Slow virtualenv activation in terminal may cause wrong command execution and potential data loss

[Ige-kun]

Type: Bug

Behaviour

When opening a terminal, the Python virtualenv activation command (e..g source /path/to/.venv/bin/activate) is issued too late. Most of the time, I’ve already started typing another command before activation occurs. As a result, the activation command is appended to whatever I was typing, and the combined text is executed as-is. This causes the virtualenv activation to fail, and the command I was entering is also lost.

This seems potentially dangerous, because it can result in excuting commands I never intended to run. For example, if I type rm and the activation triggers right after, the executed command becomes: rm source /path/to/.venv/bin/activate. This would obviously delete the listed paths.

This appears to be the same issue described in the now-closed #15719 (2021). That issue includes a video that already demonstrates the problem well, so I haven’t recorded a new one. Here's the video from the old issue:

Peek.19-03-2021.07-50.mp4

The problem seems to be shell-agnostic: I can reproduce it in both Bash and Fish. It’s also not caused by my custom shell configuration, since it still happens when running Bash with --noprofile --norc.

Steps to reproduce:

1. Open a new internal terminal (panel or editor area)
2. Start typing a command immediately
3. Notice that your input is appended with the virtualenv command and executed together

Diagnostic data

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

2025-09-04 13:19:15.065 [info] > pyenv which python
2025-09-04 13:19:15.066 [info] cwd: .
2025-09-04 13:19:28.051 [info] Active interpreter [/home/ige/repos/pythontest]:  /home/ige/repos/pythontest/.venv/bin/python
2025-09-04 13:19:30.733 [info] Starting Pylance language server.
2025-09-04 13:19:37.000 [info] Send text to terminal: source /home/ige/repos/pythontest/.venv/bin/activate

Extension version: 2025.12.0
VS Code version: Code 1.103.1 (360a4e4fd251bfce169a4ddf857c7d25d1ad40da, 2025-08-12T16:25:40.542Z)
OS version: Linux x64 6.15.9-201.fc42.x86_64+debug
Modes:
Remote OS version: Linux x64 6.15.9-201.fc42.x86_64+debug

• Python version: 3.13.3
• Type of virtual environment used: venv
• Value of the python.languageServer setting: Default

User Settings

languageServer: "Pylance"

testing
• pytestArgs: "<placeholder>"
• pytestEnabled: true
• pytestPath: "<placeholder>"

experiments
• enabled: false
• optOutFrom: ["pythonTerminalEnvVarActivation"]

Installed Extensions

Extension Name	Extension Id	Version
Bookmarks	ale	13.5.0
cloudcode	goo	2.36.0
code-spell-checker	str	4.2.6
copilot	Git	1.364.0
copilot-chat	Git	0.30.3
debugpy	ms-	2025.10.0
even-better-toml	tam	0.21.2
geminicodeassist	goo	2.47.0
gitlab-workflow	Git	6.40.1
gitlens	eam	17.4.1
js-debug	ms-	1.102.0
markdown-all-in-one	yzh	3.6.3
python	ms-	2025.12.0
ruff	cha	2025.24.0
shellcheck	tim	0.38.3
vscode-js-profile-table	ms-	1.0.10
vscode-kubernetes-tools	ms-	1.3.26
vscode-markdownlint	Dav	0.60.0
vscode-pylance	ms-	2025.7.1
vscode-python-envs	ms-	1.2.0
vscode-yaml	red	1.18.0

System Info

Item	Value
CPUs	AMD Ryzen 7 PRO 4750U with Radeon Graphics (16 x 1409)
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: disabled_off trees_in_viz: disabled_off video_decode: enabled video_encode: disabled_software vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: disabled_off webnn: disabled_off
Load (avg)	6, 6, 5
Memory (System)	26.49GB (6.57GB free)
Process Argv	--new-window --crash-reporter-id b1a9997c-d502-48ce-9353-1ad864d1ffab
Screen Reader	no
VM	0%
DESKTOP_SESSION	gnome
XDG_CURRENT_DESKTOP	GNOME
XDG_SESSION_DESKTOP	gnome
XDG_SESSION_TYPE	wayland

Item	Value
Remote	Dev Container: zeevending-support-backend @ unix:///run/user/1000/podman/podman.sock
OS	Linux x64 6.15.9-201.fc42.x86_64+debug
CPUs	AMD Ryzen 7 PRO 4750U with Radeon Graphics (16 x 3217)
Memory (System)	26.49GB (6.56GB free)
VM	0%

A/B Experiments

vsliv368cf:30146710
vswsl492:30256859
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
996jf627:31283433
pythonrdcb7:31342333
usemplatestapi:31297334
747dc170:31275177
aj953862:31281341
nesew2to5:31336538
agentclaude:31350858
nes-set-on:31351930
testaa123cf:31335227
onetestforazureexp:31335613
6abeh943:31336334
0927b901:31350571
custommodel2t:31371781
45650338:31358607
0cj2b977:31352657
cloudbuttonc:31374191
retryenabled:31370050
todos-0:31378732
search_len_ctrl:31378778
3efgi100_wstrepl:31374188

[danielpassy]

Extra issue with that:

Sometimes I run something with run and debug
It opens a new console, insert the command but then a env activation stops the command.

launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Django Debug",
      "type": "debugpy",
      "request": "launch",
      "program": "${workspaceFolder}/manage.py",
      "args": [
        "runserver",
        "0.0.0.0:8000"
      ],
      "django": true,
      "justMyCode": false,
      "env": {
        "MANAGE_PY_PATH": "manage.py"
      },
    },
  ]
}

Results:

The debugger hangs for quite a while and then

The workaround is quite simple, bug really annoying, stop the debugger and let this shell open

[anthonykim1]

Make sure you have environment extension enabled and set python-envs.terminal.autoActivationType to shellStartup.
Try with vscode insiders https://code.visualstudio.com/insiders/ and latest pre-release of environment extension.

If you do shell startup, you dont have to rely on the order of commands being sent to terminal.