The Rust toolchain was unpinned on both sides, and the two sides had drifted
five releases apart: the CI builder image ships rustc 1.97.1, the development
machine was on 1.92.0. Clippy's lint set and rustfmt's output both change
between releases, so a green `cargo clippy` / `cargo fmt --check` locally said
nothing about CI and vice versa — which is the reason the clippy gate could
not be trusted enough to turn on.
src-tauri/rust-toolchain.toml pins channel 1.97.1 with the rustfmt and clippy
components. Deliberately no `targets` list: that would make rustup fetch the
Android and Windows std libraries on every plain `cargo test`, including on
machines that never cross-compile. The image already has them.
Dockerfile.builder installs that exact version instead of "latest stable at
rebuild time", and prints rustc/clippy versions so a mismatch is visible in
the build log.
The pin only becomes authoritative once the image is rebuilt and pushed
(scripts/build-builder-image.sh). Until then CI still runs whatever rustc the
current image has, and if that is not 1.97.1 rustup will download the pinned
toolchain at job time — a toolchain install in CI, which CLAUDE.md forbids.
Both files carry that warning next to the version.
Note: the clippy step in .gitea/workflows/build-and-test.yml is left advisory
here; tightening it wants a warning count measured on 1.97.1 first.
