diff --git a/Config/Orchestrator.ocfg b/Config/Orchestrator.ocfg
index f878e144..1a8d08f3 100644
--- a/Config/Orchestrator.ocfg
+++ b/Config/Orchestrator.ocfg
@@ -8,10 +8,10 @@
 
 [Orchestrator_header]
 // All pretty arbitrary; just copied in and stored
-name        = OrchestratorConfiguration
-author      = "MLV and GMB"
-date        = "2021-01-17"
-version     = "0.0.6"
+name        = "OrchestratorConfiguration"
+author      = "MLV"
+date        = "2021-08-27"
+version     = "0.1.0"
 
 // All these may be overridden by the console "path" command
 [default_paths]
@@ -58,6 +58,11 @@ hardware = "../Config/POETSHardwareOneBox.ocfg"
 // Default flags for the cross-compiler
 // build = "\oink -plop ++wheeee  !. <?> "
 
+// Alter the behaviour of the Orchestrator
+[modes]
+single_app_mode = "true"  // Either 'true' or 'false'. Must be true to support
+                          // hardware idle, for now.
+
 // Elaboration messages passed out to the author for errors in processing THIS
 // file They are all classed as "Unrecoverable", not because they are, but
 // because: If you're not a grown-up you shouldn't be mucking about with it
diff --git a/Config/OrchestratorMessages.ocfg b/Config/OrchestratorMessages.ocfg
index de969189..73058130 100644
--- a/Config/OrchestratorMessages.ocfg
+++ b/Config/OrchestratorMessages.ocfg
@@ -133,7 +133,7 @@
 // Loading, typelinking
 
 100(U) : "MLV: Allocated but as yet unused"
-101(S) : "Decoder in %s (PID %s) has dropped a packet from %s(rank %s) to %s(rank %s) with key 0x%s"
+101(S) : "Decoder in %s (rank %s) has dropped a packet from %s (rank %s) with key 0x%s."
 102(I) : "Task graph default file path is ||%s||"
 103(I) : "New path is ||%s||"
 104(W) : "Filename %s does not parse correctly"
@@ -450,7 +450,7 @@
 534(I) : "Mothership (rank %s): All devices on this Mothership for application '%s' have stopped."
 535(I) : "Mothership (rank %s): Recalling application '%s'."
 536(I) : "Mothership (rank %s): Application '%s' recalled. This Mothership has forgotten everything about this application."
-537(U) : "MLV: Allocated but as yet unused"
+537(E) : "Mothership: Error decoding MPI message with key '0x%s': Expected bool in field %s. Ignoring message."
 538(U) : "MLV: Allocated but as yet unused"
 539(U) : "MLV: Allocated but as yet unused"
 540(U) : "GMB: Allocated but as yet unused"
@@ -489,8 +489,10 @@
 573(U) : "MLV: Allocated but as yet unused"
 574(U) : "MLV: Allocated but as yet unused"
 575(U) : "MLV: Allocated but as yet unused"
-578(U) : "MLV: Allocated but as yet unused"
-579(U) : "MLV: Allocated but as yet unused"
+576(U) : "MLV: Allocated but as yet unused"
+577(I) : "Mothership: Calling backend->loadAll."
+578(I) : "Mothership: Calling backend->go."
+579(I) : "Mothership: Calling backend->startAll."
 580(E) : "Mothership: Received a log packet with an invalid device index 0x%s."
 581(I) : "Mothership: Consuming log packet from device address 0x%s with name %s."
 582(I) : "Mothership: Received a message containing packets for a supervisor device for application '%s' that is not running (it may be in the process of stopping). Ignoring these packets."
diff --git a/Source/Common/Decode.cpp b/Source/Common/Decode.cpp
index 262d1058..f738e7c5 100644
--- a/Source/Common/Decode.cpp
+++ b/Source/Common/Decode.cpp
@@ -32,12 +32,9 @@ if (CommonBase::FnMap.find(pPkt->Key())!=CommonBase::FnMap.end()) {
                                        // Nope. Kick.
                                        // Pull out the unknown key and post what
                                        // little we know to the LogServer
-Post(101,Sderived,int2str(pPkt->Src()),pPmap->vPmap[pPkt->Src()].P_class,int2str(pPkt->Tgt()),
-     pPmap->vPmap[pPkt->Tgt()].P_class,hex2str(pPkt->Key()));
+Post(101,Sderived,int2str(pPkt->Tgt()),pPmap->vPmap[pPkt->Src()].P_class,
+     int2str(pPkt->Src()),hex2str(pPkt->Key()));
 return 0;                              // Return "keep going" value
 }
 
 //==============================================================================
-
-
-
diff --git a/Source/Common/Pglobals.cpp b/Source/Common/Pglobals.cpp
index e986fcf7..9738b7e5 100644
--- a/Source/Common/Pglobals.cpp
+++ b/Source/Common/Pglobals.cpp
@@ -40,8 +40,9 @@ const byte Q::SPEC    = 0x50;
 const byte Q::SUPD    = 0x51;
 const byte Q::INIT    = 0x52;
 const byte Q::CNC     = 0x53;
-const byte Q::ACKt     = 0x54;
+const byte Q::ACKt    = 0x54;
 const byte Q::SUPR    = 0x55;
+const byte Q::EMPT    = 0x56;
 // temporary use: for MPI testing ------------------------------------------
 const byte Q::M0      = 0x60;
 const byte Q::M1      = 0x61;
diff --git a/Source/Common/Pglobals.h b/Source/Common/Pglobals.h
index d26e57b5..f4b36525 100644
--- a/Source/Common/Pglobals.h
+++ b/Source/Common/Pglobals.h
@@ -80,8 +80,12 @@ Mothership
 ----------
 EXIT |-    |-    |-    | (None)
 SYST |KILL |-    |-    | (None)
+APP  |EMPT |-    |-    | (0:string)Code path to broadcast
+                       | (1:string)Data path to broadcast
 APP  |SPEC |-    |-    | (0:string)Application name
                          (1:uint32_t)Number of expected distribution messages
+                         (2:uint8_t)Application number
+                         (3:bool)Hardware-idle application?
 APP  |DIST |-    |-    | (0:string)Application name
                          (1:string)Code path for this core
                          (2:string)Data path for this core
@@ -152,6 +156,7 @@ static const byte INIT;
 static const byte CNC;
 static const byte ACK;
 static const byte SUPR;
+static const byte EMPT;
 // temporary use: for MPI testing ------------------------------------------
 static const byte M0;
 static const byte M1;
diff --git a/Source/Mothership/AppDB.cpp b/Source/Mothership/AppDB.cpp
index c09d72dd..c3947072 100644
--- a/Source/Mothership/AppDB.cpp
+++ b/Source/Mothership/AppDB.cpp
@@ -1,10 +1,12 @@
 #include "AppDB.h"
 
 /* Checks appInfos for an application of a given name. If it doesn't exist,
- * AppDB creates it and returns a pointer to it (passing distCountExpected to
- * it as an argument). If it already exists, returns a pointer to the existing
- * application, and does not use distCountExpected. */
-AppInfo* AppDB::check_create_app(std::string name, uint32_t distCountExpected)
+ * AppDB creates it and returns a pointer to it (passing distCountExpected and
+ * soloApp to it as an argument). If it already exists, returns a pointer to
+ * the existing application, does not use distCountExpected, but sets
+ * soloApp. */
+AppInfo* AppDB::check_create_app(std::string name, uint32_t distCountExpected,
+                                 bool soloApp)
 {
     AppInfoIt appFinder = appInfos.find(name);
 
@@ -21,7 +23,7 @@ AppInfo* AppDB::check_create_app(std::string name, uint32_t distCountExpected)
         else
         {
             appInfos.insert(std::pair<std::string, AppInfo>
-                            (name, AppInfo(name, distCountExpected)));
+                            (name, AppInfo(name, distCountExpected, soloApp)));
         }
 
         return &(appInfos.find(name)->second);
@@ -37,7 +39,7 @@ AppInfo* AppDB::check_create_app(std::string name, uint32_t distCountExpected)
 /* Sub-synonym. */
 AppInfo* AppDB::check_create_app(std::string name)
 {
-    return check_create_app(name, 0);
+    return check_create_app(name, 0, false);  /* soloApp argument not used. */
 }
 
 /* Checks appInfos for an application of a given name, returning true if such
diff --git a/Source/Mothership/AppDB.h b/Source/Mothership/AppDB.h
index 32667778..4a067f26 100644
--- a/Source/Mothership/AppDB.h
+++ b/Source/Mothership/AppDB.h
@@ -22,7 +22,7 @@ class AppDB
     std::map<uint32_t, uint32_t> threadToCoreAddr;
     std::map<uint8_t, std::string> numberToApp;
 
-    AppInfo* check_create_app(std::string, uint32_t);
+    AppInfo* check_create_app(std::string, uint32_t, bool);
     AppInfo* check_create_app(std::string);
     bool check_defined_app(std::string);
     void recall_app(AppInfo*);
diff --git a/Source/Mothership/AppInfo.cpp b/Source/Mothership/AppInfo.cpp
index 9b27395e..832d1545 100644
--- a/Source/Mothership/AppInfo.cpp
+++ b/Source/Mothership/AppInfo.cpp
@@ -1,9 +1,10 @@
 #include "AppInfo.h"
 
 /* This constructor is used by SPEC messages. */
-AppInfo::AppInfo(std::string name, uint32_t distCountExpected):
+AppInfo::AppInfo(std::string name, uint32_t distCountExpected, bool soloApp):
     name(name),
-    distCountExpected(distCountExpected)
+    distCountExpected(distCountExpected),
+    soloApp(soloApp)
 {
     pendingCommands = 0;
     distCountCurrent = 0;
diff --git a/Source/Mothership/AppInfo.h b/Source/Mothership/AppInfo.h
index 408462fa..98073c88 100644
--- a/Source/Mothership/AppInfo.h
+++ b/Source/Mothership/AppInfo.h
@@ -39,11 +39,12 @@ enum AppState{UNDERDEFINED,  /* We're still receiving DIST messages. */
 class AppInfo
 {
 public:
-    AppInfo(std::string nameArg, uint32_t distCountExpected);
+    AppInfo(std::string nameArg, uint32_t distCountExpected, bool soloApp);
     AppInfo(std::string nameArg);
 
     std::string name;
     uint32_t distCountExpected;
+    bool soloApp;
     AppState state;
     std::map<uint32_t, CoreInfo> coreInfos;
     std::set<uint32_t> coresLoaded;
diff --git a/Source/Mothership/AppTransitions.cpp b/Source/Mothership/AppTransitions.cpp
index 81320820..22ef2158 100644
--- a/Source/Mothership/AppTransitions.cpp
+++ b/Source/Mothership/AppTransitions.cpp
@@ -58,44 +58,62 @@ void Mothership::initialise_application(AppInfo* app)
                                  meshX, meshY, coreId);
     }
 
-    /* 2: For each core, kick off the threads (mode=false).
-     * 3: For each core, start execution (mode=true). */
-    mode = false;
-    do
+    /* 2: For each core, kick off the threads.
+     * 3: For each core, start execution. */
+
+    /* In solo-app mode, use backend's available global start and go
+     * methods. */
+    if (app->soloApp)
     {
-        for (coreIt = app->coreInfos.begin(); coreIt != app->coreInfos.end();
-             coreIt++)
-        {
-            backend->fromAddr(coreIt->first, &meshX, &meshY, &coreId,
-                              &threadId);
+        debug_post(579, 0);
+        backend->startAll();  /* 2 */
+        debug_post(578, 0);
+        backend->go();  /* 3 */
+    }
 
-            if (!mode)  /* 2 */
-            {
-                debug_post(
-                    587, 4, hex2str(meshX).c_str(), hex2str(meshY).c_str(),
-                    hex2str(coreId).c_str(),
-                    uint2str(coreIt->second.threadsExpected.size()).c_str());
-                /* Note that startOne can hang for the Tinsel backend if the
-                 * number of threads expected is greater than the number of
-                 * threads that the core will start - this is because startOne
-                 * waits for an acknowledgement message from the core that
-                 * varies as a function of the number of threads. If you find
-                 * the above 587 being the last message you see from the MPI
-                 * CNC Resolver thread (for example), this is most likely your
-                 * issue. */
-                backend->startOne(meshX, meshY, coreId,
-                                  coreIt->second.threadsExpected.size());
-            }
-            else  /* 3 */
+    /* Otherwise, things get more complicated... */
+    else
+    {
+        mode = false;  /* 2 when false, 3 when true. */
+        do  /* Simple loop to reduce code duplication (see comment accompanying
+             * this function definition). */
+        {
+            for (coreIt = app->coreInfos.begin();
+                 coreIt != app->coreInfos.end(); coreIt++)
             {
-                debug_post(586, 3, hex2str(meshX).c_str(),
-                           hex2str(meshY).c_str(), hex2str(coreId).c_str());
-                backend->goOne(meshX, meshY, coreId);
+                backend->fromAddr(coreIt->first, &meshX, &meshY, &coreId,
+                                  &threadId);
+
+                if (!mode)  /* 2 */
+                {
+                    debug_post(
+                        587, 4, hex2str(meshX).c_str(), hex2str(meshY).c_str(),
+                        hex2str(coreId).c_str(),
+                        uint2str(coreIt->second.threadsExpected.size())
+                        .c_str());
+                    /* Note that startOne can hang for the Tinsel backend if
+                     * the number of threads expected is greater than the
+                     * number of threads that the core will start - this is
+                     * because startOne waits for an acknowledgement message
+                     * from the core that varies as a function of the number of
+                     * threads. If you find the above 587 being the last
+                     * message you see from the MPI CNC Resolver thread (for
+                     * example), this is most likely your issue. */
+                    backend->startOne(meshX, meshY, coreId,
+                                      coreIt->second.threadsExpected.size());
+                }
+                else  /* 3 */
+                {
+                    debug_post(586, 3, hex2str(meshX).c_str(),
+                               hex2str(meshY).c_str(),
+                               hex2str(coreId).c_str());
+                    backend->goOne(meshX, meshY, coreId);
+                }
             }
-        }
 
-        mode = !mode;
-    } while (mode);
+            mode = !mode;
+        } while (mode);
+    }
 
     /* Good stuff. Now the cores will spin up and send BARRIER messages to the
      * Mothership. */
diff --git a/Source/Mothership/MPIHandlers.cpp b/Source/Mothership/MPIHandlers.cpp
index fec38f8b..58f77b1b 100644
--- a/Source/Mothership/MPIHandlers.cpp
+++ b/Source/Mothership/MPIHandlers.cpp
@@ -54,8 +54,8 @@ unsigned Mothership::handle_msg_cnc(PMsg_p* message)
 {
     #if ORCHESTRATOR_DEBUG
     std::string key = "Unknown";
-    if (message->Key() == PMsg_p::KEY(Q::APP,Q::SPEC))
-        key = "Q::APP,Q::SPEC";
+    if (message->Key() == PMsg_p::KEY(Q::APP,Q::EMPT))
+        key = "Q::APP,Q::EMPT";
     else if (message->Key() == PMsg_p::KEY(Q::APP,Q::SPEC))
         key = "Q::APP,Q::SPEC";
     else if (message->Key() == PMsg_p::KEY(Q::APP,Q::DIST))
@@ -79,6 +79,28 @@ unsigned Mothership::handle_msg_cnc(PMsg_p* message)
     return 0;
 }
 
+unsigned Mothership::handle_msg_app_empt(PMsg_p* message)
+{
+    /* Pull message contents. */
+    std::string codePath;
+    std::string dataPath;
+    if (!decode_app_empt_message(message, &codePath, &dataPath))
+    {
+        debug_post(597, 3, "Q::APP,Q::EMPT", hex2str(message->Key()).c_str(),
+                   "Failed to decode.");
+        return 0;
+    }
+
+    debug_post(597, 3, "Q::APP,Q::EMPT", hex2str(message->Key()).c_str(),
+               dformat("codePath=%s, dataPath=%s",
+                       codePath.c_str(), dataPath.c_str()).c_str());
+
+    /* gogogo */
+    debug_post(577, 0);
+    backend->loadAll(codePath.c_str(), dataPath.c_str());
+    return 0;
+}
+
 unsigned Mothership::handle_msg_app_spec(PMsg_p* message)
 {
     AppInfo* appInfo;
@@ -87,8 +109,9 @@ unsigned Mothership::handle_msg_app_spec(PMsg_p* message)
     std::string appName;
     uint32_t distCount;
     uint8_t appNumber;
+    bool soloApp;
     if (!decode_app_spec_message(message, &appName, &distCount,
-                                 &appNumber))
+                                 &appNumber, &soloApp))
     {
         debug_post(597, 3, "Q::APP,Q::SPEC", hex2str(message->Key()).c_str(),
                    "Failed to decode.");
@@ -96,12 +119,13 @@ unsigned Mothership::handle_msg_app_spec(PMsg_p* message)
     }
 
     debug_post(597, 3, "Q::APP,Q::SPEC", hex2str(message->Key()).c_str(),
-               dformat("appName=%s, distCount=%u, appNumber=%u",
-                       appName.c_str(), distCount, appNumber).c_str());
+               dformat("appName=%s, distCount=%u, appNumber=%u, soloApp=%s",
+                       appName.c_str(), distCount, appNumber,
+                       soloApp ? "true" : "false").c_str());
 
     /* Ensure application existence idempotently (it might have been created by
      * an AppDist message). */
-    appInfo = appdb.check_create_app(appName, distCount);
+    appInfo = appdb.check_create_app(appName, distCount, soloApp);
 
     /* If the application is not in the UNDERDEFINED state, post bossily and do
      * nothing else. */
diff --git a/Source/Mothership/MessageUtils.cpp b/Source/Mothership/MessageUtils.cpp
index 814a3c43..75909343 100644
--- a/Source/Mothership/MessageUtils.cpp
+++ b/Source/Mothership/MessageUtils.cpp
@@ -10,6 +10,16 @@
 
 #include "Mothership.h"
 
+bool Mothership::decode_app_empt_message(
+    PMsg_p* message, std::string* codePath, std::string* dataPath)
+{
+    codePath->clear();
+    dataPath->clear();
+    if(!decode_string_message(message, codePath)) return false;
+    if(!decode_string_message(message, dataPath, 1)) return false;
+    return true;
+}
+
 bool Mothership::decode_app_dist_message(
     PMsg_p* message, std::string* appName, std::string* codePath,
     std::string* dataPath, uint32_t* coreAddr,
@@ -38,12 +48,14 @@ bool Mothership::decode_app_supd_message(PMsg_p* message, std::string* appName,
 
 bool Mothership::decode_app_spec_message(PMsg_p* message, std::string* appName,
                                          uint32_t* distCount,
-                                         uint8_t* appNumber)
+                                         uint8_t* appNumber,
+                                         bool* soloApp)
 {
     *distCount = 0;
     if(!decode_string_message(message, appName)) return false;
     if(!decode_unsigned_message(message, distCount, 1)) return false;
     if(!decode_char_message(message, appNumber, 2)) return false;
+    if(!decode_bool_message(message, soloApp, 3)) return false;
     return true;
 }
 
@@ -77,9 +89,9 @@ bool Mothership::decode_addressed_packets_message(PMsg_p* message,
     message->Put<P_Addr_Pkt_t>();  // Tell the message its type
 
     packets->clear();
-    
+
     message->Get<P_Addr_Pkt_t>(index, *packets);
-    
+
     if (packets->empty())
     {
         Post(516, hex2str(message->Key()), uint2str(index));
@@ -89,6 +101,24 @@ bool Mothership::decode_addressed_packets_message(PMsg_p* message,
     return true;
 }
 
+bool Mothership::decode_bool_message(PMsg_p* message, bool* result,
+                                     unsigned index)
+{
+    int countBuffer;
+    bool* resultBuffer;
+
+    /* Get and check for errors. */
+    resultBuffer = message->Get<bool>(index, countBuffer);
+    if (resultBuffer == PNULL)
+    {
+        *result = 0;
+        Post(537, hex2str(message->Key()), uint2str(index));
+        return false;
+    }
+    *result = *resultBuffer;
+    return true;
+}
+
 bool Mothership::decode_char_message(PMsg_p* message, unsigned char* result,
                                      unsigned index)
 {
@@ -120,7 +150,7 @@ bool Mothership::decode_packets_message(PMsg_p* message,
     packets->clear();
 
     message->Get<P_Pkt_t>(index, *packets);
-    
+
     // If the packet vector has come back empty, there is an error.
     if (packets->empty())
     {
diff --git a/Source/Mothership/Mothership.cpp b/Source/Mothership/Mothership.cpp
index 35f7a471..7052ee70 100644
--- a/Source/Mothership/Mothership.cpp
+++ b/Source/Mothership/Mothership.cpp
@@ -196,6 +196,7 @@ void Mothership::setup_mpi_hooks()
     DebugPrint("[MOTHERSHIP] Setting up MPI hooks.\n");
     FnMap[PMsg_p::KEY(Q::EXIT)] = &Mothership::handle_msg_exit;
     FnMap[PMsg_p::KEY(Q::SYST,Q::KILL)] = &Mothership::handle_msg_syst_kill;
+    FnMap[PMsg_p::KEY(Q::APP,Q::EMPT)] = &Mothership::handle_msg_cnc;
     FnMap[PMsg_p::KEY(Q::APP,Q::SPEC)] = &Mothership::handle_msg_cnc;
     FnMap[PMsg_p::KEY(Q::APP,Q::DIST)] = &Mothership::handle_msg_cnc;
     FnMap[PMsg_p::KEY(Q::APP,Q::SUPD)] = &Mothership::handle_msg_cnc;
diff --git a/Source/Mothership/Mothership.h b/Source/Mothership/Mothership.h
index b3fc99ea..bc72ca59 100644
--- a/Source/Mothership/Mothership.h
+++ b/Source/Mothership/Mothership.h
@@ -51,6 +51,7 @@ class Mothership: public CommonBase
     void recall_application(AppInfo*);
 
     /* Methods for handling MPI messages (called by consumer threads). */
+    unsigned handle_msg_app_empt(PMsg_p* message);
     unsigned handle_msg_app_spec(PMsg_p* message);
     unsigned handle_msg_app_dist(PMsg_p* message);
     unsigned handle_msg_app_supd(PMsg_p* message);
@@ -95,6 +96,8 @@ class Mothership: public CommonBase
 
     /* Methods for safely decoding MPI messages with certain field
      * configurations. */
+    bool decode_app_empt_message(PMsg_p* message, std::string* codePath,
+                                 std::string* dataPath);
     bool decode_app_dist_message(PMsg_p* message, std::string* appName,
                                  std::string* codePath, std::string* dataPath,
                                  uint32_t* coreAddr,
@@ -102,12 +105,14 @@ class Mothership: public CommonBase
     bool decode_app_supd_message(PMsg_p* message, std::string* appName,
                                  std::string* soPath);
     bool decode_app_spec_message(PMsg_p* message, std::string* appName,
-                                 uint32_t* distCount, uint8_t* appNumber);
+                                 uint32_t* distCount, uint8_t* appNumber,
+                                 bool* soloApp);
     bool decode_addresses_message(PMsg_p* message,
                                   std::vector<uint32_t>* addresses,
                                   unsigned index=0);
     bool decode_addressed_packets_message(PMsg_p* message,
         std::vector<P_Addr_Pkt_t>* packets, unsigned index=0);
+    bool decode_bool_message(PMsg_p* message, bool* result, unsigned index=0);
     bool decode_char_message(PMsg_p* message, unsigned char* result,
                              unsigned index=0);
     bool decode_packets_message(PMsg_p* message,
diff --git a/Source/Mothership/ThreadLogic.cpp b/Source/Mothership/ThreadLogic.cpp
index f69d910b..bc9ee9ab 100644
--- a/Source/Mothership/ThreadLogic.cpp
+++ b/Source/Mothership/ThreadLogic.cpp
@@ -55,7 +55,9 @@ void* ThreadComms::mpi_cnc_resolver(void* mothershipArg)
              messageIt++)
         {
             key = messageIt->Key();
-            if (key == PMsg_p::KEY(Q::APP, Q::SPEC))
+            if (key == PMsg_p::KEY(Q::APP, Q::EMPT))
+                mothership->handle_msg_app_empt(&*messageIt);
+            else if (key == PMsg_p::KEY(Q::APP, Q::SPEC))
                 mothership->handle_msg_app_spec(&*messageIt);
             else if (key == PMsg_p::KEY(Q::APP, Q::DIST))
                 mothership->handle_msg_app_dist(&*messageIt);
diff --git a/Source/OrchBase/Composer.cpp b/Source/OrchBase/Composer.cpp
index 665c0958..901a0f84 100644
--- a/Source/OrchBase/Composer.cpp
+++ b/Source/OrchBase/Composer.cpp
@@ -38,6 +38,9 @@ ComposerGraphI_t::ComposerGraphI_t()
     
     compilationFlags = "";
     provenanceCache = "";
+    
+    idleInstructionBinary = "";
+    idleDataBinary = "";
 }
 
 ComposerGraphI_t::ComposerGraphI_t(GraphI_t* graphIIn, std::string& outputPath)
@@ -59,6 +62,9 @@ ComposerGraphI_t::ComposerGraphI_t(GraphI_t* graphIIn, std::string& outputPath)
     
     compilationFlags = "";
     provenanceCache = "";
+    
+    idleInstructionBinary = "";
+    idleDataBinary = "";
 }
 
 ComposerGraphI_t::~ComposerGraphI_t()
@@ -1017,6 +1023,34 @@ bool Composer::isCompiled(GraphI_t* graphI)
     return builderGraphI->compiled;
 }
 
+/******************************************************************************
+ * Public method to get the paths for the HW Idle binaries
+ *****************************************************************************/
+bool Composer::getDummyPaths(GraphI_t* graphI, std::string& instrBin, 
+                                std::string& dataBin)
+{
+    ComposerGraphI_t* builderGraphI;
+
+    ComposerGraphIMap_t::iterator srch = graphIMap.find(graphI);
+    if (srch == graphIMap.end())
+    {   // The Graph Instance has not been seen before, so not compiled.
+        return false;
+
+    } else {
+        builderGraphI = srch->second;
+    }
+    
+    if(builderGraphI->idleInstructionBinary == "" || 
+        builderGraphI->idleDataBinary == "")
+    {   // We are missing a binary path, return false.
+        return false;
+    }
+    
+    instrBin = builderGraphI->idleInstructionBinary;
+    dataBin = builderGraphI->idleDataBinary;
+    return true;
+}
+
 /******************************************************************************
  * Invoke a clean and then a degenerate
  *****************************************************************************/
diff --git a/Source/OrchBase/Composer.h b/Source/OrchBase/Composer.h
index f7293064..69c62aba 100644
--- a/Source/OrchBase/Composer.h
+++ b/Source/OrchBase/Composer.h
@@ -143,6 +143,8 @@ int         addFlags(GraphI_t*, std::string&);
 bool        isGenerated(GraphI_t*);
 bool        isCompiled(GraphI_t*);
 
+bool        getDummyPaths(GraphI_t*, std::string&, std::string&);   // Get the hardware idle binary names 
+
 void        Show(FILE * = stdout);
 void        Dump(unsigned = 0,FILE * = stdout);
 
diff --git a/Source/OrchBase/Handlers/CmDepl.cpp b/Source/OrchBase/Handlers/CmDepl.cpp
index a4ab09fe..688d8742 100644
--- a/Source/OrchBase/Handlers/CmDepl.cpp
+++ b/Source/OrchBase/Handlers/CmDepl.cpp
@@ -1,8 +1,8 @@
 //------------------------------------------------------------------------------
 
 #include "CmDepl.h"
-#include "OrchBase.h"
 #include "Pglobals.h"
+#include "Root.h"  /* Grabs Orchestrator config, and OrchBase. */
 #include "SupervisorModes.h"
 
 //==============================================================================
@@ -145,6 +145,7 @@ int CmDepl::DeployGraph(GraphI_t* gi)
     PMsg_p specMessage;
     PMsg_p distMessage;
     PMsg_p supdMessage;
+    PMsg_p emptMessage;
     std::vector<PMsg_p*> messages;
     std::vector<PMsg_p*>::iterator messageIt;
 
@@ -347,6 +348,7 @@ int CmDepl::DeployGraph(GraphI_t* gi)
     messages.push_back(&specMessage);
     messages.push_back(&distMessage);
     messages.push_back(&supdMessage);
+    messages.push_back(&emptMessage);
     for (messageIt = messages.begin(); messageIt != messages.end();
          messageIt++)
     {
@@ -356,6 +358,7 @@ int CmDepl::DeployGraph(GraphI_t* gi)
     specMessage.Key(Q::APP, Q::SPEC);
     distMessage.Key(Q::APP, Q::DIST);
     supdMessage.Key(Q::APP, Q::SUPD);
+    emptMessage.Key(Q::APP, Q::EMPT);
 
     /* Iterate through participating Motherships. */
     for (mothershipPayloadsIt = mothershipPayloads.begin();
@@ -369,6 +372,31 @@ int CmDepl::DeployGraph(GraphI_t* gi)
             (*messageIt)->Tgt(mothershipPayloadsIt->first);
         }
 
+        /* Customise and send the EMPT message, if configured to use them. */
+        bool soloApp = dynamic_cast<Root *>(par)->pOC->SingleApp();
+        if (soloApp)
+        {
+            std::string codePath;
+            std::string dataPath;
+            
+            // Get the dummy binary paths
+            par->pComposer->getDummyPaths(gi, codePath, dataPath);
+
+            emptMessage.Put(0, &codePath);
+            emptMessage.Put(1, &dataPath);
+            fprintf(par->fd, "Sending EMPT message to Mothership rank %d, "
+                    "with codepath=%s and dataPath=%s...",
+                    mothershipPayloadsIt->first, codePath.c_str(),
+                    dataPath.c_str());
+            emptMessage.Send();
+            fprintf(par->fd, " message sent.\n");
+        }
+        else
+        {
+            fprintf(par->fd, "Not sending EMPT message, as Orchestrator is "
+                    "not configured to operate in single-application mode.\n");
+        }
+
         /* Customise and send the SPEC message. */
         appNumber = 0;  /* This is terrible - only one graph instance can be
                          * loaded at a time! <!> TODO */
@@ -376,9 +404,11 @@ int CmDepl::DeployGraph(GraphI_t* gi)
         specMessage.Put<unsigned>(1, &distCount);
         specMessage.Put<unsigned char>(2,
             static_cast<unsigned char*>(&appNumber));
+        specMessage.Put<bool>(3,&soloApp);
         fprintf(par->fd, "Sending SPEC message to Mothership rank %d, with "
-                "appNumber=%u and distCount=%u...",
-                mothershipPayloadsIt->first, appNumber, distCount);
+                "appNumber=%u, distCount=%u, and soloApp=%s...",
+                mothershipPayloadsIt->first, appNumber, distCount,
+                soloApp ? "true" : "false");
         specMessage.Send();
         fprintf(par->fd, " message sent.\n");
 
diff --git a/Source/Root/OrchConfig.cpp b/Source/Root/OrchConfig.cpp
index 0b93f499..05c41203 100644
--- a/Source/Root/OrchConfig.cpp
+++ b/Source/Root/OrchConfig.cpp
@@ -27,8 +27,8 @@ ecnt = 0;                              // So far, so good, then. No errors
 JNJ P(WhereAmI);                      // Parse defining file
 ecnt = P.ErrCnt();                     // Syntax cockups?
 if (ecnt!=0) {                         // If so, bail
-  if (P.Td.t==Lex::S_0) IncErr(0,6);
-  else IncErr(0,7);
+  if (P.Td.t==Lex::S_0) IncErr(0,7);
+  else IncErr(0,8);
   return;
 }
 vH sects;
@@ -99,6 +99,20 @@ WALKVECTOR(UIF::Node *,sects,i) {      // Walk the sections
       if ((*k)->str=="build"   ) flags.build    = s;
     }
   }
+  if (sn=="modes") {
+    P.GetVari(*i,varis);
+    WALKVECTOR(UIF::Node *,varis,k) {
+      P.LocValu(*k,valus);
+      if (valus.size()>1) IncErr(P.FndRecd(*k),6);
+      if (valus.empty()) s.clear();
+      else s = valus[0]->str;
+      if ((*k)->str=="single_app_mode") {
+        if (s=="false") modes.single_app_mode = false;
+        else if (s=="true") modes.single_app_mode = true;
+        else IncErr(P.FndRecd(*k),6);
+      }
+    }
+  }
 }
 if (ecnt!=0) Init();              // Any errors, kill the lot
 Force2Linux();                    // Force all the separators to linux-land
diff --git a/Source/Root/OrchConfig.h b/Source/Root/OrchConfig.h
index ebbac36b..7a8344cd 100644
--- a/Source/Root/OrchConfig.h
+++ b/Source/Root/OrchConfig.h
@@ -41,6 +41,7 @@ string                   Placement()   { return setup_files.placement;         }
 string                   RemoteMshp()  { return default_paths.remote_mship;    }
 string                   RemoteOut()   { return default_paths.remote_outdir;   }
 string                   Trace()       { return default_paths.trace;           }
+bool                     SingleApp()   { return modes.single_app_mode;         }
 string                   Stage()       { return default_paths.stage;           }
 string                   Supervisors() { return default_paths.supervisors;     }
 string                   Ulog()        { return default_paths.ulog;            }
@@ -86,6 +87,10 @@ struct flags_t {
   string build;                        // Default x-compiler flags
 } flags;
 
+struct modes_t {
+  bool single_app_mode;                // Hardware-idle friendly?
+} modes;
+
 };
 
 //==============================================================================