Shift-Enter on long block inserts garbage into terminal, not my actual code

[arencambre]

Type: Bug

Behaviour

When I hit shift-enter on a single line of code, it always works fine. If I hit shift-enter on a long code block, such as if my cursor is on the def statement for a lengthy function, several lines get sent correctly, then some nonsense text eventually get sent to terminal instead of my actual code, and I get an error.

Steps to reproduce:

1. In a .py file, define a function using the def statement. It should have a fair number of lines. In my case, 42 lines.
2. With the cursor on the same line as the def statement, hit shift-enter.

Diagnostic data

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

There is no output. It's blank.

Extension version: 2026.0.0
VS Code version: Code 1.109.3 (Universal) (b6a47e94e326b5c209d118cf0f994d6065585705, 2026-02-12T17:54:48.470Z)
OS version: Darwin arm64 25.3.0
Modes:

• Python version (& distribution if applicable, e.g. Anaconda): 3.14.2
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): System
• Value of the python.languageServer setting: Default

User Settings

languageServer: "Pylance"

Installed Extensions

Extension Name	Extension Id	Version
chatgpt	ope	0.4.74
copilot-chat	Git	0.37.6
csdevkit	ms-	2.10.3
csharp	ms-	2.120.3
debugpy	ms-	2025.18.0
docker	doc	0.18.0
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
parallels-desktop	Par	1.5.11
powershell	ms-	2025.4.0
python	ms-	2026.0.0
quarto	qua	1.129.0
r	REd	2.8.6
r-syntax	REd	0.1.3
rainbow-csv	mec	3.24.1
remote-containers	ms-	0.442.0
remote-wsl	ms-	0.104.3
sort-lines	Tyr	1.12.0
vscode-containers	ms-	2.4.1
vscode-docker	ms-	2.0.0
vscode-dotnet-runtime	ms-	3.0.0
vscode-icalendar	af4	1.0.1
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-	2025.10.4
vscode-python-envs	ms-	1.16.0
vscode-xml	red	0.29.0

System Info

Item	Value
CPUs	Apple M4 Pro (14 x 2400)
GPU Status	2d_canvas: enabled GPU0: VENDOR= 0x106b [Google Inc. (Apple)], DEVICE=0x0000 [ANGLE (Apple, ANGLE Metal Renderer: Apple M4 Pro, Version 26.3 (Build 25D125))], DRIVER_VENDOR=Apple, DRIVER_VERSION=26.3 ACTIVE Machine model name: Mac Machine model version: 16.8 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: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	9, 8, 8
Memory (System)	48.00GB (0.07GB free)
Process Argv	--crash-reporter-id 59c64e8e-dcb7-475e-bb77-fc0f062aecee
Screen Reader	no
VM	0%

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cp_cls_c_1081:31454833
copilot-nes-oct-trt:31432596
ia-use-proxy-models-svc:31452481
nes-slash-models-on:31441832
nes-set-to-on:31441941
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c0ci8992_validated:31449878
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edit_mode_hidden:31461530
showstats:31457174
864ei723_large_tool_results_to_disk:31460878
notips:31457203
reg-2ge67640:31455970
nes-extended-on:31455476
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[arencambre]

problem_code.py is the code block that fails.

output.txt is the output in the terminal. Line 50 shows a break from reality. That is not code in my .py file. Where did that come from? Then line 51, we see that lines of code from the start of the function are inserted again.

This also happened on a separate .py file, completely unrelated to this one. For that separate file, I had to give up on using shift-enter, instead just running the entire .py file.

The commonality seems to be when shift-enter causes a few tens of lines of code to be sent to the terminal at once.