# Retool: Major incident: React App Builder Sandbox Installs May Fail to Install Dependencies

**Summary:** Retool reported a major React App Builder incident: downstream dependency issues could prevent sandbox installation and connection on Cloud and Self-Hosted instances. It ran from 2026-08-20 17:26 UTC to 2026-08-20 23:20 UTC (5 h 54 min); Cloud recovered at 17:30 UTC, and self-hosted fixes shipped in 4.0.12-stable and 4.43.0-edge. _(machine-written, sol)_
- Kind: Major incident · Label: outage (model (Jev))
- Changed: 2026-08-20 17:26 UTC · Detected: 2026-10-17 18:22 UTC
- [Source: https://stspg.io/hfvc3zn0ct60](https://stspg.io/hfvc3zn0ct60)
- [Company: Retool](https://rewindex.com/company/retool.md)
- Versions: before (none: first archived) → after incident\_version:204/v65248gt8jlm@f3ca64269c37
- Change 1 of 1 for this incident

## What changed

**1. Added: Title**

```diff
+ React App Builder Sandbox Installs May Fail to Install Dependencies
```

**2. Added: Impact**

```diff
+ major
```

**3. Added: Status**

```diff
+ resolved
```

**4. Added: Start time**

```diff
+ 2026-08-20 17:26 UTC
```

**5. Added: Resolved time**

```diff
+ 2026-08-20 23:20 UTC
```

**6. Added: Affected components**

```diff
+ New app builder, Self Hosted On-Premise
```

**7. Added: Update** (investigating) · 2026-08-20 17:26 UTC

```diff
+ Retool's app builder may fail to install and connect to a sandbox due to downstream dependency issues. This affects both Cloud and Self-Hosted Retool instances.
```

**8. Added: Update** (identified) · 2026-08-20 17:30 UTC

```diff
+ This issue no longer affects the React App Builder on Retool Cloud. We have identified the issue for self-hosted, and are working on releasing images with a fix
```

**9. Added: Update** (identified) · 2026-08-20 18:16 UTC

```diff
+ This issue affects Retool version 4.0.0+ (stable and edge), specifically for 1) newly-created React apps, 2) new publishes of existing React apps, and 3) cold starts of sandboxes when editing existing React apps. Existing published apps that do not get published after August 19th are unaffected. Self-hosted customers can update to 4.43.0-edge to get an immediate fix. A patch to our stable release channel is coming soon.
```

**10. Added: Update** (monitoring) · 2026-08-20 21:08 UTC

```diff
+ Images with the fix are out: 4.0.12-stable 4.43.0-edge Our minimum release age for React app builder dependencies is 5 days, so this incident will self-resolve for any self-hosted deployments that don't upgrade on August 24th, by 7am PST. All currently affected self-hosted versions: stable: 4.0.0 - 4.0.11 edge: 4.1, 4.9, 4.16, 4.19, 4.23, 4.27, 4.31, 4.35, 4.40
```

**11. Added: Update** (resolved) · 2026-08-20 23:20 UTC

```diff
+ This incident is resolved. Images with the fix are out: 4.0.12-stable 4.43.0-edge Our minimum release age for React app builder dependencies is 5 days, so this incident will self-resolve for any self-hosted deployments that don't upgrade on August 24th, by 7am PST. All currently affected self-hosted versions: stable: 4.0.0 - 4.0.11 edge: 4.1, 4.9, 4.16, 4.19, 4.23, 4.27, 4.31, 4.35, 4.40
```

## History of this incident

| When (UTC) | Change | Label |
| --- | --- | --- |
| 2026-08-20 17:26 UTC | Major incident: React App Builder Sandbox Installs May Fail to Install Dependencies (this change) | outage |

All Retool changes: [timeline](https://rewindex.com/company/retool/changes.md)
_Diff excerpts are shown on normalized text: dates, counters and tokens appear as ‹date›, ‹count›, ‹tok›; noise-only edits are hidden. Rewindex shows the changed passages, not a copy of the page._


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Canonical: https://rewindex.com/change/id9ca15467e45cc · Markdown: https://rewindex.com/change/id9ca15467e45cc.md · JSON: https://rewindex.com/api/v1/changes/id9ca15467e45cc · Generated 2026-10-18T02:54:37.648Z