diff --git a/shared/static/scripts/sx-browser.js b/shared/static/scripts/sx-browser.js
index 48da949..7b969d9 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 = "2026-03-11T22:53:48Z";
+  var SX_VERSION = "2026-03-11T23:22:03Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
diff --git a/shared/sx/ref/adapter-async.sx b/shared/sx/ref/adapter-async.sx
index 09803f3..0922111 100644
--- a/shared/sx/ref/adapter-async.sx
+++ b/shared/sx/ref/adapter-async.sx
@@ -40,7 +40,7 @@
 ;; Async HTML renderer
 ;; --------------------------------------------------------------------------
 
-(define-async async-render
+(define-async async-render :effects [render io]
   (fn (expr (env :as dict) ctx)
     (case (type-of expr)
       "nil"      ""
@@ -56,7 +56,7 @@
       :else      (escape-html (str expr)))))
 
 
-(define-async async-render-list
+(define-async async-render-list :effects [render io]
   (fn (expr (env :as dict) ctx)
     (let ((head (first expr)))
       (if (not (= (type-of head) "symbol"))
@@ -138,7 +138,7 @@
 ;; async-render-raw — handle (raw! ...) in async context
 ;; --------------------------------------------------------------------------
 
-(define-async async-render-raw
+(define-async async-render-raw :effects [render io]
   (fn ((args :as list) (env :as dict) ctx)
     (let ((parts (list)))
       (for-each
@@ -157,7 +157,7 @@
 ;; async-render-element — render an HTML element with async arg evaluation
 ;; --------------------------------------------------------------------------
 
-(define-async async-render-element
+(define-async async-render-element :effects [render io]
   (fn ((tag :as string) (args :as list) (env :as dict) ctx)
     (let ((attrs (dict))
           (children (list)))
@@ -185,7 +185,7 @@
 ;; Uses for-each + mutable state instead of reduce, because the bootstrapper
 ;; compiles inline for-each lambdas as for loops (which can contain await).
 
-(define-async async-parse-element-args
+(define-async async-parse-element-args :effects [render io]
   (fn ((args :as list) (attrs :as dict) (children :as list) (env :as dict) ctx)
     (let ((skip false)
           (i 0))
@@ -210,7 +210,7 @@
 ;; async-render-component — expand and render a component asynchronously
 ;; --------------------------------------------------------------------------
 
-(define-async async-render-component
+(define-async async-render-component :effects [render io]
   (fn ((comp :as component) (args :as list) (env :as dict) ctx)
     (let ((kwargs (dict))
           (children (list)))
@@ -232,7 +232,7 @@
 ;; async-render-island — SSR render of reactive island with hydration markers
 ;; --------------------------------------------------------------------------
 
-(define-async async-render-island
+(define-async async-render-island :effects [render io]
   (fn ((island :as island) (args :as list) (env :as dict) ctx)
     (let ((kwargs (dict))
           (children (list)))
@@ -261,7 +261,7 @@
 ;; async-render-lambda — render lambda body in HTML context
 ;; --------------------------------------------------------------------------
 
-(define-async async-render-lambda
+(define-async async-render-lambda :effects [render io]
   (fn ((f :as lambda) (args :as list) (env :as dict) ctx)
     (let ((local (env-merge (lambda-closure f) env)))
       (for-each-indexed
@@ -274,7 +274,7 @@
 ;; async-parse-kw-args — parse keyword args and children with async eval
 ;; --------------------------------------------------------------------------
 
-(define-async async-parse-kw-args
+(define-async async-parse-kw-args :effects [render io]
   (fn ((args :as list) (kwargs :as dict) (children :as list) (env :as dict) ctx)
     (let ((skip false)
           (i 0))
@@ -300,7 +300,7 @@
 ;; --------------------------------------------------------------------------
 ;; Bootstrapper emits this as: [await async_render(x, env, ctx) for x in exprs]
 
-(define-async async-map-render
+(define-async async-map-render :effects [render io]
   (fn ((exprs :as list) (env :as dict) ctx)
     (let ((results (list)))
       (for-each
@@ -319,7 +319,7 @@
         "deftype" "defeffect"
         "map" "map-indexed" "filter" "for-each"))
 
-(define async-render-form?
+(define async-render-form? :effects []
   (fn ((name :as string))
     (contains? ASYNC_RENDER_FORMS name)))
 
@@ -331,7 +331,7 @@
 ;; Uses cond-scheme? from eval.sx (the FIXED version with every? check)
 ;; and eval-cond from render.sx for correct scheme/clojure classification.
 
-(define-async dispatch-async-render-form
+(define-async dispatch-async-render-form :effects [render io]
   (fn ((name :as string) expr (env :as dict) ctx)
     (cond
       ;; if
@@ -407,7 +407,7 @@
 ;; async-render-cond-scheme — scheme-style cond for render mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-render-cond-scheme
+(define-async async-render-cond-scheme :effects [render io]
   (fn ((clauses :as list) (env :as dict) ctx)
     (if (empty? clauses)
       ""
@@ -429,7 +429,7 @@
 ;; async-render-cond-clojure — clojure-style cond for render mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-render-cond-clojure
+(define-async async-render-cond-clojure :effects [render io]
   (fn ((clauses :as list) (env :as dict) ctx)
     (if (< (len clauses) 2)
       ""
@@ -449,7 +449,7 @@
 ;; async-process-bindings — evaluate let-bindings asynchronously
 ;; --------------------------------------------------------------------------
 
-(define-async async-process-bindings
+(define-async async-process-bindings :effects [render io]
   (fn (bindings (env :as dict) ctx)
     ;; env-extend (not merge) — Env is not a dict subclass, so merge()
     ;; returns an empty dict, losing all parent scope bindings.
@@ -470,7 +470,7 @@
       local)))
 
 
-(define-async async-process-bindings-flat
+(define-async async-process-bindings-flat :effects [render io]
   (fn ((bindings :as list) (local :as dict) ctx)
     (let ((skip false)
           (i 0))
@@ -495,7 +495,7 @@
 ;; async-map-fn-render — map a lambda/callable over collection for render
 ;; --------------------------------------------------------------------------
 
-(define-async async-map-fn-render
+(define-async async-map-fn-render :effects [render io]
   (fn (f (coll :as list) (env :as dict) ctx)
     (let ((results (list)))
       (for-each
@@ -512,7 +512,7 @@
 ;; async-map-indexed-fn-render — map-indexed variant for render
 ;; --------------------------------------------------------------------------
 
-(define-async async-map-indexed-fn-render
+(define-async async-map-indexed-fn-render :effects [render io]
   (fn (f (coll :as list) (env :as dict) ctx)
     (let ((results (list))
           (i 0))
@@ -531,7 +531,7 @@
 ;; async-invoke — call a native callable, await if coroutine
 ;; --------------------------------------------------------------------------
 
-(define-async async-invoke
+(define-async async-invoke :effects [io]
   (fn (f &rest args)
     (let ((r (apply f args)))
       (if (async-coroutine? r)
@@ -543,7 +543,7 @@
 ;; Async SX wire format (aser)
 ;; ==========================================================================
 
-(define-async async-aser
+(define-async async-aser :effects [render io]
   (fn (expr (env :as dict) ctx)
     (case (type-of expr)
       "number"  expr
@@ -573,7 +573,7 @@
       :else expr)))
 
 
-(define-async async-aser-dict
+(define-async async-aser-dict :effects [render io]
   (fn ((expr :as dict) (env :as dict) ctx)
     (let ((result (dict)))
       (for-each
@@ -587,7 +587,7 @@
 ;; async-aser-list — dispatch on list head for aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-list
+(define-async async-aser-list :effects [render io]
   (fn (expr (env :as dict) ctx)
     (let ((head (first expr))
           (args (rest expr)))
@@ -666,7 +666,7 @@
 ;; async-aser-eval-call — evaluate a function call fully in aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-eval-call
+(define-async async-aser-eval-call :effects [render io]
   (fn (head (args :as list) (env :as dict) ctx)
     (let ((f (async-eval head env ctx))
           (evaled-args (async-eval-args args env ctx)))
@@ -694,7 +694,7 @@
 ;; async-eval-args — evaluate a list of args asynchronously
 ;; --------------------------------------------------------------------------
 
-(define-async async-eval-args
+(define-async async-eval-args :effects [io]
   (fn ((args :as list) (env :as dict) ctx)
     (let ((results (list)))
       (for-each
@@ -707,7 +707,7 @@
 ;; async-aser-map-list — aser each element of a list
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-map-list
+(define-async async-aser-map-list :effects [render io]
   (fn ((exprs :as list) (env :as dict) ctx)
     (let ((results (list)))
       (for-each
@@ -720,7 +720,7 @@
 ;; async-aser-fragment — serialize (<> child1 child2 ...) in aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-fragment
+(define-async async-aser-fragment :effects [render io]
   (fn ((children :as list) (env :as dict) ctx)
     (let ((parts (list)))
       (for-each
@@ -744,7 +744,7 @@
 ;; async-aser-component — expand component server-side in aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-component
+(define-async async-aser-component :effects [render io]
   (fn ((comp :as component) (args :as list) (env :as dict) ctx)
     (let ((kwargs (dict))
           (children (list)))
@@ -776,7 +776,7 @@
 ;; async-parse-aser-kw-args — parse keyword args for aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-parse-aser-kw-args
+(define-async async-parse-aser-kw-args :effects [render io]
   (fn ((args :as list) (kwargs :as dict) (children :as list) (env :as dict) ctx)
     (let ((skip false)
           (i 0))
@@ -801,7 +801,7 @@
 ;; async-aser-call — serialize an SX call (tag or component) in aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-call
+(define-async async-aser-call :effects [render io]
   (fn ((name :as string) (args :as list) (env :as dict) ctx)
     (let ((token (if (or (= name "svg") (= name "math"))
                    (svg-context-set! true)
@@ -860,7 +860,7 @@
 (define ASYNC_ASER_HO_NAMES
   (list "map" "map-indexed" "filter" "for-each"))
 
-(define async-aser-form?
+(define async-aser-form? :effects []
   (fn ((name :as string))
     (or (contains? ASYNC_ASER_FORM_NAMES name)
         (contains? ASYNC_ASER_HO_NAMES name))))
@@ -872,7 +872,7 @@
 ;;
 ;; Uses cond-scheme? from eval.sx (the FIXED version with every? check).
 
-(define-async dispatch-async-aser-form
+(define-async dispatch-async-aser-form :effects [render io]
   (fn ((name :as string) expr (env :as dict) ctx)
     (let ((args (rest expr)))
       (cond
@@ -1002,7 +1002,7 @@
 ;; async-aser-cond-scheme — scheme-style cond for aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-cond-scheme
+(define-async async-aser-cond-scheme :effects [render io]
   (fn ((clauses :as list) (env :as dict) ctx)
     (if (empty? clauses)
       nil
@@ -1024,7 +1024,7 @@
 ;; async-aser-cond-clojure — clojure-style cond for aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-cond-clojure
+(define-async async-aser-cond-clojure :effects [render io]
   (fn ((clauses :as list) (env :as dict) ctx)
     (if (< (len clauses) 2)
       nil
@@ -1044,7 +1044,7 @@
 ;; async-aser-case-loop — case dispatch for aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-case-loop
+(define-async async-aser-case-loop :effects [render io]
   (fn (match-val (clauses :as list) (env :as dict) ctx)
     (if (< (len clauses) 2)
       nil
@@ -1064,7 +1064,7 @@
 ;; async-aser-thread-first — -> form in aser mode
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-thread-first
+(define-async async-aser-thread-first :effects [render io]
   (fn ((args :as list) (env :as dict) ctx)
     (let ((result (async-eval (first args) env ctx)))
       (for-each
@@ -1084,7 +1084,7 @@
 ;; async-invoke-or-lambda — invoke a callable or lambda with args
 ;; --------------------------------------------------------------------------
 
-(define-async async-invoke-or-lambda
+(define-async async-invoke-or-lambda :effects [render io]
   (fn (f (args :as list) (env :as dict) ctx)
     (cond
       (and (callable? f) (not (lambda? f)) (not (component? f)))
@@ -1106,7 +1106,7 @@
 ;; Async aser HO forms (map, map-indexed, for-each)
 ;; --------------------------------------------------------------------------
 
-(define-async async-aser-ho-map
+(define-async async-aser-ho-map :effects [render io]
   (fn ((args :as list) (env :as dict) ctx)
     (let ((f (async-eval (first args) env ctx))
           (coll (async-eval (nth args 1) env ctx))
@@ -1122,7 +1122,7 @@
       results)))
 
 
-(define-async async-aser-ho-map-indexed
+(define-async async-aser-ho-map-indexed :effects [render io]
   (fn ((args :as list) (env :as dict) ctx)
     (let ((f (async-eval (first args) env ctx))
           (coll (async-eval (nth args 1) env ctx))
@@ -1141,7 +1141,7 @@
       results)))
 
 
-(define-async async-aser-ho-for-each
+(define-async async-aser-ho-for-each :effects [render io]
   (fn ((args :as list) (env :as dict) ctx)
     (let ((f (async-eval (first args) env ctx))
           (coll (async-eval (nth args 1) env ctx))
@@ -1172,7 +1172,7 @@
 ;;   (sx-expr? x)             — check if SxExpr
 ;;   (set-expand-components!) — enable component expansion context var
 
-(define-async async-eval-slot-inner
+(define-async async-eval-slot-inner :effects [render io]
   (fn (expr (env :as dict) ctx)
     ;; NOTE: Uses statement-form let + set! to avoid expression-context
     ;; let (IIFE lambdas) which can't contain await in Python.
@@ -1198,7 +1198,7 @@
             (make-sx-expr (serialize result))))))))
 
 
-(define-async async-maybe-expand-result
+(define-async async-maybe-expand-result :effects [render io]
   (fn (result (env :as dict) ctx)
     ;; If the aser result is a component call string like "(~foo ...)",
     ;; re-parse and expand it. This handles indirect component references
diff --git a/shared/sx/ref/adapter-dom.sx b/shared/sx/ref/adapter-dom.sx
index 5ff0b53..8c00e92 100644
--- a/shared/sx/ref/adapter-dom.sx
+++ b/shared/sx/ref/adapter-dom.sx
@@ -18,7 +18,7 @@
 ;; render-to-dom — main entry point
 ;; --------------------------------------------------------------------------
 
-(define render-to-dom
+(define render-to-dom :effects [render]
   (fn (expr (env :as dict) (ns :as string))
     (set-render-active! true)
     (case (type-of expr)
@@ -66,7 +66,7 @@
 ;; render-dom-list — dispatch on list head
 ;; --------------------------------------------------------------------------
 
-(define render-dom-list
+(define render-dom-list :effects [render]
   (fn (expr (env :as dict) (ns :as string))
     (let ((head (first expr)))
       (cond
@@ -165,7 +165,7 @@
 ;; render-dom-element — create a DOM element with attrs and children
 ;; --------------------------------------------------------------------------
 
-(define render-dom-element
+(define render-dom-element :effects [render]
   (fn ((tag :as string) (args :as list) (env :as dict) (ns :as string))
     ;; Detect namespace from tag
     (let ((new-ns (cond (= tag "svg") SVG_NS
@@ -236,7 +236,7 @@
 ;; render-dom-component — expand and render a component
 ;; --------------------------------------------------------------------------
 
-(define render-dom-component
+(define render-dom-component :effects [render]
   (fn ((comp :as component) (args :as list) (env :as dict) (ns :as string))
     ;; Parse kwargs and children, bind into component env, render body.
     (let ((kwargs (dict))
@@ -283,7 +283,7 @@
 ;; render-dom-fragment — render children into a DocumentFragment
 ;; --------------------------------------------------------------------------
 
-(define render-dom-fragment
+(define render-dom-fragment :effects [render]
   (fn ((args :as list) (env :as dict) (ns :as string))
     (let ((frag (create-fragment)))
       (for-each
@@ -296,7 +296,7 @@
 ;; render-dom-raw — insert unescaped content
 ;; --------------------------------------------------------------------------
 
-(define render-dom-raw
+(define render-dom-raw :effects [render]
   (fn ((args :as list) (env :as dict))
     (let ((frag (create-fragment)))
       (for-each
@@ -317,7 +317,7 @@
 ;; render-dom-unknown-component — visible warning element
 ;; --------------------------------------------------------------------------
 
-(define render-dom-unknown-component
+(define render-dom-unknown-component :effects [render]
   (fn ((name :as string))
     (error (str "Unknown component: " name))))
 
@@ -334,11 +334,11 @@
         "map" "map-indexed" "filter" "for-each" "portal"
         "error-boundary"))
 
-(define render-dom-form?
+(define render-dom-form? :effects []
   (fn ((name :as string))
     (contains? RENDER_DOM_FORMS name)))
 
-(define dispatch-render-form
+(define dispatch-render-form :effects [render]
   (fn ((name :as string) expr (env :as dict) (ns :as string))
     (cond
       ;; if — reactive inside islands (re-renders when signal deps change)
@@ -580,7 +580,7 @@
 ;; render-lambda-dom — render a lambda body in DOM context
 ;; --------------------------------------------------------------------------
 
-(define render-lambda-dom
+(define render-lambda-dom :effects [render]
   (fn ((f :as lambda) (args :as list) (env :as dict) (ns :as string))
     ;; Bind lambda params and render body as DOM
     (let ((local (env-merge (lambda-closure f) env)))
@@ -604,7 +604,7 @@
 ;;   - Attribute bindings: (deref sig) in attr → reactive attribute
 ;;   - Conditional fragments: (when (deref sig) ...) → reactive show/hide
 
-(define render-dom-island
+(define render-dom-island :effects [render mutation]
   (fn ((island :as island) (args :as list) (env :as dict) (ns :as string))
     ;; Parse kwargs and children (same as component)
     (let ((kwargs (dict))
@@ -678,7 +678,7 @@
 ;;
 ;; Supports :tag keyword to change wrapper element (default "div").
 
-(define render-dom-lake
+(define render-dom-lake :effects [render]
   (fn ((args :as list) (env :as dict) (ns :as string))
     (let ((lake-id nil)
           (lake-tag "div")
@@ -722,7 +722,7 @@
 ;; Renders as <div data-sx-marsh="name">children</div>.
 ;; Stores the island env and transform on the element for morph retrieval.
 
-(define render-dom-marsh
+(define render-dom-marsh :effects [render]
   (fn ((args :as list) (env :as dict) (ns :as string))
     (let ((marsh-id nil)
           (marsh-tag "div")
@@ -769,7 +769,7 @@
 
 ;; reactive-text — create a text node bound to a signal
 ;; Used when (deref sig) appears in a text position inside an island.
-(define reactive-text
+(define reactive-text :effects [render mutation]
   (fn (sig)
     (let ((node (create-text-node (str (deref sig)))))
       (effect (fn ()
@@ -780,7 +780,7 @@
 ;; Used when an attribute value contains (deref sig) inside an island.
 ;; Marks the attribute name on the element via data-sx-reactive-attrs so
 ;; the morph algorithm knows not to overwrite it with server content.
-(define reactive-attr
+(define reactive-attr :effects [render mutation]
   (fn (el (attr-name :as string) (compute-fn :as lambda))
     ;; Mark this attribute as reactively managed
     (let ((existing (or (dom-get-attr el "data-sx-reactive-attrs") ""))
@@ -801,7 +801,7 @@
 
 ;; reactive-fragment — conditionally render a fragment based on a signal
 ;; Used for (when (deref sig) ...) or (if (deref sig) ...) inside an island.
-(define reactive-fragment
+(define reactive-fragment :effects [render mutation]
   (fn ((test-fn :as lambda) (render-fn :as lambda) (env :as dict) (ns :as string))
     (let ((marker (create-comment "island-fragment"))
           (current-nodes (list)))
@@ -823,13 +823,13 @@
 ;; existing DOM nodes are reused across updates. Only additions, removals,
 ;; and reorderings touch the DOM. Without keys, falls back to clear+rerender.
 
-(define render-list-item
+(define render-list-item :effects [render]
   (fn ((map-fn :as lambda) item (env :as dict) (ns :as string))
     (if (lambda? map-fn)
       (render-lambda-dom map-fn (list item) env ns)
       (render-to-dom (apply map-fn (list item)) env ns))))
 
-(define extract-key
+(define extract-key :effects [render]
   (fn (node (index :as number))
     ;; Extract key from rendered node: :key attr, data-key, or index fallback
     (let ((k (dom-get-attr node "key")))
@@ -838,7 +838,7 @@
         (let ((dk (dom-get-data node "key")))
           (if dk (str dk) (str "__idx_" index)))))))
 
-(define reactive-list
+(define reactive-list :effects [render mutation]
   (fn ((map-fn :as lambda) (items-sig :as signal) (env :as dict) (ns :as string))
     (let ((container (create-fragment))
           (marker (create-comment "island-list"))
@@ -924,7 +924,7 @@
 ;;
 ;; Handles: input[text/number/email/...], textarea, select, checkbox, radio
 
-(define bind-input
+(define bind-input :effects [render mutation]
   (fn (el (sig :as signal))
     (let ((input-type (lower (or (dom-get-attr el "type") "")))
           (is-checkbox (or (= input-type "checkbox")
@@ -959,7 +959,7 @@
 ;; position. Registers a disposer to clean up portal content on island
 ;; teardown.
 
-(define render-dom-portal
+(define render-dom-portal :effects [render]
   (fn ((args :as list) (env :as dict) (ns :as string))
     (let ((selector (trampoline (eval-expr (first args) env)))
           (target (or (dom-query selector)
@@ -999,7 +999,7 @@
 ;;   (fn (err retry) ...)
 ;; Calling (retry) re-renders the body, replacing the fallback.
 
-(define render-dom-error-boundary
+(define render-dom-error-boundary :effects [render]
   (fn ((args :as list) (env :as dict) (ns :as string))
     (let ((fallback-expr (first args))
           (body-exprs (rest args))
diff --git a/shared/sx/ref/adapter-html.sx b/shared/sx/ref/adapter-html.sx
index fa44e2d..368dd89 100644
--- a/shared/sx/ref/adapter-html.sx
+++ b/shared/sx/ref/adapter-html.sx
@@ -13,7 +13,7 @@
 ;; ==========================================================================
 
 
-(define render-to-html
+(define render-to-html :effects [render]
   (fn (expr (env :as dict))
     (set-render-active! true)
     (case (type-of expr)
@@ -33,7 +33,7 @@
       ;; Everything else — evaluate first
       :else     (render-value-to-html (trampoline (eval-expr expr env)) env))))
 
-(define render-value-to-html
+(define render-value-to-html :effects [render]
   (fn (val (env :as dict))
     (case (type-of val)
       "nil"     ""
@@ -55,7 +55,7 @@
         "deftype" "defeffect"
         "map" "map-indexed" "filter" "for-each"))
 
-(define render-html-form?
+(define render-html-form? :effects []
   (fn ((name :as string))
     (contains? RENDER_HTML_FORMS name)))
 
@@ -64,7 +64,7 @@
 ;; render-list-to-html — dispatch on list head
 ;; --------------------------------------------------------------------------
 
-(define render-list-to-html
+(define render-list-to-html :effects [render]
   (fn ((expr :as list) (env :as dict))
     (if (empty? expr)
       ""
@@ -135,7 +135,7 @@
 ;; dispatch-html-form — render-aware special form handling for HTML output
 ;; --------------------------------------------------------------------------
 
-(define dispatch-html-form
+(define dispatch-html-form :effects [render]
   (fn ((name :as string) (expr :as list) (env :as dict))
     (cond
       ;; if
@@ -235,7 +235,7 @@
 ;; render-lambda-html — render a lambda body in HTML context
 ;; --------------------------------------------------------------------------
 
-(define render-lambda-html
+(define render-lambda-html :effects [render]
   (fn ((f :as lambda) (args :as list) (env :as dict))
     (let ((local (env-merge (lambda-closure f) env)))
       (for-each-indexed
@@ -249,7 +249,7 @@
 ;; render-html-component — expand and render a component
 ;; --------------------------------------------------------------------------
 
-(define render-html-component
+(define render-html-component :effects [render]
   (fn ((comp :as component) (args :as list) (env :as dict))
     ;; Expand component and render body through HTML adapter.
     ;; Component body contains rendering forms (HTML tags) that only the
@@ -288,7 +288,7 @@
         (render-to-html (component-body comp) local)))))
 
 
-(define render-html-element
+(define render-html-element :effects [render]
   (fn ((tag :as string) (args :as list) (env :as dict))
     (let ((parsed (parse-element-args args env))
           (attrs  (first parsed))
@@ -312,7 +312,7 @@
 ;; Lakes are server territory inside islands. The morph can update lake
 ;; content while preserving surrounding reactive DOM.
 
-(define render-html-lake
+(define render-html-lake :effects [render]
   (fn ((args :as list) (env :as dict))
     (let ((lake-id nil)
           (lake-tag "div")
@@ -351,7 +351,7 @@
 ;; re-evaluated in the island's signal scope. Server renders children normally;
 ;; the :transform is a client-only concern.
 
-(define render-html-marsh
+(define render-html-marsh :effects [render]
   (fn ((args :as list) (env :as dict))
     (let ((marsh-id nil)
           (marsh-tag "div")
@@ -394,7 +394,7 @@
 ;;   (reset! s v) → no-op
 ;;   (swap! s f)  → no-op
 
-(define render-html-island
+(define render-html-island :effects [render]
   (fn ((island :as island) (args :as list) (env :as dict))
     ;; Parse kwargs and children (same pattern as render-html-component)
     (let ((kwargs (dict))
@@ -452,7 +452,7 @@
 ;; Uses the SX serializer (not JSON) so the client can parse with sx-parse.
 ;; Handles all SX types natively: numbers, strings, booleans, nil, lists, dicts.
 
-(define serialize-island-state
+(define serialize-island-state :effects []
   (fn ((kwargs :as dict))
     (if (empty-dict? kwargs)
       nil
diff --git a/shared/sx/ref/adapter-sx.sx b/shared/sx/ref/adapter-sx.sx
index a97f5f6..f55da20 100644
--- a/shared/sx/ref/adapter-sx.sx
+++ b/shared/sx/ref/adapter-sx.sx
@@ -11,7 +11,7 @@
 ;; ==========================================================================
 
 
-(define render-to-sx
+(define render-to-sx :effects [render]
   (fn (expr (env :as dict))
     (let ((result (aser expr env)))
       ;; aser-call already returns serialized SX strings;
@@ -20,7 +20,7 @@
         result
         (serialize result)))))
 
-(define aser
+(define aser :effects [render]
   (fn ((expr :as any) (env :as dict))
     ;; Evaluate for SX wire format — serialize rendering forms,
     ;; evaluate control flow and function calls.
@@ -51,7 +51,7 @@
       :else expr)))
 
 
-(define aser-list
+(define aser-list :effects [render]
   (fn ((expr :as list) (env :as dict))
     (let ((head (first expr))
           (args (rest expr)))
@@ -103,7 +103,7 @@
                   :else (error (str "Not callable: " (inspect f)))))))))))
 
 
-(define aser-fragment
+(define aser-fragment :effects [render]
   (fn ((children :as list) (env :as dict))
     ;; Serialize (<> child1 child2 ...) to sx source string
     ;; Must flatten list results (e.g. from map/filter) to avoid nested parens
@@ -125,7 +125,7 @@
         (str "(<> " (join " " parts) ")")))))
 
 
-(define aser-call
+(define aser-call :effects [render]
   (fn ((name :as string) (args :as list) (env :as dict))
     ;; Serialize (name :key val child ...) — evaluate args but keep as sx
     ;; Uses for-each + mutable state (not reduce) so bootstrapper emits for-loops
@@ -177,11 +177,11 @@
   (list "map" "map-indexed" "filter" "reduce"
         "some" "every?" "for-each"))
 
-(define special-form?
+(define special-form? :effects []
   (fn ((name :as string))
     (contains? SPECIAL_FORM_NAMES name)))
 
-(define ho-form?
+(define ho-form? :effects []
   (fn ((name :as string))
     (contains? HO_FORM_NAMES name)))
 
@@ -194,7 +194,7 @@
 ;; through aser (serializing tags/components instead of rendering HTML).
 ;; Definition forms evaluate for side effects and return nil.
 
-(define aser-special
+(define aser-special :effects [render]
   (fn ((name :as string) (expr :as list) (env :as dict))
     (let ((args (rest expr)))
       (cond
@@ -315,7 +315,7 @@
 
 
 ;; Helper: case dispatch for aser mode
-(define eval-case-aser
+(define eval-case-aser :effects [render]
   (fn (match-val (clauses :as list) (env :as dict))
     (if (< (len clauses) 2)
       nil
diff --git a/shared/sx/ref/boot.sx b/shared/sx/ref/boot.sx
index 494bbf4..aca976a 100644
--- a/shared/sx/ref/boot.sx
+++ b/shared/sx/ref/boot.sx
@@ -26,7 +26,7 @@
 (define HEAD_HOIST_SELECTOR
   "meta, title, link[rel='canonical'], script[type='application/ld+json']")
 
-(define hoist-head-elements-full
+(define hoist-head-elements-full :effects [mutation io]
   (fn (root)
     (let ((els (dom-query-all root HEAD_HOIST_SELECTOR)))
       (for-each
@@ -71,7 +71,7 @@
 ;; Mount — render SX source into a DOM element
 ;; --------------------------------------------------------------------------
 
-(define sx-mount
+(define sx-mount :effects [mutation io]
   (fn (target (source :as string) (extra-env :as dict))
     ;; Render SX source string into target element.
     ;; target: Element or CSS selector string
@@ -100,7 +100,7 @@
 ;; Finds the suspense wrapper by data-suspense attribute, renders the
 ;; new SX content, and replaces the wrapper's children.
 
-(define resolve-suspense
+(define resolve-suspense :effects [mutation io]
   (fn ((id :as string) (sx :as string))
     ;; Process any new <script type="text/sx"> tags that arrived via
     ;; streaming (e.g. extra component defs) before resolving.
@@ -127,7 +127,7 @@
 ;; Hydrate — render all [data-sx] elements
 ;; --------------------------------------------------------------------------
 
-(define sx-hydrate-elements
+(define sx-hydrate-elements :effects [mutation io]
   (fn (root)
     ;; Find all [data-sx] elements within root and render them.
     (let ((els (dom-query-all (or root (dom-body)) "[data-sx]")))
@@ -143,7 +143,7 @@
 ;; Update — re-render a [data-sx] element with new env data
 ;; --------------------------------------------------------------------------
 
-(define sx-update-element
+(define sx-update-element :effects [mutation io]
   (fn (el new-env)
     ;; Re-render a [data-sx] element.
     ;; Reads source from data-sx attr, base env from data-sx-env attr.
@@ -165,7 +165,7 @@
 ;; Render component — build synthetic call from kwargs dict
 ;; --------------------------------------------------------------------------
 
-(define sx-render-component
+(define sx-render-component :effects [mutation io]
   (fn ((name :as string) (kwargs :as dict) (extra-env :as dict))
     ;; Render a named component with keyword args.
     ;; name: component name (with or without ~ prefix)
@@ -190,7 +190,7 @@
 ;; Script processing — <script type="text/sx">
 ;; --------------------------------------------------------------------------
 
-(define process-sx-scripts
+(define process-sx-scripts :effects [mutation io]
   (fn (root)
     ;; Process all <script type="text/sx"> tags.
     ;; - data-components + data-hash → localStorage cache
@@ -235,7 +235,7 @@
 ;; Component script with caching
 ;; --------------------------------------------------------------------------
 
-(define process-component-script
+(define process-component-script :effects [mutation io]
   (fn (script (text :as string))
     ;; Handle <script type="text/sx" data-components data-hash="...">
     (let ((hash (dom-get-attr script "data-hash")))
@@ -288,7 +288,7 @@
 
 (define _page-routes (list))
 
-(define process-page-scripts
+(define process-page-scripts :effects [mutation io]
   (fn ()
     ;; Process <script type="text/sx-pages"> tags.
     ;; Parses SX page registry and builds route entries with parsed patterns.
@@ -331,7 +331,7 @@
 ;; 5. Morph existing DOM to preserve structure, focus, scroll
 ;; 6. Store disposers on the element for cleanup
 
-(define sx-hydrate-islands
+(define sx-hydrate-islands :effects [mutation io]
   (fn (root)
     (let ((els (dom-query-all (or root (dom-body)) "[data-sx-island]")))
       (for-each
@@ -341,7 +341,7 @@
             (hydrate-island el)))
         els))))
 
-(define hydrate-island
+(define hydrate-island :effects [mutation io]
   (fn (el)
     (let ((name (dom-get-attr el "data-sx-island"))
           (state-sx (or (dom-get-attr el "data-sx-state") "{}")))
@@ -388,7 +388,7 @@
 ;; Island disposal — clean up when island removed from DOM
 ;; --------------------------------------------------------------------------
 
-(define dispose-island
+(define dispose-island :effects [mutation io]
   (fn (el)
     (let ((disposers (dom-get-data el "sx-disposers")))
       (when disposers
@@ -398,7 +398,7 @@
           disposers)
         (dom-set-data el "sx-disposers" nil)))))
 
-(define dispose-islands-in
+(define dispose-islands-in :effects [mutation io]
   (fn (root)
     ;; Dispose islands within root, but SKIP hydrated islands —
     ;; they may be preserved across morphs. Only dispose islands
@@ -419,7 +419,7 @@
 ;; Full boot sequence
 ;; --------------------------------------------------------------------------
 
-(define boot-init
+(define boot-init :effects [mutation io]
   (fn ()
     ;; Full browser initialization:
     ;; 1. CSS tracking
diff --git a/shared/sx/ref/bootstrap_py.py b/shared/sx/ref/bootstrap_py.py
index eb2e342..b84010b 100644
--- a/shared/sx/ref/bootstrap_py.py
+++ b/shared/sx/ref/bootstrap_py.py
@@ -664,7 +664,12 @@ class PyEmitter:
     def _emit_define(self, expr, indent: int = 0) -> str:
         pad = "    " * indent
         name = expr[1].name if isinstance(expr[1], Symbol) else str(expr[1])
-        val_expr = expr[2]
+        # Handle (define name :effects [...] value) — skip :effects annotation
+        if (len(expr) >= 5 and isinstance(expr[2], Keyword)
+                and expr[2].name == "effects"):
+            val_expr = expr[4]
+        else:
+            val_expr = expr[2]
         # Always emit fn-bodied defines as def statements for flat control flow
         if (isinstance(val_expr, list) and val_expr and
                 isinstance(val_expr[0], Symbol) and val_expr[0].name in ("fn", "lambda")):
@@ -675,7 +680,12 @@ class PyEmitter:
     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]
+        # Handle (define-async name :effects [...] value) — skip :effects annotation
+        if (len(expr) >= 5 and isinstance(expr[2], Keyword)
+                and expr[2].name == "effects"):
+            val_expr = expr[4]
+        else:
+            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)
diff --git a/shared/sx/ref/deps.sx b/shared/sx/ref/deps.sx
index fd66a26..b52a62e 100644
--- a/shared/sx/ref/deps.sx
+++ b/shared/sx/ref/deps.sx
@@ -31,14 +31,14 @@
 ;; Walks all branches of control flow (if/when/cond/case) to find
 ;; every component that *could* be rendered.
 
-(define scan-refs
+(define scan-refs :effects []
   (fn (node)
     (let ((refs (list)))
       (scan-refs-walk node refs)
       refs)))
 
 
-(define scan-refs-walk
+(define scan-refs-walk :effects []
   (fn (node (refs :as list))
     (cond
       ;; Symbol starting with ~ → component reference
@@ -67,7 +67,7 @@
 ;; Given a component name and an environment, compute all components
 ;; that it can transitively render.  Handles cycles via seen-set.
 
-(define transitive-deps-walk
+(define transitive-deps-walk :effects []
   (fn ((n :as string) (seen :as list) (env :as dict))
     (when (not (contains? seen n))
       (append! seen n)
@@ -82,7 +82,7 @@
           :else nil)))))
 
 
-(define transitive-deps
+(define transitive-deps :effects []
   (fn ((name :as string) (env :as dict))
     (let ((seen (list))
           (key (if (starts-with? name "~") name (str "~" name))))
@@ -100,7 +100,7 @@
 ;;   (env-components env) → list of component names in env
 ;;   (component-set-deps! comp deps) → store deps on component
 
-(define compute-all-deps
+(define compute-all-deps :effects [mutation]
   (fn ((env :as dict))
     (for-each
       (fn ((name :as string))
@@ -119,7 +119,7 @@
 ;; Platform interface:
 ;;   (regex-find-all pattern source) → list of matched group strings
 
-(define scan-components-from-source
+(define scan-components-from-source :effects []
   (fn ((source :as string))
     (let ((matches (regex-find-all "\\(~([a-zA-Z_][a-zA-Z0-9_\\-]*)" source)))
       (map (fn ((m :as string)) (str "~" m)) matches))))
@@ -131,7 +131,7 @@
 ;; Scans page source for direct component references, then computes
 ;; the transitive closure.  Returns list of ~names.
 
-(define components-needed
+(define components-needed :effects []
   (fn ((page-source :as string) (env :as dict))
     (let ((direct (scan-components-from-source page-source))
           (all-needed (list)))
@@ -165,7 +165,7 @@
 ;;
 ;; This replaces the "send everything" approach with per-page bundles.
 
-(define page-component-bundle
+(define page-component-bundle :effects []
   (fn ((page-source :as string) (env :as dict))
     (components-needed page-source env)))
 
@@ -180,7 +180,7 @@
 ;;   (component-css-classes c) → set/list of class strings
 ;;   (scan-css-classes source) → set/list of class strings from source
 
-(define page-css-classes
+(define page-css-classes :effects []
   (fn ((page-source :as string) (env :as dict))
     (let ((needed (components-needed page-source env))
           (classes (list)))
@@ -218,7 +218,7 @@
 ;;   (component-io-refs c)        → cached IO ref list (may be empty)
 ;;   (component-set-io-refs! c r) → cache IO refs on component
 
-(define scan-io-refs-walk
+(define scan-io-refs-walk :effects []
   (fn (node (io-names :as list) (refs :as list))
     (cond
       ;; Symbol → check if name is in the IO set
@@ -241,7 +241,7 @@
       :else nil)))
 
 
-(define scan-io-refs
+(define scan-io-refs :effects []
   (fn (node (io-names :as list))
     (let ((refs (list)))
       (scan-io-refs-walk node io-names refs)
@@ -252,7 +252,7 @@
 ;; 9. Transitive IO refs — follow component deps and union IO refs
 ;; --------------------------------------------------------------------------
 
-(define transitive-io-refs-walk
+(define transitive-io-refs-walk :effects []
   (fn ((n :as string) (seen :as list) (all-refs :as list) (env :as dict) (io-names :as list))
     (when (not (contains? seen n))
       (append! seen n)
@@ -285,7 +285,7 @@
           :else nil)))))
 
 
-(define transitive-io-refs
+(define transitive-io-refs :effects []
   (fn ((name :as string) (env :as dict) (io-names :as list))
     (let ((all-refs (list))
           (seen (list))
@@ -298,7 +298,7 @@
 ;; 10. Compute IO refs for all components in an environment
 ;; --------------------------------------------------------------------------
 
-(define compute-all-io-refs
+(define compute-all-io-refs :effects [mutation]
   (fn ((env :as dict) (io-names :as list))
     (for-each
       (fn ((name :as string))
@@ -308,7 +308,7 @@
       (env-components env))))
 
 
-(define component-io-refs-cached
+(define component-io-refs-cached :effects []
   (fn ((name :as string) (env :as dict) (io-names :as list))
     (let ((key (if (starts-with? name "~") name (str "~" name))))
       (let ((val (env-get env key)))
@@ -319,7 +319,7 @@
           ;; Fallback: not yet cached (shouldn't happen after compute-all-io-refs)
           (transitive-io-refs name env io-names))))))
 
-(define component-pure?
+(define component-pure? :effects []
   (fn ((name :as string) (env :as dict) (io-names :as list))
     (let ((key (if (starts-with? name "~") name (str "~" name))))
       (let ((val (env-get env key)))
@@ -343,7 +343,7 @@
 ;;
 ;; Returns: "server" | "client"
 
-(define render-target
+(define render-target :effects []
   (fn ((name :as string) (env :as dict) (io-names :as list))
     (let ((key (if (starts-with? name "~") name (str "~" name))))
       (let ((val (env-get env key)))
@@ -372,7 +372,7 @@
 ;; The async evaluator and client router both use it to make decisions
 ;; without recomputing at every request.
 
-(define page-render-plan
+(define page-render-plan :effects []
   (fn ((page-source :as string) (env :as dict) (io-names :as list))
     (let ((needed (components-needed page-source env))
           (comp-targets (dict))
@@ -450,7 +450,7 @@
 ;; --------------------------------------------------------------------------
 ;; Moved from platform to spec: pure logic using type predicates.
 
-(define env-components
+(define env-components :effects []
   (fn ((env :as dict))
     (filter
       (fn ((k :as string))
diff --git a/shared/sx/ref/engine.sx b/shared/sx/ref/engine.sx
index 9f1d9e9..e070536 100644
--- a/shared/sx/ref/engine.sx
+++ b/shared/sx/ref/engine.sx
@@ -31,7 +31,7 @@
 ;; Parses the sx-trigger attribute value into a list of trigger descriptors.
 ;; Each descriptor is a dict with "event" and "modifiers" keys.
 
-(define parse-time
+(define parse-time :effects []
   (fn ((s :as string))
     ;; Parse time string: "2s" → 2000, "500ms" → 500
     ;; Uses nested if (not cond) because cond misclassifies 2-element
@@ -42,7 +42,7 @@
           (parse-int s 0))))))
 
 
-(define parse-trigger-spec
+(define parse-trigger-spec :effects []
   (fn ((spec :as string))
     ;; Parse "click delay:500ms once,change" → list of trigger descriptors
     (if (nil? spec)
@@ -80,7 +80,7 @@
             raw-parts))))))
 
 
-(define default-trigger
+(define default-trigger :effects []
   (fn ((tag-name :as string))
     ;; Default trigger for element type
     (cond
@@ -98,7 +98,7 @@
 ;; Verb extraction
 ;; --------------------------------------------------------------------------
 
-(define get-verb-info
+(define get-verb-info :effects [io]
   (fn (el)
     ;; Check element for sx-get, sx-post, etc. Returns (dict "method" "url") or nil.
     (some
@@ -114,7 +114,7 @@
 ;; Request header building
 ;; --------------------------------------------------------------------------
 
-(define build-request-headers
+(define build-request-headers :effects [io]
   (fn (el (loaded-components :as list) (css-hash :as string))
     ;; Build the SX request headers dict
     (let ((headers (dict
@@ -150,7 +150,7 @@
 ;; Response header processing
 ;; --------------------------------------------------------------------------
 
-(define process-response-headers
+(define process-response-headers :effects []
   (fn ((get-header :as lambda))
     ;; Extract all SX response header directives into a dict.
     ;; get-header is (fn (name) → string or nil).
@@ -174,7 +174,7 @@
 ;; Swap specification parsing
 ;; --------------------------------------------------------------------------
 
-(define parse-swap-spec
+(define parse-swap-spec :effects []
   (fn ((raw-swap :as string) (global-transitions? :as boolean))
     ;; Parse "innerHTML transition:true" → dict with style + transition flag
     (let ((parts (split (or raw-swap DEFAULT_SWAP) " "))
@@ -193,7 +193,7 @@
 ;; Retry logic
 ;; --------------------------------------------------------------------------
 
-(define parse-retry-spec
+(define parse-retry-spec :effects []
   (fn ((retry-attr :as string))
     ;; Parse "exponential:1000:30000" → spec dict or nil
     (if (nil? retry-attr)
@@ -205,7 +205,7 @@
           "cap-ms"    (parse-int (nth parts 2) 30000))))))
 
 
-(define next-retry-ms
+(define next-retry-ms :effects []
   (fn ((current-ms :as number) (cap-ms :as number))
     ;; Exponential backoff: double current, cap at max
     (min (* current-ms 2) cap-ms)))
@@ -215,7 +215,7 @@
 ;; Form parameter filtering
 ;; --------------------------------------------------------------------------
 
-(define filter-params
+(define filter-params :effects []
   (fn ((params-spec :as string) (all-params :as list))
     ;; Filter form parameters by sx-params spec.
     ;; all-params is a list of (key value) pairs.
@@ -239,7 +239,7 @@
 ;; Target resolution
 ;; --------------------------------------------------------------------------
 
-(define resolve-target
+(define resolve-target :effects [io]
   (fn (el)
     ;; Resolve the swap target for an element
     (let ((sel (dom-get-attr el "sx-target")))
@@ -253,7 +253,7 @@
 ;; Optimistic updates
 ;; --------------------------------------------------------------------------
 
-(define apply-optimistic
+(define apply-optimistic :effects [mutation io]
   (fn (el)
     ;; Apply optimistic update preview. Returns state for reverting, or nil.
     (let ((directive (dom-get-attr el "sx-optimistic")))
@@ -278,7 +278,7 @@
           state)))))
 
 
-(define revert-optimistic
+(define revert-optimistic :effects [mutation io]
   (fn ((state :as dict))
     ;; Revert an optimistic update
     (when state
@@ -299,7 +299,7 @@
 ;; Out-of-band swap identification
 ;; --------------------------------------------------------------------------
 
-(define find-oob-swaps
+(define find-oob-swaps :effects [mutation io]
   (fn (container)
     ;; Find elements marked for out-of-band swapping.
     ;; Returns list of (dict "element" el "swap-type" type "target-id" id).
@@ -329,7 +329,7 @@
 ;; preserving event listeners, focus, scroll position, and form state
 ;; on keyed (id) elements.
 
-(define morph-node
+(define morph-node :effects [mutation io]
   (fn (old-node new-node)
     ;; Morph old-node to match new-node, preserving listeners/state.
     (cond
@@ -371,7 +371,7 @@
             (morph-children old-node new-node))))))
 
 
-(define sync-attrs
+(define sync-attrs :effects [mutation io]
   (fn (old-el new-el)
     ;; Sync attributes from new to old, but skip reactively managed attrs.
     ;; data-sx-reactive-attrs="style,class" means those attrs are owned by
@@ -398,7 +398,7 @@
         (dom-attr-list old-el)))))
 
 
-(define morph-children
+(define morph-children :effects [mutation io]
   (fn (old-parent new-parent)
     ;; Reconcile children of old-parent to match new-parent.
     ;; Keyed elements (with id) are matched and moved in-place.
@@ -472,7 +472,7 @@
 ;;   - Lakes = server substance (content, morphed)
 ;;   - The morph = Aufhebung (cancellation/preservation/elevation of both)
 
-(define morph-island-children
+(define morph-island-children :effects [mutation io]
   (fn (old-island new-island)
     ;; Find all lake and marsh slots in both old and new islands
     (let ((old-lakes (dom-query-all old-island "[data-sx-lake]"))
@@ -522,7 +522,7 @@
 ;; as SX and rendered in the island's signal context. If the marsh has a
 ;; :transform function, it reshapes the content before evaluation.
 
-(define morph-marsh
+(define morph-marsh :effects [mutation io]
   (fn (old-marsh new-marsh island-el)
     (let ((transform (dom-get-data old-marsh "sx-marsh-transform"))
           (env (dom-get-data old-marsh "sx-marsh-env"))
@@ -555,7 +555,7 @@
 ;;
 ;; Values are JSON-parsed: "7" → 7, "\"hello\"" → "hello", "true" → true.
 
-(define process-signal-updates
+(define process-signal-updates :effects [mutation io]
   (fn (root)
     (let ((signal-els (dom-query-all root "[data-sx-signal]")))
       (for-each
@@ -576,7 +576,7 @@
 ;; Swap dispatch
 ;; --------------------------------------------------------------------------
 
-(define swap-dom-nodes
+(define swap-dom-nodes :effects [mutation io]
   (fn (target new-nodes (strategy :as string))
     ;; Execute a swap strategy on live DOM nodes.
     ;; new-nodes is typically a DocumentFragment or Element.
@@ -630,7 +630,7 @@
             (morph-children target wrapper))))))
 
 
-(define insert-remaining-siblings
+(define insert-remaining-siblings :effects [mutation io]
   (fn (parent ref-node sib)
     ;; Insert sibling chain after ref-node
     (when sib
@@ -643,7 +643,7 @@
 ;; String-based swap (fallback for HTML responses)
 ;; --------------------------------------------------------------------------
 
-(define swap-html-string
+(define swap-html-string :effects [mutation io]
   (fn (target (html :as string) (strategy :as string))
     ;; Execute a swap strategy using an HTML string (DOMParser pipeline).
     (case strategy
@@ -674,7 +674,7 @@
 ;; History management
 ;; --------------------------------------------------------------------------
 
-(define handle-history
+(define handle-history :effects [io]
   (fn (el (url :as string) (resp-headers :as dict))
     ;; Process history push/replace based on element attrs and response headers
     (let ((push-url     (dom-get-attr el "sx-push-url"))
@@ -700,7 +700,7 @@
 
 (define PRELOAD_TTL 30000)  ;; 30 seconds
 
-(define preload-cache-get
+(define preload-cache-get :effects [mutation]
   (fn ((cache :as dict) (url :as string))
     ;; Get and consume a cached preload response.
     ;; Returns (dict "text" ... "content-type" ...) or nil.
@@ -712,7 +712,7 @@
           (do (dict-delete! cache url) entry))))))
 
 
-(define preload-cache-set
+(define preload-cache-set :effects [mutation]
   (fn ((cache :as dict) (url :as string) (text :as string) (content-type :as string))
     ;; Store a preloaded response
     (dict-set! cache url
@@ -725,7 +725,7 @@
 ;; Maps trigger event names to binding strategies.
 ;; This is the logic; actual browser event binding is platform interface.
 
-(define classify-trigger
+(define classify-trigger :effects []
   (fn ((trigger :as dict))
     ;; Classify a parsed trigger descriptor for binding.
     ;; Returns one of: "poll", "intersect", "load", "revealed", "event"
@@ -742,7 +742,7 @@
 ;; Boost logic
 ;; --------------------------------------------------------------------------
 
-(define should-boost-link?
+(define should-boost-link? :effects [io]
   (fn (link)
     ;; Whether a link inside an sx-boost container should be boosted
     (let ((href (dom-get-attr link "href")))
@@ -756,7 +756,7 @@
            (not (dom-has-attr? link "sx-disable"))))))
 
 
-(define should-boost-form?
+(define should-boost-form? :effects [io]
   (fn (form)
     ;; Whether a form inside an sx-boost container should be boosted
     (and (not (dom-has-attr? form "sx-get"))
@@ -768,7 +768,7 @@
 ;; SSE event classification
 ;; --------------------------------------------------------------------------
 
-(define parse-sse-swap
+(define parse-sse-swap :effects [io]
   (fn (el)
     ;; Parse sx-sse-swap attribute
     ;; Returns event name to listen for (default "message")
diff --git a/shared/sx/ref/js.sx b/shared/sx/ref/js.sx
index 8de1cb5..6dfc6df 100644
--- a/shared/sx/ref/js.sx
+++ b/shared/sx/ref/js.sx
@@ -1318,10 +1318,15 @@
 
 (define js-emit-define
   (fn (expr)
+    ;; Handle (define name :effects [...] value) — skip :effects annotation
     (let ((name (if (= (type-of (nth expr 1)) "symbol")
                   (symbol-name (nth expr 1))
                   (str (nth expr 1))))
-          (val-expr (nth expr 2)))
+          (val-expr (if (and (>= (len expr) 5)
+                             (= (type-of (nth expr 2)) "keyword")
+                             (= (keyword-name (nth expr 2)) "effects"))
+                      (nth expr 4)
+                      (nth expr 2))))
       (if (nil? val-expr)
         (str "var " (js-mangle name) " = NIL;")
         ;; Detect zero-arg self-tail-recursive functions → while loops
diff --git a/shared/sx/ref/orchestration.sx b/shared/sx/ref/orchestration.sx
index 9ee6e56..2fd1f94 100644
--- a/shared/sx/ref/orchestration.sx
+++ b/shared/sx/ref/orchestration.sx
@@ -33,7 +33,7 @@
 ;; Event dispatch helpers
 ;; --------------------------------------------------------------------------
 
-(define dispatch-trigger-events
+(define dispatch-trigger-events :effects [mutation io]
   (fn (el (header-val :as string))
     ;; Dispatch events from SX-Trigger / SX-Trigger-After-Swap headers.
     ;; Value can be JSON object (name → detail) or comma-separated names.
@@ -58,7 +58,7 @@
 ;; CSS tracking
 ;; --------------------------------------------------------------------------
 
-(define init-css-tracking
+(define init-css-tracking :effects [mutation io]
   (fn ()
     ;; Read initial CSS hash from meta tag
     (let ((meta (dom-query "meta[name=\"sx-css-classes\"]")))
@@ -72,7 +72,7 @@
 ;; Request execution
 ;; --------------------------------------------------------------------------
 
-(define execute-request
+(define execute-request :effects [mutation io]
   (fn (el (verbInfo :as dict) (extraParams :as dict))
     ;; Gate checks then delegate to do-fetch.
     ;; verbInfo: dict with "method" and "url" (or nil to read from element).
@@ -105,7 +105,7 @@
                         extraParams))))))))))))
 
 
-(define do-fetch
+(define do-fetch :effects [mutation io]
   (fn (el (verb :as string) (method :as string) (url :as string) (extraParams :as dict))
     ;; Execute the actual fetch. Manages abort, headers, body, loading state.
     (let ((sync (dom-get-attr el "sx-sync")))
@@ -201,7 +201,7 @@
                       (dict "error" err))))))))))))
 
 
-(define handle-fetch-success
+(define handle-fetch-success :effects [mutation io]
   (fn (el (url :as string) (verb :as string) (extraParams :as dict) get-header (text :as string))
     ;; Route a successful response through the appropriate handler.
     (let ((resp-headers (process-response-headers get-header)))
@@ -269,7 +269,7 @@
               (dict "target" target-el "swap" swap-style)))))))
 
 
-(define handle-sx-response
+(define handle-sx-response :effects [mutation io]
   (fn (el target (text :as string) (swap-style :as string) (use-transition :as boolean))
     ;; Handle SX-format response: strip components, extract CSS, render, swap.
     (let ((cleaned (strip-component-scripts text)))
@@ -300,7 +300,7 @@
                     (post-swap target)))))))))))
 
 
-(define handle-html-response
+(define handle-html-response :effects [mutation io]
   (fn (el target (text :as string) (swap-style :as string) (use-transition :as boolean))
     ;; Handle HTML-format response: parse, OOB, select, swap.
     (let ((doc (dom-parse-html-document text)))
@@ -337,7 +337,7 @@
 ;; Retry
 ;; --------------------------------------------------------------------------
 
-(define handle-retry
+(define handle-retry :effects [mutation io]
   (fn (el (verb :as string) (method :as string) (url :as string) (extraParams :as dict))
     ;; Handle retry on failure if sx-retry is configured
     (let ((retry-attr (dom-get-attr el "sx-retry"))
@@ -357,7 +357,7 @@
 ;; Trigger binding
 ;; --------------------------------------------------------------------------
 
-(define bind-triggers
+(define bind-triggers :effects [mutation io]
   (fn (el (verbInfo :as dict))
     ;; Bind triggers from sx-trigger attribute (or defaults)
     (let ((triggers (or (parse-trigger-spec (dom-get-attr el "sx-trigger"))
@@ -392,7 +392,7 @@
         triggers))))
 
 
-(define bind-event
+(define bind-event :effects [mutation io]
   (fn (el (event-name :as string) (mods :as dict) (verbInfo :as dict))
     ;; Bind a standard DOM event trigger.
     ;; Handles delay, once, changed, optimistic, preventDefault.
@@ -453,7 +453,7 @@
 ;; Post-swap lifecycle
 ;; --------------------------------------------------------------------------
 
-(define post-swap
+(define post-swap :effects [mutation io]
   (fn (root)
     ;; Run lifecycle after swap: activate scripts, process SX, hydrate, process
     (activate-scripts root)
@@ -474,7 +474,7 @@
 ;;
 ;; Example: (button :sx-get "/search" :sx-on-settle "(reset! (use-store \"count\") 0)")
 
-(define process-settle-hooks
+(define process-settle-hooks :effects [mutation io]
   (fn (el)
     (let ((settle-expr (dom-get-attr el "sx-on-settle")))
       (when (and settle-expr (not (empty? settle-expr)))
@@ -484,7 +484,7 @@
             exprs))))))
 
 
-(define activate-scripts
+(define activate-scripts :effects [mutation io]
   (fn (root)
     ;; Re-activate scripts in swapped content.
     ;; Scripts inserted via innerHTML are inert — clone to make them execute.
@@ -505,7 +505,7 @@
 ;; OOB swap processing
 ;; --------------------------------------------------------------------------
 
-(define process-oob-swaps
+(define process-oob-swaps :effects [mutation io]
   (fn (container (swap-fn :as lambda))
     ;; Find and process out-of-band swaps in container.
     ;; swap-fn is (fn (target oob-element swap-type) ...).
@@ -529,7 +529,7 @@
 ;; Head element hoisting
 ;; --------------------------------------------------------------------------
 
-(define hoist-head-elements
+(define hoist-head-elements :effects [mutation io]
   (fn (container)
     ;; Move style[data-sx-css] and link[rel=stylesheet] to <head>
     ;; so they take effect globally.
@@ -551,7 +551,7 @@
 ;; Boost processing
 ;; --------------------------------------------------------------------------
 
-(define process-boosted
+(define process-boosted :effects [mutation io]
   (fn (root)
     ;; Find [sx-boost] containers and boost their descendants
     (for-each
@@ -560,7 +560,7 @@
       (dom-query-all (or root (dom-body)) "[sx-boost]"))))
 
 
-(define boost-descendants
+(define boost-descendants :effects [mutation io]
   (fn (container)
     ;; Boost links and forms within a container.
     ;; The sx-boost attribute value is the default target selector
@@ -609,7 +609,7 @@
 (define _page-data-cache (dict))
 (define _page-data-cache-ttl 30000)  ;; 30 seconds in ms
 
-(define page-data-cache-key
+(define page-data-cache-key :effects []
   (fn ((page-name :as string) (params :as dict))
     ;; Build a cache key from page name + params.
     ;; Params are from route matching so order is deterministic.
@@ -623,7 +623,7 @@
             (keys params))
           (str base ":" (join "&" parts)))))))
 
-(define page-data-cache-get
+(define page-data-cache-get :effects [mutation io]
   (fn ((cache-key :as string))
     ;; Return cached data if fresh, else nil.
     (let ((entry (get _page-data-cache cache-key)))
@@ -635,7 +635,7 @@
             nil)
           (get entry "data"))))))
 
-(define page-data-cache-set
+(define page-data-cache-set :effects [mutation io]
   (fn ((cache-key :as string) data)
     ;; Store data with current timestamp.
     (dict-set! _page-data-cache cache-key
@@ -646,7 +646,7 @@
 ;; Client-side routing — cache management
 ;; --------------------------------------------------------------------------
 
-(define invalidate-page-cache
+(define invalidate-page-cache :effects [mutation io]
   (fn ((page-name :as string))
     ;; Clear cached data for a page. Removes all cache entries whose key
     ;; matches page-name (exact) or starts with "page-name:" (with params).
@@ -659,14 +659,14 @@
     (sw-post-message {"type" "invalidate" "page" page-name})
     (log-info (str "sx:cache invalidate " page-name))))
 
-(define invalidate-all-page-cache
+(define invalidate-all-page-cache :effects [mutation io]
   (fn ()
     ;; Clear all cached page data and notify service worker.
     (set! _page-data-cache (dict))
     (sw-post-message {"type" "invalidate" "page" "*"})
     (log-info "sx:cache invalidate *")))
 
-(define update-page-cache
+(define update-page-cache :effects [mutation io]
   (fn ((page-name :as string) data)
     ;; Replace cached data for a page with server-provided data.
     ;; Uses a bare page-name key (no params) — the server knows the
@@ -675,7 +675,7 @@
       (page-data-cache-set cache-key data)
       (log-info (str "sx:cache update " page-name)))))
 
-(define process-cache-directives
+(define process-cache-directives :effects [mutation io]
   (fn (el (resp-headers :as dict) (response-text :as string))
     ;; Process cache invalidation and update directives from both
     ;; element attributes and response headers.
@@ -721,7 +721,7 @@
 
 (define _optimistic-snapshots (dict))
 
-(define optimistic-cache-update
+(define optimistic-cache-update :effects [mutation]
   (fn ((cache-key :as string) (mutator :as lambda))
     ;; Apply predicted mutation to cached data. Saves snapshot for rollback.
     ;; Returns predicted data or nil if no cached data exists.
@@ -734,7 +734,7 @@
           (page-data-cache-set cache-key predicted)
           predicted)))))
 
-(define optimistic-cache-revert
+(define optimistic-cache-revert :effects [mutation]
   (fn ((cache-key :as string))
     ;; Revert to pre-mutation snapshot. Returns restored data or nil.
     (let ((snapshot (get _optimistic-snapshots cache-key)))
@@ -743,12 +743,12 @@
         (dict-delete! _optimistic-snapshots cache-key)
         snapshot))))
 
-(define optimistic-cache-confirm
+(define optimistic-cache-confirm :effects [mutation]
   (fn ((cache-key :as string))
     ;; Server accepted — discard the rollback snapshot.
     (dict-delete! _optimistic-snapshots cache-key)))
 
-(define submit-mutation
+(define submit-mutation :effects [mutation io]
   (fn ((page-name :as string) (params :as dict) (action-name :as string) payload (mutator-fn :as lambda) (on-complete :as lambda))
     ;; Optimistic mutation: predict locally, send to server, confirm or revert.
     ;; on-complete is called with "confirmed" or "reverted" status.
@@ -787,14 +787,14 @@
 (define _is-online true)
 (define _offline-queue (list))
 
-(define offline-is-online?
+(define offline-is-online? :effects [io]
   (fn () _is-online))
 
-(define offline-set-online!
+(define offline-set-online! :effects [mutation]
   (fn ((val :as boolean))
     (set! _is-online val)))
 
-(define offline-queue-mutation
+(define offline-queue-mutation :effects [mutation io]
   (fn ((action-name :as string) payload (page-name :as string) (params :as dict) (mutator-fn :as lambda))
     ;; Queue a mutation for later sync. Apply optimistic update locally.
     (let ((cache-key (page-data-cache-key page-name params))
@@ -813,7 +813,7 @@
       (log-info (str "sx:offline queued " action-name " (" (len _offline-queue) " pending)"))
       entry)))
 
-(define offline-sync
+(define offline-sync :effects [mutation io]
   (fn ()
     ;; Replay all pending mutations. Called on reconnect.
     (let ((pending (filter (fn ((e :as dict)) (= (get e "status") "pending")) _offline-queue)))
@@ -830,11 +830,11 @@
                 (log-warn (str "sx:offline sync failed " (get entry "action") ": " error)))))
           pending)))))
 
-(define offline-pending-count
+(define offline-pending-count :effects [io]
   (fn ()
     (len (filter (fn ((e :as dict)) (= (get e "status") "pending")) _offline-queue))))
 
-(define offline-aware-mutation
+(define offline-aware-mutation :effects [mutation io]
   (fn ((page-name :as string) (params :as dict) (action-name :as string) payload (mutator-fn :as lambda) (on-complete :as lambda))
     ;; Top-level mutation function. Routes to submit-mutation when online,
     ;; offline-queue-mutation when offline.
@@ -849,7 +849,7 @@
 ;; Client-side routing
 ;; --------------------------------------------------------------------------
 
-(define current-page-layout
+(define current-page-layout :effects [io]
   (fn ()
     ;; Find the layout name of the currently displayed page by matching
     ;; the browser URL against the page route table.
@@ -859,7 +859,7 @@
         (or (get match "layout") "")))))
 
 
-(define swap-rendered-content
+(define swap-rendered-content :effects [mutation io]
   (fn (target rendered (pathname :as string))
     ;; Swap rendered DOM content into target and run post-processing.
     ;; Shared by pure and data page client routes.
@@ -875,7 +875,7 @@
       (log-info (str "sx:route client " pathname)))))
 
 
-(define resolve-route-target
+(define resolve-route-target :effects [io]
   (fn ((target-sel :as string))
     ;; Resolve a target selector to a DOM element, or nil.
     (if (and target-sel (not (= target-sel "true")))
@@ -883,7 +883,7 @@
       nil)))
 
 
-(define deps-satisfied?
+(define deps-satisfied? :effects [io]
   (fn ((match :as dict))
     ;; Check if all component deps for a page are loaded client-side.
     (let ((deps (get match "deps"))
@@ -893,7 +893,7 @@
         (every? (fn ((dep :as string)) (contains? loaded dep)) deps)))))
 
 
-(define try-client-route
+(define try-client-route :effects [mutation io]
   (fn ((pathname :as string) (target-sel :as string))
     ;; Try to render a page client-side. Returns true if successful, false otherwise.
     ;; target-sel is the CSS selector for the swap target (from sx-boost value).
@@ -1011,7 +1011,7 @@
                               true))))))))))))))))))
 
 
-(define bind-client-route-link
+(define bind-client-route-link :effects [mutation io]
   (fn (link (href :as string))
     ;; Bind a boost link with client-side routing. If the route can be
     ;; rendered client-side (pure page, no :data), do so. Otherwise
@@ -1026,7 +1026,7 @@
 ;; SSE processing
 ;; --------------------------------------------------------------------------
 
-(define process-sse
+(define process-sse :effects [mutation io]
   (fn (root)
     ;; Find and bind SSE elements
     (for-each
@@ -1037,7 +1037,7 @@
       (dom-query-all (or root (dom-body)) "[sx-sse]"))))
 
 
-(define bind-sse
+(define bind-sse :effects [mutation io]
   (fn (el)
     ;; Connect to SSE endpoint and bind swap handler
     (let ((url (dom-get-attr el "sx-sse")))
@@ -1049,7 +1049,7 @@
               (bind-sse-swap el data))))))))
 
 
-(define bind-sse-swap
+(define bind-sse-swap :effects [mutation io]
   (fn (el (data :as string))
     ;; Handle an SSE event: swap data into element
     (let ((target (resolve-target el))
@@ -1081,7 +1081,7 @@
 ;; Inline event handlers
 ;; --------------------------------------------------------------------------
 
-(define bind-inline-handlers
+(define bind-inline-handlers :effects [mutation io]
   (fn (root)
     ;; Find elements with sx-on:* attributes and bind SX event handlers.
     ;; Handler bodies are SX expressions evaluated with `event` and `this`
@@ -1115,7 +1115,7 @@
 ;; Preload
 ;; --------------------------------------------------------------------------
 
-(define bind-preload-for
+(define bind-preload-for :effects [mutation io]
   (fn (el)
     ;; Bind preload event listeners based on sx-preload attribute
     (let ((preload-attr (dom-get-attr el "sx-preload")))
@@ -1134,7 +1134,7 @@
                       (loaded-component-names) _css-hash)))))))))))
 
 
-(define do-preload
+(define do-preload :effects [mutation io]
   (fn ((url :as string) (headers :as dict))
     ;; Execute a preload fetch into the cache
     (when (nil? (preload-cache-get _preload-cache url))
@@ -1148,7 +1148,7 @@
 (define VERB_SELECTOR
   (str "[sx-get],[sx-post],[sx-put],[sx-delete],[sx-patch]"))
 
-(define process-elements
+(define process-elements :effects [mutation io]
   (fn (root)
     ;; Find all elements with sx-* verb attributes and process them.
     (let ((els (dom-query-all (or root (dom-body)) VERB_SELECTOR)))
@@ -1165,7 +1165,7 @@
     (process-emit-elements root)))
 
 
-(define process-one
+(define process-one :effects [mutation io]
   (fn (el)
     ;; Process a single element with an sx-* verb attribute
     (let ((verb-info (get-verb-info el)))
@@ -1193,7 +1193,7 @@
 ;; On click → dispatches CustomEvent "cart:add" with detail {id:42, name:"Widget"}
 ;; The event bubbles up to the island container where bridge-event catches it.
 
-(define process-emit-elements
+(define process-emit-elements :effects [mutation io]
   (fn (root)
     (let ((els (dom-query-all (or root (dom-body)) "[data-sx-emit]")))
       (for-each
@@ -1214,7 +1214,7 @@
 ;; History: popstate handler
 ;; --------------------------------------------------------------------------
 
-(define handle-popstate
+(define handle-popstate :effects [mutation io]
   (fn ((scrollY :as number))
     ;; Handle browser back/forward navigation.
     ;; Derive target from [sx-boost] container or fall back to #main-panel.
@@ -1241,7 +1241,7 @@
 ;; Initialization
 ;; --------------------------------------------------------------------------
 
-(define engine-init
+(define engine-init :effects [mutation io]
   (fn ()
     ;; Initialize: CSS tracking, scripts, hydrate, process.
     (do
diff --git a/shared/sx/ref/parser.sx b/shared/sx/ref/parser.sx
index f2e2943..919806b 100644
--- a/shared/sx/ref/parser.sx
+++ b/shared/sx/ref/parser.sx
@@ -49,20 +49,20 @@
 ;; --------------------------------------------------------------------------
 ;; Returns a list of top-level AST expressions.
 
-(define sx-parse
+(define sx-parse :effects []
   (fn ((source :as string))
     (let ((pos 0)
           (len-src (len source)))
 
       ;; -- Cursor helpers (closure over pos, source, len-src) --
 
-      (define skip-comment
+      (define skip-comment :effects []
         (fn ()
           (when (and (< pos len-src) (not (= (nth source pos) "\n")))
             (set! pos (inc pos))
             (skip-comment))))
 
-      (define skip-ws
+      (define skip-ws :effects []
         (fn ()
           (when (< pos len-src)
             (let ((ch (nth source pos)))
@@ -80,11 +80,11 @@
 
       ;; -- Atom readers --
 
-      (define read-string
+      (define read-string :effects []
         (fn ()
           (set! pos (inc pos))  ;; skip opening "
           (let ((buf ""))
-            (define read-str-loop
+            (define read-str-loop :effects []
               (fn ()
                 (if (>= pos len-src)
                   (error "Unterminated string")
@@ -110,10 +110,10 @@
             (read-str-loop)
             buf)))
 
-      (define read-ident
+      (define read-ident :effects []
         (fn ()
           (let ((start pos))
-            (define read-ident-loop
+            (define read-ident-loop :effects []
               (fn ()
                 (when (and (< pos len-src)
                            (ident-char? (nth source pos)))
@@ -122,19 +122,19 @@
             (read-ident-loop)
             (slice source start pos))))
 
-      (define read-keyword
+      (define read-keyword :effects []
         (fn ()
           (set! pos (inc pos))  ;; skip :
           (make-keyword (read-ident))))
 
-      (define read-number
+      (define read-number :effects []
         (fn ()
           (let ((start pos))
             ;; Optional leading minus
             (when (and (< pos len-src) (= (nth source pos) "-"))
               (set! pos (inc pos)))
             ;; Integer digits
-            (define read-digits
+            (define read-digits :effects []
               (fn ()
                 (when (and (< pos len-src)
                            (let ((c (nth source pos)))
@@ -158,7 +158,7 @@
               (read-digits))
             (parse-number (slice source start pos)))))
 
-      (define read-symbol
+      (define read-symbol :effects []
         (fn ()
           (let ((name (read-ident)))
             (cond
@@ -169,10 +169,10 @@
 
       ;; -- Composite readers --
 
-      (define read-list
+      (define read-list :effects []
         (fn ((close-ch :as string))
           (let ((items (list)))
-            (define read-list-loop
+            (define read-list-loop :effects []
               (fn ()
                 (skip-ws)
                 (if (>= pos len-src)
@@ -184,10 +184,10 @@
             (read-list-loop)
             items)))
 
-      (define read-map
+      (define read-map :effects []
         (fn ()
           (let ((result (dict)))
-            (define read-map-loop
+            (define read-map-loop :effects []
               (fn ()
                 (skip-ws)
                 (if (>= pos len-src)
@@ -206,10 +206,10 @@
 
       ;; -- Raw string reader (for #|...|) --
 
-      (define read-raw-string
+      (define read-raw-string :effects []
         (fn ()
           (let ((buf ""))
-            (define raw-loop
+            (define raw-loop :effects []
               (fn ()
                 (if (>= pos len-src)
                   (error "Unterminated raw string")
@@ -224,7 +224,7 @@
 
       ;; -- Main expression reader --
 
-      (define read-expr
+      (define read-expr :effects []
         (fn ()
           (skip-ws)
           (if (>= pos len-src)
@@ -322,7 +322,7 @@
 
       ;; -- Entry point: parse all top-level expressions --
       (let ((exprs (list)))
-        (define parse-loop
+        (define parse-loop :effects []
           (fn ()
             (skip-ws)
             (when (< pos len-src)
@@ -336,7 +336,7 @@
 ;; Serializer — AST → SX source text
 ;; --------------------------------------------------------------------------
 
-(define sx-serialize
+(define sx-serialize :effects []
   (fn (val)
     (case (type-of val)
       "nil"       "nil"
@@ -351,7 +351,7 @@
       :else       (str val))))
 
 
-(define sx-serialize-dict
+(define sx-serialize-dict :effects []
   (fn ((d :as dict))
     (str "{"
       (join " "
diff --git a/shared/sx/ref/render.sx b/shared/sx/ref/render.sx
index 7624f9b..d97968f 100644
--- a/shared/sx/ref/render.sx
+++ b/shared/sx/ref/render.sx
@@ -71,14 +71,14 @@
 ;; Shared utilities
 ;; --------------------------------------------------------------------------
 
-(define definition-form?
+(define definition-form? :effects []
   (fn ((name :as string))
     (or (= name "define") (= name "defcomp") (= name "defisland")
         (= name "defmacro") (= name "defstyle") (= name "defhandler")
         (= name "deftype") (= name "defeffect"))))
 
 
-(define parse-element-args
+(define parse-element-args :effects [render]
   (fn ((args :as list) (env :as dict))
     ;; Parse (:key val :key2 val2 child1 child2) into (attrs-dict children-list)
     (let ((attrs (dict))
@@ -101,7 +101,7 @@
       (list attrs children))))
 
 
-(define render-attrs
+(define render-attrs :effects []
   (fn ((attrs :as dict))
     ;; Render an attrs dict to an HTML attribute string.
     ;; Used by adapter-html.sx and adapter-sx.sx.
@@ -133,13 +133,13 @@
 ;; eval-cond: find matching cond branch, return unevaluated body expr.
 ;; Handles both scheme-style ((test body) ...) and clojure-style
 ;; (test body test body ...).
-(define eval-cond
+(define eval-cond :effects []
   (fn ((clauses :as list) (env :as dict))
     (if (cond-scheme? clauses)
       (eval-cond-scheme clauses env)
       (eval-cond-clojure clauses env))))
 
-(define eval-cond-scheme
+(define eval-cond-scheme :effects []
   (fn ((clauses :as list) (env :as dict))
     (if (empty? clauses)
       nil
@@ -156,7 +156,7 @@
             body
             (eval-cond-scheme (rest clauses) env)))))))
 
-(define eval-cond-clojure
+(define eval-cond-clojure :effects []
   (fn ((clauses :as list) (env :as dict))
     (if (< (len clauses) 2)
       nil
@@ -173,7 +173,7 @@
 
 ;; process-bindings: evaluate let-binding pairs, return extended env.
 ;; bindings = ((name1 expr1) (name2 expr2) ...)
-(define process-bindings
+(define process-bindings :effects [mutation]
   (fn ((bindings :as list) (env :as dict))
     ;; env-extend (not merge) — Env is not a dict subclass, so merge()
     ;; returns an empty dict, losing all parent scope bindings.
@@ -195,7 +195,7 @@
 ;; Used by eval-list to dispatch rendering forms to the active adapter
 ;; (HTML, SX wire, or DOM) rather than evaluating them as function calls.
 
-(define is-render-expr?
+(define is-render-expr? :effects []
   (fn (expr)
     (if (or (not (= (type-of expr) "list")) (empty? expr))
       false
diff --git a/shared/sx/ref/router.sx b/shared/sx/ref/router.sx
index 266d65d..9eb8f1f 100644
--- a/shared/sx/ref/router.sx
+++ b/shared/sx/ref/router.sx
@@ -17,7 +17,7 @@
 ;; "/" → ()
 ;; "/docs/" → ("docs")
 
-(define split-path-segments
+(define split-path-segments :effects []
   (fn ((path :as string))
     (let ((trimmed (if (starts-with? path "/") (slice path 1) path)))
       (let ((trimmed2 (if (and (not (empty? trimmed))
@@ -35,7 +35,7 @@
 ;; "/docs/<slug>" → ({"type" "literal" "value" "docs"}
 ;;                   {"type" "param" "value" "slug"})
 
-(define make-route-segment
+(define make-route-segment :effects []
   (fn ((seg :as string))
     (if (and (starts-with? seg "<") (ends-with? seg ">"))
       (let ((param-name (slice seg 1 (- (len seg) 1))))
@@ -48,7 +48,7 @@
         (dict-set! d "value" seg)
         d))))
 
-(define parse-route-pattern
+(define parse-route-pattern :effects []
   (fn ((pattern :as string))
     (let ((segments (split-path-segments pattern)))
       (map make-route-segment segments))))
@@ -59,7 +59,7 @@
 ;; --------------------------------------------------------------------------
 ;; Returns params dict if match, nil if no match.
 
-(define match-route-segments
+(define match-route-segments :effects []
   (fn ((path-segs :as list) (parsed-segs :as list))
     (if (not (= (len path-segs) (len parsed-segs)))
       nil
@@ -87,7 +87,7 @@
 ;; --------------------------------------------------------------------------
 ;; Returns params dict (may be empty for exact matches) or nil.
 
-(define match-route
+(define match-route :effects []
   (fn ((path :as string) (pattern :as string))
     (let ((path-segs (split-path-segments path))
           (parsed-segs (parse-route-pattern pattern)))
@@ -100,7 +100,7 @@
 ;; Each entry: {"pattern" "/docs/<slug>" "parsed" [...] "name" "docs-page" ...}
 ;; Returns matching entry with "params" added, or nil.
 
-(define find-matching-route
+(define find-matching-route :effects []
   (fn ((path :as string) (routes :as list))
     (let ((path-segs (split-path-segments path))
           (result nil))
diff --git a/shared/sx/ref/signals.sx b/shared/sx/ref/signals.sx
index 3491f7d..f7f6d11 100644
--- a/shared/sx/ref/signals.sx
+++ b/shared/sx/ref/signals.sx
@@ -41,7 +41,7 @@
 ;; 1. signal — create a reactive container
 ;; --------------------------------------------------------------------------
 
-(define signal
+(define signal :effects []
   (fn ((initial-value :as any))
     (make-signal initial-value)))
 
@@ -54,7 +54,7 @@
 ;; signal as a dependency. Outside reactive context, deref just returns
 ;; the current value — no subscription, no overhead.
 
-(define deref
+(define deref :effects []
   (fn ((s :as any))
     (if (not (signal? s))
       s  ;; non-signal values pass through
@@ -71,7 +71,7 @@
 ;; 3. reset! — write a new value, notify subscribers
 ;; --------------------------------------------------------------------------
 
-(define reset!
+(define reset! :effects [mutation]
   (fn ((s :as signal) value)
     (when (signal? s)
       (let ((old (signal-value s)))
@@ -84,7 +84,7 @@
 ;; 4. swap! — update signal via function
 ;; --------------------------------------------------------------------------
 
-(define swap!
+(define swap! :effects [mutation]
   (fn ((s :as signal) (f :as lambda) &rest args)
     (when (signal? s)
       (let ((old (signal-value s))
@@ -102,7 +102,7 @@
 ;; of its dependencies change. The dependency set is discovered automatically
 ;; by tracking deref calls during evaluation.
 
-(define computed
+(define computed :effects [mutation]
   (fn ((compute-fn :as lambda))
     (let ((s (make-signal nil))
           (deps (list))
@@ -145,7 +145,7 @@
 ;; Like computed, but doesn't produce a signal value. Returns a dispose
 ;; function that tears down the effect.
 
-(define effect
+(define effect :effects [mutation]
   (fn ((effect-fn :as lambda))
     (let ((deps (list))
           (disposed false)
@@ -201,7 +201,7 @@
 (define *batch-depth* 0)
 (define *batch-queue* (list))
 
-(define batch
+(define batch :effects [mutation]
   (fn ((thunk :as lambda))
     (set! *batch-depth* (+ *batch-depth* 1))
     (invoke thunk)
@@ -231,14 +231,14 @@
 ;;
 ;; If inside a batch, queues the signal. Otherwise, notifies immediately.
 
-(define notify-subscribers
+(define notify-subscribers :effects [mutation]
   (fn ((s :as signal))
     (if (> *batch-depth* 0)
       (when (not (contains? *batch-queue* s))
         (append! *batch-queue* s))
       (flush-subscribers s))))
 
-(define flush-subscribers
+(define flush-subscribers :effects [mutation]
   (fn ((s :as signal))
     (for-each
       (fn ((sub :as lambda)) (sub))
@@ -268,7 +268,7 @@
 ;; For computed signals, unsubscribe from all dependencies.
 ;; For effects, the dispose function is returned by effect itself.
 
-(define dispose-computed
+(define dispose-computed :effects [mutation]
   (fn ((s :as signal))
     (when (signal? s)
       (for-each
@@ -287,7 +287,7 @@
 
 (define *island-scope* nil)
 
-(define with-island-scope
+(define with-island-scope :effects [mutation]
   (fn ((scope-fn :as lambda) (body-fn :as lambda))
     (let ((prev *island-scope*))
       (set! *island-scope* scope-fn)
@@ -299,7 +299,7 @@
 ;; The platform's make-signal should call (register-in-scope s) if
 ;; *island-scope* is non-nil.
 
-(define register-in-scope
+(define register-in-scope :effects [mutation]
   (fn ((disposable :as lambda))
     (when *island-scope*
       (*island-scope* disposable))))
@@ -322,7 +322,7 @@
 ;;   (dom-set-data el key val) → void  — store JS value on element
 ;;   (dom-get-data el key)     → any   — retrieve stored value
 
-(define with-marsh-scope
+(define with-marsh-scope :effects [mutation io]
   (fn (marsh-el (body-fn :as lambda))
     ;; Execute body-fn collecting all disposables into a marsh-local list.
     ;; Nested under the current island scope — if the island is disposed,
@@ -335,7 +335,7 @@
       ;; Store disposers on the marsh element for later cleanup
       (dom-set-data marsh-el "sx-marsh-disposers" disposers))))
 
-(define dispose-marsh-scope
+(define dispose-marsh-scope :effects [mutation io]
   (fn (marsh-el)
     ;; Dispose all effects/computeds registered in this marsh's scope.
     ;; Parent island scope and sibling marshes are unaffected.
@@ -358,7 +358,7 @@
 
 (define *store-registry* (dict))
 
-(define def-store
+(define def-store :effects [mutation]
   (fn ((name :as string) (init-fn :as lambda))
     (let ((registry *store-registry*))
       ;; Only create the store once — subsequent calls return existing
@@ -366,14 +366,14 @@
         (set! *store-registry* (assoc registry name (invoke init-fn))))
       (get *store-registry* name))))
 
-(define use-store
+(define use-store :effects []
   (fn ((name :as string))
     (if (has-key? *store-registry* name)
       (get *store-registry* name)
       (error (str "Store not found: " name
                   ". Call (def-store ...) before (use-store ...).")))))
 
-(define clear-stores
+(define clear-stores :effects [mutation]
   (fn ()
     (set! *store-registry* (dict))))
 
@@ -401,11 +401,11 @@
 ;;
 ;; These are platform primitives because they require browser DOM APIs.
 
-(define emit-event
+(define emit-event :effects [io]
   (fn (el (event-name :as string) detail)
     (dom-dispatch el event-name detail)))
 
-(define on-event
+(define on-event :effects [io]
   (fn (el (event-name :as string) (handler :as lambda))
     (dom-listen el event-name handler)))
 
@@ -415,7 +415,7 @@
 ;; When the effect is disposed (island teardown), the listener is
 ;; removed automatically via the cleanup return.
 
-(define bridge-event
+(define bridge-event :effects [mutation io]
   (fn (el (event-name :as string) (target-signal :as signal) transform-fn)
     (effect (fn ()
       (let ((remove (dom-listen el event-name
@@ -449,7 +449,7 @@
 ;; Platform interface required:
 ;;   (promise-then promise on-resolve on-reject) → void
 
-(define resource
+(define resource :effects [mutation io]
   (fn ((fetch-fn :as lambda))
     (let ((state (signal (dict "loading" true "data" nil "error" nil))))
       ;; Kick off the async operation
diff --git a/shared/sx/ref/sx_ref.py b/shared/sx/ref/sx_ref.py
index 6a0e5fe..fdf007a 100644
--- a/shared/sx/ref/sx_ref.py
+++ b/shared/sx/ref/sx_ref.py
@@ -3937,4 +3937,4 @@ def render(expr, env=None):
 
 def make_env(**kwargs):
     """Create an environment with initial bindings."""
-    return _Env(dict(kwargs))
+    return _Env(dict(kwargs))
\ No newline at end of file