diff --git a/.github/workflows/ci-scripts-build.yml b/.github/workflows/ci-scripts-build.yml
index 070f6f2..beefedb 100644
--- a/.github/workflows/ci-scripts-build.yml
+++ b/.github/workflows/ci-scripts-build.yml
@@ -177,9 +177,10 @@ jobs:
       if: ${{ always() && runner.os == 'macOS' }}
       run: otool -D -L -l bundle/usr/*/lib/*.dylib lib/*/*.dylib bin/*/pvxinfo
     - name: readelf
-      if: ${{ always() && runner.os == 'Linux' }}
+      if: ${{ always() && runner.os == 'Linux' && matrix.base != '3.14' }}
       run: find bundle/usr lib -name '*.so' -print0 | xargs -0 readelf -d bin/linux-*/pvxinfo
     - name: Host info
+      if: ${{ matrix.base != '3.14' }}
       run: python .ci/cue.py --add-path "{TOP}/bin/{EPICS_HOST_ARCH}" --add-path "{TOP}/bundle/usr/{EPICS_HOST_ARCH}/lib" exec pvxinfo -D
     - name: Test env setup
       run: echo "UBSAN_OPTIONS=log_path=$PWD/UBSAN:suppressions=$PWD/.ci-local/ubsan.supp:report_error_type=1:print_stacktrace=1" >> $GITHUB_ENV
diff --git a/tools/Makefile b/tools/Makefile
index 18785fc..9c885d2 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -5,6 +5,8 @@ include $(TOP)/configure/CONFIG
 #  ADD MACRO DEFINITIONS AFTER THIS LINE
 #=============================
 
+ifdef BASE_3_15
+
 # access to private headers
 USR_CPPFLAGS += -I$(TOP)/src
 
@@ -34,6 +36,8 @@ pvxlist_SRCS += list.cpp
 PROD += pvxmshim
 pvxmshim_SRCS += mshim.cpp
 
+endif # BASE_3_15
+
 #===========================
 
 include $(TOP)/configure/RULES
diff --git a/tools/put.cpp b/tools/put.cpp
index a57b453..8685c54 100644
--- a/tools/put.cpp
+++ b/tools/put.cpp
@@ -12,8 +12,11 @@
 #include <epicsGetopt.h>
 #include <epicsThread.h>
 
+#define PVXS_ENABLE_EXPERT_API
+
 #include <pvxs/client.h>
 #include <pvxs/log.h>
+#include <pvxs/json.h>
 #include "utilpvt.h"
 #include "evhelper.h"
 
@@ -85,9 +88,10 @@ int main(int argc, char *argv[])
 
         if(argc-optind==1 && std::string(argv[optind]).find_first_of('=')==std::string::npos) {
             // only one field assignment, and field name omitted.
-            // implies .value
+            // if JSON map, treat as entire struct.  Others imply .value
 
-            values["value"] = argv[optind];
+            auto sval(argv[optind]);
+            values[sval[0]=='{' ? "" : "value"] = sval;
 
         } else {
             for(auto n : range(optind, argc)) {
@@ -120,9 +124,18 @@ int main(int argc, char *argv[])
                     val.unmark(false, true);
                     for(auto& pair : values) {
                         try{
-                            val[pair.first] = pair.second;
-                        }catch(NoConvert& e){
-                            throw std::runtime_error(SB()<<"Unable to assign "<<pair.first<<" from \""<<escape(pair.second)<<"\"");
+                            auto fld(val);
+                            if(!pair.first.empty())
+                                fld = val.lookup(pair.first);
+                            auto& sv(pair.second);
+                            if(!sv.empty() && (sv[0]=='{' || sv[0]=='[' || sv[0]=='"'))
+                                json::Parse(pair.second).into(fld);
+                            else
+                                fld.from(sv);
+                        }catch(std::exception& e){
+                            throw std::runtime_error(SB()<<"Unable to assign "<<pair.first
+                                                     <<" from \""<<escape(pair.second)<<"\""
+                                                     <<" : "<<e.what());
                         }
                     }
                     if(verbose) {