diff --git a/src/Control/Inciter/CmdLine/CmdLine.hpp b/src/Control/Inciter/CmdLine/CmdLine.hpp
index 0c0ef976e1e..b2f804cc6c3 100644
--- a/src/Control/Inciter/CmdLine/CmdLine.hpp
+++ b/src/Control/Inciter/CmdLine/CmdLine.hpp
@@ -169,7 +169,29 @@ class CmdLine : public tk::TaggedTuple< CmdLineMembers > {
     ///@{
     //! \brief Pack/Unpack serialize member function
     //! \param[in,out] p Charm++'s PUP::er serializer object reference
-    void pup( PUP::er& p ) { tk::TaggedTuple< CmdLineMembers >::pup(p); }
+    //! \details cmdinfo, ctrinfo, and helpkw are intentionally skipped: they
+    //!   are always reconstructed identically by the constructors from
+    //!   compile-time string literals and must not be checkpointed, as their
+    //!   large size (MB of help text) can corrupt the PUP stream offset.
+    void pup( PUP::er& p ) {
+      p | get< tag::io >();
+      p | get< tag::virtualization >();
+      p | get< tag::verbose >();
+      p | get< tag::chare >();
+      p | get< tag::nonblocking >();
+      p | get< tag::benchmark >();
+      p | get< tag::feedback >();
+      p | get< tag::help >();
+      p | get< tag::helpctr >();
+      p | get< tag::quiescence >();
+      p | get< tag::trace >();
+      p | get< tag::version >();
+      p | get< tag::license >();
+      p | get< tag::error >();
+      p | get< tag::lbfreq >();
+      p | get< tag::rsfreq >();
+      // tag::cmdinfo, tag::ctrinfo, tag::helpkw intentionally not PUP'd
+    }
     //! \brief Pack/Unpack serialize operator|
     //! \param[in,out] p Charm++'s PUP::er serializer object reference
     //! \param[in,out] c CmdLine object reference
diff --git a/src/Inciter/Discretization.cpp b/src/Inciter/Discretization.cpp
index e6304c7b80c..f8017598071 100644
--- a/src/Inciter/Discretization.cpp
+++ b/src/Inciter/Discretization.cpp
@@ -35,6 +35,12 @@ extern ctr::InputDeck g_inputdeck_defaults;
 
 } // inciter::
 
+namespace exam2m {
+
+extern CollideHandle collideHandle;
+
+} // exam2m::
+
 using inciter::Discretization;
 
 Discretization::Discretization(
@@ -175,13 +181,50 @@ Discretization::Discretization(
     if (thisIndex == 0) {
       exam2m::addMesh( thisProxy, m_nchare,
         CkCallback( CkIndex_Discretization::transferInit(), thisProxy ) );
-      //std::cout << "Disc: " << m_meshid << " m2m::addMesh()\n";
+      std::cout << "Disc: " << m_meshid << " called addMesh(). \n";
     }
   }
+}
+
+void
+Discretization::addRestartedMesh( CkCallback cb )
+// *****************************************************************************
+// Register mesh with mesh-transfer lib on restart
+//! \param[in] cb Callback to call when mesh-registration is complete.
+// *****************************************************************************
+{
+  if (m_disc.size() == 1 || m_transfer.empty()) {
+    // skip transfer if single mesh or if not involved in coupling
+    cb.send();
+  } else {
+    // Store the callback so collideRestartDone() (element 0) can forward it
+    // to addMesh once all PEs have finished reinitClient.
+    m_restartcb = cb;
+    // Reinitialize the collision client on this PE's collideMgr branch.
+    // Contribute to a barrier so ALL PEs finish reinitClient before element 0
+    // calls addMesh.  Without this, collideMgr on some PEs may not yet be
+    // restored from checkpoint when the first collision messages arrive,
+    // causing "group proxy not initialized" (CmiAbort / SIGSEGV on restart).
+    CollideSerialClientRestart(exam2m::collideHandle, exam2m::collisionHandler,
+      0);
+    contribute( CkCallback(CkIndex_Discretization::collideRestartDone(), thisProxy) );
+  }
   // Array elements must not use the chare_objs table
   chareIdx = -1;
 }
 
+void
+Discretization::collideRestartDone()
+// *****************************************************************************
+// Called on element 0 once every chare has finished CollideSerialClientRestart
+// *****************************************************************************
+{
+  if (thisIndex == 0) {
+    std::cout << "Disc: on restart " << m_meshid << " called addMesh(). \n";
+    exam2m::addMesh( thisProxy, m_nchare, m_restartcb );
+  }
+}
+
 std::unordered_map< std::size_t, std::size_t >
 Discretization::genBid()
 // *****************************************************************************
@@ -204,6 +247,7 @@ Discretization::transferInit()
 // coupled to other solver)
 // *****************************************************************************
 {
+  std::cout << "Disc: " << m_meshid << " completed addMesh(). \n";
   // Compute number of mesh points owned
   std::size_t npoin = m_gid.size();
   for (auto g : m_gid) if (tk::slave(m_nodeCommMap,g,thisIndex)) --npoin;
@@ -345,6 +389,7 @@ Discretization::transfer(
     // Pass source and destination meshes to mesh transfer lib (if coupled)
     Assert( m_nsrc < m_mytransfer.size(), "Indexing out of mytransfer[src]" );
     if (fromMesh == m_meshid) {
+      std::cout << "Disc: " << m_meshid << " setting source tets. \n";
       exam2m::setSourceTets( thisProxy, thisIndex, &m_inpoel, &m_coord, u );
       ++m_nsrc;
     } else {
@@ -352,6 +397,7 @@ Discretization::transfer(
     }
     Assert( m_ndst < m_mytransfer.size(), "Indexing out of mytransfer[dst]" );
     if (toMesh == m_meshid) {
+      std::cout << "Disc: " << m_meshid << " setting destination pts. \n";
       exam2m::setDestPoints( thisProxy, thisIndex, &m_coord, u,
         cb_xfer );
       ++m_ndst;
diff --git a/src/Inciter/Discretization.hpp b/src/Inciter/Discretization.hpp
index 1bdf472f8db..c965022dfc0 100644
--- a/src/Inciter/Discretization.hpp
+++ b/src/Inciter/Discretization.hpp
@@ -93,6 +93,12 @@ class Discretization : public CBase_Discretization {
     //! Configure Charm++ reduction types
     static void registerReducers();
 
+    //! Register mesh with mesh-transfer lib
+    void addRestartedMesh( CkCallback cb );
+
+    //! Barrier target: all PEs done with CollideSerialClientRestart
+    void collideRestartDone();
+
     //! Start computing new mesh veloctity for ALE mesh motion
     void meshvelStart(
       const tk::UnsMesh::Coords vel,
@@ -514,6 +520,8 @@ class Discretization : public CBase_Discretization {
     //! \brief Charm++ callback of the function to call after a mesh-to-mesh
     //!   solution transfer (to-and-fro) is complete
     CkCallback m_transfer_complete;
+    //! Callback stored during addRestartedMesh, forwarded by collideRestartDone
+    CkCallback m_restartcb;
     //! Solution/mesh transfer (coupling) information coordination propagation
     //! \details This has the same size with the same src/dst information on
     //!   all solvers.
diff --git a/src/Inciter/OversetFE.cpp b/src/Inciter/OversetFE.cpp
index 3d652f37d86..713860fb686 100644
--- a/src/Inciter/OversetFE.cpp
+++ b/src/Inciter/OversetFE.cpp
@@ -667,6 +667,9 @@ OversetFE::transferSol()
 // Transfer solution to other solver and mesh if coupled
 // *****************************************************************************
 {
+  std::cout << "Overset " << Disc()->MeshId()
+    << " in transferSol(), m_ixfer: " << m_ixfer << "\n";
+
   // Set up transfer-flags for receiving mesh
   if (m_ixfer == 1) {
     applySolTransfer(0);
@@ -674,6 +677,9 @@ OversetFE::transferSol()
   setTransferFlags(m_ixfer);
   ++m_ixfer;
 
+  std::cout << "Overset " << Disc()->MeshId()
+    << " transferflags set, m_ixfer: " << m_ixfer << "\n";
+
   // Initiate IC transfer (if coupled)
   Disc()->transfer( m_uc, m_ixfer-1,
     CkCallback(CkIndex_OversetFE::lhs(), thisProxy[thisIndex]) );
@@ -1677,7 +1683,7 @@ OversetFE::out()
 void
 OversetFE::evalLB( int nrestart )
 // *****************************************************************************
-// Evaluate whether to do load balancing
+// Begins to evaluate whether to do load balancing, but actually just adds mesh
 //! \param[in] nrestart Number of times restarted
 // *****************************************************************************
 {
@@ -1685,7 +1691,23 @@ OversetFE::evalLB( int nrestart )
 
   // Detect if just returned from a checkpoint and if so, zero timers and
   // finished flag
-  if (d->restarted( nrestart )) m_finished = 0;
+  if (d->restarted( nrestart )) {
+    d->addRestartedMesh(
+      CkCallback(CkIndex_OversetFE::continueEvalLB(), thisProxy) );
+    m_finished = 0;
+  }
+  else
+    continueEvalLB();
+}
+
+void
+OversetFE::continueEvalLB()
+// *****************************************************************************
+// Continue evaluating whether to do load balancing and proceed to next step
+// *****************************************************************************
+{
+  auto d = Disc();
+  std::cout << "Overset " << d->MeshId() << " in continueEvalLB. \n";
 
   const auto lbfreq = g_inputdeck.get< tag::cmd, tag::lbfreq >();
   const auto nonblocking = g_inputdeck.get< tag::cmd, tag::nonblocking >();
diff --git a/src/Inciter/OversetFE.hpp b/src/Inciter/OversetFE.hpp
index 6e0f1bc6cb2..f915590d2bc 100644
--- a/src/Inciter/OversetFE.hpp
+++ b/src/Inciter/OversetFE.hpp
@@ -157,6 +157,9 @@ class OversetFE : public CBase_OversetFE {
     // Evaluate whether to do load balancing
     void evalLB( int nrestart );
 
+    // Continue evaluating whether to do load balancing and proceed to next step
+    void continueEvalLB();
+
     //! Evaluate whether to continue with next time step stage
     void stage();
 
diff --git a/src/Inciter/discretization.ci b/src/Inciter/discretization.ci
index 755f4f7b0d7..e85c7aa8ed9 100644
--- a/src/Inciter/discretization.ci
+++ b/src/Inciter/discretization.ci
@@ -47,6 +47,7 @@ module discretization {
                          const std::vector< tk::real >& nodevol );
       entry void stat( tk::real mesh_volume );
       entry void transferInit();
+      entry void collideRestartDone();
       entry void transfer_complete();
       entry void to_complete();
       entry void from_complete();
diff --git a/src/Inciter/oversetfe.ci b/src/Inciter/oversetfe.ci
index 935a7226594..4ca7778f7ee 100644
--- a/src/Inciter/oversetfe.ci
+++ b/src/Inciter/oversetfe.ci
@@ -62,6 +62,7 @@ module oversetfe {
       entry void next();
       entry void stage();
       entry void evalLB( int nrestart );
+      entry void continueEvalLB();
       //! [Entry methods]
 
       // SDAG code follows. See http://charm.cs.illinois.edu/manuals/html/
diff --git a/src/Transfer/M2MTransfer.cpp b/src/Transfer/M2MTransfer.cpp
index c73e69c72e2..20e1fbe3414 100644
--- a/src/Transfer/M2MTransfer.cpp
+++ b/src/Transfer/M2MTransfer.cpp
@@ -4,6 +4,7 @@
 #include "TransferDetails.hpp"
 
 #include <cassert>
+#include <iostream>
 
 namespace exam2m {
 
@@ -49,6 +50,7 @@ void setDestPoints(CkArrayID p, int index, tk::UnsMesh::Coords* coords, tk::Fiel
 }
 
 LibMain::LibMain(CkArgMsg* msg) {
+  std::cout << "LibMain() called..." << std::endl;
   delete msg;
   m2mtransferProxy = CProxy_M2MTransfer::ckNew();
 
@@ -56,11 +58,22 @@ LibMain::LibMain(CkArgMsg* msg) {
   CollideGrid3d gridMap(CkVector3d(0, 0, 0),CkVector3d(2, 100, 2));
   collideHandle = CollideCreate(gridMap,
       CollideSerialClient(collisionHandler, 0));
+  std::cout << "LibMain() cmplt." << std::endl;
 }
 
+
 M2MTransfer::M2MTransfer() : current_chunk(0) {}
 
-void M2MTransfer::addMesh(CkArrayID p, int elem, CkCallback cb) {
+void M2MTransfer::addMesh(CkArrayID p, int elem, CkCallback cb)
+// *****************************************************************************
+//  Register mesh with the mesh-to-mesh transfer library
+//! \param[in] p Proxy from which this function call originated
+//! \param[in] elem Total number of chares in the application
+//! \param[in] cb Callback to inform application that the library is ready
+//! \details This function registers a mesh with M2MTransfer. This needs to
+//!   be called during normal execution and when restarting from checkpoint.
+// *****************************************************************************
+{
   auto id = static_cast<std::size_t>(CkGroupID(p).idx);
   if (proxyMap.count(id) == 0) {
     CkArrayOptions opts;
@@ -72,6 +85,7 @@ void M2MTransfer::addMesh(CkArrayID p, int elem, CkCallback cb) {
     mesh.m_proxy = CProxy_TransferDetails::ckNew(p, mesh, cb, opts);
     proxyMap[id] = mesh;
     current_chunk += elem;
+    std::cout << "M2MTransfer::addMesh() cmplt. " << thisIndex << std::endl;
   } else {
     CkAbort("Uhoh...\n");
   }
diff --git a/src/Transfer/M2MTransfer.hpp b/src/Transfer/M2MTransfer.hpp
index 29397447970..a1aa26d3f94 100644
--- a/src/Transfer/M2MTransfer.hpp
+++ b/src/Transfer/M2MTransfer.hpp
@@ -1,21 +1,36 @@
 // Controller for the library
+#ifndef M2MTransfer_hpp
+#define M2MTransfer_hpp
 
 #include "NoWarning/m2mtransfer.decl.h"
 
 #include "collidecharm.h"
 #include "Fields.hpp"
 
+#include <iostream>
+
 namespace exam2m {
 
+//! External user interface functions to M2MTransfer
+void collisionHandler( [[maybe_unused]] void *param,
+                        int nColl,
+                        Collision *colls );
 void addMesh(CkArrayID p, int elem, CkCallback cb);
 void setSourceTets(CkArrayID p, int index, std::vector< std::size_t >* inpoel, tk::UnsMesh::Coords* coords, const tk::Fields& u);
 void setDestPoints(CkArrayID p, int index, tk::UnsMesh::Coords* coords, tk::Fields& u, CkCallback cb);
 
+//! LibMain mainchare that creates collidecharm-proxies at startup
 class LibMain : public CBase_LibMain {
 public:
   LibMain(CkArgMsg* msg);
+  explicit LibMain(CkMigrateMessage* msg) : CBase_LibMain(msg) {
+    std::cout << "LibMain() migrate ctor cmplt." << std::endl;
+  }
+  void pup(PUP::er&) {}
+  friend void operator|( PUP::er& p, LibMain& m ) { m.pup(p); }
 };
 
+//! MeshData class that contains the mesh
 class MeshData {
   public:
     CProxy_TransferDetails m_proxy;
@@ -28,6 +43,7 @@ class MeshData {
     }
 };
 
+//! M2MTransfer chare-group which is inciter's interface to collidecharm
 class M2MTransfer : public CBase_M2MTransfer {
   private:
     std::unordered_map<CmiUInt8, MeshData> proxyMap;
@@ -35,22 +51,36 @@ class M2MTransfer : public CBase_M2MTransfer {
     CmiUInt8 m_sourcemesh, m_destmesh;
 
   public:
+
+    //! Constructor
     M2MTransfer();
+
     #if defined(__clang__)
       #pragma clang diagnostic push
       #pragma clang diagnostic ignored "-Wundefined-func-template"
     #endif
+    //! Migrate constructor
     explicit M2MTransfer( CkMigrateMessage* m ) : CBase_M2MTransfer( m ) {}
     #if defined(__clang__)
       #pragma clang diagnostic pop
     #endif
+
+    //! Register mesh with the mesh-to-mesh transfer library
     void addMesh(CkArrayID p, int elem, CkCallback cb);
+
     void setMesh(CkArrayID p, MeshData d);
     void setSourceTets(CkArrayID p, int index, std::vector< std::size_t >* inpoel,
                        tk::UnsMesh::Coords* coords, const tk::Fields& u);
     void setDestPoints(CkArrayID p, int index, tk::UnsMesh::Coords* coords,
                        tk::Fields& u, CkCallback cb);
     void distributeCollisions(int nColl, Collision* colls);
+
+    //! Pack/Unpack serialize member function for Charm
+    void pup(PUP::er&) {}
+    //! Pack/Unpack serialize operator| for Charm
+    friend void operator|( PUP::er& p, M2MTransfer& m ) { m.pup(p); }
 };
 
 }
+
+#endif // M2MTransfer_hpp
diff --git a/src/Transfer/TransferDetails.cpp b/src/Transfer/TransferDetails.cpp
index b26f190e817..7f840bd5304 100644
--- a/src/Transfer/TransferDetails.cpp
+++ b/src/Transfer/TransferDetails.cpp
@@ -16,6 +16,7 @@
 #include "M2MTransfer.hpp"
 
 #include "collidecharm.h"
+#include <iostream>
 
 #if defined(__clang__)
   #pragma clang diagnostic push
@@ -43,10 +44,12 @@ TransferDetails::TransferDetails( CkArrayID p, MeshData d, CkCallback cb ) :
 //! \param[in] cb Callback to inform application that the library is ready
 // *****************************************************************************
 {
+  std::cout << "TransferDetails() ctor beginning... " << thisIndex << std::endl;
   CollideRegister(collideHandle, m_firstchunk + thisIndex);
   d.m_proxy = thisProxy;
   m2mtransferProxy.ckLocalBranch()->setMesh( p, d );
   contribute(cb);
+  std::cout << "TransferDetails() ctor complete. " << thisIndex << std::endl;
 }
 
 void
@@ -123,6 +126,9 @@ TransferDetails::collideVertices()
     prio[nBoxes] = firstchunk;
     ++nBoxes;
   }
+
+  std::cout << "colliding vertices " << nBoxes << std::endl;
+
   CollideBoxesPrio( collideHandle, firstchunk + thisIndex,
                     static_cast<int>(nBoxes), boxes.data(), prio.data() );
 }
@@ -149,6 +155,9 @@ TransferDetails::collideTets() const
       boxes[i].add(CkVector3d(coord[0][p], coord[1][p], coord[2][p]));
     }
   }
+
+  std::cout << "colliding tets " << nBoxes << std::endl;
+
   CollideBoxesPrio( collideHandle, firstchunk + thisIndex,
                     static_cast<int>(nBoxes), boxes.data(), prio.data() );
 }
diff --git a/src/Transfer/TransferDetails.hpp b/src/Transfer/TransferDetails.hpp
index e8f5c6091af..0d5cfc3874f 100644
--- a/src/Transfer/TransferDetails.hpp
+++ b/src/Transfer/TransferDetails.hpp
@@ -80,19 +80,6 @@ class TransferDetails : public CBase_TransferDetails {
     //! Transfer the interpolated solution data back to destination mesh
     void transferSolution( const std::vector< SolutionData >& soln );
 
-    /** @name Charm++ pack/unpack serializer member functions */
-    ///@{
-    //! \brief Pack/Unpack serialize member function
-    //! \param[in,out] p Charm++'s PUP::er serializer object reference
-    void pup( PUP::er &p ) override {
-      p | m_firstchunk;
-    }
-    //! \brief Pack/Unpack serialize operator|
-    //! \param[in,out] p Charm++'s PUP::er serializer object reference
-    //! \param[in,out] i TransferDetails object reference
-    friend void operator|( PUP::er& p, TransferDetails& i ) { i.pup(p); }
-    //@}
-
   private:
     //! The ID of my first chunk (used for collision detection library)
     int m_firstchunk;
diff --git a/src/Transfer/m2mtransfer.ci b/src/Transfer/m2mtransfer.ci
index b9f9b4cee13..24a821ec4f1 100644
--- a/src/Transfer/m2mtransfer.ci
+++ b/src/Transfer/m2mtransfer.ci
@@ -9,7 +9,7 @@ module m2mtransfer {
 
     class MeshData;
 
-    mainchare LibMain {
+    mainchare [migratable] LibMain {
       entry LibMain(CkArgMsg* msg);
     };