr))
     return defines
@@ -1212,6 +1258,28 @@ def compile_ref_to_py(
     for name in sorted(spec_mod_set):
         sx_files.append(SPEC_MODULES[name])
 
+    # Pre-scan define-async names (needed before transpilation so emitter
+    # knows which calls require 'await')
+    has_async = "async" in adapter_set
+    if has_async:
+        async_filename = ADAPTER_FILES["async"][0]
+        async_filepath = os.path.join(ref_dir, async_filename)
+        if os.path.exists(async_filepath):
+            with open(async_filepath) as f:
+                async_src = f.read()
+            for aexpr in parse_all(async_src):
+                if (isinstance(aexpr, list) and aexpr
+                        and isinstance(aexpr[0], Symbol)
+                        and aexpr[0].name == "define-async"):
+                    aname = aexpr[1].name if isinstance(aexpr[1], Symbol) else str(aexpr[1])
+                    emitter._async_names.add(aname)
+            # Platform async primitives (provided by host, also need await)
+            emitter._async_names.update({
+                "async-eval", "execute-io", "async-await!",
+            })
+        # Async adapter is transpiled last (after sync adapters)
+        sx_files.append(ADAPTER_FILES["async"])
+
     all_sections = []
     for filename, label in sx_files:
         filepath = os.path.join(ref_dir, filename)
@@ -1248,6 +1316,9 @@ def compile_ref_to_py(
     if has_deps:
         parts.append(PLATFORM_DEPS_PY)
 
+    if has_async:
+        parts.append(PLATFORM_ASYNC_PY)
+
     for label, defines in all_sections:
         parts.append(f"\n# === Transpiled from {label} ===\n")
         for name, expr in defines:
@@ -1258,7 +1329,7 @@ def compile_ref_to_py(
     parts.append(FIXUPS_PY)
     if has_continuations:
         parts.append(CONTINUATIONS_PY)
-    parts.append(public_api_py(has_html, has_sx, has_deps))
+    parts.append(public_api_py(has_html, has_sx, has_deps, has_async))
     return "\n".join(parts)
 
 

shared/sx/ref/js.sx

@@ -1290,8 +1290,9 @@
           (= name "append!")
             (str (js-expr (nth expr 1)) ".push(" (js-expr (nth expr 2)) ");")
           (= name "env-set!")
-            (str (js-expr (nth expr 1)) "[" (js-expr (nth expr 2))
+            (str "envSet(" (js-expr (nth expr 1))
-                 "] = " (js-expr (nth expr 3)) ";")
+                 ", " (js-expr (nth expr 2))
+                 ", " (js-expr (nth expr 3)) ");")
           (= name "set-lambda-name!")
             (str (js-expr (nth expr 1)) ".name = " (js-expr (nth expr 2)) ";")
           :else

shared/sx/ref/platform_js.py

@@ -1194,7 +1194,7 @@ PLATFORM_JS_PRE = '''
 
   // JSON / dict helpers for island state serialization
   function jsonSerialize(obj) {
-    try { return JSON.stringify(obj); } catch(e) { return "{}"; }
+    return JSON.stringify(obj);
   }
   function isEmptyDict(d) {
     if (!d || typeof d !== "object") return true;
@@ -1204,11 +1204,34 @@ 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 envSet(env, name, val) {
+    // Walk prototype chain to find where the variable is defined (for set!)
+    var obj = env;
+    while (obj !== null && obj !== Object.prototype) {
+      if (obj.hasOwnProperty(name)) { obj[name] = val; return; }
+      obj = Object.getPrototypeOf(obj);
+    }
+    // Not found in any parent scope — set on the immediate env
+    env[name] = val;
+  }
   function envExtend(env) { return Object.create(env); }
   function envMerge(base, overlay) {
+    // Same env or overlay is descendant of base — just extend, no copy.
+    // This prevents set! inside lambdas from modifying shadow copies.
+    if (base === overlay) return Object.create(base);
+    var p = overlay;
+    for (var d = 0; p && p !== Object.prototype && d < 100; d++) {
+      if (p === base) return Object.create(base);
+      p = Object.getPrototypeOf(p);
+    }
+    // General case: extend base, copy ONLY overlay properties that don't
+    // exist in the base chain (avoids shadowing closure bindings).
     var child = Object.create(base);
-    if (overlay) for (var k in overlay) if (overlay.hasOwnProperty(k)) child[k] = overlay[k];
+    if (overlay) {
+      for (var k in overlay) {
+        if (overlay.hasOwnProperty(k) && !(k in base)) child[k] = overlay[k];
+      }
+    }
     return child;
   }
 
@@ -1649,8 +1672,11 @@ PLATFORM_DOM_JS = """
   function domListen(el, name, handler) {
     if (!_hasDom || !el) return function() {};
     // Wrap SX lambdas from runtime-evaluated island code into native fns
+    // If lambda takes 0 params, call without event arg (convenience for on-click handlers)
     var wrapped = isLambda(handler)
-      ? function(e) { try { invoke(handler, e); } catch(err) { console.error("[sx-ref] domListen handler error:", name, err); } }
+      ? (lambdaParams(handler).length === 0
+        ? function(e) { try { invoke(handler); } catch(err) { console.error("[sx-ref] domListen handler error:", name, err); } }
+        : function(e) { try { invoke(handler, e); } catch(err) { console.error("[sx-ref] domListen handler error:", name, err); } })
       : handler;
     if (name === "click") logInfo("domListen: click on <" + (el.tagName||"?").toLowerCase() + "> text=" + (el.textContent||"").substring(0,20) + " isLambda=" + isLambda(handler));
     el.addEventListener(name, wrapped);

shared/sx/ref/platform_py.py

@@ -462,10 +462,7 @@ def invoke(f, *args):
 
 def json_serialize(obj):
     import json
-    try:
+    return json.dumps(obj)
-        return json.dumps(obj)
-    except (TypeError, ValueError):
-        return "{}"
 
 
 def is_empty_dict(d):
@@ -1067,10 +1064,19 @@ import inspect
 
 from shared.sx.primitives_io import (
     IO_PRIMITIVES, RequestContext, execute_io,
-    css_class_collector as _css_class_collector_cv,
-    _svg_context as _svg_context_cv,
 )
 
+# Lazy imports to avoid circular dependency (html.py imports sx_ref.py)
+_css_class_collector_cv = None
+_svg_context_cv = None
+
+def _ensure_html_imports():
+    global _css_class_collector_cv, _svg_context_cv
+    if _css_class_collector_cv is None:
+        from shared.sx.html import css_class_collector, _svg_context
+        _css_class_collector_cv = css_class_collector
+        _svg_context_cv = _svg_context
+
 # When True, async_aser expands known components server-side
 _expand_components_cv: contextvars.ContextVar[bool] = contextvars.ContextVar(
     "_expand_components_ref", default=False
@@ -1094,18 +1100,22 @@ def expand_components_p():
 
 
 def svg_context_p():
+    _ensure_html_imports()
     return _svg_context_cv.get(False)
 
 
 def svg_context_set(val):
+    _ensure_html_imports()
     return _svg_context_cv.set(val)
 
 
 def svg_context_reset(token):
+    _ensure_html_imports()
     _svg_context_cv.reset(token)
 
 
 def css_class_collect(val):
+    _ensure_html_imports()
     collector = _css_class_collector_cv.get(None)
     if collector is not None:
         collector.update(str(val).split())
@@ -1123,6 +1133,25 @@ def is_sx_expr(x):
     return isinstance(x, SxExpr)
 
 
+# Predicate helpers used by adapter-async (these are in PRIMITIVES but
+# the bootstrapped code calls them as plain functions)
+def string_p(x):
+    return isinstance(x, str)
+
+
+def list_p(x):
+    return isinstance(x, _b_list)
+
+
+def number_p(x):
+    return isinstance(x, (int, float)) and not isinstance(x, bool)
+
+
+def sx_parse(src):
+    from shared.sx.parser import parse_all
+    return parse_all(src)
+
+
 def is_async_coroutine(x):
     return inspect.iscoroutine(x)
 
@@ -1199,48 +1228,16 @@ async def async_eval_slot_to_sx(expr, env, ctx=None):
         ctx = RequestContext()
     token = _expand_components_cv.set(True)
     try:
-        return await _eval_slot_inner(expr, env, ctx)
+        result = await async_eval_slot_inner(expr, env, ctx)
+        if isinstance(result, SxExpr):
+            return result
+        if result is None or result is NIL:
+            return SxExpr("")
+        if isinstance(result, str):
+            return SxExpr(result)
+        return SxExpr(sx_serialize(result))
     finally:
         _expand_components_cv.reset(token)
-
-
-async def _eval_slot_inner(expr, env, ctx):
-    if isinstance(expr, list) and expr:
-        head = expr[0]
-        if isinstance(head, Symbol) and head.name.startswith("~"):
-            comp = env.get(head.name)
-            if isinstance(comp, Component):
-                result = await async_aser_component(comp, expr[1:], env, ctx)
-                if isinstance(result, SxExpr):
-                    return result
-                if result is None or result is NIL:
-                    return SxExpr("")
-                if isinstance(result, str):
-                    return SxExpr(result)
-                return SxExpr(sx_serialize(result))
-    result = await async_aser(expr, env, ctx)
-    result = await _maybe_expand_component_result(result, env, ctx)
-    if isinstance(result, SxExpr):
-        return result
-    if result is None or result is NIL:
-        return SxExpr("")
-    if isinstance(result, str):
-        return SxExpr(result)
-    return SxExpr(sx_serialize(result))
-
-
-async def _maybe_expand_component_result(result, env, ctx):
-    raw = None
-    if isinstance(result, SxExpr):
-        raw = str(result).strip()
-    elif isinstance(result, str):
-        raw = result.strip()
-    if raw and raw.startswith("(~"):
-        from shared.sx.parser import parse_all as _pa
-        parsed = _pa(raw)
-        if parsed:
-            return await async_eval_slot_to_sx(parsed[0], env, ctx)
-    return result
 '''
 
 # ---------------------------------------------------------------------------
@@ -1366,7 +1363,8 @@ aser_special = _aser_special_with_continuations
 # Public API generator
 # ---------------------------------------------------------------------------
 
-def public_api_py(has_html: bool, has_sx: bool, has_deps: bool = False) -> str:
+def public_api_py(has_html: bool, has_sx: bool, has_deps: bool = False,
+                  has_async: bool = False) -> str:
     lines = [
         '',
         '# =========================================================================',
@@ -1419,8 +1417,9 @@ def public_api_py(has_html: bool, has_sx: bool, has_deps: bool = False) -> str:
 # ---------------------------------------------------------------------------
 
 ADAPTER_FILES = {
-    "html": ("adapter-html.sx", "adapter-html"),
+    "html":  ("adapter-html.sx",  "adapter-html"),
-    "sx":   ("adapter-sx.sx",   "adapter-sx"),
+    "sx":    ("adapter-sx.sx",    "adapter-sx"),
+    "async": ("adapter-async.sx", "adapter-async"),
 }
 
 SPEC_MODULES = {

shared/sx/ref/render.sx

@@ -178,7 +178,9 @@
 ;; bindings = ((name1 expr1) (name2 expr2) ...)
 (define process-bindings
   (fn (bindings env)
-    (let ((local (merge env)))
+    ;; env-extend (not merge) — Env is not a dict subclass, so merge()
+    ;; returns an empty dict, losing all parent scope bindings.
+    (let ((local (env-extend env)))
       (for-each
         (fn (pair)
           (when (and (= (type-of pair) "list") (>= (len pair) 2))

shared/sx/ref/test-aser.sx

@@ -119,6 +119,19 @@
     (assert-equal "(p \"hello\")"
       (render-sx "(let ((x \"hello\")) (p x))")))
 
+  (deftest "let preserves outer scope bindings"
+    ;; Regression: process-bindings must preserve parent env scope chain.
+    ;; Using merge() instead of env-extend loses parent scope items.
+    (assert-equal "(p \"outer\")"
+      (render-sx "(do (define theme \"outer\") (let ((x 1)) (p theme)))")))
+
+  (deftest "nested let preserves outer scope"
+    (assert-equal "(div (span \"hello\") (span \"world\"))"
+      (render-sx "(do (define a \"hello\")
+                      (define b \"world\")
+                      (div (let ((x 1)) (span a))
+                           (let ((y 2)) (span b))))")))
+
   (deftest "begin serializes last"
     (assert-equal "(p \"last\")"
       (render-sx "(begin (p \"first\") (p \"last\"))"))))
@@ -213,6 +226,17 @@
     (assert-equal "10"
       (render-sx "(do (define double (fn (x) (* x 2))) (double 5))")))
 
+  (deftest "native callable with multiple args"
+    ;; Regression: async-aser-eval-call passed evaled-args list to
+    ;; async-invoke (&rest), wrapping it in another list. apply(f, [list])
+    ;; calls f(list) instead of f(*list).
+    (assert-equal "3"
+      (render-sx "(do (define my-add +) (my-add 1 2))")))
+
+  (deftest "native callable with two args via alias"
+    (assert-equal "hello world"
+      (render-sx "(do (define my-join str) (my-join \"hello\" \" world\"))")))
+
   (deftest "higher-order: map returns list"
     (let ((result (render-sx "(map (fn (x) (+ x 1)) (list 1 2 3))")))
       ;; map at top level returns a list, not serialized tags

shared/sx/ref/test-render.sx

@@ -149,7 +149,20 @@
 
   (deftest "let in render context"
     (assert-equal "<p>hello</p>"
-      (render-html "(let ((x \"hello\")) (p x))"))))
+      (render-html "(let ((x \"hello\")) (p x))")))
+
+  (deftest "let preserves outer scope bindings"
+    ;; Regression: process-bindings must preserve parent env scope chain.
+    ;; Using merge() on Env objects returns empty dict (Env is not dict subclass).
+    (assert-equal "<p>outer</p>"
+      (render-html "(do (define theme \"outer\") (let ((x 1)) (p theme)))")))
+
+  (deftest "nested let preserves outer scope"
+    (assert-equal "<div><span>hello</span><span>world</span></div>"
+      (render-html "(do (define a \"hello\")
+                        (define b \"world\")
+                        (div (let ((x 1)) (span a))
+                             (let ((y 2)) (span b))))"))))
 
 
 ;; --------------------------------------------------------------------------

shared/sx/tests/run.py

@@ -127,7 +127,8 @@ def render_html(sx_source):
     except ImportError:
         raise RuntimeError("render-to-html not available — sx_ref.py not built")
     exprs = parse_all(sx_source)
-    render_env = dict(env)
+    # Use Env (not flat dict) so tests exercise the real scope chain path.
+    render_env = _Env(dict(env))
     result = ""
     for expr in exprs:
         result += _render_to_html(expr, render_env)
@@ -143,7 +144,9 @@ def render_sx(sx_source):
     except ImportError:
         raise RuntimeError("aser not available — sx_ref.py not built")
     exprs = parse_all(sx_source)
-    render_env = dict(env)
+    # Use Env (not flat dict) so tests exercise the real scope chain path.
+    # Using dict(env) hides bugs where merge() drops Env parent scopes.
+    render_env = _Env(dict(env))
     result = ""
     for expr in exprs:
         val = _aser(expr, render_env)

sx/sx/page-helpers-demo.sx

@@ -42,7 +42,6 @@
                  (sf-ms (- (now-ms) t1))
                  (sf-cats {})
                  (sf-total 0)
-
                  ;; 2. build-reference-data
                  (t2 (now-ms))
                  (ref-result (build-reference-data "attributes"