diff --git a/hermes_cli/prompt_size.py b/hermes_cli/prompt_size.py
index 30c212a429ceb..0629b9346df3c 100644
--- a/hermes_cli/prompt_size.py
+++ b/hermes_cli/prompt_size.py
@@ -252,8 +252,9 @@ def compute_prompt_breakdown(platform: str = "cli") -> Dict[str, Any]:
     volatile = parts.get("volatile", "")
 
     # Skills index — the <available_skills> block (the largest single block
-    # when many skills are installed). Measured inside the stable tier.
-    skills_match = _SKILLS_BLOCK_RE.search(stable)
+    # when many skills are installed). Lives in the volatile tier (moved from
+    # stable so skill edits don't invalidate the cached identity prefix).
+    skills_match = _SKILLS_BLOCK_RE.search(volatile) or _SKILLS_BLOCK_RE.search(stable)
     skills_index = skills_match.group(0) if skills_match else ""
 
     # Memory + user profile live in the volatile tier. We re-derive their