diff --git a/src/foreignthon/cli.py b/src/foreignthon/cli.py
index e69de29..6c8e953 100644
--- a/src/foreignthon/cli.py
+++ b/src/foreignthon/cli.py
@@ -0,0 +1,111 @@
+from __future__ import annotations
+
+import runpy
+import sys
+import tempfile
+from pathlib import Path
+
+import click
+
+from . import __version__
+from .errors import activate
+from .transpiler import transpile_file
+
+
+@click.group()
+@click.version_option(__version__, prog_name="fpy")
+def main():
+    """ForeignThon — write Python in any language."""
+    pass
+
+
+@main.command()
+@click.argument("file", type=click.Path(exists=True, path_type=Path))
+@click.option("--lang", "-l", default=None, help="Override language code (e.g. es, ta)")
+@click.option("--keep", is_flag=True, help="Keep the compiled .py file alongside the source")
+def run(file: Path, lang: str | None, keep: bool):
+    """Transpile and run a foreign-language Python file."""
+    if lang:
+        # Inject shebang override so transpiler picks it up
+        source = file.read_text(encoding="utf-8")
+        if not source.startswith("# foreignthon:"):
+            source = f"# foreignthon: {lang}\n" + source
+        file.write_text(source, encoding="utf-8")
+
+    transpiled = transpile_file(file)
+
+    # Detect lang for error hook
+    detected_lang = lang or _lang_from_file(file)
+    activate(detected_lang)
+
+    if keep:
+        out_path = file.with_suffix("").with_suffix(".compiled.py")
+        out_path.write_text(transpiled, encoding="utf-8")
+        click.echo(f"Compiled: {out_path}")
+
+    # Write to a temp file and run it — runpy keeps __file__ correct
+    with tempfile.NamedTemporaryFile(
+        suffix=".py", mode="w", encoding="utf-8", delete=False
+    ) as tmp:
+        tmp.write(transpiled)
+        tmp_path = tmp.name
+
+    try:
+        runpy.run_path(tmp_path, run_name="__main__")
+    finally:
+        Path(tmp_path).unlink(missing_ok=True)
+
+
+@main.command()
+@click.argument("file", type=click.Path(exists=True, path_type=Path))
+@click.option("--output", "-o", default=None, help="Output path (default: same dir as source)")
+def compile(file: Path, output: str | None):
+    """Transpile a file to standard Python without running it."""
+    transpiled = transpile_file(file)
+
+    out_path = Path(output) if output else file.with_suffix("").with_suffix(".compiled.py")
+    out_path.write_text(transpiled, encoding="utf-8")
+    click.echo(f"Compiled: {out_path}")
+
+
+@main.command()
+@click.argument("file", type=click.Path(exists=True, path_type=Path))
+def check(file: Path):
+    """Validate a foreign-language file without running it."""
+    import ast
+
+    try:
+        transpiled = transpile_file(file)
+        ast.parse(transpiled)
+        click.echo(f"✓ {file.name} looks good.")
+    except SyntaxError as e:
+        click.echo(f"✗ Syntax error: {e}", err=True)
+        sys.exit(1)
+    except Exception as e:
+        click.echo(f"✗ {e}", err=True)
+        sys.exit(1)
+
+
+@main.command("pack")
+@click.argument("json_file", type=click.Path(exists=True, path_type=Path))
+def validate_pack(json_file: Path):
+    """Validate a language pack JSON file."""
+    import json
+    from .pack import REQUIRED_SECTIONS
+
+    with open(json_file, encoding="utf-8") as f:
+        data = json.load(f)
+
+    missing = REQUIRED_SECTIONS - data.keys()
+    if missing:
+        click.echo(f"✗ Missing sections: {missing}", err=True)
+        sys.exit(1)
+
+    click.echo(f"✓ Pack '{data['meta']['name']}' is valid.")
+
+
+def _lang_from_file(path: Path) -> str:
+    suffixes = path.suffixes
+    if len(suffixes) >= 2 and suffixes[-1] == ".py":
+        return suffixes[-2].lstrip(".")
+    return "en"