From 1cca4b6b1c5aa5e39f69670910bf8d0ca9880cf3 Mon Sep 17 00:00:00 2001
From: Samir Hanna Verza <123646616+samirhvbr@users.noreply.github.com>
Date: Thu, 22 Oct 2026 13:36:57 -0300
Subject: [PATCH] fix(cli): preserve full default branch names in diff scope

---
 strix/interface/utils.py                |  2 +-
 tests/test_diff_scope_default_branch.py | 94 +++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 1 deletion(-)
 create mode 100644 tests/test_diff_scope_default_branch.py

diff --git a/strix/interface/utils.py b/strix/interface/utils.py
index 7ab55d8ee..9d368b1e6 100644
--- a/strix/interface/utils.py
+++ b/strix/interface/utils.py
@@ -675,7 +675,7 @@ def _extract_branch_name(ref: str | None) -> str | None:
     value = ref.strip()
     if not value:
         return None
-    return value.split("/")[-1]
+    return value.removeprefix("refs/remotes/origin/")
 
 
 def _extract_github_base_sha(env: dict[str, str]) -> str | None:
diff --git a/tests/test_diff_scope_default_branch.py b/tests/test_diff_scope_default_branch.py
new file mode 100644
index 000000000..1431b4785
--- /dev/null
+++ b/tests/test_diff_scope_default_branch.py
@@ -0,0 +1,94 @@
+"""Automatic diff-scope must compare complete Git branch names."""
+
+from __future__ import annotations
+
+import shutil
+import subprocess
+from typing import TYPE_CHECKING
+
+import pytest
+
+from strix.interface.utils import resolve_diff_scope_context
+
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+def _git(repo: Path, *args: str) -> str:
+    executable = shutil.which("git")
+    assert executable is not None
+    return subprocess.run(  # noqa: S603 - only synthetic test arguments are passed to Git.
+        [executable, "-C", str(repo), *args],
+        check=True,
+        capture_output=True,
+        text=True,
+    ).stdout.strip()
+
+
+def _commit(repo: Path) -> None:
+    _git(repo, "add", ".")
+    _git(
+        repo,
+        "-c",
+        "user.name=Regression Test",
+        "-c",
+        "user.email=test@example.invalid",
+        "-c",
+        "commit.gpgsign=false",
+        "commit",
+        "-m",
+        "Add synthetic source",
+    )
+
+
+def _default_branch_repo(repo: Path, branch: str) -> list[dict[str, str]]:
+    _git(repo, "init", "-b", branch)
+    (repo / "app.py").write_text('print("synthetic")\n', encoding="utf-8")
+    _commit(repo)
+    remote_ref = f"refs/remotes/origin/{branch}"
+    _git(repo, "update-ref", remote_ref, "HEAD")
+    _git(repo, "symbolic-ref", "refs/remotes/origin/HEAD", remote_ref)
+    return [{"source_path": str(repo), "workspace_subdir": "app"}]
+
+
+@pytest.mark.parametrize("branch", ["main", "release/stable", "release/lts/stable"])
+def test_auto_scope_stays_inactive_on_the_default_branch(tmp_path: Path, branch: str) -> None:
+    sources = _default_branch_repo(tmp_path, branch)
+
+    result = resolve_diff_scope_context(
+        sources, scope_mode="auto", diff_base=None, non_interactive=True, env={"CI": "true"}
+    )
+
+    assert result.active is False
+    assert result.metadata == {"active": False, "mode": "auto"}
+
+
+@pytest.mark.parametrize("branch", ["main", "release/stable"])
+def test_auto_scope_still_activates_on_feature_branches(tmp_path: Path, branch: str) -> None:
+    sources = _default_branch_repo(tmp_path, branch)
+    _git(tmp_path, "switch", "-c", "feature/auth-fix")
+    (tmp_path / "auth.py").write_text('print("changed")\n', encoding="utf-8")
+    _commit(tmp_path)
+
+    result = resolve_diff_scope_context(
+        sources, scope_mode="auto", diff_base=None, non_interactive=True, env={"CI": "true"}
+    )
+
+    assert result.active is True
+    assert result.metadata["total_analyzable_files"] == 1
+    assert result.metadata["repos"][0]["analyzable_files"] == ["auth.py"]
+
+
+def test_branch_sharing_the_default_branch_suffix_is_still_a_feature_branch(tmp_path: Path) -> None:
+    sources = _default_branch_repo(tmp_path, "release/stable")
+    _git(tmp_path, "switch", "-c", "stable")
+    (tmp_path / "auth.py").write_text('print("changed")\n', encoding="utf-8")
+    _commit(tmp_path)
+
+    result = resolve_diff_scope_context(
+        sources, scope_mode="auto", diff_base=None, non_interactive=True, env={"CI": "true"}
+    )
+
+    assert result.active is True
+    assert result.metadata["total_analyzable_files"] == 1