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+# Spec: Build provenance (git describe + build profile)
+
+**Status:** Proposed
+**Requirements:** new DR-093 (build provenance surfaced in-app and in logs); no UR — this is a diagnostic capability, not a user feature
+**UX spec:** n/a — adds an About block to Settings; no new flow
+**Supersedes / revises:** —
+
+## Summary
+
+Make every build say exactly what it is. Today a running JellyTau reports no
+version at all — not in the UI, not in the logs — and the only version string in
+the tree is the hand-maintained `0.2.0` duplicated across three files.
+
+This adds a `build.rs`-generated provenance string (`git describe` + short SHA +
+dirty flag + debug/release profile), exposes it over IPC, and renders it in a new
+Settings › About block. It also removes one of the three hand-bumped version
+files.
+
+## Motivation
+
+The concrete problem: when a user reports "the equalizer does nothing on my
+device" — which is a live risk for v0.2.0, whose Android audio settings are not
+yet device-verified — there is currently no way to tell which build they are
+running. Tag? Master? A local debug build from three weeks ago? The bug report
+cannot distinguish them.
+
+Two smaller irritations this also fixes:
+
+- **Debug builds masquerade as releases.** `0.2.0` is `0.2.0` whether it came
+  from a tagged release or `bun run tauri dev`.
+- **Three files carry the version.** `package.json`, `src-tauri/Cargo.toml` and
+  `src-tauri/tauri.conf.json` must be bumped in lockstep; the release checklist
+  exists partly to stop them drifting.
+
+### What this deliberately does *not* do
+
+**The canonical version stays hand-bumped in `Cargo.toml`.** Cargo requires a
+literal semver string at manifest-parse time and cannot derive it from git. The
+same is true of `tauri.conf.json`. Attempting to source the *release* version
+from a tag trades a scripted, reviewable bump for a fragile build-time
+dependency that breaks in exactly the environment we care most about (CI, in
+Docker, from a shallow clone).
+
+So: **the release version is authored; the build provenance is derived.** They
+answer different questions — "what release is this?" versus "what commit is this
+binary actually built from?" — and only the second benefits from git.
+
+## Layer assignment
+
+| Logic / responsibility | Layer | Why it belongs there |
+|------------------------|-------|----------------------|
+| Capturing git describe / SHA / dirty state at compile time | Rust (`build.rs`) | Only the Rust build has a compile step that can shell out to git and bake the result into the binary. A frontend equivalent would report the *dev server's* state, not the shipped binary's. |
+| Degrading to a sentinel when git is unavailable | Rust (`build.rs`) | Build-environment concern. Must never fail the build — CI runs in Docker from a shallow clone. |
+| Release version (`0.2.0`) | Rust (`Cargo.toml`, authored) | Domain fact about the product, not derivable from the environment. |
+| Deciding *what a build is* (release / dev / dirty) | Rust | Domain classification. The frontend must not infer "this is a dev build" from a string shape — it renders what it is told. |
+| Rendering the About block, copy-to-clipboard | Frontend | Pure presentation. |
+
+Borderline row: the release/dev/dirty classification could be done in the
+frontend by pattern-matching the describe string. It goes to Rust because that is
+a *rule about what constitutes a release build*, and it would have to change if
+the tagging scheme changed — the litmus test in the template puts that in Rust.
+Send a typed enum, not a string for the frontend to parse.
+
+## Design
+
+### `build.rs`
+
+```rust
+fn main() {
+    emit_build_provenance();
+    tauri_build::build()
+}
+
+fn emit_build_provenance() {
+    let describe = std::process::Command::new("git")
+        .args(["describe", "--tags", "--always", "--dirty"])
+        .output()
+        .ok()
+        .filter(|o| o.status.success())
+        .and_then(|o| String::from_utf8(o.stdout).ok())
+        .map(|s| s.trim().to_string())
+        .unwrap_or_else(|| "unknown".to_string());
+
+    println!("cargo:rustc-env=JELLYTAU_GIT_DESCRIBE={describe}");
+
+    // Rebuild when HEAD moves or a ref is written, so the string does not go
+    // stale across commits. Guarded: these paths do not exist in a git-less
+    // source tarball, and emitting rerun-if-changed for a missing path would
+    // force a rebuild every time.
+    for p in [".git/HEAD", ".git/refs"] {
+        if std::path::Path::new("../").join(p).exists() {
+            println!("cargo:rerun-if-changed=../{p}");
+        }
+    }
+}
+```
+
+🔴 **`build.rs` must never fail the build.** Every git call is
+`.ok()`-swallowed; a missing git binary, a shallow clone, or a source tarball all
+yield `"unknown"`. A build that breaks because git is absent would be a worse bug
+than the one this fixes.
+
+Note the `../` prefixes: `build.rs` runs with CWD at `src-tauri/`, so the repo's
+`.git` is one level up.
+
+### The provenance type
+
+```rust
+/// TRACES: DR-093
+#[derive(specta::Type, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct BuildInfo {
+    /// Authored release version (Cargo.toml).
+    pub version: String,
+    /// `git describe --tags --always --dirty`, or "unknown".
+    pub git_describe: String,
+    /// What kind of build this is — classified in Rust, not inferred by the UI.
+    pub kind: BuildKind,
+}
+
+/// TRACES: DR-093
+#[derive(specta::Type, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum BuildKind {
+    /// Built from a clean, exactly-tagged commit in release mode.
+    Release,
+    /// Release-mode build that is not on a clean tag (e.g. master, or dirty).
+    Untagged,
+    /// debug_assertions build.
+    Development,
+    /// Git state unavailable at build time.
+    Unknown,
+}
+```
+
+Classification:
+
+```rust
+let kind = if cfg!(debug_assertions) {
+    BuildKind::Development
+} else if describe == "unknown" {
+    BuildKind::Unknown
+} else if describe.contains('-') {   // "v0.2.0-3-gcb79a37" or "...-dirty"
+    BuildKind::Untagged
+} else {
+    BuildKind::Release
+};
+```
+
+### Command
+
+```rust
+/// TRACES: DR-093
+#[tauri::command]
+#[specta::specta]
+pub fn get_build_info() -> BuildInfo { … }
+```
+
+No parameters, so the camelCase param rule does not apply; the struct fields do
+need `#[serde(rename_all = "camelCase")]` (above). Regenerate `bindings.ts`.
+
+Also log the provenance once at startup, next to the existing init logging —
+that is what makes a user-submitted log file self-identifying, which is most of
+the value.
+
+### Settings › About
+
+A new block at the bottom of `src/routes/settings/+page.svelte`, rendering
+version, describe string, and a badge for non-release builds. One
+copy-to-clipboard button that yields a paste-ready block for bug reports:
+
+```
+JellyTau 0.2.0 (v0.2.0-3-gcb79a37-dirty, development)
+linux x86_64
+```
+
+Platform/arch come from the existing Tauri APIs; do not shell out.
+
+### Removing one version file
+
+`tauri.conf.json`'s `"version"` field can be omitted, in which case Tauri falls
+back to the Cargo version. That takes the bump from three files to two.
+
+**Verify before adopting**: confirm the Android `versionName`/`versionCode` and
+the NSIS installer version still resolve correctly with the field absent —
+Android packaging in particular reads the Tauri config. If either regresses,
+keep the field and drop this part; it is a convenience, not the point of the
+spec.
+
+## Out of scope
+
+- Deriving the *release* version from git tags (see Motivation).
+- A build-time timestamp. It defeats reproducible builds and adds little over
+  the commit SHA.
+- CI provenance/attestation, SBOM, signing.
+- Displaying the Jellyfin server version (separate concern, already available
+  from `/System/Info`).
+
+## Acceptance criteria
+
+- [ ] `cargo build` succeeds with git absent, from a shallow clone, and from a source tarball with no `.git` — yielding `"unknown"` in each case, never a build failure.
+- [ ] A tagged clean release build reports `BuildKind::Release`; `bun run tauri dev` reports `Development`; a dirty tree reports `Untagged` (release mode) with `-dirty` in the describe string.
+- [ ] The describe string changes after a new commit without a manual `cargo clean` (rerun-if-changed works).
+- [ ] Provenance is logged once at startup.
+- [ ] Settings › About renders version + describe + build-kind badge, with working copy-to-clipboard.
+- [ ] 🔴 CI checkouts that build a shippable artifact set `fetch-depth: 0`, or their artifacts are knowingly stamped `unknown`. Currently only `publish-docs.yml` sets it; `build-release.yml` has five checkouts and `build-and-test.yml` two, all of which would report `unknown` as-is.
+- [ ] **No toolchain installed in CI** — git is already present in the builder image; nothing new is added.
+- [ ] `bun run check`, `bun run test`, `bun run check:boundary` pass.
+- [ ] `cargo fmt` clean, `cargo clippy` clean, `bun run test:rust` passes.
+- [ ] `bindings.ts` regenerated.
+- [ ] DR-093 allocated in `requirements.md`; new code carries `// TRACES:`.
+
+## Testing
+
+**Rust**: the classification is pure and must be extracted from the command as
+`classify_build(describe: &str, debug: bool) -> BuildKind` so it can be tested
+directly. Cover: `"v0.2.0"` → `Release`; `"v0.2.0-3-gcb79a37"` → `Untagged`;
+`"v0.2.0-dirty"` → `Untagged`; `"unknown"` → `Unknown`; `debug = true` → always
+`Development` regardless of describe.
+
+`build.rs` itself is not unit-testable. Verify its failure path manually by
+building with `PATH` stripped of git, and from a `git archive` tarball — both
+must succeed with `"unknown"`.
+
+**Frontend**: assert the About block renders each `BuildKind` correctly, and that
+it renders the backend-supplied kind rather than re-deriving it from the string
+(a test that passes a `Release` kind with a `-dirty` describe and asserts the
+badge follows the *kind* would catch that regression).
+
+## TRACES
+
+- `build.rs` provenance emission → `// TRACES: | DR-093`
+- `BuildInfo` / `BuildKind` / `classify_build` → `// TRACES: | DR-093`
+- `get_build_info` command → `// TRACES: | DR-093`
+- Settings About block → `// TRACES: | DR-093`
+- `classify_build` tests → `UT-BUILD-1`
+- Allocate **DR-093** in `requirements.md` ("Build provenance: git describe and
+  build profile surfaced in-app and in logs"). Next free DR at time of writing
+  is DR-093.
+
+## Notes for the implementer
+
+- Do the `build.rs` + command + logging first; the About UI is the smaller half
+  and the logging alone delivers most of the diagnostic value.
+- The `fetch-depth: 0` change is the easiest part to forget and the one that
+  makes CI artifacts useless if missed — it is why that acceptance box is
+  flagged. Weigh it per workflow: test-only jobs do not need it.
+- Do not add a build timestamp "while you are in there" — see Out of scope.
+- A parallel Claude session may be active — `git diff` before "repairing"
+  unexpected changes.