diff --git a/TODO.md b/TODO.md
index 3150ac0..f233d2d 100644
--- a/TODO.md
+++ b/TODO.md
@@ -7,7 +7,7 @@
 - [ ] Check semantic retrieval ownership and links before copying or deleting its directory. An existing owned runtime's source files are overwritten without comparing recorded hashes; a replaced target symlink is followed on enable, and disabling the last client removes foreign files inside the runtime. (`scripts/lib/semantic-retrieval.py:82`, `scripts/lib/semantic-retrieval.py:100`)
 - [ ] Preserve pre-existing MCPorter server entries. `ensure_mcporter()` adds a server and claims ownership without checking existing configuration; if the add succeeds for an existing name, a later removal deletes that user's entry. (`scripts/lib/managed-extensions.py:395`, `scripts/lib/managed-extensions.py:263`)
 - [ ] Preserve pre-existing global CLI packages. `ensure_cli()` and `ensure_qmd()` install and claim npm packages without checking whether they were already installed; later removal can uninstall a user's package. (`scripts/lib/managed-extensions.py:342`, `scripts/lib/managed-extensions.py:378`)
-- [ ] Fetch skill archives by an immutable commit and record that same commit. The archive uses GitHub `HEAD`, while `resolvedRevision` comes from a separate later request, so the recorded revision may not identify the installed payload. (`scripts/lib/managed-extensions.py:94`, `scripts/lib/managed-extensions.py:140`, `scripts/lib/managed-extensions.py:409`)
+- [x] Fetch skill archives by an immutable commit and record that same commit. The archive uses GitHub `HEAD`, while `resolvedRevision` comes from a separate later request, so the recorded revision may not identify the installed payload. (`scripts/lib/managed-extensions.py:94`, `scripts/lib/managed-extensions.py:140`, `scripts/lib/managed-extensions.py:409`)
 - [ ] Protect the semantic retrieval daemon's IPC protocol. It uses a hardcoded authentication key and `multiprocessing.connection.recv()`, which deserializes messages; a process that can reach its socket or pipe can submit arbitrary roots and potentially crafted objects. Use a private per-install credential and a non-pickle wire format, or restrict the endpoint to the current user. (`shared/retrieval/server.py:47`, `shared/retrieval/server.py:306`, `shared/retrieval/server.py:314`)
 - [x] Write semantic retrieval ownership state atomically. `save_state()` replaces the JSON with a direct write, unlike the extension and selection ledgers; interruption can leave it unreadable and block later reconciliation. (`scripts/lib/semantic-retrieval.py:63`)
 
diff --git a/scripts/lib/managed-extensions.py b/scripts/lib/managed-extensions.py
index df2f3fa..e797d23 100644
--- a/scripts/lib/managed-extensions.py
+++ b/scripts/lib/managed-extensions.py
@@ -98,7 +98,10 @@ def fetch_skill(entry):
     skill = entry['codex_skill']
     if not re.fullmatch(r'[A-Za-z0-9_-]+', skill):
         raise ValueError('Skill name is invalid.')
-    request = urllib.request.Request(f'https://codeload.github.com/{source}/zip/HEAD', headers={'User-Agent': 'MyAiConfiguration'})
+    revision = resolve_revision(source)
+    if revision is None:
+        raise ValueError('Cannot resolve an immutable skill revision.')
+    request = urllib.request.Request(f'https://codeload.github.com/{source}/zip/{revision}', headers={'User-Agent': 'MyAiConfiguration'})
     with urllib.request.urlopen(request, timeout=60) as response:
         if not response.url.startswith('https://codeload.github.com/'):
             raise ValueError('Unexpected skill download redirect.')
@@ -134,7 +137,7 @@ def fetch_skill(entry):
             if relative in files:
                 raise ValueError('Skill archive contains duplicate paths.')
             files[relative] = (archive.read(item), bool(item.external_attr >> 16 & 0o111))
-    return skill, files
+    return skill, files, revision
 
 
 def resolve_revision(source):
@@ -143,7 +146,7 @@ def resolve_revision(source):
         with urllib.request.urlopen(request, timeout=10) as response:
             payload = json.loads(response.read(1024 * 1024))
         revision = payload.get('sha') if isinstance(payload, dict) else None
-        return revision if isinstance(revision, str) and re.fullmatch(r'[0-9a-fA-F]{7,64}', revision) else None
+        return revision if isinstance(revision, str) and re.fullmatch(r'[0-9a-fA-F]{40}', revision) else None
     except (OSError, ValueError, json.JSONDecodeError):
         return None
 
@@ -428,7 +431,7 @@ class Manager:
             return
         fetched = fetch_skill(entry)
         _, files = fetched[:2]
-        revision = fetched[2] if len(fetched) > 2 else resolve_revision(entry['codex_source'])
+        revision = fetched[2] if len(fetched) > 2 else None
         if record is None:
             record = dict(client='codex', name=entry['name'], kind='skill', directory=directory, source=entry['codex_source'], files={}, complete=False)
             self.state['resources'].append(record)