diff --git a/.changeset/action-param-visible.md b/.changeset/action-param-visible.md
new file mode 100644
index 000000000..7c61fb6cd
--- /dev/null
+++ b/.changeset/action-param-visible.md
@@ -0,0 +1,13 @@
+---
+"@object-ui/core": patch
+"@object-ui/app-shell": patch
+---
+
+Action params support a `visible` CEL predicate — the param dialog omits a param
+when it evaluates false, against the same scope as action `visible` (features /
+user / app / data). Fixes the create-user form offering a **Phone Number** field
+the default backend rejects ("Phone numbers require the phoneNumber auth plugin"):
+paired with the framework gating that param on `features.phoneNumber`, the form
+now follows the plugin — no phone field unless the opt-in phoneNumber auth plugin
+is loaded. `filterVisibleParams` is exported + unit-tested (feature-off hides,
+feature-on shows, malformed predicate fails open).
diff --git a/packages/app-shell/src/views/ActionParamDialog.test.tsx b/packages/app-shell/src/views/ActionParamDialog.test.tsx
new file mode 100644
index 000000000..07caee7b9
--- /dev/null
+++ b/packages/app-shell/src/views/ActionParamDialog.test.tsx
@@ -0,0 +1,65 @@
+/**
+ * ObjectUI
+ * Copyright (c) 2024-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * filterVisibleParams — action params gated by a `visible` CEL predicate
+ * (evaluated against the features/user/app/data scope). Fixes the create-user
+ * form offering a `phoneNumber` field the default backend rejects: the param is
+ * `visible: 'features.phoneNumber == true'`, so it's hidden unless the opt-in
+ * phoneNumber auth plugin is loaded.
+ */
+import { describe, it, expect } from 'vitest';
+import type { ActionParamDef } from '@object-ui/core';
+import { filterVisibleParams } from './ActionParamDialog';
+
+const p = (name: string, visible?: string): ActionParamDef => ({
+  name,
+  label: name,
+  type: 'text',
+  ...(visible ? { visible } : {}),
+});
+
+describe('filterVisibleParams', () => {
+  it('keeps params that have no visible predicate', () => {
+    const params = [p('email'), p('name')];
+    expect(filterVisibleParams(params, {}).map((x) => x.name)).toEqual(['email', 'name']);
+  });
+
+  it('hides the phoneNumber param when features.phoneNumber is false', () => {
+    const params = [p('email'), p('phoneNumber', 'features.phoneNumber == true'), p('name')];
+    const out = filterVisibleParams(params, { features: { phoneNumber: false } });
+    expect(out.map((x) => x.name)).toEqual(['email', 'name']);
+  });
+
+  it('shows the phoneNumber param when features.phoneNumber is true', () => {
+    const params = [p('email'), p('phoneNumber', 'features.phoneNumber == true'), p('name')];
+    const out = filterVisibleParams(params, { features: { phoneNumber: true } });
+    expect(out.map((x) => x.name)).toEqual(['email', 'phoneNumber', 'name']);
+  });
+
+  it('hides a feature-gated param when the flag is absent (conservative)', () => {
+    const params = [p('phoneNumber', 'features.phoneNumber == true')];
+    expect(filterVisibleParams(params, { features: {} })).toEqual([]);
+  });
+
+  it('defaults to visible when the predicate is malformed (fail-open)', () => {
+    const params = [p('x', 'this is ((( not valid')];
+    expect(filterVisibleParams(params, {}).map((x) => x.name)).toEqual(['x']);
+  });
+
+  it('handles the normalized {dialect, source} form the spec serializes to', () => {
+    // The framework's ExpressionInputSchema normalizes the authored string to
+    // `{ dialect: 'cel', source: '...' }`, so the served param carries the object
+    // form — the evaluator unwraps `.source`, so gating still works.
+    const params: ActionParamDef[] = [
+      { name: 'phoneNumber', label: 'Phone', type: 'text', visible: { dialect: 'cel', source: 'features.phoneNumber == true' } as any },
+    ];
+    expect(filterVisibleParams(params, { features: { phoneNumber: false } })).toEqual([]);
+    expect(filterVisibleParams(params, { features: { phoneNumber: true } }).map((x) => x.name)).toEqual(['phoneNumber']);
+  });
+});
diff --git a/packages/app-shell/src/views/ActionParamDialog.tsx b/packages/app-shell/src/views/ActionParamDialog.tsx
index f86f349ec..c5281c017 100644
--- a/packages/app-shell/src/views/ActionParamDialog.tsx
+++ b/packages/app-shell/src/views/ActionParamDialog.tsx
@@ -10,7 +10,7 @@
  * Returns collected param values or null on cancel.
  */
 
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useMemo } from 'react';
 import {
   Dialog,
   DialogContent,
@@ -31,6 +31,8 @@ import {
 } from '@object-ui/components';
 import { useObjectTranslation, pickLocalized } from '@object-ui/i18n';
 import type { ActionParamDef } from '@object-ui/core';
+import { ExpressionEvaluator } from '@object-ui/core';
+import { usePredicateScope } from '@object-ui/react';
 import { LookupField } from '@object-ui/fields';
 
 export interface ParamDialogState {
@@ -49,16 +51,46 @@ interface ActionParamDialogProps {
   onOpenChange: (open: boolean) => void;
 }
 
+/**
+ * Filter action params by their optional `visible` CEL predicate, evaluated
+ * against the expression scope (features / user / app / data). A param with no
+ * predicate is always kept; a predicate that throws defaults to visible (mirrors
+ * the ExpressionProvider "auth config not loaded yet → visible" contract). Pure
+ * + exported so the gating is unit-testable without the dialog render tree.
+ */
+export function filterVisibleParams(
+  params: ActionParamDef[],
+  scope: Record<string, any>,
+): ActionParamDef[] {
+  const evaluator = new ExpressionEvaluator(scope);
+  return params.filter((p) => {
+    if (!p.visible) return true;
+    try {
+      return evaluator.evaluateCondition(p.visible);
+    } catch {
+      return true;
+    }
+  });
+}
+
 export function ActionParamDialog({ state, onOpenChange }: ActionParamDialogProps) {
   const { t, language } = useObjectTranslation();
   const [values, setValues] = useState<Record<string, any>>({});
   const [errors, setErrors] = useState<Record<string, boolean>>({});
 
+  // A param may carry a `visible` predicate (CEL) gating it on the same scope as
+  // action visibility (features / user / app / data) — e.g. `create_user`'s
+  // phoneNumber param is `features.phoneNumber == true`, so the form never offers
+  // a field the backend rejects. Absent = visible; a predicate that errors
+  // defaults to visible (mirrors the ExpressionProvider "config not loaded" note).
+  const scope = usePredicateScope();
+  const visibleParams = useMemo(() => filterVisibleParams(state.params, scope), [state.params, scope]);
+
   // Reset values when params change
   useEffect(() => {
     if (state.open) {
       const defaults: Record<string, any> = {};
-      for (const param of state.params) {
+      for (const param of visibleParams) {
         if (param.defaultValue !== undefined) {
           defaults[param.name] = param.defaultValue;
         }
@@ -66,7 +98,7 @@ export function ActionParamDialog({ state, onOpenChange }: ActionParamDialogProp
       setValues(defaults);
       setErrors({});
     }
-  }, [state.open, state.params]);
+  }, [state.open, visibleParams]);
 
   const isMissingValue = (value: unknown): boolean => {
     if (value === undefined || value === null) return true;
@@ -80,7 +112,7 @@ export function ActionParamDialog({ state, onOpenChange }: ActionParamDialogProp
   const handleSubmit = () => {
     // Validate required fields
     const newErrors: Record<string, boolean> = {};
-    for (const param of state.params) {
+    for (const param of visibleParams) {
       if (param.required && isMissingValue(values[param.name])) {
         newErrors[param.name] = true;
       }
@@ -116,7 +148,7 @@ export function ActionParamDialog({ state, onOpenChange }: ActionParamDialogProp
         </DialogHeader>
 
         <div className="grid gap-4 py-4">
-          {state.params.map((rawParam) => {
+          {visibleParams.map((rawParam) => {
             const param = {
               ...rawParam,
               label: pickLocalized(rawParam.label, language),
diff --git a/packages/core/src/actions/ActionRunner.ts b/packages/core/src/actions/ActionRunner.ts
index 0f49d83f6..7fdf4f002 100644
--- a/packages/core/src/actions/ActionRunner.ts
+++ b/packages/core/src/actions/ActionRunner.ts
@@ -261,6 +261,14 @@ export interface ActionParamDef {
   helpText?: string;
   placeholder?: string;
   validation?: string;
+  /**
+   * Visibility predicate (CEL) evaluated against the same scope as action
+   * `visible` (`current_user` / `app` / `data` / `features`). When it evaluates
+   * false the param dialog omits this param — used to hide a param the backend
+   * only accepts under an opt-in capability (e.g. `create_user.phoneNumber`
+   * gated on `features.phoneNumber`). Absent = always visible.
+   */
+  visible?: string;
 
   // ── Lookup-/reference-type metadata ───────────────────────────────
   // Populated by `resolveActionParams()` when a field-backed param resolves