diff --git a/build-aux/m4/bitcoin_qt.m4 b/build-aux/m4/bitcoin_qt.m4
index 89f3e188ee02d..25a52173456c6 100644
--- a/build-aux/m4/bitcoin_qt.m4
+++ b/build-aux/m4/bitcoin_qt.m4
@@ -116,8 +116,8 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   BITCOIN_QT_CHECK([
   TEMP_CPPFLAGS=$CPPFLAGS
   TEMP_CXXFLAGS=$CXXFLAGS
-  CPPFLAGS="$QT_INCLUDES $CPPFLAGS"
-  CXXFLAGS="$PIC_FLAGS $CXXFLAGS"
+  CPPFLAGS="$QT_INCLUDES $CORE_CPPFLAGS $CPPFLAGS"
+  CXXFLAGS="$PIC_FLAGS $CORE_CXXFLAGS $CXXFLAGS"
   _BITCOIN_QT_IS_STATIC
   if test "x$bitcoin_cv_static_qt" = xyes; then
     _BITCOIN_QT_CHECK_STATIC_LIBS
@@ -177,8 +177,8 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
     AC_MSG_CHECKING(whether -fPIE can be used with this Qt config)
     TEMP_CPPFLAGS=$CPPFLAGS
     TEMP_CXXFLAGS=$CXXFLAGS
-    CPPFLAGS="$QT_INCLUDES $CPPFLAGS"
-    CXXFLAGS="$PIE_FLAGS $CXXFLAGS"
+    CPPFLAGS="$QT_INCLUDES $CORE_CPPFLAGS $CPPFLAGS"
+    CXXFLAGS="$PIE_FLAGS $CORE_CXXFLAGS $CXXFLAGS"
     AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
         #include <QtCore/qconfig.h>
         #ifndef QT_VERSION
@@ -200,7 +200,7 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
     BITCOIN_QT_CHECK([
     AC_MSG_CHECKING(whether -fPIC is needed with this Qt config)
     TEMP_CPPFLAGS=$CPPFLAGS
-    CPPFLAGS="$QT_INCLUDES $CPPFLAGS"
+    CPPFLAGS="$QT_INCLUDES $CORE_CPPFLAGS $CPPFLAGS"
     AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
         #include <QtCore/qconfig.h>
         #ifndef QT_VERSION
diff --git a/configure.ac b/configure.ac
index 499f539cebb74..af682ac9c17c9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -372,7 +372,9 @@ case $host in
 esac
 
 if test "x$enable_debug" = xyes; then
-  dnl Clear default -g -O2 flags
+  dnl If debugging is enabled, and the user hasn't overriden CXXFLAGS, clear
+  dnl them, to prevent autoconfs "-g -O2" being added. Otherwise we'd end up
+  dnl with "-O0 -g3 -g -O2".
   if test "x$CXXFLAGS_overridden" = xno; then
 	CXXFLAGS=""
   fi
@@ -397,11 +399,11 @@ else
     # Stacktraces will be suboptimal due to optimization, but better than nothing. Also, -fno-omit-frame-pointer
     # mitigates this a little bit
     if test "x$GCC" = xyes; then
-        CFLAGS="$CFLAGS -g1 -fno-omit-frame-pointer"
+        DEBUG_CFLAGS="$DEBUG_CFLAGS -g1 -fno-omit-frame-pointer"
     fi
 
     if test "x$GXX" = xyes; then
-        CXXFLAGS="$CXXFLAGS -g1 -fno-omit-frame-pointer"
+        DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -g1 -fno-omit-frame-pointer"
     fi
 fi
 
@@ -429,7 +431,7 @@ if test x$LINK_WRAP_SUPPORTED = "xyes"; then
 fi
 
 # Needed for MinGW targets when debug symbols are enabled as compiled objects get very large
-AX_CHECK_COMPILE_FLAG([-Wa,-mbig-obj], [CXXFLAGS="$CXXFLAGS -Wa,-mbig-obj"],,,)
+AX_CHECK_COMPILE_FLAG([-Wa,-mbig-obj], [DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -Wa,-mbig-obj"],,,)
 
 if test x$use_sanitizers != x; then
   dnl First check if the compiler accepts flags. If an incompatible pair like
@@ -532,7 +534,7 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
 fi
 
 dnl Don't allow extended (non-ASCII) symbols in identifiers. This is easier for code review.
-AX_CHECK_COMPILE_FLAG([-fno-extended-identifiers],[[CXXFLAGS="$CXXFLAGS -fno-extended-identifiers"]],,[[$CXXFLAG_WERROR]])
+AX_CHECK_COMPILE_FLAG([-fno-extended-identifiers],[[CORE_CXXFLAGS="$CORE_CXXFLAGS -fno-extended-identifiers"]],,[[$CXXFLAG_WERROR]])
 
 enable_arm_crc=no
 enable_arm_shani=no
@@ -683,7 +685,7 @@ CXXFLAGS="$TEMP_CXXFLAGS"
 
 fi
 
-CPPFLAGS="$CPPFLAGS -DHAVE_BUILD_INFO -DGSL_NO_IOSTREAMS"
+CORE_CPPFLAGS="$CORE_CPPFLAGS -DHAVE_BUILD_INFO -DGSL_NO_IOSTREAMS"
 
 AC_ARG_WITH([utils],
   [AS_HELP_STRING([--with-utils],
@@ -755,7 +757,10 @@ case $host in
        AC_MSG_ERROR("windres not found")
      fi
 
-     CPPFLAGS="$CPPFLAGS -D_MT -DWIN32 -D_WINDOWS -D_WIN32_WINNT=0x0601 -D_WIN32_IE=0x0501 -DWIN32_LEAN_AND_MEAN"
+     CORE_CPPFLAGS="$CORE_CPPFLAGS -D_MT -DWIN32 -D_WINDOWS -D_WIN32_WINNT=0x0601 -D_WIN32_IE=0x0501 -DWIN32_LEAN_AND_MEAN"
+     dnl Prevent the definition of min/max macros.
+     dnl We always want to use the standard library.
+     CORE_CPPFLAGS="$CORE_CPPFLAGS -DNOMINMAX"
 
      dnl libtool insists upon adding -nostdlib and a list of objects/libs to link against.
      dnl That breaks our ability to build dll's with static libgcc/libstdc++/libssp. Override
@@ -766,14 +771,14 @@ case $host in
      postdeps_CXX=
 
      dnl We require Windows 7 (NT 6.1) or later
-     AX_CHECK_LINK_FLAG([[-Wl,--major-subsystem-version -Wl,6 -Wl,--minor-subsystem-version -Wl,1]],[LDFLAGS="$LDFLAGS -Wl,--major-subsystem-version -Wl,6 -Wl,--minor-subsystem-version -Wl,1"],,[[$LDFLAG_WERROR]])
+     AX_CHECK_LINK_FLAG([[-Wl,--major-subsystem-version -Wl,6 -Wl,--minor-subsystem-version -Wl,1]],[CORE_LDFLAGS="$CORE_LDFLAGS -Wl,--major-subsystem-version -Wl,6 -Wl,--minor-subsystem-version -Wl,1"],,[[$LDFLAG_WERROR]])
      ;;
   *darwin*)
      TARGET_OS=darwin
      if  test x$cross_compiling != xyes; then
        BUILD_OS=darwin
 
-       AX_CHECK_LINK_FLAG([[-Wl,-headerpad_max_install_names]], [LDFLAGS="$LDFLAGS -Wl,-headerpad_max_install_names"],, [[$LDFLAG_WERROR]])
+       AX_CHECK_LINK_FLAG([[-Wl,-headerpad_max_install_names]], [CORE_LDFLAGS="$CORE_LDFLAGS -Wl,-headerpad_max_install_names"],, [[$LDFLAG_WERROR]])
 
        AC_CHECK_PROG([BREW],brew, brew)
        if test x$BREW = xbrew; then
@@ -800,8 +805,8 @@ case $host in
 
          gmp_prefix=$($BREW --prefix gmp 2>/dev/null)
          if test x$gmp_prefix != x; then
-           CPPFLAGS="$CPPFLAGS -I$gmp_prefix/include"
-           LDFLAGS="$LDFLAGS -L$gmp_prefix/lib"
+           CORE_CPPFLAGS="$CORE_CPPFLAGS -I$gmp_prefix/include"
+           CORE_LDFLAGS="$CORE_LDFLAGS -L$gmp_prefix/lib"
          fi
 
          case $host in
@@ -813,20 +818,20 @@ case $host in
              if test "x$use_upnp" != xno && $BREW list --versions miniupnpc >/dev/null; then
                miniupnpc_prefix=$($BREW --prefix miniupnpc 2>/dev/null)
                if test "x$suppress_external_warnings" != xno; then
-                 CPPFLAGS="$CPPFLAGS -isystem $miniupnpc_prefix/include"
+                 CORE_CPPFLAGS="$CORE_CPPFLAGS -isystem $miniupnpc_prefix/include"
                else
-                 CPPFLAGS="$CPPFLAGS -I$miniupnpc_prefix/include"
+                 CORE_CPPFLAGS="$CORE_CPPFLAGS -I$miniupnpc_prefix/include"
                fi
-               LDFLAGS="$LDFLAGS -L$miniupnpc_prefix/lib"
+               CORE_LDFLAGS="$CORE_LDFLAGS -L$miniupnpc_prefix/lib"
              fi
              if test "x$use_natpmp" != xno && $BREW list --versions libnatpmp >/dev/null; then
                libnatpmp_prefix=$($BREW --prefix libnatpmp 2>/dev/null)
                if test "x$suppress_external_warnings" != xno; then
-                 CPPFLAGS="$CPPFLAGS -isystem $libnatpmp_prefix/include"
+                 CORE_CPPFLAGS="$CORE_CPPFLAGS -isystem $libnatpmp_prefix/include"
                else
-                 CPPFLAGS="$CPPFLAGS -I$libnatpmp_prefix/include"
+                 CORE_CPPFLAGS="$CORE_CPPFLAGS -I$libnatpmp_prefix/include"
                fi
-               LDFLAGS="$LDFLAGS -L$libnatpmp_prefix/lib"
+               CORE_LDFLAGS="$CORE_LDFLAGS -L$libnatpmp_prefix/lib"
              fi
              ;;
          esac
@@ -849,7 +854,7 @@ case $host in
        esac
      fi
 
-     CPPFLAGS="$CPPFLAGS -DMAC_OSX -DOBJC_OLD_DISPATCH_PROTOTYPES=0"
+     CORE_CPPFLAGS="$CORE_CPPFLAGS -DMAC_OSX -DOBJC_OLD_DISPATCH_PROTOTYPES=0"
      OBJCXXFLAGS="$CXXFLAGS"
      ;;
    *android*)
@@ -912,11 +917,17 @@ if test x$use_lcov = xyes; then
   AC_SUBST(COV_TOOL_WRAPPER, "cov_tool_wrapper.sh")
   LCOV="$LCOV --gcov-tool $(pwd)/$COV_TOOL_WRAPPER"
 
-  AX_CHECK_LINK_FLAG([[--coverage]], [LDFLAGS="$LDFLAGS --coverage"],
+  AX_CHECK_LINK_FLAG([[--coverage]], [CORE_LDFLAGS="$CORE_LDFLAGS --coverage"],
     [AC_MSG_ERROR("lcov testing requested but --coverage linker flag does not work")])
-  AX_CHECK_COMPILE_FLAG([--coverage],[CXXFLAGS="$CXXFLAGS --coverage"],
+  AX_CHECK_COMPILE_FLAG([--coverage],[CORE_CXXFLAGS="$CORE_CXXFLAGS --coverage"],
     [AC_MSG_ERROR("lcov testing requested but --coverage flag does not work")])
-  CXXFLAGS="$CXXFLAGS -Og"
+  dnl If coverage is enabled, and the user hasn't overriden CXXFLAGS, clear
+  dnl them, to prevent autoconfs "-g -O2" being added. Otherwise we'd end up
+  dnl with "--coverage -Og -O0 -g -O2".
+  if test "$CXXFLAGS_overridden" = "no"; then
+  CXXFLAGS=""
+  fi
+  CORE_CXXFLAGS="$CORE_CXXFLAGS -Og -O0"
 fi
 
 if test x$use_lcov_branch != xno; then
@@ -942,13 +953,13 @@ AC_FUNC_STRERROR_R
 if test x$ac_cv_sys_file_offset_bits != x &&
    test x$ac_cv_sys_file_offset_bits != xno &&
    test x$ac_cv_sys_file_offset_bits != xunknown; then
-  CPPFLAGS="$CPPFLAGS -D_FILE_OFFSET_BITS=$ac_cv_sys_file_offset_bits"
+  CORE_CPPFLAGS="$CORE_CPPFLAGS -D_FILE_OFFSET_BITS=$ac_cv_sys_file_offset_bits"
 fi
 
 if test x$ac_cv_sys_large_files != x &&
    test x$ac_cv_sys_large_files != xno &&
    test x$ac_cv_sys_large_files != xunknown; then
-  CPPFLAGS="$CPPFLAGS -D_LARGE_FILES=$ac_cv_sys_large_files"
+  CORE_CPPFLAGS="$CORE_CPPFLAGS -D_LARGE_FILES=$ac_cv_sys_large_files"
 fi
 
 if test "x$enable_gprof" = xyes; then
@@ -1037,8 +1048,8 @@ dnl These flags are specific to ld64, and may cause issues with other linkers.
 dnl For example: GNU ld will interpret -dead_strip as -de and then try and use
 dnl "ad_strip" as the symbol for the entry point.
 if test x$TARGET_OS = xdarwin; then
-  AX_CHECK_LINK_FLAG([[-Wl,-dead_strip]], [LDFLAGS="$LDFLAGS -Wl,-dead_strip"],, [[$LDFLAG_WERROR]])
-  AX_CHECK_LINK_FLAG([[-Wl,-dead_strip_dylibs]], [LDFLAGS="$LDFLAGS -Wl,-dead_strip_dylibs"],, [[$LDFLAG_WERROR]])
+  AX_CHECK_LINK_FLAG([[-Wl,-dead_strip]], [CORE_LDFLAGS="$CORE_LDFLAGS -Wl,-dead_strip"],, [[$LDFLAG_WERROR]])
+  AX_CHECK_LINK_FLAG([[-Wl,-dead_strip_dylibs]], [CORE_LDFLAGS="$CORE_LDFLAGS -Wl,-dead_strip_dylibs"],, [[$LDFLAG_WERROR]])
   AX_CHECK_LINK_FLAG([[-Wl,-fixup_chains]], [HARDENED_LDFLAGS="$HARDENED_LDFLAGS -Wl,-fixup_chains"], [], [[$LDFLAG_WERROR]])
 fi
 
@@ -1048,7 +1059,6 @@ AC_CHECK_DECLS([getifaddrs, freeifaddrs],[CHECK_SOCKET],,
     [#include <sys/types.h>
     #include <ifaddrs.h>]
 )
-AC_CHECK_DECLS([strnlen])
 
 dnl These are used for daemonization in dashd
 AC_CHECK_DECLS([fork])
@@ -1361,7 +1371,7 @@ if test "x$enable_fuzz" = "xyes"; then
     [[-fsanitize=$use_sanitizers]],
     [AC_MSG_RESULT([no])],
     [AC_MSG_RESULT([yes])
-     CPPFLAGS="$CPPFLAGS -DPROVIDE_FUZZ_MAIN_FUNCTION"],
+     CORE_CPPFLAGS="$CORE_CPPFLAGS -DPROVIDE_FUZZ_MAIN_FUNCTION"],
     [],
     [AC_LANG_PROGRAM([[
       #include <cstdint>
@@ -1385,7 +1395,7 @@ else
       QT_TEST_INCLUDES=SUPPRESS_WARNINGS($QT_TEST_INCLUDES)
     fi
 
-    CPPFLAGS="$CPPFLAGS -DPROVIDE_FUZZ_MAIN_FUNCTION"
+    CORE_CPPFLAGS="$CORE_CPPFLAGS -DPROVIDE_FUZZ_MAIN_FUNCTION"
 fi
 
 if test x$enable_wallet != xno; then
@@ -1518,7 +1528,7 @@ fi
 
 dnl Check for reduced exports
 if test x$use_reduce_exports = xyes; then
-    AX_CHECK_COMPILE_FLAG([-fvisibility=hidden],[CXXFLAGS="$CXXFLAGS -fvisibility=hidden"],
+    AX_CHECK_COMPILE_FLAG([-fvisibility=hidden],[CORE_CXXFLAGS="$CORE_CXXFLAGS -fvisibility=hidden"],
     [AC_MSG_ERROR([Cannot set hidden symbol visibility. Use --disable-reduce-exports.])],[[$CXXFLAG_WERROR]])
     AX_CHECK_LINK_FLAG([[-Wl,--exclude-libs,ALL]],[RELDFLAGS="-Wl,--exclude-libs,ALL"],,[[$LDFLAG_WERROR]])
     AX_CHECK_LINK_FLAG([-Wl,-no_exported_symbols], [LIBTOOL_APP_LDFLAGS="$LIBTOOL_APP_LDFLAGS -Wl,-no_exported_symbols"], [], [$LDFLAG_WERROR])
@@ -1870,10 +1880,14 @@ AC_SUBST(BITCOIN_MP_NODE_NAME)
 AC_SUBST(BITCOIN_MP_GUI_NAME)
 
 AC_SUBST(RELDFLAGS)
+AC_SUBST(CORE_LDFLAGS)
+AC_SUBST(CORE_CPPFLAGS)
+AC_SUBST(CORE_CXXFLAGS)
+AC_SUBST(DEBUG_CFLAGS)
 AC_SUBST(DEBUG_CPPFLAGS)
+AC_SUBST(DEBUG_CXXFLAGS)
 AC_SUBST(WARN_CXXFLAGS)
 AC_SUBST(NOWARN_CXXFLAGS)
-AC_SUBST(DEBUG_CXXFLAGS)
 AC_SUBST(ERROR_CXXFLAGS)
 AC_SUBST(GPROF_CXXFLAGS)
 AC_SUBST(GPROF_LDFLAGS)
@@ -1995,10 +2009,10 @@ echo "  target os           = $host_os"
 echo "  build os            = $build_os"
 echo
 echo "  CC                  = $CC"
-echo "  CFLAGS              = $PTHREAD_CFLAGS $CFLAGS"
-echo "  CPPFLAGS            = $DEBUG_CPPFLAGS $HARDENED_CPPFLAGS $CPPFLAGS"
+echo "  CFLAGS              = $DEBUG_CFLAGS $PTHREAD_CFLAGS $CFLAGS"
+echo "  CPPFLAGS            = $DEBUG_CPPFLAGS $HARDENED_CPPFLAGS $CORE_CPPFLAGS $CPPFLAGS"
 echo "  CXX                 = $CXX"
-echo "  CXXFLAGS            = $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $WARN_CXXFLAGS $NOWARN_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $CXXFLAGS"
-echo "  LDFLAGS             = $PTHREAD_LIBS $HARDENED_LDFLAGS $GPROF_LDFLAGS $LDFLAGS"
+echo "  CXXFLAGS            = $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $WARN_CXXFLAGS $NOWARN_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $CORE_CXXFLAGS $CXXFLAGS"
+echo "  LDFLAGS             = $PTHREAD_LIBS $HARDENED_LDFLAGS $GPROF_LDFLAGS $CORE_LDFLAGS $LDFLAGS"
 echo "  ARFLAGS             = $ARFLAGS"
 echo
diff --git a/src/Makefile.am b/src/Makefile.am
index 55ffd7a6c6905..3b714b247cecd 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -9,9 +9,10 @@ print-%: FORCE
 
 DIST_SUBDIRS = secp256k1
 
-AM_LDFLAGS = $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(GPROF_LDFLAGS) $(SANITIZER_LDFLAGS)
-AM_CXXFLAGS = $(DEBUG_CXXFLAGS) $(HARDENED_CXXFLAGS) $(WARN_CXXFLAGS) $(NOWARN_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS) $(SANITIZER_CXXFLAGS)
-AM_CPPFLAGS = $(DEBUG_CPPFLAGS) $(HARDENED_CPPFLAGS)
+AM_LDFLAGS = $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(GPROF_LDFLAGS) $(SANITIZER_LDFLAGS) $(CORE_LDFLAGS)
+AM_CFLAGS = $(DEBUG_CFLAGS)
+AM_CXXFLAGS = $(DEBUG_CXXFLAGS) $(HARDENED_CXXFLAGS) $(WARN_CXXFLAGS) $(NOWARN_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS) $(SANITIZER_CXXFLAGS) $(CORE_CXXFLAGS)
+AM_CPPFLAGS = $(DEBUG_CPPFLAGS) $(HARDENED_CPPFLAGS) $(CORE_CPPFLAGS)
 AM_LIBTOOLFLAGS = --preserve-dup-deps
 PTHREAD_FLAGS = $(PTHREAD_CFLAGS) $(PTHREAD_LIBS)
 EXTRA_LIBRARIES =
@@ -162,9 +163,9 @@ BITCOIN_CORE_H = \
   coinjoin/util.h \
   coins.h \
   common/bloom.h \
-  compat.h \
   compat/assumptions.h \
   compat/byteswap.h \
+  compat/compat.h \
   compat/cpuid.h \
   compat/endian.h \
   compressor.h \
@@ -279,7 +280,7 @@ BITCOIN_CORE_H = \
   node/psbt.h \
   node/transaction.h \
   node/txreconciliation.h \
-  node/ui_interface.h \
+  node/interface_ui.h \
   node/utxo_snapshot.h \
   noui.h \
   outputtype.h \
@@ -512,7 +513,7 @@ libbitcoin_server_a_SOURCES = \
   node/psbt.cpp \
   node/transaction.cpp \
   node/txreconciliation.cpp \
-  node/ui_interface.cpp \
+  node/interface_ui.cpp \
   noui.cpp \
   policy/fees.cpp \
   policy/packages.cpp \
@@ -792,7 +793,6 @@ libbitcoin_util_a_SOURCES = \
   support/lockedpool.cpp \
   chainparamsbase.cpp \
   clientversion.cpp \
-  compat/strnlen.cpp \
   fs.cpp \
   interfaces/echo.cpp \
   interfaces/handler.cpp \
diff --git a/src/banman.cpp b/src/banman.cpp
index c162eb08fde09..d319a2a996476 100644
--- a/src/banman.cpp
+++ b/src/banman.cpp
@@ -6,7 +6,7 @@
 #include <banman.h>
 
 #include <netaddress.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <sync.h>
 #include <util/system.h>
 #include <util/time.h>
diff --git a/src/bitcoin-cli.cpp b/src/bitcoin-cli.cpp
index 045cf0ae76cd2..43790e9ac4d6e 100644
--- a/src/bitcoin-cli.cpp
+++ b/src/bitcoin-cli.cpp
@@ -10,7 +10,7 @@
 
 #include <chainparamsbase.h>
 #include <clientversion.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <compat/stdin.h>
 #include <policy/feerate.h>
 #include <rpc/client.h>
diff --git a/src/bitcoin-tx.cpp b/src/bitcoin-tx.cpp
index 0eb122f086cc5..cb40879f8e919 100644
--- a/src/bitcoin-tx.cpp
+++ b/src/bitcoin-tx.cpp
@@ -9,7 +9,7 @@
 #include <chainparams.h>
 #include <clientversion.h>
 #include <coins.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <consensus/consensus.h>
 #include <core_io.h>
 #include <key_io.h>
diff --git a/src/bitcoin-wallet.cpp b/src/bitcoin-wallet.cpp
index 8e7c1490fd14b..4dfb973042223 100644
--- a/src/bitcoin-wallet.cpp
+++ b/src/bitcoin-wallet.cpp
@@ -8,7 +8,7 @@
 
 #include <chainparams.h>
 #include <chainparamsbase.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <logging.h>
 #include <util/strencodings.h>
 #include <util/system.h>
diff --git a/src/bitcoind.cpp b/src/bitcoind.cpp
index d026c7c1f3690..a3b9910e2d1c3 100644
--- a/src/bitcoind.cpp
+++ b/src/bitcoind.cpp
@@ -10,12 +10,12 @@
 
 #include <chainparams.h>
 #include <clientversion.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <init.h>
 #include <interfaces/chain.h>
 #include <interfaces/init.h>
 #include <node/context.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <noui.h>
 #include <shutdown.h>
 #include <util/check.h>
diff --git a/src/compat/assumptions.h b/src/compat/assumptions.h
index 487ab9aa9e873..0298f78b96def 100644
--- a/src/compat/assumptions.h
+++ b/src/compat/assumptions.h
@@ -8,6 +8,7 @@
 #ifndef BITCOIN_COMPAT_ASSUMPTIONS_H
 #define BITCOIN_COMPAT_ASSUMPTIONS_H
 
+#include <cstddef>
 #include <limits>
 
 // Assumption: We assume that the macro NDEBUG is not defined.
diff --git a/src/compat.h b/src/compat/compat.h
similarity index 74%
rename from src/compat.h
rename to src/compat/compat.h
index 41f2cd7398604..5dd73eb717caa 100644
--- a/src/compat.h
+++ b/src/compat/compat.h
@@ -3,24 +3,24 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#ifndef BITCOIN_COMPAT_H
-#define BITCOIN_COMPAT_H
+#ifndef BITCOIN_COMPAT_COMPAT_H
+#define BITCOIN_COMPAT_COMPAT_H
 
 #if defined(HAVE_CONFIG_H)
 #include <config/bitcoin-config.h>
 #endif
 
+// Windows defines FD_SETSIZE to 64 (see _fd_types.h in mingw-w64),
+// which is too small for our usage, but allows us to redefine it safely.
+// We redefine it to be 1024, to match glibc, see typesizes.h.
 #ifdef WIN32
-#ifndef NOMINMAX
-#define NOMINMAX
-#endif
 #ifdef FD_SETSIZE
-#undef FD_SETSIZE // prevent redefinition compiler warning
+#undef FD_SETSIZE
 #endif
-#define FD_SETSIZE 1024 // max number of fds in fd_set
+#define FD_SETSIZE 1024
 #include <winsock2.h>
 #include <ws2tcpip.h>
-#include <stdint.h>
+#include <cstdint>
 #else
 #include <fcntl.h>
 #include <sys/mman.h>
@@ -37,54 +37,46 @@
 #include <unistd.h>
 #endif
 
+// We map Linux / BSD error functions and codes, to the equivalent
+// Windows definitions, and use the WSA* names throughout our code.
+// Note that glibc defines EWOULDBLOCK as EAGAIN (see errno.h).
 #ifndef WIN32
 typedef unsigned int SOCKET;
-#include <errno.h>
+#include <cerrno>
 #define WSAGetLastError()   errno
 #define WSAEINVAL           EINVAL
-#define WSAEALREADY         EALREADY
 #define WSAEWOULDBLOCK      EWOULDBLOCK
 #define WSAEAGAIN           EAGAIN
 #define WSAEMSGSIZE         EMSGSIZE
 #define WSAEINTR            EINTR
 #define WSAEINPROGRESS      EINPROGRESS
 #define WSAEADDRINUSE       EADDRINUSE
-#define WSAENOTSOCK         EBADF
 #define INVALID_SOCKET      (SOCKET)(~0)
 #define SOCKET_ERROR        -1
 #define SD_SEND             SHUT_WR
 #else
-#ifndef WSAEAGAIN
+// WSAEAGAIN doesn't exist on Windows
 #ifdef EAGAIN
 #define WSAEAGAIN EAGAIN
 #else
 #define WSAEAGAIN WSAEWOULDBLOCK
 #endif
 #endif
-#endif
 
-#ifdef WIN32
-#ifndef S_IRUSR
-#define S_IRUSR             0400
-#define S_IWUSR             0200
-#endif
-#else
+// Windows defines MAX_PATH as it's maximum path length.
+// We define MAX_PATH for use on non-Windows systems.
+#ifndef WIN32
 #define MAX_PATH            1024
 #endif
+
+// ssize_t is POSIX, and not present when using MSVC.
 #ifdef _MSC_VER
-#if !defined(ssize_t)
-#ifdef _WIN64
-typedef int64_t ssize_t;
-#else
-typedef int32_t ssize_t;
-#endif
+#include <BaseTsd.h>
+typedef SSIZE_T ssize_t;
 #endif
-#endif
-
-#if HAVE_DECL_STRNLEN == 0
-size_t strnlen( const char *start, size_t max_len);
-#endif // HAVE_DECL_STRNLEN
 
+// The type of the option value passed to getsockopt & setsockopt
+// differs between Windows and non-Windows.
 #ifndef WIN32
 typedef void* sockopt_arg_type;
 #else
@@ -135,4 +127,4 @@ bool static inline IsSelectableSocket(const SOCKET& s) {
 #define MSG_DONTWAIT 0
 #endif
 
-#endif // BITCOIN_COMPAT_H
+#endif // BITCOIN_COMPAT_COMPAT_H
diff --git a/src/compat/strnlen.cpp b/src/compat/strnlen.cpp
deleted file mode 100644
index 72b69953d0af5..0000000000000
--- a/src/compat/strnlen.cpp
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright (c) 2009-2014 The Bitcoin Core developers
-// Distributed under the MIT software license, see the accompanying
-// file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
-#if defined(HAVE_CONFIG_H)
-#include <config/bitcoin-config.h>
-#endif
-
-#include <cstring>
-
-#if HAVE_DECL_STRNLEN == 0
-size_t strnlen( const char *start, size_t max_len)
-{
-    const char *end = (const char *)memchr(start, '\0', max_len);
-
-    return end ? (size_t)(end - start) : max_len;
-}
-#endif // HAVE_DECL_STRNLEN
\ No newline at end of file
diff --git a/src/fs.cpp b/src/fs.cpp
index 7e216099adb8d..03afb11ba4091 100644
--- a/src/fs.cpp
+++ b/src/fs.cpp
@@ -11,9 +11,6 @@
 #include <sys/utsname.h>
 #include <unistd.h>
 #else
-#ifndef NOMINMAX
-#define NOMINMAX
-#endif
 #include <codecvt>
 #include <limits>
 #include <windows.h>
diff --git a/src/httpserver.cpp b/src/httpserver.cpp
index 504f3cf642190..b4b263eb50488 100644
--- a/src/httpserver.cpp
+++ b/src/httpserver.cpp
@@ -10,7 +10,7 @@
 
 #include <chainparamsbase.h>
 #include <netbase.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <rpc/protocol.h> // For HTTP status codes
 #include <shutdown.h>
 #include <sync.h>
diff --git a/src/i2p.cpp b/src/i2p.cpp
index 507bdeab55ac8..8ecb50645fe2e 100644
--- a/src/i2p.cpp
+++ b/src/i2p.cpp
@@ -3,7 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chainparams.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <compat/endian.h>
 #include <crypto/sha256.h>
 #include <fs.h>
diff --git a/src/i2p.h b/src/i2p.h
index f9619de9c5f1a..fc9256160b096 100644
--- a/src/i2p.h
+++ b/src/i2p.h
@@ -5,7 +5,7 @@
 #ifndef BITCOIN_I2P_H
 #define BITCOIN_I2P_H
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <fs.h>
 #include <netaddress.h>
 #include <sync.h>
diff --git a/src/index/base.cpp b/src/index/base.cpp
index cae1cc75fd72b..9cc326b9e96ba 100644
--- a/src/index/base.cpp
+++ b/src/index/base.cpp
@@ -5,7 +5,7 @@
 #include <chainparams.h>
 #include <index/base.h>
 #include <node/blockstorage.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <shutdown.h>
 #include <tinyformat.h>
 #include <util/thread.h>
diff --git a/src/init.cpp b/src/init.cpp
index 147f845859813..e85721ce74637 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -39,7 +39,7 @@
 #include <netgroup.h>
 #include <node/blockstorage.h>
 #include <node/context.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <node/txreconciliation.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
@@ -1441,11 +1441,6 @@ bool AppInitLockDataDirectory()
 bool AppInitInterfaces(NodeContext& node)
 {
     node.chain = interfaces::MakeChain(node);
-    // Create client interfaces for wallets that are supposed to be loaded
-    // according to -wallet and -disablewallet options. This only constructs
-    // the interfaces, it doesn't load wallet data. Wallets actually get loaded
-    // when load() and start() interface methods are called below.
-    g_wallet_init_interface.Construct(node);
     return true;
 }
 
@@ -1515,11 +1510,17 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
     GetMainSignals().RegisterBackgroundSignalScheduler(*node.scheduler);
 
-    tableRPC.InitPlatformRestrictions();
+    // Create client interfaces for wallets that are supposed to be loaded
+    // according to -wallet and -disablewallet options. This only constructs
+    // the interfaces, it doesn't load wallet data. Wallets actually get loaded
+    // when load() and start() interface methods are called below.
+    g_wallet_init_interface.Construct(node);
+    uiInterface.InitWallet();
 
     /* Register RPC commands regardless of -server setting so they will be
      * available in the GUI RPC console even if external calls are disabled.
      */
+    tableRPC.InitPlatformRestrictions();
     RegisterAllCoreRPCCommands(tableRPC);
     for (const auto& client : node.chain_clients) {
         client->registerRpcs();
diff --git a/src/init/common.cpp b/src/init/common.cpp
index 2a83ae16b7da4..f775810a72765 100644
--- a/src/init/common.cpp
+++ b/src/init/common.cpp
@@ -11,7 +11,7 @@
 #include <crypto/sha256.h>
 #include <key.h>
 #include <logging.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <random.h>
 #include <util/string.h>
 #include <util/system.h>
diff --git a/src/interfaces/node.h b/src/interfaces/node.h
index 0b9abd07b7de1..9950762afd716 100644
--- a/src/interfaces/node.h
+++ b/src/interfaces/node.h
@@ -309,6 +309,10 @@ class Node
     using ShowProgressFn = std::function<void(const std::string& title, int progress, bool resume_possible)>;
     virtual std::unique_ptr<Handler> handleShowProgress(ShowProgressFn fn) = 0;
 
+    //! Register handler for wallet client constructed messages.
+    using InitWalletFn = std::function<void()>;
+    virtual std::unique_ptr<Handler> handleInitWallet(InitWalletFn fn) = 0;
+
     //! Register handler for number of connections changed messages.
     using NotifyNumConnectionsChangedFn = std::function<void(int new_num_connections)>;
     virtual std::unique_ptr<Handler> handleNotifyNumConnectionsChanged(NotifyNumConnectionsChangedFn fn) = 0;
diff --git a/src/llmq/chainlocks.cpp b/src/llmq/chainlocks.cpp
index 1ef7d22b91b31..1b6f56f5c8632 100644
--- a/src/llmq/chainlocks.cpp
+++ b/src/llmq/chainlocks.cpp
@@ -12,7 +12,7 @@
 #include <consensus/validation.h>
 #include <masternode/sync.h>
 #include <node/blockstorage.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <scheduler.h>
 #include <spork.h>
 #include <txmempool.h>
diff --git a/src/mapport.cpp b/src/mapport.cpp
index ecdbcdff12885..5a38353070a5b 100644
--- a/src/mapport.cpp
+++ b/src/mapport.cpp
@@ -18,7 +18,7 @@
 #include <util/thread.h>
 
 #ifdef USE_NATPMP
-#include <compat.h>
+#include <compat/compat.h>
 #include <natpmp.h>
 #endif // USE_NATPMP
 
diff --git a/src/masternode/sync.cpp b/src/masternode/sync.cpp
index dc8cc60f76f65..09d89d9f0ea2e 100644
--- a/src/masternode/sync.cpp
+++ b/src/masternode/sync.cpp
@@ -8,11 +8,11 @@
 #include <governance/governance.h>
 #include <netfulfilledman.h>
 #include <netmessagemaker.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <shutdown.h>
-#include <validation.h>
 #include <util/time.h>
 #include <util/translation.h>
+#include <validation.h>
 
 class CMasternodeSync;
 
diff --git a/src/net.cpp b/src/net.cpp
index db234f48761b1..9bfb8131782ce 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -15,7 +15,7 @@
 #include <addrman.h>
 #include <banman.h>
 #include <clientversion.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <consensus/consensus.h>
 #include <crypto/sha256.h>
 #include <node/eviction.h>
@@ -25,7 +25,7 @@
 #include <net_permissions.h>
 #include <netaddress.h>
 #include <netbase.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <protocol.h>
 #include <random.h>
 #include <scheduler.h>
diff --git a/src/net.h b/src/net.h
index 446e68704813c..524f0a244b43c 100644
--- a/src/net.h
+++ b/src/net.h
@@ -9,7 +9,7 @@
 #include <bip324.h>
 #include <chainparams.h>
 #include <common/bloom.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <consensus/amount.h>
 #include <fs.h>
 #include <crypto/siphash.h>
diff --git a/src/netaddress.h b/src/netaddress.h
index 102de00225a8e..4d53ed9694540 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -10,7 +10,7 @@
 #endif
 
 #include <attributes.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <crypto/siphash.h>
 #include <prevector.h>
 #include <random.h>
diff --git a/src/netbase.cpp b/src/netbase.cpp
index cf1ba19e654fb..adaf3fa629639 100644
--- a/src/netbase.cpp
+++ b/src/netbase.cpp
@@ -5,7 +5,7 @@
 
 #include <netbase.h>
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <sync.h>
 #include <tinyformat.h>
 #include <util/sock.h>
diff --git a/src/netbase.h b/src/netbase.h
index 9478555d59484..51233967b3e86 100644
--- a/src/netbase.h
+++ b/src/netbase.h
@@ -9,7 +9,7 @@
 #include <config/bitcoin-config.h>
 #endif
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <netaddress.h>
 #include <serialize.h>
 #include <util/sock.h>
diff --git a/src/node/ui_interface.cpp b/src/node/interface_ui.cpp
similarity index 95%
rename from src/node/ui_interface.cpp
rename to src/node/interface_ui.cpp
index b87ae85ee7dd9..b01d20bb3e41f 100644
--- a/src/node/ui_interface.cpp
+++ b/src/node/interface_ui.cpp
@@ -2,7 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 
 #include <util/translation.h>
 
@@ -15,6 +15,7 @@ struct UISignals {
     boost::signals2::signal<CClientUIInterface::ThreadSafeMessageBoxSig, boost::signals2::optional_last_value<bool>> ThreadSafeMessageBox;
     boost::signals2::signal<CClientUIInterface::ThreadSafeQuestionSig, boost::signals2::optional_last_value<bool>> ThreadSafeQuestion;
     boost::signals2::signal<CClientUIInterface::InitMessageSig> InitMessage;
+    boost::signals2::signal<CClientUIInterface::InitWalletSig> InitWallet;
     boost::signals2::signal<CClientUIInterface::NotifyNumConnectionsChangedSig> NotifyNumConnectionsChanged;
     boost::signals2::signal<CClientUIInterface::NotifyNetworkActiveChangedSig> NotifyNetworkActiveChanged;
     boost::signals2::signal<CClientUIInterface::NotifyAlertChangedSig> NotifyAlertChanged;
@@ -37,6 +38,7 @@ static UISignals g_ui_signals;
 ADD_SIGNALS_IMPL_WRAPPER(ThreadSafeMessageBox);
 ADD_SIGNALS_IMPL_WRAPPER(ThreadSafeQuestion);
 ADD_SIGNALS_IMPL_WRAPPER(InitMessage);
+ADD_SIGNALS_IMPL_WRAPPER(InitWallet);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyNumConnectionsChanged);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyNetworkActiveChanged);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyAlertChanged);
@@ -51,6 +53,7 @@ ADD_SIGNALS_IMPL_WRAPPER(BannedListChanged);
 bool CClientUIInterface::ThreadSafeMessageBox(const bilingual_str& message, const std::string& caption, unsigned int style) { return g_ui_signals.ThreadSafeMessageBox(message, caption, style).value_or(false);}
 bool CClientUIInterface::ThreadSafeQuestion(const bilingual_str& message, const std::string& non_interactive_message, const std::string& caption, unsigned int style) { return g_ui_signals.ThreadSafeQuestion(message, non_interactive_message, caption, style).value_or(false);}
 void CClientUIInterface::InitMessage(const std::string& message) { return g_ui_signals.InitMessage(message); }
+void CClientUIInterface::InitWallet() { return g_ui_signals.InitWallet(); }
 void CClientUIInterface::NotifyNumConnectionsChanged(int newNumConnections) { return g_ui_signals.NotifyNumConnectionsChanged(newNumConnections); }
 void CClientUIInterface::NotifyNetworkActiveChanged(bool networkActive) { return g_ui_signals.NotifyNetworkActiveChanged(networkActive); }
 void CClientUIInterface::NotifyAlertChanged() { return g_ui_signals.NotifyAlertChanged(); }
diff --git a/src/node/ui_interface.h b/src/node/interface_ui.h
similarity index 96%
rename from src/node/ui_interface.h
rename to src/node/interface_ui.h
index a3934341bec88..3f8b683de2e96 100644
--- a/src/node/ui_interface.h
+++ b/src/node/interface_ui.h
@@ -3,8 +3,8 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#ifndef BITCOIN_NODE_UI_INTERFACE_H
-#define BITCOIN_NODE_UI_INTERFACE_H
+#ifndef BITCOIN_NODE_INTERFACE_UI_H
+#define BITCOIN_NODE_INTERFACE_UI_H
 
 #include <functional>
 #include <memory>
@@ -83,6 +83,9 @@ class CClientUIInterface
     /** Progress message during initialization. */
     ADD_SIGNALS_DECL_WRAPPER(InitMessage, void, const std::string& message);
 
+    /** Wallet client created. */
+    ADD_SIGNALS_DECL_WRAPPER(InitWallet, void, );
+
     /** Number of network connections changed. */
     ADD_SIGNALS_DECL_WRAPPER(NotifyNumConnectionsChanged, void, int newNumConnections);
 
@@ -128,4 +131,4 @@ constexpr auto AbortError = InitError;
 
 extern CClientUIInterface uiInterface;
 
-#endif // BITCOIN_NODE_UI_INTERFACE_H
+#endif // BITCOIN_NODE_INTERFACE_UI_H
diff --git a/src/node/interfaces.cpp b/src/node/interfaces.cpp
index ea4bce94d6948..90a4c51d7e4c4 100644
--- a/src/node/interfaces.cpp
+++ b/src/node/interfaces.cpp
@@ -30,7 +30,7 @@
 #include <node/blockstorage.h>
 #include <node/coin.h>
 #include <node/context.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <node/transaction.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
@@ -527,6 +527,10 @@ class NodeImpl : public Node
     {
         return MakeHandler(::uiInterface.ShowProgress_connect(fn));
     }
+    std::unique_ptr<Handler> handleInitWallet(InitWalletFn fn) override
+    {
+        return MakeHandler(::uiInterface.InitWallet_connect(fn));
+    }
     std::unique_ptr<Handler> handleNotifyNumConnectionsChanged(NotifyNumConnectionsChangedFn fn) override
     {
         return MakeHandler(::uiInterface.NotifyNumConnectionsChanged_connect(fn));
diff --git a/src/noui.cpp b/src/noui.cpp
index 57bbe39c90a9b..11bfdbc80bed8 100644
--- a/src/noui.cpp
+++ b/src/noui.cpp
@@ -7,7 +7,7 @@
 #include <noui.h>
 
 #include <logging.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <util/translation.h>
 
 #include <string>
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index debab9e2a24f1..79a1db90026ca 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -16,7 +16,7 @@
 #include <interfaces/node.h>
 #include <net.h>
 #include <node/context.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <noui.h>
 #include <qt/bitcoingui.h>
 #include <qt/clientmodel.h>
@@ -262,7 +262,6 @@ void BitcoinApplication::createSplashScreen(const NetworkStyle *networkStyle)
     // We don't hold a direct pointer to the splash screen after creation, but the splash
     // screen will take care of deleting itself when finish() happens.
     m_splash->show();
-    connect(this, &BitcoinApplication::requestedInitialize, m_splash, &SplashScreen::handleLoadWallet);
     connect(this, &BitcoinApplication::splashFinished, m_splash, &SplashScreen::finish);
     connect(this, &BitcoinApplication::requestedShutdown, m_splash, &QWidget::close);
 }
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index 734360d53fecb..4e2d32b031c37 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -36,7 +36,7 @@
 #include <interfaces/coinjoin.h>
 #include <interfaces/handler.h>
 #include <interfaces/node.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <qt/governancelist.h>
 #include <qt/masternodelist.h>
 #include <util/system.h>
diff --git a/src/qt/guiutil.cpp b/src/qt/guiutil.cpp
index 84afe40bba44d..2574adee48212 100644
--- a/src/qt/guiutil.cpp
+++ b/src/qt/guiutil.cpp
@@ -29,9 +29,6 @@
 #include <cmath>
 
 #ifdef WIN32
-#ifndef NOMINMAX
-#define NOMINMAX
-#endif
 #include <shellapi.h>
 #include <shlobj.h>
 #include <shlwapi.h>
diff --git a/src/qt/main.cpp b/src/qt/main.cpp
index a1220b9a59b29..eca9e9d88f3ac 100644
--- a/src/qt/main.cpp
+++ b/src/qt/main.cpp
@@ -4,7 +4,7 @@
 
 #include <qt/bitcoin.h>
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <util/translation.h>
 #include <util/url.h>
 
diff --git a/src/qt/paymentserver.cpp b/src/qt/paymentserver.cpp
index 72553e81bb634..2eb28aca35c05 100644
--- a/src/qt/paymentserver.cpp
+++ b/src/qt/paymentserver.cpp
@@ -17,7 +17,7 @@
 #include <clientversion.h>
 #include <interfaces/node.h>
 #include <key_io.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <policy/policy.h>
 #include <util/system.h>
 
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index 1319d1d83684d..5012e9342c461 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -21,7 +21,7 @@
 #include <chainparams.h>
 #include <interfaces/node.h>
 #include <key_io.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <policy/fees.h>
 #include <txmempool.h>
 #include <wallet/coincontrol.h>
diff --git a/src/qt/splashscreen.cpp b/src/qt/splashscreen.cpp
index 005c3bcdb4d1a..56bb8c2f8956f 100644
--- a/src/qt/splashscreen.cpp
+++ b/src/qt/splashscreen.cpp
@@ -199,6 +199,7 @@ void SplashScreen::subscribeToCoreSignals()
     // Connect signals to client
     m_handler_init_message = m_node->handleInitMessage(std::bind(InitMessage, this, std::placeholders::_1));
     m_handler_show_progress = m_node->handleShowProgress(std::bind(ShowProgress, this, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
+    m_handler_init_wallet = m_node->handleInitWallet([this]() { handleLoadWallet(); });
 }
 
 void SplashScreen::handleLoadWallet()
diff --git a/src/qt/splashscreen.h b/src/qt/splashscreen.h
index bcb5f99b361f5..7c38490793047 100644
--- a/src/qt/splashscreen.h
+++ b/src/qt/splashscreen.h
@@ -66,6 +66,7 @@ public Q_SLOTS:
     bool m_shutdown = false;
     std::unique_ptr<interfaces::Handler> m_handler_init_message;
     std::unique_ptr<interfaces::Handler> m_handler_show_progress;
+    std::unique_ptr<interfaces::Handler> m_handler_init_wallet;
     std::unique_ptr<interfaces::Handler> m_handler_load_wallet;
     std::list<std::unique_ptr<interfaces::Wallet>> m_connected_wallets;
     std::list<std::unique_ptr<interfaces::Handler>> m_connected_wallet_handlers;
diff --git a/src/qt/transactionview.cpp b/src/qt/transactionview.cpp
index 55760147c5b20..8102c53de6a37 100644
--- a/src/qt/transactionview.cpp
+++ b/src/qt/transactionview.cpp
@@ -18,7 +18,7 @@
 #include <qt/walletmodel.h>
 
 #include <interfaces/node.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 
 #include <optional>
 
diff --git a/src/qt/walletframe.cpp b/src/qt/walletframe.cpp
index d97b1d7553120..9e177c673e305 100644
--- a/src/qt/walletframe.cpp
+++ b/src/qt/walletframe.cpp
@@ -5,7 +5,7 @@
 #include <qt/walletframe.h>
 
 #include <fs.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <psbt.h>
 #include <qt/governancelist.h>
 #include <qt/guiutil.h>
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index f0ed7ef0febe1..d4a88de83b97a 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -22,7 +22,7 @@
 #include <interfaces/handler.h>
 #include <interfaces/node.h>
 #include <key_io.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <psbt.h>
 #include <util/system.h> // for GetBoolArg
 #include <util/translation.h>
diff --git a/src/qt/walletview.cpp b/src/qt/walletview.cpp
index 1a994366606f5..390df73576c18 100644
--- a/src/qt/walletview.cpp
+++ b/src/qt/walletview.cpp
@@ -22,7 +22,7 @@
 #include <qt/walletmodel.h>
 
 #include <interfaces/node.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <util/strencodings.h>
 
 #include <QAction>
diff --git a/src/random.cpp b/src/random.cpp
index 7d3b20bd65c8b..e98b068d3cee0 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -9,24 +9,23 @@
 #include <crypto/chacha20.h>
 #include <crypto/sha256.h>
 #include <crypto/sha512.h>
-#include <support/cleanse.h>
-#ifdef WIN32
-#include <compat.h> // for Windows API
-#include <wincrypt.h>
-#endif
 #include <logging.h>
 #include <randomenv.h>
-#include <support/allocators/secure.h>
 #include <span.h>
-#include <sync.h>     // for Mutex
-#include <util/time.h> // for GetTimeMicros()
+#include <support/allocators/secure.h>
+#include <support/cleanse.h>
+#include <sync.h>
+#include <util/time.h>
 
 #include <array>
 #include <cmath>
 #include <stdlib.h>
 #include <thread>
 
-#ifndef WIN32
+#ifdef WIN32
+#include <windows.h>
+#include <wincrypt.h>
+#else
 #include <fcntl.h>
 #endif
 
@@ -729,7 +728,7 @@ bool Random_SanityCheck()
      * GetOSRand() overwrites all 32 bytes of the output given a maximum
      * number of tries.
      */
-    static const ssize_t MAX_TRIES = 1024;
+    static constexpr int MAX_TRIES{1024};
     uint8_t data[NUM_OS_RANDOM_BYTES];
     bool overwritten[NUM_OS_RANDOM_BYTES] = {}; /* Tracks which bytes have been overwritten at least once */
     int num_overwritten;
diff --git a/src/randomenv.cpp b/src/randomenv.cpp
index 06ac6d8f933b7..4cfe94acace05 100644
--- a/src/randomenv.cpp
+++ b/src/randomenv.cpp
@@ -14,22 +14,23 @@
 #include <crypto/sha512.h>
 #include <span.h>
 #include <support/cleanse.h>
-#include <util/time.h> // for GetTime()
-#ifdef WIN32
-#include <compat.h> // for Windows API
-#endif
+#include <util/time.h>
 
 #include <algorithm>
 #include <atomic>
+#include <cstdint>
+#include <cstring>
 #include <chrono>
 #include <climits>
 #include <thread>
 #include <vector>
 
-#include <stdint.h>
-#include <string.h>
-#ifndef WIN32
 #include <sys/types.h> // must go before a number of other headers
+
+#ifdef WIN32
+#include <windows.h>
+#include <winreg.h>
+#else
 #include <fcntl.h>
 #include <netinet/in.h>
 #include <sys/resource.h>
diff --git a/src/shutdown.cpp b/src/shutdown.cpp
index f500fa529eaf2..fe88b3aa46759 100644
--- a/src/shutdown.cpp
+++ b/src/shutdown.cpp
@@ -12,7 +12,7 @@
 #include <logging.h>
 #include <util/tokenpipe.h>
 
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <warnings.h>
 
 #include <assert.h>
diff --git a/src/stats/rawsender.h b/src/stats/rawsender.h
index d91f6c0def751..fc0b0d6795662 100644
--- a/src/stats/rawsender.h
+++ b/src/stats/rawsender.h
@@ -6,7 +6,7 @@
 #ifndef BITCOIN_STATS_RAWSENDER_H
 #define BITCOIN_STATS_RAWSENDER_H
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <sync.h>
 #include <threadinterrupt.h>
 
diff --git a/src/support/lockedpool.cpp b/src/support/lockedpool.cpp
index 14ad4782d7446..766e817a8ab54 100644
--- a/src/support/lockedpool.cpp
+++ b/src/support/lockedpool.cpp
@@ -10,9 +10,6 @@
 #endif
 
 #ifdef WIN32
-#ifndef NOMINMAX
-#define NOMINMAX
-#endif
 #include <windows.h>
 #else
 #include <sys/mman.h> // for mmap
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index 43864a5453e8e..ebf741651b516 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -9,7 +9,7 @@
 #include <attributes.h>
 #include <chainparamsbase.h>
 #include <coins.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <consensus/amount.h>
 #include <consensus/consensus.h>
 #include <key.h>
diff --git a/src/test/fuzz/util/net.cpp b/src/test/fuzz/util/net.cpp
index a1494f8d3bdcd..f8e996cfa574f 100644
--- a/src/test/fuzz/util/net.cpp
+++ b/src/test/fuzz/util/net.cpp
@@ -2,7 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <netaddress.h>
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <util/strencodings.h>
diff --git a/src/test/net_peer_connection_tests.cpp b/src/test/net_peer_connection_tests.cpp
index 2a09791daf166..c232baa93de85 100644
--- a/src/test/net_peer_connection_tests.cpp
+++ b/src/test/net_peer_connection_tests.cpp
@@ -3,7 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chainparams.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <net.h>
 #include <net_processing.h>
 #include <netaddress.h>
diff --git a/src/test/net_tests.cpp b/src/test/net_tests.cpp
index 02a958185fef0..1ff098cd1f9e6 100644
--- a/src/test/net_tests.cpp
+++ b/src/test/net_tests.cpp
@@ -6,7 +6,7 @@
 
 #include <chainparams.h>
 #include <clientversion.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <net.h>
 #include <net_processing.h>
 #include <netaddress.h>
diff --git a/src/test/sock_tests.cpp b/src/test/sock_tests.cpp
index 9e98f4f0b1783..fa95fc0ba55ea 100644
--- a/src/test/sock_tests.cpp
+++ b/src/test/sock_tests.cpp
@@ -2,7 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <test/util/setup_common.h>
 #include <threadinterrupt.h>
 #include <util/sock.h>
diff --git a/src/test/util/net.h b/src/test/util/net.h
index 4c2be00e49dba..7ca37616e5acd 100644
--- a/src/test/util/net.h
+++ b/src/test/util/net.h
@@ -5,7 +5,7 @@
 #ifndef BITCOIN_TEST_UTIL_NET_H
 #define BITCOIN_TEST_UTIL_NET_H
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <net.h>
 #include <net_permissions.h>
 #include <net_processing.h>
diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
index 1a53f5cb1637a..fbdb851ae19d8 100644
--- a/src/test/util_tests.cpp
+++ b/src/test/util_tests.cpp
@@ -37,9 +37,11 @@
 #include <unordered_set>
 #include <utility>
 #include <vector>
+
+#include <sys/types.h>
+
 #ifndef WIN32
 #include <signal.h>
-#include <sys/types.h>
 #include <sys/wait.h>
 #endif
 
diff --git a/src/timedata.cpp b/src/timedata.cpp
index a0b8c33e7abb0..54378a5cf1b5a 100644
--- a/src/timedata.cpp
+++ b/src/timedata.cpp
@@ -9,7 +9,7 @@
 #include <timedata.h>
 
 #include <netaddress.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <sync.h>
 #include <tinyformat.h>
 #include <util/system.h>
diff --git a/src/torcontrol.cpp b/src/torcontrol.cpp
index 26154a9939891..a89099ecfd099 100644
--- a/src/torcontrol.cpp
+++ b/src/torcontrol.cpp
@@ -7,7 +7,7 @@
 
 #include <chainparams.h>
 #include <chainparamsbase.h>
-#include <compat.h>
+#include <compat/compat.h>
 #include <crypto/hmac_sha256.h>
 #include <net.h>
 #include <netaddress.h>
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 23e2480c4c5d6..f780b56b44088 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -6,7 +6,7 @@
 #include <txdb.h>
 
 #include <chain.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <pow.h>
 #include <random.h>
 #include <shutdown.h>
diff --git a/src/util/edge.h b/src/util/edge.h
index 8e3ec357a1f7d..7ac354c8bf801 100644
--- a/src/util/edge.h
+++ b/src/util/edge.h
@@ -5,7 +5,7 @@
 #ifndef BITCOIN_UTIL_EDGE_H
 #define BITCOIN_UTIL_EDGE_H
 
-#include <compat.h>
+#include <compat/compat.h>
 
 #include <assert.h>
 #include <cstdint>
diff --git a/src/util/sock.cpp b/src/util/sock.cpp
index 1d12669652d69..87e63b70c38ad 100644
--- a/src/util/sock.cpp
+++ b/src/util/sock.cpp
@@ -2,7 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <logging.h>
 #include <threadinterrupt.h>
 #include <tinyformat.h>
diff --git a/src/util/sock.h b/src/util/sock.h
index 4c18e71e0cf0e..4d32d50e5e733 100644
--- a/src/util/sock.h
+++ b/src/util/sock.h
@@ -5,7 +5,7 @@
 #ifndef BITCOIN_UTIL_SOCK_H
 #define BITCOIN_UTIL_SOCK_H
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <threadinterrupt.h>
 #include <util/time.h>
 
diff --git a/src/util/system.cpp b/src/util/system.cpp
index 84d633db09e5d..563a7bf4b0bf3 100644
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -60,9 +60,6 @@
 #pragma warning(disable:4717)
 #endif
 
-#ifndef NOMINMAX
-#define NOMINMAX
-#endif
 #include <codecvt>
 
 #include <io.h> /* for _commit */
diff --git a/src/util/system.h b/src/util/system.h
index 5779beb065ed0..2983107c228d6 100644
--- a/src/util/system.h
+++ b/src/util/system.h
@@ -16,8 +16,8 @@
 #endif
 
 #include <attributes.h>
-#include <compat.h>
 #include <compat/assumptions.h>
+#include <compat/compat.h>
 #include <consensus/amount.h>
 #include <fs.h>
 #include <logging.h>
diff --git a/src/util/time.cpp b/src/util/time.cpp
index 2b9a469d9a9db..80f689132859e 100644
--- a/src/util/time.cpp
+++ b/src/util/time.cpp
@@ -7,7 +7,7 @@
 #include <config/bitcoin-config.h>
 #endif
 
-#include <compat.h>
+#include <compat/compat.h>
 #include <util/time.h>
 
 #include <util/check.h>
diff --git a/src/util/time.h b/src/util/time.h
index 306a1ae3f2911..32bdebb205066 100644
--- a/src/util/time.h
+++ b/src/util/time.h
@@ -6,7 +6,7 @@
 #ifndef BITCOIN_UTIL_TIME_H
 #define BITCOIN_UTIL_TIME_H
 
-#include <compat.h>
+#include <compat/compat.h>
 
 #include <chrono>
 #include <stdint.h>
diff --git a/src/validation.cpp b/src/validation.cpp
index 5f093aa1b2fe6..d1681a265baaa 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -24,7 +24,7 @@
 #include <logging/timer.h>
 #include <node/blockstorage.h>
 #include <node/coinstats.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <node/utxo_snapshot.h>
 #include <policy/policy.h>
 #include <policy/settings.h>
diff --git a/src/wallet/bdb.cpp b/src/wallet/bdb.cpp
index 1509f9c17721f..ef6947a25f949 100644
--- a/src/wallet/bdb.cpp
+++ b/src/wallet/bdb.cpp
@@ -3,6 +3,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <compat/compat.h>
 #include <fs.h>
 #include <wallet/bdb.h>
 #include <wallet/db.h>
@@ -12,8 +13,15 @@
 
 #include <stdint.h>
 
-#ifndef WIN32
 #include <sys/stat.h>
+
+// Windows may not define S_IRUSR or S_IWUSR. We define both
+// here, with the same values as glibc (see stat.h).
+#ifdef WIN32
+#ifndef S_IRUSR
+#define S_IRUSR             0400
+#define S_IWUSR             0200
+#endif
 #endif
 
 namespace {
diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index 15b3306f82e13..8f7a416939261 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -9,7 +9,7 @@
 #include <interfaces/wallet.h>
 #include <net.h>
 #include <node/context.h>
-#include <node/ui_interface.h>
+#include <node/interface_ui.h>
 #include <univalue.h>
 #include <util/check.h>
 #include <util/error.h>
diff --git a/test/functional/test_framework/authproxy.py b/test/functional/test_framework/authproxy.py
index da9f6f2979477..5673f478265ae 100644
--- a/test/functional/test_framework/authproxy.py
+++ b/test/functional/test_framework/authproxy.py
@@ -39,7 +39,6 @@
 import http.client
 import json
 import logging
-import os
 import socket
 import time
 import urllib.parse
@@ -101,11 +100,6 @@ def _request(self, method, path, postdata):
                    'User-Agent': USER_AGENT,
                    'Authorization': self.__auth_header,
                    'Content-type': 'application/json'}
-        if os.name == 'nt':
-            # Windows somehow does not like to re-use connections
-            # TODO: Find out why the connection would disconnect occasionally and make it reusable on Windows
-            # Avoid "ConnectionAbortedError: [WinError 10053] An established connection was aborted by the software in your host machine"
-            self._set_conn()
         try:
             self.__conn.request(method, path, postdata, headers)
             return self._get_response()
@@ -116,10 +110,8 @@ def _request(self, method, path, postdata):
             self.__conn.request(method, path, postdata, headers)
             return self._get_response()
         except OSError as e:
-            retry = (
-                '[WinError 10053] An established connection was aborted by the software in your host machine' in str(e))
             # Workaround for a bug on macOS. See https://bugs.python.org/issue33450
-            retry = retry or ('[Errno 41] Protocol wrong type for socket' in str(e))
+            retry = '[Errno 41] Protocol wrong type for socket' in str(e)
             if retry:
                 self.__conn.close()
                 self.__conn.request(method, path, postdata, headers)