Treat GIT_BRANCH_NAME naming the current branch as a no-op

extensions/catalog.json

@@ -51,7 +51,7 @@
     "git": {
       "name": "Git Branching Workflow",
       "id": "git",
-      "version": "1.0.1",
+      "version": "1.0.2",
       "description": "Feature branch creation, numbering (sequential/timestamp), validation, and Git remote detection",
       "author": "spec-kit-core",
       "repository": "https://github.com/github/spec-kit",

extensions/git/commands/speckit.git.feature.md

@@ -19,6 +19,7 @@ You **MUST** consider the user input before proceeding (if not empty).
 If the user explicitly provided `GIT_BRANCH_NAME` (e.g., via environment variable, argument, or in their request), pass it through to the script by setting the `GIT_BRANCH_NAME` environment variable before invoking the script. When `GIT_BRANCH_NAME` is set:
 - The script uses the exact value as the branch name, bypassing all prefix/suffix generation
 - `--short-name`, `--number`, and `--timestamp` flags are ignored
+- If the value names the branch that is already checked out, the script succeeds without switching or creating a branch
 - `FEATURE_NUM` is extracted when the final path segment starts with a numeric or timestamp feature marker (for example `042-name`, `feat/042-name`, or `jdoe/app/042-name`), otherwise set to the full branch name
 
 ## Prerequisites

extensions/git/extension.yml

@@ -3,7 +3,7 @@ schema_version: "1.0"
 extension:
   id: git
   name: "Git Branching Workflow"
-  version: "1.0.1"
+  version: "1.0.2"
   description: "Feature branch creation, numbering (sequential/timestamp), templating, validation, and Git remote detection"
   author: spec-kit-core
   repository: https://github.com/github/spec-kit

extensions/git/scripts/bash/create-new-feature-branch.sh

@@ -569,7 +569,9 @@ if [ "$DRY_RUN" != true ]; then
         if ! branch_create_error=$(git checkout -q -b "$BRANCH_NAME" 2>&1); then
             current_branch="$(git rev-parse --abbrev-ref HEAD 2>/dev/null || true)"
             if git branch --list "$BRANCH_NAME" | grep -q .; then
-                if [ "$ALLOW_EXISTING" = true ]; then
+                # An explicit GIT_BRANCH_NAME naming the checked-out branch is
+                # already satisfied, so treat it like --allow-existing-branch.
+                if [ "$ALLOW_EXISTING" = true ] || { [ -n "${GIT_BRANCH_NAME:-}" ] && [ "$current_branch" = "$BRANCH_NAME" ]; }; then
                     if [ "$current_branch" = "$BRANCH_NAME" ]; then
                         :
                     elif ! switch_branch_error=$(git checkout -q "$BRANCH_NAME" 2>&1); then

extensions/git/scripts/powershell/create-new-feature-branch.ps1

@@ -526,7 +526,9 @@ if (-not $DryRun) {
             try { $currentBranch = (git rev-parse --abbrev-ref HEAD 2>$null).Trim() } catch {}
             $existingBranch = git branch --list $branchName 2>$null
             if ($existingBranch) {
-                if ($AllowExistingBranch) {
+                # An explicit GIT_BRANCH_NAME naming the checked-out branch is
+                # already satisfied, so treat it like -AllowExistingBranch.
+                if ($AllowExistingBranch -or ($env:GIT_BRANCH_NAME -and $currentBranch -ceq $branchName)) {
                     if ($currentBranch -eq $branchName) {
                         # Already on the target branch
                     } else {

extensions/git/scripts/python/create_new_feature_branch.py

@@ -574,7 +574,11 @@ def build_branch_name(feature_num: str, branch_suffix: str) -> str:
                     _git_lines(repo_root, "branch", "--list", branch_name)
                 )
                 if branch_exists:
-                    if args.allow_existing:
+                    # An explicit GIT_BRANCH_NAME naming the checked-out branch is
+                    # already satisfied, so treat it like --allow-existing-branch.
+                    if args.allow_existing or (
+                        env_branch_name and current_branch == branch_name
+                    ):
                         if current_branch != branch_name:
                             switch = subprocess.run(
                                 ["git", "checkout", "-q", branch_name],

tests/extensions/git/test_git_extension.py

@@ -145,7 +145,7 @@ def test_manifest_validates(self):
 
         m = ExtensionManifest(EXT_DIR / "extension.yml")
         assert m.id == "git"
-        assert m.version == "1.0.1"
+        assert m.version == "1.0.2"
 
     def test_manifest_commands(self):
         """Manifest declares expected commands."""
@@ -500,6 +500,28 @@ def test_branch_template_rejects_slug_before_number(self, tmp_path: Path):
         assert "{slug}" in result.stderr
         assert "{number}" in result.stderr
 
+    def test_git_branch_name_override_naming_current_branch_is_noop(self, tmp_path: Path):
+        """GIT_BRANCH_NAME equal to the checked-out branch exits 0 without switching."""
+        project = _setup_project(tmp_path)
+        subprocess.run(
+            ["git", "checkout", "-q", "-b", "feature/PROJ-42-login"],
+            cwd=project, check=True,
+        )
+        result = _run_bash(
+            "create-new-feature-branch.sh", project,
+            "--json", "--short-name", "login", "Login page",
+            env_extra={"GIT_BRANCH_NAME": "feature/PROJ-42-login"},
+        )
+
+        assert result.returncode == 0, result.stderr
+        data = json.loads(result.stdout)
+        assert data["BRANCH_NAME"] == "feature/PROJ-42-login"
+        head = subprocess.run(
+            ["git", "rev-parse", "--abbrev-ref", "HEAD"],
+            cwd=project, capture_output=True, text=True, check=True,
+        ).stdout.strip()
+        assert head == "feature/PROJ-42-login"
+
     def test_git_branch_name_override_extracts_number_after_namespace(self, tmp_path: Path):
         """GIT_BRANCH_NAME extracts FEATURE_NUM from a namespaced branch."""
         project = _setup_project(tmp_path / "app-a")
@@ -920,6 +942,50 @@ def test_git_branch_name_override_ignores_numeric_namespace_segments(self, tmp_p
         assert data["BRANCH_NAME"] == "jdoe/2026-app/042-custom-branch"
         assert data["FEATURE_NUM"] == "042"
 
+    def test_git_branch_name_override_naming_current_branch_is_noop(self, tmp_path: Path):
+        """PowerShell GIT_BRANCH_NAME equal to the checked-out branch exits 0 without switching."""
+        project = _setup_project(tmp_path)
+        subprocess.run(
+            ["git", "checkout", "-q", "-b", "feature/PROJ-42-login"],
+            cwd=project, check=True,
+        )
+        result = _run_pwsh(
+            "create-new-feature-branch.ps1", project,
+            "-Json", "-ShortName", "login", "Login page",
+            env_extra={"GIT_BRANCH_NAME": "feature/PROJ-42-login"},
+        )
+
+        assert result.returncode == 0, result.stderr
+        data = json.loads(result.stdout)
+        assert data["BRANCH_NAME"] == "feature/PROJ-42-login"
+        head = subprocess.run(
+            ["git", "rev-parse", "--abbrev-ref", "HEAD"],
+            cwd=project, capture_output=True, text=True, check=True,
+        ).stdout.strip()
+        assert head == "feature/PROJ-42-login"
+
+    def test_git_branch_name_override_naming_other_existing_branch_fails(self, tmp_path: Path):
+        """PowerShell GIT_BRANCH_NAME naming a different existing branch is rejected without switching."""
+        project = _setup_project(tmp_path)
+        subprocess.run(["git", "branch", "feature/other"], cwd=project, check=True)
+        before = subprocess.run(
+            ["git", "rev-parse", "--abbrev-ref", "HEAD"],
+            cwd=project, capture_output=True, text=True, check=True,
+        ).stdout.strip()
+        result = _run_pwsh(
+            "create-new-feature-branch.ps1", project,
+            "-Json", "-ShortName", "login", "Login page",
+            env_extra={"GIT_BRANCH_NAME": "feature/other"},
+        )
+
+        assert result.returncode == 1
+        assert "already exists" in result.stderr
+        head = subprocess.run(
+            ["git", "rev-parse", "--abbrev-ref", "HEAD"],
+            cwd=project, capture_output=True, text=True, check=True,
+        ).stdout.strip()
+        assert head == before
+
     def test_git_branch_name_override_without_feature_marker_preserves_full_name(self, tmp_path: Path):
         """PowerShell keeps the full override name when no feature marker exists."""
         project = _setup_project(tmp_path / "app-a")

tests/extensions/git/test_git_extension_python_parity.py

@@ -379,6 +379,38 @@ def test_git_branch_name_override(self, tmp_path: Path):
         _assert_parity(b, p)
         assert json.loads(p.stdout) == {"BRANCH_NAME": "team/042-exact-name", "FEATURE_NUM": "042"}
 
+    def test_git_branch_name_override_naming_current_branch_is_noop(
+        self, tmp_path: Path
+    ):
+        bash_proj, py_proj = _twin_projects(tmp_path)
+        env = {"GIT_BRANCH_NAME": "feature/PROJ-42-login"}
+        for proj in (bash_proj, py_proj):
+            subprocess.run(
+                ["git", "checkout", "-q", "-b", "feature/PROJ-42-login"],
+                cwd=proj, check=True,
+            )
+        b = _run_bash("create-new-feature-branch.sh", bash_proj, "--json", "desc word", env_extra=env)
+        p = _run_py("create-new-feature-branch", py_proj, "--json", "desc word", env_extra=env)
+        _assert_parity(b, p)
+        assert p.returncode == 0, p.stderr
+        assert json.loads(p.stdout) == {
+            "BRANCH_NAME": "feature/PROJ-42-login",
+            "FEATURE_NUM": "feature/PROJ-42-login",
+        }
+
+    def test_git_branch_name_override_naming_other_existing_branch_fails(
+        self, tmp_path: Path
+    ):
+        bash_proj, py_proj = _twin_projects(tmp_path)
+        env = {"GIT_BRANCH_NAME": "feature/other"}
+        for proj in (bash_proj, py_proj):
+            subprocess.run(["git", "branch", "feature/other"], cwd=proj, check=True)
+        b = _run_bash("create-new-feature-branch.sh", bash_proj, "--json", "desc word", env_extra=env)
+        p = _run_py("create-new-feature-branch", py_proj, "--json", "desc word", env_extra=env)
+        _assert_parity(b, p)
+        assert p.returncode == 1
+        assert "already exists" in p.stderr
+
     def test_git_branch_name_override_persist_hint_matches_bash(
         self, tmp_path: Path
     ):