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Venv activation command leaks into stdin when running tasks on Windows #25744
Description
Type: Bug
Behaviour
When running a VS Code task, the venv activation command (& c:/path/to/.venv/Scripts/Activate.ps1) leaks into stdin instead of being executed as a shell command. This causes any input() call or stdin-reading command to receive the activation path as input, breaking interactive prompts.
This is probably a regression of #9374.
Steps to reproduce:
- Create a workspace with a Python venv (I used
uv venv .venv) - Select the venv interpreter in VS Code
- Create this debug script (
debug_stdin_leak.py):
import msvcrt
import sys
print("Checking stdin buffer for leaked data...")
leaked_chars = []
while msvcrt.kbhit():
char = msvcrt.getch()
leaked_chars.append(char)
if leaked_chars:
leaked_data = b"".join(leaked_chars).decode("utf-8", errors="replace")
print(f"\n❌ STDIN LEAK DETECTED!")
print(f"Leaked data ({len(leaked_chars)} chars):")
print(f" {repr(leaked_data)}")
else:
print("\n✅ No data leaked into stdin buffer.")- Create a task in
.vscode/tasks.json:
{
"label": "Debug: Check stdin leak",
"type": "shell",
"command": "${workspaceFolder}/.venv/Scripts/python.exe",
"args": ["debug_stdin_leak.py"],
"presentation": {
"reveal": "always",
"panel": "new",
"focus": true
},
"problemMatcher": []
}- Run the task (make sure to close any existing terminals first so a fresh one is created)
Expected: stdin should be empty
Actual:
Checking stdin buffer for leaked data...
❌ STDIN LEAK DETECTED!
Leaked data (79 chars):
'& c:/Users/.../.venv/Scripts/Activate.ps1\r'Environment:
OS: Windows 11
Shell: PowerShell
venv created with: uv
Workaround: Flush stdin before reading input using msvcrt.kbhit() / msvcrt.getch()
Diagnostic data
Details
2026-01-21 11:35:56.908 [info] Native locator: Refresh started
2026-01-21 11:35:56.999 [info] Native locator: Refresh finished in 673 ms
2026-01-21 11:35:57.437 [info] Native locator: Refresh started
2026-01-21 11:35:57.447 [info] Skipping ActivatedEnv Detection: process.env.VSCODE_CLI !== '1'
2026-01-21 11:35:57.478 [info] Python interpreter path: .\.venv\Scripts\python.exe
2026-01-21 11:36:01.339 [info] > pyenv which python
2026-01-21 11:36:01.340 [info] cwd: .
2026-01-21 11:36:02.389 [info] > conda info --json
2026-01-21 11:36:03.686 [info] Native locator: Refresh finished in 6249 ms
2026-01-21 11:36:07.857 [info] Starting Pylance language server.
2026-01-21 11:43:34.156 [info] Send text to terminal: & C:/Users/.../.venv/Scripts/Activate.ps1
Extension version: 2026.0.0
VS Code version: Code 1.108.1 (585eba7c0c34fd6b30faac7c62a42050bfbc0086, 2026-01-14T14:55:44.241Z)
OS version: Windows_NT x64 10.0.22631
Modes:
- Python version (& distribution if applicable, e.g. Anaconda): 3.12.9
- Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Venv
- Value of the
python.languageServersetting: Pylance
User Settings
languageServer: "Pylance"
Installed Extensions
| Extension Name | Extension Id | Version |
|---|---|---|
| amazon-q-vscode | ama | 1.107.0 |
| autodocstring | njp | 0.6.1 |
| aws-toolkit-vscode | ama | 3.93.0 |
| bash-ide-vscode | mad | 1.43.0 |
| black-formatter | ms- | 2025.2.0 |
| datawrangler | ms- | 1.24.0 |
| debugpy | ms- | 2025.19.2026011901 |
| docker | doc | 0.18.0 |
| even-better-toml | tam | 0.21.2 |
| git-graph | mhu | 1.30.0 |
| gitblame | wad | 11.2.0 |
| gitlens | eam | 17.9.0 |
| go | gol | 0.52.1 |
| js-debug | ms- | 1.105.0 |
| js-debug-companion | ms- | 1.1.3 |
| jupyter | ms- | 2025.9.1 |
| jupyter-keymap | ms- | 1.1.2 |
| jupyter-renderers | ms- | 1.3.0 |
| markdown-pdf | yza | 1.5.0 |
| tom | 1.2.2 | |
| powershell | ms- | 2025.4.0 |
| prettier-sql-vscode | inf | 1.6.0 |
| pylint | ms- | 2025.2.0 |
| python | ms- | 2026.0.0 |
| remote-containers | ms- | 0.437.0 |
| remote-explorer | ms- | 0.5.0 |
| remote-ssh | ms- | 0.122.0 |
| remote-ssh-edit | ms- | 0.87.0 |
| remote-wsl | ms- | 0.104.3 |
| ruff | cha | 2026.34.0 |
| rust-analyzer | rus | 0.3.2761 |
| rust-syntax | dus | 0.6.1 |
| sqltools | mtx | 0.28.5 |
| sqltools-driver-mysql | mtx | 0.6.6 |
| sqltools-driver-pg | mtx | 0.5.7 |
| vscode-containers | ms- | 2.3.0 |
| vscode-github-actions | git | 0.29.1 |
| vscode-icons | vsc | 12.17.0 |
| vscode-js-profile-table | ms- | 1.0.10 |
| vscode-jupyter-cell-tags | ms- | 0.1.9 |
| vscode-jupyter-slideshow | ms- | 0.1.6 |
| vscode-nushell-lang | The | 1.10.0 |
| vscode-pylance | ms- | 2025.10.4 |
| vscode-python-envs | ms- | 1.17.10151015 |
| vscode-typescript-next | ms- | 6.0.20260120 |
| vscode-xml | red | 0.29.0 |
Activity
d-shehu commentedon Feb 5, 2026
This has been driving me nuts. Even if the venv command is in a script within a container that gets launched via tasks.json, I still get the contaminated stdin.
If I run the same command as tasks.json on the CLI and then attach from VScode it works fine. It also seems to occur on Linux irrespective of using shell or process, invoking the script directly or via bash -lc, etc.
anthonykim1 commentedon Mar 13, 2026
The activation command leaking into stdin is caused by the legacy command-based terminal activation mechanism, which sends the activate command as typed text via
sendText.Please try migrating to the Python Environments extension's
shellStartupactivation, which injects activation into your shell profile instead — no commands are sent via stdin:python-envs.terminal.autoActivationTypetoshellStartupin your settings"python.useEnvironmentsExtension": trueto your settings.jsonSee more details here: https://code.visualstudio.com/updates/v1_106#_consolidated-shell-integration-timeout-setting
Also see #25291 for the full migration guide. Please let us know if this resolves the issue!
samuelefiorini commentedon Mar 24, 2026
Thanks Anthony Kim (@anthonykim1), following your suggestion resolved the issue. No more leak: