[v13.0.0-beta.2] Block move causes container to shift on canvas

[microbit-robert]

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Description

One can make 'move mode' followed by 'cancel' or 'confirm' shift its parent container across the workspace like a caterpillar. Please see the repro steps below and screen grab.

The type of renderer plays no part and can be reproduce with either.

Maybe related to #9708, but this is unknown.

Reproduction steps

1. Have a container block
2. Add at least three statement blocks
3. Press 'M' on the bottom 2 statement blocks - it doesn't result in any shift of the parent container on the workspace
4. Press 'M' on the statement block third from the bottom, or any above this - the parent container on the workspace shifts
5. Repeat for the caterpillar movement effect

Priority

No response

Stack trace

Screenshots

Screen.Recording.2026-05-05.at.15.34.58.mov

Browsers

No response

[cathelizabeth]

I just ran into this and saw there was already a bug created so I will comment here - When you inject blocks from the toolbox the same shift happens, and when you delete blocks by dragging them over the toolbox the shift happens as well for me on MacOS.

Video attached from v13.0.0-beta.3 branch showing moving block in via keyboard, workspace shifts, dragging block out via mouse, workspace shifts

Screen.Recording.2026-05-06.at.12.50.35.PM.mov