Quickly auto-reload for changes in src/backend/base/langflow modules during development

[Ethan16162]

When using LFX_DEV=1 make backend/frontend to start the LangFlow project, how can I synchronize changes made under src/backend/base/langflow without restarting the entire project?

When I start the project using the above command, it takes a long time to restart:

✓ Stopping Server...
✓ Cancelling Background Tasks...
✓ Cleaning Up Services...
✓ Clearing Temporary Files...
✓ Finalizing Shutdown...
INFO:     Application shutdown complete.
INFO:     Finished server process [162489]


INFO:     Started server process [167136]
INFO:     Waiting for application startup.

Looking forward to your reply.

[xXMrNidaXx]

Quick auto-reload for backend module changes during Langflow dev:

Option 1: uvicorn --reload

cd src/backend
uvicorn langflow.main:app --reload --reload-dir ./base/langflow

Option 2: watchdog script

# watch_reload.py
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler
import subprocess
import time

class ReloadHandler(FileSystemEventHandler):
    def on_modified(self, event):
        if event.src_path.endswith(".py"):
            print(f"Changed: {event.src_path}")
            subprocess.run(["pkill", "-f", "langflow"])
            subprocess.Popen(["langflow", "run"])

observer = Observer()
observer.schedule(ReloadHandler(), "./base/langflow", recursive=True)
observer.start()

Option 3: entr (simple)

find src/backend -name "*.py" | entr -r langflow run

Option 4: Docker with mounted code

volumes:
  - ./src/backend:/app/src/backend
environment:
  LANGFLOW_AUTO_RELOAD: true

Fastest setup:

pip install watchdog
LANGFLOW_DEV=true langflow run

We do rapid Langflow development at RevolutionAI. The uvicorn --reload is cleanest for backend changes.

What's your dev setup — local or containerized?