fix: add launcher script to wrap langflow startup (#8884)

* Add launcher script to wrap langflow startup

* [autofix.ci] apply automated fixes

* Ruff

* [autofix.ci] apply automated fixes

* ruff

* [autofix.ci] apply automated fixes

* rut pusff

* [autofix.ci] apply automated fixes

* use exec instead of subprocess

* [autofix.ci] apply automated fixes

* Remove forced run addition to cli

* Integrate Typer for improved error handling in langflow launcher

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@langflow.org>

src/backend/base/langflow/langflow_launcher.py

@@ -0,0 +1,51 @@
+import os
+import platform
+import sys
+
+import typer
+
+
+def main():
+    """Launches langflow with appropriate environment setup.
+
+    On macOS, sets required environment variables and replaces current process.
+    On other platforms, calls main function directly.
+    """
+    if platform.system() == "Darwin":  # macOS
+        _launch_with_exec()
+    else:
+        # On non-macOS systems, call the main function directly
+        from langflow.__main__ import main as langflow_main
+
+        langflow_main()
+
+
+def _launch_with_exec():
+    """Launch langflow by replacing current process with properly configured environment.
+
+    This approach is necessary because Objective-C libraries are preloaded by the Python
+    runtime before any Python code executes. Setting OBJC_DISABLE_INITIALIZE_FORK_SAFETY
+    within Python code is too late - it must be set in the parent process environment
+    before spawning Python.
+
+    Testing with OBJC_PRINT_INITIALIZE=YES confirms that NSCheapMutableString and
+    other Objective-C classes are initialized during Python startup, before any
+    user code runs. This causes fork safety issues when gunicorn or multiprocessing
+    attempts to fork the process.
+
+    The exec approach sets the environment variables and then replaces the current
+    process with a new Python process. This is more efficient than subprocess since
+    we don't need the launcher process to remain running, and signals are handled
+    directly by the target process.
+    """
+    # Set environment variables before exec
+    os.environ["OBJC_DISABLE_INITIALIZE_FORK_SAFETY"] = "YES"
+    # Additional fix for gunicorn compatibility
+    os.environ["no_proxy"] = "*"
+
+    try:
+        os.execv(sys.executable, [sys.executable, "-m", "langflow.__main__"] + sys.argv[1:])  # noqa: S606
+    except OSError as e:
+        # If exec fails, we need to exit since the process replacement failed
+        typer.echo(f"Failed to exec langflow: {e}", file=sys.stderr)
+        sys.exit(1)