Fix: fix simple SPA layout animations #3516
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Avoid stale shared layout nodes during SPA navigations and add an HTML regression fixture for disconnected resumeFrom cases.
Keep exiting nodes with snapshots while filtering stale layout stack members and update the SPA regression fixture accordingly.
mattgperry
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Feb 2, 2026
Clean up disconnected DOM instances from the layout stack lazily when new nodes are added. This prevents stale nodes from being used as resumeFrom targets during shared element transitions. The fix is minimal: 1. In add(): filter out members with disconnected instances and clear lead/prevLead if they were removed 2. In promote(): only use prevLead if its instance is still connected This addresses the same issue as #3516 but with ~15 lines instead of 190+. https://claude.ai/code/session_019kNt63LG4sBKvk5m87JVUb
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Avoid stale shared layout nodes during SPA navigations and add an HTML regression fixture for disconnected resumeFrom cases.
I encountered this problem on my SvelteKit app, but I suppose it affects other frameworks that approach navigation in a similar way as well. Svelte provides an onDestroy utility, but I wasn't able to get it to clean old nodes after the first navigation, only a full page refresh "fixed" it.
I suppose the additional checks shouldn't cause a perf regression since it happens only when adding or promoting, but I'm not very familiar with the codebase.
Please check carefully the logic and the test since I've narrowed down the issue thanks to Opus and GPT Codex, worked fine on my codebase, but haven't done anything extensive or stress tests.
Before the fix:
before_fix.mp4
After the fix:
after_fix.mp4