Having pygls.protocol.json_rpc ValueError after updating to 2025.6.0 from 2025.4.0

[mondwan]

Type: Bug

Behaviour

Once updated the python extension from 2025.4.0 to 2025.6.0, the vscode python extension starts behaved strange.

Before the updates, there will be a tooltip for the documentation on whatever varaible, modules I highlighted. After the updates, it stopped working after a while.

It worked fine if I rollback to 2025.4.0. Is it because I am still using python3.8 instead?

Steps to reproduce:

1. Install the latest version of Python plugin
2. Mouse hover to the variable / module
3. There should be a tooltip showing the document of that variable / module
4. After a while, it stopped showing the doc, but keep showing Loading...

Diagnostic data

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

2025-05-13 10:22:46.286 [info] ERROR:pygls.protocol.json_rpc:Failed to handle request 80 textDocument/documentSymbol DocumentSymbolParams(text_document=TextDocumentIdentifier(uri='file:///home/vdc/....venv/lib/python3.8/site-packages/.../services.py'), work_done_token=None, partial_result_token=None)
Traceback (most recent call last):
  File "/home/vdc/.vscode-server/extensions/ms-python.python-2025.6.0-linux-x64/python_files/lib/jedilsp/jedi/cache.py", line 110, in wrapper
    return dct[key]
KeyError: ((), frozenset())

Extension version: 2025.6.0
VS Code version: Code 1.100.0 (19e0f9e681ecb8e5c09d8784acaa601316ca4571, 2025-05-07T12:48:53.763Z)
OS version: Windows_NT x64 10.0.22631
Modes:
Remote OS version: Linux x64 5.4.0-200-generic

• Python version (& distribution if applicable, e.g. Anaconda): 3.8.10
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Venv
• Value of the python.languageServer setting: Jedi

User Settings

languageServer: "Jedi"

testing
• promptToConfigure: false
• pytestEnabled: true
• autoTestDiscoverOnSaveEnabled: false

Installed Extensions

Extension Name	Extension Id	Version
black-formatter	ms-	2024.6.0
debugpy	ms-	2025.8.0
docker	doc	0.6.0
gitlab-workflow	Git	6.13.1
gitlens	eam	17.0.3
hcl	has	0.6.0
intellicode-api-usage-examples	Vis	0.2.9
isort	ms-	2025.0.0
js-debug	ms-	1.100.0
live-server	ms-	0.4.15
php-cs-fixer	jun	0.3.21
php-debug	xde	1.36.1
php-docblocker	nei	2.7.0
phpcs	ika	1.0.5
phpunit	ema	4.16.1
python	ms-	2025.6.0
remote-kubernetes	Okt	0.5.2
vscode-coverage-gutters	rya	2.13.0
vscode-docker	ms-	1.29.6
vscode-eslint	dba	3.0.10
vscode-intelephense-client	bme	1.14.4
vscode-js-profile-table	ms-	1.0.10
vscode-kubernetes-tools	ms-	1.3.23
vscode-openapi	42C	4.33.2
vscode-pylance	ms-	2025.4.1
vscode-yaml	red	1.18.0
vscodeintellicode	Vis	1.3.2

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-10850H CPU @ 2.70GHz (12 x 2712)
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)	31.78GB (18.43GB free)
Process Argv
Screen Reader	no
VM	0%

Item	Value
Remote	SSH: vm027943
OS	Linux x64 5.4.0-200-generic
CPUs	Intel(R) Xeon(R) Platinum 8462Y+ (2 x 0)
Memory (System)	7.76GB (6.03GB free)
VM	100%

[bytemain]

Encountered the same problem on remote ssh.

[karthiknadig]

@mondwan You are using Python3.8 which is deprecated. You need to pin the extension to older version for Python 3.8 support.

[mondwan]

@karthiknadig Before raising this ticket, I had considered that the issue might be version-related. However, since there was no version information included in the release log, I wasn't able to confirm this on my own. That’s why I proceeded to raise the ticket for clarification.

As a suggestion, it might be helpful to include version changes in future release logs to make it easier for others to identify such issues proactively.

Thanks again

[ZhengRui]

I am using Python 3.12, after update the extension to 2025.6.0, I also encounter the same issue. I had to change the python language server to Pylance for now. Upgrading Jedi is not working. Hovering on any variable or methods just shows "loading...".

logs:

2025-06-02 17:04:13.207 [info] WARNING:pygls.protocol.json_rpc:Cancel notification for unknown message id "2"
2025-06-02 17:04:13.243 [info] WARNING:pygls.protocol.json_rpc:Cancel notification for unknown message id "3"
2025-06-02 17:04:13.389 [info] semantic_tokens_full file:///Users/zerry/Work/Libs/ctc-forced-aligner/ctc_forced_aligner/align.py 
2025-06-02 17:04:13.397 [info] semantic_tokens_range file:///Users/zerry/Work/Libs/ctc-forced-aligner/ctc_forced_aligner/align.py 101:0-264:0
2025-06-02 17:04:13.500 [info] ERROR:pygls.protocol.json_rpc:Exception occurred for message "6": _pickle.UnpicklingError: unpickling stack underflow
NoneType: None
2025-06-02 17:04:13.500 [info] [Error - 5:04:13 PM] Request textDocument/semanticTokens/full failed.
2025-06-02 17:04:13.500 [info]   Message: _pickle.UnpicklingError: unpickling stack underflow
  Code: -32603 
[object Object]