@@ -93,7 +93,11 @@ def _cached_default(root: Path, repository: str, remotes: dict[str, str]) -> str
     for name in names:
         target = _git(root, "symbolic-ref", "--quiet", f"refs/remotes/{name}/HEAD", optional=True)
         prefix = f"refs/remotes/{name}/"
-        if target.startswith(prefix) and target != prefix + "HEAD":
+        if (
+            target.startswith(prefix)
+            and target != prefix + "HEAD"
+            and _git(root, "rev-parse", "--verify", "--quiet", target, optional=True)
+        ):
             branches.add(target.removeprefix(prefix))
     instructions = "; ".join(f"git remote set-head {name} --auto" for name in names)
     if not branches:
 
@@ -30,12 +30,26 @@ def checkout(tmp_path):
     root = tmp_path / "checkout space$#"
     root.mkdir()
     git(root, "init")
+    git(
+        root,
+        "-c",
+        "user.name=Link Test",
+        "-c",
+        "[email protected]",
+        "-c",
+        "commit.gpgsign=false",
+        "commit",
+        "--allow-empty",
+        "-m",
+        "Initial test revision",
+    )
     return root
 
 
 def remote(root, alias, url, branch=None):
     git(root, "remote", "add", alias, url)
     if branch is not None:
+        git(root, "update-ref", f"refs/remotes/{alias}/{branch}", "HEAD")
         git(root, "symbolic-ref", f"refs/remotes/{alias}/HEAD", f"refs/remotes/{alias}/{branch}")
 
 
@@ -135,6 +149,16 @@ def test_missing_cached_head_gives_matching_remote_refresh_instruction(tmp_path,
         links.repository_defaults(root)
 
 
+@pytest.mark.agent_authored(model="gpt-6.1-sol")
+def test_dangling_cached_head_requires_refresh_instead_of_using_removed_branch(tmp_path, monkeypatch):
+    monkeypatch.delenv(links.METADATA_ENV, raising=False)
+    root = checkout(tmp_path)
+    remote(root, "upstream", "https://github.com/NVIDIA/cuda-python.git")
+    git(root, "symbolic-ref", "refs/remotes/upstream/HEAD", "refs/remotes/upstream/removed")
+    with pytest.raises(ValueError, match="git remote set-head upstream --auto"):
+        links.repository_defaults(root)
+
+
 @pytest.mark.agent_authored(model="gpt-6.1-sol")
 def test_conflicting_cached_heads_fail_instead_of_choosing_arbitrarily(tmp_path, monkeypatch):
     monkeypatch.delenv(links.METADATA_ENV, raising=False)