matrix-org / matrix-org/matrix-rust-sdk
Crashes on Element X Android: 'cannot fail because at least one empty chunk must exist'
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Description
There are several crashes on Android with this error message when instantiating a timeline:
> items cannot fail because at least one empty chunk must exist
The code is here:
https://github.com/matrix-org/matrix-rust-sdk/blob/01bd672d05751c2ad88e4629ebeac124bb2be47b/crates/matrix-sdk-common/src/linked_chunk/mod.rs#L1030-L1035
The associated rageshakes I found are:
- https://github.com/element-hq/element-x-android-rageshakes/issues/9671
- https://github.com/element-hq/element-x-android-rageshakes/issues/9481
- https://github.com/element-hq/element-x-android-rageshakes/issues/9244
All of them happened after December of 2025, so it seems like a recent-ish change caused it.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in crates/matrix-sdk-common/src/linked_chunk/mod.rs around lines 1030-1035, then compare recent changes to the timeline and linked-chunk logic against the three associated rageshakes. Trace the state that causes timeline instantiation to reach the reported failure, reproduce it with an existing test or fixture if available, and verify that the crash is prevented with coverage for the failing state.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100