diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 5c7e590f41..a9d51f4622 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -60,12 +60,12 @@ jobs:
 
       - name: Build Firedrake
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           cd ..
           # Linting should ignore unquoted shell variable $COMPLEX
           # shellcheck disable=SC2086
           ./firedrake/scripts/firedrake-install \
             $COMPLEX \
-            --honour-petsc-dir \
             --mpicc="$MPICH_DIR"/mpicc \
             --mpicxx="$MPICH_DIR"/mpicxx \
             --mpif90="$MPICH_DIR"/mpif90 \
@@ -88,6 +88,8 @@ jobs:
             --install defcon \
             --install gadopt \
             --install asQ \
+            --package-branch petsc dham/merge_upstream \
+            --package-branch slepc connorjward/merge-upstream \
             || (cat firedrake-install.log && /bin/false)
 
       - name: Install test dependencies
@@ -104,6 +106,7 @@ jobs:
         run: |
           : # Use pytest-xdist here so we can have a single collated output (not possible
           : # for parallel tests)
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 1 1 "-n 12 $EXTRA_PYTEST_ARGS --junit-xml=firedrake1_{#}.xml"
 
@@ -111,42 +114,49 @@ jobs:
         # Run even if earlier tests failed
         if: ${{ success() || steps.build.conclusion == 'success' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 2 6 "$EXTRA_PYTEST_ARGS --junit-xml=firedrake2_{#}.xml"
 
       - name: Run tests (nprocs = 3)
         if: ${{ success() || steps.build.conclusion == 'success' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 3 4 "$EXTRA_PYTEST_ARGS --junit-xml=firedrake3_{#}.xml"
 
       - name: Run tests (nprocs = 4)
         if: ${{ success() || steps.build.conclusion == 'success' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 4 3 "$EXTRA_PYTEST_ARGS --junit-xml=firedrake4_{#}.xml"
 
       - name: Run tests (nprocs = 5)
         if: ${{ success() || steps.build.conclusion == 'success' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 5 2 "$EXTRA_PYTEST_ARGS --junit-xml=firedrake5_{#}.xml"
 
       - name: Run tests (nprocs = 6)
         if: ${{ success() || steps.build.conclusion == 'success' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 6 2 "$EXTRA_PYTEST_ARGS --junit-xml=firedrake6_{#}.xml"
 
       - name: Run tests (nprocs = 7)
         if: ${{ success() || steps.build.conclusion == 'success' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 7 1 "$EXTRA_PYTEST_ARGS --junit-xml=firedrake7_{#}.xml"
 
       - name: Run tests (nprocs = 8)
         if: ${{ success() || steps.build.conclusion == 'success' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           firedrake-run-split-tests 8 1 "$EXTRA_PYTEST_ARGS --junit-xml=firedrake8_{#}.xml"
 
diff --git a/firedrake/cython/dmcommon.pyx b/firedrake/cython/dmcommon.pyx
index b5e0777dfe..b67c0c21ec 100644
--- a/firedrake/cython/dmcommon.pyx
+++ b/firedrake/cython/dmcommon.pyx
@@ -2120,6 +2120,8 @@ def mark_entity_classes_using_cell_dm(PETSc.DM swarm):
         PetscInt nswarmCells, swarmCell, blocksize
         PetscInt *swarmParentCells = NULL
         PetscDataType ctype = PETSC_DATATYPE_UNKNOWN
+        const char *cellid = NULL
+        PETSc.PetscDMSwarmCellDM celldm
 
     plex = swarm.getCellDM()
     get_height_stratum(plex.dm, 0, &cStart, &cEnd)
@@ -2145,14 +2147,16 @@ def mark_entity_classes_using_cell_dm(PETSc.DM swarm):
     for ilabel, op2class in enumerate([b"pyop2_core", b"pyop2_owned", b"pyop2_ghost"]):
         CHKERR(DMCreateLabel(swarm.dm, op2class))
         CHKERR(DMGetLabel(swarm.dm, op2class, &swarm_labels[ilabel]))
-    CHKERR(DMSwarmGetField(swarm.dm, b"DMSwarm_cellid", &blocksize, &ctype, <void**>&swarmParentCells))
+    CHKERR(DMSwarmGetCellDMActive(swarm.dm, &celldm))
+    CHKERR(DMSwarmCellDMGetCellID(celldm, &cellid))
+    CHKERR(DMSwarmGetField(swarm.dm, cellid, &blocksize, &ctype, <void**> &swarmParentCells))
     assert ctype == PETSC_INT
     assert blocksize == 1
     CHKERR(DMSwarmGetLocalSize(swarm.dm, &nswarmCells))
     for swarmCell in range(nswarmCells):
         plex_cell_class = plex_cell_classes[swarmParentCells[swarmCell] - cStart]
         CHKERR(DMLabelSetValue(swarm_labels[plex_cell_class], swarmCell, label_value))
-    CHKERR(DMSwarmRestoreField(swarm.dm, b"DMSwarm_cellid", &blocksize, &ctype, <void**>&swarmParentCells))
+    CHKERR(DMSwarmRestoreField(swarm.dm, cellid, &blocksize, &ctype, <void**> &swarmParentCells))
     CHKERR(PetscFree(plex_cell_classes))
 
 
diff --git a/firedrake/cython/petschdr.pxi b/firedrake/cython/petschdr.pxi
index 9a0bff609d..750a3c3714 100644
--- a/firedrake/cython/petschdr.pxi
+++ b/firedrake/cython/petschdr.pxi
@@ -79,6 +79,8 @@ cdef extern from "petscdm.h" nogil:
 cdef extern from "petscdmswarm.h" nogil:
     int DMSwarmGetLocalSize(PETSc.PetscDM,PetscInt*)
     int DMSwarmGetCellDM(PETSc.PetscDM, PETSc.PetscDM*)
+    int DMSwarmGetCellDMActive(PETSc.PetscDM, PETSc.PetscDMSwarmCellDM*)
+    int DMSwarmCellDMGetCellID(PETSc.PetscDMSwarmCellDM, const char *[])
     int DMSwarmGetField(PETSc.PetscDM,const char[],PetscInt*,PetscDataType*,void**)
     int DMSwarmRestoreField(PETSc.PetscDM,const char[],PetscInt*,PetscDataType*,void**)
 
diff --git a/firedrake/mesh.py b/firedrake/mesh.py
index 8a0f8ec8a9..30e24a1cd8 100644
--- a/firedrake/mesh.py
+++ b/firedrake/mesh.py
@@ -1966,14 +1966,15 @@ def _renumber_entities(self, reorder):
         if reorder:
             swarm = self.topology_dm
             parent = self._parent_mesh.topology_dm
-            swarm_parent_cell_nums = swarm.getField("DMSwarm_cellid").ravel()
+            cell_id_name = swarm.getCellDMActive().getCellID()
+            swarm_parent_cell_nums = swarm.getField(cell_id_name).ravel()
             parent_renum = self._parent_mesh._dm_renumbering.getIndices()
             pStart, _ = parent.getChart()
             parent_renum_inv = np.empty_like(parent_renum)
             parent_renum_inv[parent_renum - pStart] = np.arange(len(parent_renum))
             # Use kind = 'stable' to make the ordering deterministic.
             perm = np.argsort(parent_renum_inv[swarm_parent_cell_nums - pStart], kind='stable').astype(IntType)
-            swarm.restoreField("DMSwarm_cellid")
+            swarm.restoreField(cell_id_name)
             perm_is = PETSc.IS().create(comm=swarm.comm)
             perm_is.setType("general")
             perm_is.setIndices(perm)
@@ -3557,11 +3558,9 @@ def _pic_swarm_in_mesh(
         #. ``parentcellextrusionheight`` which contains the extrusion height of
             the immersed vertex in the parent mesh cell.
 
-        Another three are required for proper functioning of the DMSwarm:
+        Another two are required for proper functioning of the DMSwarm:
 
         #. ``DMSwarmPIC_coor`` which contains the coordinates of the point.
-        #. ``DMSwarm_cellid`` the DMPlex cell within which the DMSwarm point is
-           located.
         #. ``DMSwarm_rank``: the MPI rank which owns the DMSwarm point.
 
     .. note::
@@ -3794,7 +3793,6 @@ def _dmswarm_create(
     # These are created by default for a PIC DMSwarm
     default_fields = [
         ("DMSwarmPIC_coor", gdim, RealType),
-        ("DMSwarm_cellid", 1, IntType),
         ("DMSwarm_rank", 1, IntType),
     ]
 
@@ -3853,12 +3851,6 @@ def _dmswarm_create(
     # Set to Particle In Cell (PIC) type
     if not isinstance(plex, PETSc.DMSwarm):
         swarm.setType(PETSc.DMSwarm.Type.PIC)
-    else:
-        # This doesn't work where we embed a DMSwarm in a DMSwarm, instead
-        # we register some default fields manually
-        for name, size, dtype in default_fields:
-            if name == "DMSwarmPIC_coor" or name == "DMSwarm_cellid":
-                swarm.registerField(name, size, dtype=dtype)
 
     # Register any fields
     for name, size, dtype in swarm.default_extra_fields + swarm.other_fields:
@@ -3872,14 +3864,15 @@ def _dmswarm_create(
     # Add point coordinates. This amounts to our own implementation of
     # DMSwarmSetPointCoordinates because Firedrake's mesh coordinate model
     # doesn't always exactly coincide with that of DMPlex: in most cases the
-    # plex_parent_cell_nums (DMSwarm_cellid field) and parent_cell_nums
-    # (parentcellnum field), the latter being the numbering used by firedrake,
-    # refer fundamentally to the same cells. For extruded meshes the DMPlex
-    # dimension is based on the topological dimension of the base mesh.
+    # plex_parent_cell_nums and parent_cell_nums (parentcellnum field), the
+    # latter being the numbering used by firedrake, refer fundamentally to the
+    # same cells. For extruded meshes the DMPlex dimension is based on the
+    # topological dimension of the base mesh.
 
     # NOTE ensure that swarm.restoreField is called for each field too!
     swarm_coords = swarm.getField("DMSwarmPIC_coor").reshape((num_vertices, gdim))
-    swarm_parent_cell_nums = swarm.getField("DMSwarm_cellid").ravel()
+    cell_id_name = swarm.getCellDMActive().getCellID()
+    swarm_parent_cell_nums = swarm.getField(cell_id_name).ravel()
     field_parent_cell_nums = swarm.getField("parentcellnum").ravel()
     field_reference_coords = swarm.getField("refcoord").reshape((num_vertices, tdim))
     field_global_index = swarm.getField("globalindex").ravel()
@@ -3903,7 +3896,7 @@ def _dmswarm_create(
     swarm.restoreField("refcoord")
     swarm.restoreField("parentcellnum")
     swarm.restoreField("DMSwarmPIC_coor")
-    swarm.restoreField("DMSwarm_cellid")
+    swarm.restoreField(cell_id_name)
 
     if extruded:
         field_base_parent_cell_nums = swarm.getField("parentcellbasenum").ravel()
diff --git a/tests/firedrake/vertexonly/test_swarm.py b/tests/firedrake/vertexonly/test_swarm.py
index d3f5680041..4bd5cde939 100644
--- a/tests/firedrake/vertexonly/test_swarm.py
+++ b/tests/firedrake/vertexonly/test_swarm.py
@@ -218,8 +218,9 @@ def test_pic_swarm_in_mesh(parentmesh, redundant, exclude_halos):
     nptslocal = len(localpointcoords)
     nptsglobal = MPI.COMM_WORLD.allreduce(nptslocal, op=MPI.SUM)
     # Get parent PETSc cell indices on current MPI rank
-    localparentcellindices = np.copy(swarm.getField("DMSwarm_cellid").ravel())
-    swarm.restoreField("DMSwarm_cellid")
+    cell_id = swarm.getCellDMActive().getCellID()
+    localparentcellindices = np.copy(swarm.getField(cell_id).ravel())
+    swarm.restoreField(cell_id)
 
     # also get the global coordinate numbering
     globalindices = np.copy(swarm.getField("globalindex").ravel())
@@ -242,7 +243,6 @@ def test_pic_swarm_in_mesh(parentmesh, redundant, exclude_halos):
     # Check swarm fields are correct
     default_fields = [
         ("DMSwarmPIC_coor", parentmesh.geometric_dimension(), RealType),
-        ("DMSwarm_cellid", 1, IntType),
         ("DMSwarm_rank", 1, IntType),
     ]
     default_extra_fields = [
@@ -378,8 +378,9 @@ def test_pic_swarm_in_mesh(parentmesh, redundant, exclude_halos):
     ):
         swarm.setPointCoordinates(localpointcoords, redundant=False,
                                   mode=PETSc.InsertMode.INSERT_VALUES)
-        petsclocalparentcellindices = np.copy(swarm.getField("DMSwarm_cellid").ravel())
-        swarm.restoreField("DMSwarm_cellid")
+        cell_id = swarm.getCellDMActive().getCellID()
+        petsclocalparentcellindices = np.copy(swarm.getField(cell_id).ravel())
+        swarm.restoreField(cell_id)
         if exclude_halos:
             assert np.all(petsclocalparentcellindices == localparentcellindices)
         elif parentmesh.comm.size > 1: