diff --git a/shared/static/scripts/sx-browser.js b/shared/static/scripts/sx-browser.js
index 23a9e74..c3b8379 100644
--- a/shared/static/scripts/sx-browser.js
+++ b/shared/static/scripts/sx-browser.js
@@ -14,7 +14,7 @@
   // =========================================================================
 
   var NIL = Object.freeze({ _nil: true, toString: function() { return "nil"; } });
-  var SX_VERSION = "2026-03-14T01:00:32Z";
+  var SX_VERSION = "2026-03-14T01:23:35Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
@@ -1391,7 +1391,7 @@ var d2 = hexDigitValue(nth(source, pos));
 var _ = (pos = (pos + 1));
 var d3 = hexDigitValue(nth(source, pos));
 var _ = (pos = (pos + 1));
-buf = (String(buf) + String(charFromCode(((((d0 * 4096) + (d1 * 256)) + (d2 * 16)) + d3))));
+buf = (String(buf) + String(charFromCode((d0 * 4096))));
 continue; } } else { buf = (String(buf) + String((isSxTruthy((esc == "n")) ? "\n" : (isSxTruthy((esc == "t")) ? "\t" : (isSxTruthy((esc == "r")) ? "\r" : esc)))));
 pos = (pos + 1);
 continue; } } } else { buf = (String(buf) + String(ch));
@@ -6442,87 +6442,6 @@ return forEach(function(d) { return invoke(d); }, subDisposers); });
   };
 
 
-  // =========================================================================
-  // Extension: Delimited continuations (shift/reset)
-  // =========================================================================
-
-  function Continuation(fn) { this.fn = fn; }
-  Continuation.prototype._continuation = true;
-  Continuation.prototype.call = function(value) { return this.fn(value !== undefined ? value : NIL); };
-
-  function ShiftSignal(kName, body, env) {
-    this.kName = kName;
-    this.body = body;
-    this.env = env;
-  }
-
-  PRIMITIVES["continuation?"] = function(x) { return x != null && x._continuation === true; };
-
-  var _resetResume = [];
-
-  function sfReset(args, env) {
-    var body = args[0];
-    try {
-      return trampoline(evalExpr(body, env));
-    } catch (e) {
-      if (e instanceof ShiftSignal) {
-        var sig = e;
-        var cont = new Continuation(function(value) {
-          if (value === undefined) value = NIL;
-          _resetResume.push(value);
-          try {
-            return trampoline(evalExpr(body, env));
-          } finally {
-            _resetResume.pop();
-          }
-        });
-        var sigEnv = merge(sig.env);
-        sigEnv[sig.kName] = cont;
-        return trampoline(evalExpr(sig.body, sigEnv));
-      }
-      throw e;
-    }
-  }
-
-  function sfShift(args, env) {
-    if (_resetResume.length > 0) {
-      return _resetResume[_resetResume.length - 1];
-    }
-    var kName = symbolName(args[0]);
-    var body = args[1];
-    throw new ShiftSignal(kName, body, env);
-  }
-
-  // Wrap evalList to intercept reset/shift
-  var _baseEvalList = evalList;
-  evalList = function(expr, env) {
-    var head = expr[0];
-    if (isSym(head)) {
-      var name = head.name;
-      if (name === "reset") return sfReset(expr.slice(1), env);
-      if (name === "shift") return sfShift(expr.slice(1), env);
-    }
-    return _baseEvalList(expr, env);
-  };
-
-  // Wrap aserSpecial to handle reset/shift in SX wire mode
-  if (typeof aserSpecial === "function") {
-    var _baseAserSpecial = aserSpecial;
-    aserSpecial = function(name, expr, env) {
-      if (name === "reset") return sfReset(expr.slice(1), env);
-      if (name === "shift") return sfShift(expr.slice(1), env);
-      return _baseAserSpecial(name, expr, env);
-    };
-  }
-
-  // Wrap typeOf to recognize continuations
-  var _baseTypeOf = typeOf;
-  typeOf = function(x) {
-    if (x != null && x._continuation) return "continuation";
-    return _baseTypeOf(x);
-  };
-
-
   // =========================================================================
   // Async IO: Promise-aware rendering for client-side IO primitives
   // =========================================================================
@@ -7320,6 +7239,14 @@ return forEach(function(d) { return invoke(d); }, subDisposers); });
     context: sxContext,
     emit: sxEmit,
     emitted: sxEmitted,
+    cekRun: cekRun,
+    makeCekState: makeCekState,
+    makeCekValue: makeCekValue,
+    cekStep: cekStep,
+    cekTerminal: cekTerminal_p,
+    cekValue: cekValue,
+    makeReactiveResetFrame: makeReactiveResetFrame,
+    evalExpr: evalExpr,
     _version: "ref-2.0 (boot+dom+engine+html+orchestration+parser+sx, bootstrap-compiled)"
   };
 
diff --git a/shared/sx/ref/platform_js.py b/shared/sx/ref/platform_js.py
index 013cf71..f606d20 100644
--- a/shared/sx/ref/platform_js.py
+++ b/shared/sx/ref/platform_js.py
@@ -3076,7 +3076,7 @@ def fixups_js(has_html, has_sx, has_dom, has_signals=False, has_deps=False, has_
     return "\n".join(lines)
 
 
-def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has_parser, adapter_label, has_deps=False, has_router=False, has_signals=False, has_page_helpers=False):
+def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has_parser, adapter_label, has_deps=False, has_router=False, has_signals=False, has_page_helpers=False, has_cek=False):
     # Parser: use compiled sxParse from parser.sx, or inline a minimal fallback
     if has_parser:
         parser = '''
@@ -3272,6 +3272,15 @@ def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has
     api_lines.append('    context: sxContext,')
     api_lines.append('    emit: sxEmit,')
     api_lines.append('    emitted: sxEmitted,')
+    if has_cek:
+        api_lines.append('    cekRun: cekRun,')
+        api_lines.append('    makeCekState: makeCekState,')
+        api_lines.append('    makeCekValue: makeCekValue,')
+        api_lines.append('    cekStep: cekStep,')
+        api_lines.append('    cekTerminal: cekTerminal_p,')
+        api_lines.append('    cekValue: cekValue,')
+        api_lines.append('    makeReactiveResetFrame: makeReactiveResetFrame,')
+        api_lines.append('    evalExpr: evalExpr,')
     api_lines.append(f'    _version: "{version}"')
     api_lines.append('  };')
     api_lines.append('')
diff --git a/shared/sx/ref/run_js_sx.py b/shared/sx/ref/run_js_sx.py
index 9edfa24..50cbaf9 100644
--- a/shared/sx/ref/run_js_sx.py
+++ b/shared/sx/ref/run_js_sx.py
@@ -226,7 +226,7 @@ def compile_ref_to_js(
         parts.append(CONTINUATIONS_JS)
     if has_dom:
         parts.append(ASYNC_IO_JS)
-    parts.append(public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has_parser, adapter_label, has_deps, has_router, has_signals, has_page_helpers))
+    parts.append(public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_boot, has_parser, adapter_label, has_deps, has_router, has_signals, has_page_helpers, has_cek))
     parts.append(EPILOGUE)
 
     build_ts = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
diff --git a/sx/sx/geography/cek.sx b/sx/sx/geography/cek.sx
new file mode 100644
index 0000000..a723d6a
--- /dev/null
+++ b/sx/sx/geography/cek.sx
@@ -0,0 +1,195 @@
+;; ---------------------------------------------------------------------------
+;; CEK Machine — Geography section
+;; ---------------------------------------------------------------------------
+
+
+;; ---------------------------------------------------------------------------
+;; Island demos
+;; ---------------------------------------------------------------------------
+
+;; Counter: signal + deref in text position
+(defisland ~geography/cek/demo-counter (&key initial)
+  (let ((count (signal (or initial 0)))
+        (doubled (computed (fn () (* 2 (deref count))))))
+    (div :class "rounded-lg border border-stone-200 p-4 space-y-2"
+      (div :class "flex items-center gap-3"
+        (button :class "px-3 py-1 rounded bg-violet-600 text-white text-sm"
+          :on-click (fn (e) (swap! count dec)) "-")
+        (span :class "text-2xl font-bold text-violet-700 min-w-[3ch] text-center"
+          (deref count))
+        (button :class "px-3 py-1 rounded bg-violet-600 text-white text-sm"
+          :on-click (fn (e) (swap! count inc)) "+"))
+      (p :class "text-sm text-stone-500"
+        (str "doubled: " (deref doubled))))))
+
+;; Computed chain: base -> doubled -> quadrupled
+(defisland ~geography/cek/demo-chain ()
+  (let ((base (signal 1))
+        (doubled (computed (fn () (* (deref base) 2))))
+        (quadrupled (computed (fn () (* (deref doubled) 2)))))
+    (div :class "rounded-lg border border-stone-200 p-4 space-y-2"
+      (div :class "flex items-center gap-3"
+        (button :class "px-3 py-1 rounded bg-violet-600 text-white text-sm"
+          :on-click (fn (e) (swap! base dec)) "-")
+        (span :class "text-2xl font-bold text-violet-700 min-w-[3ch] text-center"
+          (deref base))
+        (button :class "px-3 py-1 rounded bg-violet-600 text-white text-sm"
+          :on-click (fn (e) (swap! base inc)) "+"))
+      (p :class "text-sm text-stone-500"
+        (str "doubled: " (deref doubled) "  |  quadrupled: " (deref quadrupled))))))
+
+;; Reactive attribute: (deref sig) in :class position
+(defisland ~geography/cek/demo-reactive-attr ()
+  (let ((danger (signal false)))
+    (div :class "rounded-lg border border-stone-200 p-4 space-y-3"
+      (button :class "px-3 py-1 rounded bg-violet-600 text-white text-sm"
+        :on-click (fn (e) (swap! danger not))
+        (if (deref danger) "Safe mode" "Danger mode"))
+      (div :class (str "p-3 rounded font-medium transition-colors "
+                       (if (deref danger)
+                         "bg-red-100 text-red-800"
+                         "bg-green-100 text-green-800"))
+        (if (deref danger)
+          "DANGER: reactive class binding via CEK"
+          "SAFE: reactive class binding via CEK")))))
+
+;; Stopwatch: effect + cleanup
+(defisland ~geography/cek/demo-stopwatch ()
+  (let ((running (signal false))
+        (elapsed (signal 0))
+        (time-text (create-text-node "0.0s"))
+        (btn-text (create-text-node "Start")))
+    (effect (fn ()
+      (when (deref running)
+        (let ((id (set-interval (fn () (swap! elapsed inc)) 100)))
+          (fn () (clear-interval id))))))
+    (effect (fn ()
+      (let ((e (deref elapsed)))
+        (dom-set-text-content time-text
+          (str (floor (/ e 10)) "." (mod e 10) "s")))))
+    (effect (fn ()
+      (dom-set-text-content btn-text
+        (if (deref running) "Stop" "Start"))))
+    (div :class "rounded-lg border border-stone-200 p-4"
+      (div :class "flex items-center gap-3"
+        (span :class "text-2xl font-bold text-violet-700 font-mono min-w-[5ch]" time-text)
+        (button :class "px-3 py-1 rounded bg-violet-600 text-white text-sm"
+          :on-click (fn (e) (swap! running not)) btn-text)
+        (button :class "px-3 py-1 rounded bg-stone-400 text-white text-sm"
+          :on-click (fn (e) (reset! running false) (reset! elapsed 0)) "Reset")))))
+
+;; Batch: two signals, one notification
+(defisland ~geography/cek/demo-batch ()
+  (let ((first-sig  (signal 0))
+        (second-sig (signal 0))
+        (renders    (signal 0)))
+    (effect (fn ()
+      (deref first-sig) (deref second-sig)
+      (swap! renders inc)))
+    (div :class "rounded-lg border border-stone-200 p-4 space-y-2"
+      (div :class "flex items-center gap-4 text-sm"
+        (span (str "first: " (deref first-sig)))
+        (span (str "second: " (deref second-sig)))
+        (span :class "px-2 py-0.5 rounded bg-green-100 text-green-800 text-xs font-semibold"
+          (str "renders: " (deref renders))))
+      (div :class "flex items-center gap-2"
+        (button :class "px-3 py-1 rounded bg-violet-600 text-white text-sm"
+          :on-click (fn (e)
+            (batch (fn ()
+              (swap! first-sig inc)
+              (swap! second-sig inc))))
+          "Batch +1")
+        (button :class "px-3 py-1 rounded bg-stone-400 text-white text-sm"
+          :on-click (fn (e)
+            (swap! first-sig inc)
+            (swap! second-sig inc))
+          "No-batch +1")))))
+
+
+;; ---------------------------------------------------------------------------
+;; Overview page content
+;; ---------------------------------------------------------------------------
+
+(defcomp ~geography/cek/cek-content ()
+  (~docs/page :title "CEK Machine"
+
+    (~docs/section :title "Three registers" :id "registers"
+      (p "The CEK machine makes evaluation explicit. Every step is a pure function from state to state:")
+      (ul :class "space-y-1 text-stone-600 list-disc pl-5"
+        (li (strong "C") "ontrol — the expression being evaluated")
+        (li (strong "E") "nvironment — the bindings in scope")
+        (li (strong "K") "ontinuation — what to do with the result"))
+      (p "The tree-walk evaluator uses the same three things, but hides them in the call stack. The CEK makes them " (em "data") " — inspectable, serializable, capturable."))
+
+    (~docs/section :title "Why it matters" :id "why"
+      (p "Making the continuation explicit enables:")
+      (ul :class "space-y-1 text-stone-600 list-disc pl-5"
+        (li (strong "Stepping") " — pause evaluation, inspect state, resume")
+        (li (strong "Serialization") " — save a computation mid-flight, restore later")
+        (li (strong "Delimited continuations") " — " (code "shift") "/" (code "reset") " capture \"the rest of this expression\" as a value")
+        (li (strong "Deref-as-shift") " — " (code "(deref sig)") " inside a reactive boundary captures the continuation as the subscriber")))
+
+    (~docs/section :title "Default evaluator" :id "default"
+      (p "CEK is the default evaluator on both client (JS) and server (Python). Every " (code "eval-expr") " call goes through " (code "cek-run") ". The tree-walk evaluator is preserved as " (code "_tree_walk_eval_expr") " for test runners that interpret " (code ".sx") " files.")
+      (p "The CEK is defined in two spec files:")
+      (ul :class "space-y-1 text-stone-600 list-disc pl-5"
+        (li (code "frames.sx") " — frame types (IfFrame, ArgFrame, ResetFrame, ReactiveResetFrame, ...)")
+        (li (code "cek.sx") " — step function, run loop, special form handlers, continuation operations")))
+
+    (~docs/section :title "Deref as shift" :id "deref-as-shift"
+      (p "The reactive payoff. When " (code "(deref sig)") " encounters a signal inside a " (code "reactive-reset") " boundary:")
+      (ol :class "space-y-1 text-stone-600 list-decimal pl-5"
+        (li (strong "Shift") " — capture all frames between here and the reactive-reset")
+        (li (strong "Subscribe") " — register the captured continuation as a signal subscriber")
+        (li (strong "Return") " — flow the current signal value through the rest of the expression"))
+      (p "When the signal changes, the captured continuation is re-invoked with the new value. The " (code "update-fn") " on the ReactiveResetFrame mutates the DOM. No explicit " (code "effect()") " wrapping needed.")
+      (~docs/code :code (highlight
+        ";; User writes:\n(div :class (str \"count-\" (deref counter))\n  (str \"Value: \" (deref counter)))\n\n;; CEK sees (deref counter) → signal? → reactive-reset on stack?\n;; Yes: capture (str \"count-\" [HOLE]) as continuation\n;; Register as subscriber. Return current value.\n;; When counter changes: re-invoke continuation → update DOM."
+        "lisp")))))
+
+
+;; ---------------------------------------------------------------------------
+;; Demo page content
+;; ---------------------------------------------------------------------------
+
+(defcomp ~geography/cek/cek-demo-content ()
+  (~docs/page :title "CEK Demo"
+
+    (~docs/section :title "What this demonstrates" :id "what"
+      (p "These are " (strong "live islands") " evaluated by the CEK machine. Every " (code "eval-expr") " goes through " (code "cek-run") ". Every " (code "(deref sig)") " in an island creates a reactive DOM binding via continuation frames.")
+      (p "The CEK machine is defined in " (code "cek.sx") " (160 lines) and " (code "frames.sx") " (100 lines) — pure s-expressions, bootstrapped to both JavaScript and Python."))
+
+    (~docs/section :title "1. Counter" :id "demo-counter"
+      (p (code "(deref count)") " in text position creates a reactive text node. " (code "(deref doubled)") " is a computed that updates when count changes.")
+      (~geography/cek/demo-counter :initial 0)
+      (~docs/code :code (highlight
+        "(defisland ~demo-counter (&key initial)\n  (let ((count (signal (or initial 0)))\n        (doubled (computed (fn () (* 2 (deref count))))))\n    (div\n      (button :on-click (fn (e) (swap! count dec)) \"-\")\n      (span (deref count))\n      (button :on-click (fn (e) (swap! count inc)) \"+\")\n      (p (str \"doubled: \" (deref doubled))))))"
+        "lisp")))
+
+    (~docs/section :title "2. Computed chain" :id "demo-chain"
+      (p "Three levels of computed: base -> doubled -> quadrupled. Change base, all propagate.")
+      (~geography/cek/demo-chain)
+      (~docs/code :code (highlight
+        "(let ((base (signal 1))\n      (doubled (computed (fn () (* (deref base) 2))))\n      (quadrupled (computed (fn () (* (deref doubled) 2)))))\n  (span (deref base))\n  (p (str \"doubled: \" (deref doubled)\n         \"  |  quadrupled: \" (deref quadrupled))))"
+        "lisp")))
+
+    (~docs/section :title "3. Reactive attributes" :id "demo-attr"
+      (p (code "(deref sig)") " in " (code ":class") " position. The CEK evaluates the " (code "str") " expression, and when the signal changes, the continuation re-evaluates and updates the attribute.")
+      (~geography/cek/demo-reactive-attr)
+      (~docs/code :code (highlight
+        "(div :class (str \"p-3 rounded font-medium \"\n             (if (deref danger)\n               \"bg-red-100 text-red-800\"\n               \"bg-green-100 text-green-800\"))\n  (if (deref danger) \"DANGER\" \"SAFE\"))"
+        "lisp")))
+
+    (~docs/section :title "4. Effect + cleanup" :id "demo-stopwatch"
+      (p "Effects still work through CEK. This stopwatch uses " (code "effect") " with cleanup — toggling the signal clears the interval.")
+      (~geography/cek/demo-stopwatch)
+      (~docs/code :code (highlight
+        "(effect (fn ()\n  (when (deref running)\n    (let ((id (set-interval (fn () (swap! elapsed inc)) 100)))\n      (fn () (clear-interval id))))))"
+        "lisp")))
+
+    (~docs/section :title "5. Batch coalescing" :id "demo-batch"
+      (p "Two signals updated in " (code "batch") " — one notification cycle. Compare render counts between batch and no-batch.")
+      (~geography/cek/demo-batch)
+      (~docs/code :code (highlight
+        "(batch (fn ()\n  (swap! first-sig inc)\n  (swap! second-sig inc)))\n;; One render pass, not two."
+        "lisp")))))
diff --git a/sx/sx/nav-data.sx b/sx/sx/nav-data.sx
index 6115c5c..ea4458b 100644
--- a/sx/sx/nav-data.sx
+++ b/sx/sx/nav-data.sx
@@ -166,6 +166,12 @@
   (dict :label "Optimistic" :href "/sx/(geography.(isomorphism.optimistic))")
   (dict :label "Offline" :href "/sx/(geography.(isomorphism.offline))")))
 
+(define cek-nav-items (list
+  (dict :label "Overview" :href "/sx/(geography.(cek))"
+        :summary "The CEK machine — explicit evaluator with Control, Environment, Kontinuation. Three registers, pure step function.")
+  (dict :label "Demo" :href "/sx/(geography.(cek.demo))"
+        :summary "Live islands evaluated by the CEK machine. Counter, computed chains, reactive attributes — all through explicit continuation frames.")))
+
 (define plans-nav-items (list
   (dict :label "Status" :href "/sx/(etc.(plan.status))"
         :summary "Audit of all plans — what's done, what's in progress, and what remains.")
@@ -384,7 +390,8 @@
           :summary "Child-to-parent communication across render boundaries — spread, collect!, reactive-spread, built on scopes."}
         {:label "Marshes" :href "/sx/(geography.(marshes))"
           :summary "Where reactivity and hypermedia interpenetrate — server writes to signals, reactive transforms reshape server content, client state modifies how hypermedia is interpreted."}
-        {:label "Isomorphism" :href "/sx/(geography.(isomorphism))" :children isomorphism-nav-items})}
+        {:label "Isomorphism" :href "/sx/(geography.(isomorphism))" :children isomorphism-nav-items}
+        {:label "CEK Machine" :href "/sx/(geography.(cek))" :children cek-nav-items})}
      {:label "Language" :href "/sx/(language)"
       :children (list
         {:label "Docs" :href "/sx/(language.(doc))" :children docs-nav-items}
diff --git a/sx/sxc/pages/docs.sx b/sx/sxc/pages/docs.sx
index 45574b4..c0aa01e 100644
--- a/sx/sxc/pages/docs.sx
+++ b/sx/sxc/pages/docs.sx
@@ -650,6 +650,25 @@
   :layout :sx-docs
   :content (~layouts/doc :path "/sx/(geography.(marshes))" (~reactive-islands/marshes/reactive-islands-marshes-content)))
 
+;; ---------------------------------------------------------------------------
+;; CEK Machine section (under Geography)
+;; ---------------------------------------------------------------------------
+
+(defpage cek-index
+  :path "/geography/cek/"
+  :auth :public
+  :layout :sx-docs
+  :content (~layouts/doc :path "/sx/(geography.(cek))" (~geography/cek/cek-content)))
+
+(defpage cek-page
+  :path "/geography/cek/<slug>"
+  :auth :public
+  :layout :sx-docs
+  :content (~layouts/doc :path (str "/sx/(geography.(cek." slug "))")
+    (case slug
+      "demo" (~geography/cek/cek-demo-content)
+      :else (~geography/cek/cek-content))))
+
 ;; ---------------------------------------------------------------------------
 ;; Bootstrapped page helpers demo
 ;; ---------------------------------------------------------------------------
diff --git a/sx/sxc/pages/sx_router.py b/sx/sxc/pages/sx_router.py
index 883489d..bf13bc8 100644
--- a/sx/sxc/pages/sx_router.py
+++ b/sx/sxc/pages/sx_router.py
@@ -267,6 +267,8 @@ _REDIRECT_PATTERNS = [
      lambda m: f"/sx/(geography.(reactive.{m.group(1)}))"),
     (re.compile(r"^/geography/isomorphism/(.+?)/?$"),
      lambda m: f"/sx/(geography.(isomorphism.{m.group(1)}))"),
+    (re.compile(r"^/geography/cek/(.+?)/?$"),
+     lambda m: f"/sx/(geography.(cek.{m.group(1)}))"),
     (re.compile(r"^/geography/spreads/?$"),
      "/sx/(geography.(spreads))"),
     (re.compile(r"^/geography/marshes/?$"),
@@ -290,6 +292,7 @@ _REDIRECT_PATTERNS = [
     (re.compile(r"^/geography/hypermedia/?$"), "/sx/(geography.(hypermedia))"),
     (re.compile(r"^/geography/reactive/?$"), "/sx/(geography.(reactive))"),
     (re.compile(r"^/geography/isomorphism/?$"), "/sx/(geography.(isomorphism))"),
+    (re.compile(r"^/geography/cek/?$"), "/sx/(geography.(cek))"),
     (re.compile(r"^/geography/?$"), "/sx/(geography)"),
     (re.compile(r"^/applications/cssx/?$"), "/sx/(applications.(cssx))"),
     (re.compile(r"^/applications/protocols/?$"), "/sx/(applications.(protocol))"),