Crash on startup: Unhandled exception FormatException: Unknown release type 'snapshot'

[pawseytj]

Is there an existing issue for this?

• I have searched the existing issues and found none matching what I'm reporting.

Bug Description

When launching the App Center, the application fails to load the Manage tab (spinning loading icon) or crashes via terminal with a Dart isolate exception. The crash is caused by the AppStream parser hitting an unknown release type 'snapshot' in the local metadata cache.

Steps to reproduce the behavior

1. Run snap-store in the terminal.
2. Observe the crash output.
   (Note: Clearing the /var/cache/swcatalog/ and app-info directories allows the store to open until apt update pulls the metadata again).

Expected behavior

The App Center should gracefully ignore unrecognized release types in the AppStream metadata rather than crashing the isolate.

Ubuntu release

Ubuntu 26.04 LTS

System info

7.0.0-28-generic #28-Ubuntu SMP PREEMPT_DYNAMIC Sun Jun 21 01:01:36 UTC 2026 x86_64
name: snap-store
summary: Discover, install and manage Linux apps
publisher: Canonical✓
store-url: https://snapcraft.io/snap-store
license: unset
description: |
The App Center showcases featured and popular applications with useful
descriptions, ratings, and screenshots.

Apps can be found either through browsing categories or by searching.

The App Center can also be used to update apps, switch channels, and view
and submit ratings.

In older Ubuntu releases, the App Center is called Snap Store and is based
on GNOME Software.
commands:

• snap-store.show-updates
• snap-store
  services:
  snap-store.packagekit-session-installer: dbus, enabled, inactive
  snap-id: gjf3IPXoRiipCu9K0kVu52f0H56fIksg
  tracking: 2/candidate
  refresh-date: 2026-04-30
  channels:
  2/stable: 0+git.10310e85 2026-04-22 (1367) 16.4MB -
  2/candidate: ↑
  2/beta: ↑
  2/edge: 0+git.c1a8a57b 2026-06-25 (1382) 12.4MB -
  latest/stable: 41.3-72-g80e7130 2024-09-22 (1216) 12.8MB -
  latest/candidate: ↑
  latest/beta: ↑
  latest/edge: 0+git.c1a8a57b 2026-06-25 (1382) 12.4MB -
  preview/stable: –
  preview/candidate: 0.2.7-alpha 2023-02-02 (864) 10.9MB -
  preview/beta: ↑
  preview/edge: 0.3.0-alpha 2023-08-14 (1017) 11.2MB -
  1/stable: 41.3-72-g80e7130 2024-09-22 (1216) 12.8MB -
  1/candidate: ↑
  1/beta: ↑
  1/edge: 41.3-72-g80e7130 2024-09-16 (1216) 12.8MB -
  installed: 0+git.10310e85 (1367) 16.4MB -

---

name: snapd
summary: Daemon and tooling that enable snap packages
publisher: Canonical✓
store-url: https://snapcraft.io/snapd
contact: https://bugs.launchpad.net/snapd
license: GPL-3.0
description: |
Install, configure, refresh and remove snap packages. Snaps are
'universal' packages that work across many different Linux systems,
enabling secure distribution of the latest apps and utilities for
cloud, servers, desktops and the internet of things.

Start with 'snap list' to see installed snaps.
type: snapd
snap-id: PMrrV4ml8uWuEUDBT8dSGnKUYbevVhc4
tracking: latest/stable
refresh-date: 3 days ago, at 16:03 AEST
channels:
latest/stable: 2.76 2026-07-03 (27406) 52.5MB -
latest/candidate: 2.76 2026-06-22 (27406) 52.5MB -
latest/beta: 2.76 2026-05-31 (27406) 52.5MB -
latest/edge: 2.76+g235.606b9b0 2026-07-17 (27825) 46.9MB -
fips-updates/stable: –
fips-updates/candidate: –
fips-updates/beta: –
fips-updates/edge: 2.76+g235.606b9b0+fips 2026-07-17 (27831) 50.4MB -
installed: 2.76 (27406) 52.5MB snapd

Additional context

[ERROR:flutter/runtime/dart_isolate.cc(1402)] Unhandled exception:
FormatException: Unknown release type 'snapshot'
#0 _parseReleaseType (package:appstream/src/collection.dart:944)
#1 new AppstreamCollection.fromYaml (package:appstream/src/collection.dart:641)
#2 AppstreamPool._loadYamlCollectionInIsolate (package:appstream/src/pool.dart:94)

[pasch256]

same problem here....
[ERROR:flutter/runtime/dart_isolate.cc(1402)] Unhandled exception:
FormatException: Unknown release type 'snapshot'
#0 _parseReleaseType (package:appstream/src/collection.dart:944)
#1 new AppstreamCollection.fromYaml (package:appstream/src/collection.dart:641)
#2 AppstreamPool._loadYamlCollectionInIsolate (package:appstream/src/pool.dart:94)

[vicajilau]

The metadata that triggers this is still in the archive: resolute-updates/main carries a type: snapshot release for nautilus 50.2.2, which the appstream package doesn't know about. Its AppstreamReleaseType only has stable and development, while libappstream defines AS_RELEASE_KIND_SNAPSHOT.

Worth noting that the crash and the spinning Manage tab are the same event, not alternatives. Collection parsing runs in an isolate spawned without an error port, so the FormatException kills the isolate — the runtime prints it to stderr, which reads as a crash, but the parent just waits on a ReceivePort that will never emit. AppstreamPool.load() never completes, so componentsByPackage → localDebs → installedApps/appUpdates all stay in loading, and Manage spins forever with nothing in the app log.

Confirmed on 26.04 by tracing PackageKit. Broken run:

11:34:51 PackageKit: daemon start
11:34:52 get-packages transaction finished with success after 616ms
(nothing further — daemon idles out 5 minutes later)

The chain stalls at the AppStream step and never issues another call. With the fix applied:

12:47:31 get-packages finished with success after 802ms
12:47:36 get-updates  finished with success after 786ms
12:47:37 get-details  finished with success after 435ms

Manage then renders normally, including the deb updates that were previously invisible because localDebs never completed.

Fix proposed upstream: canonical/appstream.dart#44, it adds the missing release type, and wires onError into the isolate so that a parse failure surfaces as an exception instead of hanging silently. That second part matters beyond this bug: right now any catalog the parser chokes on freezes every consumer of the pool, with no error and no log line.

This issue can't close until that lands, gets published to pub.dev, and app-center bumps its appstream constraint.

[jahidhasanrimon333-cmyk]

I am experiencing the same issue on Ubuntu 26.04 LTS.

The App Center opens normally, but the Manage tab remains stuck on the loading spinner and never loads the installed apps or updates.

Running snap-store from the terminal produces:

FormatException: Unknown release type 'snapshot'
#0 _parseReleaseType (package:appstream/src/collection.dart:944)
#1 new AppstreamCollection.fromYaml (package:appstream/src/collection.dart:641)
#2 AppstreamPool._loadYamlCollectionInIsolate (package:appstream/src/pool.dart:94)

My App Center is currently:
snap-store 0+git.10310e85 (revision 1367)
channel: 2/stable

I also reinstalled AppStream successfully:
AppStream version: 1.1.2

I confirmed that the error still occurs after switching from the edge channel to 2/stable.

The Manage page is still stuck loading.

This appears to match the issue described here. Please let me know if you need any additional diagnostics or logs.