diff --git a/lib/spack/llnl/util/link_tree.py b/lib/spack/llnl/util/link_tree.py
index 81c3aa09ad4..d851f06d117 100644
--- a/lib/spack/llnl/util/link_tree.py
+++ b/lib/spack/llnl/util/link_tree.py
@@ -50,9 +50,14 @@ class SourceMergeVisitor(BaseDirectoryVisitor):
     - A list of merge conflicts in dst/
     """
 
-    def __init__(self, ignore: Optional[Callable[[str], bool]] = None):
+    def __init__(
+        self, ignore: Optional[Callable[[str], bool]] = None, normalize_paths: bool = False
+    ):
         self.ignore = ignore if ignore is not None else lambda f: False
 
+        # On case-insensitive filesystems, normalize paths to detect duplications
+        self.normalize_paths = normalize_paths
+
         # When mapping <src root> to <dst root>/<projection>, we need to prepend the <projection>
         # bit to the relative path in the destination dir.
         self.projection: str = ""
@@ -71,10 +76,88 @@ def __init__(self, ignore: Optional[Callable[[str], bool]] = None):
         # and can run mkdir in order.
         self.directories: Dict[str, Tuple[str, str]] = {}
 
+        # If the visitor is configured to normalize paths, keep a map of
+        # normalized path to: original path, root directory + relative path
+        self._directories_normalized: Dict[str, Tuple[str, str, str]] = {}
+
         # Files to link. Maps dst_rel to (src_root, src_rel). This is an ordered dict, where files
         # are guaranteed to be grouped by src_root in the order they were visited.
         self.files: Dict[str, Tuple[str, str]] = {}
 
+        # If the visitor is configured to normalize paths, keep a map of
+        # normalized path to: original path, root directory + relative path
+        self._files_normalized: Dict[str, Tuple[str, str, str]] = {}
+
+    def _in_directories(self, proj_rel_path: str) -> bool:
+        """
+        Check if a path is already in the directory list
+        """
+        if self.normalize_paths:
+            return proj_rel_path.lower() in self._directories_normalized
+        else:
+            return proj_rel_path in self.directories
+
+    def _directory(self, proj_rel_path: str) -> Tuple[str, str, str]:
+        """
+        Get the directory that is mapped to a path
+        """
+        if self.normalize_paths:
+            return self._directories_normalized[proj_rel_path.lower()]
+        else:
+            return (proj_rel_path, *self.directories[proj_rel_path])
+
+    def _del_directory(self, proj_rel_path: str):
+        """
+        Remove a directory from the list of directories
+        """
+        del self.directories[proj_rel_path]
+        if self.normalize_paths:
+            del self._directories_normalized[proj_rel_path.lower()]
+
+    def _add_directory(self, proj_rel_path: str, root: str, rel_path: str):
+        """
+        Add a directory to the list of directories.
+        Also stores the normalized version for later lookups
+        """
+        self.directories[proj_rel_path] = (root, rel_path)
+        if self.normalize_paths:
+            self._directories_normalized[proj_rel_path.lower()] = (proj_rel_path, root, rel_path)
+
+    def _in_files(self, proj_rel_path: str) -> bool:
+        """
+        Check if a path is already in the files list
+        """
+        if self.normalize_paths:
+            return proj_rel_path.lower() in self._files_normalized
+        else:
+            return proj_rel_path in self.files
+
+    def _file(self, proj_rel_path: str) -> Tuple[str, str, str]:
+        """
+        Get the file that is mapped to a path
+        """
+        if self.normalize_paths:
+            return self._files_normalized[proj_rel_path.lower()]
+        else:
+            return (proj_rel_path, *self.files[proj_rel_path])
+
+    def _del_file(self, proj_rel_path: str):
+        """
+        Remove a file from the list of files
+        """
+        del self.files[proj_rel_path]
+        if self.normalize_paths:
+            del self._files_normalized[proj_rel_path.lower()]
+
+    def _add_file(self, proj_rel_path: str, root: str, rel_path: str):
+        """
+        Add a file to the list of files
+        Also stores the normalized version for later lookups
+        """
+        self.files[proj_rel_path] = (root, rel_path)
+        if self.normalize_paths:
+            self._files_normalized[proj_rel_path.lower()] = (proj_rel_path, root, rel_path)
+
     def before_visit_dir(self, root: str, rel_path: str, depth: int) -> bool:
         """
         Register a directory if dst / rel_path is not blocked by a file or ignored.
@@ -84,9 +167,9 @@ def before_visit_dir(self, root: str, rel_path: str, depth: int) -> bool:
         if self.ignore(rel_path):
             # Don't recurse when dir is ignored.
             return False
-        elif proj_rel_path in self.files:
+        elif self._in_files(proj_rel_path):
             # Can't create a dir where a file is.
-            src_a_root, src_a_relpath = self.files[proj_rel_path]
+            _, src_a_root, src_a_relpath = self._file(proj_rel_path)
             self.fatal_conflicts.append(
                 MergeConflict(
                     dst=proj_rel_path,
@@ -95,12 +178,12 @@ def before_visit_dir(self, root: str, rel_path: str, depth: int) -> bool:
                 )
             )
             return False
-        elif proj_rel_path in self.directories:
+        elif self._in_directories(proj_rel_path):
             # No new directory, carry on.
             return True
         else:
             # Register new directory.
-            self.directories[proj_rel_path] = (root, rel_path)
+            self._add_directory(proj_rel_path, root, rel_path)
             return True
 
     def before_visit_symlinked_dir(self, root: str, rel_path: str, depth: int) -> bool:
@@ -140,22 +223,22 @@ def visit_file(self, root: str, rel_path: str, depth: int, *, symlink: bool = Fa
 
         if self.ignore(rel_path):
             pass
-        elif proj_rel_path in self.directories:
+        elif self._in_directories(proj_rel_path):
             # Can't create a file where a dir is; fatal error
             self.fatal_conflicts.append(
                 MergeConflict(
                     dst=proj_rel_path,
-                    src_a=os.path.join(*self.directories[proj_rel_path]),
+                    src_a=os.path.join(*self._directory(proj_rel_path)),
                     src_b=os.path.join(root, rel_path),
                 )
             )
-        elif proj_rel_path in self.files:
+        elif self._in_files(proj_rel_path):
             # When two files project to the same path, they conflict iff they are distinct.
             # If they are the same (i.e. one links to the other), register regular files rather
             # than symlinks. The reason is that in copy-type views, we need a copy of the actual
             # file, not the symlink.
 
-            src_a = os.path.join(*self.files[proj_rel_path])
+            src_a = os.path.join(*self._file(proj_rel_path))
             src_b = os.path.join(root, rel_path)
 
             try:
@@ -173,12 +256,13 @@ def visit_file(self, root: str, rel_path: str, depth: int, *, symlink: bool = Fa
             if not symlink:
                 # Remove the link in favor of the actual file. The del is necessary to maintain the
                 # order of the files dict, which is grouped by root.
-                del self.files[proj_rel_path]
-                self.files[proj_rel_path] = (root, rel_path)
+                existing_proj_rel_path, _, _ = self._file(proj_rel_path)
+                self._del_file(existing_proj_rel_path)
+                self._add_file(proj_rel_path, root, rel_path)
 
         else:
             # Otherwise register this file to be linked.
-            self.files[proj_rel_path] = (root, rel_path)
+            self._add_file(proj_rel_path, root, rel_path)
 
     def visit_symlinked_file(self, root: str, rel_path: str, depth: int) -> None:
         # Treat symlinked files as ordinary files (without "dereferencing")
@@ -197,11 +281,11 @@ def set_projection(self, projection: str) -> None:
         path = ""
         for part in self.projection.split(os.sep):
             path = os.path.join(path, part)
-            if path not in self.files:
-                self.directories[path] = ("<projection>", path)
+            if not self._in_files(path):
+                self._add_directory(path, "<projection>", path)
             else:
                 # Can't create a dir where a file is.
-                src_a_root, src_a_relpath = self.files[path]
+                _, src_a_root, src_a_relpath = self._file(path)
                 self.fatal_conflicts.append(
                     MergeConflict(
                         dst=path,
@@ -227,8 +311,8 @@ def __init__(self, source_merge_visitor: SourceMergeVisitor):
     def before_visit_dir(self, root: str, rel_path: str, depth: int) -> bool:
         # If destination dir is a file in a src dir, add a conflict,
         # and don't traverse deeper
-        if rel_path in self.src.files:
-            src_a_root, src_a_relpath = self.src.files[rel_path]
+        if self.src._in_files(rel_path):
+            _, src_a_root, src_a_relpath = self.src._file(rel_path)
             self.src.fatal_conflicts.append(
                 MergeConflict(
                     rel_path, os.path.join(src_a_root, src_a_relpath), os.path.join(root, rel_path)
@@ -238,8 +322,9 @@ def before_visit_dir(self, root: str, rel_path: str, depth: int) -> bool:
 
         # If destination dir was also a src dir, remove the mkdir
         # action, and traverse deeper.
-        if rel_path in self.src.directories:
-            del self.src.directories[rel_path]
+        if self.src._in_directories(rel_path):
+            existing_proj_rel_path, _, _ = self.src._directory(rel_path)
+            self.src._del_directory(existing_proj_rel_path)
             return True
 
         # If the destination dir does not appear in the src dir,
@@ -252,38 +337,24 @@ def before_visit_symlinked_dir(self, root: str, rel_path: str, depth: int) -> bo
         be seen as files; we should not accidentally merge
         source dir with a symlinked dest dir.
         """
-        # Always conflict
-        if rel_path in self.src.directories:
-            src_a_root, src_a_relpath = self.src.directories[rel_path]
-            self.src.fatal_conflicts.append(
-                MergeConflict(
-                    rel_path, os.path.join(src_a_root, src_a_relpath), os.path.join(root, rel_path)
-                )
-            )
 
-        if rel_path in self.src.files:
-            src_a_root, src_a_relpath = self.src.files[rel_path]
-            self.src.fatal_conflicts.append(
-                MergeConflict(
-                    rel_path, os.path.join(src_a_root, src_a_relpath), os.path.join(root, rel_path)
-                )
-            )
+        self.visit_file(root, rel_path, depth)
 
         # Never descend into symlinked target dirs.
         return False
 
     def visit_file(self, root: str, rel_path: str, depth: int) -> None:
         # Can't merge a file if target already exists
-        if rel_path in self.src.directories:
-            src_a_root, src_a_relpath = self.src.directories[rel_path]
+        if self.src._in_directories(rel_path):
+            _, src_a_root, src_a_relpath = self.src._directory(rel_path)
             self.src.fatal_conflicts.append(
                 MergeConflict(
                     rel_path, os.path.join(src_a_root, src_a_relpath), os.path.join(root, rel_path)
                 )
             )
 
-        elif rel_path in self.src.files:
-            src_a_root, src_a_relpath = self.src.files[rel_path]
+        elif self.src._in_files(rel_path):
+            _, src_a_root, src_a_relpath = self.src._file(rel_path)
             self.src.fatal_conflicts.append(
                 MergeConflict(
                     rel_path, os.path.join(src_a_root, src_a_relpath), os.path.join(root, rel_path)
diff --git a/lib/spack/spack/filesystem_view.py b/lib/spack/spack/filesystem_view.py
index 86efd8e2f56..2267928b6d5 100644
--- a/lib/spack/spack/filesystem_view.py
+++ b/lib/spack/spack/filesystem_view.py
@@ -9,6 +9,7 @@
 import shutil
 import stat
 import sys
+import tempfile
 from typing import Callable, Dict, Optional
 
 from typing_extensions import Literal
@@ -708,7 +709,10 @@ def add_specs(self, *specs: spack.spec.Spec) -> None:
         def skip_list(file):
             return os.path.basename(file) == spack.store.STORE.layout.metadata_dir
 
-        visitor = SourceMergeVisitor(ignore=skip_list)
+        # Determine if the root is on a case-insensitive filesystem
+        normalize_paths = is_folder_on_case_insensitive_filesystem(self._root)
+
+        visitor = SourceMergeVisitor(ignore=skip_list, normalize_paths=normalize_paths)
 
         # Gather all the directories to be made and files to be linked
         for spec in specs:
@@ -884,3 +888,8 @@ def get_dependencies(specs):
 
 class ConflictingProjectionsError(SpackError):
     """Raised when a view has a projections file and is given one manually."""
+
+
+def is_folder_on_case_insensitive_filesystem(path: str) -> bool:
+    with tempfile.NamedTemporaryFile(dir=path, prefix=".sentinel") as sentinel:
+        return os.path.exists(os.path.join(path, os.path.basename(sentinel.name).upper()))
diff --git a/lib/spack/spack/test/llnl/util/link_tree.py b/lib/spack/spack/test/llnl/util/link_tree.py
index 57175aa32a8..459b40ef16c 100644
--- a/lib/spack/spack/test/llnl/util/link_tree.py
+++ b/lib/spack/spack/test/llnl/util/link_tree.py
@@ -396,3 +396,229 @@ def test_source_merge_visitor_does_deals_with_dangling_symlinks(tmp_path: pathli
 
     # The first file encountered should be listed.
     assert visitor.files == {str(tmp_path / "view" / "file"): (str(tmp_path / "dir_a"), "file")}
+
+
+def test_source_visitor_no_path_normalization(tmp_path: pathlib.Path):
+    src = str(tmp_path / "a")
+
+    a = SourceMergeVisitor(normalize_paths=False)
+    a.visit_file(src, "file", 0)
+    a.visit_file(src, "FILE", 0)
+    assert len(a.files) == 2
+    assert len(a.directories) == 0
+    assert "file" in a.files and "FILE" in a.files
+    assert len(a.file_conflicts) == 0
+
+    a = SourceMergeVisitor(normalize_paths=False)
+    a.visit_file(src, "file", 0)
+    a.before_visit_dir(src, "FILE", 0)
+    assert len(a.files) == 1
+    assert "file" in a.files and "FILE" not in a.files
+    assert len(a.directories) == 1
+    assert "FILE" in a.directories
+    assert len(a.fatal_conflicts) == 0
+    assert len(a.file_conflicts) == 0
+
+    # without normalization, order doesn't matter
+    a = SourceMergeVisitor(normalize_paths=False)
+    a.before_visit_dir(src, "FILE", 0)
+    a.visit_file(src, "file", 0)
+    assert len(a.files) == 1
+    assert "file" in a.files and "FILE" not in a.files
+    assert len(a.directories) == 1
+    assert "FILE" in a.directories
+    assert len(a.fatal_conflicts) == 0
+    assert len(a.file_conflicts) == 0
+
+    a = SourceMergeVisitor(normalize_paths=False)
+    a.before_visit_dir(src, "FILE", 0)
+    a.before_visit_dir(src, "file", 0)
+    assert len(a.files) == 0
+    assert len(a.directories) == 2
+    assert "FILE" in a.directories and "file" in a.directories
+    assert len(a.fatal_conflicts) == 0
+    assert len(a.file_conflicts) == 0
+
+
+def test_source_visitor_path_normalization(tmp_path: pathlib.Path, monkeypatch):
+    src_a = str(tmp_path / "a")
+    src_b = str(tmp_path / "b")
+
+    os.mkdir(src_a)
+    os.mkdir(src_b)
+
+    file = os.path.join(src_a, "file")
+    FILE = os.path.join(src_b, "FILE")
+
+    with open(file, "wb"):
+        pass
+
+    with open(FILE, "wb"):
+        pass
+
+    assert os.path.exists(file)
+    assert os.path.exists(FILE)
+
+    # file conflict with os.path.samefile reporting it's NOT the same file
+    a = SourceMergeVisitor(normalize_paths=True)
+    a.visit_file(src_a, "file", 0)
+    a.visit_file(src_b, "FILE", 0)
+    assert a.files
+    assert len(a.files) == 1
+    # first file wins
+    assert "file" in a.files
+    # this is a conflict since the files are reported to be distinct
+    assert len(a.file_conflicts) == 1
+    assert "FILE" in [c.dst for c in a.file_conflicts]
+
+    os.remove(FILE)
+    os.link(file, FILE)
+
+    assert os.path.exists(file)
+    assert os.path.exists(FILE)
+    assert os.path.samefile(file, FILE)
+
+    # file conflict with os.path.samefile reporting it's the same file
+    a = SourceMergeVisitor(normalize_paths=True)
+    a.visit_file(src_a, "file", 0)
+    a.visit_file(src_b, "FILE", 0)
+    assert a.files
+    assert len(a.files) == 1
+    # second file wins
+    assert "FILE" in a.files
+    # not a conflict
+    assert len(a.file_conflicts) == 0
+
+    a = SourceMergeVisitor(normalize_paths=True)
+    a.visit_file(src_a, "file", 0)
+    a.before_visit_dir(src_a, "FILE", 0)
+    assert a.files
+    assert len(a.files) == 1
+    assert "file" in a.files
+    assert len(a.directories) == 0
+    assert len(a.fatal_conflicts) == 1
+    conflicts = [c.dst for c in a.fatal_conflicts]
+    assert "FILE" in conflicts
+
+    a = SourceMergeVisitor(normalize_paths=True)
+    a.before_visit_dir(src_a, "FILE", 0)
+    a.visit_file(src_a, "file", 0)
+    assert len(a.directories) == 1
+    assert "FILE" in a.directories
+    assert len(a.files) == 0
+    assert len(a.fatal_conflicts) == 1
+    conflicts = [c.dst for c in a.fatal_conflicts]
+    assert "file" in conflicts
+
+    a = SourceMergeVisitor(normalize_paths=True)
+    a.before_visit_dir(src_a, "FILE", 0)
+    a.before_visit_dir(src_a, "file", 0)
+    assert len(a.directories) == 1
+    # first dir wins
+    assert "FILE" in a.directories
+    assert len(a.files) == 0
+    assert len(a.fatal_conflicts) == 0
+
+
+def test_destination_visitor_no_path_normalization(tmp_path: pathlib.Path):
+    src = str(tmp_path / "a")
+    dest = str(tmp_path / "b")
+
+    src_visitor = SourceMergeVisitor(normalize_paths=False)
+    src_visitor.visit_file(src, "file", 0)
+    assert len(src_visitor.files) == 1
+    assert len(src_visitor.directories) == 0
+    assert "file" in src_visitor.files
+
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.visit_file(dest, "FILE", 0)
+    # not a conflict, since normalization is off
+    assert len(dest_visitor.src.files) == 1
+    assert len(dest_visitor.src.directories) == 0
+    assert "file" in dest_visitor.src.files
+    assert len(dest_visitor.src.fatal_conflicts) == 0
+    assert len(dest_visitor.src.file_conflicts) == 0
+
+    src_visitor = SourceMergeVisitor(normalize_paths=False)
+    src_visitor.visit_file(src, "file", 0)
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.before_visit_dir(dest, "FILE", 0)
+    assert len(dest_visitor.src.files) == 1
+    assert "file" in dest_visitor.src.files
+    assert len(dest_visitor.src.directories) == 0
+    assert len(dest_visitor.src.fatal_conflicts) == 0
+    assert len(dest_visitor.src.file_conflicts) == 0
+
+    # not insensitive, order does not matter
+    src_visitor = SourceMergeVisitor(normalize_paths=False)
+    src_visitor.before_visit_dir(src, "file", 0)
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.visit_file(dest, "FILE", 0)
+    assert len(dest_visitor.src.files) == 0
+    assert len(dest_visitor.src.directories) == 1
+    assert "file" in dest_visitor.src.directories
+    assert len(dest_visitor.src.fatal_conflicts) == 0
+    assert len(dest_visitor.src.file_conflicts) == 0
+
+    src_visitor = SourceMergeVisitor(normalize_paths=False)
+    src_visitor.before_visit_dir(src, "file", 0)
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.before_visit_dir(dest, "FILE", 0)
+    assert len(dest_visitor.src.files) == 0
+    assert len(dest_visitor.src.directories) == 1
+    assert "file" in dest_visitor.src.directories
+    assert len(dest_visitor.src.fatal_conflicts) == 0
+    assert len(dest_visitor.src.file_conflicts) == 0
+
+
+def test_destination_visitor_path_normalization(tmp_path: pathlib.Path):
+    src = str(tmp_path / "a")
+    dest = str(tmp_path / "b")
+
+    src_visitor = SourceMergeVisitor(normalize_paths=True)
+    src_visitor.visit_file(src, "file", 0)
+    assert len(src_visitor.files) == 1
+    assert len(src_visitor.directories) == 0
+    assert "file" in src_visitor.files
+
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.visit_file(dest, "FILE", 0)
+    assert len(dest_visitor.src.files) == 1
+    assert len(dest_visitor.src.directories) == 0
+    assert "file" in dest_visitor.src.files
+    assert len(dest_visitor.src.fatal_conflicts) == 1
+    assert "FILE" in [c.dst for c in dest_visitor.src.fatal_conflicts]
+    assert len(dest_visitor.src.file_conflicts) == 0
+
+    src_visitor = SourceMergeVisitor(normalize_paths=True)
+    src_visitor.visit_file(src, "file", 0)
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.before_visit_dir(dest, "FILE", 0)
+    assert len(dest_visitor.src.files) == 1
+    assert "file" in dest_visitor.src.files
+    assert len(dest_visitor.src.directories) == 0
+    assert len(dest_visitor.src.fatal_conflicts) == 1
+    assert "FILE" in [c.dst for c in dest_visitor.src.fatal_conflicts]
+    assert len(dest_visitor.src.file_conflicts) == 0
+
+    src_visitor = SourceMergeVisitor(normalize_paths=True)
+    src_visitor.before_visit_dir(src, "file", 0)
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.visit_file(dest, "FILE", 0)
+    assert len(dest_visitor.src.files) == 0
+    assert len(dest_visitor.src.directories) == 1
+    assert "file" in dest_visitor.src.directories
+    assert len(dest_visitor.src.fatal_conflicts) == 1
+    assert "FILE" in [c.dst for c in dest_visitor.src.fatal_conflicts]
+    assert len(dest_visitor.src.file_conflicts) == 0
+
+    src_visitor = SourceMergeVisitor(normalize_paths=True)
+    src_visitor.before_visit_dir(src, "file", 0)
+    dest_visitor = DestinationMergeVisitor(src_visitor)
+    dest_visitor.before_visit_dir(dest, "FILE", 0)
+    assert len(dest_visitor.src.files) == 0
+    # this removes the mkdir action, no directory left over
+    assert len(dest_visitor.src.directories) == 0
+    # but it's also not a conflict
+    assert len(dest_visitor.src.fatal_conflicts) == 0
+    assert len(dest_visitor.src.file_conflicts) == 0