diff --git a/agent/prompt_builder.py b/agent/prompt_builder.py
index e7bb0ffc9..3e042f65d 100644
--- a/agent/prompt_builder.py
+++ b/agent/prompt_builder.py
@@ -654,7 +654,7 @@ def build_skills_system_prompt(
             ):
                 continue
             skills_by_category.setdefault(category, []).append(
-                (skill_name, entry.get("description", ""))
+                (frontmatter_name, entry.get("description", ""))
             )
         category_descriptions = {
             str(k): str(v)
@@ -679,7 +679,7 @@ def build_skills_system_prompt(
             ):
                 continue
             skills_by_category.setdefault(entry["category"], []).append(
-                (skill_name, entry["description"])
+                (entry["frontmatter_name"], entry["description"])
             )
 
         # Read category-level DESCRIPTION.md files
@@ -722,9 +722,10 @@ def build_skills_system_prompt(
                     continue
                 entry = _build_snapshot_entry(skill_file, ext_dir, frontmatter, desc)
                 skill_name = entry["skill_name"]
-                if skill_name in seen_skill_names:
+                frontmatter_name = entry["frontmatter_name"]
+                if frontmatter_name in seen_skill_names:
                     continue
-                if entry["frontmatter_name"] in disabled or skill_name in disabled:
+                if frontmatter_name in disabled or skill_name in disabled:
                     continue
                 if not _skill_should_show(
                     extract_skill_conditions(frontmatter),
@@ -732,9 +733,9 @@ def build_skills_system_prompt(
                     available_toolsets,
                 ):
                     continue
-                seen_skill_names.add(skill_name)
+                seen_skill_names.add(frontmatter_name)
                 skills_by_category.setdefault(entry["category"], []).append(
-                    (skill_name, entry["description"])
+                    (frontmatter_name, entry["description"])
                 )
             except Exception as e:
                 logger.debug("Error reading external skill %s: %s", skill_file, e)