diff --git a/src/ipc/TypedMsgHdr.cc b/src/ipc/TypedMsgHdr.cc
index b40ff0bfb0b..8a26b7bea42 100644
--- a/src/ipc/TypedMsgHdr.cc
+++ b/src/ipc/TypedMsgHdr.cc
@@ -11,6 +11,7 @@
 #include "squid.h"
 #include "base/TextException.h"
 #include "ipc/TypedMsgHdr.h"
+#include "sbuf/SBuf.h"
 #include "SquidString.h"
 #include "tools.h"
 
@@ -147,6 +148,29 @@ Ipc::TypedMsgHdr::putString(const String &s)
     putRaw(s.rawBuf(), s.psize());
 }
 
+void
+Ipc::TypedMsgHdr::getSBuf(SBuf &s) const
+{
+    const int length = getInt();
+    Must(length >= 0);
+    // SBuf doesn't need special handling for empty
+    if (!length) {
+        s.clear();
+        return;
+    }
+    Must(length <= maxSize);
+    s.assign(data.raw + offset, length);
+    offset += length;
+}
+
+void
+Ipc::TypedMsgHdr::putSBuf(const SBuf &s)
+{
+    Must(s.length() <= maxSize);
+    putInt(s.length());
+    putRaw(s.rawContent(), s.length());
+}
+
 void
 Ipc::TypedMsgHdr::getFixed(void *rawBuf, size_t rawSize) const
 {
diff --git a/src/ipc/TypedMsgHdr.h b/src/ipc/TypedMsgHdr.h
index 3f850cd738d..d60d4e153ff 100644
--- a/src/ipc/TypedMsgHdr.h
+++ b/src/ipc/TypedMsgHdr.h
@@ -25,6 +25,7 @@
 
 #include <type_traits>
 
+class SBuf;
 class String;
 
 namespace Ipc
@@ -57,6 +58,8 @@ class TypedMsgHdr: public msghdr
     /* access to message parts for selected commonly-used part types */
     void getString(String &s) const; ///< load variable-length string
     void putString(const String &s); ///< store variable-length string
+    void getSBuf(SBuf &s) const; ///< load variable-length SBuf
+    void putSBuf(const SBuf &s); ///< store variable-length SBuf
     int getInt() const; ///< load an integer
     void putInt(int n); ///< store an integer
     void getFixed(void *raw, size_t size) const; ///< always load size bytes
diff --git a/src/mgr/QueryParams.cc b/src/mgr/QueryParams.cc
index 312ab828dfc..a304de388e0 100644
--- a/src/mgr/QueryParams.cc
+++ b/src/mgr/QueryParams.cc
@@ -98,7 +98,7 @@ ParseParamValue(const SBuf &rawValue)
     if (tok.atEnd())
         return new Mgr::IntParam(array);
     else
-        return new Mgr::StringParam(SBufToString(rawValue));
+        return new Mgr::StringParam(rawValue);
 }
 
 /**
diff --git a/src/mgr/StringParam.cc b/src/mgr/StringParam.cc
index 4eca6f483b7..08c73f8ad6a 100644
--- a/src/mgr/StringParam.cc
+++ b/src/mgr/StringParam.cc
@@ -17,7 +17,7 @@ Mgr::StringParam::StringParam():
 {
 }
 
-Mgr::StringParam::StringParam(const String& aString):
+Mgr::StringParam::StringParam(const SBuf& aString):
     QueryParam(QueryParam::ptString), str(aString)
 {
 }
@@ -26,18 +26,11 @@ void
 Mgr::StringParam::pack(Ipc::TypedMsgHdr& msg) const
 {
     msg.putPod(type);
-    msg.putString(str);
+    msg.putSBuf(str);
 }
 
 void
 Mgr::StringParam::unpackValue(const Ipc::TypedMsgHdr& msg)
 {
-    msg.getString(str);
+    msg.getSBuf(str);
 }
-
-const String&
-Mgr::StringParam::value() const
-{
-    return str;
-}
-
diff --git a/src/mgr/StringParam.h b/src/mgr/StringParam.h
index ab8a8bbb04c..2770ab908f7 100644
--- a/src/mgr/StringParam.h
+++ b/src/mgr/StringParam.h
@@ -14,7 +14,7 @@
 #include "ipc/forward.h"
 #include "mgr/forward.h"
 #include "mgr/QueryParam.h"
-#include "SquidString.h"
+#include "sbuf/SBuf.h"
 
 namespace Mgr
 {
@@ -23,13 +23,13 @@ class StringParam: public QueryParam
 {
 public:
     StringParam();
-    StringParam(const String& aString);
+    StringParam(const SBuf& aString);
     void pack(Ipc::TypedMsgHdr& msg) const override;
     void unpackValue(const Ipc::TypedMsgHdr& msg) override;
-    const String& value() const;
+    const auto& value() const { return str; }
 
 private:
-    String str;
+    SBuf str;
 };
 
 } // namespace Mgr
diff --git a/src/tests/stub_libmgr.cc b/src/tests/stub_libmgr.cc
index 692fbab50e5..675b81c7558 100644
--- a/src/tests/stub_libmgr.cc
+++ b/src/tests/stub_libmgr.cc
@@ -55,8 +55,6 @@ void Mgr::MenuAction::dump(StoreEntry *) STUB
 
 Mgr::Action::Pointer Mgr::ShutdownAction::Create(const Mgr::CommandPointer &) STUB_RETVAL(dummyAction)
 void Mgr::ShutdownAction::dump(StoreEntry *) STUB
-// protected:
-//Mgr::ShutdownAction::ShutdownAction(const CommandPointer &) STUB
 
 Mgr::Action::Pointer Mgr::ReconfigureAction::Create(const Mgr::CommandPointer &) STUB_RETVAL(dummyAction)
 void Mgr::ReconfigureAction::dump(StoreEntry *) STUB
@@ -241,10 +239,6 @@ void Mgr::StoreToCommWriter::noteCommClosed(const CommCloseCbParams&) STUB
 void Mgr::StoreToCommWriter::close() STUB
 
 #include "mgr/StringParam.h"
-//Mgr::StringParam::StringParam() STUB
-//Mgr::StringParam::StringParam(const String&) STUB
 void Mgr::StringParam::pack(Ipc::TypedMsgHdr&) const STUB
 void Mgr::StringParam::unpackValue(const Ipc::TypedMsgHdr&) STUB
-static String t;
-const String& Mgr::StringParam::value() const STUB_RETVAL(t)