August 24, 2026
Fission 0.13.0: stable widget identity and Apache 2.0
Fission 0.13.0 removes a persistent source of subtle application bugs: ordinary
widgets now receive deterministic identity without requiring developers to
manually assign IDs throughout the tree. This release also changes Fission's
sole project license from MIT to Apache License 2.0.
This is a minor release because automatic identity changes retained runtime
behavior and the license change affects every redistributed Fission package.
Stable identity is the default
Every authored widget is assigned an identity derived from one application root,
its structural child path, its child slot, and its widget kind. Identical trees
therefore produce identical identities and clean frame diffs. Internal wrappers,
decorations, portals, and shell overlays no longer make authored identities drift.
Applications normally do not need to configure the root. Desktop, Web, mobile,
Winit, and Terminal applications use WidgetId::app_root() by default and can
set an explicit namespace when hosting multiple independent roots:
DesktopApp::<AppState, _>::new(App)
.with_root_id(WidgetId::explicit("primary-window"))
.run()
An explicit ID set directly on a widget remains authoritative.
Collections remain predictable
Unidentified collection items retain identity by position. That is the useful
default for fixed-order content and matches how a developer reads an ordinary
widget tree.
When state must follow data through insertion, filtering, or reordering, assign
an ID only to the logical item:
let children = projects
.into_iter()
.map(|project| {
ProjectCard { project: project.clone() }
.id(WidgetId::explicit(&format!("project.{}", project.id)))
})
.collect();
All automatically identified descendants are scoped beneath that explicit ID.
Collections can freely mix explicit and automatic items: explicit state follows
its data while unidentified state remains positional.
The same authority now backs #[local_state]. Local values remain stable across
rebuilds, are isolated between application roots, and are pruned when their
widget disappears.
Apache License 2.0 is the sole Fission license
Fission and all first-party crates are now licensed exclusively under the
Apache License 2.0.
This replaces the previous MIT license and is not a dual-license arrangement.
Every first-party Cargo manifest, crate README, repository license reference,
documentation surface, generated template, and bundled Fission design package
now declares Apache-2.0. Vendored dependencies and bundled fonts continue to
carry their own upstream license notices.
Upgrade
Update the framework and CLI:
[dependencies]
fission = { version = "0.13.0", default-features = false, features = ["desktop"] }
cargo install cargo-fission --version 0.13.0 --locked
Most applications need no source migration. Keep explicit IDs for reorderable
logical collection items and widgets addressed directly by application code;
IDs added solely because an ordinary static widget was previously unstable can
usually be removed.
Redistributors must follow the Apache License 2.0 redistribution conditions.
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