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bug: Flet & Qdrant: Created app runs a second blank window if qdrant vector store is initiated (non builded app dont show a second window) #5528
Description
Duplicate Check
- I have searched the opened issues and there are no duplicates
Describe the bug
Hello, i use qdrant vector store in a project, so far it runs fine, but once the app has been created using flet build, a second window without content opens when the vectore store is initialized. The window does not appear unless the app has been built and running with flet run or python main.py.
I cannot find any error messages in logs or console, and apart from the fact that the second window opens, the app runs without errors.
For better clarity, I have created the following small code example.
I don't understand why a second window opens and hope someone can help me out or fix this behavior.
Kind regards & thanks in advanced.
Code sample
Code
- main.py
import flet as ft from langchain_qdrant import QdrantVectorStore from qdrant_client import QdrantClient from qdrant_client.models import VectorParams, Distance from langchain_nomic import NomicEmbeddings def main(page: ft.Page): page.title = "Qdrant Vector DB TEST" embeddings = NomicEmbeddings( model="nomic-embed-text-v1.5", inference_mode="local", device="cpu", ) vector_client = QdrantClient(path="./qdrant") if not vector_client.collection_exists("langchain"): vector_client.create_collection( collection_name="langchain", vectors_config=VectorParams(size=768, distance=Distance.COSINE), ) def init_qdrant_vectore_store(e): vector_store = QdrantVectorStore( client=vector_client, collection_name="langchain", embedding=embeddings, ) text.value = "Qdrant-VectoreStore initiated..." text.update() return vector_store button = ft.FilledButton( "Init VectorStore", icon=ft.Icons.DELETE_FOREVER, on_click=init_qdrant_vectore_store, ) text = ft.Text("") page.add(button) page.add(text) page.update() ft.app(target=main)
- requirements.txt
flet
langchain_qdrant
qdrant_client
langchain_nomic
gpt4all
Build with: flet build macos --copyright "QdrantTest" --project "QdrantTest" --company "QdrantTest" --build-version 0.1'
To reproduce
- create main.py from example
- create requirements.txt from example
- create environment, install python modules, run and build app..
python -m venv venv
source venv/bin/activate
pip install -r requirements.txt
flet run (second window didnt appear)
flet build macos --copyright "QdrantTest" --project "QdrantTest" --company "QdrantTest" --build-version 0.1 (run the created app --> second window appear)
Expected behavior
App should not show a second blank window if qdrant vector store is initiated.
Screenshots / Videos
Captures
Operating System
macOS
Operating system details
15.6
Flet version
28.3.0
Regression
I'm not sure / I don't know
Suggestions
I dont know..
Logs
Logs
Additional details
Qdrant client didnt work in created (build) flet app on windows, app fails because of an import error from pywin32. So the example can only be testet on macos or linux.
Activity
ndonkoHenri commentedon Sep 4, 2026
This is now resolved in Flet 0.86.0 (#6662). Docs: https://flet.dev/docs/cookbook/multiprocessing
Packaged desktop apps now detect Python multiprocessing child invocations before Flutter starts and run them using a headless embedded Python interpreter, so helper processes no longer open additional Flet windows.
Despite appearances, Qdrant isn't the cause here.
QdrantVectorStore(...)validates the collection by embedding a dummy text, and that is the first call that actually runs local Nomic inference — which is why the window appeared at vector store initialization rather than at startup.nomicwraps that call in atqdmprogress bar,tqdmcreates amultiprocessing.RLock(), and that starts CPython's multiprocessing resource tracker, which re-executessys.executable. In a packaged appsys.executableis your app's own binary, so it launched a second, blank instance of the app. That also explains the two things that made this hard to diagnose: nothing was written to the logs, andflet run/python main.pywere unaffected, since theresys.executableis a real Python interpreter.Please upgrade to Flet 0.86.0 or newer and rebuild the macOS app — the second window should be gone with no changes to your code. The
if __name__ == "__main__":guard isn't required for this particular case, because the resource tracker never imports your app module, but it's worth adding if you later usemultiprocessingdirectly.Regarding the pywin32 import error you mention on Windows: that's a separate, unrelated issue.
qdrant-clientdepends onportalocker, which requirespywin32there. It's tracked in #5071 and #4737 — please follow up in those.Let know if you still face any issues.