diff --git a/packages/varden/src/lib.ts b/packages/varden/src/lib.ts
index a70bd3e..85efe34 100644
--- a/packages/varden/src/lib.ts
+++ b/packages/varden/src/lib.ts
@@ -6,6 +6,7 @@ import {
   type ComputedRef,
   type Ref,
   type DeepReadonly,
+  toRaw,
 } from 'vue';
 
 import { getIssuePath, type StandardSchemaV1 } from './standard-schema';
@@ -35,7 +36,7 @@ export interface FormContext<T> {
   resetField<Path extends Paths<T>>(path: Path): void;
   setValue<Path extends Paths<T>, Value extends Get<T, Path>>(
     path: Path | CompiledPath,
-    value: Value,
+    value: Value | undefined,
   ): void;
   getValue<Path extends Paths<T>, Value extends Get<T, Path>>(path: Path | CompiledPath): Value;
   setTouched<Path extends Paths<T>>(path: Path, flag?: boolean): void;
@@ -50,8 +51,13 @@ export interface _FormContext<T> extends FormContext<T> {
   __meta: Map<Paths<T>, FieldMeta>;
 }
 
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function strictEqualsFn(a: any, b: any): boolean {
+  return a === b;
+}
+
 // eslint-disable-next-line no-underscore-dangle
-let _equalsFn: FormProps<unknown>['equalsFn'] & {} = (a, b) => a === b;
+let _equalsFn: FormProps<unknown>['equalsFn'] & {} = strictEqualsFn;
 // eslint-disable-next-line no-underscore-dangle
 let _cloneFn: FormProps<unknown>['cloneFn'] & {} = structuredClone;
 
@@ -61,7 +67,7 @@ export function defineVardenConfig(config: { equalsFn?: FormProps<unknown>['equa
 }
 
 export function resetVardenConfig() {
-  _equalsFn = (a, b) => a === b;
+  _equalsFn = strictEqualsFn;
   _cloneFn = structuredClone;
 }
 
@@ -185,7 +191,7 @@ export function useForm<T = object>(props: FormProps<T>): FormContext<T> {
     resetField,
     setValue<Path extends Paths<T>, Value extends Get<T, Path>>(
       path: Path | CompiledPath,
-      value: Value,
+      value: Value | undefined,
     ) {
       const compiledPath = Array.isArray(path) ? path : toCompiledPath(path);
       const stringPath = typeof path === 'string' ? path : compiledPath.join('.');
@@ -193,16 +199,35 @@ export function useForm<T = object>(props: FormProps<T>): FormContext<T> {
       set(currentValues.value, compiledPath, cloneFn(value));
 
       const meta = fields.get(stringPath);
-      const isDirty = !equalsFn(get(initialValues, compiledPath), value);
+      const isDirty = !equalsFn(get(initialValues, compiledPath, Empty), value);
       if (meta) {
         meta.dirty = isDirty;
       } else {
         fields.set(stringPath, createFieldMeta(false, isDirty, '', 0));
       }
+
+      // cleanup child fields
+      for (const [nestedPath, nestedMeta] of fields) {
+        if (nestedPath.startsWith(`${stringPath}.`)) {
+          if (nestedMeta !== undefined) {
+            if (nestedMeta.refCount === 0) {
+              fields.delete(nestedPath);
+            } else {
+              const compiledNestedPath = toCompiledPath(nestedPath);
+              nestedMeta.dirty = !equalsFn(
+                get(initialValues, compiledNestedPath),
+                get(currentValues.value, compiledNestedPath),
+              );
+            }
+          }
+        }
+      }
+
       applyValidation();
     },
     getValue<Path extends Paths<T>, Value extends Get<T, Path>>(path: Path | CompiledPath): Value {
-      return get(currentValues.value, Array.isArray(path) ? path : toCompiledPath(path));
+      const a = get(currentValues.value, Array.isArray(path) ? path : toCompiledPath(path));
+      return cloneFn(toRaw(a));
     },
     setTouched<Path extends Paths<T>>(path: Path, flag = true) {
       fields.get(path)!.touched = flag;
@@ -220,7 +245,27 @@ export function useForm<T = object>(props: FormProps<T>): FormContext<T> {
       onSubmit(cloneFn(currentValues.value));
     },
     isDirty<Path extends Paths<T>>(path: Path): boolean {
-      return fields.get(path)?.dirty ?? false;
+      // TODO: consider shipping dequal for deep equality
+      // this case is only possible if equalsFn is not strict equality
+      if (equalsFn !== strictEqualsFn) {
+        const compiledPath = toCompiledPath(path);
+        return !equalsFn(
+          get(currentValues.value, compiledPath, Empty),
+          get(initialValues, compiledPath, Empty),
+        );
+      }
+
+      for (const [field, meta] of fields) {
+        if (field === path) return meta.dirty;
+        if (field.startsWith(`${path}.`) && meta.dirty === true) return true;
+      }
+
+      // TODO: should be tracked after first check?
+      const compiledPath = toCompiledPath(path);
+      return !equalsFn(
+        get(currentValues.value, compiledPath, Empty),
+        get(initialValues, compiledPath, Empty),
+      );
     },
     isTouched<Path extends Paths<T>>(path: Path): boolean {
       return fields.get(path)?.touched ?? false;
diff --git a/packages/varden/src/path.spec.ts b/packages/varden/src/path.spec.ts
index 9b92fb1..44663f1 100644
--- a/packages/varden/src/path.spec.ts
+++ b/packages/varden/src/path.spec.ts
@@ -1,7 +1,7 @@
 import { expect, it, describe } from 'vitest';
 
 import {
-  del, get, isArrayIndex, set, toCompiledPath,
+  del, Empty, get, isArrayIndex, set, toCompiledPath,
 } from './path';
 
 describe('path utilities', () => {
@@ -34,6 +34,11 @@ describe('path utilities', () => {
     expect(get({ foo: { bar: '' } }, toCompiledPath('foo.bar'), 'TEST')).toBe('');
   });
 
+  it('path is longer than object', () => {
+    expect(get({ foo: undefined }, toCompiledPath('foo.bar.baz'), 'TEST')).toBe('TEST');
+    expect(get({ foo: undefined }, toCompiledPath('foo.bar'))).toBe(undefined);
+  });
+
   it('should delete value by path', () => {
     const value = { foo: { bar: 2, baz: 3 } };
     del(value, toCompiledPath('foo.bar'));
@@ -69,4 +74,9 @@ describe('path utilities', () => {
     // @ts-expect-error test case
     expect(test.foo.bar[0].baz).toBe(4);
   });
+
+  it('should return Empty for nested path under undefined field', () => {
+    const test = { user: undefined };
+    expect(get(test, toCompiledPath('user.name'), Empty)).toBe(Empty);
+  });
 });
diff --git a/packages/varden/src/path.ts b/packages/varden/src/path.ts
index 7737498..49f6396 100644
--- a/packages/varden/src/path.ts
+++ b/packages/varden/src/path.ts
@@ -45,11 +45,14 @@ export function get(
     if (typeof object === 'object' && object !== null && path[i]! in object) {
       object = object[path[i]!];
     } else {
-      return object[path[i]!] ?? defaultValue;
+      // target path is longer than the object, return defaultValue
+      return object?.[path[i]!] ?? defaultValue;
     }
   }
 
-  return object[path[limit]!];
+  // early return for null/undefined objects
+  if (!object) return defaultValue;
+  return path[limit]! in object ? object[path[limit]!] : defaultValue;
 }
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
diff --git a/packages/varden/tests/field-value.spec.ts b/packages/varden/tests/field-value.spec.ts
new file mode 100644
index 0000000..e4f48da
--- /dev/null
+++ b/packages/varden/tests/field-value.spec.ts
@@ -0,0 +1,176 @@
+import { describe, expect, it } from 'vitest';
+import * as v from 'valibot';
+import { dequal } from 'dequal';
+
+import { useForm } from '../src/lib';
+import { useFieldValue } from '../src/composables';
+
+const onSubmit = () => { };
+
+describe('form.setValue plain', () => {
+  it('should set the value of a field', () => {
+    const form = useForm({
+      onSubmit: () => { },
+      schema: v.object({ name: v.string() }),
+    });
+
+    form.setValue('name', 'foo');
+    expect(form.values.value.name).toBe('foo');
+    expect(form.isDirty('name')).toBe(true);
+  });
+
+  it('should treat undefined and missing field as dirty (shallow)', () => {
+    const form = useForm({
+      onSubmit,
+      schema: v.object({ foo: v.string() }),
+    });
+
+    form.setValue('foo', undefined);
+    expect(form.values.value?.foo).toBe(undefined);
+    expect(form.isDirty('foo')).toBe(true);
+  });
+
+  it('should treat undefined and missing field as dirty (deep)', () => {
+    const form = useForm({
+      onSubmit,
+      schema: v.object({ foo: v.object({ bar: v.string() }) }),
+    });
+
+    form.setValue('foo.bar', undefined);
+    expect(form.values.value?.foo?.bar).toBe(undefined);
+    expect(form.isDirty('foo.bar')).toBe(true);
+  });
+});
+
+describe('form.setValue object', () => {
+  it('should set the value of an object field', () => {
+    const form = useForm({
+      onSubmit: () => { },
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    form.setValue('user', { name: 'foo' });
+    expect(form.values.value?.user).toEqual({ name: 'foo' });
+    expect(form.isDirty('user')).toBe(true);
+  });
+
+  it('should set copied value of an object field', () => {
+    const form = useForm({
+      onSubmit: () => { },
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    const value = { name: 'foo' };
+    form.setValue('user', value);
+    value.name = 'bar';
+
+    expect(form.values.value?.user).toEqual({ name: 'foo' });
+    expect(form.isDirty('user')).toBe(true);
+  });
+
+  it('should reset child metadata', () => {
+    const form = useForm({
+      onSubmit: () => { },
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    form.setValue('user.name', 'foo');
+    form.setValue('user', undefined);
+
+    expect(form.values.value?.user?.name).toBeUndefined();
+    expect(form.isDirty('user.name')).toBe(false);
+  });
+
+  it('should keep child metadata for registered fields', () => {
+    const form = useForm({
+      onSubmit: () => { },
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    const name = useFieldValue(form, 'user.name');
+    name.value = 'foo';
+    form.setTouched('user.name');
+    form.setValue('user', undefined);
+
+    expect(form.values.value?.user?.name).toBeUndefined();
+    expect(form.isDirty('user.name')).toBe(false);
+    expect(form.isTouched('user.name')).toBe(true);
+  });
+
+  it('should mark child as not dirty when parent is set to initial values', () => {
+    const form = useForm({
+      onSubmit: () => { },
+      initial: { user: { name: 'initial' } },
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    const name = useFieldValue(form, 'user.name');
+    name.value = 'changed';
+    expect(form.isDirty('user.name')).toBe(true);
+
+    form.setValue('user', { name: 'initial' });
+
+    expect(form.values.value?.user?.name).toBe('initial');
+    expect(form.isDirty('user.name')).toBe(false);
+  });
+
+  it('should mark child as dirty when parent is set to different values', () => {
+    const form = useForm({
+      onSubmit: () => { },
+      initial: { user: { name: 'initial' } },
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    useFieldValue(form, 'user.name');
+    expect(form.isDirty('user.name')).toBe(false);
+
+    form.setValue('user', { name: 'changed' });
+
+    expect(form.values.value?.user?.name).toBe('changed');
+    expect(form.isDirty('user.name')).toBe(true);
+  });
+
+  it('should treat untracked parent as dirty if child is dirty', () => {
+    const form = useForm({
+      onSubmit,
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    form.setValue('user.name', 'test');
+    expect(form.isDirty('user')).toBe(true);
+  });
+
+  it('should treat child as dirty when parent affects child field state', () => {
+    const form = useForm({
+      onSubmit,
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    form.setValue('user', { name: 'Jack' });
+    expect(form.isDirty('user.name')).toBe(true);
+  });
+
+  it('should mark parent dirty if child is changed back to original value', () => {
+    const form = useForm({
+      onSubmit,
+      initial: { user: { name: 'initial' } },
+      equalsFn: dequal,
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+
+    form.setValue('user', { name: 'changed' });
+    form.setValue('user.name', 'initial');
+    expect(form.isDirty('user')).toBe(false);
+  });
+
+  it('should return a safe copy of the value', () => {
+    const form = useForm({
+      onSubmit,
+      schema: v.object({ user: v.object({ name: v.string() }) }),
+    });
+    form.setValue('user', { name: 'initial' });
+    const a = form.getValue('user');
+    a.name = 'changed';
+    expect(form.values.value.user?.name).toBe('initial');
+  });
+});