diff --git a/src/vcspull/cli/sync.py b/src/vcspull/cli/sync.py
index 1f754887..d7094036 100644
--- a/src/vcspull/cli/sync.py
+++ b/src/vcspull/cli/sync.py
@@ -3,10 +3,12 @@
 from __future__ import annotations
 
 import logging
+import subprocess
 import sys
 import typing as t
 from copy import deepcopy
 
+from libvcs import exc as libvcs_exc
 from libvcs._internal.shortcuts import create_project
 from libvcs.url import registry as url_tools
 
@@ -23,6 +25,22 @@
 
 log = logging.getLogger(__name__)
 
+BRANCH_ERROR_MSG = """
+⚠️  Error syncing '{repo_name}': Branch issue detected
+
+The repository appears to be on a local branch with no remote tracking.
+
+To fix this, add a 'rev' field to your vcspull configuration:
+
+  {repo_name}:
+    repo: {repo_url}
+    rev: main  # or specify your desired branch
+
+Alternatively, switch to a branch that exists remotely:
+  cd {repo_path}
+  git checkout main  # or another remote branch{available_branches}
+"""
+
 
 def clamp(n: int, _min: int, _max: int) -> int:
     """Clamp a number between a min and max value."""
@@ -142,6 +160,130 @@ def __init__(self, repo_url: str, *args: object, **kwargs: object) -> None:
         return super().__init__(f"Could not automatically determine VCS for {repo_url}")
 
 
+def check_branch_state(repo_dict: dict[str, t.Any]) -> bool:
+    """Check if repository is in a problematic branch state.
+
+    Returns True if there are potential branch issues that should be addressed
+    before attempting to sync.
+
+    Parameters
+    ----------
+    repo_dict : dict
+        Repository configuration dictionary
+
+    Returns
+    -------
+    bool
+        True if branch issues detected, False otherwise
+    """
+    repo_path = repo_dict.get("path")
+    if not repo_path:
+        return False
+
+    try:
+        # Check if we're in a git repository
+        git_dir = subprocess.run(
+            ["git", "-C", str(repo_path), "rev-parse", "--git-dir"],
+            capture_output=True,
+            text=True,
+            timeout=5,
+            check=False,
+        )
+        if git_dir.returncode != 0:
+            return False  # Not a git repo or git not available
+
+        # Get current branch
+        current_branch = subprocess.run(
+            ["git", "-C", str(repo_path), "branch", "--show-current"],
+            capture_output=True,
+            text=True,
+            timeout=5,
+            check=False,
+        )
+        if current_branch.returncode != 0:
+            return False  # Can't determine current branch
+
+        branch_name = current_branch.stdout.strip()
+        if not branch_name:
+            return False  # Detached HEAD or other edge case
+
+        # Check if current branch has upstream tracking
+        upstream_ref = f"{branch_name}@{{upstream}}"
+        upstream = subprocess.run(
+            ["git", "-C", str(repo_path), "rev-parse", "--abbrev-ref", upstream_ref],
+            capture_output=True,
+            text=True,
+            timeout=5,
+            check=False,
+        )
+
+        if upstream.returncode != 0:
+            # No upstream tracking - this is potentially problematic
+            # Even if the remote branch exists, the lack of upstream tracking
+            # can cause libvcs to construct invalid remote references
+            # Check if there's a remote branch with the same name
+            remote_ref = f"origin/{branch_name}"
+            remote_branch = subprocess.run(
+                ["git", "-C", str(repo_path), "rev-parse", "--verify", remote_ref],
+                capture_output=True,
+                text=True,
+                timeout=5,
+                check=False,
+            )
+            if remote_branch.returncode != 0:
+                # Current branch doesn't exist on remote - this will cause issues
+                return True
+            # Branch exists on remote but no upstream tracking
+            # This can still cause issues with libvcs's remote name detection
+            return True
+        else:
+            return False  # Branch state looks good
+
+    except (subprocess.TimeoutExpired, FileNotFoundError):
+        return False  # Git command failed or not available
+
+
+def handle_branch_error(repo_dict: dict[str, t.Any]) -> None:
+    """Handle branch-related errors by showing helpful instructions.
+
+    Parameters
+    ----------
+    repo_dict : dict
+        Repository configuration dictionary
+    """
+    repo_name = repo_dict.get("name", "repository")
+    repo_url = repo_dict.get("url", "YOUR_REPO_URL")
+    repo_path = repo_dict.get("path", "REPO_PATH")
+
+    # Try to get available remote branches
+    available_branches = ""
+    try:
+        cmd = ["git", "-C", str(repo_path), "branch", "-r"]
+        result = subprocess.run(
+            cmd, capture_output=True, text=True, timeout=5, check=False
+        )
+        if result.returncode == 0 and result.stdout:
+            branches = [
+                line.strip().replace("origin/", "")
+                for line in result.stdout.splitlines()
+                if "origin/" in line and "->" not in line
+            ][:5]  # Show first 5 branches
+            if branches:
+                branch_list = ", ".join(branches)
+                available_branches = f"\n\nAvailable remote branches: {branch_list}"
+    except (subprocess.TimeoutExpired, FileNotFoundError):
+        pass  # Git command failed or not available
+
+    error_msg = BRANCH_ERROR_MSG.format(
+        repo_name=repo_name,
+        repo_url=repo_url,
+        repo_path=repo_path,
+        available_branches=available_branches,
+    )
+
+    print(error_msg, file=sys.stderr)
+
+
 def update_repo(
     repo_dict: t.Any,
     # repo_dict: Dict[str, Union[str, Dict[str, GitRemote], pathlib.Path]]
@@ -162,7 +304,21 @@ def update_repo(
         repo_dict["vcs"] = vcs
 
     r = create_project(**repo_dict)  # Creates the repo object
-    r.update_repo(set_remotes=True)  # Creates repo if not exists and fetches
+
+    # Check for branch issues before attempting to sync
+    if check_branch_state(repo_dict):
+        handle_branch_error(repo_dict)
+        # Still attempt the sync but user has been warned
+
+    try:
+        r.update_repo(set_remotes=True)  # Creates repo if not exists and fetches
+    except libvcs_exc.CommandError as e:
+        error_msg = str(e).lower()
+        # Check for branch-related errors (fallback in case pre-check missed something)
+        if "invalid upstream" in error_msg or "ambiguous argument" in error_msg:
+            handle_branch_error(repo_dict)
+            raise
+        raise
 
     # TODO: Fix this
     return r  # type:ignore
diff --git a/tests/test_sync.py b/tests/test_sync.py
index e7a379ed..e99af84c 100644
--- a/tests/test_sync.py
+++ b/tests/test_sync.py
@@ -2,15 +2,18 @@
 
 from __future__ import annotations
 
+import subprocess
 import textwrap
 import typing as t
+from unittest.mock import patch
 
 import pytest
+from libvcs import exc as libvcs_exc
 from libvcs._internal.shortcuts import create_project
 from libvcs.sync.git import GitRemote, GitSync
 
 from vcspull._internal.config_reader import ConfigReader
-from vcspull.cli.sync import update_repo
+from vcspull.cli.sync import check_branch_state, handle_branch_error, update_repo
 from vcspull.config import extract_repos, filter_repos, load_configs
 from vcspull.validator import is_valid_config
 
@@ -314,3 +317,226 @@ def test_updating_remote(
                     expected_config["remotes"]["origin"].fetch_url.replace("git+", "")
                     == current_remote_url
                 )
+
+
+def test_check_branch_state(tmp_path: pathlib.Path) -> None:
+    """Test that check_branch_state detects problematic branches."""
+    repo_dict = {
+        "name": "test-repo",
+        "url": "git@github.com:user/repo.git",
+        "path": tmp_path / "test-repo",
+    }
+
+    # Create a mock git directory for testing
+    (tmp_path / "test-repo" / ".git").mkdir(parents=True, exist_ok=True)
+
+    # Mock successful git commands that indicate problematic state
+    with patch("subprocess.run") as mock_run:
+
+        def git_side_effect(cmd: list[str], **kwargs: t.Any) -> t.Any:
+            from unittest.mock import MagicMock
+
+            mock_result = MagicMock()
+
+            if "--git-dir" in cmd:
+                # Git directory check - success
+                mock_result.returncode = 0
+                return mock_result
+            elif "--show-current" in cmd:
+                # Current branch - return 'docs'
+                mock_result.returncode = 0
+                mock_result.stdout = "docs\n"
+                return mock_result
+            elif "@{upstream}" in " ".join(cmd):
+                # No upstream tracking
+                mock_result.returncode = 1  # No upstream
+                return mock_result
+            elif "origin/docs" in cmd:
+                # No origin/docs branch
+                mock_result.returncode = 1  # Branch doesn't exist on remote
+                return mock_result
+            else:
+                mock_result.returncode = 0
+                return mock_result
+
+        mock_run.side_effect = git_side_effect
+
+        # Should detect branch issue
+        assert check_branch_state(repo_dict) is True
+
+
+def test_check_branch_state_good_branch(tmp_path: pathlib.Path) -> None:
+    """Test that check_branch_state doesn't flag good branches."""
+    repo_dict = {
+        "name": "test-repo",
+        "url": "git@github.com:user/repo.git",
+        "path": tmp_path / "test-repo",
+    }
+
+    # Create a mock git directory for testing
+    (tmp_path / "test-repo" / ".git").mkdir(parents=True, exist_ok=True)
+
+    # Mock git commands that indicate good state
+    with patch("subprocess.run") as mock_run:
+
+        def git_side_effect(cmd: list[str], **kwargs: t.Any) -> t.Any:
+            from unittest.mock import MagicMock
+
+            mock_result = MagicMock()
+
+            if "--git-dir" in cmd:
+                # Git directory check - success
+                mock_result.returncode = 0
+                return mock_result
+            elif "--show-current" in cmd:
+                # Current branch - return 'main'
+                mock_result.returncode = 0
+                mock_result.stdout = "main\n"
+                return mock_result
+            elif "@{upstream}" in " ".join(cmd):
+                # Has upstream tracking
+                mock_result.returncode = 0  # Has upstream
+                mock_result.stdout = "origin/main\n"
+                return mock_result
+            else:
+                mock_result.returncode = 0
+                return mock_result
+
+        mock_run.side_effect = git_side_effect
+
+        # Should NOT detect branch issue
+        assert check_branch_state(repo_dict) is False
+
+
+def test_handle_branch_error(
+    tmp_path: pathlib.Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    """Test that handle_branch_error shows helpful error message."""
+    repo_dict = {
+        "name": "test-repo",
+        "url": "git@github.com:user/repo.git",
+        "path": tmp_path / "test-repo",
+    }
+
+    # Create a mock git directory for testing
+    (tmp_path / "test-repo" / ".git").mkdir(parents=True, exist_ok=True)
+
+    # Mock subprocess.run to simulate git branch output
+    with patch("subprocess.run") as mock_run:
+        mock_run.return_value.returncode = 0
+        mock_run.return_value.stdout = """  origin/HEAD -> origin/main
+  origin/main
+  origin/develop
+  origin/feature/test
+  origin/v1.0.0
+  origin/v2.0.0
+  origin/docs"""
+
+        handle_branch_error(repo_dict)
+
+    captured = capsys.readouterr()
+
+    # Check that the error message contains expected elements
+    assert "Error syncing 'test-repo': Branch issue detected" in captured.err
+    assert "add a 'rev' field to your vcspull configuration" in captured.err
+    assert "test-repo:" in captured.err
+    assert "repo: git@github.com:user/repo.git" in captured.err
+    assert f"cd {tmp_path / 'test-repo'}" in captured.err
+    expected_branches = "main, develop, feature/test, v1.0.0, v2.0.0"
+    assert f"Available remote branches: {expected_branches}" in captured.err
+
+
+def test_handle_branch_error_no_git(
+    tmp_path: pathlib.Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    """Test handle_branch_error when git command fails."""
+    repo_dict = {
+        "name": "test-repo",
+        "url": "git@github.com:user/repo.git",
+        "path": tmp_path / "test-repo",
+    }
+
+    # Mock subprocess.run to simulate git command failure
+    with patch("subprocess.run") as mock_run:
+        mock_run.side_effect = FileNotFoundError("git not found")
+
+        handle_branch_error(repo_dict)
+
+    captured = capsys.readouterr()
+
+    # Check that the error message still works without branches list
+    assert "Error syncing 'test-repo': Branch issue detected" in captured.err
+    assert "Available remote branches" not in captured.err
+
+
+def test_update_repo_branch_error_precheck(
+    tmp_path: pathlib.Path,
+    git_remote_repo: pathlib.Path,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Test that update_repo detects branch errors with pre-validation."""
+    repo_config = {
+        "name": "test-repo",
+        "url": f"git+file://{git_remote_repo}",
+        "path": str(tmp_path / "test-repo"),
+        "vcs": "git",
+    }
+
+    # First, create the repository normally
+    update_repo(repo_config)
+
+    # Create and checkout a local branch with no remote
+    repo_path = tmp_path / "test-repo"
+    subprocess.run(
+        ["git", "-C", str(repo_path), "checkout", "-b", "local-only"], check=True
+    )
+
+    # Mock check_branch_state to return True (problematic branch detected)
+    with patch("vcspull.cli.sync.check_branch_state", return_value=True):
+        # This should trigger the pre-validation warning
+        update_repo(repo_config)
+
+    captured = capsys.readouterr()
+
+    # Verify error handler was called during pre-validation
+    assert "Error syncing 'test-repo': Branch issue detected" in captured.err
+    assert "add a 'rev' field to your vcspull configuration" in captured.err
+
+
+def test_update_repo_branch_error_fallback(
+    tmp_path: pathlib.Path,
+    git_remote_repo: pathlib.Path,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Test that update_repo still catches CommandError as fallback."""
+    repo_config = {
+        "name": "test-repo",
+        "url": f"git+file://{git_remote_repo}",
+        "path": str(tmp_path / "test-repo"),
+        "vcs": "git",
+    }
+
+    # First, create the repository normally
+    update_repo(repo_config)
+
+    # Mock check_branch_state to return False (no issue detected in pre-check)
+    # But mock update_repo to raise CommandError (fallback case)
+    with (
+        patch("vcspull.cli.sync.check_branch_state", return_value=False),
+        patch.object(GitSync, "update_repo") as mock_update,
+    ):
+        mock_update.side_effect = libvcs_exc.CommandError(
+            output="fatal: invalid upstream 'origin/local-only'",
+            returncode=1,
+            cmd="git rebase origin/local-only",
+        )
+
+        # Try to update, should trigger fallback error handling
+        with pytest.raises(libvcs_exc.CommandError):
+            update_repo(repo_config)
+
+    captured = capsys.readouterr()
+
+    # Verify error handler was called as fallback
+    assert "Error syncing 'test-repo': Branch issue detected" in captured.err
+    assert "add a 'rev' field to your vcspull configuration" in captured.err