Add provide/context/emit!/emitted — render-time dynamic scope

Four new primitives for scoped downward value passing and upward
accumulation through the render tree. Specced in .sx, bootstrapped
to Python and JS across all adapters (eval, html, sx, dom, async).

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 = "2026-03-13T02:18:19Z";
+  var SX_VERSION = "2026-03-13T02:54:01Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
@@ -87,6 +87,7 @@
   SxSpread.prototype._spread = true;
 
   var _collectBuckets = {};
+  var _provideStacks = {};
 
   function isSym(x) { return x != null && x._sym === true; }
   function isKw(x) { return x != null && x._kw === true; }
@@ -162,6 +163,35 @@
     if (_collectBuckets[bucket]) _collectBuckets[bucket] = [];
   }
 
+  function providePush(name, value) {
+    if (!_provideStacks[name]) _provideStacks[name] = [];
+    _provideStacks[name].push({value: value !== undefined ? value : NIL, emitted: []});
+  }
+  function providePop(name) {
+    if (_provideStacks[name] && _provideStacks[name].length) _provideStacks[name].pop();
+  }
+  function sxContext(name) {
+    if (_provideStacks[name] && _provideStacks[name].length) {
+      return _provideStacks[name][_provideStacks[name].length - 1].value;
+    }
+    if (arguments.length > 1) return arguments[1];
+    throw new Error("No provider for: " + name);
+  }
+  function sxEmit(name, value) {
+    if (_provideStacks[name] && _provideStacks[name].length) {
+      _provideStacks[name][_provideStacks[name].length - 1].emitted.push(value);
+    } else {
+      throw new Error("No provider for emit!: " + name);
+    }
+    return NIL;
+  }
+  function sxEmitted(name) {
+    if (_provideStacks[name] && _provideStacks[name].length) {
+      return _provideStacks[name][_provideStacks[name].length - 1].emitted.slice();
+    }
+    return [];
+  }
+
   function lambdaParams(f) { return f.params; }
   function lambdaBody(f) { return f.body; }
   function lambdaClosure(f) { return f.closure; }
@@ -495,6 +525,12 @@
   PRIMITIVES["collect!"] = sxCollect;
   PRIMITIVES["collected"] = sxCollected;
   PRIMITIVES["clear-collected!"] = sxClearCollected;
+  // provide/context/emit! — render-time dynamic scope
+  PRIMITIVES["provide-push!"] = providePush;
+  PRIMITIVES["provide-pop!"] = providePop;
+  PRIMITIVES["context"] = sxContext;
+  PRIMITIVES["emit!"] = sxEmit;
+  PRIMITIVES["emitted"] = sxEmitted;
 
 
   function isPrimitive(name) { return name in PRIMITIVES; }
@@ -760,10 +796,10 @@
   var args = rest(expr);
   return (isSxTruthy(!isSxTruthy(sxOr((typeOf(head) == "symbol"), (typeOf(head) == "lambda"), (typeOf(head) == "list")))) ? map(function(x) { return trampoline(evalExpr(x, env)); }, expr) : (isSxTruthy((typeOf(head) == "symbol")) ? (function() {
   var name = symbolName(head);
-  return (isSxTruthy((name == "if")) ? sfIf(args, env) : (isSxTruthy((name == "when")) ? sfWhen(args, env) : (isSxTruthy((name == "cond")) ? sfCond(args, env) : (isSxTruthy((name == "case")) ? sfCase(args, env) : (isSxTruthy((name == "and")) ? sfAnd(args, env) : (isSxTruthy((name == "or")) ? sfOr(args, env) : (isSxTruthy((name == "let")) ? sfLet(args, env) : (isSxTruthy((name == "let*")) ? sfLet(args, env) : (isSxTruthy((name == "letrec")) ? sfLetrec(args, env) : (isSxTruthy((name == "lambda")) ? sfLambda(args, env) : (isSxTruthy((name == "fn")) ? sfLambda(args, env) : (isSxTruthy((name == "define")) ? sfDefine(args, env) : (isSxTruthy((name == "defcomp")) ? sfDefcomp(args, env) : (isSxTruthy((name == "defisland")) ? sfDefisland(args, env) : (isSxTruthy((name == "defmacro")) ? sfDefmacro(args, env) : (isSxTruthy((name == "defstyle")) ? sfDefstyle(args, env) : (isSxTruthy((name == "defhandler")) ? sfDefhandler(args, env) : (isSxTruthy((name == "defpage")) ? sfDefpage(args, env) : (isSxTruthy((name == "defquery")) ? sfDefquery(args, env) : (isSxTruthy((name == "defaction")) ? sfDefaction(args, env) : (isSxTruthy((name == "deftype")) ? sfDeftype(args, env) : (isSxTruthy((name == "defeffect")) ? sfDefeffect(args, env) : (isSxTruthy((name == "begin")) ? sfBegin(args, env) : (isSxTruthy((name == "do")) ? sfBegin(args, env) : (isSxTruthy((name == "quote")) ? sfQuote(args, env) : (isSxTruthy((name == "quasiquote")) ? sfQuasiquote(args, env) : (isSxTruthy((name == "->")) ? sfThreadFirst(args, env) : (isSxTruthy((name == "set!")) ? sfSetBang(args, env) : (isSxTruthy((name == "reset")) ? sfReset(args, env) : (isSxTruthy((name == "shift")) ? sfShift(args, env) : (isSxTruthy((name == "dynamic-wind")) ? sfDynamicWind(args, env) : (isSxTruthy((name == "map")) ? hoMap(args, env) : (isSxTruthy((name == "map-indexed")) ? hoMapIndexed(args, env) : (isSxTruthy((name == "filter")) ? hoFilter(args, env) : (isSxTruthy((name == "reduce")) ? hoReduce(args, env) : (isSxTruthy((name == "some")) ? hoSome(args, env) : (isSxTruthy((name == "every?")) ? hoEvery(args, env) : (isSxTruthy((name == "for-each")) ? hoForEach(args, env) : (isSxTruthy((isSxTruthy(envHas(env, name)) && isMacro(envGet(env, name)))) ? (function() {
+  return (isSxTruthy((name == "if")) ? sfIf(args, env) : (isSxTruthy((name == "when")) ? sfWhen(args, env) : (isSxTruthy((name == "cond")) ? sfCond(args, env) : (isSxTruthy((name == "case")) ? sfCase(args, env) : (isSxTruthy((name == "and")) ? sfAnd(args, env) : (isSxTruthy((name == "or")) ? sfOr(args, env) : (isSxTruthy((name == "let")) ? sfLet(args, env) : (isSxTruthy((name == "let*")) ? sfLet(args, env) : (isSxTruthy((name == "letrec")) ? sfLetrec(args, env) : (isSxTruthy((name == "lambda")) ? sfLambda(args, env) : (isSxTruthy((name == "fn")) ? sfLambda(args, env) : (isSxTruthy((name == "define")) ? sfDefine(args, env) : (isSxTruthy((name == "defcomp")) ? sfDefcomp(args, env) : (isSxTruthy((name == "defisland")) ? sfDefisland(args, env) : (isSxTruthy((name == "defmacro")) ? sfDefmacro(args, env) : (isSxTruthy((name == "defstyle")) ? sfDefstyle(args, env) : (isSxTruthy((name == "defhandler")) ? sfDefhandler(args, env) : (isSxTruthy((name == "defpage")) ? sfDefpage(args, env) : (isSxTruthy((name == "defquery")) ? sfDefquery(args, env) : (isSxTruthy((name == "defaction")) ? sfDefaction(args, env) : (isSxTruthy((name == "deftype")) ? sfDeftype(args, env) : (isSxTruthy((name == "defeffect")) ? sfDefeffect(args, env) : (isSxTruthy((name == "begin")) ? sfBegin(args, env) : (isSxTruthy((name == "do")) ? sfBegin(args, env) : (isSxTruthy((name == "quote")) ? sfQuote(args, env) : (isSxTruthy((name == "quasiquote")) ? sfQuasiquote(args, env) : (isSxTruthy((name == "->")) ? sfThreadFirst(args, env) : (isSxTruthy((name == "set!")) ? sfSetBang(args, env) : (isSxTruthy((name == "reset")) ? sfReset(args, env) : (isSxTruthy((name == "shift")) ? sfShift(args, env) : (isSxTruthy((name == "dynamic-wind")) ? sfDynamicWind(args, env) : (isSxTruthy((name == "provide")) ? sfProvide(args, env) : (isSxTruthy((name == "map")) ? hoMap(args, env) : (isSxTruthy((name == "map-indexed")) ? hoMapIndexed(args, env) : (isSxTruthy((name == "filter")) ? hoFilter(args, env) : (isSxTruthy((name == "reduce")) ? hoReduce(args, env) : (isSxTruthy((name == "some")) ? hoSome(args, env) : (isSxTruthy((name == "every?")) ? hoEvery(args, env) : (isSxTruthy((name == "for-each")) ? hoForEach(args, env) : (isSxTruthy((isSxTruthy(envHas(env, name)) && isMacro(envGet(env, name)))) ? (function() {
   var mac = envGet(env, name);
   return makeThunk(expandMacro(mac, args, env), env);
-})() : (isSxTruthy((isSxTruthy(renderActiveP()) && isRenderExpr(expr))) ? renderExpr(expr, env) : evalCall(head, args, env)))))))))))))))))))))))))))))))))))))))));
+})() : (isSxTruthy((isSxTruthy(renderActiveP()) && isRenderExpr(expr))) ? renderExpr(expr, env) : evalCall(head, args, env))))))))))))))))))))))))))))))))))))))))));
 })() : evalCall(head, args, env)));
 })(); };
 
@@ -1170,6 +1206,18 @@ return append_b(inits, nth(binding, 1)); }, bindings) : reduce(function(acc, pai
 })();
 })(); };
 
+  // sf-provide
+  var sfProvide = function(args, env) { return (function() {
+  var name = trampoline(evalExpr(first(args), env));
+  var val = trampoline(evalExpr(nth(args, 1), env));
+  var bodyExprs = slice(args, 2);
+  var result = NIL;
+  providePush(name, val);
+  { var _c = bodyExprs; for (var _i = 0; _i < _c.length; _i++) { var e = _c[_i]; result = trampoline(evalExpr(e, env)); } }
+  providePop(name);
+  return result;
+})(); };
+
   // expand-macro
   var expandMacro = function(mac, rawArgs, env) { return (function() {
   var local = envMerge(macroClosure(mac), env);
@@ -1468,7 +1516,7 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return ""; if (_m =
   var renderValueToHtml = function(val, env) { return (function() { var _m = typeOf(val); if (_m == "nil") return ""; if (_m == "string") return escapeHtml(val); if (_m == "number") return (String(val)); if (_m == "boolean") return (isSxTruthy(val) ? "true" : "false"); if (_m == "list") return renderListToHtml(val, env); if (_m == "raw-html") return rawHtmlContent(val); if (_m == "spread") return val; return escapeHtml((String(val))); })(); };
 
   // RENDER_HTML_FORMS
-  var RENDER_HTML_FORMS = ["if", "when", "cond", "case", "let", "let*", "begin", "do", "define", "defcomp", "defisland", "defmacro", "defstyle", "defhandler", "deftype", "defeffect", "map", "map-indexed", "filter", "for-each"];
+  var RENDER_HTML_FORMS = ["if", "when", "cond", "case", "let", "let*", "begin", "do", "define", "defcomp", "defisland", "defmacro", "defstyle", "defhandler", "deftype", "defeffect", "map", "map-indexed", "filter", "for-each", "provide"];
 
   // render-html-form?
   var isRenderHtmlForm = function(name) { return contains(RENDER_HTML_FORMS, name); };
@@ -1517,7 +1565,18 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return ""; if (_m =
   var f = trampoline(evalExpr(nth(expr, 1), env));
   var coll = trampoline(evalExpr(nth(expr, 2), env));
   return join("", filter(function(r) { return !isSxTruthy(isSpread(r)); }, map(function(item) { return (isSxTruthy(isLambda(f)) ? renderLambdaHtml(f, [item], env) : renderToHtml(apply(f, [item]), env)); }, coll)));
-})() : renderValueToHtml(trampoline(evalExpr(expr, env)), env)))))))))))); };
+})() : (isSxTruthy((name == "provide")) ? (function() {
+  var provName = trampoline(evalExpr(nth(expr, 1), env));
+  var provVal = trampoline(evalExpr(nth(expr, 2), env));
+  var bodyStart = 3;
+  var bodyCount = (len(expr) - 3);
+  providePush(provName, provVal);
+  return (function() {
+  var result = (isSxTruthy((bodyCount == 1)) ? renderToHtml(nth(expr, bodyStart), env) : join("", filter(function(r) { return !isSxTruthy(isSpread(r)); }, map(function(i) { return renderToHtml(nth(expr, i), env); }, range(bodyStart, (bodyStart + bodyCount))))));
+  providePop(provName);
+  return result;
+})();
+})() : renderValueToHtml(trampoline(evalExpr(expr, env)), env))))))))))))); };
 
   // render-lambda-html
   var renderLambdaHtml = function(f, args, env) { return (function() {
@@ -1722,7 +1781,7 @@ return (function() { var _m = typeOf(expr); if (_m == "number") return expr; if
 })(); };
 
   // SPECIAL_FORM_NAMES
-  var SPECIAL_FORM_NAMES = ["if", "when", "cond", "case", "and", "or", "let", "let*", "lambda", "fn", "define", "defcomp", "defmacro", "defstyle", "defhandler", "defpage", "defquery", "defaction", "defrelation", "begin", "do", "quote", "quasiquote", "->", "set!", "letrec", "dynamic-wind", "defisland", "deftype", "defeffect"];
+  var SPECIAL_FORM_NAMES = ["if", "when", "cond", "case", "and", "or", "let", "let*", "lambda", "fn", "define", "defcomp", "defmacro", "defstyle", "defhandler", "defpage", "defquery", "defaction", "defrelation", "begin", "do", "quote", "quasiquote", "->", "set!", "letrec", "dynamic-wind", "defisland", "deftype", "defeffect", "provide"];
 
   // HO_FORM_NAMES
   var HO_FORM_NAMES = ["map", "map-indexed", "filter", "reduce", "some", "every?", "for-each"];
@@ -1793,7 +1852,15 @@ return result; }, args);
   return append_b(results, aser(lambdaBody(f), local));
 })() : invoke(f, item)); } }
   return (isSxTruthy(isEmpty(results)) ? NIL : results);
-})() : (isSxTruthy((name == "defisland")) ? (trampoline(evalExpr(expr, env)), serialize(expr)) : (isSxTruthy(sxOr((name == "define"), (name == "defcomp"), (name == "defmacro"), (name == "defstyle"), (name == "defhandler"), (name == "defpage"), (name == "defquery"), (name == "defaction"), (name == "defrelation"), (name == "deftype"), (name == "defeffect"))) ? (trampoline(evalExpr(expr, env)), NIL) : trampoline(evalExpr(expr, env)))))))))))))));
+})() : (isSxTruthy((name == "defisland")) ? (trampoline(evalExpr(expr, env)), serialize(expr)) : (isSxTruthy(sxOr((name == "define"), (name == "defcomp"), (name == "defmacro"), (name == "defstyle"), (name == "defhandler"), (name == "defpage"), (name == "defquery"), (name == "defaction"), (name == "defrelation"), (name == "deftype"), (name == "defeffect"))) ? (trampoline(evalExpr(expr, env)), NIL) : (isSxTruthy((name == "provide")) ? (function() {
+  var provName = trampoline(evalExpr(first(args), env));
+  var provVal = trampoline(evalExpr(nth(args, 1), env));
+  var result = NIL;
+  providePush(provName, provVal);
+  { var _c = slice(args, 2); for (var _i = 0; _i < _c.length; _i++) { var body = _c[_i]; result = aser(body, env); } }
+  providePop(provName);
+  return result;
+})() : trampoline(evalExpr(expr, env))))))))))))))));
 })(); };
 
   // eval-case-aser
@@ -1926,7 +1993,7 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return createFragme
   var renderDomUnknownComponent = function(name) { return error((String("Unknown component: ") + String(name))); };
 
   // RENDER_DOM_FORMS
-  var RENDER_DOM_FORMS = ["if", "when", "cond", "case", "let", "let*", "begin", "do", "define", "defcomp", "defisland", "defmacro", "defstyle", "defhandler", "map", "map-indexed", "filter", "for-each", "portal", "error-boundary"];
+  var RENDER_DOM_FORMS = ["if", "when", "cond", "case", "let", "let*", "begin", "do", "define", "defcomp", "defisland", "defmacro", "defstyle", "defhandler", "map", "map-indexed", "filter", "for-each", "portal", "error-boundary", "provide"];
 
   // render-dom-form?
   var isRenderDomForm = function(name) { return contains(RENDER_DOM_FORMS, name); };
@@ -2060,7 +2127,15 @@ return (function() { var _m = typeOf(expr); if (_m == "nil") return createFragme
   return domAppend(frag, val);
 })(); } }
   return frag;
-})() : renderToDom(trampoline(evalExpr(expr, env)), env, ns)))))))))))))); };
+})() : (isSxTruthy((name == "provide")) ? (function() {
+  var provName = trampoline(evalExpr(nth(expr, 1), env));
+  var provVal = trampoline(evalExpr(nth(expr, 2), env));
+  var frag = createFragment();
+  providePush(provName, provVal);
+  { var _c = range(3, len(expr)); for (var _i = 0; _i < _c.length; _i++) { var i = _c[_i]; domAppend(frag, renderToDom(nth(expr, i), env, ns)); } }
+  providePop(provName);
+  return frag;
+})() : renderToDom(trampoline(evalExpr(expr, env)), env, ns))))))))))))))); };
 
   // render-lambda-dom
   var renderLambdaDom = function(f, args, env, ns) { return (function() {
@@ -6453,6 +6528,11 @@ return (isSxTruthy((_batchDepth == 0)) ? (function() {
     collect: sxCollect,
     collected: sxCollected,
     clearCollected: sxClearCollected,
+    providePush: providePush,
+    providePop: providePop,
+    context: sxContext,
+    emit: sxEmit,
+    emitted: sxEmitted,
     _version: "ref-2.0 (boot+dom+engine+html+orchestration+parser+sx, bootstrap-compiled)"
   };
 

shared/sx/ref/adapter-async.sx

@@ -341,7 +341,7 @@
   (list "if" "when" "cond" "case" "let" "let*" "begin" "do"
         "define" "defcomp" "defisland" "defmacro" "defstyle" "defhandler"
         "deftype" "defeffect"
-        "map" "map-indexed" "filter" "for-each"))
+        "map" "map-indexed" "filter" "for-each" "provide"))
 
 (define async-render-form? :effects []
   (fn ((name :as string))
@@ -434,6 +434,20 @@
             (filter (fn (r) (not (spread? r)))
               (async-map-fn-render f coll env ctx))))
 
+      ;; provide — render-time dynamic scope
+      (= name "provide")
+        (let ((prov-name (async-eval (nth expr 1) env ctx))
+              (prov-val (async-eval (nth expr 2) env ctx))
+              (body-start 3)
+              (body-count (- (len expr) 3)))
+          (provide-push! prov-name prov-val)
+          (let ((result (if (= body-count 1)
+                          (async-render (nth expr body-start) env ctx)
+                          (let ((results (async-map-render (slice expr body-start) env ctx)))
+                            (join "" (filter (fn (r) (not (spread? r))) results))))))
+            (provide-pop! prov-name)
+            result))
+
       ;; Fallback
       :else
         (async-render (async-eval expr env ctx) env ctx))))
@@ -894,7 +908,7 @@
         "define" "defcomp" "defmacro" "defstyle"
         "defhandler" "defpage" "defquery" "defaction"
         "begin" "do" "quote" "->" "set!" "defisland"
-        "deftype" "defeffect"))
+        "deftype" "defeffect" "provide"))
 
 (define ASYNC_ASER_HO_NAMES
   (list "map" "map-indexed" "filter" "for-each"))
@@ -1032,6 +1046,17 @@
             (= name "deftype") (= name "defeffect"))
           (do (async-eval expr env ctx) nil)
 
+        ;; provide — render-time dynamic scope
+        (= name "provide")
+          (let ((prov-name (async-eval (first args) env ctx))
+                (prov-val (async-eval (nth args 1) env ctx))
+                (result nil))
+            (provide-push! prov-name prov-val)
+            (for-each (fn (body) (set! result (async-aser body env ctx)))
+                      (slice args 2))
+            (provide-pop! prov-name)
+            result)
+
         ;; Fallback
         :else
           (async-eval expr env ctx)))))

shared/sx/ref/adapter-dom.sx

@@ -359,7 +359,7 @@
   (list "if" "when" "cond" "case" "let" "let*" "begin" "do"
         "define" "defcomp" "defisland" "defmacro" "defstyle" "defhandler"
         "map" "map-indexed" "filter" "for-each" "portal"
-        "error-boundary"))
+        "error-boundary" "provide"))
 
 (define render-dom-form? :effects []
   (fn ((name :as string))
@@ -598,6 +598,19 @@
             coll)
           frag)
 
+      ;; provide — render-time dynamic scope
+      (= name "provide")
+        (let ((prov-name (trampoline (eval-expr (nth expr 1) env)))
+              (prov-val (trampoline (eval-expr (nth expr 2) env)))
+              (frag (create-fragment)))
+          (provide-push! prov-name prov-val)
+          (for-each
+            (fn (i)
+              (dom-append frag (render-to-dom (nth expr i) env ns)))
+            (range 3 (len expr)))
+          (provide-pop! prov-name)
+          frag)
+
       ;; Fallback
       :else
         (render-to-dom (trampoline (eval-expr expr env)) env ns))))

shared/sx/ref/adapter-html.sx

@@ -56,7 +56,7 @@
   (list "if" "when" "cond" "case" "let" "let*" "begin" "do"
         "define" "defcomp" "defisland" "defmacro" "defstyle" "defhandler"
         "deftype" "defeffect"
-        "map" "map-indexed" "filter" "for-each"))
+        "map" "map-indexed" "filter" "for-each" "provide"))
 
 (define render-html-form? :effects []
   (fn ((name :as string))
@@ -237,6 +237,21 @@
                     (render-to-html (apply f (list item)) env)))
                 coll))))
 
+      ;; provide — render-time dynamic scope
+      (= name "provide")
+        (let ((prov-name (trampoline (eval-expr (nth expr 1) env)))
+              (prov-val (trampoline (eval-expr (nth expr 2) env)))
+              (body-start 3)
+              (body-count (- (len expr) 3)))
+          (provide-push! prov-name prov-val)
+          (let ((result (if (= body-count 1)
+                          (render-to-html (nth expr body-start) env)
+                          (join "" (filter (fn (r) (not (spread? r)))
+                                    (map (fn (i) (render-to-html (nth expr i) env))
+                                         (range body-start (+ body-start body-count))))))))
+            (provide-pop! prov-name)
+            result))
+
       ;; Fallback
       :else
         (render-value-to-html (trampoline (eval-expr expr env)) env))))

shared/sx/ref/adapter-sx.sx

@@ -174,7 +174,7 @@
         "defhandler" "defpage" "defquery" "defaction" "defrelation"
         "begin" "do" "quote" "quasiquote"
         "->" "set!" "letrec" "dynamic-wind" "defisland"
-        "deftype" "defeffect"))
+        "deftype" "defeffect" "provide"))
 
 (define HO_FORM_NAMES
   (list "map" "map-indexed" "filter" "reduce"
@@ -312,6 +312,17 @@
             (= name "deftype") (= name "defeffect"))
           (do (trampoline (eval-expr expr env)) nil)
 
+        ;; provide — render-time dynamic scope
+        (= name "provide")
+          (let ((prov-name (trampoline (eval-expr (first args) env)))
+                (prov-val (trampoline (eval-expr (nth args 1) env)))
+                (result nil))
+            (provide-push! prov-name prov-val)
+            (for-each (fn (body) (set! result (aser body env)))
+                      (slice args 2))
+            (provide-pop! prov-name)
+            result)
+
         ;; Everything else — evaluate normally
         :else
           (trampoline (eval-expr expr env))))))

shared/sx/ref/bootstrap_py.py

@@ -293,6 +293,11 @@ class PyEmitter:
             "collect!": "sx_collect",
             "collected": "sx_collected",
             "clear-collected!": "sx_clear_collected",
+            "provide-push!": "provide_push",
+            "provide-pop!": "provide_pop",
+            "context": "sx_context",
+            "emit!": "sx_emit",
+            "emitted": "sx_emitted",
             "is-raw-html?": "is_raw_html",
             "async-coroutine?": "is_async_coroutine",
             "async-await!": "async_await",

shared/sx/ref/boundary.sx

@@ -371,3 +371,51 @@
   :effects [mutation]
   :doc "Clear a named render-time accumulator bucket. Used at flush points
         after emitting collected values (e.g. after writing a <style> tag).")
+
+
+;; --------------------------------------------------------------------------
+;; Tier 5: Dynamic scope — render-time provide/context/emit!
+;;
+;; `provide` is a special form (not a primitive) that creates a named scope
+;; with a value and an empty accumulator. `context` reads the value from the
+;; nearest enclosing provider. `emit!` appends to the accumulator, `emitted`
+;; reads the accumulated values.
+;;
+;; The platform must implement per-name stacks. Each entry has a value and
+;; an emitted list. `provide-push!`/`provide-pop!` manage the stack.
+;; --------------------------------------------------------------------------
+
+(declare-tier :dynamic-scope :source "eval.sx")
+
+(declare-spread-primitive "provide-push!"
+  :params (name value)
+  :returns "nil"
+  :effects [mutation]
+  :doc "Push a provider scope with name and value (platform internal).")
+
+(declare-spread-primitive "provide-pop!"
+  :params (name)
+  :returns "nil"
+  :effects [mutation]
+  :doc "Pop the most recent provider scope for name (platform internal).")
+
+(declare-spread-primitive "context"
+  :params (name &rest default)
+  :returns "any"
+  :effects []
+  :doc "Read value from nearest enclosing provide with matching name.
+        Errors if no provider and no default given.")
+
+(declare-spread-primitive "emit!"
+  :params (name value)
+  :returns "nil"
+  :effects [mutation]
+  :doc "Append value to nearest enclosing provide's accumulator.
+        Errors if no matching provider. No deduplication.")
+
+(declare-spread-primitive "emitted"
+  :params (name)
+  :returns "list"
+  :effects []
+  :doc "Return list of values emitted into nearest matching provider.
+        Empty list if no provider.")

shared/sx/ref/eval.sx

@@ -162,6 +162,7 @@
               (= name "reset")       (sf-reset args env)
               (= name "shift")       (sf-shift args env)
               (= name "dynamic-wind") (sf-dynamic-wind args env)
+              (= name "provide")    (sf-provide args env)
 
               ;; Higher-order forms
               (= name "map")          (ho-map args env)
@@ -949,6 +950,25 @@
         result))))
 
 
+;; --------------------------------------------------------------------------
+;; 6a2. provide — render-time dynamic scope
+;; --------------------------------------------------------------------------
+;;
+;; (provide name value body...) — push a named scope with value and empty
+;; accumulator, evaluate body, pop scope. Returns last body result.
+
+(define sf-provide
+  (fn ((args :as list) (env :as dict))
+    (let ((name (trampoline (eval-expr (first args) env)))
+          (val (trampoline (eval-expr (nth args 1) env)))
+          (body-exprs (slice args 2))
+          (result nil))
+      (provide-push! name val)
+      (for-each (fn (e) (set! result (trampoline (eval-expr e env)))) body-exprs)
+      (provide-pop! name)
+      result)))
+
+
 ;; --------------------------------------------------------------------------
 ;; 6b. Macro expansion
 ;; --------------------------------------------------------------------------

shared/sx/ref/js.sx

@@ -527,6 +527,11 @@
   "collect!" "sxCollect"
   "collected" "sxCollected"
   "clear-collected!" "sxClearCollected"
+  "provide-push!" "providePush"
+  "provide-pop!" "providePop"
+  "context" "sxContext"
+  "emit!" "sxEmit"
+  "emitted" "sxEmitted"
 })
 
 

shared/sx/ref/platform_js.py

@@ -868,6 +868,7 @@ PREAMBLE = '''\
   SxSpread.prototype._spread = true;
 
   var _collectBuckets = {};
+  var _provideStacks = {};
 
   function isSym(x) { return x != null && x._sym === true; }
   function isKw(x) { return x != null && x._kw === true; }
@@ -1087,6 +1088,12 @@ PRIMITIVES_JS_MODULES: dict[str, str] = {
   PRIMITIVES["collect!"] = sxCollect;
   PRIMITIVES["collected"] = sxCollected;
   PRIMITIVES["clear-collected!"] = sxClearCollected;
+  // provide/context/emit! — render-time dynamic scope
+  PRIMITIVES["provide-push!"] = providePush;
+  PRIMITIVES["provide-pop!"] = providePop;
+  PRIMITIVES["context"] = sxContext;
+  PRIMITIVES["emit!"] = sxEmit;
+  PRIMITIVES["emitted"] = sxEmitted;
 ''',
 }
 # Modules to include by default (all)
@@ -1162,6 +1169,35 @@ PLATFORM_JS_PRE = '''
     if (_collectBuckets[bucket]) _collectBuckets[bucket] = [];
   }
 
+  function providePush(name, value) {
+    if (!_provideStacks[name]) _provideStacks[name] = [];
+    _provideStacks[name].push({value: value !== undefined ? value : NIL, emitted: []});
+  }
+  function providePop(name) {
+    if (_provideStacks[name] && _provideStacks[name].length) _provideStacks[name].pop();
+  }
+  function sxContext(name) {
+    if (_provideStacks[name] && _provideStacks[name].length) {
+      return _provideStacks[name][_provideStacks[name].length - 1].value;
+    }
+    if (arguments.length > 1) return arguments[1];
+    throw new Error("No provider for: " + name);
+  }
+  function sxEmit(name, value) {
+    if (_provideStacks[name] && _provideStacks[name].length) {
+      _provideStacks[name][_provideStacks[name].length - 1].emitted.push(value);
+    } else {
+      throw new Error("No provider for emit!: " + name);
+    }
+    return NIL;
+  }
+  function sxEmitted(name) {
+    if (_provideStacks[name] && _provideStacks[name].length) {
+      return _provideStacks[name][_provideStacks[name].length - 1].emitted.slice();
+    }
+    return [];
+  }
+
   function lambdaParams(f) { return f.params; }
   function lambdaBody(f) { return f.body; }
   function lambdaClosure(f) { return f.closure; }
@@ -3192,6 +3228,11 @@ def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has
     api_lines.append('    collect: sxCollect,')
     api_lines.append('    collected: sxCollected,')
     api_lines.append('    clearCollected: sxClearCollected,')
+    api_lines.append('    providePush: providePush,')
+    api_lines.append('    providePop: providePop,')
+    api_lines.append('    context: sxContext,')
+    api_lines.append('    emit: sxEmit,')
+    api_lines.append('    emitted: sxEmitted,')
     api_lines.append(f'    _version: "{version}"')
     api_lines.append('  };')
     api_lines.append('')

shared/sx/ref/platform_py.py

@@ -101,6 +101,46 @@ def _collect_reset():
     _collect_buckets = {}
 
 
+# Render-time dynamic scope stacks (provide/context/emit!)
+_provide_stacks: dict[str, list[dict]] = {}
+
+
+def provide_push(name, value=None):
+    """Push a provider scope with name, value, and empty emitted list."""
+    _provide_stacks.setdefault(name, []).append({"value": value, "emitted": []})
+
+
+def provide_pop(name):
+    """Pop the most recent provider scope for name."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        _provide_stacks[name].pop()
+
+
+def sx_context(name, *default):
+    """Read value from nearest enclosing provider. Error if no provider and no default."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        return _provide_stacks[name][-1]["value"]
+    if default:
+        return default[0]
+    raise RuntimeError(f"No provider for: {name}")
+
+
+def sx_emit(name, value):
+    """Append value to nearest enclosing provider's accumulator. Error if no provider."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        _provide_stacks[name][-1]["emitted"].append(value)
+    else:
+        raise RuntimeError(f"No provider for emit!: {name}")
+    return NIL
+
+
+def sx_emitted(name):
+    """Return list of values emitted into nearest matching provider."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        return list(_provide_stacks[name][-1]["emitted"])
+    return []
+
+
 def sx_truthy(x):
     """SX truthiness: everything is truthy except False, None, and NIL."""
     if x is False:
@@ -942,6 +982,12 @@ PRIMITIVES["spread-attrs"] = spread_attrs
 PRIMITIVES["collect!"] = sx_collect
 PRIMITIVES["collected"] = sx_collected
 PRIMITIVES["clear-collected!"] = sx_clear_collected
+# provide/context/emit! — render-time dynamic scope
+PRIMITIVES["provide-push!"] = provide_push
+PRIMITIVES["provide-pop!"] = provide_pop
+PRIMITIVES["context"] = sx_context
+PRIMITIVES["emit!"] = sx_emit
+PRIMITIVES["emitted"] = sx_emitted
 ''',
 }
 

shared/sx/ref/py.sx

@@ -252,6 +252,11 @@
   "collect!" "sx_collect"
   "collected" "sx_collected"
   "clear-collected!" "sx_clear_collected"
+  "provide-push!" "provide_push"
+  "provide-pop!" "provide_pop"
+  "context" "sx_context"
+  "emit!" "sx_emit"
+  "emitted" "sx_emitted"
 })
 
 

shared/sx/ref/render.sx

@@ -269,6 +269,13 @@
 ;;   (collected bucket)        → list
 ;;   (clear-collected! bucket) → void
 ;;
+;; Dynamic scope (provide/context/emit!):
+;;   (provide-push! name val)  → void
+;;   (provide-pop! name)       → void
+;;   (context name &rest def)  → value from nearest provider
+;;   (emit! name value)        → void (append to provider accumulator)
+;;   (emitted name)            → list of emitted values
+;;
 ;; From parser.sx:
 ;;   (sx-serialize val)        → SX source string (aliased as serialize above)
 ;; --------------------------------------------------------------------------

shared/sx/ref/sx_ref.py

@@ -60,6 +60,46 @@ def _collect_reset():
     _collect_buckets = {}
 
 
+# Render-time dynamic scope stacks (provide/context/emit!)
+_provide_stacks: dict[str, list[dict]] = {}
+
+
+def provide_push(name, value=None):
+    """Push a provider scope with name, value, and empty emitted list."""
+    _provide_stacks.setdefault(name, []).append({"value": value, "emitted": []})
+
+
+def provide_pop(name):
+    """Pop the most recent provider scope for name."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        _provide_stacks[name].pop()
+
+
+def sx_context(name, *default):
+    """Read value from nearest enclosing provider. Error if no provider and no default."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        return _provide_stacks[name][-1]["value"]
+    if default:
+        return default[0]
+    raise RuntimeError(f"No provider for: {name}")
+
+
+def sx_emit(name, value):
+    """Append value to nearest enclosing provider's accumulator. Error if no provider."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        _provide_stacks[name][-1]["emitted"].append(value)
+    else:
+        raise RuntimeError(f"No provider for emit!: {name}")
+    return NIL
+
+
+def sx_emitted(name):
+    """Return list of values emitted into nearest matching provider."""
+    if name in _provide_stacks and _provide_stacks[name]:
+        return list(_provide_stacks[name][-1]["emitted"])
+    return []
+
+
 def sx_truthy(x):
     """SX truthiness: everything is truthy except False, None, and NIL."""
     if x is False:
@@ -905,6 +945,12 @@ PRIMITIVES["spread-attrs"] = spread_attrs
 PRIMITIVES["collect!"] = sx_collect
 PRIMITIVES["collected"] = sx_collected
 PRIMITIVES["clear-collected!"] = sx_clear_collected
+# provide/context/emit! — render-time dynamic scope
+PRIMITIVES["provide-push!"] = provide_push
+PRIMITIVES["provide-pop!"] = provide_pop
+PRIMITIVES["context"] = sx_context
+PRIMITIVES["emit!"] = sx_emit
+PRIMITIVES["emitted"] = sx_emitted
 
 
 def is_primitive(name):
@@ -1349,6 +1395,8 @@ def eval_list(expr, env):
                 return sf_shift(args, env)
             elif sx_truthy((name == 'dynamic-wind')):
                 return sf_dynamic_wind(args, env)
+            elif sx_truthy((name == 'provide')):
+                return sf_provide(args, env)
             elif sx_truthy((name == 'map')):
                 return ho_map(args, env)
             elif sx_truthy((name == 'map-indexed')):
@@ -1840,6 +1888,19 @@ def sf_dynamic_wind(args, env):
     call_thunk(after, env)
     return result
 
+# sf-provide
+def sf_provide(args, env):
+    _cells = {}
+    name = trampoline(eval_expr(first(args), env))
+    val = trampoline(eval_expr(nth(args, 1), env))
+    body_exprs = slice(args, 2)
+    _cells['result'] = NIL
+    provide_push(name, val)
+    for e in body_exprs:
+        _cells['result'] = trampoline(eval_expr(e, env))
+    provide_pop(name)
+    return _cells['result']
+
 # expand-macro
 def expand_macro(mac, raw_args, env):
     local = env_merge(macro_closure(mac), env)
@@ -2189,7 +2250,7 @@ def render_value_to_html(val, env):
         return escape_html(sx_str(val))
 
 # RENDER_HTML_FORMS
-RENDER_HTML_FORMS = ['if', 'when', 'cond', 'case', 'let', 'let*', 'begin', 'do', 'define', 'defcomp', 'defisland', 'defmacro', 'defstyle', 'defhandler', 'deftype', 'defeffect', 'map', 'map-indexed', 'filter', 'for-each']
+RENDER_HTML_FORMS = ['if', 'when', 'cond', 'case', 'let', 'let*', 'begin', 'do', 'define', 'defcomp', 'defisland', 'defmacro', 'defstyle', 'defhandler', 'deftype', 'defeffect', 'map', 'map-indexed', 'filter', 'for-each', 'provide']
 
 # render-html-form?
 def is_render_html_form(name):
@@ -2291,6 +2352,15 @@ def dispatch_html_form(name, expr, env):
         f = trampoline(eval_expr(nth(expr, 1), env))
         coll = trampoline(eval_expr(nth(expr, 2), env))
         return join('', filter(lambda r: (not sx_truthy(is_spread(r))), map(lambda item: (render_lambda_html(f, [item], env) if sx_truthy(is_lambda(f)) else render_to_html(apply(f, [item]), env)), coll)))
+    elif sx_truthy((name == 'provide')):
+        prov_name = trampoline(eval_expr(nth(expr, 1), env))
+        prov_val = trampoline(eval_expr(nth(expr, 2), env))
+        body_start = 3
+        body_count = (len(expr) - 3)
+        provide_push(prov_name, prov_val)
+        result = (render_to_html(nth(expr, body_start), env) if sx_truthy((body_count == 1)) else join('', filter(lambda r: (not sx_truthy(is_spread(r))), map(lambda i: render_to_html(nth(expr, i), env), range(body_start, (body_start + body_count))))))
+        provide_pop(prov_name)
+        return result
     else:
         return render_value_to_html(trampoline(eval_expr(expr, env)), env)
 
@@ -2529,7 +2599,7 @@ def aser_call(name, args, env):
     return sx_str('(', join(' ', parts), ')')
 
 # SPECIAL_FORM_NAMES
-SPECIAL_FORM_NAMES = ['if', 'when', 'cond', 'case', 'and', 'or', 'let', 'let*', 'lambda', 'fn', 'define', 'defcomp', 'defmacro', 'defstyle', 'defhandler', 'defpage', 'defquery', 'defaction', 'defrelation', 'begin', 'do', 'quote', 'quasiquote', '->', 'set!', 'letrec', 'dynamic-wind', 'defisland', 'deftype', 'defeffect']
+SPECIAL_FORM_NAMES = ['if', 'when', 'cond', 'case', 'and', 'or', 'let', 'let*', 'lambda', 'fn', 'define', 'defcomp', 'defmacro', 'defstyle', 'defhandler', 'defpage', 'defquery', 'defaction', 'defrelation', 'begin', 'do', 'quote', 'quasiquote', '->', 'set!', 'letrec', 'dynamic-wind', 'defisland', 'deftype', 'defeffect', 'provide']
 
 # HO_FORM_NAMES
 HO_FORM_NAMES = ['map', 'map-indexed', 'filter', 'reduce', 'some', 'every?', 'for-each']
@@ -2626,6 +2696,15 @@ def aser_special(name, expr, env):
     elif sx_truthy(((name == 'define') if sx_truthy((name == 'define')) else ((name == 'defcomp') if sx_truthy((name == 'defcomp')) else ((name == 'defmacro') if sx_truthy((name == 'defmacro')) else ((name == 'defstyle') if sx_truthy((name == 'defstyle')) else ((name == 'defhandler') if sx_truthy((name == 'defhandler')) else ((name == 'defpage') if sx_truthy((name == 'defpage')) else ((name == 'defquery') if sx_truthy((name == 'defquery')) else ((name == 'defaction') if sx_truthy((name == 'defaction')) else ((name == 'defrelation') if sx_truthy((name == 'defrelation')) else ((name == 'deftype') if sx_truthy((name == 'deftype')) else (name == 'defeffect')))))))))))):
         trampoline(eval_expr(expr, env))
         return NIL
+    elif sx_truthy((name == 'provide')):
+        prov_name = trampoline(eval_expr(first(args), env))
+        prov_val = trampoline(eval_expr(nth(args, 1), env))
+        _cells['result'] = NIL
+        provide_push(prov_name, prov_val)
+        for body in slice(args, 2):
+            _cells['result'] = aser(body, env)
+        provide_pop(prov_name)
+        return _cells['result']
     else:
         return trampoline(eval_expr(expr, env))
 
@@ -3759,7 +3838,7 @@ async def async_map_render(exprs, env, ctx):
     return results
 
 # ASYNC_RENDER_FORMS
-ASYNC_RENDER_FORMS = ['if', 'when', 'cond', 'case', 'let', 'let*', 'begin', 'do', 'define', 'defcomp', 'defisland', 'defmacro', 'defstyle', 'defhandler', 'deftype', 'defeffect', 'map', 'map-indexed', 'filter', 'for-each']
+ASYNC_RENDER_FORMS = ['if', 'when', 'cond', 'case', 'let', 'let*', 'begin', 'do', 'define', 'defcomp', 'defisland', 'defmacro', 'defstyle', 'defhandler', 'deftype', 'defeffect', 'map', 'map-indexed', 'filter', 'for-each', 'provide']
 
 # async-render-form?
 def async_render_form_p(name):
@@ -3823,6 +3902,15 @@ async def dispatch_async_render_form(name, expr, env, ctx):
         f = (await async_eval(nth(expr, 1), env, ctx))
         coll = (await async_eval(nth(expr, 2), env, ctx))
         return join('', filter(lambda r: (not sx_truthy(is_spread(r))), (await async_map_fn_render(f, coll, env, ctx))))
+    elif sx_truthy((name == 'provide')):
+        prov_name = (await async_eval(nth(expr, 1), env, ctx))
+        prov_val = (await async_eval(nth(expr, 2), env, ctx))
+        body_start = 3
+        body_count = (len(expr) - 3)
+        provide_push(prov_name, prov_val)
+        result = ((await async_render(nth(expr, body_start), env, ctx)) if sx_truthy((body_count == 1)) else (lambda results: join('', filter(lambda r: (not sx_truthy(is_spread(r))), results)))((await async_map_render(slice(expr, body_start), env, ctx))))
+        provide_pop(prov_name)
+        return result
     else:
         return (await async_render((await async_eval(expr, env, ctx)), env, ctx))
 
@@ -4148,7 +4236,7 @@ async def async_aser_call(name, args, env, ctx):
     return make_sx_expr(sx_str('(', join(' ', parts), ')'))
 
 # ASYNC_ASER_FORM_NAMES
-ASYNC_ASER_FORM_NAMES = ['if', 'when', 'cond', 'case', 'and', 'or', 'let', 'let*', 'lambda', 'fn', 'define', 'defcomp', 'defmacro', 'defstyle', 'defhandler', 'defpage', 'defquery', 'defaction', 'begin', 'do', 'quote', '->', 'set!', 'defisland', 'deftype', 'defeffect']
+ASYNC_ASER_FORM_NAMES = ['if', 'when', 'cond', 'case', 'and', 'or', 'let', 'let*', 'lambda', 'fn', 'define', 'defcomp', 'defmacro', 'defstyle', 'defhandler', 'defpage', 'defquery', 'defaction', 'begin', 'do', 'quote', '->', 'set!', 'defisland', 'deftype', 'defeffect', 'provide']
 
 # ASYNC_ASER_HO_NAMES
 ASYNC_ASER_HO_NAMES = ['map', 'map-indexed', 'filter', 'for-each']
@@ -4242,6 +4330,15 @@ async def dispatch_async_aser_form(name, expr, env, ctx):
     elif sx_truthy(((name == 'define') if sx_truthy((name == 'define')) else ((name == 'defcomp') if sx_truthy((name == 'defcomp')) else ((name == 'defmacro') if sx_truthy((name == 'defmacro')) else ((name == 'defstyle') if sx_truthy((name == 'defstyle')) else ((name == 'defhandler') if sx_truthy((name == 'defhandler')) else ((name == 'defpage') if sx_truthy((name == 'defpage')) else ((name == 'defquery') if sx_truthy((name == 'defquery')) else ((name == 'defaction') if sx_truthy((name == 'defaction')) else ((name == 'deftype') if sx_truthy((name == 'deftype')) else (name == 'defeffect'))))))))))):
         (await async_eval(expr, env, ctx))
         return NIL
+    elif sx_truthy((name == 'provide')):
+        prov_name = (await async_eval(first(args), env, ctx))
+        prov_val = (await async_eval(nth(args, 1), env, ctx))
+        _cells['result'] = NIL
+        provide_push(prov_name, prov_val)
+        for body in slice(args, 2):
+            _cells['result'] = (await async_aser(body, env, ctx))
+        provide_pop(prov_name)
+        return _cells['result']
     else:
         return (await async_eval(expr, env, ctx))