# 404s downloading worker binary

- Provider: [Spacelift](https://down.guide/spacelift)
- Level: confirmed
- Impact: Partial outage
- lasted 52m
- started 2026-10-29 15:48 UTC
- eu
- id: DWN-00758bf7a4
- Official page: https://stspg.io/n06j8ndnlsmn

## Root cause
> \*\*Root Cause\*\*

[Postmortem](https://stspg.io/n06j8ndnlsmn)

## Updates from Spacelift
### 2026-10-29 15:48 UTC: investigating
We are investigating an issue where some runs fail to start with the error "couldn't start worker: error populating worker binary". Our team is actively working on this.

### 2026-10-29 16:24 UTC: monitoring
A fix has been applied and runs in the EU region are working again. We are monitoring the situation to make sure all runs start as expected

### 2026-10-29 16:40 UTC: resolved
This incident has been resolved. Runs in the EU region are starting normally again. If any of your runs failed during this period, please retrigger them

### 2026-10-30 09:10 UTC: postmortem
\*\*Summary\*\* 
Between 15:31 UTC and 15:55 UTC on October 29th, runs for customers using ARM runners failed to start with the following error message:
couldn't start worker: couldn't start docker container: error populating worker binary: unexpected response code when querying for worker binary at \[https://downloads.spacelift.io/worker-arm64/752bab1d/spacelift-worker\](https://downloads.spacelift.io/worker-arm64/752bab1d/spacelift-worker): 404
\*\*Incident Timeline\*\*
\* 15:31 UTC - A new deployment of the Spacelift backend was triggered.
\* 15:45 UTC - We triggered a rollback to the previous version.
\* 15:50 UTC - The fix began to take effect.
\* 15:55 UTC - The fix was fully rolled out.
\*\*Root Cause\*\* 
The problem was caused by our build pipeline failing silently to upload that single file. When we triggered a new deployment of the Spacelift backend, new runs switched over to the new worker version and began to fail because the file was missing.
\*\*Mitigations\*\*
\* Immediate: we rolled back to a previous working version.
\* Permanent: we have updated our deployment pipeline to ensure that it cannot silently fail to upload assets like this in future.

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