Leftover process `python_server.py` with 100% after closing VSCode

[fabern]

Type: Bug

Behaviour

After closing VSCode, a leftover process remains running.

• This happens locally on my macOS (using about 2.4% of a CPU core):
  /Users/faber/.vscode/extensions/ms-python.python-2025.18.0-darwin-arm64/python_files/python_server.py

• as well as vis SSH Remote extension on a Linux cluster (using 100% of a CPU core [!]):
  /bin/python /storage/homefs/fb24k097/.vscode-server/extensions/ms-python.python-2025.18.0-linux-x64/python_files/python_server.py

Steps to reproduce:

1. Open up VSCode
2. Open a python file
3. Shift Enter in the python file to start a session and send some commands to the python REPL (e.g. import pprint)
4. Close VSCode
5. Check running processes with htop

Diagnostic data

2025-12-03 11:28:43.148 [info] Experiment 'pythonSurveyNotification' is active
2025-12-03 11:28:43.485 [info] Native locator: Refresh started
2025-12-03 11:28:44.296 [info] > pyenv which python
2025-12-03 11:28:44.296 [info] cwd: .
2025-12-03 11:28:46.936 [info] Native locator: Refresh finished in 3452 ms
2025-12-03 11:28:49.055 [info] Starting Pylance language server.
2025-12-03 11:28:49.058 [info] Active interpreter [/storage/homefs/fb24k097/GitHub/fabern/aggregate-ERA5Land-daily]: /storage/homefs/fb24k097/GitHub/fabern/aggregate-ERA5Land-daily/.venv/bin/python
2025-12-03 11:29:00.927 [info] > /bin/python ~/.vscode-server/extensions/ms-python.python-2025.18.0-linux-x64/python_files/normalizeSelection.py

Extension version: 2025.18.0
VS Code version: Code 1.106.3 (bf9252a2fb45be6893dd8870c0bf37e2e1766d61, 2025-11-25T22:28:18.024Z)
OS version: Darwin arm64 24.6.0
Modes:

• Python version (& distribution if applicable, e.g. Anaconda): 3.13.7.final.0
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): System
• Value of the python.languageServer setting: Default

User Settings

languageServer: "Pylance"

Installed Extensions

Extension Name	Extension Id	Version
cmake-tools	ms-	1.21.36
copilot-chat	Git	0.33.3
cpptools	ms-	1.28.3
cpptools-extension-pack	ms-	1.3.1
cpptools-themes	ms-	2.0.0
debugpy	ms-	2025.16.0
fortran-ls	han	0.6.2
github-local-actions	San	1.2.5
gitlens	eam	17.7.1
js-debug	ms-	1.105.0
js-debug-companion	ms-	1.1.3
language-julia	jul	1.158.2
linter-gfortran	for	3.4.2025101501
makefile-tools	ms-	0.12.17
python	ms-	2025.18.0
r	REd	2.8.6
r-syntax	REd	0.1.3
remote-explorer	ms-	0.5.0
remote-ssh	ms-	0.120.0
remote-ssh-edit	ms-	0.87.0
vscode-js-profile-table	ms-	1.0.10
vscode-latex	mat	1.3.0
vscode-lldb	vad	1.11.5
vscode-peacock	joh	4.2.2
vscode-pylance	ms-	2025.10.3
vscode-python-envs	ms-	1.12.0

System Info

Item	Value
CPUs	Apple M4 (10 x 2400)
GPU Status	2d_canvas: enabled direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: enabled_on trees_in_viz: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	5, 3, 3
Memory (System)	16.00GB (0.18GB free)
Process Argv	--crash-reporter-id 08ffa65a-dbb4-4eb7-984b-8800380a22c8
Screen Reader	no
VM	0%

A/B Experiments

vsliv368cf:30146710
pythonvspyt551:31249599
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31334701
aj953862:31281341
nes-set-on:31351930
6abeh943:31336334
envsactivate1:31353494
cloudbuttont:31379625
todos-1:31405332
qwen_all_req:31402696
3efgi100_wstrepl:31403338
trigger-command-fix:31379601
auto_model_enabled:31385282
use-responses-api:31390855
ddidtcf:31399634
je187915:31407605
ec5jj548:31422691
copilot-nes-oct-t:31418199
terminalsuggestenabled:31426255
cmp-ext-treat:31426748
cp_cls_c_966_ss:31426491
defaultvisibility:31426295
expandedtokens:31427242
copilot6169-t1000:31426764
c0683394:31419495
g0h3h215:31426582
478ah919:31426797
ge8j1254_inline_auto_hint_haiku:31426733
b53de340:31426751
a5gib710:31426879
38bie571_auto:31426784

[hutch3232]

I can confirm this is happening to me as well on my M1 MacBook Air. Interestingly, I don't even have the SSH Remote Extension installed. After using the Native REPL, when I close VS Code that same python_server.py script uses 100% of my CPU. If you don't kill the process, and then open VS Code again and repeat the steps, you'll have a second process competing for 100% of CPU. I was wondering why my battery was draining and my laptop was getting very hot. Found the process when running top.

[hutch3232]

I looked into this a bit. Haven't made the PR yet because I haven't gotten to do real testing of this yet. https://github.com/microsoft/vscode-python/compare/main...hutch3232:vscode-python:leftover-py-process?expand=1

This issue is that it's getting stuck in get_headers

vscode-python/python_files/python_server.py

Line 164 in 268e3c1

def get_headers():

It breaks on "" and returns that to handle_response. In that case, content length is 0 so it goes back to get_headers... Repeat.

My approach raises an error if 0 bytes returned and handles separately. I should be able to test it sometime soon.

[hutch3232]

@anthonykim1 @joaomorenoalt I saw the milestone was removed. Could we please get this issue slated for another milestone? This is a particularly pernicious issue. Thanks!

[anthonykim1]

@hutch3232 Yeap, PR in progress, thanks!
Will let you know once its out in pre-release so we can have folks test this out before it goes into release.