diff --git a/gcode/cli.py b/gcode/cli.py
index 5e744c3..ca4b15f 100644
--- a/gcode/cli.py
+++ b/gcode/cli.py
@@ -252,8 +252,22 @@ def main() -> None:
     parser.add_argument("--session", default=DEFAULT_SESSION, help="Named session for history.")
     parser.add_argument("--yes", action="store_true", help="Auto-approve bash commands (unsafe).")
     parser.add_argument("--version", action="version", version=f"gcode {__version__}")
+    parser.add_argument(
+        "--cwd",
+        metavar="DIR",
+        help="Run as if started in DIR (like git -C), instead of the current directory.",
+    )
     args = parser.parse_args()
 
+    # Before anything reads the working directory. .gcoderc discovery, the
+    # banner and every tool resolve paths against it, so changing it later
+    # would leave them disagreeing about which project this session is for.
+    if args.cwd is not None:
+        try:
+            os.chdir(args.cwd)
+        except OSError as exc:
+            parser.error(f"--cwd {args.cwd!r} is not usable: {exc.strerror}")
+
     # Load ~/.gcode/.env first (setup module's config location)
     load_env()
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
index d0e7f27..734ec01 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -1,5 +1,6 @@
 from unittest.mock import Mock, patch
 
+import pytest
 from gcode import __version__
 from gcode.cli import _cmd_diff, _cmd_status, _cmd_version, _print_help
 
@@ -112,3 +113,110 @@ def test_report_no_models_neither_source():
 
     assert "No model source is reachable" in ui.error.call_args.args[0]
     assert "Ollama" in ui.info.call_args.args[0]
+
+
+def test_help_lists_cwd_flag(capsys):
+
+    from gcode.cli import main
+
+    with patch("sys.argv", ["gcode", "--help"]), pytest.raises(SystemExit) as exc:
+        main()
+
+    assert exc.value.code == 0
+    assert "--cwd" in capsys.readouterr().out
+
+
+class _Sentinel(Exception):
+    """Raised from the first call after the chdir, to stop main() there."""
+
+
+def test_cwd_changes_directory_before_config_is_loaded(tmp_path, monkeypatch):
+    """The chdir must land before anything reads the working directory.
+
+    .gcoderc discovery, the banner and every tool resolve against it, so a
+    chdir performed later would leave them describing different projects.
+    load_env is the first call after it, so raising there proves the ordering
+    without running the interactive session.
+    """
+    import os
+
+    from gcode.cli import main
+
+    start = os.getcwd()
+    seen = {}
+
+    def _record():
+        seen["cwd"] = os.getcwd()
+        raise _Sentinel
+
+    monkeypatch.setattr("gcode.cli.load_env", _record)
+    monkeypatch.setattr("sys.argv", ["gcode", "--cwd", str(tmp_path)])
+    try:
+        with pytest.raises(_Sentinel):
+            main()
+    finally:
+        os.chdir(start)
+
+    assert os.path.realpath(seen["cwd"]) == os.path.realpath(str(tmp_path))
+
+
+def test_without_cwd_the_directory_is_untouched(monkeypatch):
+    import os
+
+    from gcode.cli import main
+
+    start = os.getcwd()
+    seen = {}
+
+    def _record():
+        seen["cwd"] = os.getcwd()
+        raise _Sentinel
+
+    monkeypatch.setattr("gcode.cli.load_env", _record)
+    monkeypatch.setattr("sys.argv", ["gcode"])
+    try:
+        with pytest.raises(_Sentinel):
+            main()
+    finally:
+        os.chdir(start)
+
+    assert seen["cwd"] == start
+
+
+def test_cwd_that_does_not_exist_exits_two(tmp_path, capsys, monkeypatch):
+    """A bad --cwd is user input: one line on stderr, exit 2, no traceback."""
+    import os
+
+    from gcode.cli import main
+
+    missing = tmp_path / "no-such-project"
+    start = os.getcwd()
+    monkeypatch.setattr("sys.argv", ["gcode", "--cwd", str(missing)])
+    try:
+        with pytest.raises(SystemExit) as exc:
+            main()
+    finally:
+        os.chdir(start)
+
+    assert exc.value.code == 2
+    stderr = capsys.readouterr().err
+    assert "--cwd" in stderr
+    assert "Traceback" not in stderr
+
+
+def test_cwd_pointing_at_a_file_exits_two(tmp_path, capsys, monkeypatch):
+    import os
+
+    from gcode.cli import main
+
+    target = tmp_path / "notadir.txt"
+    target.write_text("x\n")
+    start = os.getcwd()
+    monkeypatch.setattr("sys.argv", ["gcode", "--cwd", str(target)])
+    try:
+        with pytest.raises(SystemExit) as exc:
+            main()
+    finally:
+        os.chdir(start)
+
+    assert exc.value.code == 2