Status: plumbing PoC. It proves the wiring — Rust → codegen → build-from-source on each app build → load on both platforms — not a perf win yet. The one capability (sha1_hex) is single-shot in-memory, and the local-sync probe found hashing isn't the hot path; a measured payload is the next step. core_version is a smoke entrypoint. Mobile is the consumed path; the server napi crate builds and round-trips but is not wired into the server yet.

Layout

crates/
  immich_core        pure logic, no binding deps. capabilities = cargo features (hashing).
  immich_core_dart   cdylib/staticlib + cbindgen header for dart:ffi (mobile)
  immich_core_napi   cdylib (.node) via napi-rs (server, unwired)
immich_native_core/  the Flutter package mobile depends on. build hook + ffigen @Native bindings.
smoke/               host dart + node roundtrip scripts (no device)

Bindings are separate crates (Cargo can't gate crate-type by feature).

How the native lib is built (Flutter native assets — no prebuilt, no CI)

immich_native_core/hook/build.dart (native_toolchain_rust) compiles crates/immich_core_dart from source on every app build via rustup and bundles it as a Flutter code asset. The Dart side uses ffigen @Native externals bound to that asset — no DynamicLibrary, no prebuilt artifacts, no fetch/publish/separate-repo.

Native assets is on by default on Flutter stable (3.38+), so a stock flutter build runs the hook. Each builder needs rustup (the hook auto-installs the pinned toolchain + targets from crates/immich_core_dart/rust-toolchain.toml).

Dev commands (mise)

mise run build         cargo build --workspace
mise run test          cargo test --workspace     (host Rust tests, incl. FFI-boundary)
mise run lint          clippy -D warnings         (fmt: mise run fmt)
mise run codegen       regen cbindgen header + ffigen @Native bindings — commit the result
mise run test:flutter  HOST FFI roundtrip through the real build hook (no device)
mise run smoke         Rust tests + host dart:ffi + host napi roundtrips

Add a capability (end to end)

add the logic to crates/immich_core (behind a cargo feature if it pulls a dep).
expose a C entry in crates/immich_core_dart/src/lib.rs — #[no_mangle] pub extern "C", wrap the body in guard(...) (panic at the boundary → null, never unwind into the host), validate pointers, return Rust-owned memory the caller frees via immich_core_free_string.
mise run codegen — regenerates the committed cbindgen header + ffigen @Native bindings.
add an ergonomic wrapper + null-check in immich_native_core/lib/immich_native_core.dart.
(optional) mirror it in crates/immich_core_napi/src/lib.rs for the server.
mise run test:flutter (host) + add a case to immich_native_core/test/, and to mobile/integration_test/native_core_test.dart to exercise it on a device.

Consume from immich/mobile

immich_native_core: { path: ../native/immich_native_core } in mobile/pubspec.yaml, then dart pub get. No app-level Gradle/Podfile edits — the hook builds + bundles the lib. Builders need rustup. See the package README for the iOS App-Extension caveat.

/native/ is codeowned by @santoshakil + @mertalev. License: reuses the immich repo-root AGPL-3.0 (no separate license file).