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When an effect creates another effect and a proxy property is read that wasn't before, the proxy will have logic where it creates the new signal in its original reaction context. But it did not have logic to correctly handle the reaction_sources array which prevents effects/deriveds rerunning when state created inside themselves is read and then changed inside them: Since reaction_sources wasn't take the reaction context into account, false positives could occur where nested effects would not register the sources as dependencies.

Fixes #15870

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When an effect creates another effect and a proxy property is read that wasn't before, the proxy will have logic where it creates the new signal in its original reaction context. But it did not have logic to correctly handle the `reaction_sources` array which prevents effects/deriveds rerunning when state created inside themselves is read and then changed inside them: Since `reaction_sources` wasn't take the reaction context into account, false positives could occur where nested effects would not register the sources as dependencies.

Fixes #15870
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changeset-bot bot commented Jun 17, 2025

🦋 Changeset detected

Latest commit: efb9b63

The changes in this PR will be included in the next version bump.

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pnpm add https://pkg.pr.new/svelte@16193

@Rich-Harris Rich-Harris merged commit 061ab31 into main Jun 17, 2025
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@Rich-Harris Rich-Harris deleted the reaction_sources-fix branch June 17, 2025 21:07
@github-actions github-actions bot mentioned this pull request Jun 17, 2025
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Successfully merging this pull request may close these issues.

Components added to dom using 'mount' have broken reactivity in {#if} when reacting to state from context
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