diff --git a/react-openapi/index.ts b/react-openapi/index.ts
index 3b5f543..fb73fa2 100644
--- a/react-openapi/index.ts
+++ b/react-openapi/index.ts
@@ -8,5 +8,7 @@ export { SseStreamView } from "./src/components/SseStreamView";
 export { SseConnectionStatus } from "./src/components/SseConnectionStatus";
 export { getApi } from "./src/hooks/useApi";
 export { useItemSse } from "./src/hooks/useItemSse";
+export { sanitizePayload } from "./src/utils/sanitize-payload";
+export type { FkResolver } from "./src/utils/sanitize-payload";
 export type { FilterComponentProps } from "./src/context/useResource";
 export type { SpecConfiguration, ResourceConfig, FieldConfig, FKFieldConfig, ResourceRelationship } from "./src/types";
diff --git a/react-openapi/src/components/fields/FormFieldRenderer.tsx b/react-openapi/src/components/fields/FormFieldRenderer.tsx
index 425c3f9..6d9616e 100644
--- a/react-openapi/src/components/fields/FormFieldRenderer.tsx
+++ b/react-openapi/src/components/fields/FormFieldRenderer.tsx
@@ -1,5 +1,5 @@
 import React from "react";
-import { TextField } from "@mui/material";
+import { TextField, Chip, Box } from "@mui/material";
 import type { FieldConfig } from "../../types";
 import { StringField } from "./renderers/StringField";
 import { NumberField } from "./renderers/NumberField";
@@ -139,6 +139,32 @@ export function FormFieldRenderer({ field, value, onChange, error, fkOptions, fk
     );
   }
 
+  if (field.type === "array" && !field.fk) {
+    return (
+      <Box>
+        <Chip
+          label={`${field.label} (${Array.isArray(value) ? value.length : 0})`}
+          size="small"
+          color="default"
+          variant="outlined"
+        />
+      </Box>
+    );
+  }
+
+  if (field.type === "object" && !field.fk) {
+    return (
+      <Box>
+        <Chip
+          label={field.label}
+          size="small"
+          color="default"
+          variant="outlined"
+        />
+      </Box>
+    );
+  }
+
   return (
     <StringField
       field={field}
diff --git a/react-openapi/src/components/fields/renderers/DiscriminatorField.tsx b/react-openapi/src/components/fields/renderers/DiscriminatorField.tsx
index d5dad58..bc6ce76 100644
--- a/react-openapi/src/components/fields/renderers/DiscriminatorField.tsx
+++ b/react-openapi/src/components/fields/renderers/DiscriminatorField.tsx
@@ -15,13 +15,21 @@ export function DiscriminatorField({ field, value, onChange, error }: Props) {
   const discProp = field.discriminatorProperty ?? "type";
   const currentType = value?.[discProp] ?? "";
 
+  function defaultFieldValue(field: FieldConfig): any {
+    if (field.enumValues) return field.enumValues[0];
+    if (field.isArray) return [];
+    if (field.type === "object") return {};
+    if (field.type === "number" || field.type === "integer") return 0;
+    return null;
+  }
+
   const handleTypeChange = useCallback((e: any) => {
     const newType = e.target.value;
     const option = options.find((o) => o.value === newType);
     const newValue: Record<string, any> = { [discProp]: newType };
     if (option) {
       for (const f of option.fields) {
-        newValue[f.name] = f.enumValues?.[0] ?? f.type === "number" ? 0 : f.type === "integer" ? 0 : "";
+        newValue[f.name] = defaultFieldValue(f);
       }
     }
     onChange(newValue);
diff --git a/react-openapi/src/components/fields/renderers/JsonField.tsx b/react-openapi/src/components/fields/renderers/JsonField.tsx
index 8fd34a9..14aefb9 100644
--- a/react-openapi/src/components/fields/renderers/JsonField.tsx
+++ b/react-openapi/src/components/fields/renderers/JsonField.tsx
@@ -243,6 +243,10 @@ function buildDefaultShape(fields: FieldConfig[], schemas: Record<string, any>):
       const refSchemaObj = schemas[f.refSchema!];
       const nestedFields = refSchemaObj ? extractFields(f.refSchema!, refSchemaObj, schemas) : [];
       shape[f.name] = f.isArray ? [] : buildDefaultShape(nestedFields, schemas);
+    } else if (f.isArray) {
+      shape[f.name] = [];
+    } else if (f.type === "object") {
+      shape[f.name] = {};
     } else {
       shape[f.name] = null;
     }
@@ -254,7 +258,7 @@ function initEditValue(value: any, field: FieldConfig, schemas: Record<string, a
   if (field.isArray) {
     return value ? value.map((item: any) => ({ ...item })) : [];
   }
-  if (value && typeof value === "object") {
+  if (value != null && value !== "" && typeof value === "object") {
     return { ...value };
   }
   return buildDefaultShape(
diff --git a/react-openapi/src/context/useResource.tsx b/react-openapi/src/context/useResource.tsx
index 67b29e7..4e9d7de 100644
--- a/react-openapi/src/context/useResource.tsx
+++ b/react-openapi/src/context/useResource.tsx
@@ -4,6 +4,7 @@ import DoneIcon from "@mui/icons-material/Done";
 import type { ResourceConfig, ParsedListResponse, FieldConfig } from "../types";
 import { useAppContext } from "./AppContext";
 import { getApi } from "../hooks/useApi";
+import { sanitizePayload } from "../utils/sanitize-payload";
 import { StringField } from "../components/fields/renderers/StringField";
 import { NumberField } from "../components/fields/renderers/NumberField";
 import { DateField } from "../components/fields/renderers/DateField";
@@ -588,7 +589,7 @@ function buildFilterComponent(field: FieldConfig, resourceName: string): React.F
 }
 
 export function useResource(resourceName: string): UseResourceReturn {
-  const { resources } = useAppContext();
+  const { resources, schemas } = useAppContext();
   const resource = resources.find((r) => r.name === resourceName);
 
   const [state, setState] = useState<ResourceState>({ loading: false, error: null });
@@ -661,6 +662,18 @@ export function useResource(resourceName: string): UseResourceReturn {
     [rPath, setLoading, setError]
   );
 
+  const resolveFk = useCallback(async (resourceName: string, id: any) => {
+    const targetRes = resources.find((r) => r.name === resourceName);
+    if (!targetRes) return id;
+    try {
+      const api = getApi();
+      const res = await api.get(`${targetRes.path}/${id}`);
+      return res.data;
+    } catch {
+      return id;
+    }
+  }, [resources]);
+
   const create = useCallback(
     async (data: any): Promise<any> => {
       if (!rPath) throw new Error(`Resource "${resourceName}" not found yet`);
@@ -668,7 +681,10 @@ export function useResource(resourceName: string): UseResourceReturn {
       setError(null);
       try {
         const api = getApi();
-        const res = await api.post(rPath, data);
+        const sanitized = rFields && schemas
+          ? await sanitizePayload(data, rFields, schemas, resolveFk)
+          : data;
+        const res = await api.post(rPath, sanitized);
         return res.data;
       } catch (e: any) {
         setError(parseError(e));
@@ -677,7 +693,7 @@ export function useResource(resourceName: string): UseResourceReturn {
         setLoading(false);
       }
     },
-    [rPath, setLoading, setError]
+    [rPath, rFields, schemas, resolveFk, setLoading, setError]
   );
 
   const update = useCallback(
@@ -687,8 +703,11 @@ export function useResource(resourceName: string): UseResourceReturn {
       setError(null);
       try {
         const api = getApi();
+        const sanitized = rFields && schemas
+          ? await sanitizePayload(data, rFields, schemas, resolveFk)
+          : data;
         const method = rUpdateMethod ?? "put";
-        const res = await (method === "patch" ? api.patch : api.put)(`${rPath}/${id}`, data);
+        const res = await (method === "patch" ? api.patch : api.put)(`${rPath}/${id}`, sanitized);
         return res.data;
       } catch (e: any) {
         setError(parseError(e));
@@ -697,7 +716,7 @@ export function useResource(resourceName: string): UseResourceReturn {
         setLoading(false);
       }
     },
-    [rPath, rUpdateMethod, setLoading, setError]
+    [rPath, rFields, schemas, resolveFk, rUpdateMethod, setLoading, setError]
   );
 
   const remove = useCallback(
diff --git a/react-openapi/src/utils/sanitize-payload.ts b/react-openapi/src/utils/sanitize-payload.ts
new file mode 100644
index 0000000..653ced5
--- /dev/null
+++ b/react-openapi/src/utils/sanitize-payload.ts
@@ -0,0 +1,67 @@
+import type { FieldConfig } from "../types";
+import { extractFields } from "../transformers/field-config";
+
+export type FkResolver = (resourceName: string, fkValue: any) => Promise<any>;
+
+export async function sanitizePayload(
+  data: any,
+  fields: FieldConfig[],
+  schemas: Record<string, any>,
+  resolveFk?: FkResolver,
+): Promise<any> {
+  if (data == null || typeof data !== "object") return data;
+
+  if (Array.isArray(data)) {
+    return Promise.all(data.map((item) => {
+      if (item != null && typeof item === "object") {
+        return sanitizePayload(item, fields, schemas, resolveFk);
+      }
+      return item;
+    }));
+  }
+
+  const result: Record<string, any> = { ...data };
+  const fieldMap = new Map(fields.map((f) => [f.name, f]));
+
+  for (const key of Object.keys(result)) {
+    const field = fieldMap.get(key);
+    if (!field) continue;
+
+    const val = result[key];
+
+    if (field.fk) {
+      if (val == null || val === "") {
+        result[key] = null;
+      } else if (resolveFk) {
+        if (field.isArray && Array.isArray(val)) {
+          result[key] = await Promise.all(val.map((v: any) => resolveFk(field.fk!.resource, v)));
+        } else {
+          result[key] = await resolveFk(field.fk!.resource, val);
+        }
+      }
+      continue;
+    }
+
+    if (field.refSchema && !field.fk) {
+      if (val == null || val === "") {
+        result[key] = field.isArray ? [] : {};
+      } else if (typeof val === "object") {
+        const refSchemaObj = schemas[field.refSchema!];
+        const nestedFields = refSchemaObj
+          ? extractFields(field.refSchema!, refSchemaObj, schemas)
+          : [];
+        result[key] = await sanitizePayload(val, nestedFields, schemas, resolveFk);
+      }
+    } else if (field.isArray) {
+      if (val == null || val === "") {
+        result[key] = [];
+      }
+    } else if (field.type === "object") {
+      if (val == null || val === "") {
+        result[key] = {};
+      }
+    }
+  }
+
+  return result;
+}