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Leftover process python_server.py with 100% after closing VSCode #25620
Description
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:
- Open up VSCode
- Open a python file
- Shift Enter in the python file to start a session and send some commands to the python REPL (e.g.
import pprint) - Close VSCode
- 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.languageServersetting: 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
Activity
hutch3232 commentedon Dec 6, 2025
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.pyscript uses 100% of my CPU. If you don'tkillthe 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 runningtop.hutch3232 commentedon Dec 16, 2025
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_headersvscode-python/python_files/python_server.py
Line 164 in 268e3c1
It breaks on
""and returns that tohandle_response. In that case, content length is 0 so it goes back toget_headers... Repeat.My approach raises an error if 0 bytes returned and handles separately. I should be able to test it sometime soon.
hutch3232 commentedon Jan 19, 2026
Anthony Kim (@anthonykim1) João Moreno (@joaomorenoalt) I saw the milestone was removed. Could we please get this issue slated for another milestone? This is a particularly pernicious issue. Thanks!
Fix python_server.py infinite loop on EOF (fixes #25620)
anthonykim1 commentedon Jan 22, 2026
Paul (@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.
Fix python_server.py infinite loop on EOF (fixes microsoft#25620) (mi…
anthonykim1 commentedon Jan 26, 2026
Fabian Bernhard (@fabern) Paul (@hutch3232) Could you guys please verify? In the latest pre-release of Python extension.
hutch3232 commentedon Jan 26, 2026
Hi Anthony Kim (@anthonykim1), thank you for fixing this! I just tested again and it does not occur in pre-release version.
fabern commentedon Jan 26, 2026
Great job Anthony Kim (@anthonykim1)!
This has solved it for me on two different systems.
I have just tested it with remote-SSH on an Ubuntu 22.04 and 24.04 instance: version 2026.0.0 still had a leftover process, whereas version 2026.1.2026012301 properly terminated the
python_server.py.Thanks a lot!