diff --git a/luprex/Makefile b/luprex/Makefile
index 79c4083d..fe079efa 100644
--- a/luprex/Makefile
+++ b/luprex/Makefile
@@ -1,4 +1,4 @@
-all: main
+
 
 OBJ_ERIS=\
 	obj/eris/lapi.o \
@@ -77,11 +77,6 @@ OBJ_DRV=\
 	obj/drv/sslutil.o\
 
 
--include $(OBJ_ERIS:%.o=%.d)
--include $(OBJ_CORE:%.o=%.d)
--include $(OBJ_DRV:%.o=%.d)
-
-
 ifeq ($(OS),linux)
 
 OPT=-g -O0
@@ -98,10 +93,15 @@ obj/core/%.o: cpp/core/%.cpp
 obj/drv/%.o: cpp/drv/%.cpp
 	g++ $(OPT) -Wall -fvisibility=hidden -std=c++17 -I./ext/openssl -I./src/drv -c -MMD $< -o $@
 
+-include obj/drv/driver-linux.d
+
 endif
 
 clean:
 	rm -f main.exe main obj/*/*.*
 
+-include $(OBJ_ERIS:%.o=%.d)
+-include $(OBJ_CORE:%.o=%.d)
+-include $(OBJ_DRV:%.o=%.d)
 
 
diff --git a/luprex/cpp/core/drivenengine.cpp b/luprex/cpp/core/drivenengine.cpp
index 717d49a5..623061b6 100644
--- a/luprex/cpp/core/drivenengine.cpp
+++ b/luprex/cpp/core/drivenengine.cpp
@@ -744,6 +744,9 @@ static void replay_sent_outgoing(EngineWrapper *w) {
     if ((nbytes > ndata) || (hash != SpookyHash::QkHash64(data, nbytes))) {
         return reset_wrapper(w, "nondeterministic in replay_sent_outgoing");
     }
+    if (w->replay_cb_sent_outgoing != nullptr) {
+        w->replay_cb_sent_outgoing(w->replay_cb_vp, chid, ndata, data);
+    }
     w->engine->drv_sent_outgoing(chid, nbytes);
 }
 
@@ -885,7 +888,6 @@ void replay_set_lua_source(EngineWrapper *w) {
 
 
 static void replaycore_initialize(EngineWrapper *w, const char *logfn) {
-    std::cerr << "Memhash before replaycore_initialize: " << eng::memhash() << std::endl;
     if (w->engine != nullptr) {
         return reset_wrapper(w, "Cannot initialize wrapper, it's already initialized.");
         return;
@@ -904,7 +906,7 @@ static void replaycore_initialize(EngineWrapper *w, const char *logfn) {
     uint8_t code = rlog_uint8(w);
     int hash = rlog_uint32(w);
     if (!w->rlog->good()) {
-        return reset_wrapper(w, "logfile corrupt");
+        return reset_wrapper(w, "logfile corrupt in initial step");
     }
     if (hash != eng::memhash()) {
         return reset_wrapper(w, "nondeterminism detected in initial step");
@@ -926,9 +928,12 @@ static void replaycore_step(EngineWrapper *w) {
     }
 
     uint8_t code = rlog_uint8(w);
+    if (w->rlog->eof()) {
+        return reset_wrapper(w, "logfile terminated abruptly");
+    }
     int hash = rlog_uint32(w);
     if (!w->rlog->good()) {
-        return reset_wrapper(w, "logfile corrupt");
+        return reset_wrapper(w, "logfile corrupt in replay step");
     }
     if (hash != eng::memhash()) {
         return reset_wrapper(w, "nondeterminism detected");
diff --git a/luprex/cpp/core/enginewrapper.hpp b/luprex/cpp/core/enginewrapper.hpp
index e8323df8..b7d9d4a4 100644
--- a/luprex/cpp/core/enginewrapper.hpp
+++ b/luprex/cpp/core/enginewrapper.hpp
@@ -193,6 +193,32 @@ struct EngineWrapper {
     //
     void (*replay_step)(EngineWrapper *w);
 
+    //////////////////////////////////////////////////////////////////////////////
+    //////////////////////////////////////////////////////////////////////////////
+    //
+    // CALLBACKS USED ONLY IN REPLAY MODE
+    //
+    // The driver can store function pointers here.  If it does so, these
+    // functions will get called during replay_step operations. 
+    //
+    //////////////////////////////////////////////////////////////////////////////
+    //////////////////////////////////////////////////////////////////////////////
+
+    void (*replay_cb_sent_outgoing)(void *vp, int chid, int nbytes, const char *data);
+
+    //////////////////////////////////////////////////////////////////////////////
+    //////////////////////////////////////////////////////////////////////////////
+    //
+    // VOID POINTER USED IN REPLAY CALLBACKS
+    //
+    // The driver can store a void pointer here.  This void pointer will get passed
+    // to all the replay callbacks. 
+    //
+    //////////////////////////////////////////////////////////////////////////////
+    //////////////////////////////////////////////////////////////////////////////
+
+    void *replay_cb_vp;
+
     //////////////////////////////////////////////////////////////////////////////
     //////////////////////////////////////////////////////////////////////////////
     //
diff --git a/luprex/cpp/drv/driver-common.cpp b/luprex/cpp/drv/driver-common.cpp
index 8166fd5c..669ff5cb 100644
--- a/luprex/cpp/drv/driver-common.cpp
+++ b/luprex/cpp/drv/driver-common.cpp
@@ -405,6 +405,12 @@ class Driver {
         return 0;
     }
 
+    static void replay_cb_sent_outgoing(void *vp, int chid, int ndata, const char *data) {
+        if (chid == 0) {
+            std::cerr.write(data, ndata);
+        }
+    }
+
     int drive(int argc, char *argv[]) {
         // Remove the program name from argv.
         std::string program = argv[0];
@@ -413,6 +419,7 @@ class Driver {
 
         // Load the DLL and gain access to its functions.
         call_init_engine_wrapper(&engw);
+        engw.replay_cb_sent_outgoing = replay_cb_sent_outgoing;
 
         // If argv contains "replay <filename>", do a replay,
         // and then skip everything else.