diff --git a/Sources/Flipcash2ClientProtocol/ContractInfo.swift b/Sources/Flipcash2ClientProtocol/ContractInfo.swift
index 5873174..519248f 100644
--- a/Sources/Flipcash2ClientProtocol/ContractInfo.swift
+++ b/Sources/Flipcash2ClientProtocol/ContractInfo.swift
@@ -2,7 +2,7 @@
 
 public enum Flipcash2ContractInfo {
     public static let version = "0.18.0-dev"
-    public static let protoCommit = "9d44350b8d4d8eda9d63cff405238bd0e2920409"
+    public static let protoCommit = "9f67566fd0297a27ad2de7a98474634adf4d3a24"
 
     public static var isLocal: Bool { protoCommit == localSentinel }
 
diff --git a/Sources/Flipcash2ClientProtocol/chat_v1_chat_service.pb.swift b/Sources/Flipcash2ClientProtocol/chat_v1_chat_service.pb.swift
index 7ec54e0..29ca7a2 100644
--- a/Sources/Flipcash2ClientProtocol/chat_v1_chat_service.pb.swift
+++ b/Sources/Flipcash2ClientProtocol/chat_v1_chat_service.pb.swift
@@ -761,9 +761,21 @@ public struct Flipcash_Chat_V1_StartChatRequest: Sendable {
     /// Clears the value of `profilePicture`. Subsequent reads from it will return its default value.
     public mutating func clearProfilePicture() {self._profilePicture = nil}
 
-    /// Rules governing participation in the chat. Optional; if not set, the
-    /// chat has no participation requirements. Caller must satisfy the rules
-    /// in order for the chat to be started.
+    /// Rules governing participation in the chat. Caller must satisfy the
+    /// rules, speaker rules included, in order for the chat to be started
+    /// (RULES_NOT_SATISFIED otherwise).
+    ///
+    /// The server currently accepts only the following, and refuses
+    /// anything else as INVALID_RULES:
+    ///  - Listener rules: exactly one MinimumBalanceRequirement, which is
+    ///    required, and optionally one StaffRequirement.
+    ///  - Speaker rules: optionally one MinimumBalanceRequirement. If set,
+    ///    it must be in the same currency and the same mints as the
+    ///    listener MinimumBalanceRequirement, and its amount must be larger
+    ///    by at least the currency's minimum transfer value.
+    /// Every MinimumBalanceRequirement must be at least the currency's
+    /// minimum transfer value (one unit at its last decimal place, e.g.
+    /// 0.01 USD or 1 JPY), in a currency the server can value.
     public var rules: Flipcash_Chat_V1_Rules {
       get {return _rules ?? Flipcash_Chat_V1_Rules()}
       set {_rules = newValue}
diff --git a/flipcash2.lock b/flipcash2.lock
index 9dc3c84..70f88c5 100644
--- a/flipcash2.lock
+++ b/flipcash2.lock
@@ -1,4 +1,4 @@
 # Pinned upstream contract. Regenerate with scripts/sync-protos.sh <sha>.
 upstream: code-payments/flipcash2-protobuf-api
-commit: 9d44350b8d4d8eda9d63cff405238bd0e2920409
-subject: Add support for featured groups (#138)
+commit: 9f67566fd0297a27ad2de7a98474634adf4d3a24
+subject: Update StartChat comments to enable minimum speaker balanace requirements for public groups (#139)
diff --git a/proto/chat/v1/chat_service.proto b/proto/chat/v1/chat_service.proto
index fffc873..275be7e 100644
--- a/proto/chat/v1/chat_service.proto
+++ b/proto/chat/v1/chat_service.proto
@@ -632,9 +632,21 @@ message StartChatRequest {
         // Optional. If set, it must be owned by the caller and READY.
         blob.v1.BlobId profile_picture = 2;
 
-        // Rules governing participation in the chat. Optional; if not set, the
-        // chat has no participation requirements. Caller must satisfy the rules
-        // in order for the chat to be started.
+        // Rules governing participation in the chat. Caller must satisfy the
+        // rules, speaker rules included, in order for the chat to be started
+        // (RULES_NOT_SATISFIED otherwise).
+        //
+        // The server currently accepts only the following, and refuses
+        // anything else as INVALID_RULES:
+        //  - Listener rules: exactly one MinimumBalanceRequirement, which is
+        //    required, and optionally one StaffRequirement.
+        //  - Speaker rules: optionally one MinimumBalanceRequirement. If set,
+        //    it must be in the same currency and the same mints as the
+        //    listener MinimumBalanceRequirement, and its amount must be larger
+        //    by at least the currency's minimum transfer value.
+        // Every MinimumBalanceRequirement must be at least the currency's
+        // minimum transfer value (one unit at its last decimal place, e.g.
+        // 0.01 USD or 1 JPY), in a currency the server can value.
         Rules rules = 3;
 
         // Description for the chat. Optional; empty sets none. Moderated like