diff --git a/src/mgr/Action.cc b/src/mgr/Action.cc
index 2c8bf63bf57..7afa0f6a366 100644
--- a/src/mgr/Action.cc
+++ b/src/mgr/Action.cc
@@ -9,6 +9,7 @@
 /* DEBUG: section 16    Cache Manager API */
 
 #include "squid.h"
+#include "base/PackableStream.h"
 #include "CacheManager.h"
 #include "comm/Connection.h"
 #include "HttpReply.h"
@@ -112,7 +113,7 @@ Mgr::Action::fillEntry(StoreEntry* entry, bool writeHttpHeader)
         entry->replaceHttpReply(rep);
     }
 
-    dump(entry);
+    dump(entry); // TODO: replace with report() when all children are converted
 
     entry->flush();
 
@@ -120,3 +121,10 @@ Mgr::Action::fillEntry(StoreEntry* entry, bool writeHttpHeader)
         entry->complete();
 }
 
+void
+Mgr::Action::dump(StoreEntry *entry)
+{
+    PackableStream os(*entry);
+    report(os);
+}
+
diff --git a/src/mgr/Action.h b/src/mgr/Action.h
index bf09b0e1519..9100f32cad6 100644
--- a/src/mgr/Action.h
+++ b/src/mgr/Action.h
@@ -14,6 +14,8 @@
 #include "ipc/forward.h"
 #include "mgr/forward.h"
 
+#include <iosfwd>
+
 class StoreEntry;
 
 namespace Mgr
@@ -76,11 +78,14 @@ class Action: public RefCountable
     /// calculate and keep local action-specific information
     virtual void collect() {}
 
+    /// write manager report output to a stream.
+    virtual void report(std::ostream &) {}
+
     /** start writing action-specific info to Store entry;
      * may collect info during dump, especially if collect() did nothing
      * non-atomic() actions may continue writing asynchronously after returning
      */
-    virtual void dump(StoreEntry *) {}
+    virtual void dump(StoreEntry *);
 
 private:
     const CommandPointer cmd; ///< the command that caused this action
diff --git a/src/mgr/BasicActions.cc b/src/mgr/BasicActions.cc
index 341dcfad755..49c55c4c695 100644
--- a/src/mgr/BasicActions.cc
+++ b/src/mgr/BasicActions.cc
@@ -30,12 +30,6 @@ Mgr::IndexAction::IndexAction(const Command::Pointer &aCmd): Action(aCmd)
     debugs(16, 5, MYNAME);
 }
 
-void
-Mgr::IndexAction::dump(StoreEntry *)
-{
-    debugs(16, 5, MYNAME);
-}
-
 Mgr::MenuAction::Pointer
 Mgr::MenuAction::Create(const Command::Pointer &cmd)
 {
@@ -47,20 +41,26 @@ Mgr::MenuAction::MenuAction(const Command::Pointer &aCmd): Action(aCmd)
     debugs(16, 5, MYNAME);
 }
 
+/// A table summarizing available Cache Manager actions:
+///   table-row = SP 1*VCHAR 1*( HTAB 0*VCHAR )
 void
-Mgr::MenuAction::dump(StoreEntry* entry)
+Mgr::MenuAction::report(std::ostream &os)
 {
-    debugs(16, 5, MYNAME);
-    Must(entry != nullptr);
+    const auto &menu = CacheManager::GetInstance()->menu();
 
-    typedef CacheManager::Menu::const_iterator Iterator;
-    const CacheManager::Menu& menu = CacheManager::GetInstance()->menu();
+    const auto savedFlags = os.flags();
+    const auto savedFill = os.fill();
 
-    for (Iterator a = menu.begin(); a != menu.end(); ++a) {
-        storeAppendPrintf(entry, " %-22s\t%-32s\t%s\n",
-                          (*a)->name, (*a)->desc,
-                          CacheManager::GetInstance()->ActionProtection(*a));
+    os << std::left;
+    for (const auto &a : menu) {
+        os << ' ' << std::setw(22) << a->name << std::setw(0)
+           << '\t' << std::setw(32) << a->desc << std::setw(0)
+           << '\t' << CacheManager::GetInstance()->ActionProtection(a)
+           << '\n';
     }
+
+    os.fill(savedFill);
+    os.flags(savedFlags);
 }
 
 Mgr::ShutdownAction::Pointer
@@ -75,7 +75,7 @@ Mgr::ShutdownAction::ShutdownAction(const Command::Pointer &aCmd): Action(aCmd)
 }
 
 void
-Mgr::ShutdownAction::dump(StoreEntry *)
+Mgr::ShutdownAction::report(std::ostream &)
 {
     debugs(16, DBG_CRITICAL, "Shutdown by Cache Manager command.");
     shut_down(SIGTERM);
@@ -94,10 +94,10 @@ Mgr::ReconfigureAction::ReconfigureAction(const Command::Pointer &aCmd):
 }
 
 void
-Mgr::ReconfigureAction::dump(StoreEntry* entry)
+Mgr::ReconfigureAction::report(std::ostream &os)
 {
     debugs(16, DBG_IMPORTANT, "Reconfigure by Cache Manager command.");
-    storeAppendPrintf(entry, "Reconfiguring Squid Process ....");
+    os << "Reconfiguring Squid Process ... \n";
     reconfigure(SIGHUP);
 }
 
@@ -113,10 +113,10 @@ Mgr::RotateAction::RotateAction(const Command::Pointer &aCmd): Action(aCmd)
 }
 
 void
-Mgr::RotateAction::dump(StoreEntry* entry)
+Mgr::RotateAction::report(std::ostream &os)
 {
     debugs(16, DBG_IMPORTANT, "Rotate Logs by Cache Manager command.");
-    storeAppendPrintf(entry, "Rotating Squid Process Logs ....");
+    os << "Rotating Squid Process Logs ... \n";
 #if defined(_SQUID_LINUX_THREADS_)
     rotate_logs(SIGQUIT);
 #else
@@ -137,13 +137,12 @@ Mgr::OfflineToggleAction::OfflineToggleAction(const Command::Pointer &aCmd):
 }
 
 void
-Mgr::OfflineToggleAction::dump(StoreEntry* entry)
+Mgr::OfflineToggleAction::report(std::ostream &os)
 {
     Config.onoff.offline = !Config.onoff.offline;
     debugs(16, DBG_IMPORTANT, "offline_mode now " << (Config.onoff.offline ? "ON" : "OFF") << " by Cache Manager request.");
 
-    storeAppendPrintf(entry, "offline_mode is now %s\n",
-                      Config.onoff.offline ? "ON" : "OFF");
+    os << "offline_mode is now " << (Config.onoff.offline ? "ON" : "OFF") << '\n';
 }
 
 void
diff --git a/src/mgr/BasicActions.h b/src/mgr/BasicActions.h
index 08ba3ebb02c..5f2a926b831 100644
--- a/src/mgr/BasicActions.h
+++ b/src/mgr/BasicActions.h
@@ -27,7 +27,7 @@ class IndexAction: public Action
 public:
     static Pointer Create(const CommandPointer &cmd);
     /* Action API */
-    void dump(StoreEntry *entry) override;
+    void report(std::ostream &) override {}
 
 protected:
     IndexAction(const CommandPointer &cmd);
@@ -39,7 +39,7 @@ class MenuAction: public Action
 public:
     static Pointer Create(const CommandPointer &cmd);
     /* Action API */
-    void dump(StoreEntry *entry) override;
+    void report(std::ostream &) override;
 
 protected:
     MenuAction(const CommandPointer &cmd);
@@ -51,7 +51,7 @@ class ShutdownAction: public Action
 public:
     static Pointer Create(const CommandPointer &cmd);
     /* Action API */
-    void dump(StoreEntry *entry) override;
+    void report(std::ostream &) override;
 
 protected:
     ShutdownAction(const CommandPointer &cmd);
@@ -63,7 +63,7 @@ class ReconfigureAction: public Action
 public:
     static Pointer Create(const CommandPointer &cmd);
     /* Action API */
-    void dump(StoreEntry *entry) override;
+    void report(std::ostream &) override;
 
 protected:
     ReconfigureAction(const CommandPointer &cmd);
@@ -75,7 +75,7 @@ class RotateAction: public Action
 public:
     static Pointer Create(const CommandPointer &cmd);
     /* Action API */
-    void dump(StoreEntry *entry) override;
+    void report(std::ostream &) override;
 
 protected:
     RotateAction(const CommandPointer &cmd);
@@ -87,7 +87,7 @@ class OfflineToggleAction: public Action
 public:
     static Pointer Create(const CommandPointer &cmd);
     /* Action API */
-    void dump(StoreEntry *entry) override;
+    void report(std::ostream &) override;
 
 protected:
     OfflineToggleAction(const CommandPointer &cmd);
diff --git a/src/tests/stub_libmgr.cc b/src/tests/stub_libmgr.cc
index 8177995bd7c..6d1921a5954 100644
--- a/src/tests/stub_libmgr.cc
+++ b/src/tests/stub_libmgr.cc
@@ -34,6 +34,7 @@ const char * Mgr::Action::name() const STUB_RETVAL(nullptr)
 static Mgr::Command static_Command;
 const Mgr::Command & Mgr::Action::command() const STUB_RETVAL(static_Command)
 StoreEntry * Mgr::Action::createStoreEntry() const STUB_RETVAL(nullptr)
+void Mgr::Action::dump(StoreEntry *) STUB
 static Mgr::Action::Pointer dummyAction;
 
 #include "mgr/ActionParams.h"
@@ -48,27 +49,27 @@ void Mgr::ActionWriter::start() STUB
 
 #include "mgr/BasicActions.h"
 Mgr::Action::Pointer Mgr::MenuAction::Create(const Mgr::CommandPointer &) STUB_RETVAL(dummyAction)
-void Mgr::MenuAction::dump(StoreEntry *) STUB
+void Mgr::MenuAction::report(std::ostream &) STUB
 //protected:
 //Mgr::MenuAction::MenuAction(const CommandPointer &cmd) STUB
 
 Mgr::Action::Pointer Mgr::ShutdownAction::Create(const Mgr::CommandPointer &) STUB_RETVAL(dummyAction)
-void Mgr::ShutdownAction::dump(StoreEntry *) STUB
+void Mgr::ShutdownAction::report(std::ostream &) 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
+void Mgr::ReconfigureAction::report(std::ostream &) STUB
 //protected:
 //Mgr::ReconfigureAction::ReconfigureAction(const CommandPointer &) STUB
 
 Mgr::Action::Pointer Mgr::RotateAction::Create(const Mgr::CommandPointer &) STUB_RETVAL(dummyAction)
-void Mgr::RotateAction::dump(StoreEntry *) STUB
+void Mgr::RotateAction::report(std::ostream &) STUB
 //protected:
 //Mgr::RotateAction::RotateAction(const CommandPointer &) STUB
 
 Mgr::Action::Pointer Mgr::OfflineToggleAction::Create(const CommandPointer &) STUB_RETVAL(dummyAction)
-void Mgr::OfflineToggleAction::dump(StoreEntry *) STUB
+void Mgr::OfflineToggleAction::report(std::ostream &) STUB
 //protected:
 //Mgr::OfflineToggleAction::OfflineToggleAction(const CommandPointer &) STUB