Venv not being activated in terminal

[AWH1122]

Type: Bug

Behaviour

When using a venv, if I run a file using the run button provided by VS Code, the correct Python binary is used. If I go to the terminal and run which python I can see that the active binary is /usr/bin/python.

This issue does not seem to occur when using conda environments. I am using wsl with zsh and oh my zsh. I can see that oh my zsh is showing that the environment is active even though it isn't. Not sure if this is helpful or not.

Steps to reproduce:

1. Create a venv
2. Select venv as the active interpreter
3. Open a new terminal
4. Run which python
5. Observe venv has not been automatically activated

Diagnostic data

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

N/A

Extension version: 2025.0.0
VS Code version: Code 1.97.1 (e249dada235c2083c83813bd65b7f4707fb97b76, 2025-02-10T13:13:58.153Z)
OS version: Windows_NT x64 10.0.22631
Modes:
Remote OS version: Linux x64 5.15.167.4-microsoft-standard-WSL2

• Python version (& distribution if applicable, e.g. Anaconda): 3.13.1
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Venv
• Value of the python.languageServer setting: Default

User Settings

languageServer: "Pylance"

Installed Extensions

Extension Name	Extension Id	Version
copilot	Git	1.270.0
copilot-chat	Git	0.24.0
cpptools	ms-	1.23.6
datawrangler	ms-	1.18.1
debugpy	ms-	2025.0.0
intellicode-api-usage-examples	Vis	0.2.9
js-debug	ms-	1.97.1
jupyter	ms-	2025.1.0
jupyter-renderers	ms-	1.1.0
latex-workshop	Jam	10.7.5
path-intellisense	chr	2.10.0
python	ms-	2025.0.0
resourcemonitor	mut	1.0.7
ruff	cha	2025.8.0
vscode-clangd	llv	0.1.33
vscode-js-profile-table	ms-	1.0.10
vscode-jupyter-cell-tags	ms-	0.1.9
vscode-jupyter-slideshow	ms-	0.1.6
vscode-pylance	ms-	2025.2.1
vscodeintellicode	Vis	1.3.2

System Info

Item	Value
CPUs	AMD Ryzen 9 3900X 12-Core Processor (24 x 3793)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on 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: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	31.92GB (15.77GB free)
Process Argv	--crash-reporter-id 672d1eda-f4ea-4625-a978-6966492cb88b
Screen Reader	no
VM	0%

Item	Value
Remote	WSL: Ubuntu
OS	Linux x64 5.15.167.4-microsoft-standard-WSL2
CPUs	AMD Ryzen 9 3900X 12-Core Processor (24 x 0)
Memory (System)	15.58GB (13.32GB free)
VM	0%

A/B Experiments

vsliv368:30146709
vspor879:30202332
vspor708:30202333
vspor363:30204092
pythonvspyt551cf:31179979
vscod805cf:30301675
binariesv615:30325510
py29gd2263:31024239
c4g48928:30535728
azure-dev_surveyone:30548225
962ge761:30959799
h48ei257:31000450
pythontbext0:30879054
cppperfnew:31000557
dwnewjupytercf:31046870
nativerepl1:31139838
pythonrstrctxt:31112756
nativeloc2:31192216
iacca1:31171482
5fd0e150:31155592
dwcopilot:31170013
stablechunks:31184530
6074i472:31201624
5a9hg449:31230677
9064b325:31222308
copilot_t_ci:31222730
jda6j935:31233686

[karthiknadig]

Try adding this to your User settings.json and reload:

"python.experiments.optOutFrom": ["pythonTerminalEnvVarActivation"]

[AWH1122]

Thank you, this seems have fixed the issue. What is this experiment doing?

[karthiknadig]

The goal of the experiment is to avoid activate the environment without sending source activate to the terminal. The reason is, in many cases sending the command to terminal can collide with user typing in terminal, or multiple extensions attempting to send a command. Like Git extension could send a command while Python extension also does it, it can collide and fail.