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fix: reinstate reactivity loss tracking#17801

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Rich-Harris merged 7 commits intomainfrom
reinstate-reactivity-loss-detection
Mar 17, 2026
Merged

fix: reinstate reactivity loss tracking#17801
Rich-Harris merged 7 commits intomainfrom
reinstate-reactivity-loss-detection

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We commented out this code in #17038 because it was broken. I suspect it was broken because we weren't correctly calling unset_context inside run, leading to false positives — this is now fixed, and as such I think we can safely reinstate it.

One small change — I got rid of the was_read check. I assume this existed to prevent duplicate warnings, but it actually causes false negatives in the case where you read a signal while the reaction is being tracked then again while it's untracked.

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changeset-bot Bot commented Feb 25, 2026

🦋 Changeset detected

Latest commit: 26c8b7c

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

This PR includes changesets to release 1 package
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svelte Patch

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pnpm add https://pkg.pr.new/svelte@17801

@elliott-with-the-longest-name-on-github elliott-with-the-longest-name-on-github added needs-ecosystem-ci This PR needs to have an ecosystem CI run started prior to its last commit before merging. and removed needs-ecosystem-ci This PR needs to have an ecosystem CI run started prior to its last commit before merging. labels Feb 26, 2026
@Rich-Harris Rich-Harris merged commit 5faf102 into main Mar 17, 2026
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@Rich-Harris Rich-Harris deleted the reinstate-reactivity-loss-detection branch March 17, 2026 20:06
@github-actions github-actions Bot mentioned this pull request Mar 17, 2026
dummdidumm added a commit to sveltejs/language-tools that referenced this pull request Mar 17, 2026
sveltejs/svelte#17801 introduced dynamic compile options; had to adjust one occurence as a result
Rich-Harris pushed a commit that referenced this pull request Mar 17, 2026
This PR was opened by the [Changesets
release](https://github.com/changesets/action) GitHub action. When
you're ready to do a release, you can merge this and the packages will
be published to npm automatically. If you're not ready to do a release
yet, that's fine, whenever you add more changesets to main, this PR will
be updated.


# Releases
## svelte@5.54.0

### Minor Changes

- feat: allow `css`, `runes`, `customElement` compiler options to be
functions ([#17951](#17951))

### Patch Changes

- fix: reinstate reactivity loss tracking
([#17801](#17801))

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
dlrobson added a commit to dlrobson/dlrobson.github.io that referenced this pull request Mar 22, 2026
This PR contains the following updates:

| Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) |
|---|---|---|---|
| [svelte](https://svelte.dev) ([source](https://github.com/sveltejs/svelte/tree/HEAD/packages/svelte)) | [`5.53.7` → `5.54.1`](https://renovatebot.com/diffs/npm/svelte/5.53.7/5.54.1) | ![age](https://developer.mend.io/api/mc/badges/age/npm/svelte/5.54.1?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/svelte/5.53.7/5.54.1?slim=true) |
| [svelte](https://svelte.dev) ([source](https://github.com/sveltejs/svelte/tree/HEAD/packages/svelte)) | [`5.53.6` → `5.54.1`](https://renovatebot.com/diffs/npm/svelte/5.53.6/5.54.1) | ![age](https://developer.mend.io/api/mc/badges/age/npm/svelte/5.54.1?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/svelte/5.53.6/5.54.1?slim=true) |

---

### Release Notes

<details>
<summary>sveltejs/svelte (svelte)</summary>

### [`v5.54.1`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#5541)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.54.0...svelte@5.54.1)

##### Patch Changes

- fix: hydration comments during hmr ([#&#8203;17975](sveltejs/svelte#17975))

- fix: null out `effect.b` in `destroy_effect` ([#&#8203;17980](sveltejs/svelte#17980))

- fix: group sync statements ([#&#8203;17977](sveltejs/svelte#17977))

- fix: defer batch resolution until earlier intersecting batches have committed ([#&#8203;17162](sveltejs/svelte#17162))

- fix: properly invoke `iterator.return()` during reactivity loss check ([#&#8203;17966](sveltejs/svelte#17966))

- fix: remove trailing semicolon from {[@&#8203;const](https://github.com/const)} tag printer ([#&#8203;17962](sveltejs/svelte#17962))

### [`v5.54.0`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#5540)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.53.13...svelte@5.54.0)

##### Minor Changes

- feat: allow `css`, `runes`, `customElement` compiler options to be functions ([#&#8203;17951](sveltejs/svelte#17951))

##### Patch Changes

- fix: reinstate reactivity loss tracking ([#&#8203;17801](sveltejs/svelte#17801))

### [`v5.53.13`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#55313)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.53.12...svelte@5.53.13)

##### Patch Changes

- fix: ensure `$inspect` after top level await doesn't break builds ([#&#8203;17943](sveltejs/svelte#17943))

- fix: resume inert effects when they come from offscreen ([#&#8203;17942](sveltejs/svelte#17942))

- fix: don't eagerly access not-yet-initialized functions in template ([#&#8203;17938](sveltejs/svelte#17938))

- fix: discard batches made obsolete by commit ([#&#8203;17934](sveltejs/svelte#17934))

- fix: ensure "is standalone child" is correctly reset ([#&#8203;17944](sveltejs/svelte#17944))

- fix: remove nodes in boundary when work is pending and HMR is active ([#&#8203;17932](sveltejs/svelte#17932))

### [`v5.53.12`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#55312)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.53.11...svelte@5.53.12)

##### Patch Changes

- fix: update `select.__value` on `change` ([#&#8203;17745](sveltejs/svelte#17745))

- chore: add `invariant` helper for debugging ([#&#8203;17929](sveltejs/svelte#17929))

- fix: ensure deriveds values are correct across batches ([#&#8203;17917](sveltejs/svelte#17917))

- fix: handle async RHS in `assignment_value_stale` ([#&#8203;17925](sveltejs/svelte#17925))

- fix: avoid traversing clean roots ([#&#8203;17928](sveltejs/svelte#17928))

### [`v5.53.11`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#55311)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.53.10...svelte@5.53.11)

##### Patch Changes

- fix: remove `untrack` circular dependency ([#&#8203;17910](sveltejs/svelte#17910))

- fix: recover from errors that leave a corrupted effect tree ([#&#8203;17888](sveltejs/svelte#17888))

- fix: properly lazily evaluate RHS when checking for `assignment_value_stale` ([#&#8203;17906](sveltejs/svelte#17906))

- fix: resolve boundary in correct batch when hydrating ([#&#8203;17914](sveltejs/svelte#17914))

- chore: rebase batches after process, not during ([#&#8203;17900](sveltejs/svelte#17900))

### [`v5.53.10`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#55310)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.53.9...svelte@5.53.10)

##### Patch Changes

- fix: re-process batch if new root effects were scheduled ([#&#8203;17895](sveltejs/svelte#17895))

### [`v5.53.9`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#5539)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.53.8...svelte@5.53.9)

##### Patch Changes

- fix: better `bind:this` cleanup timing ([#&#8203;17885](sveltejs/svelte#17885))

### [`v5.53.8`](https://github.com/sveltejs/svelte/blob/HEAD/packages/svelte/CHANGELOG.md#5538)

[Compare Source](https://github.com/sveltejs/svelte/compare/svelte@5.53.7...svelte@5.53.8)

##### Patch Changes

- fix: `{@&#8203;html}` no longer duplicates content inside `contenteditable` elements ([#&#8203;17853](sveltejs/svelte#17853))

- fix: don't access inert block effects ([#&#8203;17882](sveltejs/svelte#17882))

- fix: handle asnyc updates within pending boundary ([#&#8203;17873](sveltejs/svelte#17873))

- perf: avoid re-traversing the effect tree after `$:` assignments ([#&#8203;17848](sveltejs/svelte#17848))

- chore: simplify scheduling logic ([#&#8203;17805](sveltejs/svelte#17805))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about these updates again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My44NC4yIiwidXBkYXRlZEluVmVyIjoiNDMuODQuMiIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Reviewed-on: https://forgejo.tail5a98.ts.net/gooilers123/monolith/pulls/47
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