diff --git a/.github/workflows/ci_tests.yml b/.github/workflows/ci_tests.yml
index 7ab583d9683..0651caa88b6 100644
--- a/.github/workflows/ci_tests.yml
+++ b/.github/workflows/ci_tests.yml
@@ -97,7 +97,7 @@ jobs:
       fail-fast : false
       matrix:
         include:
-        # Validates the code-style using uncrustify
+        # Validates C++ style (uncrustify) and XML formatting (format_xml)
         - name: Check code style
           BUILD_AND_TEST_ARGS: --test-code-style
         # Validates that the documentation generated using doxygen has no hole.
diff --git a/examples/GPU/beamBending.xml b/examples/GPU/beamBending.xml
index 2d5c3852bed..fa00000d237 100644
--- a/examples/GPU/beamBending.xml
+++ b/examples/GPU/beamBending.xml
@@ -12,9 +12,7 @@
       discretization="FE1"
       targetRegions="{ Region2 }">
       <!-- SPHINX_SolidMechanicsSolverEnd -->
-      <NonlinearSolverParameters
-        newtonTol="1.0e-6"
-        newtonMaxIter="8"/>
+      <NonlinearSolverParameters newtonTol="1.0e-6" newtonMaxIter="8"/>
       <LinearSolverParameters
         logLevel="1"
         solverType="gmres"
@@ -43,10 +41,7 @@
     <!-- This event is applied every cycle, and overrides the
     solver time-step request -->
     <!-- SPHINX_Execution -->
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1.0"
-      target="/Solvers/lagsolve"/>
+    <PeriodicEvent name="solverApplications" forceDt="1.0" target="/Solvers/lagsolve"/>
 
     <!-- SPHINX_ExecutionEnd -->
     <!-- This event is applied every 5.0e-5s.  The targetExactTimestep
@@ -67,18 +62,13 @@
   <!-- SPHINX_FEDiscretization -->
   <NumericalMethods>
     <FiniteElements>
-      <FiniteElementSpace
-        name="FE1"
-        order="1"/>
+      <FiniteElementSpace name="FE1" order="1"/>
     </FiniteElements>
   </NumericalMethods>
 
   <!-- SPHINX_FEDiscretizationEnd -->
   <ElementRegions>
-    <CellElementRegion
-      name="Region2"
-      cellBlocks="{ * }"
-      materialList="{ shale }"/>
+    <CellElementRegion name="Region2" cellBlocks="{ * }" materialList="{ shale }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -145,12 +135,8 @@
 
   <!-- SPHINX_TableFunctionEnd -->
   <Outputs>
-    <Silo
-      name="siloOutput"
-      parallelThreads="32"
-      childDirectory="sub"/>
+    <Silo name="siloOutput" parallelThreads="32" childDirectory="sub"/>
 
-    <Restart
-      name="restartOutput"/>
+    <Restart name="restartOutput"/>
   </Outputs>
 </Problem>
diff --git a/examples/advanced_xml_features/included/included_a.xml b/examples/advanced_xml_features/included/included_a.xml
index 66f4abed35e..11fb9aa0960 100644
--- a/examples/advanced_xml_features/included/included_a.xml
+++ b/examples/advanced_xml_features/included/included_a.xml
@@ -7,9 +7,7 @@
       name="SinglePhaseFlow"
       discretization="singlePhaseTPFA"
       targetRegions="{ Region1 }">
-      <LinearSolverParameters
-        solverType="gmres"
-        krylovTol="1.0e-12"/>
+      <LinearSolverParameters solverType="gmres" krylovTol="1.0e-12"/>
     </SinglePhaseFVM>
   </Solvers>
 
@@ -27,14 +25,8 @@
   </Mesh>
 
   <Geometry>
-    <Box
-      name="source"
-      xMin="{ -0.01, -0.01, -0.01 }"
-      xMax="{ 1.01, 1.01, 1.01 }"/>
+    <Box name="source" xMin="{ -0.01, -0.01, -0.01 }" xMax="{ 1.01, 1.01, 1.01 }"/>
 
-    <Box
-      name="sink"
-      xMin="{ 8.99, -0.01, -0.01 }"
-      xMax="{ 10.01, 1.01, 1.01 }"/>
+    <Box name="sink" xMin="{ 8.99, -0.01, -0.01 }" xMax="{ 10.01, 1.01, 1.01 }"/>
   </Geometry>
 </Problem>
diff --git a/examples/advanced_xml_features/included/included_b.xml b/examples/advanced_xml_features/included/included_b.xml
index ba2aa87baed..b0bd9da3a2c 100644
--- a/examples/advanced_xml_features/included/included_b.xml
+++ b/examples/advanced_xml_features/included/included_b.xml
@@ -3,15 +3,9 @@
 <Problem>
   <Events
     maxTime="2e4">
-    <PeriodicEvent
-      name="outputs"
-      timeFrequency="1000.0"
-      target="/Outputs/siloOutput"/>
+    <PeriodicEvent name="outputs" timeFrequency="1000.0" target="/Outputs/siloOutput"/>
 
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1e3"
-      target="/Solvers/SinglePhaseFlow"/>
+    <PeriodicEvent name="solverApplications" forceDt="1e3" target="/Solvers/SinglePhaseFlow"/>
 
     <PeriodicEvent
       name="restarts"
@@ -22,16 +16,12 @@
 
   <NumericalMethods>
     <FiniteVolume>
-      <TwoPointFluxApproximation
-        name="singlePhaseTPFA"/>
+      <TwoPointFluxApproximation name="singlePhaseTPFA"/>
     </FiniteVolume>
   </NumericalMethods>
 
   <ElementRegions>
-    <CellElementRegion
-      name="Region1"
-      cellBlocks="{ * }"
-      materialList="{ water, rock }"/>
+    <CellElementRegion name="Region1" cellBlocks="{ * }" materialList="{ water, rock }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -49,8 +39,7 @@
       porosityModelName="rockPorosity"
       permeabilityModelName="rockPerm"/>
 
-    <NullModel
-      name="nullSolid"/>
+    <NullModel name="nullSolid"/>
 
     <PressurePorosity
       name="rockPorosity"
@@ -58,16 +47,12 @@
       referencePressure="0.0"
       compressibility="1.0e-9"/>
 
-    <ConstantPermeability
-      name="rockPerm"
-      permeabilityComponents="{ 2.0e-16, 2.0e-16, 2.0e-16 }"/>
+    <ConstantPermeability name="rockPerm" permeabilityComponents="{ 2.0e-16, 2.0e-16, 2.0e-16 }"/>
   </Constitutive>
 
   <Outputs>
-    <Silo
-      name="siloOutput"/>
+    <Silo name="siloOutput"/>
 
-    <Restart
-      name="restartOutput"/>
+    <Restart name="restartOutput"/>
   </Outputs>
 </Problem>
diff --git a/examples/advanced_xml_features/included_files_example.xml b/examples/advanced_xml_features/included_files_example.xml
index 1e36184f8ff..191249136f3 100644
--- a/examples/advanced_xml_features/included_files_example.xml
+++ b/examples/advanced_xml_features/included_files_example.xml
@@ -17,13 +17,10 @@ using the following rules:
     Otherwise insert the target into the xml structure as-is
 -->
   <Included>
-    <File
-      name="./included/included_a.xml"/>
+    <File name="./included/included_a.xml"/>
 
-    <File
-      name="./included/included_b.xml"/>
+    <File name="./included/included_b.xml"/>
 
-    <File
-      name="./included/included_c.xml"/>
+    <File name="./included/included_c.xml"/>
   </Included>
 </Problem>
diff --git a/examples/advanced_xml_features/parameters_example.xml b/examples/advanced_xml_features/parameters_example.xml
index fa31e5d4bd3..a8b92c7a1ad 100644
--- a/examples/advanced_xml_features/parameters_example.xml
+++ b/examples/advanced_xml_features/parameters_example.xml
@@ -17,17 +17,11 @@ XML Units:
      - These use a python-style format e.g. (0.1 [m/s**2])
 -->
   <Parameters>
-    <Parameter
-      name="permeability"
-      value="2.0e-16"/>
+    <Parameter name="permeability" value="2.0e-16"/>
 
-    <Parameter
-      name="porosity"
-      value="0.05"/>
+    <Parameter name="porosity" value="0.05"/>
 
-    <Parameter
-      name="pressure"
-      value="5 [MPa]"/>
+    <Parameter name="pressure" value="5 [MPa]"/>
   </Parameters>
 
   <Solvers
@@ -36,9 +30,7 @@ XML Units:
       name="SinglePhaseFlow"
       discretization="singlePhaseTPFA"
       targetRegions="{ Region1 }">
-      <LinearSolverParameters
-        solverType="gmres"
-        krylovTol="1.0e-12"/>
+      <LinearSolverParameters solverType="gmres" krylovTol="1.0e-12"/>
     </SinglePhaseFVM>
   </Solvers>
 
@@ -56,28 +48,16 @@ XML Units:
   </Mesh>
 
   <Geometry>
-    <Box
-      name="source"
-      xMin="{ -0.01, -0.01, -0.01 }"
-      xMax="{ 1.01, 1.01, 1.01 }"/>
-
-    <Box
-      name="sink"
-      xMin="{ 8.99, -0.01, -0.01 }"
-      xMax="{ 10.01, 1.01, 1.01 }"/>
+    <Box name="source" xMin="{ -0.01, -0.01, -0.01 }" xMax="{ 1.01, 1.01, 1.01 }"/>
+
+    <Box name="sink" xMin="{ 8.99, -0.01, -0.01 }" xMax="{ 10.01, 1.01, 1.01 }"/>
   </Geometry>
 
   <Events
     maxTime="2e4">
-    <PeriodicEvent
-      name="outputs"
-      timeFrequency="1000.0"
-      target="/Outputs/siloOutput"/>
+    <PeriodicEvent name="outputs" timeFrequency="1000.0" target="/Outputs/siloOutput"/>
 
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1e3"
-      target="/Solvers/SinglePhaseFlow"/>
+    <PeriodicEvent name="solverApplications" forceDt="1e3" target="/Solvers/SinglePhaseFlow"/>
 
     <PeriodicEvent
       name="restarts"
@@ -88,16 +68,12 @@ XML Units:
 
   <NumericalMethods>
     <FiniteVolume>
-      <TwoPointFluxApproximation
-        name="singlePhaseTPFA"/>
+      <TwoPointFluxApproximation name="singlePhaseTPFA"/>
     </FiniteVolume>
   </NumericalMethods>
 
   <ElementRegions>
-    <CellElementRegion
-      name="Region1"
-      cellBlocks="{ * }"
-      materialList="{ water, rock }"/>
+    <CellElementRegion name="Region1" cellBlocks="{ * }" materialList="{ water, rock }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -115,8 +91,7 @@ XML Units:
       porosityModelName="rockPorosity"
       permeabilityModelName="rockPerm"/>
 
-    <NullModel
-      name="nullSolid"/>
+    <NullModel name="nullSolid"/>
 
     <PressurePorosity
       name="rockPorosity"
@@ -130,11 +105,9 @@ XML Units:
   </Constitutive>
 
   <Outputs>
-    <Silo
-      name="siloOutput"/>
+    <Silo name="siloOutput"/>
 
-    <Restart
-      name="restartOutput"/>
+    <Restart name="restartOutput"/>
   </Outputs>
 
   <FieldSpecifications>
diff --git a/examples/advanced_xml_features/symbolic_math_example.xml b/examples/advanced_xml_features/symbolic_math_example.xml
index e4d3f4942dd..573c801f714 100644
--- a/examples/advanced_xml_features/symbolic_math_example.xml
+++ b/examples/advanced_xml_features/symbolic_math_example.xml
@@ -27,17 +27,11 @@ XML Symbolic Math:
       - This constraint can be relaxed to allow more complicated functions (sin, cos, etc.)
 -->
   <Parameters>
-    <Parameter
-      name="permeability"
-      value="2.0e-16"/>
+    <Parameter name="permeability" value="2.0e-16"/>
 
-    <Parameter
-      name="porosity"
-      value="0.05"/>
+    <Parameter name="porosity" value="0.05"/>
 
-    <Parameter
-      name="pressure"
-      value="5 [MPa]"/>
+    <Parameter name="pressure" value="5 [MPa]"/>
   </Parameters>
 
   <Solvers
@@ -46,9 +40,7 @@ XML Symbolic Math:
       name="SinglePhaseFlow"
       discretization="singlePhaseTPFA"
       targetRegions="{ Region1 }">
-      <LinearSolverParameters
-        solverType="gmres"
-        krylovTol="1.0e-12"/>
+      <LinearSolverParameters solverType="gmres" krylovTol="1.0e-12"/>
     </SinglePhaseFVM>
   </Solvers>
 
@@ -66,28 +58,16 @@ XML Symbolic Math:
   </Mesh>
 
   <Geometry>
-    <Box
-      name="source"
-      xMin="{ -0.01, -0.01, -0.01 }"
-      xMax="{ 1.01, 1.01, 1.01 }"/>
-
-    <Box
-      name="sink"
-      xMin="{ 8.99, -0.01, -0.01 }"
-      xMax="{ 10.01, 1.01, 1.01 }"/>
+    <Box name="source" xMin="{ -0.01, -0.01, -0.01 }" xMax="{ 1.01, 1.01, 1.01 }"/>
+
+    <Box name="sink" xMin="{ 8.99, -0.01, -0.01 }" xMax="{ 10.01, 1.01, 1.01 }"/>
   </Geometry>
 
   <Events
     maxTime="2e4">
-    <PeriodicEvent
-      name="outputs"
-      timeFrequency="1000.0"
-      target="/Outputs/siloOutput"/>
+    <PeriodicEvent name="outputs" timeFrequency="1000.0" target="/Outputs/siloOutput"/>
 
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1e3"
-      target="/Solvers/SinglePhaseFlow"/>
+    <PeriodicEvent name="solverApplications" forceDt="1e3" target="/Solvers/SinglePhaseFlow"/>
 
     <PeriodicEvent
       name="restarts"
@@ -98,16 +78,12 @@ XML Symbolic Math:
 
   <NumericalMethods>
     <FiniteVolume>
-      <TwoPointFluxApproximation
-        name="singlePhaseTPFA"/>
+      <TwoPointFluxApproximation name="singlePhaseTPFA"/>
     </FiniteVolume>
   </NumericalMethods>
 
   <ElementRegions>
-    <CellElementRegion
-      name="Region1"
-      cellBlocks="{ * }"
-      materialList="{ water, rock }"/>
+    <CellElementRegion name="Region1" cellBlocks="{ * }" materialList="{ water, rock }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -125,8 +101,7 @@ XML Symbolic Math:
       porosityModelName="rockPorosity"
       permeabilityModelName="rockPerm"/>
 
-    <NullModel
-      name="nullSolid"/>
+    <NullModel name="nullSolid"/>
 
     <PressurePorosity
       name="rockPorosity"
@@ -140,11 +115,9 @@ XML Symbolic Math:
   </Constitutive>
 
   <Outputs>
-    <Silo
-      name="siloOutput"/>
+    <Silo name="siloOutput"/>
 
-    <Restart
-      name="restartOutput"/>
+    <Restart name="restartOutput"/>
   </Outputs>
 
   <FieldSpecifications>
diff --git a/examples/event_examples.xml b/examples/event_examples.xml
index 582343b5875..0059c9f4ae8 100644
--- a/examples/event_examples.xml
+++ b/examples/event_examples.xml
@@ -5,40 +5,27 @@
     maxTime="10"
     logLevel="1">
     <!-- This event will execute every cycle, and will always request dt = 1 -->
-    <PeriodicEvent
-      name="periodic_a"
-      forceDt="1"/>
+    <PeriodicEvent name="periodic_a" forceDt="1"/>
 
     <!-- This event will execute every cycle, and will requset a max dt = 1 -->
-    <PeriodicEvent
-      name="periodic_b"
-      maxEventDt="1"
-      target="/Solvers/solver_a"/>
+    <PeriodicEvent name="periodic_b" maxEventDt="1" target="/Solvers/solver_a"/>
 
     <!-- This event will exectue every 5 s.  When necessary, it will request a dt
     that will cause it to be triggered at a time equal to a multiple of timeFrequency -->
-    <PeriodicEvent
-      name="periodic_c"
-      timeFrequency="5"
-      target="/Outputs/restartOutput"/>
+    <PeriodicEvent name="periodic_c" timeFrequency="5" target="/Outputs/restartOutput"/>
 
     <!-- This event will execute every 3 cycles.  When it does, it will attempt to
     execute each of its two sub-events -->
     <PeriodicEvent
       name="periodic_d"
       cycleFrequency="3">
-      <PeriodicEvent
-        name="subevent_a"/>
-      <PeriodicEvent
-        name="subevent_b"/>
+      <PeriodicEvent name="subevent_a"/>
+      <PeriodicEvent name="subevent_b"/>
     </PeriodicEvent>
 
     <!-- This event will request a dt = 3.3.  It will not not attempt to reduce its dt
     request to execute on multiples of timeFrequency -->
-    <PeriodicEvent
-      name="periodic_e"
-      timeFrequency="3.3"
-      targetExactTimestep="0"/>
+    <PeriodicEvent name="periodic_e" timeFrequency="3.3" targetExactTimestep="0"/>
 
     <!-- This event will execute every cycle from (beginTime <= time < endTime).
     It will limit its dt request so that the time will match beginTime and
@@ -47,29 +34,20 @@
       name="periodic_f"
       beginTime="6.1"
       endTime="8.3">
-      <PeriodicEvent
-        name="subevent_c"/>
-      <PeriodicEvent
-        name="subevent_d"/>
+      <PeriodicEvent name="subevent_c"/>
+      <PeriodicEvent name="subevent_d"/>
     </PeriodicEvent>
 
     <!-- This event will execute once during its target cycle -->
-    <SoloEvent
-      name="solo_a"
-      targetCycle="3"/>
+    <SoloEvent name="solo_a" targetCycle="3"/>
 
     <!-- This event will execute once during its target time.  It will limit
     its dt request to execute exactly at this time -->
-    <SoloEvent
-      name="solo_b"
-      targetTime="4"/>
+    <SoloEvent name="solo_b" targetTime="4"/>
 
     <!-- This event will execute once time >= targetTime.  It will not limit
     its dt request to exactly match targetTime -->
-    <SoloEvent
-      name="solo_c"
-      targetTime="5.123"
-      targetExactTimestep="0"/>
+    <SoloEvent name="solo_c" targetTime="5.123" targetExactTimestep="0"/>
 
     <!-- This event will execute when the wall time = maxRunTime.
     It will then set the exitFlag on the EventManager loop and
diff --git a/examples/functions/function_examples/function_examples.xml b/examples/functions/function_examples/function_examples.xml
index 0cc84199b48..5339f8e3ef0 100644
--- a/examples/functions/function_examples/function_examples.xml
+++ b/examples/functions/function_examples/function_examples.xml
@@ -5,10 +5,7 @@
     <!-- These are example mathpresso functions.  In order to use them, you need to specify the order that the 
     symbolic math function should expect the variables to be given, and an expression that it will compile.
     A list of available functions is given here: https://github.com/kobalicek/mathpresso -->
-    <SymbolicFunction
-      name="f_a"
-      variableNames="{ x, y, z, t }"
-      expression="x+y*z"/>
+    <SymbolicFunction name="f_a" variableNames="{ x, y, z, t }" expression="x+y*z"/>
 
     <SymbolicFunction
       name="f_b"
@@ -17,10 +14,7 @@
 
     <!-- As a special case, 1D tables may be specified using coordinates and values.
          A 1D table will only evaluate the first entry in evaluate (for the demo solver, this is x) -->
-    <TableFunction
-      name="f_c"
-      coordinates="{ -10, 10 }"
-      values="{ -10, 10 }"/>
+    <TableFunction name="f_c" coordinates="{ -10, 10 }" values="{ -10, 10 }"/>
 
     <!-- More generally, an ND table may be specified by giving a list of coordinate files, and a voxel file (with
          data in Fortran-array order).  Note: Unlike the old code, I do not look for header values in the voxel file.
diff --git a/examples/pygeosxExamples/hydraulicFractureWithMonitor/hydraulicFracture.xml b/examples/pygeosxExamples/hydraulicFractureWithMonitor/hydraulicFracture.xml
index d969cf46ea0..9b1af71602d 100644
--- a/examples/pygeosxExamples/hydraulicFractureWithMonitor/hydraulicFracture.xml
+++ b/examples/pygeosxExamples/hydraulicFractureWithMonitor/hydraulicFracture.xml
@@ -16,15 +16,11 @@
   <!-- SPHINX_HYDROFRACTURE_INCLUDED_PARAMETERS_END -->
   <!-- SPHINX_HYDROFRACTURE_EVENTS_OUTPUTS -->
   <Outputs>
-    <Python
-      name="pythonOutput"/>
+    <Python name="pythonOutput"/>
   </Outputs>
 
   <Events>
-    <PeriodicEvent
-      name="python"
-      cycleFrequency="10"
-      target="/Outputs/pythonOutput"/>
+    <PeriodicEvent name="python" cycleFrequency="10" target="/Outputs/pythonOutput"/>
   </Events>
 
   <!-- SPHINX_HYDROFRACTURE_EVENTS_OUTPUTS_END -->
diff --git a/examples/pygeosxExamples/modifyBoundaryCondition/pkn_example.xml b/examples/pygeosxExamples/modifyBoundaryCondition/pkn_example.xml
index 8d861acab42..5afe9514205 100644
--- a/examples/pygeosxExamples/modifyBoundaryCondition/pkn_example.xml
+++ b/examples/pygeosxExamples/modifyBoundaryCondition/pkn_example.xml
@@ -23,15 +23,10 @@
       solidSolverName="lagsolve"
       logLevel="1"
       flowSolverName="SinglePhaseFlow"
-      surfaceGeneratorName="SurfaceGen"      
+      surfaceGeneratorName="SurfaceGen"
       targetRegions="{ Domain, Fracture }">
-      <NonlinearSolverParameters
-        newtonMaxIter="50"
-        lineSearchMaxCuts="10"
-        newtonTol="1.0e-5"/>
-      <LinearSolverParameters
-        solverType="gmres"
-        preconditionerType="amg"/>
+      <NonlinearSolverParameters newtonMaxIter="50" lineSearchMaxCuts="10" newtonTol="1.0e-5"/>
+      <LinearSolverParameters solverType="gmres" preconditionerType="amg"/>
     </Hydrofracture>
 
     <SolidMechanicsLagrangianFEM
@@ -40,23 +35,16 @@
       name="lagsolve"
       targetRegions="{ Domain, Fracture }"
       contactPenaltyStiffness="1.0e0">
-      <NonlinearSolverParameters
-        newtonTol="1.0e-6"/>
-      <LinearSolverParameters
-        krylovTol="1.0e-10"
-        solverType="gmres"/>
+      <NonlinearSolverParameters newtonTol="1.0e-6"/>
+      <LinearSolverParameters krylovTol="1.0e-10" solverType="gmres"/>
     </SolidMechanicsLagrangianFEM>
 
     <SinglePhaseFVM
       discretization="singlePhaseTPFA"
       name="SinglePhaseFlow"
       targetRegions="{ Fracture }">
-      <NonlinearSolverParameters
-        newtonMaxIter="10"
-        newtonTol="1.0e-5"/>
-      <LinearSolverParameters
-        krylovTol="1.0e-12"
-        solverType="gmres"/>
+      <NonlinearSolverParameters newtonMaxIter="10" newtonTol="1.0e-5"/>
+      <LinearSolverParameters krylovTol="1.0e-12" solverType="gmres"/>
     </SinglePhaseFVM>
 
     <SurfaceGenerator
@@ -68,10 +56,7 @@
   </Solvers>
 
   <ElementRegions>
-    <CellElementRegion
-      name="Domain"
-      cellBlocks="{ * }"
-      materialList="{ water, rock }"/>
+    <CellElementRegion name="Domain" cellBlocks="{ * }" materialList="{ water, rock }"/>
 
     <SurfaceElementRegion
       name="Fracture"
@@ -101,8 +86,7 @@
       porosityModelName="fracturePorosity"
       permeabilityModelName="fracturePerm"/>
 
-    <NullModel
-      name="nullSolid"/>
+    <NullModel name="nullSolid"/>
 
     <PressurePorosity
       name="fracturePorosity"
@@ -110,47 +94,27 @@
       referencePressure="0.0"
       compressibility="0.0"/>
 
-    <FrictionlessContact
-      name="fractureContact"/>
+    <FrictionlessContact name="fractureContact"/>
 
-    <HydraulicApertureTable
-      name="hApertureTable"
-      apertureTableName="apertureTable"/>  
+    <HydraulicApertureTable name="hApertureTable" apertureTableName="apertureTable"/>
 
-    <ParallelPlatesPermeability
-      name="fracturePerm"/>
+    <ParallelPlatesPermeability name="fracturePerm"/>
   </Constitutive>
 
   <Outputs>
-    <Silo
-      name="siloOutput"
-      plotFileRoot="zeroToughness"
-      plotLevel="3"
-      parallelThreads="16"/>
+    <Silo name="siloOutput" plotFileRoot="zeroToughness" plotLevel="3" parallelThreads="16"/>
 
-    <Restart
-      name="sidreRestart"/>
+    <Restart name="sidreRestart"/>
 
-    <Python
-      name="pythonOutput"/>
+    <Python name="pythonOutput"/>
   </Outputs>
 
   <Geometry>
-    <Box
-      name="source"
-      xMin="{ -0.1, -0.1, -0.1 }"
-      xMax="{ 2.1, 0.1, 2.1 }"/>
-
-    <Box
-      name="perf"
-      xMin="{ -4.1, -0.1, -4.1 }"
-      xMax="{ 4.1, 0.1, 4.1 }"/>
-
-    <ThickPlane
-      name="fracturable"
-      normal="{ 0, 1, 0 }"
-      origin="{ 0, 0, 0 }"
-      thickness="0.1"/>
+    <Box name="source" xMin="{ -0.1, -0.1, -0.1 }" xMax="{ 2.1, 0.1, 2.1 }"/>
+
+    <Box name="perf" xMin="{ -4.1, -0.1, -4.1 }" xMax="{ 4.1, 0.1, 4.1 }"/>
+
+    <ThickPlane name="fracturable" normal="{ 0, 1, 0 }" origin="{ 0, 0, 0 }" thickness="0.1"/>
   </Geometry>
 
   <Functions>
@@ -162,9 +126,7 @@
 
   <Events
     maxTime="200.0">
-    <SoloEvent
-      name="preFracture"
-      target="/Solvers/SurfaceGen"/>
+    <SoloEvent name="preFracture" target="/Solvers/SurfaceGen"/>
 
     <PeriodicEvent
       name="solverApplications1"
@@ -185,23 +147,16 @@
       targetExactTimestep="0"
       target="/Outputs/siloOutput"/>
 
-    <PeriodicEvent
-      name="python"
-      cycleFrequency="5"
-      target="/Outputs/pythonOutput"/>
+    <PeriodicEvent name="python" cycleFrequency="5" target="/Outputs/pythonOutput"/>
   </Events>
 
   <NumericalMethods>
     <FiniteElements>
-      <FiniteElementSpace
-        name="FE1"
-        order="1"/>
+      <FiniteElementSpace name="FE1" order="1"/>
     </FiniteElements>
 
     <FiniteVolume>
-      <TwoPointFluxApproximation
-        name="singlePhaseTPFA"
-        meanPermCoefficient="0.8"/>
+      <TwoPointFluxApproximation name="singlePhaseTPFA" meanPermCoefficient="0.8"/>
     </FiniteVolume>
   </NumericalMethods>
 
diff --git a/examples/pygeosxExamples/parametricSurfaceMapping/parametricMesh.xml b/examples/pygeosxExamples/parametricSurfaceMapping/parametricMesh.xml
index afd6d585819..37abebebcc3 100644
--- a/examples/pygeosxExamples/parametricSurfaceMapping/parametricMesh.xml
+++ b/examples/pygeosxExamples/parametricSurfaceMapping/parametricMesh.xml
@@ -8,11 +8,8 @@
       timeIntegrationOption="QuasiStatic"
       discretization="FE1"
       targetRegions="{ Region2 }">
-      <NonlinearSolverParameters
-        newtonTol="1.0e-6"/>
-      <LinearSolverParameters
-        solverType="gmres"
-        krylovTol="1.0e-10"/>
+      <NonlinearSolverParameters newtonTol="1.0e-6"/>
+      <LinearSolverParameters solverType="gmres" krylovTol="1.0e-10"/>
     </SolidMechanicsLagrangianFEM>
   </Solvers>
 
@@ -35,10 +32,7 @@
     maxTime="1.0e-3">
     <!-- This event is applied every cycle, and overrides the
     solver time-step request -->
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1.0e-5"
-      target="/Solvers/lagsolve"/>
+    <PeriodicEvent name="solverApplications" forceDt="1.0e-5" target="/Solvers/lagsolve"/>
 
     <PeriodicEvent
       name="silo"
@@ -49,17 +43,12 @@
 
   <NumericalMethods>
     <FiniteElements>
-      <FiniteElementSpace
-        name="FE1"
-        order="1"/>
+      <FiniteElementSpace name="FE1" order="1"/>
     </FiniteElements>
   </NumericalMethods>
 
   <ElementRegions>
-    <CellElementRegion
-      name="Region2"
-      cellBlocks="{ * }"
-      materialList="{ shale }"/>
+    <CellElementRegion name="Region2" cellBlocks="{ * }" materialList="{ shale }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -97,11 +86,8 @@
   </FieldSpecifications>
 
   <Outputs>
-    <Silo
-      name="siloOutput"
-      plotLevel="3"/>
+    <Silo name="siloOutput" plotLevel="3"/>
 
-    <Restart
-      name="restartOutput"/>
+    <Restart name="restartOutput"/>
   </Outputs>
 </Problem>
diff --git a/examples/pygeosxExamples/sedovWithStressFunction/modified_sedov.xml b/examples/pygeosxExamples/sedovWithStressFunction/modified_sedov.xml
index 0e5c1e4e52c..2ad1af3f675 100644
--- a/examples/pygeosxExamples/sedovWithStressFunction/modified_sedov.xml
+++ b/examples/pygeosxExamples/sedovWithStressFunction/modified_sedov.xml
@@ -3,22 +3,17 @@
 <Problem>
   <!-- SPHINX_SEDOV_INCLUDED -->
   <Included>
-    <File
-      name="../../../inputFiles/solidMechanics/sedov.xml"/>
+    <File name="../../../inputFiles/solidMechanics/sedov.xml"/>
   </Included>
 
   <!-- SPHINX_SEDOV_INCLUDED_END -->
   <!-- SPHINX_SEDOV_EVENTS_OUTPUTS -->
   <Events>
-    <PeriodicEvent
-      name="python"
-      cycleFrequency="5"
-      target="/Outputs/pythonOutput"/>
+    <PeriodicEvent name="python" cycleFrequency="5" target="/Outputs/pythonOutput"/>
   </Events>
 
   <Outputs>
-    <Python
-      name="pythonOutput"/>
+    <Python name="pythonOutput"/>
   </Outputs>
 
   <!-- SPHINX_SEDOV_EVENTS_OUTPUTS_END -->
diff --git a/examples/sedovKernelTest.xml b/examples/sedovKernelTest.xml
index 86d6665f189..9e8fc1294b8 100644
--- a/examples/sedovKernelTest.xml
+++ b/examples/sedovKernelTest.xml
@@ -26,10 +26,7 @@
     maxTime="1.0e-2">
     <!-- This event is applied every cycle, and overrides the
     solver time-step request -->
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1.0e-5"
-      target="/Solvers/lagsolve"/>
+    <PeriodicEvent name="solverApplications" forceDt="1.0e-5" target="/Solvers/lagsolve"/>
 
     <!-- This event is applied every 5e-4s.  The targetExactTimestep
     flag allows this event to request a dt modification to match an
@@ -54,17 +51,12 @@
 
   <NumericalMethods>
     <FiniteElements>
-      <FiniteElementSpace
-        name="FE1"
-        order="1"/>
+      <FiniteElementSpace name="FE1" order="1"/>
     </FiniteElements>
   </NumericalMethods>
 
   <ElementRegions>
-    <CellElementRegion
-      name="Region2"
-      cellBlocks="{ * }"
-      materialList="{ shale }"/>
+    <CellElementRegion name="Region2" cellBlocks="{ * }" materialList="{ shale }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -121,19 +113,12 @@
   </FieldSpecifications>
 
   <Outputs>
-    <Silo
-      name="siloOutput"
-      parallelThreads="32"
-      childDirectory="sub"/>
+    <Silo name="siloOutput" parallelThreads="32" childDirectory="sub"/>
 
-    <Restart
-      name="sidreRestart"/>
+    <Restart name="sidreRestart"/>
   </Outputs>
 
   <Geometry>
-    <Box
-      name="source"
-      xMin="{ -1, -1, -1 }"
-      xMax="{ 1.1, 1.1, 1.1 }"/>
+    <Box name="source" xMin="{ -1, -1, -1 }" xMax="{ 1.1, 1.1, 1.1 }"/>
   </Geometry>
 </Problem>
diff --git a/scripts/ci_build_and_test_in_container.sh b/scripts/ci_build_and_test_in_container.sh
index 9fa8ac1086d..91c5c67cab0 100755
--- a/scripts/ci_build_and_test_in_container.sh
+++ b/scripts/ci_build_and_test_in_container.sh
@@ -198,6 +198,7 @@ Usage: $0
   --sccache-credentials credentials.json
       Basename of the json credentials file to connect to the sccache cloud cache.
   --test-code-style
+      Check C++ style (uncrustify) and XML formatting (format_xml).
   --test-documentation
   -h | --help
 EOF
@@ -494,7 +495,14 @@ or_die cd ${GEOS_BUILD_DIR}
 
 # Code style check
 if [[ "${TEST_CODE_STYLE}" = true ]]; then
-  or_die ctest --output-on-failure -R "testUncrustifyCheck"
+  # Ubuntu 24.04 system Python is PEP 668-managed. geosx_python_tools then
+  # creates a venv, which needs the stdlib venv/ensurepip modules.
+  if ! python3 -c "import venv, ensurepip" >/dev/null 2>&1; then
+    or_die apt-get update
+    or_die apt-get install -y python3-venv
+  fi
+  or_die cmake --build . --target geosx_python_tools
+  or_die ctest --output-on-failure -R "testUncrustifyCheck|testXmlFormatCheck"
   exit 0
 fi
 
@@ -547,9 +555,9 @@ if [[ "${RUN_UNIT_TESTS}" = true ]]; then
   export OMP_NUM_THREADS=1
   echo "Running unit tests with OMP_NUM_THREADS=${OMP_NUM_THREADS}."
   if [ ${HOSTNAME} == 'streak.llnl.gov' ] || [ ${HOSTNAME} == 'streak2.llnl.gov' ]; then
-    or_die ctest --output-on-failure --parallel -E "testUncrustifyCheck|testDoxygenCheck|testExternalSolvers"
+    or_die ctest --output-on-failure --parallel -E "testUncrustifyCheck|testDoxygenCheck|testXmlFormatCheck|testExternalSolvers"
   else
-    or_die ctest --output-on-failure --parallel -E "testUncrustifyCheck|testDoxygenCheck"
+    or_die ctest --output-on-failure --parallel -E "testUncrustifyCheck|testDoxygenCheck|testXmlFormatCheck"
   fi
 fi
 
diff --git a/scripts/formatXMLFiles.bash b/scripts/formatXMLFiles.bash
index 52c3c7997a3..7c9a2ffc498 100755
--- a/scripts/formatXMLFiles.bash
+++ b/scripts/formatXMLFiles.bash
@@ -1,79 +1,191 @@
-#!/bin/bash
+#!/usr/bin/env bash
+# Format GEOS XML files with the Python format_xml tool (geos-xml-tools).
+# Used by `make geosx_format_all_xml_files` and the XML formatting CI check.
+# This is not schema validation.
 
-# check if -a or --all is provided as 1st arg
+set -uo pipefail
+
+MODE=fix
 METHOD=all
-case $1 in
-    -a|--all) METHOD=all; shift
-    ;;
-    -g|--git) METHOD=git; shift
-    ;;
-    *)
-esac
-
-# nothing to do if formatting script not specified
-if [ -z "$1" ]; then
-    echo "Usage: $0 [-a|--all|-g|--git] <PYTHON_EXECUTABLE> <FORMAT_SCRIPT> [<path>...]"
-    exit
-fi
+MAX_DIFFS=20
 
-FORMAT_SCRIPT=$1; shift
-LOGFILE=xml_formatting_results.log
+usage() {
+    cat <<EOF
+Usage: $0 [--check|--fix] [-a|--all|-g|--git] <FORMAT_SCRIPT> [<path>...]
 
-# "-r" in GNU xargs omits the call if input is empty
-# OS X xargs does not support it, but does the same by default
-if [ "$(uname)" == "Darwin" ]; then
-    XARGS="xargs"
-else
-    XARGS="xargs -r"
+  --check   Fail if any XML file is malformed or not in format_xml form
+  --fix     Rewrite XML files in place (default)
+  -a, --all Search all regular *.xml files under each path (default)
+  -g, --git Search git-tracked *.xml files under each path
+EOF
+}
+
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --check)
+            MODE=check
+            shift
+            ;;
+        --fix)
+            MODE=fix
+            shift
+            ;;
+        -a|--all)
+            METHOD=all
+            shift
+            ;;
+        -g|--git)
+            METHOD=git
+            shift
+            ;;
+        -h|--help)
+            usage
+            exit 0
+            ;;
+        --)
+            shift
+            break
+            ;;
+        -*)
+            echo "Error: unknown option: $1" >&2
+            usage >&2
+            exit 1
+            ;;
+        *)
+            break
+            ;;
+    esac
+done
+
+if [[ -z "${1:-}" ]]; then
+    usage >&2
+    exit 1
 fi
 
-# check to see if the formatting script exists
-if [ ! -f $FORMAT_SCRIPT ]; then
-    >&2 echo "Error: the format_xml script was not found"
-    exit
+FORMAT_SCRIPT=$1
+shift
+
+if [[ ! -f "${FORMAT_SCRIPT}" && ! -x "${FORMAT_SCRIPT}" ]]; then
+    if ! command -v "${FORMAT_SCRIPT}" >/dev/null 2>&1; then
+        echo "Error: the format_xml script was not found: ${FORMAT_SCRIPT}" >&2
+        exit 1
+    fi
 fi
 
-# check if git is present, if needed
-if [ "$METHOD" = "git" ] && ! (hash git &> /dev/null); then
-    >&2 echo "Error: git is required when -g or --git is specified"
-    exit
+if [[ "${METHOD}" = "git" ]] && ! command -v git >/dev/null 2>&1; then
+    echo "Error: git is required when -g or --git is specified" >&2
+    exit 1
 fi
 
-abs_path ()
-{
-    if [ "$#" -gt 0 ]; then
-        realpath -s "$@"
-    fi
+# Regular files only. Do not follow directory symlinks, and do not match
+# symlink-to-file entries (examples/ has links into inputFiles/).
+list_xml_files_all() {
+    local search_path=$1
+    find -P "${search_path}" -type f -name "*.xml" -not -path "*/.*" -print
 }
 
-list_xml_files_all () 
-{
-    abs_path $(find $1 -name "*.xml" -not -path "*/\.*")
+list_xml_files_git() {
+    local search_path=$1
+    local git_root prefix tracked
+    git_root=$(cd "${search_path}" && git rev-parse --show-toplevel) || {
+        echo "Error: ${search_path} does not appear to be part of a git repository" >&2
+        return 1
+    }
+    prefix=$(cd "${search_path}" && git rev-parse --show-prefix) || return 1
+    tracked=$(git -C "${git_root}" ls-files -- "${prefix}") || {
+        echo "Error: git ls-files failed under ${search_path}" >&2
+        return 1
+    }
+    printf '%s\n' "${tracked}" | grep -e '.*[.]xml$' | sed "s|^|${git_root}/|g" || true
 }
 
-# git does not have -C flag prior to 1.8.5, so we emulate it with cd
-# this is actually the most reliable way, although not the fastest
-# run in a subprocess so as to avoid having to cd back
-list_xml_files_git ()
-{
-    local git_root=$(cd $path; git rev-parse --show-toplevel 2>/dev/null)
-    if ! [ $? -eq 0 ]; then
-        >&2 echo "Error: $path does not appear to be part of a git repository"
-        exit 1
+LOGFILE=xml_formatting_results.log
+echo -n > "${LOGFILE}"
+
+status=0
+n_checked=0
+n_invalid=0
+n_unformatted=0
+n_fixed=0
+n_diffs_shown=0
+
+process_file() {
+    local file=$1
+
+    if [[ "${MODE}" == "fix" ]]; then
+        if ! "${FORMAT_SCRIPT}" "${file}" &>> "${LOGFILE}"; then
+            echo "Invalid XML: ${file}"
+            n_invalid=$((n_invalid + 1))
+            status=1
+        else
+            n_fixed=$((n_fixed + 1))
+        fi
+        return
+    fi
+
+    # Keep a .xml suffix: format_xml may ignore extensionless temp files.
+    local tmpdir tmp
+    tmpdir="$(mktemp -d)"
+    tmp="${tmpdir}/check.xml"
+    cp "${file}" "${tmp}"
+    if ! "${FORMAT_SCRIPT}" "${tmp}" &>> "${LOGFILE}"; then
+        echo "Invalid XML: ${file}"
+        n_invalid=$((n_invalid + 1))
+        status=1
+    elif ! cmp -s "${file}" "${tmp}"; then
+        echo "Incorrect XML formatting: ${file}"
+        if [[ ${n_diffs_shown} -lt ${MAX_DIFFS} ]]; then
+            diff -u "${file}" "${tmp}" || true
+            n_diffs_shown=$((n_diffs_shown + 1))
+        fi
+        n_unformatted=$((n_unformatted + 1))
+        status=1
     fi
-    local prefix=$(cd $path; git rev-parse --show-prefix 2>/dev/null)
-    git --git-dir=$git_root/.git ls-files $prefix | grep -e .*[.]xml$ | sed "s|^|$git_root/|g"
+    rm -rf "${tmpdir}"
 }
 
-# create/nullify the log file
-echo -n > $LOGFILE
+if [[ $# -eq 0 ]]; then
+    echo "Error: no search paths given" >&2
+    exit 1
+fi
 
-# validate each path separately and write results in the log
 for path in "$@"; do
-    for file in $(list_xml_files_$METHOD $path); do
-        $FORMAT_SCRIPT $file &>> $LOGFILE
-    done
+    if [[ ! -d "${path}" ]]; then
+        echo "Error: directory not found: ${path}" >&2
+        exit 1
+    fi
+
+    list_file="$(mktemp)"
+    if ! list_xml_files_${METHOD} "${path}" > "${list_file}"; then
+        rm -f "${list_file}"
+        echo "Error: failed to list XML files under ${path}" >&2
+        exit 1
+    fi
+
+    while IFS= read -r file; do
+        [[ -z "${file}" ]] && continue
+        # examples/ contains git-tracked symlinks into inputFiles/. Skip them
+        # so this check does not rewrite or require formatting that tree.
+        [[ -L "${file}" ]] && continue
+        n_checked=$((n_checked + 1))
+        process_file "${file}"
+    done < "${list_file}"
+    rm -f "${list_file}"
 done
 
+if [[ ${n_checked} -eq 0 ]]; then
+    echo "Error: no XML files were found under: $*" >&2
+    echo "The format check must not pass when it inspected nothing." >&2
+    exit 1
+fi
 
+if [[ "${MODE}" == "fix" ]]; then
+    echo "XML formatting: ${n_checked} file(s) processed, ${n_invalid} invalid."
+else
+    echo "XML formatting: ${n_checked} file(s) checked, ${n_unformatted} incorrectly formatted, ${n_invalid} invalid."
+    if [[ ${status} -ne 0 ]]; then
+        echo "Run: make geosx_format_all_xml_files"
+    fi
+fi
 
+exit "${status}"
diff --git a/scripts/setupPythonEnvironment.bash b/scripts/setupPythonEnvironment.bash
index c25a0026f9c..d7dfbb7680d 100755
--- a/scripts/setupPythonEnvironment.bash
+++ b/scripts/setupPythonEnvironment.bash
@@ -117,6 +117,30 @@ then
     exit 1
 fi
 
+# Ubuntu 24.04+ marks the system interpreter as EXTERNALLY-MANAGED (PEP 668).
+# geosx_python_tools_test already expects packages in ${CMAKE_BINARY_DIR}/python/geosx.
+if "${PYTHON_TARGET}" -c 'import os, sysconfig; raise SystemExit(0 if os.path.isfile(os.path.join(sysconfig.get_path("stdlib"), "EXTERNALLY-MANAGED")) else 1)'
+then
+    if [[ -z "${BIN_DIR}" ]]
+    then
+        echo "The target python (${PYTHON_TARGET}) is externally managed (PEP 668)."
+        echo "Pass -b/--bin-dir so a virtual environment can be created."
+        exit 1
+    fi
+
+    VENV_DIR="$(cd "$(dirname "${BIN_DIR}")" && pwd)/python/geosx"
+    echo "The target python (${PYTHON_TARGET}) is externally managed (PEP 668)."
+    echo "Creating a virtual environment at ${VENV_DIR}"
+    mkdir -p "$(dirname "${VENV_DIR}")"
+    if ! "${PYTHON_TARGET}" -m venv "${VENV_DIR}"
+    then
+        echo "Failed to create a virtual environment at ${VENV_DIR}."
+        echo "On Debian/Ubuntu, install the python3-venv package and retry."
+        exit 1
+    fi
+    PYTHON_TARGET="${VENV_DIR}/bin/python"
+fi
+
 
 # Check for a predefined package directory
 echo "Checking for python packages..."
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 04ebce29ca6..f547d6bb3e4 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -245,8 +245,8 @@ install( FILES ${CMAKE_BINARY_DIR}/schema.xsd
 ################################
 # Add python environment setup
 ################################
-message(WARNING "Temporarily changing the geosPythonBranch to feature/remove-dndx-detj")
-set(GEOS_PYTHON_PACKAGES_BRANCH "feature/remove-dndx-detj" CACHE STRING "" FORCE)
+message(WARNING "Temporarily changing the geosPythonBranch to feature/paludettomag1/compact-xml-leaves")
+set(GEOS_PYTHON_PACKAGES_BRANCH "feature/paludettomag1/compact-xml-leaves" CACHE STRING "" FORCE)
 
 
 if ( Python3_EXECUTABLE )
@@ -282,6 +282,8 @@ if ( Python3_EXECUTABLE )
          "${CMAKE_BINARY_DIR}/bin/preprocess_xml"
          "${CMAKE_BINARY_DIR}/bin/format_xml" )
 
+    # setupPythonEnvironment.bash installs into a build-tree venv when the
+    # target interpreter is PEP 668 externally-managed (Ubuntu 24.04+).
     add_custom_command( OUTPUT ${GEOS_PYTHON_TOOLS_BINS}
                         COMMAND bash ${CMAKE_SOURCE_DIR}/../scripts/setupPythonEnvironment.bash -p ${PYTHON_POST_EXECUTABLE} -b ${CMAKE_BINARY_DIR}/bin --python-pkg-branch ${GEOS_PYTHON_PACKAGES_BRANCH}
                         WORKING_DIRECTORY ${CMAKE_BINARY_DIR} )
@@ -299,12 +301,30 @@ if ( Python3_EXECUTABLE )
                        DEPENDS geosx_python_tools
                      )
 
+    # Format / check XML with the existing Python format_xml tool.
+    # Walk the filesystem (-a), not git (-g): the CI container often cannot
+    # use the mounted checkout as root (safe.directory), and a git listing
+    # failure must not look like a clean pass.
+    # This is not a replacement for geosx_validate_all_xml_files (schema validation).
     add_custom_target( geosx_format_all_xml_files
-                       COMMAND bash ${CMAKE_SOURCE_DIR}/../scripts/formatXMLFiles.bash -g ${CMAKE_BINARY_DIR}/bin/format_xml ${CMAKE_SOURCE_DIR} ${CMAKE_SOURCE_DIR}/../examples
+                       COMMAND bash ${CMAKE_SOURCE_DIR}/../scripts/formatXMLFiles.bash -a ${CMAKE_BINARY_DIR}/bin/format_xml ${CMAKE_SOURCE_DIR} ${CMAKE_SOURCE_DIR}/../examples
                        WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
                        DEPENDS geosx_python_tools
                      )
 
+    add_custom_target( geosx_check_xml_files
+                       COMMAND bash ${CMAKE_SOURCE_DIR}/../scripts/formatXMLFiles.bash --check -a ${CMAKE_BINARY_DIR}/bin/format_xml ${CMAKE_SOURCE_DIR} ${CMAKE_SOURCE_DIR}/../examples
+                       WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
+                       DEPENDS geosx_python_tools
+                     )
+
+    set_property( TARGET geosx_check_xml_files PROPERTY EXCLUDE_FROM_ALL TRUE )
+    set_property( TARGET geosx_check_xml_files PROPERTY EXCLUDE_FROM_DEFAULT_BUILD TRUE )
+
+    add_test( NAME testXmlFormatCheck
+              COMMAND bash ${CMAKE_SOURCE_DIR}/../scripts/formatXMLFiles.bash --check -a ${CMAKE_BINARY_DIR}/bin/format_xml ${CMAKE_SOURCE_DIR} ${CMAKE_SOURCE_DIR}/../examples
+              WORKING_DIRECTORY ${CMAKE_BINARY_DIR} )
+
 else()
     message(WARNING "Building the GEOSX python tools requires Python >= 3.6.")
     message(STATUS "If you need these, try setting Python3_ROOT_DIR and/or Python3_EXECUTABLE in your host config.")
diff --git a/src/cmake/GeosxMacros.cmake b/src/cmake/GeosxMacros.cmake
index f4bb47096c7..899aba5e2ce 100644
--- a/src/cmake/GeosxMacros.cmake
+++ b/src/cmake/GeosxMacros.cmake
@@ -57,7 +57,7 @@ macro( geosx_add_code_checks )
 
     if (ENABLE_COVERAGE)
         blt_add_code_coverage_target( NAME   ${arg_PREFIX}_coverage
-                                      RUNNER ctest --progress --output-on-failure -E 'blt_gtest_smoke|blt_mpi_smoke|testUncrustifyCheck|testDoxygenCheck'
+                                      RUNNER ctest --progress --output-on-failure -E 'blt_gtest_smoke|blt_mpi_smoke|testUncrustifyCheck|testDoxygenCheck|testXmlFormatCheck'
                                       SOURCE_DIRECTORIES ${PROJECT_SOURCE_DIR}/coreComponents )
     endif()
 
diff --git a/src/coreComponents/integrationTests/constitutiveTests/testReactiveFluid.xml b/src/coreComponents/integrationTests/constitutiveTests/testReactiveFluid.xml
index d37ed605c49..2bbd8545ca8 100644
--- a/src/coreComponents/integrationTests/constitutiveTests/testReactiveFluid.xml
+++ b/src/coreComponents/integrationTests/constitutiveTests/testReactiveFluid.xml
@@ -7,16 +7,17 @@
     <ReactiveFluidDriver
       name="testDistilledWaterCO2"
       fluid="reactiveFluid"
-      feedComposition="{1e-1, 1e-1, 1e-20, 1e-20, 1e-20, 1e-20, 1e-20 }"
+      feedComposition="{ 1e-1, 1e-1, 1e-20, 1e-20, 1e-20, 1e-20, 1e-20 }"
       pressureControl="pressureFunction"
       temperatureControl="temperatureFunction"
       baseline="testDistilledWater.txt"
       steps="1"
       logLevel="1"/>
+
     <ReactiveFluidDriver
       name="testReactiveBrine"
       fluid="reactiveFluid"
-      feedComposition="{3.76e-1, 3.76e-1, 3.87e-2, 3.21e-2, 1.89, 1.65e-2, 1.09 }"
+      feedComposition="{ 3.76e-1, 3.76e-1, 3.87e-2, 3.21e-2, 1.89, 1.65e-2, 1.09 }"
       pressureControl="pressureFunction"
       temperatureControl="temperatureFunction"
       baseline="testReactiveBrine.txt"
@@ -26,12 +27,9 @@
 
   <Events
     maxTime="1">
-    <SoloEvent
-      name="testDistilledWaterCO2"
-      target="/Tasks/testDistilledWaterCO2"/>
-    <SoloEvent
-      name="testReactiveBrine"
-      target="/Tasks/testReactiveBrine"/>
+    <SoloEvent name="testDistilledWaterCO2" target="/Tasks/testDistilledWaterCO2"/>
+
+    <SoloEvent name="testReactiveBrine" target="/Tasks/testReactiveBrine"/>
   </Events>
 
   <Constitutive>
@@ -39,7 +37,7 @@
       name="reactiveFluid"
       phaseNames="{ water }"
       componentNames="{ H+, HCO3-, Ca+2, SO4-2, Cl-, Mg+2, Na+1 }"
-      componentMolarWeight="{ 18e-3, 18e-3, 18e-3, 18e-3, 18e-3, 18e-3, 18e-3}"
+      componentMolarWeight="{ 18e-3, 18e-3, 18e-3, 18e-3, 18e-3, 18e-3, 18e-3 }"
       phasePVTParaFiles="{ testPVT_data/reactiveBrinePVT.txt }"/>
   </Constitutive>
 
@@ -72,9 +70,6 @@
   </Mesh>
 
   <ElementRegions>
-    <CellElementRegion
-      name="dummy"
-      cellBlocks="{ * }"
-      materialList="{ dummy }"/>
+    <CellElementRegion name="dummy" cellBlocks="{ * }" materialList="{ dummy }"/>
   </ElementRegions>
 </Problem>
diff --git a/src/coreComponents/integrationTests/xmlTests/basic_input.xml b/src/coreComponents/integrationTests/xmlTests/basic_input.xml
index e4398019fe0..cc460bec6c6 100644
--- a/src/coreComponents/integrationTests/xmlTests/basic_input.xml
+++ b/src/coreComponents/integrationTests/xmlTests/basic_input.xml
@@ -24,30 +24,20 @@
 
   <Events
     maxTime="1.0e-3">
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1.0e-3"
-      target="/Solvers/lagsolve"/>
+    <PeriodicEvent name="solverApplications" forceDt="1.0e-3" target="/Solvers/lagsolve"/>
 
-    <PeriodicEvent
-      name="outputs"
-      target="/Outputs/siloOutput"/>
+    <PeriodicEvent name="outputs" target="/Outputs/siloOutput"/>
   </Events>
 
   <NumericalMethods>
     <FiniteElements>
-      <FiniteElementSpace
-        name="FE1"
-        order="1"/>
+      <FiniteElementSpace name="FE1" order="1"/>
     </FiniteElements>
   </NumericalMethods>
 
   <ElementRegions>
     <!-- ElementRegion name="Region1" cellBlocks="cb1"     numericalMethod="FE1" material="granite"/-->
-    <CellElementRegion
-      name="Region2"
-      cellBlocks="{ * }"
-      materialList="{ shale }"/>
+    <CellElementRegion name="Region2" cellBlocks="{ * }" materialList="{ shale }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -102,15 +92,10 @@
   </Functions>
 
   <Outputs>
-    <Silo
-      name="siloOutput"
-      childDirectory="sub"/>
+    <Silo name="siloOutput" childDirectory="sub"/>
   </Outputs>
 
   <Geometry>
-    <Box
-      name="perf"
-      xMin="{ 0, 0, 0 }"
-      xMax="{ 1, 1, 1 }"/>
+    <Box name="perf" xMin="{ 0, 0, 0 }" xMax="{ 1, 1, 1 }"/>
   </Geometry>
 </Problem>
diff --git a/src/coreComponents/integrationTests/xmlTests/include_input.xml b/src/coreComponents/integrationTests/xmlTests/include_input.xml
index 3749cd9290f..15514d80b15 100644
--- a/src/coreComponents/integrationTests/xmlTests/include_input.xml
+++ b/src/coreComponents/integrationTests/xmlTests/include_input.xml
@@ -2,16 +2,12 @@
 
 <Problem>
   <Included>
-    <File
-      name="multifile_input/mesh.xml"/>
+    <File name="multifile_input/mesh.xml"/>
 
-    <File
-      name="multifile_input/fieldspec.xml"/>
+    <File name="multifile_input/fieldspec.xml"/>
 
-    <File
-      name="multifile_input/outputs.xml"/>
+    <File name="multifile_input/outputs.xml"/>
 
-    <File
-      name="multifile_input/solver.xml"/>
+    <File name="multifile_input/solver.xml"/>
   </Included>
 </Problem>
diff --git a/src/coreComponents/integrationTests/xmlTests/multifile_input/fieldspec.xml b/src/coreComponents/integrationTests/xmlTests/multifile_input/fieldspec.xml
index 251a5993fab..9eb454bd4d3 100644
--- a/src/coreComponents/integrationTests/xmlTests/multifile_input/fieldspec.xml
+++ b/src/coreComponents/integrationTests/xmlTests/multifile_input/fieldspec.xml
@@ -2,10 +2,8 @@
 
 <Problem>
   <Included>
-    <File
-      name="boundary_conditions/constraints.xml"/>
+    <File name="boundary_conditions/constraints.xml"/>
 
-    <File
-      name="boundary_conditions/velocity.xml"/>
+    <File name="boundary_conditions/velocity.xml"/>
   </Included>
 </Problem>
diff --git a/src/coreComponents/integrationTests/xmlTests/multifile_input/mesh.xml b/src/coreComponents/integrationTests/xmlTests/multifile_input/mesh.xml
index 8b8da84f49c..45afb742fe2 100644
--- a/src/coreComponents/integrationTests/xmlTests/multifile_input/mesh.xml
+++ b/src/coreComponents/integrationTests/xmlTests/multifile_input/mesh.xml
@@ -15,9 +15,6 @@
   </Mesh>
 
   <Geometry>
-    <Box
-      name="perf"
-      xMin="{ 0, 0, 0 }"
-      xMax="{ 1, 1, 1 }"/>
+    <Box name="perf" xMin="{ 0, 0, 0 }" xMax="{ 1, 1, 1 }"/>
   </Geometry>
 </Problem>
diff --git a/src/coreComponents/integrationTests/xmlTests/multifile_input/outputs.xml b/src/coreComponents/integrationTests/xmlTests/multifile_input/outputs.xml
index 371078f74c9..9d186e357fb 100644
--- a/src/coreComponents/integrationTests/xmlTests/multifile_input/outputs.xml
+++ b/src/coreComponents/integrationTests/xmlTests/multifile_input/outputs.xml
@@ -2,14 +2,10 @@
 
 <Problem>
   <Events>
-    <PeriodicEvent
-      name="outputs"
-      target="/Outputs/siloOutput"/>
+    <PeriodicEvent name="outputs" target="/Outputs/siloOutput"/>
   </Events>
 
   <Outputs>
-    <Silo
-      name="siloOutput"
-      childDirectory="sub"/>
+    <Silo name="siloOutput" childDirectory="sub"/>
   </Outputs>
 </Problem>
diff --git a/src/coreComponents/integrationTests/xmlTests/multifile_input/solver.xml b/src/coreComponents/integrationTests/xmlTests/multifile_input/solver.xml
index 66124970c74..25972a3060b 100644
--- a/src/coreComponents/integrationTests/xmlTests/multifile_input/solver.xml
+++ b/src/coreComponents/integrationTests/xmlTests/multifile_input/solver.xml
@@ -11,26 +11,18 @@
 
   <Events
     maxTime="1.0e-3">
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1.0e-3"
-      target="/Solvers/lagsolve"/>
+    <PeriodicEvent name="solverApplications" forceDt="1.0e-3" target="/Solvers/lagsolve"/>
   </Events>
 
   <NumericalMethods>
     <FiniteElements>
-      <FiniteElementSpace
-        name="FE1"
-        order="1"/>
+      <FiniteElementSpace name="FE1" order="1"/>
     </FiniteElements>
   </NumericalMethods>
 
   <ElementRegions>
     <!-- ElementRegion name="Region1" cellBlocks="cb1"     numericalMethod="FE1" material="granite"/-->
-    <CellElementRegion
-      name="Region2"
-      cellBlocks="{ * }"
-      materialList="{ shale }"/>
+    <CellElementRegion name="Region2" cellBlocks="{ * }" materialList="{ shale }"/>
   </ElementRegions>
 
   <Constitutive>
diff --git a/src/docs/sphinx/developerGuide/Contributing/CodeStyle.rst b/src/docs/sphinx/developerGuide/Contributing/CodeStyle.rst
index 6d7f78d9b46..12861a0c9b3 100644
--- a/src/docs/sphinx/developerGuide/Contributing/CodeStyle.rst
+++ b/src/docs/sphinx/developerGuide/Contributing/CodeStyle.rst
@@ -171,6 +171,26 @@ While quite extensive, uncrustify does not enforce every example of the preferre
 In cases where uncrusitfy is unable to enforce code style, it will ignore formatting rules.
 In these cases it is acceptable to proceed with pull requests, as there is no logical recourse.
 
+XML input files
+===============
+GEOS XML files under ``src`` and ``examples`` are formatted with the Python
+``format_xml`` tool from geos-xml-tools. CI runs this as
+``testXmlFormatCheck`` alongside the uncrustify code-style job.
+The check walks those directories on disk (it does not use git) and skips
+symlinks, so it does not follow ``examples/`` links into ``inputFiles``.
+Leaf blocks that fit in 100 columns are kept on one line; longer blocks and
+parent elements stay multi-line.
+
+From the build directory:
+
+.. code-block:: bash
+
+   make geosx_check_xml_files
+   make geosx_format_all_xml_files
+
+XML formatting is not a replacement for schema validation
+(``make geosx_validate_all_xml_files``).
+
 Header Guards
 =============
 Header guard names should consist of the name `GEOS`, followed by the component name (e.g. dataRepository),
diff --git a/src/pygeosx/pyssle.xml b/src/pygeosx/pyssle.xml
index b5dd7aedee0..1624d8ed78d 100644
--- a/src/pygeosx/pyssle.xml
+++ b/src/pygeosx/pyssle.xml
@@ -26,10 +26,7 @@
     maxTime="1.0e-3">
     <!-- This event is applied every cycle, and overrides the
     solver time-step request -->
-    <PeriodicEvent
-      name="solverApplications"
-      forceDt="1.0e-5"
-      target="/Solvers/lagsolve"/>
+    <PeriodicEvent name="solverApplications" forceDt="1.0e-5" target="/Solvers/lagsolve"/>
 
     <PeriodicEvent
       name="python"
@@ -40,17 +37,12 @@
 
   <NumericalMethods>
     <FiniteElements>
-      <FiniteElementSpace
-        name="FE1"
-        order="1"/>
+      <FiniteElementSpace name="FE1" order="1"/>
     </FiniteElements>
   </NumericalMethods>
 
   <ElementRegions>
-    <CellElementRegion
-      name="Region2"
-      cellBlocks="{ * }"
-      materialList="{ shale }"/>
+    <CellElementRegion name="Region2" cellBlocks="{ * }" materialList="{ shale }"/>
   </ElementRegions>
 
   <Constitutive>
@@ -115,14 +107,10 @@
   </FieldSpecifications>
 
   <Outputs>
-    <Python
-      name="pythonOutput"/>
+    <Python name="pythonOutput"/>
   </Outputs>
 
   <Geometry>
-    <Box
-      name="source"
-      xMin="{ -1, -1, -1 }"
-      xMax="{ 1.1, 1.1, 1.1 }"/>
+    <Box name="source" xMin="{ -1, -1, -1 }" xMax="{ 1.1, 1.1, 1.1 }"/>
   </Geometry>
 </Problem>
diff --git a/src/pygeosx/unitTests/dataRepositoryTests/pygeosx_only.xml b/src/pygeosx/unitTests/dataRepositoryTests/pygeosx_only.xml
index 085db97cd7d..fcdadc9f9a0 100644
--- a/src/pygeosx/unitTests/dataRepositoryTests/pygeosx_only.xml
+++ b/src/pygeosx/unitTests/dataRepositoryTests/pygeosx_only.xml
@@ -1,17 +1,13 @@
 <?xml version="1.0" ?>
 
 <Problem>
-
-  <Events maxTime="10">
-    <PeriodicEvent
-      name="python"
-      maxEventDt="1"
-      target="/Outputs/pythonOutput"/>
+  <Events
+    maxTime="10">
+    <PeriodicEvent name="python" maxEventDt="1" target="/Outputs/pythonOutput"/>
   </Events>
 
   <Outputs>
-    <Python
-      name="pythonOutput"/>
+    <Python name="pythonOutput"/>
   </Outputs>
 
   <Mesh>
@@ -28,10 +24,6 @@
   </Mesh>
 
   <ElementRegions>
-    <CellElementRegion
-      name="dummy"
-      cellBlocks="{ * }"
-      materialList="{ dummy }"/>
+    <CellElementRegion name="dummy" cellBlocks="{ * }" materialList="{ dummy }"/>
   </ElementRegions>
-
-</Problem>
\ No newline at end of file
+</Problem>