diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2c8e541..5059f2f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@ All user-visible bugs and enhancements should be recorded here.
 
 ## Unreleased
 
+### Fixed
+
+- `xurl chat add-members` no longer fails with "Invalid action signature" on a group whose message timer (`message_ttl_ms`) or screen-capture blocking setting (`screen_capture_blocking_enabled`) has been set. The signed group state left both out; it now carries the values from the conversation.
+
 ## v1.3.2 - 2026-09-23
 
 ### Fixed
diff --git a/cli/chat.go b/cli/chat.go
index d92f7d3..790964c 100644
--- a/cli/chat.go
+++ b/cli/chat.go
@@ -1636,13 +1636,15 @@ func (s *chatSession) addGroupMembers(conversationID string, newMembers []string
 		return err
 	}
 	prepared, err := s.chat.PrepareGroupMembersChange(chatxdk.GroupMembersChangeParams{
-		PublicKeys:       inputs,
-		ConversationID:   api.ChatConversationEventID(conversationID),
-		NewMemberIDs:     newIDs,
-		CurrentMemberIDs: meta.MemberIDs,
-		CurrentAdminIDs:  meta.AdminIDs,
-		CurrentTitle:     meta.GroupName,
-		CurrentAvatarURL: meta.GroupAvatarURL,
+		PublicKeys:                          inputs,
+		ConversationID:                      api.ChatConversationEventID(conversationID),
+		NewMemberIDs:                        newIDs,
+		CurrentMemberIDs:                    meta.MemberIDs,
+		CurrentAdminIDs:                     meta.AdminIDs,
+		CurrentTitle:                        meta.GroupName,
+		CurrentAvatarURL:                    meta.GroupAvatarURL,
+		CurrentTTLMsec:                      meta.MessageTTLMs,
+		CurrentScreenCaptureBlockingEnabled: meta.ScreenCaptureBlockingEnabled,
 	})
 	if err != nil {
 		return fmt.Errorf("failed to prepare member change: %w", err)
diff --git a/cli/chat_test.go b/cli/chat_test.go
index 315c63b..42181ad 100644
--- a/cli/chat_test.go
+++ b/cli/chat_test.go
@@ -152,6 +152,75 @@ func TestPreparedChangeToRequestShape(t *testing.T) {
 	assert.False(t, has)
 }
 
+// addMembersStubClient serves the requests addGroupMembers makes and records
+// the body it posts.
+type addMembersStubClient struct {
+	api.Client
+	conversation string
+	publicKey    string
+	posted       string
+}
+
+func (c *addMembersStubClient) SendRequest(opts api.RequestOptions) (json.RawMessage, error) {
+	switch {
+	case opts.Method == "GET" && opts.Endpoint == "/2/chat/conversations/g100":
+		return json.RawMessage(c.conversation), nil
+	case opts.Method == "GET" && strings.HasSuffix(opts.Endpoint, "/public_keys"):
+		return json.RawMessage(fmt.Sprintf(`{"data":[{"public_key_version":"1","public_key":%q}]}`, c.publicKey)), nil
+	case opts.Method == "POST" && opts.Endpoint == "/2/chat/conversations/g100/members":
+		c.posted = opts.Data
+		return json.RawMessage(`{"data":{}}`), nil
+	}
+	return nil, fmt.Errorf("unexpected request %s %s", opts.Method, opts.Endpoint)
+}
+
+func TestAddGroupMembersSignsGroupSettings(t *testing.T) {
+	// The member-add signature covers the group's current settings. Its signed
+	// payload ends with {message_ttl_ms|null},{conversation key version},
+	// {screen_capture_blocking_enabled|null}, and must match the conversation.
+	tests := []struct {
+		name     string
+		settings string
+		want     string
+	}{
+		{"settings never set", ``, "null,%s,null"},
+		{"timer on, screen capture off", `,"message_ttl_ms":86400000,"screen_capture_blocking_enabled":false`, "86400000,%s,false"},
+		{"screen capture on", `,"screen_capture_blocking_enabled":true`, "null,%s,true"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			chat := chatxdk.New()
+			defer chat.Close()
+			keys, err := chat.GenerateKeypairs()
+			require.NoError(t, err)
+			require.NoError(t, chat.SetIdentity("42", "1"))
+
+			client := &addMembersStubClient{
+				conversation: `{"data":{"id":"g100","type":"group","member_ids":["42","7"],"admin_ids":["42"]` + tt.settings + `}}`,
+				publicKey:    keys.PublicKey.PublicKey,
+			}
+			s := &chatSession{chat: chat, client: client, userID: "42", usernames: map[string]string{}}
+			require.NoError(t, s.addGroupMembers("g100", []string{"300"}, true))
+
+			var body struct {
+				ConversationKeyVersion string `json:"conversation_key_version"`
+				ActionSignatures       []struct {
+					SignaturePayload string `json:"signature_payload"`
+				} `json:"action_signatures"`
+			}
+			require.NoError(t, json.Unmarshal([]byte(client.posted), &body))
+			var memberAdd string
+			for _, sig := range body.ActionSignatures {
+				if strings.HasPrefix(sig.SignaturePayload, "GroupChangeEvent.GroupMemberAddChange,") {
+					memberAdd = sig.SignaturePayload
+				}
+			}
+			require.NotEmpty(t, memberAdd, "no member-add signature in the request")
+			assert.True(t, strings.HasSuffix(memberAdd, ","+fmt.Sprintf(tt.want, body.ConversationKeyVersion)), memberAdd)
+		})
+	}
+}
+
 func TestChatConversationPathHelpers(t *testing.T) {
 	assert.Equal(t, "1-2", api.ChatConversationPathID("1:2"))
 	assert.Equal(t, "1:2", api.ChatConversationEventID("1-2"))