diff --git a/packages/dom/src/Render/DOMRenderer.ts b/packages/dom/src/Render/DOMRenderer.ts
index 88a7ce4..b642f34 100644
--- a/packages/dom/src/Render/DOMRenderer.ts
+++ b/packages/dom/src/Render/DOMRenderer.ts
@@ -25,8 +25,8 @@ export const DOMRenderer: Renderer<Node> = {
     Effect.sync(() => document.createTextNode(text)),
 
   appendChild: (parent: Node, child: Node) =>
-    Effect.sync(() => {
-      warnIfInvalidNesting(tagNameOf(parent), tagNameOf(child));
+    Effect.gen(function* () {
+      yield* warnIfInvalidNesting(tagNameOf(parent), tagNameOf(child));
       parent.appendChild(child);
     }),
 
diff --git a/packages/dom/src/Render/server/StringRenderer.ts b/packages/dom/src/Render/server/StringRenderer.ts
index 3d473d6..adabc9b 100644
--- a/packages/dom/src/Render/server/StringRenderer.ts
+++ b/packages/dom/src/Render/server/StringRenderer.ts
@@ -24,10 +24,10 @@ export const StringRenderer: Renderer<VNode> = {
   createTextNode: (text: string) => Effect.sync(() => vText(text)),
 
   appendChild: (parent: VNode, child: VNode) =>
-    Effect.sync(() => {
+    Effect.gen(function* () {
       if (parent._tag === "VElement") {
         if (child._tag === "VElement") {
-          warnIfInvalidNesting(parent.type, child.type);
+          yield* warnIfInvalidNesting(parent.type, child.type);
         }
         parent.children.push(child);
         // Track parent reference for slot markers
diff --git a/packages/dom/src/Render/validateNesting.test.ts b/packages/dom/src/Render/validateNesting.test.ts
index f6626e0..ce7c4a3 100644
--- a/packages/dom/src/Render/validateNesting.test.ts
+++ b/packages/dom/src/Render/validateNesting.test.ts
@@ -1,7 +1,13 @@
+import { Effect } from "effect";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import { checkNesting, warnIfInvalidNesting } from "./validateNesting.js";
 
+/** Helper: warnIfInvalidNesting returns Effect<void>; run it synchronously. */
+const warn = (parent: string | undefined, child: string | undefined): void => {
+  Effect.runSync(warnIfInvalidNesting(parent, child));
+};
+
 describe("checkNesting", () => {
   it("flags a paragraph nested inside a paragraph", () => {
     expect(checkNesting("p", "p")).toMatch(/<p> inside <p>/);
@@ -56,36 +62,36 @@ describe("warnIfInvalidNesting", () => {
   });
 
   it("emits a console.warn on invalid nesting", () => {
-    warnIfInvalidNesting("p", "div");
+    warn("p", "div");
     expect(warnSpy).toHaveBeenCalledTimes(1);
     expect(warnSpy.mock.calls[0][0]).toMatch(/\[@effex\/dom\]/);
     expect(warnSpy.mock.calls[0][0]).toMatch(/<div> inside <p>/);
   });
 
   it("is silent on valid nesting", () => {
-    warnIfInvalidNesting("div", "p");
-    warnIfInvalidNesting("ul", "li");
+    warn("div", "p");
+    warn("ul", "li");
     expect(warnSpy).not.toHaveBeenCalled();
   });
 
   it("is silent when either arg is missing (text nodes, comments, etc.)", () => {
-    warnIfInvalidNesting(undefined, "div");
-    warnIfInvalidNesting("p", undefined);
-    warnIfInvalidNesting(undefined, undefined);
+    warn(undefined, "div");
+    warn("p", undefined);
+    warn(undefined, undefined);
     expect(warnSpy).not.toHaveBeenCalled();
   });
 
   it("only warns once per parent-child pair (across calls)", () => {
     // The module-level Set caches across tests, so use a distinct pair that
     // no other test in this file exercises for warning-count assertions.
-    warnIfInvalidNesting("form", "form");
-    warnIfInvalidNesting("form", "form");
-    warnIfInvalidNesting("form", "form");
+    warn("form", "form");
+    warn("form", "form");
+    warn("form", "form");
     expect(warnSpy).toHaveBeenCalledTimes(1);
   });
 
   it("normalizes tag case", () => {
-    warnIfInvalidNesting("BUTTON", "INPUT");
+    warn("BUTTON", "INPUT");
     expect(warnSpy).toHaveBeenCalledTimes(1);
     expect(warnSpy.mock.calls[0][0]).toMatch(/<input> inside <button>/);
   });
diff --git a/packages/dom/src/Render/validateNesting.ts b/packages/dom/src/Render/validateNesting.ts
index 41614f7..e086ec2 100644
--- a/packages/dom/src/Render/validateNesting.ts
+++ b/packages/dom/src/Render/validateNesting.ts
@@ -1,3 +1,5 @@
+import { Console, Effect } from "effect";
+
 /**
  * Compile-time HTML nesting validator.
  *
@@ -102,24 +104,25 @@ export const checkNesting = (parent: string, child: string): string | null => {
 const warned = new Set<string>();
 
 /**
- * Report an invalid nesting via `console.warn`, once per parent-child pair
- * per process. Safe to call unconditionally — the check is cheap and the
- * warning only fires on real bugs. No-ops in environments without `console`.
+ * Report an invalid nesting via Effect's {@link Console.warn}, once per
+ * parent-child pair per process. Returns `Effect.void` when the pair is
+ * valid or has already been warned about, so callers can `yield*` it
+ * unconditionally without branching.
+ *
+ * Uses Effect's Console service (not raw `console.warn`) to stay idiomatic
+ * with the rest of the codebase and to let tests swap the sink via Layer.
  */
 export const warnIfInvalidNesting = (
   parent: string | undefined,
   child: string | undefined,
-): void => {
-  if (!parent || !child) return;
+): Effect.Effect<void> => {
+  if (!parent || !child) return Effect.void;
   const p = parent.toLowerCase();
   const c = child.toLowerCase();
   const key = `${p}>${c}`;
-  if (warned.has(key)) return;
+  if (warned.has(key)) return Effect.void;
   const message = checkNesting(p, c);
-  if (!message) return;
+  if (!message) return Effect.void;
   warned.add(key);
-  if (typeof console !== "undefined") {
-    // eslint-disable-next-line no-console
-    console.warn(`[@effex/dom] ${message}`);
-  }
+  return Console.warn(`[@effex/dom] ${message}`);
 };