From 3c353ff30ec2e487b564a1d0cc2c5523277fffaa Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Thu, 11 Sep 2025 00:14:55 +0200
Subject: [PATCH 1/8] fix[next]: apply cse in fuse_as_fieldop

---
 src/gt4py/next/iterator/transforms/cse.py             | 2 +-
 src/gt4py/next/iterator/transforms/fuse_as_fieldop.py | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/gt4py/next/iterator/transforms/cse.py b/src/gt4py/next/iterator/transforms/cse.py
index 2fcbd5df0d..8c98c7acc3 100644
--- a/src/gt4py/next/iterator/transforms/cse.py
+++ b/src/gt4py/next/iterator/transforms/cse.py
@@ -396,7 +396,7 @@ def extract_subexpression(
         if not eligible_ids:
             continue
 
-        expr_id = uid_generator.sequential_id()
+        expr_id = uid_generator.random_id()  # TODO: undo, but make sure we don't get collisions
         extracted[itir.Sym(id=expr_id)] = expr
         expr_ref = itir.SymRef(id=expr_id)
         for id_ in eligible_ids:
diff --git a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
index 4b3a258396..c119d5c6fd 100644
--- a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
+++ b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
@@ -25,6 +25,7 @@
     misc as ir_misc,
 )
 from gt4py.next.iterator.transforms import (
+    cse,
     fixed_point_transformation,
     inline_center_deref_lift_vars,
     inline_lambdas,
@@ -182,6 +183,7 @@ def fuse_as_fieldop(
         new_stencil, opcount_preserving=True, force_inline_lift_args=True
     )
     new_stencil = inline_lifts.InlineLifts().visit(new_stencil)
+    new_stencil = cse.CommonSubexpressionElimination.apply(new_stencil, within_stencil=True)
 
     new_node = im.as_fieldop(new_stencil, domain)(*new_args.values())
 

From 5cf6e49ef9122bcb7a08f565e06e9d2f3771ba03 Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Thu, 11 Sep 2025 07:41:09 +0200
Subject: [PATCH 2/8] fix name collision in cse

---
 src/gt4py/next/iterator/transforms/cse.py           | 13 ++++++++-----
 .../next/iterator/transforms/fuse_as_fieldop.py     |  4 +++-
 src/gt4py/next/iterator/transforms/pass_manager.py  |  5 ++++-
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/gt4py/next/iterator/transforms/cse.py b/src/gt4py/next/iterator/transforms/cse.py
index 8c98c7acc3..e5ecd7d49a 100644
--- a/src/gt4py/next/iterator/transforms/cse.py
+++ b/src/gt4py/next/iterator/transforms/cse.py
@@ -396,7 +396,7 @@ def extract_subexpression(
         if not eligible_ids:
             continue
 
-        expr_id = uid_generator.random_id()  # TODO: undo, but make sure we don't get collisions
+        expr_id = uid_generator.sequential_id(prefix="_cs")
         extracted[itir.Sym(id=expr_id)] = expr
         expr_ref = itir.SymRef(id=expr_id)
         for id_ in eligible_ids:
@@ -435,9 +435,7 @@ class CommonSubexpressionElimination(PreserveLocationVisitor, NodeTranslator):
 
     # we use one UID generator per instance such that the generated ids are
     # stable across multiple runs (required for caching to properly work)
-    uids: UIDGenerator = dataclasses.field(
-        init=False, repr=False, default_factory=lambda: UIDGenerator(prefix="_cs")
-    )
+    uids: UIDGenerator = dataclasses.field(repr=False)
 
     collect_all: bool = dataclasses.field(default=False)
 
@@ -447,6 +445,8 @@ def apply(
         node: ProgramOrExpr,
         within_stencil: bool | None = None,
         offset_provider_type: common.OffsetProviderType | None = None,
+        *,
+        uids: UIDGenerator | None = None,
     ) -> ProgramOrExpr:
         is_program = isinstance(node, itir.Program)
         if is_program:
@@ -457,11 +457,14 @@ def apply(
                 "The expression's context must be specified using `within_stencil`."
             )
 
+        if not uids:
+            uids = UIDGenerator()
+
         offset_provider_type = offset_provider_type or {}
         node = itir_type_inference.infer(
             node, offset_provider_type=offset_provider_type, allow_undeclared_symbols=not is_program
         )
-        return cls().visit(node, within_stencil=within_stencil)
+        return cls(uids=uids).visit(node, within_stencil=within_stencil)
 
     def generic_visit(self, node, **kwargs):
         if cpm.is_call_to(node, "as_fieldop"):
diff --git a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
index c119d5c6fd..1e188b620e 100644
--- a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
+++ b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
@@ -183,7 +183,9 @@ def fuse_as_fieldop(
         new_stencil, opcount_preserving=True, force_inline_lift_args=True
     )
     new_stencil = inline_lifts.InlineLifts().visit(new_stencil)
-    new_stencil = cse.CommonSubexpressionElimination.apply(new_stencil, within_stencil=True)
+    new_stencil = cse.CommonSubexpressionElimination.apply(
+        new_stencil, within_stencil=True, uids=uids
+    )
 
     new_node = im.as_fieldop(new_stencil, domain)(*new_args.values())
 
diff --git a/src/gt4py/next/iterator/transforms/pass_manager.py b/src/gt4py/next/iterator/transforms/pass_manager.py
index 9c5e154011..d4c7d2c2e5 100644
--- a/src/gt4py/next/iterator/transforms/pass_manager.py
+++ b/src/gt4py/next/iterator/transforms/pass_manager.py
@@ -65,6 +65,7 @@ def apply_common_transforms(
     tmp_uids = eve_utils.UIDGenerator(prefix="__tmp")
     mergeasfop_uids = eve_utils.UIDGenerator()
     collapse_tuple_uids = eve_utils.UIDGenerator()
+    cse_uids = eve_utils.UIDGenerator()
 
     ir = MergeLet().visit(ir)
     ir = inline_fundefs.InlineFundefs().visit(ir)
@@ -126,7 +127,9 @@ def apply_common_transforms(
 
     # breaks in test_zero_dim_tuple_arg as trivial tuple_get is not inlined
     if common_subexpression_elimination:
-        ir = CommonSubexpressionElimination.apply(ir, offset_provider_type=offset_provider_type)
+        ir = CommonSubexpressionElimination.apply(
+            ir, offset_provider_type=offset_provider_type, uids=cse_uids
+        )
         ir = MergeLet().visit(ir)
         ir = InlineLambdas.apply(ir, opcount_preserving=True)
 

From 6ffd03cc7bf57ccde10214224722fb34beb3d986 Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Thu, 11 Sep 2025 08:27:27 +0200
Subject: [PATCH 3/8] pass offset_provider_type

---
 .../iterator/transforms/fixed_point_transformation.py    | 5 ++++-
 src/gt4py/next/iterator/transforms/fuse_as_fieldop.py    | 9 ++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/gt4py/next/iterator/transforms/fixed_point_transformation.py b/src/gt4py/next/iterator/transforms/fixed_point_transformation.py
index 3818f3864a..7427450c4d 100644
--- a/src/gt4py/next/iterator/transforms/fixed_point_transformation.py
+++ b/src/gt4py/next/iterator/transforms/fixed_point_transformation.py
@@ -42,7 +42,10 @@ def fp_transform(self, node: ir.Node, **kwargs) -> ir.Node:
 
     def _post_transform(self, node: ir.Node, new_node: ir.Node) -> ir.Node:
         if self.REINFER_TYPES:
-            itir_type_inference.reinfer(new_node)
+            kwargs = {}
+            if hasattr(self, "offset_provider_type"):
+                kwargs["offset_provider_type"] = self.offset_provider_type
+            itir_type_inference.reinfer(new_node, **kwargs)
         self._preserve_annex(node, new_node)
         return new_node
 
diff --git a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
index 1e188b620e..d2f42bcf65 100644
--- a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
+++ b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
@@ -282,6 +282,7 @@ def all(self) -> FuseAsFieldOp.Transformation:
     enabled_transformations = Transformation.all()
 
     uids: eve_utils.UIDGenerator
+    offset_provider_type: common.OffsetProviderType
 
     @classmethod
     def apply(
@@ -308,9 +309,11 @@ def apply(
         if not uids:
             uids = eve_utils.UIDGenerator()
 
-        new_node = cls(uids=uids, enabled_transformations=enabled_transformations).visit(
-            node, within_set_at_expr=within_set_at_expr
-        )
+        new_node = cls(
+            uids=uids,
+            enabled_transformations=enabled_transformations,
+            offset_provider_type=offset_provider_type,
+        ).visit(node, within_set_at_expr=within_set_at_expr)
         # The `FuseAsFieldOp` pass does not fully preserve the type information yet. In particular
         # for the generated lifts this is tricky and error-prone. For simplicity, we just reinfer
         # everything here ensuring later passes can use the information.

From 5c90bcf21b379bf354e968217b4ad4edc2aab5be Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Thu, 11 Sep 2025 09:14:41 +0200
Subject: [PATCH 4/8] dont cse collect neighbors

---
 src/gt4py/next/iterator/transforms/cse.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/gt4py/next/iterator/transforms/cse.py b/src/gt4py/next/iterator/transforms/cse.py
index e5ecd7d49a..7bc986f00b 100644
--- a/src/gt4py/next/iterator/transforms/cse.py
+++ b/src/gt4py/next/iterator/transforms/cse.py
@@ -90,7 +90,7 @@ def _is_collectable_expr(node: itir.Node) -> bool:
         # do also not collect index nodes because otherwise the right hand side of SetAts becomes a let statement
         #  instead of an as_fieldop
         if cpm.is_call_to(
-            node, ("lift", "shift", "reduce", "map_", "index")
+            node, ("lift", "shift", "neighbors", "reduce", "map_", "index")
         ) or cpm.is_applied_lift(node):
             return False
         return True

From 13a85970e9bebc248a537b160ce7fcb4f6ded7c8 Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Thu, 27 Nov 2025 13:52:11 +0100
Subject: [PATCH 5/8] fix cse type reinfer

---
 .../transforms/fixed_point_transformation.py  |  5 +----
 .../iterator/transforms/fuse_as_fieldop.py    | 20 ++++++++++++++-----
 .../transforms/inline_dynamic_shifts.py       | 18 ++++++++++++++---
 .../next/iterator/transforms/pass_manager.py  |  4 ++--
 .../test_inline_dynamic_shifts.py             |  4 ++--
 5 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/src/gt4py/next/iterator/transforms/fixed_point_transformation.py b/src/gt4py/next/iterator/transforms/fixed_point_transformation.py
index 7427450c4d..3818f3864a 100644
--- a/src/gt4py/next/iterator/transforms/fixed_point_transformation.py
+++ b/src/gt4py/next/iterator/transforms/fixed_point_transformation.py
@@ -42,10 +42,7 @@ def fp_transform(self, node: ir.Node, **kwargs) -> ir.Node:
 
     def _post_transform(self, node: ir.Node, new_node: ir.Node) -> ir.Node:
         if self.REINFER_TYPES:
-            kwargs = {}
-            if hasattr(self, "offset_provider_type"):
-                kwargs["offset_provider_type"] = self.offset_provider_type
-            itir_type_inference.reinfer(new_node, **kwargs)
+            itir_type_inference.reinfer(new_node)
         self._preserve_annex(node, new_node)
         return new_node
 
diff --git a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
index d2f42bcf65..2a93f992d5 100644
--- a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
+++ b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
@@ -121,7 +121,11 @@ def _prettify_as_fieldop_args(
 
 
 def fuse_as_fieldop(
-    expr: itir.Expr, eligible_args: list[bool], *, uids: eve_utils.UIDGenerator
+    expr: itir.Expr,
+    eligible_args: list[bool],
+    *,
+    offset_provider_type: common.OffsetProviderType,
+    uids: eve_utils.UIDGenerator,
 ) -> itir.Expr:
     assert cpm.is_applied_as_fieldop(expr)
 
@@ -183,11 +187,12 @@ def fuse_as_fieldop(
         new_stencil, opcount_preserving=True, force_inline_lift_args=True
     )
     new_stencil = inline_lifts.InlineLifts().visit(new_stencil)
-    new_stencil = cse.CommonSubexpressionElimination.apply(
-        new_stencil, within_stencil=True, uids=uids
-    )
 
     new_node = im.as_fieldop(new_stencil, domain)(*new_args.values())
+    # TODO(havogt): We should investigate how to keep the tree small without having to run CSE.
+    new_node = cse.CommonSubexpressionElimination.apply(
+        new_node, within_stencil=False, uids=uids, offset_provider_type=offset_provider_type
+    )
 
     return new_node
 
@@ -398,7 +403,12 @@ def transform_fuse_as_fieldop(self, node: itir.Node, **kwargs):
             ]
             if any(eligible_els):
                 return self.visit(
-                    fuse_as_fieldop(node, eligible_els, uids=self.uids),
+                    fuse_as_fieldop(
+                        node,
+                        eligible_els,
+                        uids=self.uids,
+                        offset_provider_type=self.offset_provider_type,
+                    ),
                     **{**kwargs, "recurse": False},
                 )
         return None
diff --git a/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py b/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py
index f24326efe6..4158ffa2d9 100644
--- a/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py
+++ b/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py
@@ -12,6 +12,7 @@
 import gt4py.next.iterator.ir_utils.common_pattern_matcher as cpm
 from gt4py import eve
 from gt4py.eve import utils as eve_utils
+from gt4py.next import common
 from gt4py.next.iterator import ir as itir
 from gt4py.next.iterator.transforms import fuse_as_fieldop, inline_lambdas, trace_shifts
 from gt4py.next.iterator.transforms.symbol_ref_utils import collect_symbol_refs
@@ -34,14 +35,20 @@ def _dynamic_shift_args(node: itir.Expr) -> None | list[bool]:
 
 @dataclasses.dataclass
 class InlineDynamicShifts(eve.NodeTranslator, eve.VisitorWithSymbolTableTrait):
+    offset_provider_type: common.OffsetProviderType
     uids: eve_utils.UIDGenerator
 
     @classmethod
-    def apply(cls, node: itir.Program, uids: Optional[eve_utils.UIDGenerator] = None):
+    def apply(
+        cls,
+        node: itir.Program,
+        offset_provider_type: common.OffsetProviderType,
+        uids: Optional[eve_utils.UIDGenerator] = None,
+    ):
         if not uids:
             uids = eve_utils.UIDGenerator()
 
-        return cls(uids=uids).visit(node)
+        return cls(offset_provider_type=offset_provider_type, uids=uids).visit(node)
 
     def visit_FunCall(self, node: itir.FunCall, **kwargs):
         node = self.generic_visit(node, **kwargs)
@@ -69,6 +76,11 @@ def visit_FunCall(self, node: itir.FunCall, **kwargs):
                 for inp, dynamic_shift_arg in zip(node.args, dynamic_shift_args, strict=True)
             ]
             if any(fuse_args):
-                return fuse_as_fieldop.fuse_as_fieldop(node, fuse_args, uids=self.uids)
+                return fuse_as_fieldop.fuse_as_fieldop(
+                    node,
+                    fuse_args,
+                    uids=self.uids,
+                    offset_provider_type=self.offset_provider_type,
+                )
 
         return node
diff --git a/src/gt4py/next/iterator/transforms/pass_manager.py b/src/gt4py/next/iterator/transforms/pass_manager.py
index f3b56f7f98..01a4f6ed75 100644
--- a/src/gt4py/next/iterator/transforms/pass_manager.py
+++ b/src/gt4py/next/iterator/transforms/pass_manager.py
@@ -83,7 +83,7 @@ def apply_common_transforms(
         ir, collapse_tuple_uids=collapse_tuple_uids, offset_provider_type=offset_provider_type
     )  # domain inference does not support dead-code
     ir = inline_dynamic_shifts.InlineDynamicShifts.apply(
-        ir
+        ir, offset_provider_type=offset_provider_type
     )  # domain inference does not support dynamic offsets yet
     ir = infer_domain_ops.InferDomainOps.apply(ir)
     ir = concat_where.canonicalize_domain_argument(ir)
@@ -183,7 +183,7 @@ def apply_fieldview_transforms(
     ir = concat_where.expand_tuple_args(ir, offset_provider_type=offset_provider_type)  # type: ignore[assignment]  # always an itir.Program
     ir = dead_code_elimination.dead_code_elimination(ir, offset_provider_type=offset_provider_type)
     ir = inline_dynamic_shifts.InlineDynamicShifts.apply(
-        ir
+        ir, offset_provider_type=offset_provider_type
     )  # domain inference does not support dynamic offsets yet
 
     ir = infer_domain_ops.InferDomainOps.apply(ir)
diff --git a/tests/next_tests/unit_tests/iterator_tests/test_inline_dynamic_shifts.py b/tests/next_tests/unit_tests/iterator_tests/test_inline_dynamic_shifts.py
index ff7a761c5a..205b8447aa 100644
--- a/tests/next_tests/unit_tests/iterator_tests/test_inline_dynamic_shifts.py
+++ b/tests/next_tests/unit_tests/iterator_tests/test_inline_dynamic_shifts.py
@@ -27,7 +27,7 @@ def test_inline_dynamic_shift_as_fieldop_arg():
         )
     )("inp", "offset_field")
 
-    actual = inline_dynamic_shifts.InlineDynamicShifts.apply(testee)
+    actual = inline_dynamic_shifts.InlineDynamicShifts.apply(testee, offset_provider_type={})
     assert actual == expected
 
 
@@ -44,5 +44,5 @@ def test_inline_dynamic_shift_let_var():
         )
     )("inp", "offset_field")
 
-    actual = inline_dynamic_shifts.InlineDynamicShifts.apply(testee)
+    actual = inline_dynamic_shifts.InlineDynamicShifts.apply(testee, offset_provider_type={})
     assert actual == expected

From 0f6737cafc198e699b18f41530f5deb150fc41eb Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Thu, 27 Nov 2025 15:45:38 +0100
Subject: [PATCH 6/8] fix test references

---
 .../iterator/transforms/fuse_as_fieldop.py    | 14 +++++---
 .../transforms/inline_dynamic_shifts.py       |  1 +
 .../transforms_tests/test_cse.py              |  6 ++--
 .../transforms_tests/test_fuse_as_fieldop.py  | 32 +++++++++----------
 4 files changed, 30 insertions(+), 23 deletions(-)

diff --git a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
index 2a93f992d5..74da4c3e2d 100644
--- a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
+++ b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
@@ -125,6 +125,7 @@ def fuse_as_fieldop(
     eligible_args: list[bool],
     *,
     offset_provider_type: common.OffsetProviderType,
+    enable_cse: bool,
     uids: eve_utils.UIDGenerator,
 ) -> itir.Expr:
     assert cpm.is_applied_as_fieldop(expr)
@@ -189,10 +190,11 @@ def fuse_as_fieldop(
     new_stencil = inline_lifts.InlineLifts().visit(new_stencil)
 
     new_node = im.as_fieldop(new_stencil, domain)(*new_args.values())
-    # TODO(havogt): We should investigate how to keep the tree small without having to run CSE.
-    new_node = cse.CommonSubexpressionElimination.apply(
-        new_node, within_stencil=False, uids=uids, offset_provider_type=offset_provider_type
-    )
+    if enable_cse:
+        # TODO(havogt): We should investigate how to keep the tree small without having to run CSE.
+        new_node = cse.CommonSubexpressionElimination.apply(
+            new_node, within_stencil=False, uids=uids, offset_provider_type=offset_provider_type
+        )
 
     return new_node
 
@@ -288,6 +290,7 @@ def all(self) -> FuseAsFieldOp.Transformation:
 
     uids: eve_utils.UIDGenerator
     offset_provider_type: common.OffsetProviderType
+    enable_cse: bool  # option to disable is mainly for testing purposes
 
     @classmethod
     def apply(
@@ -299,6 +302,7 @@ def apply(
         allow_undeclared_symbols=False,
         within_set_at_expr: Optional[bool] = None,
         enabled_transformations: Optional[Transformation] = None,
+        enable_cse: bool = True,
     ):
         enabled_transformations = enabled_transformations or cls.enabled_transformations
 
@@ -318,6 +322,7 @@ def apply(
             uids=uids,
             enabled_transformations=enabled_transformations,
             offset_provider_type=offset_provider_type,
+            enable_cse=enable_cse,
         ).visit(node, within_set_at_expr=within_set_at_expr)
         # The `FuseAsFieldOp` pass does not fully preserve the type information yet. In particular
         # for the generated lifts this is tricky and error-prone. For simplicity, we just reinfer
@@ -408,6 +413,7 @@ def transform_fuse_as_fieldop(self, node: itir.Node, **kwargs):
                         eligible_els,
                         uids=self.uids,
                         offset_provider_type=self.offset_provider_type,
+                        enable_cse=self.enable_cse,
                     ),
                     **{**kwargs, "recurse": False},
                 )
diff --git a/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py b/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py
index 4158ffa2d9..924537890a 100644
--- a/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py
+++ b/src/gt4py/next/iterator/transforms/inline_dynamic_shifts.py
@@ -81,6 +81,7 @@ def visit_FunCall(self, node: itir.FunCall, **kwargs):
                     fuse_args,
                     uids=self.uids,
                     offset_provider_type=self.offset_provider_type,
+                    enable_cse=True,
                 )
 
         return node
diff --git a/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_cse.py b/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_cse.py
index f618ba409d..8bbbb80f0d 100644
--- a/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_cse.py
+++ b/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_cse.py
@@ -228,12 +228,12 @@ def is_let(node: ir.Expr):
         b = 2
         c = a + b
         d = 3
-        _let_result_1 = c + d
-        return _let_result_1 + 4
+        _cs_1 = c + d
+        return _cs_1 + 4
     """
     ).strip()
 
-    uid_gen = UIDGenerator(prefix="_let_result")
+    uid_gen = UIDGenerator()
 
     def convert_to_assignment_stmt_form(node: ir.Expr) -> tuple[list[tuple[str, ir.Expr]], ir.Expr]:
         assignment_stmts: list[tuple[str, ir.Expr]] = []
diff --git a/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_fuse_as_fieldop.py b/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_fuse_as_fieldop.py
index 58febf03c9..337c74f202 100644
--- a/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_fuse_as_fieldop.py
+++ b/tests/next_tests/unit_tests/iterator_tests/transforms_tests/test_fuse_as_fieldop.py
@@ -68,7 +68,7 @@ def test_trivial_same_arg_twice():
         d,
     )(im.ref("inp1", field_type), im.ref("inp2", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -93,7 +93,7 @@ def test_tuple_arg():
         d,
     )()
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -113,7 +113,7 @@ def test_symref_used_twice():
         d,
     )("inp1", "inp2")
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -128,7 +128,7 @@ def test_no_inline():
         d1,
     )(im.op_as_fieldop("plus", d2)(im.ref("inp1", field_type), im.ref("inp2", field_type)))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={"IOff": IDim}, allow_undeclared_symbols=True
+        testee, offset_provider_type={"IOff": IDim}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == testee
 
@@ -152,7 +152,7 @@ def test_staged_inlining():
         d,
     )(im.ref("a", field_type), im.ref("b", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -168,7 +168,7 @@ def test_make_tuple_fusion_trivial():
         d,
     )(im.ref("a", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     # simplify to remove unnecessary make_tuple call `{v[0], v[1]}(actual)`
     actual_simplified = collapse_tuple.CollapseTuple.apply(
@@ -188,7 +188,7 @@ def test_make_tuple_fusion_symref():
         d,
     )(im.ref("a", field_type), im.ref("b", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     # simplify to remove unnecessary make_tuple call
     actual_simplified = collapse_tuple.CollapseTuple.apply(
@@ -208,7 +208,7 @@ def test_make_tuple_fusion_symref_same_ref():
         d,
     )(im.ref("a", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     # simplify to remove unnecessary make_tuple call
     actual_simplified = collapse_tuple.CollapseTuple.apply(
@@ -233,7 +233,7 @@ def test_make_tuple_nested():
         d,
     )(im.ref("a", field_type), im.ref("b", field_type), im.ref("c", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     # simplify to remove unnecessary make_tuple call
     actual_simplified = collapse_tuple.CollapseTuple.apply(
@@ -275,7 +275,7 @@ def test_make_tuple_fusion_different_domains():
         )
     )
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -311,7 +311,7 @@ def test_partial_inline():
         "inp2",
     )
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={"IOff": IDim}, allow_undeclared_symbols=True
+        testee, offset_provider_type={"IOff": IDim}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -335,7 +335,7 @@ def test_chained_fusion():
         d,
     )(im.ref("inp1", field_type), im.ref("inp2", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -352,7 +352,7 @@ def test_inline_as_fieldop_with_list_dtype():
         im.lambda_("inp")(im.call(im.call("reduce")("plus", 0))(im.deref("inp"))), d
     )(im.ref("inp", list_field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -363,7 +363,7 @@ def test_inline_into_scan():
     testee = im.as_fieldop(scan, d)(im.as_fieldop("deref")(im.ref("a", field_type)))
     expected = im.as_fieldop(scan, d)(im.ref("a", field_type))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected
 
@@ -376,7 +376,7 @@ def test_no_inline_into_scan():
     scan = im.as_fieldop(scan_stencil, d)(im.ref("a", field_type))
     testee = im.as_fieldop(im.lambda_("arg")(im.deref("arg")), d)(scan)
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == testee
 
@@ -389,6 +389,6 @@ def test_opage_arg_deduplication():
         d,
     )(im.index(IDim))
     actual = fuse_as_fieldop.FuseAsFieldOp.apply(
-        testee, offset_provider_type={}, allow_undeclared_symbols=True
+        testee, offset_provider_type={}, allow_undeclared_symbols=True, enable_cse=False
     )
     assert actual == expected

From d82fd067cf26d635d043c5e8e00e93943ab6c771 Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Fri, 28 Nov 2025 13:11:40 +0100
Subject: [PATCH 7/8] make the unique ids uniquer

---
 src/gt4py/next/iterator/transforms/cse.py | 27 +++++++++++++++++------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/gt4py/next/iterator/transforms/cse.py b/src/gt4py/next/iterator/transforms/cse.py
index 7bc986f00b..6826f3977b 100644
--- a/src/gt4py/next/iterator/transforms/cse.py
+++ b/src/gt4py/next/iterator/transforms/cse.py
@@ -262,6 +262,19 @@ def visit_SymRef(
             state.used_symbol_ids.add(id(symtable[node.id]))
 
 
+def _unique_id(uid_generator: UIDGenerator) -> str:
+    """
+    Generate a unique id with '_cs' prefix using the given uid generator.
+
+    In case cse is used from a different context where the uid generator already has a prefix.
+    """
+    prefix = uid_generator.prefix or ""
+    if prefix != "_cs":
+        prefix = f"{prefix}_cs"
+
+    return uid_generator.sequential_id(prefix=prefix)
+
+
 def extract_subexpression(
     node: itir.Expr,
     predicate: Callable[[itir.Expr, int], bool],
@@ -299,10 +312,10 @@ def extract_subexpression(
         ...     expr, predicate, UIDGenerator(prefix="_subexpr")
         ... )
         >>> print(new_expr)
-        _subexpr_1 + (_subexpr_1 + z)
+        _subexpr_cs_1 + (_subexpr_cs_1 + z)
         >>> for sym, subexpr in extracted_subexprs.items():
         ...     print(f"`{sym}`: `{subexpr}`")
-        `_subexpr_1`: `x + y`
+        `_subexpr_cs_1`: `x + y`
 
         The order of the extraction can be configured using `deepest_expr_first`. By default, the nodes
         closer to the root are eliminated first:
@@ -315,10 +328,10 @@ def extract_subexpression(
         ...     expr, predicate, UIDGenerator(prefix="_subexpr"), deepest_expr_first=False
         ... )
         >>> print(new_expr)
-        _subexpr_1 + _subexpr_1
+        _subexpr_cs_1 + _subexpr_cs_1
         >>> for sym, subexpr in extracted_subexprs.items():
         ...     print(f"`{sym}`: `{subexpr}`")
-        `_subexpr_1`: `x + y + (x + y)`
+        `_subexpr_cs_1`: `x + y + (x + y)`
 
         Since `(x+y)` is a child of one of the expressions it is ignored:
 
@@ -339,10 +352,10 @@ def extract_subexpression(
         ...     deepest_expr_first=True,
         ... )
         >>> print(new_expr)
-        _subexpr_1 + _subexpr_1 + (_subexpr_1 + _subexpr_1)
+        _subexpr_cs_1 + _subexpr_cs_1 + (_subexpr_cs_1 + _subexpr_cs_1)
         >>> for sym, subexpr in extracted_subexprs.items():
         ...     print(f"`{sym}`: `{subexpr}`")
-        `_subexpr_1`: `x + y`
+        `_subexpr_cs_1`: `x + y`
 
         Note that this requires `once_only` to be set right now.
     """
@@ -396,7 +409,7 @@ def extract_subexpression(
         if not eligible_ids:
             continue
 
-        expr_id = uid_generator.sequential_id(prefix="_cs")
+        expr_id = _unique_id(uid_generator)
         extracted[itir.Sym(id=expr_id)] = expr
         expr_ref = itir.SymRef(id=expr_id)
         for id_ in eligible_ids:

From 40791356b2c0a598c6df2775c2101fd4ceada0ca Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Wed, 3 Dec 2025 10:14:35 +0100
Subject: [PATCH 8/8] add comment

---
 src/gt4py/next/iterator/transforms/cse.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/gt4py/next/iterator/transforms/cse.py b/src/gt4py/next/iterator/transforms/cse.py
index 072b3c6764..0a8fd7b59f 100644
--- a/src/gt4py/next/iterator/transforms/cse.py
+++ b/src/gt4py/next/iterator/transforms/cse.py
@@ -81,10 +81,10 @@ def _is_collectable_expr(node: itir.Node) -> bool:
     if isinstance(node, itir.FunCall):
         # do not collect (and thus deduplicate in CSE) shift(offsets…) calls. Node must still be
         #  visited, to ensure symbol dependencies are recognized correctly.
-        # do also not collect reduce nodes if they are left in the IR at this point, this may lead to
+        # do also not collect reduce, map_ and neighbors nodes if they are left in the IR at this point, this may lead to
         #  conceptual problems (other parts of the tool chain rely on the arguments being present directly
         #  on the reduce FunCall node (connectivity deduction)), as well as problems with the imperative backend
-        #  backend (single pass eager depth first visit approach)
+        #  backend (single pass eager depth first visit approach), see also https://github.com/GridTools/gt4py/issues/1795
         # do also not collect lifts or applied lifts as they become invisible to the lift inliner
         #  otherwise
         # do also not collect index nodes because otherwise the right hand side of SetAts becomes a let statement