Python Extension crashing with logs of `pickle.UnpicklingError`.

[ChrisGy]

Type: Bug

Behaviour

When running the Python extension in an SSH remote host (a Raspberry Pi 5 running Debian 12), I am unable to do many extension related functionality. Code Intelligence does not work. Line suggestions or variable suggestions do not work either. Symbol rename (with F2) does not work. The extension output is filled with errors related to the pickle module, something about missing keys. The missing key seems to change upon every Window reload. The last occurence before this report was key 'n' not found.

The environment is a Python virtual environment (venv) based on Python 3.11.2.
The Microsoft Python extension version is 2025.10.1.
I have tried deleting the entire vscode-server folder from the Remote host and having everything reinstalled. I have updated VSCode itself. I have rebooted window several times. I have also restarted the remote host itself. The issue keeps occuring right upon starting VSCode. Log of the extension output from the very start of a freshly-loaded window is attached below.

Steps to reproduce:

1. Open any Python file in the Remote SSH mode.
2. Attempt a symbol rename (using F2). This takes forever.
3. Observe Python extension output.

Diagnostic data

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

2025-07-31 13:53:57.561 [info] Extension host with pid 28578 started
2025-07-31 13:53:57.614 [info] Lock '/home/<myUserName>/.vscode-server/data/User/workspaceStorage/731b43754a5ef6832150daecc16c5f1b/vscode.lock': Lock acquired.
2025-07-31 13:53:58.088 [info] ExtensionService#_doActivateExtension vscode.emmet, startup: false, activationEvent: 'onLanguage'
2025-07-31 13:53:58.093 [info] ExtensionService#_doActivateExtension vscode.git-base, startup: false, activationEvent: '*', root cause: vscode.git
2025-07-31 13:53:58.094 [info] ExtensionService#_doActivateExtension ms-python.python, startup: false, activationEvent: 'onLanguage:python', root cause: ms-python.autopep8
2025-07-31 13:53:59.680 [info] ExtensionService#_doActivateExtension vscode.git, startup: false, activationEvent: '*'
2025-07-31 13:53:59.681 [info] ExtensionService#_doActivateExtension vscode.github, startup: false, activationEvent: '*'
2025-07-31 13:54:00.237 [info] ExtensionService#_doActivateExtension ms-python.autopep8, startup: false, activationEvent: 'onLanguage:python'
2025-07-31 13:54:00.238 [info] ExtensionService#_doActivateExtension ms-python.debugpy, startup: false, activationEvent: 'onLanguage:python'
2025-07-31 13:54:01.291 [info] Eager extensions activated
2025-07-31 13:54:01.292 [info] ExtensionService#_doActivateExtension vscode.debug-auto-launch, startup: false, activationEvent: 'onStartupFinished'
2025-07-31 13:54:01.294 [info] ExtensionService#_doActivateExtension vscode.merge-conflict, startup: false, activationEvent: 'onStartupFinished'
2025-07-31 13:54:01.295 [info] ExtensionService#_doActivateExtension GitHub.copilot, startup: false, activationEvent: 'onStartupFinished'
2025-07-31 13:54:01.296 [info] ExtensionService#_doActivateExtension GitHub.copilot-chat, startup: false, activationEvent: 'onStartupFinished'
2025-07-31 13:54:22.348 [error] [ms-python.python] provider FAILED
2025-07-31 13:54:22.349 [error] Error: _pickle.UnpicklingError: unexpected MARK found
    at ae (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1996792)
    at oe (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1994752)
    at Immediate.<anonymous> (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1991046)
    at processImmediate (node:internal/timers:485:21)
2025-07-31 13:54:22.357 [error] [ms-python.python] provider FAILED
2025-07-31 13:54:22.358 [error] Error: _pickle.UnpicklingError: unexpected MARK found
    at ae (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1996792)
    at oe (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1994752)
    at Immediate.<anonymous> (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1991046)
    at processImmediate (node:internal/timers:485:21)
2025-07-31 13:54:22.360 [error] [ms-python.python] provider FAILED
2025-07-31 13:54:22.360 [error] Error: _pickle.UnpicklingError: unexpected MARK found
    at ae (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1996792)
    at oe (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1994752)
    at Immediate.<anonymous> (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1991046)
    at processImmediate (node:internal/timers:485:21)
2025-07-31 13:55:51.839 [error] [ms-python.python] provider FAILED
2025-07-31 13:55:51.840 [error] Error: _pickle.UnpicklingError: unexpected MARK found
    at ae (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1996792)
    at oe (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1994752)
    at Immediate.<anonymous> (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1991046)
    at processImmediate (node:internal/timers:485:21)
2025-07-31 13:55:52.460 [error] [ms-python.python] provider FAILED
2025-07-31 13:55:52.462 [error] Error: _pickle.UnpicklingError: unexpected MARK found
    at ae (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1996792)
    at oe (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1994752)
    at Immediate.<anonymous> (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1991046)
    at processImmediate (node:internal/timers:485:21)
2025-07-31 13:55:54.358 [error] [ms-python.python] provider FAILED
2025-07-31 13:55:54.359 [error] Error: _pickle.UnpicklingError: unexpected MARK found
    at ae (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1996792)
    at oe (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1994752)
    at Immediate.<anonymous> (/home/<myUserName>/.vscode-server/extensions/ms-python.python-2025.10.1-linux-arm64/out/client/extension.js:2:1991046)
    at processImmediate (node:internal/timers:485:21)

Extension version: 2025.10.1
VS Code version: Code 1.102.3 (488a1f239235055e34e673291fb8d8c810886f81, 2025-07-29T03:00:23.339Z)
OS version: Windows_NT x64 10.0.26100
Modes:
Remote OS version: Linux arm64 6.12.20+rpt-rpi-v8

• Python version (& distribution if applicable, e.g. Anaconda): 3.11.2
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Venv
• Value of the python.languageServer setting: Default

User Settings

languageServer: "Jedi"

Installed Extensions

Extension Name	Extension Id	Version
autopep8	ms-	2025.2.0
copilot	Git	1.350.0
copilot-chat	Git	0.29.1
debugpy	ms-	2025.10.0
doxdocgen	csc	1.4.0
js-debug	ms-	1.102.0
python	ms-	2025.10.1
vscode-js-profile-table	ms-	1.0.10
vscode-markdownlint	Dav	0.60.0

System Info

Item	Value
CPUs	AMD Ryzen 5 7530U with Radeon Graphics (12 x 1996)
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)	22.83GB (9.40GB free)
Process Argv	--crash-reporter-id 6e5b78a7-5e42-423c-b9dd-fbc66c53d348
Screen Reader	no
VM	0%

Item	Value
Remote	SSH: mpetproduction01-onsite
OS	Linux arm64 6.12.20+rpt-rpi-v8
CPUs	Cortex-A72 (4 x 1800)
Memory (System)	7.63GB (6.28GB free)
VM	0%

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[eleanorjboyd]

hm this is interesting I haven't seen this before. To confirm linux arm64 is the right OS type corrrect?

[ChrisGy]

Hi @eleanorjboyd,

Yes this is linux arm64. But I've figured that this only happens when Jedi is the language server. I installed Pylance and the issue went away. It returns when I manually switch language server to Jedi with .vscode/settings.json.

Thank you.

[eleanorjboyd]

are you able to move forward with Pylance? I may be able to investigate more if you need Jedi

[ChrisGy]

Thank you very much for the offer, but I'm okay using Pylance. I only uninstalled it because of "too much linting" but I can live with it.
Thank you very much.

[0x9fff00]

I also have this issue, it seems to be caused by pappasam/jedi-language-server#340

[Root-Core]

CC #25060 - Jedi works with the extension on version 2025.4.0