diff --git a/pymage/internal/cache/cache.go b/pymage/internal/cache/cache.go
index 27feecb..58d08f8 100644
--- a/pymage/internal/cache/cache.go
+++ b/pymage/internal/cache/cache.go
@@ -85,7 +85,7 @@ func (c *Cache) PutText(key, val string) error {
 	if err := tmp.Close(); err != nil {
 		return err
 	}
-	return os.Rename(tmpName, p)
+	return replaceFile(tmpName, p)
 }
 
 // Put stores the layer's compressed blob under key. Writes are atomic (temp
@@ -111,5 +111,20 @@ func (c *Cache) Put(key string, l v1.Layer) error {
 	if err := tmp.Close(); err != nil {
 		return err
 	}
-	return os.Rename(tmpName, c.path(key))
+	return replaceFile(tmpName, c.path(key))
+}
+
+// replaceFile atomically moves src onto dst. os.Rename replaces an existing
+// dst on POSIX but fails on Windows, so retry after removing dst there. The
+// store is content-addressed (or overwrites an equivalent value), so removing
+// an existing dst is safe.
+func replaceFile(src, dst string) error {
+	if err := os.Rename(src, dst); err != nil {
+		if _, statErr := os.Stat(dst); statErr == nil {
+			_ = os.Remove(dst)
+			return os.Rename(src, dst)
+		}
+		return err
+	}
+	return nil
 }
diff --git a/pymage/internal/cache/cache_test.go b/pymage/internal/cache/cache_test.go
index 59061b0..e7f6b99 100644
--- a/pymage/internal/cache/cache_test.go
+++ b/pymage/internal/cache/cache_test.go
@@ -20,6 +20,14 @@ func TestTextRoundTrip(t *testing.T) {
 	if v, ok := c.GetText("k"); !ok || v != "3.14" {
 		t.Fatalf("GetText = %q,%v; want 3.14,true", v, ok)
 	}
+	// Overwriting an existing key must succeed on all platforms (os.Rename onto
+	// an existing dest fails on Windows; replaceFile handles it).
+	if err := c.PutText("k", "3.15"); err != nil {
+		t.Fatalf("overwrite PutText: %v", err)
+	}
+	if v, ok := c.GetText("k"); !ok || v != "3.15" {
+		t.Fatalf("GetText after overwrite = %q,%v; want 3.15,true", v, ok)
+	}
 }
 
 func TestPutGetRoundTrip(t *testing.T) {
diff --git a/pymage/internal/project/project.go b/pymage/internal/project/project.go
index 107269d..5979f3b 100644
--- a/pymage/internal/project/project.go
+++ b/pymage/internal/project/project.go
@@ -75,7 +75,7 @@ func Discover(dir string) (Info, error) {
 		}
 	}
 	if info.LockFile == "" {
-		return info, fmt.Errorf("no uv.lock or requirements.txt in %s", abs)
+		return info, fmt.Errorf("no uv.lock, requirements.lock, or requirements.txt in %s", abs)
 	}
 
 	pyproject := filepath.Join(abs, "pyproject.toml")
diff --git a/pymage/internal/sbom/sbom.go b/pymage/internal/sbom/sbom.go
index 0f531e7..922e410 100644
--- a/pymage/internal/sbom/sbom.go
+++ b/pymage/internal/sbom/sbom.go
@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"sort"
 
+	"github.com/imjasonh/terraform-playground/pymage/internal/lock"
 	"github.com/imjasonh/terraform-playground/pymage/internal/wheelhouse"
 )
 
@@ -33,21 +34,25 @@ type hash struct {
 
 // Generate returns a deterministic CycloneDX JSON document for the wheels.
 func Generate(wheels []wheelhouse.ResolvedWheel) ([]byte, error) {
+	// Project names are case-insensitive (PEP 503), so sort and build PURLs from
+	// the normalized name for stable ordering and canonical pkg:pypi PURLs.
 	sorted := append([]wheelhouse.ResolvedWheel(nil), wheels...)
 	sort.Slice(sorted, func(i, j int) bool {
-		if sorted[i].Name != sorted[j].Name {
-			return sorted[i].Name < sorted[j].Name
+		ni, nj := lock.NormalizeName(sorted[i].Name), lock.NormalizeName(sorted[j].Name)
+		if ni != nj {
+			return ni < nj
 		}
 		return sorted[i].Version < sorted[j].Version
 	})
 
 	d := doc{BOMFormat: "CycloneDX", SpecVersion: "1.5", Version: 1}
 	for _, w := range sorted {
+		norm := lock.NormalizeName(w.Name)
 		d.Components = append(d.Components, component{
 			Type:    "library",
-			Name:    w.Name,
+			Name:    norm,
 			Version: w.Version,
-			PURL:    "pkg:pypi/" + w.Name + "@" + w.Version,
+			PURL:    "pkg:pypi/" + norm + "@" + w.Version,
 			Hashes:  []hash{{Alg: "SHA-256", Content: w.SHA256}},
 		})
 	}
diff --git a/pymage/internal/sbom/sbom_test.go b/pymage/internal/sbom/sbom_test.go
index 219b56a..cc602fc 100644
--- a/pymage/internal/sbom/sbom_test.go
+++ b/pymage/internal/sbom/sbom_test.go
@@ -32,3 +32,25 @@ func TestGenerateDeterministicAndSorted(t *testing.T) {
 		t.Error("components not sorted (alpha should precede beta)")
 	}
 }
+
+func TestGenerateNormalizesNames(t *testing.T) {
+	// Names are normalized (PEP 503) for canonical PURLs and stable ordering.
+	wheels := []wheelhouse.ResolvedWheel{
+		{Name: "Werkzeug", Version: "2.3.7", SHA256: "cccc"},
+		{Name: "typing_extensions", Version: "4.0", SHA256: "dddd"},
+	}
+	out, err := Generate(wheels)
+	if err != nil {
+		t.Fatal(err)
+	}
+	s := string(out)
+	if !strings.Contains(s, "pkg:pypi/werkzeug@2.3.7") {
+		t.Errorf("Werkzeug not normalized in PURL:\n%s", s)
+	}
+	if !strings.Contains(s, "pkg:pypi/typing-extensions@4.0") {
+		t.Errorf("typing_extensions not normalized in PURL:\n%s", s)
+	}
+	if strings.Contains(s, "Werkzeug") || strings.Contains(s, "typing_extensions") {
+		t.Errorf("non-normalized names present in SBOM:\n%s", s)
+	}
+}
diff --git a/pymage/internal/wheel/wheel.go b/pymage/internal/wheel/wheel.go
index 5940223..73a36ce 100644
--- a/pymage/internal/wheel/wheel.go
+++ b/pymage/internal/wheel/wheel.go
@@ -263,6 +263,12 @@ func (w *Wheel) Files(layout Layout) ([]ptar.File, error) {
 		if f.FileInfo().IsDir() {
 			continue
 		}
+		// Reject any ".." segment outright: even a member that resolves back
+		// under the prefix (e.g. "foo/../../bin/x") could escape site-packages
+		// and clobber other installed files. within() below is defense in depth.
+		if hasDotDotSegment(f.Name) {
+			return nil, fmt.Errorf("wheel: member %q contains a %q path segment", f.Name, "..")
+		}
 		dst, exec, skip := w.dest(f.Name, site, bin, prefix)
 		if skip {
 			continue
@@ -289,6 +295,17 @@ func (w *Wheel) Files(layout Layout) ([]ptar.File, error) {
 	return out, nil
 }
 
+// hasDotDotSegment reports whether any "/"- or "\"-separated segment of name is
+// "..", which would let a wheel member traverse out of its install directory.
+func hasDotDotSegment(name string) bool {
+	for _, seg := range strings.FieldsFunc(name, func(r rune) bool { return r == '/' || r == '\\' }) {
+		if seg == ".." {
+			return true
+		}
+	}
+	return false
+}
+
 // within reports whether child is parent itself or nested under it.
 func within(parent, child string) bool {
 	parent = path.Clean(parent)
diff --git a/pymage/internal/wheel/wheel_test.go b/pymage/internal/wheel/wheel_test.go
index b629caf..af9677e 100644
--- a/pymage/internal/wheel/wheel_test.go
+++ b/pymage/internal/wheel/wheel_test.go
@@ -104,6 +104,25 @@ func TestFilesRejectsEscapingMember(t *testing.T) {
 	}
 }
 
+func TestFilesRejectsInternalDotDot(t *testing.T) {
+	// A member with a ".." segment that resolves back under the prefix (here,
+	// out of site-packages into the prefix's bin) must still be rejected.
+	dir := t.TempDir()
+	path, _ := testwheel.Write(t, dir, testwheel.Spec{
+		Name:    "evil",
+		Version: "1.0",
+		Modules: map[string]string{"pkg/../../../../bin/evil": "x\n"},
+	})
+	w, err := Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = w.Close() }()
+	if _, err := w.Files(layout); err == nil {
+		t.Fatal("expected error for member with an internal '..' segment")
+	}
+}
+
 func TestFilesLayout(t *testing.T) {
 	w, err := Open(writeFixture(t))
 	if err != nil {
diff --git a/pymage/internal/wheelhouse/fetch.go b/pymage/internal/wheelhouse/fetch.go
index 3093734..d8452d9 100644
--- a/pymage/internal/wheelhouse/fetch.go
+++ b/pymage/internal/wheelhouse/fetch.go
@@ -73,6 +73,15 @@ func (c *wheelCache) put(sum string, r io.Reader) (string, error) {
 	}
 	dest := c.path(sum)
 	if err := os.Rename(tmpName, dest); err != nil {
+		// os.Rename fails on Windows if dest exists; the cache is keyed by the
+		// content hash, so an existing dest is the same wheel — replace it.
+		if _, statErr := os.Stat(dest); statErr == nil {
+			_ = os.Remove(dest)
+			if err := os.Rename(tmpName, dest); err != nil {
+				return "", err
+			}
+			return dest, nil
+		}
 		return "", err
 	}
 	return dest, nil