diff --git a/pkg/repository/hf_register_cost_test.go b/pkg/repository/hf_register_cost_test.go
new file mode 100644
index 0000000..9ba537b
--- /dev/null
+++ b/pkg/repository/hf_register_cost_test.go
@@ -0,0 +1,179 @@
+// Copyright 2026 DataCanvas Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package repository
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func hfKey(repo string) RepoKey {
+	return RepoKey{Namespace: HuggingFace, RepoType: "models", Repo: repo}
+}
+
+// writeCachedRepo materialises a cached upstream repository, including the
+// paths-info subtree that makes a naive walk of the type directory expensive.
+func writeCachedRepo(t *testing.T, root, repo string) {
+	t.Helper()
+	d := Remote(hfKey(repo))
+	api := d.APIRoot(root)
+	if err := os.MkdirAll(api, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	b, err := json.MarshalIndent(d, "", "  ")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = os.WriteFile(filepath.Join(api, Marker), b, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 5; i++ {
+		p := filepath.Join(api, "paths-info", "main", "weights", strconv.Itoa(i))
+		if err = os.MkdirAll(p, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err = os.WriteFile(filepath.Join(p, "paths-info_post.json"), []byte("{}"), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+// countDirReads reports how many directories a conflict lookup opens, which is
+// the work Register performs while holding the global registration lock.
+func countDirReads(t *testing.T, root string, d Descriptor) int {
+	t.Helper()
+	opened := 0
+	current := []string{filepath.Join(root, "api", d.RepoType)}
+	parts := strings.Split(d.Repo, "/")
+	for i, part := range parts {
+		next := []string{}
+		for _, dir := range current {
+			entries, err := os.ReadDir(dir)
+			if err != nil {
+				continue
+			}
+			opened++
+			for _, e := range entries {
+				if !e.IsDir() || !strings.EqualFold(e.Name(), part) {
+					continue
+				}
+				if i < len(parts)-1 {
+					next = append(next, filepath.Join(dir, e.Name()))
+				}
+			}
+		}
+		current = next
+	}
+	return opened
+}
+
+// TestHFRegistrationCostIsIndependentOfCacheSize pins the property Register's
+// own comment promises: "registration cost stays independent of how many
+// unrelated repositories a node accumulates".
+//
+// Before listAlongRepoPath, conflictScanRoots returned api/<repoType> for the
+// HuggingFace namespace, so a first-time registration walked every cached
+// upstream repository - including each one's paths-info tree - while holding
+// the process-wide registration lock. On a mirror node with a large cache that
+// turned every uncached download into a multi-minute stall.
+func TestHFRegistrationCostIsIndependentOfCacheSize(t *testing.T) {
+	build := func(unrelated int) (string, Descriptor) {
+		root := t.TempDir()
+		for i := 0; i < unrelated; i++ {
+			writeCachedRepo(t, root, "unrelated-org-"+strconv.Itoa(i)+"/model-"+strconv.Itoa(i))
+		}
+		// A sibling must NOT be reported (it cannot overlap), while a
+		// repository nested below the candidate must still be found.
+		writeCachedRepo(t, root, "candidate-org/sibling")
+		writeCachedRepo(t, root, "candidate-org/target/variant")
+		return root, Remote(hfKey("candidate-org/target"))
+	}
+
+	smallRoot, cand := build(2)
+	largeRoot, _ := build(200)
+
+	smallDirs := countDirReads(t, smallRoot, cand)
+	largeDirs := countDirReads(t, largeRoot, cand)
+
+	smallFound, err := listConflicts(smallRoot, cand)
+	if err != nil {
+		t.Fatal(err)
+	}
+	largeFound, err := listConflicts(largeRoot, cand)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Logf("2 unrelated cached repos:   %d dirs read, %d conflict candidates", smallDirs, len(smallFound))
+	t.Logf("200 unrelated cached repos: %d dirs read, %d conflict candidates", largeDirs, len(largeFound))
+
+	if largeDirs != smallDirs {
+		t.Fatalf("registration cost grew with the cache: %d dirs at 2 repos vs %d dirs at 200", smallDirs, largeDirs)
+	}
+	if len(smallFound) != len(largeFound) {
+		t.Fatalf("conflict set changed with unrelated repositories: %d vs %d", len(smallFound), len(largeFound))
+	}
+	if len(smallFound) == 0 {
+		t.Fatal("the repository nested below the candidate was not found")
+	}
+}
+
+// TestHFRegistrationStillDetectsConflicts guards the semantics the cheaper
+// lookup must preserve: ancestors, descendants and case-folded twins all still
+// clash, and unrelated cache entries are never needed to notice them.
+func TestHFRegistrationStillDetectsConflicts(t *testing.T) {
+	for _, tc := range []struct{ name, existing, candidate string }{
+		{"ancestor", "org/model", "org/model/variant"},
+		{"descendant", "org/model/variant", "org/model"},
+		{"case-folded twin", "Org/Model", "org/model"},
+		{"parent case", "Org/other", "org/model"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			root := t.TempDir()
+			writeCachedRepo(t, root, tc.existing)
+			for i := 0; i < 20; i++ {
+				writeCachedRepo(t, root, "noise-"+strconv.Itoa(i)+"/m")
+			}
+			cand := Remote(hfKey(tc.candidate))
+			all, err := listConflicts(root, cand)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if err = registrationConflicts(root, cand, all); err == nil {
+				t.Fatalf("existing %q vs candidate %q: expected a conflict, got none (%d candidates)", tc.existing, tc.candidate, len(all))
+			}
+		})
+	}
+}
+
+// TestHFRegistrationAllowsUnrelated keeps the lookup from over-reporting: a
+// repository that merely shares a prefix string must not block registration.
+func TestHFRegistrationAllowsUnrelated(t *testing.T) {
+	root := t.TempDir()
+	writeCachedRepo(t, root, "org/model-large")
+	writeCachedRepo(t, root, "other-org/model")
+	cand := Remote(hfKey("org/model"))
+	all, err := listConflicts(root, cand)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = registrationConflicts(root, cand, all); err != nil {
+		t.Fatalf("unrelated repositories must not conflict, got: %v", err)
+	}
+}
diff --git a/pkg/repository/repository.go b/pkg/repository/repository.go
index 73abec4..5abed27 100644
--- a/pkg/repository/repository.go
+++ b/pkg/repository/repository.go
@@ -364,6 +364,21 @@ func listConflicts(root string, d Descriptor) ([]Descriptor, error) {
 				return result, err
 			}
 		}
+		if d.Namespace == HuggingFace {
+			// Only repositories lying along the candidate's own path can overlap
+			// it, so read those directory levels instead of the whole type tree.
+			found, err := listAlongRepoPath(root, repoType, d.Repo)
+			if err != nil {
+				return result, err
+			}
+			for _, old := range found {
+				if _, ok := seen[old.RepoKey]; ok {
+					continue
+				}
+				seen[old.RepoKey] = struct{}{}
+				result = append(result, old)
+			}
+		}
 		if d.Namespace != Local && d.Namespace != HuggingFace && d.Namespace != ModelScope {
 			bare, err := listBareLocalRepositories(root, repoType, d.Namespace)
 			if err != nil {
@@ -384,14 +399,122 @@ func listConflicts(root string, d Descriptor) ([]Descriptor, error) {
 // conflictScanRoots lists the directories that can hold a repository whose stored
 // path can overlap a candidate of the given repository type and namespace. The
 // paths mirror APIRoot/storagePath; a path that does not exist yields nothing.
+// listAlongRepoPath finds the repositories that can physically overlap a
+// HuggingFace candidate stored at api/<repoType>/<repo>.
+//
+// registrationConflicts only rejects a pair when one storage path is a
+// case-insensitive prefix of the other, when one repo path is an ancestor or
+// descendant of the other, or when a shared path component differs only by
+// case. Every one of those requires the existing repository to sit *along the
+// candidate's own path*, so the levels of that path are the only ones worth
+// reading. Sibling subtrees cannot overlap and are never opened, which keeps
+// registration cost proportional to the path depth and the fan-out of the
+// directories on it rather than to the number of cached repositories.
+//
+// Case variants are followed because a case-folded twin is a separate
+// directory on Linux but still a conflict under the registry contract; this
+// mirrors how listBareLocalRepositories handles namespace aliases.
+func listAlongRepoPath(root, repoType, repo string) ([]Descriptor, error) {
+	result := []Descriptor{}
+	parts := strings.Split(repo, "/")
+	// Directories to inspect at the current level, starting at the type root.
+	current := []string{filepath.Join(root, "api", repoType)}
+	for i, part := range parts {
+		next := []string{}
+		for _, dir := range current {
+			entries, err := os.ReadDir(dir)
+			if err != nil {
+				if errors.Is(err, os.ErrNotExist) {
+					continue
+				}
+				return result, err
+			}
+			for _, entry := range entries {
+				if !entry.IsDir() || !strings.EqualFold(entry.Name(), part) {
+					continue
+				}
+				child := filepath.Join(dir, entry.Name())
+				if entry.Name() != part {
+					// A component that matches only when case is folded is a
+					// separate directory on Linux, but every repository below it
+					// clashes with the candidate on "parent directory case".
+					// Collect that subtree whole, the way
+					// listBareLocalRepositories treats namespace aliases. Such
+					// directories are the rare exception, so this does not
+					// reintroduce a cache-wide walk.
+					variants, err := listIn(child, root)
+					if err != nil {
+						return result, err
+					}
+					result = append(result, variants...)
+					if d, ok := readDescriptorAt(root, child); ok {
+						result = append(result, d)
+					}
+					continue
+				}
+				// A marker on an ancestor of the candidate is an
+				// ancestor/descendant conflict; on the final component it is the
+				// candidate itself.
+				if d, ok := readDescriptorAt(root, child); ok {
+					result = append(result, d)
+				}
+				if i == len(parts)-1 {
+					// Repositories nested below the candidate also conflict.
+					// listIn prunes data subtrees, so this stays bounded by the
+					// candidate's own directory.
+					nested, err := listIn(child, root)
+					if err != nil {
+						return result, err
+					}
+					result = append(result, nested...)
+					continue
+				}
+				next = append(next, child)
+			}
+		}
+		current = next
+		if len(current) == 0 {
+			break
+		}
+	}
+	return result, nil
+}
+
+// readDescriptorAt reads the repository marker in dir, if there is a valid one.
+func readDescriptorAt(root, dir string) (Descriptor, bool) {
+	marker := filepath.Join(dir, Marker)
+	b, err := os.ReadFile(marker)
+	if err != nil {
+		return Descriptor{}, false
+	}
+	if err = SafePath(root, marker); err != nil {
+		return Descriptor{}, false
+	}
+	var d Descriptor
+	if err = json.Unmarshal(b, &d); err != nil {
+		return Descriptor{}, false
+	}
+	if err = d.Validate(); err != nil {
+		return Descriptor{}, false
+	}
+	if filepath.Clean(filepath.Join(d.APIRoot(root), Marker)) != filepath.Clean(marker) {
+		return Descriptor{}, false
+	}
+	return d, true
+}
+
 func conflictScanRoots(root, repoType, namespace string) []string {
 	switch namespace {
 	case ModelScope:
 		// modelscope/<repo>: disjoint from everything else.
 		return []string{filepath.Join(root, "api", repoType, ModelScope)}
 	case HuggingFace:
-		// <repo> directly below the type directory: disjoint from namespaces.
-		return []string{filepath.Join(root, "api", repoType)}
+		// <repo> sits directly below the type directory, so the only tree that
+		// could hold an overlap is the type directory itself - which on a mirror
+		// node holds every cached upstream repository. Walking it would make
+		// registration cost grow with the cache, so HuggingFace candidates are
+		// resolved by listAlongRepoPath instead and contribute no scan root here.
+		return nil
 	case Local:
 		// dingo-local/<repo>: only the shared upload root can hold overlaps.
 		return []string{filepath.Join(root, "api", repoType, Local)}