diff --git a/pkg/routes/routes.go b/pkg/routes/routes.go
index 8e026a87..f1095e51 100644
--- a/pkg/routes/routes.go
+++ b/pkg/routes/routes.go
@@ -134,6 +134,7 @@ func (r *Routes) AssignRoutes(eng *gin.Engine) {
 			routes.POST("/check", r.jidValidationMiddleware.ValidateNumberFieldWithFormatJid(), r.userHandler.CheckUser)
 			routes.POST("/avatar", r.jidValidationMiddleware.ValidateNumberField(), r.userHandler.GetAvatar)
 			routes.GET("/contacts", r.userHandler.GetContacts)
+			routes.POST("/contacts", r.userHandler.SaveContact)
 			routes.GET("/privacy", r.userHandler.GetPrivacy)
 			routes.POST("/privacy", r.userHandler.SetPrivacy)
 			routes.POST("/block", r.jidValidationMiddleware.ValidateNumberField(), r.userHandler.BlockContact)
diff --git a/pkg/user/handler/save_contact.go b/pkg/user/handler/save_contact.go
new file mode 100644
index 00000000..025e447e
--- /dev/null
+++ b/pkg/user/handler/save_contact.go
@@ -0,0 +1,53 @@
+package user_handler
+
+// HTTP handler for saving a contact to the device addressbook.
+// See the rationale in pkg/user/service/save_contact.go.
+
+import (
+	"net/http"
+
+	instance_model "github.com/evolution-foundation/evolution-go/pkg/instance/model"
+	user_service "github.com/evolution-foundation/evolution-go/pkg/user/service"
+	"github.com/gin-gonic/gin"
+)
+
+// Save a contact to the device addressbook
+// @Summary Save a contact
+// @Description Save/update a contact in the WhatsApp contact list (app state), asking the
+// @Description primary device to also store it in the system addressbook.
+// @Tags User
+// @Accept json
+// @Produce json
+// @Param message body user_service.SaveContactStruct true "Contact data"
+// @Success 200 {object} gin.H "success"
+// @Failure 400 {object} gin.H "Error on validation"
+// @Failure 500 {object} gin.H "Internal server error"
+// @Router /user/contacts [post]
+func (u *userHandler) SaveContact(ctx *gin.Context) {
+	getInstance := ctx.MustGet("instance")
+
+	instance, ok := getInstance.(*instance_model.Instance)
+	if !ok {
+		ctx.JSON(http.StatusInternalServerError, gin.H{"error": "instance not found"})
+		return
+	}
+
+	var data *user_service.SaveContactStruct
+	err := ctx.ShouldBindBodyWithJSON(&data)
+	if err != nil {
+		ctx.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	if len(data.Number) < 1 || len(data.FullName) < 1 {
+		ctx.JSON(http.StatusBadRequest, gin.H{"error": "phone and fullName are required"})
+		return
+	}
+
+	if err := u.userService.SaveContact(data, instance); err != nil {
+		ctx.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	ctx.JSON(http.StatusOK, gin.H{"message": "success"})
+}
diff --git a/pkg/user/handler/user_handler.go b/pkg/user/handler/user_handler.go
index 173fa920..806e3ab4 100644
--- a/pkg/user/handler/user_handler.go
+++ b/pkg/user/handler/user_handler.go
@@ -13,6 +13,7 @@ type UserHandler interface {
 	CheckUser(ctx *gin.Context)
 	GetAvatar(ctx *gin.Context)
 	GetContacts(ctx *gin.Context)
+	SaveContact(ctx *gin.Context)
 	GetPrivacy(ctx *gin.Context)
 	SetPrivacy(ctx *gin.Context)
 	BlockContact(ctx *gin.Context)
diff --git a/pkg/user/service/save_contact.go b/pkg/user/service/save_contact.go
new file mode 100644
index 00000000..cbff2756
--- /dev/null
+++ b/pkg/user/service/save_contact.go
@@ -0,0 +1,79 @@
+package user_service
+
+// Save a contact to the device addressbook.
+//
+// WhatsApp syncs the contact list across devices via APP STATE (the same
+// channel as mute/pin/archive): a "contact"-index mutation on the
+// critical_unblock_low patch — which whatsmeow itself applies back into
+// Store.Contacts on receipt (appstate.go, IndexContact → PutContactName).
+// The API currently exposes only the READ side (GET /user/contacts); this
+// adds the WRITE side: build the ContactAction (FullName/FirstName +
+// SaveOnPrimaryAddressbook, which asks the primary phone to also store it in
+// the SYSTEM addressbook) and send it with the official primitive
+// Client.SendAppState. After the resync SendAppState triggers, the contact
+// shows up in GET /user/contacts.
+//
+// Own file + minimal call-site lines (interface/handler/route) to keep the
+// change easy to review and rebase.
+
+import (
+	"context"
+	"errors"
+	"strings"
+
+	instance_model "github.com/evolution-foundation/evolution-go/pkg/instance/model"
+	"go.mau.fi/whatsmeow/appstate"
+	waSyncAction "go.mau.fi/whatsmeow/proto/waSyncAction"
+	"go.mau.fi/whatsmeow/types"
+	"google.golang.org/protobuf/proto"
+)
+
+type SaveContactStruct struct {
+	Number    string `json:"phone"`
+	FullName  string `json:"fullName"`
+	FirstName string `json:"firstName"`
+}
+
+// contactMutationVersion is the static version of the "contact" index
+// mutation (each index has its own — mute=2, pin=5, …; reference
+// implementations use 2 for contact). A wrong value fails CLEANLY in
+// SendAppState (the server rejects the patch), with no side effects.
+const contactMutationVersion = 2
+
+func (u *userService) SaveContact(data *SaveContactStruct, instance *instance_model.Instance) error {
+	client, err := u.ensureClientConnected(instance.Id)
+	if err != nil {
+		return err
+	}
+	number := strings.TrimSpace(data.Number)
+	fullName := strings.TrimSpace(data.FullName)
+	if number == "" || fullName == "" {
+		return errors.New("phone and fullName are required")
+	}
+	firstName := strings.TrimSpace(data.FirstName)
+	if firstName == "" {
+		firstName = strings.Fields(fullName)[0]
+	}
+	jid := types.NewJID(number, types.DefaultUserServer)
+
+	patch := appstate.PatchInfo{
+		Type: appstate.WAPatchCriticalUnblockLow, // the patch that carries the contact list
+		Mutations: []appstate.MutationInfo{{
+			Index:   []string{appstate.IndexContact, jid.String()},
+			Version: contactMutationVersion,
+			Value: &waSyncAction.SyncActionValue{
+				ContactAction: &waSyncAction.ContactAction{
+					FullName:                 proto.String(fullName),
+					FirstName:                proto.String(firstName),
+					SaveOnPrimaryAddressbook: proto.Bool(true),
+				},
+			},
+		}},
+	}
+	if err := client.SendAppState(context.Background(), patch); err != nil {
+		u.loggerWrapper.GetLogger(instance.Id).LogError("[%s] SaveContact %s: %v", instance.Id, jid.String(), err)
+		return err
+	}
+	u.loggerWrapper.GetLogger(instance.Id).LogInfo("[%s] Contact saved to addressbook: %s (%s)", instance.Id, fullName, jid.String())
+	return nil
+}
diff --git a/pkg/user/service/user_service.go b/pkg/user/service/user_service.go
index f3011606..2a27fecb 100644
--- a/pkg/user/service/user_service.go
+++ b/pkg/user/service/user_service.go
@@ -22,6 +22,7 @@ type UserService interface {
 	CheckUser(data *CheckUserStruct, instance *instance_model.Instance) (*CheckUserCollection, error)
 	GetAvatar(data *GetAvatarStruct, instance *instance_model.Instance) (*types.ProfilePictureInfo, error)
 	GetContacts(instance *instance_model.Instance) ([]ContactInfo, error)
+	SaveContact(data *SaveContactStruct, instance *instance_model.Instance) error
 	GetPrivacy(instance *instance_model.Instance) (types.PrivacySettings, error)
 	SetPrivacy(data *PrivacyStruct, instance *instance_model.Instance) (*types.PrivacySettings, error)
 	BlockContact(data *BlockStruct, instance *instance_model.Instance) (*types.Blocklist, error)