diff --git a/client b/client
index c1839bd..615c317 160000
--- a/client
+++ b/client
@@ -1 +1 @@
-Subproject commit c1839bd960c13d3ab1bbe271749aa655701f1b92
+Subproject commit 615c317a66f8d79b71d673f53b461a6f4d47a8e2
diff --git a/common/proto/table_validation.proto b/common/proto/table_validation.proto
index 417f9db..4ffe9ec 100644
--- a/common/proto/table_validation.proto
+++ b/common/proto/table_validation.proto
@@ -23,6 +23,7 @@ message FieldValidation {
   CharacterLimits limits = 10;
   // Future expansion:
   PatternRules pattern = 11; // Validation 2
+  optional CustomFormatter formatter = 14; // Validation 4 – custom formatting logic
   DisplayMask mask = 3;
   // ExternalValidation external = 13;
   // CustomFormatter formatter = 14;
@@ -73,6 +74,15 @@ message PatternRule {
   string filter = 2;
 }
 
+message CustomFormatter {
+  // Formatter type identifier; handled client‑side.
+  // Examples: "PSCFormatter", "PhoneFormatter", "CreditCardFormatter", "DateFormatter"
+  string type = 1;
+
+  // Optional free‑text note or parameters (e.g. locale, pattern)
+  optional string description = 2;
+}
+
 // Collection of pattern rules for one field
 message PatternRules {
   // All rules that make up the validation logic
diff --git a/flake.nix b/flake.nix
index d6963be..ab5d720 100644
--- a/flake.nix
+++ b/flake.nix
@@ -20,6 +20,7 @@
             rustfmt
             clippy
             cargo-watch
+	    rust-analyzer
 
             # C build tools (for your linker issue)
             gcc