diff --git a/framework/src/problems/EigenProblem.C b/framework/src/problems/EigenProblem.C
index d4b6073e3ef0..02c2e3c9793e 100644
--- a/framework/src/problems/EigenProblem.C
+++ b/framework/src/problems/EigenProblem.C
@@ -19,6 +19,7 @@
 #include "OutputWarehouse.h"
 #include "Function.h"
 #include "MooseVariableScalar.h"
+#include "UserObject.h"
 
 // libMesh includes
 #include "libmesh/system.h"
@@ -493,6 +494,16 @@ EigenProblem::checkProblemIntegrity()
 {
   FEProblemBase::checkProblemIntegrity();
   _nl_eigen->checkIntegrity();
+  if (_bx_norm_name)
+  {
+    if (!isNonlinearEigenvalueSolver())
+      paramWarning("bx_norm", "This parameter is only used for nonlinear solve types");
+    else if (auto & pp = getUserObjectBase(_bx_norm_name.value());
+             !pp.getExecuteOnEnum().contains(EXEC_LINEAR))
+      pp.paramError("execute_on",
+                    "If providing the Bx norm, this postprocessor must execute on linear e.g. "
+                    "during residual evaluations");
+  }
 }
 
 void
diff --git a/framework/src/utils/SlepcSupport.C b/framework/src/utils/SlepcSupport.C
index bd9e0cda1a2d..3b7c82119d1b 100644
--- a/framework/src/utils/SlepcSupport.C
+++ b/framework/src/utils/SlepcSupport.C
@@ -951,6 +951,13 @@ mooseSlepcEigenFormFunctionB(SNES snes, Vec x, Vec r, void * ctx)
 
     ierr = MatMult(B, x, r);
     CHKERRQ(ierr);
+
+    if (eigen_problem->bxNormProvided())
+    {
+      // User has provided a postprocessor. We need it updated
+      updateCurrentLocalSolution(eigen_nl.sys(), x);
+      eigen_problem->execute(EXEC_LINEAR);
+    }
   }
   else
     moosePetscSNESFormFunction(snes, x, r, ctx, eigen_nl.eigenVectorTag());
@@ -1006,6 +1013,13 @@ mooseSlepcEigenFormFunctionAB(SNES /*snes*/, Vec x, Vec Ax, Vec Bx, void * ctx)
       CHKERRQ(ierr);
     }
 
+    if (eigen_problem->bxNormProvided())
+    {
+      // User has provided a postprocessor. We need it updated
+      updateCurrentLocalSolution(sys, x);
+      eigen_problem->execute(EXEC_LINEAR);
+    }
+
     PetscFunctionReturn(PETSC_SUCCESS);
   }
 
diff --git a/test/tests/problems/eigen_problem/jfnk_mo/ne_coupled_mo.i b/test/tests/problems/eigen_problem/jfnk_mo/ne_coupled_mo.i
index 49c050270a83..b29d122959e6 100644
--- a/test/tests/problems/eigen_problem/jfnk_mo/ne_coupled_mo.i
+++ b/test/tests/problems/eigen_problem/jfnk_mo/ne_coupled_mo.i
@@ -79,6 +79,20 @@
   type = Eigenvalue
   solve_type = PJFNKMO
   nl_rel_tol = 1e-6
+  nl_abs_tol = 1e-14
+[]
+
+[Problem]
+  type = EigenProblem
+[]
+
+[Postprocessors]
+  [uint]
+    type = ElementIntegralVariablePostprocessor
+    variable = u
+    execute_on = 'initial linear nonlinear'
+    outputs = 'console'
+  []
 []
 
 [VectorPostprocessors]
diff --git a/test/tests/problems/eigen_problem/jfnk_mo/tests b/test/tests/problems/eigen_problem/jfnk_mo/tests
index 13ba015af496..66fccbf57158 100644
--- a/test/tests/problems/eigen_problem/jfnk_mo/tests
+++ b/test/tests/problems/eigen_problem/jfnk_mo/tests
@@ -54,19 +54,41 @@
   []
 
   [ne_coupled_mo]
-    type = 'CSVDiff'
-    input = 'ne_coupled_mo.i'
-    csvdiff = 'ne_coupled_eigenvalues_0001.csv'
-    slepc = true
-    slepc_version = '>=3.11.0'
-    requirement = "The system shall support use of matrix-vector multiplication as residual evaluation for coupled eigenvalue problems"
+    requirement = "The system shall support use of matrix-vector multiplication as residual evaluation for coupled eigenvalue problems with the bx norm"
+    issues = "#18493 #21056 #28993"
+    [l2_bx]
+      type = 'CSVDiff'
+      input = 'ne_coupled_mo.i'
+      csvdiff = 'ne_coupled_eigenvalues_0001.csv'
+      slepc = true
+      slepc_version = '>=3.11.0'
+      detail = 'computed as the L2 norm of the bx vector, or'
+    []
+    [custom_bx]
+      type = 'CSVDiff'
+      input = 'ne_coupled_mo.i'
+      csvdiff = 'ne_coupled_eigenvalues_0001.csv'
+      cli_args = 'Problem/bx_norm=uint'
+      slepc = true
+      slepc_version = '>=3.11.0'
+      detail = 'computed by a user provided postprocessor.'
+      prereq = 'ne_coupled_mo/l2_bx'
+    []
+  []
+  [missing_bx_norm_exec_linear]
+    type = RunException
+    issues = '#28993'
+    input = ne_coupled_mo.i
+    cli_args = "Problem/bx_norm=uint Postprocessors/uint/execute_on='initial nonlinear'"
+    requirement = 'The system shall error if the user wants the Bx norm provided by a postprocessor but the postprocessor is not executed during residual evaluations.'
+    expect_err = "If providing the Bx norm, this postprocessor must execute on linear"
   []
 
   [ne_coupled_mo_full]
     type = 'CSVDiff'
     input = 'ne_coupled_mo.i'
     csvdiff = 'ne_coupled_eigenvalues_0001.csv'
-    prereq = 'ne_coupled_mo'
+    prereq = 'ne_coupled_mo/custom_bx'
     cli_args = 'Preconditioning/active='''
     slepc = true
     slepc_version = '>=3.11.0'