diff --git a/src/KSPACE/pppm.h b/src/KSPACE/pppm.h
index 1ce1a0d666..b84dfe26c4 100644
--- a/src/KSPACE/pppm.h
+++ b/src/KSPACE/pppm.h
@@ -20,8 +20,7 @@ KSpaceStyle(pppm,PPPM)
 #ifndef LMP_PPPM_H
 #define LMP_PPPM_H
 
-#include "lmptype.h"
-#include <mpi.h>
+#include "kspace.h"
 
 #ifdef FFT_SINGLE
 typedef float FFT_SCALAR;
@@ -31,8 +30,6 @@ typedef double FFT_SCALAR;
 #define MPI_FFT_SCALAR MPI_DOUBLE
 #endif
 
-#include "kspace.h"
-
 namespace LAMMPS_NS {
 
 class PPPM : public KSpace {
diff --git a/src/KSPACE/pppm_disp.h b/src/KSPACE/pppm_disp.h
index ccbeb60f3c..8582e98acd 100644
--- a/src/KSPACE/pppm_disp.h
+++ b/src/KSPACE/pppm_disp.h
@@ -20,8 +20,7 @@ KSpaceStyle(pppm/disp,PPPMDisp)
 #ifndef LMP_PPPM_DISP_H
 #define LMP_PPPM_DISP_H
 
-#include "lmptype.h"
-#include <mpi.h>
+#include "kspace.h"
 
 #ifdef FFT_SINGLE
 typedef float FFT_SCALAR;
@@ -31,8 +30,6 @@ typedef double FFT_SCALAR;
 #define MPI_FFT_SCALAR MPI_DOUBLE
 #endif
 
-#include "kspace.h"
-
 namespace LAMMPS_NS {
 
 
diff --git a/src/MPIIO/dump_xyz_mpiio.cpp b/src/MPIIO/dump_xyz_mpiio.cpp
index ee0532399a..f5caab3a9c 100644
--- a/src/MPIIO/dump_xyz_mpiio.cpp
+++ b/src/MPIIO/dump_xyz_mpiio.cpp
@@ -21,7 +21,6 @@
 #include <cstring>
 #include "domain.h"
 #include "update.h"
-#include "modify.h"
 #include "compute.h"
 #include "memory.h"
 #include "error.h"
diff --git a/src/USER-AWPMD/atom_vec_wavepacket.cpp b/src/USER-AWPMD/atom_vec_wavepacket.cpp
index 3dc624e4b8..bce334a7b3 100644
--- a/src/USER-AWPMD/atom_vec_wavepacket.cpp
+++ b/src/USER-AWPMD/atom_vec_wavepacket.cpp
@@ -16,7 +16,6 @@
 ------------------------------------------------------------------------- */
 
 #include "atom_vec_wavepacket.h"
-#include <cmath>
 #include <cstring>
 #include "atom.h"
 #include "comm.h"
diff --git a/src/USER-AWPMD/fix_nve_awpmd.cpp b/src/USER-AWPMD/fix_nve_awpmd.cpp
index 57ad17f3e6..a147a11081 100644
--- a/src/USER-AWPMD/fix_nve_awpmd.cpp
+++ b/src/USER-AWPMD/fix_nve_awpmd.cpp
@@ -16,14 +16,13 @@
 ------------------------------------------------------------------------- */
 
 #include "fix_nve_awpmd.h"
-#include <cmath>
-#include <cstdio>
-#include <cstring>
+#include "pair_awpmd_cut.h"
 #include "atom.h"
 #include "force.h"
 #include "update.h"
 #include "respa.h"
 #include "error.h"
+#include "utils.h"
 
 #include "TCP/wpmd_split.h"
 
@@ -62,7 +61,7 @@ void FixNVEAwpmd::init()
   dtv = update->dt;
   dtf = 0.5 * update->dt * force->ftm2v;
 
-  if (strstr(update->integrate_style,"respa"))
+  if (utils::strmatch(update->integrate_style,"^respa"))
     step_respa = ((Respa *) update->integrate)->step;
 
   awpmd_pair=(PairAWPMDCut *)force->pair;
diff --git a/src/USER-AWPMD/fix_nve_awpmd.h b/src/USER-AWPMD/fix_nve_awpmd.h
index 140d234308..832f5821a3 100644
--- a/src/USER-AWPMD/fix_nve_awpmd.h
+++ b/src/USER-AWPMD/fix_nve_awpmd.h
@@ -25,7 +25,6 @@ FixStyle(nve/awpmd,FixNVEAwpmd)
 #define LMP_FIX_NVE_awpmd_H
 
 #include "fix.h"
-#include "pair_awpmd_cut.h"
 
 namespace LAMMPS_NS {
 
@@ -45,7 +44,7 @@ class FixNVEAwpmd : public Fix {
   double *step_respa;
   int mass_require;
 
-  PairAWPMDCut *awpmd_pair;
+  class PairAWPMDCut *awpmd_pair;
 };
 
 }
diff --git a/src/USER-AWPMD/pair_awpmd_cut.cpp b/src/USER-AWPMD/pair_awpmd_cut.cpp
index ae2fbc59fa..75ebb0e251 100644
--- a/src/USER-AWPMD/pair_awpmd_cut.cpp
+++ b/src/USER-AWPMD/pair_awpmd_cut.cpp
@@ -16,10 +16,11 @@
 ------------------------------------------------------------------------- */
 
 #include "pair_awpmd_cut.h"
+#include <mpi.h>
 #include <cmath>
-#include <cstdio>
-#include <cstdlib>
 #include <cstring>
+#include <map>
+#include <utility>
 #include "atom.h"
 #include "update.h"
 #include "min.h"
@@ -32,6 +33,9 @@
 #include "memory.h"
 #include "error.h"
 
+#include "logexc.h"
+#include "vector_3.h"
+#include "TCP/wpmd.h"
 #include "TCP/wpmd_split.h"
 
 using namespace LAMMPS_NS;
diff --git a/src/USER-BOCS/compute_pressure_bocs.cpp b/src/USER-BOCS/compute_pressure_bocs.cpp
index ee1ad33f88..d0a24b99a3 100644
--- a/src/USER-BOCS/compute_pressure_bocs.cpp
+++ b/src/USER-BOCS/compute_pressure_bocs.cpp
@@ -16,6 +16,7 @@
 
 #include "compute_pressure_bocs.h"
 #include <mpi.h>
+#include <cmath>
 #include <cstring>
 #include <cstdlib>
 #include "atom.h"
diff --git a/src/USER-CGSDK/pair_lj_sdk.cpp b/src/USER-CGSDK/pair_lj_sdk.cpp
index 6ad77a6183..1301dc4155 100644
--- a/src/USER-CGSDK/pair_lj_sdk.cpp
+++ b/src/USER-CGSDK/pair_lj_sdk.cpp
@@ -24,7 +24,6 @@
 #include "comm.h"
 #include "force.h"
 #include "neigh_list.h"
-#include "math_const.h"
 #include "memory.h"
 #include "error.h"
 
@@ -32,7 +31,6 @@
 #include "lj_sdk_common.h"
 
 using namespace LAMMPS_NS;
-using namespace MathConst;
 using namespace LJSDKParms;
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/USER-CGSDK/pair_lj_sdk_coul_msm.cpp b/src/USER-CGSDK/pair_lj_sdk_coul_msm.cpp
index 1095521de3..f168089fae 100644
--- a/src/USER-CGSDK/pair_lj_sdk_coul_msm.cpp
+++ b/src/USER-CGSDK/pair_lj_sdk_coul_msm.cpp
@@ -23,7 +23,6 @@
 #include "force.h"
 #include "kspace.h"
 #include "neigh_list.h"
-#include "memory.h"
 #include "error.h"
 
 #include "lj_sdk_common.h"
diff --git a/src/USER-DPD/fix_shardlow.cpp b/src/USER-DPD/fix_shardlow.cpp
index f181436f91..b0efeb634d 100644
--- a/src/USER-DPD/fix_shardlow.cpp
+++ b/src/USER-DPD/fix_shardlow.cpp
@@ -37,15 +37,16 @@
 #include <cstdlib>
 #include <cstring>
 #include <cmath>
+#include <stdint.h>
 #include "atom.h"
 #include "force.h"
 #include "update.h"
 #include "error.h"
-#include "atom_vec.h"
 #include "comm.h"
 #include "neighbor.h"
 #include "neigh_list.h"
 #include "neigh_request.h"
+#include "npair.h"
 #include "memory.h"
 #include "domain.h"
 #include "modify.h"
diff --git a/src/USER-OMP/pair_reaxc_omp.cpp b/src/USER-OMP/pair_reaxc_omp.cpp
index 2f17515130..aedd438066 100644
--- a/src/USER-OMP/pair_reaxc_omp.cpp
+++ b/src/USER-OMP/pair_reaxc_omp.cpp
@@ -34,6 +34,8 @@
  ------------------------------------------------------------------------- */
 
 #include "pair_reaxc_omp.h"
+#include <mpi.h>
+#include <cmath>
 #include "atom.h"
 #include "update.h"
 #include "force.h"
@@ -42,32 +44,27 @@
 #include "neigh_list.h"
 #include "neigh_request.h"
 #include "modify.h"
-#include "fix.h"
 #include "fix_reaxc.h"
 #include "citeme.h"
 #include "memory.h"
 #include "error.h"
 #include "timer.h"
 
+#include "reaxc_defs.h"
 #include "reaxc_types.h"
 #include "reaxc_allocate.h"
-#include "reaxc_control.h"
-#include "reaxc_ffield.h"
 #include "reaxc_forces_omp.h"
 #include "reaxc_init_md_omp.h"
 #include "reaxc_io_tools.h"
 #include "reaxc_list.h"
-#include "reaxc_lookup.h"
 #include "reaxc_reset_tools.h"
 #include "reaxc_tool_box.h"
-#include "reaxc_traj.h"
-#include "reaxc_vector.h"
-#include "fix_reaxc_bonds.h"
 
 #if defined(_OPENMP)
 #include <omp.h>
 #endif
 
+#include "suffix.h"
 using namespace LAMMPS_NS;
 
 #ifdef OMP_TIMING
diff --git a/src/accelerator_kokkos.h b/src/accelerator_kokkos.h
index 74bd470572..a3fff2fe16 100644
--- a/src/accelerator_kokkos.h
+++ b/src/accelerator_kokkos.h
@@ -19,14 +19,14 @@
 
 #ifdef LMP_KOKKOS
 
-#include "kokkos.h"
-#include "atom_kokkos.h"
-#include "comm_kokkos.h"
-#include "comm_tiled_kokkos.h"
-#include "domain_kokkos.h"
-#include "neighbor_kokkos.h"
-#include "memory_kokkos.h"
-#include "modify_kokkos.h"
+#include "kokkos.h"              // IWYU pragma: export
+#include "atom_kokkos.h"         // IWYU pragma: export
+#include "comm_kokkos.h"         // IWYU pragma: export
+#include "comm_tiled_kokkos.h"   // IWYU pragma: export
+#include "domain_kokkos.h"       // IWYU pragma: export
+#include "neighbor_kokkos.h"     // IWYU pragma: export
+#include "memory_kokkos.h"       // IWYU pragma: export
+#include "modify_kokkos.h"       // IWYU pragma: export
 
 #define LAMMPS_INLINE KOKKOS_INLINE_FUNCTION
 
diff --git a/src/finish.cpp b/src/finish.cpp
index bef3ae89eb..9ab97ae410 100644
--- a/src/finish.cpp
+++ b/src/finish.cpp
@@ -16,8 +16,6 @@
 #include <cmath>
 #include <cstdlib>
 #include <cstring>
-#include "timer.h"
-#include "universe.h"
 #include "accelerator_kokkos.h"
 #include "atom.h"
 #include "atom_vec.h"
@@ -32,6 +30,8 @@
 #include "neigh_request.h"
 #include "memory.h"
 #include "error.h"
+#include "timer.h"
+#include "universe.h"
 
 #ifdef LMP_USER_OMP
 #include "modify.h"