diff --git a/.github/CHANGELOG.md b/.github/CHANGELOG.md
index 8d992c0..0920053 100644
--- a/.github/CHANGELOG.md
+++ b/.github/CHANGELOG.md
@@ -9,6 +9,10 @@
   the package version; publishing uses PyPI trusted publishing.
 - Made the safe runtime the default while retaining the legacy runtime only
   behind an explicit migration flag.
+- Changed the safe runtime's `Py7zip.get_binary_url()` to raise
+  `NotImplementedError` directing callers to the public `download_binary()`
+  entry point instead of returning a fabricated cache-relative path
+  (OVH-05).
 
 ## 0.7.3
 
diff --git a/py7zip/py7zip.py b/py7zip/py7zip.py
index dda88d9..00a6056 100644
--- a/py7zip/py7zip.py
+++ b/py7zip/py7zip.py
@@ -8,7 +8,6 @@
 
 import requests
 
-from .platforms import ArtifactCatalog
 from .safe import SafePy7zip
 
 
@@ -145,10 +144,27 @@ def download_binary(self):
             os.chmod(self.binary_path, 0o755)
 
     def get_binary_url(self):
-        """Dynamically gets the URL of the required system binary."""
+        """Return the source location for the platform's 7-Zip binary.
+
+        On the safe runtime (default), binary acquisition is explicit:
+        callers must invoke :meth:`download_binary` (or supply a
+        pre-verified ``binary_path``) before using the wrapper. This
+        method raises :class:`NotImplementedError` rather than returning
+        a fabricated cache-relative path, because the safe runtime does
+        not construct download URLs at construction time.
+
+        On the legacy runtime (``legacy=True``), returns the URL where
+        the historical in-package binary would have been served from,
+        or raises :class:`NotImplementedError` for unsupported host
+        platforms.
+        """
         if not self.legacy:
-            spec = ArtifactCatalog.resolve(self.platform_info)
-            return f"{self._safe.cache_dir}/{spec.relative_path}"
+            raise NotImplementedError(
+                "get_binary_url() is not supported on the safe runtime; "
+                "call download_binary() to acquire a verified binary into "
+                "the cache directory, or supply a pre-verified "
+                "binary_path=... to the constructor."
+            )
         if self.platform not in self.supported:
             raise NotImplementedError(f"Platform '{self.platform}' is not supported.")
         return self.url
diff --git a/tests/test_default_api.py b/tests/test_default_api.py
index 81a911d..e1b1ccc 100644
--- a/tests/test_default_api.py
+++ b/tests/test_default_api.py
@@ -30,6 +30,26 @@ def test_default_aliases_require_individual_option_arguments(tmp_path):
         wrapper.compress("source", "destination", options="-y")
 
 
+def test_get_binary_url_raises_on_safe_runtime(tmp_path):
+    """The safe runtime exposes acquisition, not download URLs.
+
+    Per the F2 finding in the platform-architecture audit, the safe
+    runtime previously returned a fabricated cache-relative path that
+    did not correspond to any real download. Acquisition is now
+    explicit via the public ``download_binary()`` entry point; this
+    method raises a typed error pointing callers at that API rather
+    than the internal ``SafePy7zip.ensure_binary()``.
+    """
+    wrapper = Py7zip(cache_dir=tmp_path)
+
+    with pytest.raises(NotImplementedError) as excinfo:
+        wrapper.get_binary_url()
+
+    message = str(excinfo.value)
+    assert "download_binary()" in message
+    assert "ensure_binary" not in message
+
+
 def test_legacy_mode_is_explicit():
     assert "legacy" in Py7zip.__init__.__code__.co_varnames
     assert ArchiveRunner is not None