Fix .beam save quirks: real sample rate, drop dead fields

Address the code smells flagged in the .beam format spec:

- Write the project's actual sample rate on save instead of a hardcoded 48000
  (add AudioProject::sample_rate()).
- Remove the vestigial RasterKeyframe.media_path field (it was only used by the
  legacy ZIP loader, which now derives "media/raster/<id>.png" from the keyframe
  id) and the dead buffer_path_at_time accessor. Backward-compatible: older files
  carrying media_path deserialize fine (the field is ignored).
- Drop the unused SaveSettings fields auto_embed_threshold_bytes / force_embed_all
  / force_link_all; only large_media_mode was ever consulted. Un-prefix the now-used
  `settings` parameter.

Update BEAM_FILE_FORMAT.md to match. The remaining notes (reserved MediaKind::Video,
exact-match version check) are design choices, left as-is.

BEAM_FILE_FORMAT.md

@@ -255,15 +255,15 @@ Collections that carry media linkage are **bold**:
 
 `RasterKeyframe` (within the layer tree) has `id: Uuid` (= its full-res `Raster`
 media id and the seed for its `RasterProxy` id), `time`, `width`, `height`,
-`tween_after`, `stroke_log`, and a `media_path` string that is **vestigial** in
+`tween_after`, and `stroke_log`. Pixel buffers are `#[serde(skip)]` and faulted in
-SQLite files (it names the legacy ZIP entry path; the SQLite path keys on `id` and
+from media rows. (The legacy ZIP entry path `media/raster/<id>.png` is derived from
-ignores it). Pixel buffers are `#[serde(skip)]` and faulted in from media rows.
+`id`; older files may also carry a now-ignored `media_path` field.)
 
 ### 8.3 `SerializedAudioBackend`
 
 | Field                | Type                | Notes |
 |----------------------|---------------------|-------|
-| `sample_rate`        | `u32`               | **Unreliable:** the current writer hardcodes `48000` here; authoritative rates are on `AudioProject.sample_rate` and each `AudioPoolEntry.sample_rate`. |
+| `sample_rate`        | `u32`               | The project's system sample rate (mirrors `AudioProject.sample_rate`). Per-file rates are on each `AudioPoolEntry.sample_rate`. |
 | `project`            | `AudioProject`      | Tracks + MIDI clip pool (§8.4). |
 | `audio_pool_entries` | `[AudioPoolEntry]`  | Audio source registry (§8.5). |
 | `layer_to_track_map` | `map<Uuid, u32>`    | UI layer UUID → engine track id. `#[serde(default)]`. |
@@ -388,8 +388,8 @@ internal layout:
   extension. **FLAC entries are decoded to PCM `f32` and re-encoded in memory as
   IEEE-float WAV (WAV format tag 3)** before being base64-embedded; other formats are
   embedded as-is. The entry's `relative_path` is cleared after extraction.
-- `media/raster/<uuid>.png` — raster keyframe pixels, named by
+- `media/raster/<uuid>.png` — raster keyframe pixels, named `media/raster/<id>.png`
-  `RasterKeyframe.media_path`.
+  after the keyframe's `id`.
 
 A reader MUST NOT modify a legacy ZIP on open; it loads into memory only. **The next
 save migrates the project to SQLite** (the save sees a non-SQLite target, so it takes
@@ -451,18 +451,15 @@ A conforming **writer** MUST:
 These reflect the current reference implementation and are flagged for implementers
 and future spec revisions:
 
-- `SerializedAudioBackend.sample_rate` is hardcoded to `48000` on save and SHOULD be
-  ignored in favour of `AudioProject.sample_rate` / `AudioPoolEntry.sample_rate`.
 - `MediaKind::Video` (`1`) is defined but never written; video media is always an
   external file via `VideoClip.file_path`.
-- `RasterKeyframe.media_path` is serialized but unused by the SQLite path (vestigial
-  legacy-ZIP linkage).
-- The reference writer's `SaveSettings` fields `auto_embed_threshold_bytes`,
-  `force_embed_all`, and `force_link_all` are not consulted by the current save path;
-  only the large-media mode is.
 - The project `version` check is exact-match with no compatibility window; a future
   revision should define semantic-version tolerance before bumping it.
 
+(Earlier revisions of this section flagged a hardcoded save sample rate, a vestigial
+`RasterKeyframe.media_path` field, and unused `SaveSettings` fields; these have since
+been fixed/removed.)
+
 ## 16. Inspecting a `.beam` file
 
 Because the container is plain SQLite, any `.beam` (SQLite variant) can be inspected

daw-backend/src/audio/project.rs

@@ -41,6 +41,11 @@ impl Project {
         }
     }
 
+    /// The project's system sample rate in Hz.
+    pub fn sample_rate(&self) -> u32 {
+        self.sample_rate
+    }
+
     /// Generate a new unique track ID
     fn next_id(&mut self) -> TrackId {
         let id = self.next_track_id;

lightningbeam-ui/lightningbeam-core/src/file_io.rs

@@ -88,15 +88,6 @@ impl Default for LargeMediaMode {
 /// Settings for saving a project
 #[derive(Debug, Clone)]
 pub struct SaveSettings {
-    /// Automatically embed files smaller than this size (in bytes)
-    pub auto_embed_threshold_bytes: u64,
-
-    /// Force embedding all media files
-    pub force_embed_all: bool,
-
-    /// Force linking all media files (don't embed any)
-    pub force_link_all: bool,
-
     /// How to store files at/above [`LARGE_MEDIA_THRESHOLD`] (pack vs reference).
     /// `Ask` behaves as `Reference` here (safe default: don't bloat the DB).
     pub large_media_mode: LargeMediaMode,
@@ -105,9 +96,6 @@ pub struct SaveSettings {
 impl Default for SaveSettings {
     fn default() -> Self {
         Self {
-            auto_embed_threshold_bytes: 10_000_000, // 10 MB
-            force_embed_all: false,
-            force_link_all: false,
             large_media_mode: LargeMediaMode::Ask,
         }
     }
@@ -269,7 +257,7 @@ pub fn save_beam(
     audio_pool_entries: Vec<AudioPoolEntry>,
     layer_to_track_map: &std::collections::HashMap<uuid::Uuid, u32>,
     thumbnail_blobs: &std::collections::HashMap<uuid::Uuid, Vec<u8>>,
-    _settings: &SaveSettings,
+    settings: &SaveSettings,
 ) -> Result<(), String> {
     let fn_start = std::time::Instant::now();
     eprintln!("📊 [SAVE_BEAM] Starting save_beam() (SQLite container)...");
@@ -349,7 +337,7 @@ pub fn save_beam(
                 // (`Ask` == reference); smaller files are always packed.
                 let reference_it = entry.is_video_audio
                     || (size >= LARGE_MEDIA_THRESHOLD
-                        && _settings.large_media_mode != LargeMediaMode::Pack);
+                        && settings.large_media_mode != LargeMediaMode::Pack);
                 if reference_it {
                     referenced = Some(rel.clone());
                 } else {
@@ -498,7 +486,7 @@ pub fn save_beam(
         modified: now.clone(),
         ui_state: document.clone(),
         audio_backend: SerializedAudioBackend {
-            sample_rate: 48000, // TODO: Get from audio engine
+            sample_rate: audio_project.sample_rate(),
             project: audio_project.clone(),
             audio_pool_entries: modified_entries,
             layer_to_track_map: layer_to_track_map.clone(),
@@ -879,8 +867,11 @@ fn load_beam_zip_legacy(path: &Path) -> Result<LoadedProject, String> {
     for layer in document.root.children.iter_mut() {
         if let crate::layer::AnyLayer::Raster(rl) = layer {
             for kf in &mut rl.keyframes {
-                if !kf.media_path.is_empty() {
+                // Legacy ZIP raster entries are named "media/raster/<uuid>.png",
-                    match zip.by_name(&kf.media_path) {
+                // derivable from the keyframe id (the old `media_path` field).
+                let entry_path = format!("media/raster/{}.png", kf.id);
+                {
+                    match zip.by_name(&entry_path) {
                         Ok(mut png_file) => {
                             let mut png_bytes = Vec::new();
                             let _ = png_file.read_to_end(&mut png_bytes);
@@ -890,7 +881,7 @@ fn load_beam_zip_legacy(path: &Path) -> Result<LoadedProject, String> {
                                     kf.raw_pixels = rgba.into_raw();
                                     raster_load_count += 1;
                                 }
-                                Err(e) => eprintln!("⚠️ [LOAD_BEAM] Failed to decode raster PNG {}: {}", kf.media_path, e),
+                                Err(e) => eprintln!("⚠️ [LOAD_BEAM] Failed to decode raster PNG {}: {}", entry_path, e),
                             }
                         }
                         Err(_) => {

lightningbeam-ui/lightningbeam-core/src/raster_layer.rs

@@ -111,8 +111,6 @@ pub struct RasterKeyframe {
     pub time: f64,
     pub width: u32,
     pub height: u32,
-    /// ZIP-relative path: `"media/raster/<uuid>.png"`
-    pub media_path: String,
     /// Stroke history (for potential replay / future non-destructive editing)
     pub stroke_log: Vec<StrokeRecord>,
     pub tween_after: TweenType,
@@ -157,13 +155,11 @@ impl RasterKeyframe {
 
     pub fn new(time: f64, width: u32, height: u32) -> Self {
         let id = Uuid::new_v4();
-        let media_path = format!("media/raster/{}.png", id);
         Self {
             id,
             time,
             width,
             height,
-            media_path,
             stroke_log: Vec::new(),
             tween_after: TweenType::Hold,
             raw_pixels: Vec::new(),
@@ -264,10 +260,6 @@ impl RasterLayer {
             .map(|pos| self.keyframes.remove(pos))
     }
 
-    /// Return the ZIP-relative PNG path for the active keyframe at `time`, or `None`.
-    pub fn buffer_path_at_time(&self, time: f64) -> Option<&str> {
-        self.keyframe_at(time).map(|kf| kf.media_path.as_str())
-    }
 }
 
 // Delegate all LayerTrait methods to self.layer

lightningbeam-ui/lightningbeam-editor/src/main.rs

@@ -731,7 +731,6 @@ impl FileOperationsWorker {
 
         let settings = SaveSettings {
             large_media_mode,
-            ..SaveSettings::default()
         };
         match save_beam(&path, &document, &mut audio_project, audio_pool_entries, layer_to_track_map, &thumbnail_blobs, &settings) {
             Ok(()) => {