Shift+Enter progressively changes indentation when running Python code in the terminal

[CardonaEA]

Type: Bug

Summary

Regression in Python extension 2026.6.0: using Shift+Enter to run Python code from the editor in the Python terminal progressively increases indentation in multiline code.

The source code in the editor is correctly indented; the indentation is changed in the code sent to the terminal.

This workflow works correctly with Python extension 2026.4.0. Downgrading from 2026.6.0 to 2026.4.0 resolves the issue.

Minimal reproduction

Source:

plane_range = [20, 50]
n_planes = 450
valid_plane_range = (
    isinstance(plane_range, (tuple, list))
    and len(plane_range) == 2
    and all(isinstance(plane, int) for plane in plane_range)
    and all(0 <= plane < n_planes for plane in plane_range)
)

After pressing Shift+Enter, the terminal receives progressively increasing indentation:

>>> valid_plane_range = (
...     isinstance(plane_range, (tuple, list))
...         and len(plane_range) == 2
...             and all(isinstance(plane, int) for plane in plane_range)
...                 and all(0 <= plane < n_planes for plane in plane_range)
...                 )

With a larger selection, this eventually results in:

IndentationError: unexpected indent

To reproduce IndentationError: unexpected indent with a minimal larger block:

def function_test(arr=np.zeros((450, 1200, 1200, 2))):
    plane_range = [20, 50]
    n_planes = arr.shape[0]
    valid_plane_range = (
        isinstance(plane_range, (tuple, list))
        and len(plane_range) == 2
        and all(isinstance(plane, int) for plane in plane_range)
        and all(0 <= plane < n_planes for plane in plane_range)
    )
    return

Additional observation

Whenever I observe issues with sending code from the editor to the terminal after an extension update — including this issue and previous, related but not identical issues — the Python prompt itself (>>>) appears pink/violet instead of the usual neutral white in the terminal.

Expected behavior

Shift+Enter should send the selected/current Python code to the terminal without changing its indentation.

Regression

• Working: ms-python.python 2026.4.0
• Broken: ms-python.python 2026.6.0
• Observed: September 30, 2026

Environment

• OS: Windows
• VS Code: 1.139.1
• Python: Python 3.13.7

Extension version: 2026.6.0
VS Code version: Code 1.139.1 (04c0d99f4fb0d8afe6ce4f0c58e31e183ac3e4b1, 2026-09-25T03:40:57Z)
OS version: Windows_NT x64 10.0.26200
Modes:

• Python version (& distribution if applicable, e.g. Anaconda): 3.13.7
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): System
• Value of the python.languageServer setting: Default

User Settings

languageServer: "Pylance"

terminal
• activateEnvironment: false

Installed Extensions

Extension Name	Extension Id	Version
debugpy	ms-	2026.6.0
js-debug	ms-	1.117.0
js-debug-companion	ms-	1.1.3
jsts-chat-features	Typ	0.0.4
markdown-pdf	yza	2.2.0
python	ms-	2026.6.0
vscode-js-profile-table	ms-	1.0.11
vscode-pylance	ms-	2026.4.1
vscode-python-envs	ms-	1.38.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) Ultra 9 185H (22 x 3072)
GPU Status	2d_canvas: enabled GPU0: VENDOR= 0x8086, DEVICE=0x7d55 [Intel(R) Arc(TM) Pro Graphics], DRIVER_VENDOR=Intel, DRIVER_VERSION=32.0.101.8860 ACTIVE GPU1: VENDOR= 0x10de, DEVICE=0x2838 [NVIDIA RTX 3000 Ada Generation Laptop GPU], DRIVER_VERSION=32.0.15.9641 GPU2: VENDOR= 0x1414, DEVICE=0x008c [Microsoft Basic Render Driver], DRIVER_VERSION=10.0.26100.9278 Machine model name: Machine model version: 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 webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	63.45GB (44.16GB free)
Process Argv	--crash-reporter-id fb04d34d-bbc9-42e1-af06-0120fbec62ef
Screen Reader	no
VM	0%

A/B Experiments

vsliv368cf:30146710
binariesv615:30325510
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dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31463988
aj953862:31281341
envsactivate1:31551504
cloudbuttont:31379625
3efgi100_wstrepl:31403338
ec5jj548:31422691
cp_cls_t_966_ss:31526232
4je02754:31466945
8hhj4413:31478653
cp_cls_t_1081:31454832
conptydll_true:31498968
e9c30283:31461165
46204921:31447328
ei9d7968:31496641
chat:31457767
23c7c724:31520045
ddid_t:31478206
hmra_i5g22:31518061
7df3h592:31512476
cp_cls_t_1082:31535311
logging_enabled_new:31498466
j0d79568:31499440
jb_cp_cls_t_632:31543129
56dj4588:31512888
32d76977:31512328
ha629193:31508444
jh5f2457_c:31540921
jbcp_cls_pctr_t:31531130
cp_intellij_t_nes:31548657
ahp-both-windows:31556933
ihg5j128:31534457
9gg7f176:31542112
enable_editor_pane_layout:31569726
allow-none:31555437
ac562147:31564510
c7c27ce7:31554789
1h923230:31564177
treatment-23-1:31555779
unuse_dynamic_mcp:31555281
0d8dfbc3:31570291
a1hcc538:31559322
nemo-v2:31565334
0c1h4866:31566224
session-mark-done:31591648
5b8j3302:31564601
autotiers:31584978
mangle-name-control:31572633
allow-signed-out:31592042
b17abb00-cfec-4134-90da-ee5e32ce4426:31589248
intellij_nes_preview_t:31580086
39a5d156:31574986
2bfb8b39:31585911
outline:31581109
links-control:31587703
aw-autom-on:31583758
revealsession_treatment_7ed7e840:31582194
usage_tips_endabled_0911:31587631
7g328426_fixed:31584544
codex-agent-host-stable-control:31590621
66c8a39e-e7a5-4b4c-a3c0-41b161c795c4:31586113
sessioninlinediffenabled_disabled:31587634
welcomesignin9359t:31590011
e6882f69-f5cc-4f90-9073-69a4ca3e50ea:31589215
ca19f5eb-b04f-4f52-8e6b-9f6927d4e0dc:31589210

[edvilme]

Related python/cpython#126449

[edvilme]

Thanks for bringing this to our attention. PyREPL was reactivated in the latest release, which is why you are seeing the colored prompt. This is a bug where the paste markers were not included when executing code in the terminal.

We are currently working on a fix, but as a workaround you can set PYTHON_BASIC_REPL=1 which should solve the issue