spork issue tracker

[cwillisf]

Several issues have popped up after the recent Scratch editor release, which includes the "spork" (Blockly unforking) work in scratch-blocks. This is a meta-issue to track them. We should file individual issues for each at some point, but that's probably after the most urgent items are hotfixed.

Big thanks to @redspacecat, @nimeratus, @mxmou, @Joeclinton1, @npxl32, and others for collecting reports and contributing technical analysis. See the comments on this issue for the running feed. There is also a community-maintained list at https://scratch.mit.edu/discuss/post/9109627/

Status (2026-04-30): two waves of fixes deployed (2026-04-21 and 2026-04-29). Backpack/broadcast de/serialization fixes (#554 + #555) merged today into the hotfix branch — not yet deployed to production. One community PR still open: #3571 (hat block delete preserves stack), CI clean, awaiting review. Custom block input deletion cursed inputs and the related "potato block" reports are the next fix priority.

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P0 -- Data loss / code deletion

• ✅ Disappearing blocks on project load. Fixed by #3547 + argumentdefaults follow-up.
  • https://scratch.mit.edu/discuss/topic/878239/
• ✅ Forever block wrapping deletes code. Fixed by fix: allow C-blocks without a next connection (e.g. forever) to wrap around mid-stack blocks scratch-blocks#3549. Deployed 2026-04-21.
  • https://scratch.mit.edu/discuss/topic/878427/
• ✅ Cursed/empty inputs (main case). Fixed by fix: recover shadow inputs dropped by Blockly's blockToDom scratch-blocks#3560 + #3563 + fix(scratch-vm): repair broken shadow references from cursed inputs bug #536. Deployed 2026-04-21. Confirmed working by forum users.
  • https://scratch.mit.edu/discuss/topic/878291/
• ✅ Wrong default value in sprite-targeting dropdowns. Fixed by #3548.
  • https://scratch.mit.edu/discuss/topic/878311/
• ✅ Duplicated blocks share shadow IDs. Fixed by fix: prevent stripIds from corrupting original block shadow state scratch-blocks#3570 + Fix/shadow top level scripts #543. Deployed 2026-04-29. Root cause: stripIds mutated original block's connection.shadowState by reference, creating orphaned top-level shadows that prevent workspace rendering on sprite switch. Diagnosis from @nimeratus, clear repro from @Joeclinton1.
• ✅ Code duplicates across sprites via angle picker (duplicating onto new sprites then unable to delete #537). Fixed by Fix: clear angle field event wrappers to prevent double-unbind scratch-blocks#3568 (@Joeclinton1). Deployed 2026-04-29. Root cause: angle field event wrappers not cleared after unbind, causing double-unbind crash.
  • duplicating onto new sprites then unable to delete #537
• Cursed inputs from custom block input deletion NOT fixed. Deleting a custom block input still creates a cursed/blank input. Confirmed still reproducible by @nimeratus and @redspacecat (2026-04-22). May share a code path with the "detached input fragments" reports below. Top fix priority.
  • Repro video from @redspacecat (2026-04-17)
• 🔀 Backpack de/serialization corruption. Fixes merged into hotfix branch 2026-04-30 (fix(scratch-vm): create missing variable and broadcast definitions on import #554 going-forward, fix(scratch-vm): repair missing variable and broadcast definitions on project load #555 load-time repair for already-corrupted projects). Awaiting deploy. Symptoms covered:
  • Variables corrupted to empty after dragging from backpack (@Joeclinton1, @redspacecat replication).
  • Variable names mangled (shared "my variable" IDs across projects).
  • Backpack broadcasts don't define the broadcast variable, so they can never fire (@nimeratus analysis). Independently re-confirmed by pippy2011eight (2026-04-29).
  • Forum: https://scratch.mit.edu/discuss/topic/879403/, https://scratch.mit.edu/discuss/topic/879479/, https://scratch.mit.edu/discuss/topic/880836/
• Detached string input fragments in custom blocks ("potato blocks"). Disconnected string input shapes appear floating in the workspace, can be typed into but not dragged. Reported by fortyonegames; ywc2 notes they "pop out of blocks they originally belonged to, particularly from custom blocks." Likely shares a code path with the custom block input deletion cursed input bug.
  • https://scratch.mit.edu/discuss/topic/880947/
• Blocks joining behind the block palette deletes code.
  • Reported by @redspacecat (2026-04-18)
  • Repro confirmed by @kaylen-s: dragging blocks into stacks behind the palette can delete unintended parts of the stack. (2026-04-30)
• 🤔 Sprite duplication causes code loss. All reports pre-date the 2026-04-21 hotfix; QA suggests this is likely fixed by one of the earlier hotfixes (probably the shared-shadow-ID fix in #3560/#3563). Needs re-verification on the current build.
  • https://scratch.mit.edu/discuss/topic/878551/
• 🔧 Deleting a hat block deletes the entire stack instead of just the hat. Community fix in fix: preserve stack below when deleting a top stack block scratch-blocks#3571 (@Joeclinton1) — open, CI clean as of 2026-04-30, ready for review. Undo works if you click the workspace first.
  • Reported by @Joeclinton1 (2026-04-22)
• Broadcast block causes costume to disappear on one sprite. Needs re-verification.
  • https://scratch.mit.edu/discuss/topic/878343/
• Dropdown bug causes code loss after save. Could not repro in test project.
  • https://scratch.mit.edu/discuss/topic/878374/

P1 -- Silent wrong behavior / runtime failures / interaction failures

• Broadcast blocks not firing at runtime. Multiple independent reports. Some likely manifestations of the backpack/sprite-import scoping bug fixed by fix(scratch-vm): create missing variable and broadcast definitions on import #554 + fix(scratch-vm): repair missing variable and broadcast definitions on project load #555 (merged, not yet deployed); non-backpack runtime cases need re-verification post-deploy. @nimeratus diagnosis.
  • https://scratch.mit.edu/discuss/topic/879319/, https://scratch.mit.edu/discuss/topic/879267/, https://scratch.mit.edu/discuss/topic/879200/
  • Also: https://scratch.mit.edu/discuss/topic/879827/, https://scratch.mit.edu/discuss/topic/879895/
• 🔀 Broadcasts dropdown empties after importing a sprite and switching away. Same scoping path as fix(scratch-vm): create missing variable and broadcast definitions on import #554. Awaiting deploy.
  • https://scratch.mit.edu/discuss/topic/878352/, https://scratch.mit.edu/discuss/topic/878407/
• 🔀 Backpacked sprites: broadcasts won't send, variables not selectable cross-sprite, can't drag code between sprites. Same cluster as fix(scratch-vm): create missing variable and broadcast definitions on import #554. Awaiting deploy.
  • https://scratch.mit.edu/discuss/topic/878434/
• 🔀 Events vanish after importing a backpacked sprite. Same cluster as fix(scratch-vm): create missing variable and broadcast definitions on import #554. Awaiting deploy.
  • https://scratch.mit.edu/discuss/topic/879069/
• 🔀 Empty variables bug: variable reporter shows empty when the variable ID in the block doesn't match the sprite/stage JSON definition. Same cluster as fix(scratch-vm): create missing variable and broadcast definitions on import #554/fix(scratch-vm): repair missing variable and broadcast definitions on project load #555 (load-time repair will heal already-corrupted projects). Awaiting deploy.
  • Reported by @nimeratus (2026-04-22)
• Ghost/invisible blocks: blocks become invisible but still execute. Reload fixes it. Triggered by tab switching, duplication, or sprite switching.
  • https://scratch.mit.edu/discuss/topic/879911/, https://scratch.mit.edu/discuss/topic/879960/
• Old projects: blocks disappear on load and block palette tab disappears + can't be reopened. Reported on ChromeOS Chrome 146. May be aftermath of cursed inputs in saved projects from before the 2026-04-21 hotfix.
  • https://scratch.mit.edu/discuss/topic/881000/ (reported 2026-04-30)
• Scripts fail to execute at runtime / green flag broken. Likely mostly aftermath of cursed inputs in saved projects; should diminish as users reload.
  • https://scratch.mit.edu/discuss/topic/879077/, https://scratch.mit.edu/discuss/topic/879121/, https://scratch.mit.edu/discuss/topic/879090/
  • https://scratch.mit.edu/discuss/topic/879311/
• Clone blocks not working.
  • https://scratch.mit.edu/discuss/topic/879114/, https://scratch.mit.edu/discuss/topic/878957/
• "Stop other scripts in sprite" block not working.
  • https://scratch.mit.edu/discuss/topic/879314/
• Phantom lists: lists can't be read by code, can't be fully deleted, leave ghost entries in the list tab.
  • https://scratch.mit.edu/discuss/topic/879458/
• Obsolete/hidden blocks broken: for-each, pen shade, counter, and the loud? boolean no longer work.
  • Reported by @npxl32 (2026-04-19)
• Cannot connect hat block above stack block.
  • https://scratch.mit.edu/discuss/topic/878315/
• Malformed block input freezes script execution. May be resolved by cursed inputs fix -- needs re-verification.
  • https://scratch.mit.edu/discuss/topic/878976/
• Red hat block (%15 in custom block definitions) no longer works.
  • https://scratch.mit.edu/discuss/topic/879259/
• Touch drag-and-drop broken: dragging costumes, blocks, and sounds between sprites does not work on tablets/phones.
  • https://scratch.mit.edu/discuss/topic/878722/, https://scratch.mit.edu/discuss/topic/879211/
• "When this sprite clicked" and broadcast dialog broken on touchscreen.
  • https://scratch.mit.edu/discuss/topic/878708/
• Sprite-specific variable monitors only allow one at a time.
  • https://scratch.mit.edu/discuss/topic/879391/
• Comments break the entire project (Safari-specific).
  • https://scratch.mit.edu/discuss/topic/879946/
• RTL editor interactions malfunction: reversed text and operators, erratic drag behavior, and custom blocks can disappear off-screen, making the editor unusable in affected languages.
  • Received a Freshdesk report from a Hebrew language program with ~100 students who are experiencing significantly disrupted classroom use

P2 -- Blocks editing broken

• "Create new broadcast/message" dialog closes immediately.
  • https://scratch.mit.edu/discuss/topic/878407/, https://scratch.mit.edu/discuss/topic/878251/, https://scratch.mit.edu/discuss/topic/879434/
  • Unable to repro on desktop (@kaylen-s and Marshally T.), but seems to be affecting touchscreen devices
• Keyboard shortcuts broken in block inputs: Ctrl+A in operator inputs, Ctrl+C/V in number-only inputs.
  • https://scratch.mit.edu/discuss/post/9116118/, https://scratch.mit.edu/discuss/topic/878840/
• Clipboard cleared on sprite switch.
  • https://scratch.mit.edu/discuss/topic/879096/
• Middle mouse button causes uncontrolled block/canvas movement.
  • https://scratch.mit.edu/discuss/topic/879165/
• Pasted blocks duplicate instead of following the mouse.
  • https://scratch.mit.edu/discuss/topic/878352/
• Duplicated blocks no longer auto-attach to cursor (behavioral regression from Blockly).
  • https://scratch.mit.edu/discuss/topic/879564/
• Custom blocks added from the backpack don't appear in the palette.
  • https://scratch.mit.edu/discuss/post/9109412/
• Variable palette doesn't refresh on variable creation (ChromeOS/Chrome 146).
  • https://scratch.mit.edu/discuss/topic/878354/
• Off-centered reporter blocks; spam-clicking reporters causes values to build up.
  • https://scratch.mit.edu/discuss/topic/878445/
• Grayed-out/uneditable operator blocks.
  • https://scratch.mit.edu/discuss/topic/879074/
• Code area becomes locked/unusable for certain sprites.
  • https://scratch.mit.edu/discuss/topic/879364/
• Custom block hat dragged over a linking block stack copies inputs to top-left of workspace.
  • Reported by @Joeclinton1 (2026-04-24)
• Dragging a block into the "Make a block" / "Make a Variable" / "Make a List" section triggers the dialog.
  • https://scratch.mit.edu/discuss/topic/879545/
• Backpacking blocks from block palette broken; no text for blocks in backpacked scripts.
  • https://scratch.mit.edu/discuss/3/ (reported ~2026-04-24)

P3 -- Visual / cosmetic regressions

• RTL language visual bugs: UI elements go offscreen, block outlines render LTR in RTL mode, set thumbnail popup not translated.
  • Reported by @redspacecat (citing gem1001) (2026-04-22)
  • Repro confirmed by @kaylen-s (2026-05-05)
• Broadcast ordering changed: "New Broadcast" no longer pinned to top of list.
  • https://scratch.mit.edu/discuss/topic/878547/
  • Repro confirmed by @kaylen-s (2026-05-05)
• Define block position jumps when dragging the embedded block.
  • https://scratch.mit.edu/discuss/topic/878508/
  • Repro confirmed by @kaylen-s (2026-05-05)
• Right-click variable menu overflows to top of screen with many variables.
  • Reported via https://scratch.mit.edu/discuss/post/9113967/
• Comment resize corner blocked by scrollbar.
  • Reported via https://scratch.mit.edu/discuss/post/9113967/
  • Repro confirmed by @kaylen-s (2026-05-05)
• C-block shadows/outlines don't render correctly when a cap block is at the bottom.
  • Reported by @npxl32 with video
• Visual phantom/glitching of blocks around block stack edges (Linux, Intel iGPU, X11, KDE Plasma).
  • Reported by @TechNerd64 with video
• Padding issues with dropdowns. Root cause: box-sizing: border-box missing in production. Fix identified by @mxmou.
  • https://scratch.mit.edu/discuss/topic/878269/
• Boolean blocks have an outline: https://scratch.mit.edu/discuss/topic/878300/
  • Repro confirmed by Will D. (2026-05-05)
• Menu popups have a black outline: https://scratch.mit.edu/discuss/topic/878294/
• Comments: scrollbar appears when text would fit without it; dragging a comment doesn't expand workspace: https://scratch.mit.edu/discuss/topic/878331/
• Block font changed for users without Helvetica Neue: https://scratch.mit.edu/discuss/topic/878363/
• Dragging block to left edge of palette lights up the stage
  • Repro confirmed by Lauren K. (2026-05-05)

P4 -- Performance / viewport

• Some projects cause severe slowness. Repro: https://scratch.mit.edu/projects/1306151552/editor/, switch to the "engine" sprite. Extreme case: 9.7 GB memory usage reported.
  • https://scratch.mit.edu/discuss/topic/878292/, https://scratch.mit.edu/discuss/topic/878155/
• Zoom snaps back when workspace scrolled past left edge.
  • https://scratch.mit.edu/discuss/topic/878349/

P5 -- Low-confidence / adjacent / unreproduced

• Keyboard pops up on number-only inputs (Android and Safari/mobile): https://scratch.mit.edu/discuss/topic/878361/, https://scratch.mit.edu/discuss/topic/878420/
• Blocks from one sprite appear in another sprite's workspace when switching while running (no repro): https://scratch.mit.edu/discuss/topic/878522/
• Script drag-to-sprite broken on iPad: https://scratch.mit.edu/discuss/topic/878983/
• Can't duplicate custom blocks (may have never been possible). Raised by @Joeclinton1.
• Variables disappearing (sparse report, may be addon-related): https://scratch.mit.edu/discuss/topic/879222/
• Pen color / touching color mismatch (unclear if unfork-related): https://scratch.mit.edu/discuss/topic/879292/
• Variable duplicating in sprite (evidence destroyed, unclear if reproducible): https://scratch.mit.edu/discuss/topic/879305/
• Crash when switching from costume editor to scripts tab: https://scratch.mit.edu/discuss/topic/879510/
• "Online" sensing block always reports online (unclear if unfork-related). Reported on forum 2026-04-29.
• Custom boolean inputs in definitions not rendering correctly (single report, fixed by reload, second user couldn't reproduce). https://scratch.mit.edu/discuss/topic/880914/
• Sprite costumes skipped when running a tight next costume + wait 0.1 loop over 100+ costumes. Likely runtime/timing rather than spork. https://scratch.mit.edu/discuss/topic/881012/
• "Property of sprite" block deletes itself when changing the sprite dropdown. Workaround: edit in the sidebar first.
  • Reported in https://scratch.mit.edu/discuss/post/9109627/
• Undo in costume editor replaces entire sprite with previous sprite. Hitting undo "too many times" in the costume editor reverts so far that the current sprite is replaced by the previously-edited sprite. Single report so far on ChromeOS / Chrome 132.
  • https://scratch.mit.edu/discuss/topic/880866/
• Reporter checkbox spacing in flyout: FlyoutCheckboxIcon misalignment.
  • Technical analysis from @mxmou
  • @kaylen-s - Unable to repro (2026-05-05)
• Block input text is unnaturally large at full zoom-out: https://scratch.mit.edu/discuss/topic/878294/
  • Lauren K. - Unable to repro (2026-05-05)
• Stop block dropdown uses wrong color in High Contrast Mode: https://scratch.mit.edu/discuss/topic/878363/
  • Lauren K. - Unable to repro (2026-05-05)
• Say/think blocks truncate long text: https://scratch.mit.edu/discuss/topic/878935/
  • Not inherently a bug and may be preferable to some users
• Samsung Internet: block text not centered, overlapping, sticking outside blocks: https://scratch.mit.edu/discuss/topic/878979/
  • Deprioritized since this is not a supported browser and the issue is not reproducible elsewhere
• Can't rename sprite (not reproduced): https://scratch.mit.edu/discuss/topic/878329/
  • @kaylen-s - Unable to repro (2026-05-05)

[redspacecat]

There's also another topic about some more editor oddities, not sure if they're all related to the other ones listed.
https://scratch.mit.edu/discuss/topic/878294/

My browser / operating system: Windows NT 10.0, Chrome 147.0.0.0, No Flash version detected

I have been experiencing a couple of issues with the block palette today:

When I click on or try to drag blocks, the page lags and my mouse doesn't usually display the correct animation.
Variables and menu popups now appear with a strange black outline.
Writing in a block's text input while zoomed all the way out makes the text look unnaturally large.

There may be others, but I don't know how to describe them. I assume this has something to do with the recent update. If they could be fixed as soon as possible, that would be great.

[redspacecat]

A bug with code comments: https://scratch.mit.edu/discuss/topic/878331/

My browser / operating system: Windows 10, Chrome 132, No Flash version detected

The image shows https://scratch.mit.edu/projects/941518411/ in TurboWarp and in the new Scratch editor (but after that I've also looked at it in the old editor https://scratchfoundation.github.io/scratch-gui/ and it looks in the same way as in TurboWarp)

If you click on the resizer on the comments, the scroll bars disappear.

Also it seems like the blocks moved to different positions in the new version

[redspacecat]

Someone also reported not being able to change the name of their sprite, but I can't replicate.
https://scratch.mit.edu/discuss/topic/878329/

[redspacecat]

When adding custom blocks from the backpack, they don't appear in the block palette.
https://scratch.mit.edu/discuss/post/9109412/

[redspacecat]

https://scratch.mit.edu/discuss/topic/878349/ - Screen zooming glitch

In the block editor, zooming in or out while scrolled past the left side of all of the scripts causes the camera to get snapped back again.

[redspacecat]

@cwillisf if you have time, could any of the other comments with issues I reported be added to the tracker?

[redspacecat]

Several issues from https://scratch.mit.edu/discuss/topic/878352/

• Previously when you copied and pasted something, it moved around with your mouse until you set it down. Now it just duplicates instead.
• When importing a sprite that uses broadcasts, after switching back to another sprite the broadcasts no longer appear in the dropdown.

[redspacecat]

https://scratch.mit.edu/discuss/post/9109491/

On some projects, inputs are messed up.

If you take some of the inputs out of operators in the Player Collision script, there will be cursed inputs underneath where you cannot input numbers.

This is happening on https://scratch.mit.edu/projects/1296008268/

[redspacecat]

https://scratch.mit.edu/discuss/topic/878251/ - New message menu closes immediately.
I can only replicate when using a touchscreen to tap the "new message" button.

[cwillisf]

At some level, I'm of course sad that it's happening... but the description of that issue as "cursed inputs" has brought a little bit of joy to an otherwise hectic afternoon :D

[redspacecat]

finally, the flood of issues has slowed 😅