diff --git a/cue-ios/CueIOS/AppState.swift b/cue-ios/CueIOS/AppState.swift
index 7dfd29d..630d395 100644
--- a/cue-ios/CueIOS/AppState.swift
+++ b/cue-ios/CueIOS/AppState.swift
@@ -223,6 +223,7 @@ final class AppState {
             status = "Chlorine complete: \(clPoints.count) points"
 
         case .phResult(let r):
+            transport.measuring = false
             if collectingRefs {
                 phRef = r
             } else {
@@ -256,6 +257,7 @@ final class AppState {
             break
 
         case .refsDone:
+            transport.measuring = false
             collectingRefs = false
             hasDeviceRefs = true
             refMode = nil
@@ -364,6 +366,7 @@ final class AppState {
 
     func startPh() {
         phResult = nil
+        transport.measuring = true
         let stab = Float(phStabilize) ?? 30
         send(buildSysexGetTemp())
         send(buildSysexStartPh(stabilizeS: stab))
@@ -408,6 +411,7 @@ final class AppState {
 
     func collectRefs() {
         collectingRefs = true
+        transport.measuring = true
         eisRefs.removeAll()
         status = "Starting reference collection..."
         send(buildSysexStartRefs())
@@ -415,6 +419,7 @@ final class AppState {
 
     func getRefs() {
         collectingRefs = true
+        transport.measuring = true
         eisRefs.removeAll()
         send(buildSysexGetRefs())
     }
@@ -432,8 +437,12 @@ final class AppState {
     func startClean() {
         let v = Float(cleanV) ?? 1200
         let d = Float(cleanDur) ?? 30
+        transport.measuring = true
         send(buildSysexStartClean(vMv: v, durationS: d))
         status = String(format: "Cleaning: %.0f mV for %.0fs", v, d)
+        DispatchQueue.main.asyncAfter(deadline: .now() + Double(d) + 2) { [weak self] in
+            self?.transport.measuring = false
+        }
     }
 
     var hasCurrentRef: Bool {
diff --git a/cue-ios/CueIOS/Transport/UDPManager.swift b/cue-ios/CueIOS/Transport/UDPManager.swift
index a228c02..351aa91 100644
--- a/cue-ios/CueIOS/Transport/UDPManager.swift
+++ b/cue-ios/CueIOS/Transport/UDPManager.swift
@@ -23,6 +23,9 @@ final class UDPManager: @unchecked Sendable {
     var address: String
     var port: UInt16
 
+    /// Suppress keepalive timeout during blocking firmware operations (pH, clean, refs)
+    var measuring: Bool = false
+
     private var connection: NWConnection?
     private let queue = DispatchQueue(label: "udp.eis4", qos: .userInitiated)
     private var onMessage: ((EisMessage) -> Void)?
@@ -76,6 +79,7 @@ final class UDPManager: @unchecked Sendable {
         stopTimers()
         connection?.cancel()
         connection = nil
+        measuring = false
         state = .disconnected
     }
 
@@ -178,7 +182,7 @@ final class UDPManager: @unchecked Sendable {
         }
 
         timeoutTimer = Timer.scheduledTimer(withTimeInterval: 2, repeats: true) { [weak self] _ in
-            guard let self, self.state == .connected else { return }
+            guard let self, self.state == .connected, !self.measuring else { return }
             if Date().timeIntervalSince(self.lastReceived) > Self.timeout {
                 self.state = .disconnected
                 self.stopTimers()