diff --git a/app/RSpade/Core/Polymorphic_Field_Helper.php b/app/RSpade/Core/Polymorphic_Field_Helper.php
new file mode 100755
index 000000000..d887779b2
--- /dev/null
+++ b/app/RSpade/Core/Polymorphic_Field_Helper.php
@@ -0,0 +1,187 @@
+<?php
+
+namespace App\RSpade\Core;
+
+/**
+ * Polymorphic Field Helper
+ *
+ * Handles JSON-encoded polymorphic field values from form components.
+ * Provides parsing, validation, and security checks for polymorphic relationships.
+ *
+ * Polymorphic fields are submitted as JSON: {"model":"Contact_Model","id":123}
+ * This class parses that JSON and validates the model type against a whitelist.
+ *
+ * Usage in controllers:
+ *
+ *     use App\RSpade\Core\Polymorphic_Field_Helper;
+ *
+ *     // Parse and validate a polymorphic field
+ *     $eventable = Polymorphic_Field_Helper::parse($params['eventable'], [
+ *         Contact_Model::class,
+ *         Project_Model::class,
+ *     ]);
+ *
+ *     // Quick validation with error message
+ *     $error = $eventable->validate('Please select an entity');
+ *     if ($error) {
+ *         $errors['eventable'] = $error;
+ *     }
+ *
+ *     // Or check states manually
+ *     if ($eventable->is_empty()) {
+ *         $errors['eventable'] = 'Please select a contact or project';
+ *     } elseif (!$eventable->is_valid()) {
+ *         $errors['eventable'] = 'Invalid entity type selected';
+ *     }
+ *
+ *     // Use the values
+ *     $model->eventable_type = $eventable->model;
+ *     $model->eventable_id = $eventable->id;
+ */
+#[Instantiatable]
+class Polymorphic_Field_Helper
+{
+    /**
+     * The model class name (e.g., "Contact_Model")
+     */
+    public ?string $model = null;
+
+    /**
+     * The entity ID
+     */
+    public ?int $id = null;
+
+    /**
+     * Whether any value was provided in the input
+     */
+    private bool $was_provided = false;
+
+    /**
+     * Whether the provided model type is in the allowed list
+     */
+    private bool $model_allowed = false;
+
+    /**
+     * List of allowed model basenames for error messages
+     */
+    private array $allowed_models = [];
+
+    /**
+     * Parse a JSON-encoded polymorphic field value
+     *
+     * @param string|null $json_value The JSON string from form submission (e.g., '{"model":"Contact_Model","id":123}')
+     * @param array $allowed_model_classes Array of allowed model class names (use Model::class syntax)
+     * @return self
+     */
+    public static function parse(?string $json_value, array $allowed_model_classes): self
+    {
+        $instance = new self();
+        $instance->allowed_models = array_map(fn($class) => class_basename($class), $allowed_model_classes);
+
+        if (empty($json_value)) {
+            return $instance;
+        }
+
+        $decoded = json_decode($json_value, true);
+        if (!is_array($decoded)) {
+            return $instance;
+        }
+
+        $instance->was_provided = true;
+
+        if (!empty($decoded['model']) && !empty($decoded['id'])) {
+            $instance->model = $decoded['model'];
+            $instance->id = (int) $decoded['id'];
+            $instance->model_allowed = in_array($instance->model, $instance->allowed_models);
+        }
+
+        return $instance;
+    }
+
+    /**
+     * Check if no value was provided (empty string or null)
+     */
+    public function is_empty(): bool
+    {
+        return !$this->was_provided || $this->model === null || $this->id === null;
+    }
+
+    /**
+     * Check if the value is valid (provided and model type is allowed)
+     */
+    public function is_valid(): bool
+    {
+        return !$this->is_empty() && $this->model_allowed;
+    }
+
+    /**
+     * Check if a value was provided but is invalid (wrong model type or malformed)
+     */
+    public function is_invalid(): bool
+    {
+        return $this->was_provided && !$this->is_valid();
+    }
+
+    /**
+     * Get the model class name (e.g., "Contact_Model")
+     */
+    public function get_model(): ?string
+    {
+        return $this->model;
+    }
+
+    /**
+     * Get the entity ID
+     */
+    public function get_id(): ?int
+    {
+        return $this->id;
+    }
+
+    /**
+     * Get allowed model names for error messages
+     */
+    public function get_allowed_models(): array
+    {
+        return $this->allowed_models;
+    }
+
+    /**
+     * Validate and return error message if invalid, null if valid
+     *
+     * Use this for required polymorphic fields.
+     *
+     * @param string $empty_message Message when field is empty/missing
+     * @param string $invalid_message Message when model type is not allowed
+     * @return string|null Error message or null if valid
+     */
+    public function validate(string $empty_message, string $invalid_message = 'Invalid entity type selected'): ?string
+    {
+        if ($this->is_empty()) {
+            return $empty_message;
+        }
+        if (!$this->model_allowed) {
+            return $invalid_message;
+        }
+        return null;
+    }
+
+    /**
+     * Validate for optional field (only invalid if provided but wrong type)
+     *
+     * Use this for optional polymorphic fields where empty is acceptable.
+     *
+     * @param string $invalid_message Message when model type is not allowed
+     * @return string|null Error message or null if valid/empty
+     */
+    public function validate_optional(string $invalid_message = 'Invalid entity type selected'): ?string
+    {
+        if ($this->is_empty()) {
+            return null; // Empty is OK for optional fields
+        }
+        if (!$this->model_allowed) {
+            return $invalid_message;
+        }
+        return null;
+    }
+}
diff --git a/app/RSpade/man/polymorphic.txt b/app/RSpade/man/polymorphic.txt
new file mode 100755
index 000000000..3a77c6451
--- /dev/null
+++ b/app/RSpade/man/polymorphic.txt
@@ -0,0 +1,256 @@
+POLYMORPHIC(7)                 RSX Framework Manual                POLYMORPHIC(7)
+
+NAME
+    polymorphic - JSON-encoded polymorphic field handling
+
+SYNOPSIS
+    Server-side:
+        use App\RSpade\Core\Polymorphic_Field_Helper;
+
+        $field = Polymorphic_Field_Helper::parse($params['fieldname'], [
+            Contact_Model::class,
+            Project_Model::class,
+        ]);
+
+        if ($error = $field->validate('Please select an entity')) {
+            $errors['fieldname'] = $error;
+        }
+
+        $model->poly_type = $field->model;
+        $model->poly_id = $field->id;
+
+    Client-side (form input value format):
+        {"model":"Contact_Model","id":123}
+
+DESCRIPTION
+    Polymorphic fields allow a single database relationship to reference
+    multiple model types. For example, an Activity can be related to either
+    a Contact or a Project. This document describes the standard pattern for
+    handling polymorphic fields in RSX applications.
+
+    The Problem
+
+        Traditional form handling passes polymorphic data as separate fields:
+
+            eventable_type=Contact_Model
+            eventable_id=123
+
+        This approach has issues:
+        - Requires custom form submission handlers to inject hidden fields
+        - Field naming is inconsistent (type vs _type, id vs _id)
+        - No standard validation pattern
+        - Security validation (allowed model types) is ad-hoc
+
+    The Solution
+
+        Polymorphic fields are submitted as a single JSON-encoded value:
+
+            eventable={"model":"Contact_Model","id":123}
+
+        Benefits:
+        - Single field to validate
+        - Standard val() getter/setter pattern on client
+        - Polymorphic_Field_Helper handles parsing and security validation
+        - Clean, reusable code on both client and server
+
+SERVER-SIDE USAGE
+    Polymorphic_Field_Helper Class
+
+        Location: App\RSpade\Core\Polymorphic_Field_Helper
+
+        Parse a field value:
+
+            use App\RSpade\Core\Polymorphic_Field_Helper;
+
+            $eventable = Polymorphic_Field_Helper::parse($params['eventable'], [
+                Contact_Model::class,
+                Project_Model::class,
+            ]);
+
+        The second argument is the whitelist of allowed model classes. Always
+        use Model::class syntax - never hardcode model name strings.
+
+    Validation Methods
+
+        Required field validation:
+
+            if ($error = $eventable->validate('Please select an entity')) {
+                $errors['eventable'] = $error;
+            }
+
+        Optional field validation:
+
+            if ($error = $parent->validate_optional('Invalid parent type')) {
+                $errors['parent'] = $error;
+            }
+
+    Accessing Values
+
+        After validation:
+
+            $model->eventable_type = $eventable->model;  // "Contact_Model"
+            $model->eventable_id = $eventable->id;       // 123
+
+        For optional fields, id will be null if not provided:
+
+            $model->parent_id = $parent->id;  // null or integer
+
+    State Checking Methods
+
+            $field->is_empty()    // No value provided
+            $field->is_valid()    // Value provided and model type allowed
+            $field->is_invalid()  // Value provided but model type not allowed
+
+CLIENT-SIDE IMPLEMENTATION
+    Building a Polymorphic Picker Component
+
+        To create a picker for polymorphic fields, build a component that:
+
+        1. Maintains a hidden input with the JSON-encoded value
+        2. Implements val() to get/set as {model: 'Model_Name', id: number}
+        3. Syncs the hidden input on every change
+        4. Handles pre-load value setting (value set before options loaded)
+
+    Hidden Input Pattern
+
+        The component template should include a hidden input:
+
+            <input type="hidden" $sid="hidden_value" name="<%= this.args.name %>" />
+
+        On value change, sync to hidden input as JSON:
+
+            _sync_hidden_value() {
+                const $hidden = this.$sid('hidden_value');
+                if (this._value && this._value.model && this._value.id) {
+                    $hidden.val(JSON.stringify(this._value));
+                } else {
+                    $hidden.val('');
+                }
+            }
+
+    val() Implementation
+
+        The val() method should work before and after component loads:
+
+            val(value) {
+                if (arguments.length === 0) {
+                    // Getter
+                    return this._value || this._pending_value || null;
+                }
+
+                // Setter
+                const parsed = value ? {model: value.model, id: parseInt(value.id)} : null;
+
+                if (this.data.loading) {
+                    this._pending_value = parsed;
+                    this._value = parsed;
+                    this._sync_hidden_value();
+                } else {
+                    this._value = parsed;
+                    this._apply_to_ui();
+                    this._sync_hidden_value();
+                }
+            }
+
+    Using Tom Select
+
+        For searchable dropdowns, use Tom Select with a compound value format:
+
+            // Compound value: "Model_Name:id"
+            valueField: 'compound_value',
+
+            onChange: function(compound_value) {
+                if (!compound_value) {
+                    that._value = null;
+                } else {
+                    const parts = compound_value.split(':');
+                    that._value = {model: parts[0], id: parseInt(parts[1])};
+                }
+                that._sync_hidden_value();
+            }
+
+        Add options with the compound format:
+
+            all_options.push({
+                compound_value: 'Contact_Model:' + contact.id,
+                model: 'Contact_Model',
+                id: contact.id,
+                name: contact.name,
+            });
+
+COMPLETE EXAMPLE
+    Controller
+
+        use App\RSpade\Core\Polymorphic_Field_Helper;
+
+        #[Ajax_Endpoint]
+        public static function save(Request $request, array $params = [])
+        {
+            $eventable = Polymorphic_Field_Helper::parse($params['eventable'] ?? null, [
+                Contact_Model::class,
+                Project_Model::class,
+            ]);
+
+            $errors = [];
+
+            if ($error = $eventable->validate('Please select an entity')) {
+                $errors['eventable'] = $error;
+            }
+
+            if (!empty($errors)) {
+                return response_form_error('Please correct errors', $errors);
+            }
+
+            $activity = new Activity_Model();
+            $activity->eventable_type = $eventable->model;
+            $activity->eventable_id = $eventable->id;
+            $activity->save();
+
+            return ['success' => true];
+        }
+
+DATABASE SCHEMA
+    Polymorphic relationships use two columns:
+
+        $table->string('eventable_type');
+        $table->unsignedBigInteger('eventable_id');
+
+    The type column stores the model class basename (e.g., "Contact_Model").
+
+SECURITY CONSIDERATIONS
+    Model Type Validation
+
+        CRITICAL: Always validate that submitted model types are in the allowed
+        list. Attackers could submit arbitrary model names to exploit the
+        polymorphic relationship.
+
+        The Polymorphic_Field_Helper enforces this automatically:
+
+            // Only Contact_Model and Project_Model are accepted
+            $eventable = Polymorphic_Field_Helper::parse($params['eventable'], [
+                Contact_Model::class,
+                Project_Model::class,
+            ]);
+
+            // Submitting {"model":"User_Model","id":1} will fail validation
+            $eventable->is_valid();  // false
+
+    Use Model::class, Not Strings
+
+        Always use the ::class constant to specify allowed models:
+
+            // CORRECT - uses class constant
+            Polymorphic_Field_Helper::parse($value, [Contact_Model::class]);
+
+            // WRONG - hardcoded string
+            Polymorphic_Field_Helper::parse($value, ['Contact_Model']);
+
+        Using ::class ensures:
+        - IDE autocompletion and refactoring support
+        - Compile-time error if class doesn't exist
+        - Consistent naming with actual class names
+
+SEE ALSO
+    form_conventions(7), ajax_error_handling(7)
+
+RSX Framework                     2025-12-23                     POLYMORPHIC(7)
diff --git a/docs/CLAUDE.dist.md b/docs/CLAUDE.dist.md
index 69f82f2f3..3b4dbfeee 100644
--- a/docs/CLAUDE.dist.md
+++ b/docs/CLAUDE.dist.md
@@ -924,6 +924,30 @@ public static function save(Request $request, array $params = []) {
 
 Details: `php artisan rsx:man form_conventions`
 
+### Polymorphic Form Fields
+
+For fields that can reference multiple model types (e.g., an Activity linked to either a Contact or Project), use JSON-encoded polymorphic values.
+
+```php
+use App\RSpade\Core\Polymorphic_Field_Helper;
+
+$eventable = Polymorphic_Field_Helper::parse($params['eventable'], [
+    Contact_Model::class,
+    Project_Model::class,
+]);
+
+if ($error = $eventable->validate('Please select an entity')) {
+    $errors['eventable'] = $error;
+}
+
+$model->eventable_type = $eventable->model;
+$model->eventable_id = $eventable->id;
+```
+
+Client submits: `{"model":"Contact_Model","id":123}`. Always use `Model::class` for the whitelist.
+
+Details: `php artisan rsx:man polymorphic`
+
 ---
 
 ## MODALS