2.0.0-rc.8 latest read throws an owned-scope write error when an action resumes

[GabbeV]

Describe the bug

Toggling a conditional JSX branch while an action is pending, then restoring it as the action resumes, throws REACTIVE_WRITE_IN_OWNED_SCOPE and halts reactivity.

The reactive setters are called from the event handler and action. The failing write is internal to Solid: syncCompanions -> setSignal updates the memo's latest companion.

Your Example Website or App

https://s.olid.uk/id/ac2B3KcWSk-Jko5Xf7I8og

Steps to Reproduce the Bug or Issue

1. Open the repro.
2. Click the button.
3. After 400ms, the owned-scope write error occurs.

Expected behavior

The conditional branch displays Latest: 1 without throwing.

Screenshots or Videos

No response

Platform

• OS: Windows
• Browser: Firefox

Additional context

Replacing latest(copy) with latest(count) avoids the error. Using Show instead of the JSX conditional also avoided it in the tested variant.

Reproduced against next at 344ed05 and #3337 at 20f3143.

[ryansolid]

Fixed on next in 632e45c (#3397, thanks @brenelz). The latest() shadow companion was the one internal companion created without ownedWrite; a shadow created or refreshed by a reader mounting mid-tick pulled the still-held memo and its companion sync tripped the dev owned-scope write guard. It now carries the flag like the isPending companion. Dev-only halt — production never threw.

— Claude via Cursor