diff --git a/packages/core/src/primitives/create-disclosure-state.ts b/packages/core/src/primitives/create-disclosure-state.ts
new file mode 100644
index 0000000..ae251e0
--- /dev/null
+++ b/packages/core/src/primitives/create-disclosure-state.ts
@@ -0,0 +1,37 @@
+import type { Accessor } from "solid-js";
+import { createControllableSignal } from "./create-controllable-signal";
+
+export interface CreateDisclosureStateOptions {
+  open?: boolean;
+  defaultOpen?: boolean;
+  onOpenChange?: (open: boolean) => void;
+}
+
+export interface DisclosureState {
+  isOpen: Accessor<boolean>;
+  open: () => void;
+  close: () => void;
+  toggle: () => void;
+}
+
+/**
+ * Shared open/close state for all disclosure components (Dialog, Popover,
+ * Tooltip, Collapsible, etc.). Wraps createControllableSignal with
+ * convenience open/close/toggle methods.
+ */
+export function createDisclosureState(
+  options: CreateDisclosureStateOptions,
+): DisclosureState {
+  const [isOpen, setIsOpen] = createControllableSignal<boolean>({
+    value: () => options.open,
+    defaultValue: () => options.defaultOpen ?? false,
+    onChange: options.onOpenChange,
+  });
+
+  return {
+    isOpen,
+    open: () => setIsOpen(true),
+    close: () => setIsOpen(false),
+    toggle: () => setIsOpen(!isOpen()),
+  };
+}
diff --git a/packages/core/tests/primitives/create-disclosure-state.test.ts b/packages/core/tests/primitives/create-disclosure-state.test.ts
new file mode 100644
index 0000000..820b023
--- /dev/null
+++ b/packages/core/tests/primitives/create-disclosure-state.test.ts
@@ -0,0 +1,76 @@
+import { createRoot } from "solid-js";
+import { describe, expect, it, vi } from "vitest";
+import { createDisclosureState } from "../../src/primitives/create-disclosure-state";
+
+describe("createDisclosureState", () => {
+  it("starts closed by default", () => {
+    createRoot((dispose) => {
+      const state = createDisclosureState({});
+      expect(state.isOpen()).toBe(false);
+      dispose();
+    });
+  });
+
+  it("respects defaultOpen", () => {
+    createRoot((dispose) => {
+      const state = createDisclosureState({ defaultOpen: true });
+      expect(state.isOpen()).toBe(true);
+      dispose();
+    });
+  });
+
+  it("open() sets state to true", () => {
+    createRoot((dispose) => {
+      const state = createDisclosureState({});
+      state.open();
+      expect(state.isOpen()).toBe(true);
+      dispose();
+    });
+  });
+
+  it("close() sets state to false", () => {
+    createRoot((dispose) => {
+      const state = createDisclosureState({ defaultOpen: true });
+      state.close();
+      expect(state.isOpen()).toBe(false);
+      dispose();
+    });
+  });
+
+  it("toggle() flips state", () => {
+    createRoot((dispose) => {
+      const state = createDisclosureState({});
+      state.toggle();
+      expect(state.isOpen()).toBe(true);
+      state.toggle();
+      expect(state.isOpen()).toBe(false);
+      dispose();
+    });
+  });
+
+  it("calls onOpenChange when state changes", () => {
+    createRoot((dispose) => {
+      const onChange = vi.fn();
+      const state = createDisclosureState({ onOpenChange: onChange });
+      state.open();
+      expect(onChange).toHaveBeenCalledWith(true);
+      state.close();
+      expect(onChange).toHaveBeenCalledWith(false);
+      dispose();
+    });
+  });
+
+  it("respects controlled open prop", () => {
+    createRoot((dispose) => {
+      const state = createDisclosureState({ open: true });
+      expect(state.isOpen()).toBe(true);
+      // Calling close() fires onChange but does not change internal state
+      const onChange = vi.fn();
+      const controlled = createDisclosureState({ open: true, onOpenChange: onChange });
+      controlled.close();
+      expect(controlled.isOpen()).toBe(true); // still controlled
+      expect(onChange).toHaveBeenCalledWith(false);
+      dispose();
+    });
+  });
+});