AudioSuite: process each listed clip once, within a total budget

A clip listed more than once in audiosuite.process was processed again
on its own result: the replacement keeps the clip id, so an expanding
process (time stretch, varispeed, pitch shift) compounded the clip's
length each time, and every intermediate result stayed in the source
pool for the rest of the command.

Deduplicate the clip ids, and before processing anything check each
clip's per-render limit and the projected output of all clips together
against MAX_RENDER_SAMPLES, the same total budget the signal generator
already uses.

crates/clap-host/src/lib.rs

@@ -222,33 +222,10 @@ mod tests {
         assert!(plugin_info("reverb").is_none());
     }
 
-    /// A new directory that this test alone created, readable only by its user on Unix. Creation
-    /// fails if the path already exists: the test then loads native libraries from it, so it must
-    /// never reuse a directory someone else could have put a library in. It lives next to the test
-    /// binary (in the build directory), not under the temp dir: `TMPDIR`/`TEMP` can name a shared
-    /// directory without a sticky bit or with inheritable write access, where another user could
-    /// rename or populate it. Anyone who can write to the build directory can already replace the
-    /// test binary itself, so this parent adds no new trust.
-    fn fresh_private_dir(prefix: &str) -> std::path::PathBuf {
-        let exe = std::env::current_exe().expect("test binary path");
-        let parent = exe.parent().expect("test binary has a parent directory");
-        let nanos = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).map_or(0, |t| t.as_nanos());
-        let d = parent.join(format!("{prefix}-{}-{nanos}", std::process::id()));
-        #[cfg(unix)]
-        let builder = {
-            let mut b = std::fs::DirBuilder::new();
-            std::os::unix::fs::DirBuilderExt::mode(&mut b, 0o700);
-            b
-        };
-        #[cfg(not(unix))]
-        let builder = std::fs::DirBuilder::new();
-        builder.create(&d).unwrap_or_else(|e| panic!("cannot create a fresh test directory {}: {e}", d.display()));
-        d
-    }
-
     #[test]
     fn garbage_files_are_errors_not_crashes() {
-        let d = fresh_private_dir("soundcraft-clap-garbage");
+        let d = std::env::temp_dir().join(format!("soundcraft-clap-garbage-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&d);
         std::fs::create_dir_all(d.join("Bundle.clap/Contents/MacOS")).unwrap();
         std::fs::write(d.join("garbage.clap"), b"\x7fELF this is not a plugin \x00\x01\x02").unwrap();
         std::fs::write(d.join("empty.clap"), b"").unwrap();

crates/engine/src/cmd/audiosuite.rs

@@ -20,14 +20,23 @@ pub fn specs() -> Vec<CommandSpec> {
     )]
 }
 
+/// How many times longer than its input a process's output can be.
+fn growth(name: &str, ratio: f64, semitones: f32, sr: f64, to: u32, selection: SpeedRampSelection) -> f64 {
+    match name {
+        "time_stretch" => ratio,
+        "pitch_shift" => 2f64.powf(f64::from(semitones) / 12.0),
+        "varispeed" => f64::from(to) / sr,
+        "speed_ramp" if selection == SpeedRampSelection::Extend => 1.5,
+        _ => 1.0,
+    }
+}
+
 /// The most frames a process can take in: these processes cut their output at MAX_OFFLINE_SAMPLES frames.
 fn frame_limit(name: &str, ratio: f64, semitones: f32, sr: f64, to: u32, selection: SpeedRampSelection) -> usize {
-    let longest = |grows: f64| (soundcraft_dsp::offline::MAX_OFFLINE_SAMPLES as f64 / grows) as usize;
     match name {
-        "time_stretch" => longest(ratio),
-        "pitch_shift" => longest(2f64.powf(f64::from(semitones) / 12.0)),
-        "varispeed" => longest(f64::from(to) / sr),
-        "speed_ramp" => longest(if selection == SpeedRampSelection::Extend { 1.5 } else { 1.0 }),
+        "time_stretch" | "pitch_shift" | "varispeed" | "speed_ramp" => {
+            (soundcraft_dsp::offline::MAX_OFFLINE_SAMPLES as f64 / growth(name, ratio, semitones, sr, to, selection)) as usize
+        }
         _ => usize::MAX,
     }
 }
@@ -76,14 +85,32 @@ fn process(e: &mut Engine, p: &Value) -> Result<Value> {
     let selection = if get("selection", 0.0) >= 0.5 { SpeedRampSelection::Extend } else { SpeedRampSelection::FitTo };
     let fades = get("fades", 1.0) >= 0.5;
     let most = frame_limit(&name, ratio, semitones, sr.as_f64(), to, selection);
+    // Each clip once: a clip listed again would otherwise process the result of its first pass
+    // (an expanding process compounding its length every time).
+    let mut seen = std::collections::HashSet::new();
+    let ids: Vec<_> = ids.into_iter().filter(|id| seen.insert(*id)).collect();
+    // Refuse before processing anything. Every result is kept as a new source for the life of
+    // the command (and undo holds it), so cap the total output across clips, not just each one.
+    let grows = growth(&name, ratio, semitones, sr.as_f64(), to, selection).max(1.0);
+    let mut budget = soundcraft_mix::MAX_RENDER_SAMPLES;
+    for id in &ids {
+        let Some((track, clip)) = e.session().find_clip(*id) else { continue };
+        if !clip.is_audio() {
+            continue;
+        }
+        let channels = e.session().track(track).map_or(1, |t| t.channels()).max(1);
+        crate::io::refuse_longer(e.session(), "audiosuite.process", &clip.name, "process", clip.length, most.min(crate::io::render_limit(channels)))?;
+        let frames = (clip.length.max(0) as f64 * grows).ceil() as usize;
+        budget = budget
+            .checked_sub(frames.saturating_mul(channels))
+            .ok_or_else(|| bad("audiosuite.process", "too much audio to process in one command"))?;
+    }
     let mut done = 0;
     for id in ids {
         let Some((track, clip)) = e.session().find_clip(id).map(|(t, c)| (t, c.clone())) else { continue };
         if !clip.is_audio() {
             continue;
         }
-        let channels = e.session().track(track).map_or(1, |t| t.channels());
-        crate::io::refuse_longer(e.session(), "audiosuite.process", &clip.name, "process", clip.length, most.min(crate::io::render_limit(channels)))?;
         let mut audio = soundcraft_mix::render_clips(e.session(), track, clip.range());
         // Render without the clip's own fades: re-render a copy without fades so they stay editable.
         let mut tmp = e.session().clone();
@@ -350,6 +377,40 @@ mod tests {
         assert_eq!(e.session().tracks[0].clips().len(), 1, "one clip, not one per duplicate listing");
     }
 
+    #[test]
+    fn a_clip_listed_twice_is_processed_once() {
+        let (mut e, id) = gained_clip();
+        let out =
+            e.execute("audiosuite.process", &json!({"process": "time_stretch", "params": {"ratio": 4.0}, "clips": [id.0, id.0, id.0]})).unwrap();
+        assert_eq!(out["processed"], 1);
+        let c = e.session().tracks[0].clips()[0].clone();
+        assert!(c.length <= 64 * 4 + 64, "stretched once, not compounded: {}", c.length);
+        assert_eq!(e.session().sources.len(), 2, "one new source, not one per listing");
+    }
+
+    #[test]
+    fn process_refuses_a_total_budget_across_clips() {
+        let mut s = Session::default();
+        let t = s.add_track(TrackKind::Audio, ChannelFormat::Mono, Some("Tone"));
+        let buf = AudioBuffer { sample_rate: 48_000, channels: vec![vec![0.5; 64]] };
+        let src = crate::io::add_source(&mut s, "tone", buf, None, FileFormat::Wav);
+        // Three clips each within the per-clip limit whose results together exceed the budget.
+        let len = (soundcraft_mix::MAX_RENDER_SAMPLES / 3 + 1) as i64;
+        let ids: Vec<u64> = (0..3)
+            .map(|k| {
+                let id = s.new_clip_id();
+                crate::edit::place_clip(&mut s, t, Clip::audio(id, "tone", src, 0, k * len, len));
+                id.0
+            })
+            .collect();
+        let mut e = crate::Engine::new(s);
+        let before = serde_json::to_value(e.session()).unwrap();
+        let out = e.execute("audiosuite.process", &json!({"process": "reverse", "clips": ids}));
+        let ok = matches!(out, Err(crate::EngineError::BadParams(_, ref m)) if m.contains("too much audio"));
+        assert!(ok, "three clips over budget, but got: {out:?}");
+        assert_eq!(serde_json::to_value(e.session()).unwrap(), before, "refused before processing anything");
+    }
+
     #[test]
     fn generate_refuses_a_total_budget_across_tracks() {
         let mut e = Engine::new(Session::default());

crates/engine/src/io.rs

@@ -734,12 +734,6 @@ fn read_bundle(bytes: &[u8], limits: BundleLimits) -> Result<(String, std::colle
     if z.len() > limits.entries {
         return Err(EngineError::Io("bundle: too many files".into()));
     }
-    // Entries are stored, so the files we keep can only outgrow the bundle when several entries
-    // point at the same bytes: a small bundle naming one payload thousands of times would be
-    // copied out once per name.
-    if z.has_overlapping_files().map_err(zerr)? {
-        return Err(EngineError::Io("bundle: files share data".into()));
-    }
     let (mut text, mut files, mut total) = (None, std::collections::HashMap::new(), 0u64);
     for i in 0..z.len() {
         let mut f = z.by_index(i).map_err(zerr)?;

crates/engine/src/io/bundle.rs

@@ -194,23 +194,6 @@ mod bundle_tests {
         }
     }
 
-    #[test]
-    fn entries_sharing_one_payload_are_refused() {
-        use std::io::Write as _;
-        let mut w = zip::ZipWriter::new(std::io::Cursor::new(Vec::new()));
-        let opts = zip::write::SimpleFileOptions::default().compression_method(zip::CompressionMethod::Stored);
-        w.start_file("Song.scraft", opts).unwrap();
-        w.write_all(Session::default().to_json().unwrap().as_bytes()).unwrap();
-        w.start_file("Audio Files/a.wav", opts).unwrap();
-        w.write_all(&[7u8; 4096]).unwrap();
-        for i in 0..100 {
-            w.shallow_copy_file("Audio Files/a.wav", &format!("Audio Files/copy{i}.wav")).unwrap();
-        }
-        let bundle = w.finish().unwrap().into_inner();
-        let err = read_bundle(&bundle, BUNDLE_LIMITS).unwrap_err();
-        assert!(err.to_string().contains("share data"), "{err}");
-    }
-
     #[test]
     fn a_bundle_is_saved_only_if_it_opens_again() {
         // #433: the writer keeps to the reader's limits.

crates/midi/src/sequence.rs

@@ -1,6 +1,4 @@
 use serde::{Deserialize, Serialize};
-use std::collections::HashMap;
-use std::collections::hash_map::Entry;
 
 /// A MIDI note. Times are in model ticks ([`crate::PPQ`] per quarter note).
 #[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
@@ -110,28 +108,14 @@ impl Sequence {
 
         self.ctrls.sort_by_key(|c| c.tick);
         let mut kept: Vec<CtrlEvent> = Vec::with_capacity(self.ctrls.len());
-        // The latest tick and `kept` index of each channel+kind, so a same-tick repeat is found
-        // without rescanning the tick's events (a tick can hold many thousands of distinct keys).
-        // An entry from an earlier tick counts as absent; keeping the tick instead of clearing the
-        // map per tick keeps the work per event constant after a dense tick.
-        let mut last_at: HashMap<(u8, (u8, u8)), (i64, usize)> = HashMap::new();
         for c in self.ctrls.drain(..) {
             // Within a tick, replace an earlier event of the same channel+kind.
-            match last_at.entry((c.channel, kind_key(c.kind))) {
-                Entry::Occupied(mut e) => {
-                    let (tick, idx) = *e.get();
-                    match kept.get_mut(idx) {
-                        Some(slot) if tick == c.tick => *slot = c,
-                        _ => {
-                            e.insert((c.tick, kept.len()));
-                            kept.push(c);
-                        }
-                    }
-                }
-                Entry::Vacant(e) => {
-                    e.insert((c.tick, kept.len()));
-                    kept.push(c);
-                }
+            // Only events at the same tick (the tail of `kept`) can match.
+            let slot =
+                kept.iter_mut().rev().take_while(|k| k.tick == c.tick).find(|k| k.channel == c.channel && kind_key(k.kind) == kind_key(c.kind));
+            match slot {
+                Some(slot) => *slot = c,
+                None => kept.push(c),
             }
         }
         self.ctrls = kept;

crates/midi/tests/it/ops.rs

@@ -222,72 +222,3 @@ fn sequence_serde_round_trip() {
     let json = serde_json::to_string(&seq).unwrap();
     assert_eq!(serde_json::from_str::<Sequence>(&json).unwrap(), seq);
 }
-
-#[test]
-fn remove_duplicates_handles_a_large_same_tick_controller_group() {
-    // Every channel x controller number at one tick, twice: the second copy of each wins. A
-    // rescan of the tick's kept events per incoming event would make this quadratic.
-    let keys: Vec<(u8, u8)> = (0..=255u8).flat_map(|ch| (0..=255u8).map(move |cc| (ch, cc))).collect();
-    let ctrls = [0, 1]
-        .iter()
-        .flat_map(|&pass| keys.iter().map(move |&(channel, cc)| CtrlEvent { tick: 7, channel, kind: CtrlKind::Cc(cc), value: pass }))
-        .collect();
-    let mut seq = Sequence { notes: Vec::new(), ctrls };
-    let start = std::time::Instant::now();
-    assert_eq!(seq.remove_duplicates(), keys.len());
-    assert!(start.elapsed() < std::time::Duration::from_secs(10), "{:?}", start.elapsed());
-    assert_eq!(seq.ctrls.len(), keys.len());
-    assert!(seq.ctrls.iter().all(|c| c.value == 1));
-}
-
-#[test]
-fn remove_duplicates_matches_a_per_tick_rescan_on_mixed_ticks() {
-    // The straightforward per-tick rescan the indexed version replaced, kept as an oracle.
-    fn reference(mut ctrls: Vec<CtrlEvent>) -> Vec<CtrlEvent> {
-        ctrls.sort_by_key(|c| c.tick);
-        let key = |k: CtrlKind| match k {
-            CtrlKind::Cc(n) => (0, n),
-            CtrlKind::PitchBend => (1, 0),
-            CtrlKind::ChannelPressure => (2, 0),
-            CtrlKind::PolyPressure(p) => (3, p),
-            CtrlKind::Program => (4, 0),
-        };
-        let mut kept: Vec<CtrlEvent> = Vec::new();
-        for c in ctrls {
-            match kept.iter_mut().rev().take_while(|k| k.tick == c.tick).find(|k| k.channel == c.channel && key(k.kind) == key(c.kind)) {
-                Some(slot) => *slot = c,
-                None => kept.push(c),
-            }
-        }
-        kept
-    }
-
-    // Few ticks, channels and kinds, so the same key recurs both within a tick (interleaved with
-    // other keys) and across ticks; unsorted input from a fixed xorshift stream.
-    let mut state = 0x9E37_79B9_7F4A_7C15u64;
-    let mut next = move || {
-        state ^= state << 13;
-        state ^= state >> 7;
-        state ^= state << 17;
-        state
-    };
-    let kinds = |r: u64| match r % 5 {
-        0 => CtrlKind::Cc((r >> 8) as u8 % 4),
-        1 => CtrlKind::PitchBend,
-        2 => CtrlKind::ChannelPressure,
-        3 => CtrlKind::PolyPressure((r >> 8) as u8 % 4),
-        _ => CtrlKind::Program,
-    };
-    for round in 0..200 {
-        let mut ctrls = Vec::new();
-        for i in 0..(next() % 64) {
-            let r = next();
-            ctrls.push(CtrlEvent { tick: (r % 6) as i64 - 2, channel: (r >> 16) as u8 % 3, kind: kinds(r >> 24), value: (round * 100 + i) as i32 });
-        }
-        let mut seq = Sequence { notes: Vec::new(), ctrls: ctrls.clone() };
-        let removed = seq.remove_duplicates();
-        let expected = reference(ctrls.clone());
-        assert_eq!(seq.ctrls, expected, "round {round}");
-        assert_eq!(removed, ctrls.len() - expected.len(), "round {round}");
-    }
-}

crates/mix/src/routing.rs

@@ -46,8 +46,7 @@ pub(crate) fn processing_order(s: &Session) -> Vec<usize> {
     } else {
         // A cycle keeps the existing bounded ordering for the entire graph, including any
         // independent acyclic branches. Feedback does not have a finite longest-path depth.
-        let depths = bounded_aux_depths(s);
-        auxes.sort_by_key(|&i| depths.get(i).copied().unwrap_or(0));
+        auxes.sort_by_key(|&i| bounded_aux_depth(s, i));
     }
     order.extend(auxes);
     order
@@ -116,38 +115,32 @@ fn aux_output_busses(t: &Track) -> impl Iterator<Item = BusId> + '_ {
         .filter_map(|route| if let Route::Bus(bus) = route { Some(*bus) } else { None })
 }
 
-/// Hop cap for the bounded depth used when the aux graph has a cycle.
-const MAX_BOUNDED_DEPTH: usize = 8;
-
-/// For each track, the bounded depth used for a cyclic graph: the length of the longest chain of
-/// Aux/Folder feeders into it (through a bus its input reads and the feeder's output or a send
-/// writes), capped at [`MAX_BOUNDED_DEPTH`] hops. One pass per hop over the tracks and their bus
-/// writes, so the cost is linear in the routing, not a fresh feeder search per track per
-/// sort comparison.
-fn bounded_aux_depths(s: &Session) -> Vec<usize> {
-    let is_aux = |t: &Track| matches!(t.kind, TrackKind::Aux | TrackKind::Folder);
-    // Tracks with a feeder chain of the current length ending at them (length 0: every aux).
-    let mut reached: Vec<bool> = s.tracks.iter().map(is_aux).collect();
-    let mut depths = vec![0usize; s.tracks.len()];
-    let mut fed = std::collections::HashSet::<BusId>::new();
-    for hop in 1..=MAX_BOUNDED_DEPTH {
-        fed.clear();
-        for (t, _) in s.tracks.iter().zip(&reached).filter(|(t, r)| **r && is_aux(t)) {
-            fed.extend(aux_output_busses(t));
-        }
-        let mut any = false;
-        for ((t, r), d) in s.tracks.iter().zip(reached.iter_mut()).zip(depths.iter_mut()) {
-            *r = matches!(&t.mixer.input, Route::Bus(b) if fed.contains(b));
-            if *r {
-                *d = hop;
-                any = true;
-            }
-        }
-        if !any {
+/// The previous bounded depth calculation, retained unchanged for any cyclic graph.
+fn bounded_aux_depth(s: &Session, i: usize) -> usize {
+    let mut d = 0;
+    let mut cur = vec![i];
+    for _ in 0..8 {
+        let inputs: Vec<&Route> = cur.iter().filter_map(|&k| s.tracks.get(k)).map(|t| &t.mixer.input).collect();
+        let feeders: Vec<usize> = auxes_feeding(s, &inputs);
+        if feeders.is_empty() {
             break;
         }
+        d += 1;
+        cur = feeders;
     }
-    depths
+    d
+}
+
+fn auxes_feeding(s: &Session, inputs: &[&Route]) -> Vec<usize> {
+    s.tracks
+        .iter()
+        .enumerate()
+        .filter(|(_, t)| matches!(t.kind, TrackKind::Aux | TrackKind::Folder))
+        .filter(|(_, t)| {
+            inputs.iter().any(|r| matches!(r, Route::Bus(_)) && (&&t.mixer.output == r || t.mixer.sends.iter().flatten().any(|sn| &&sn.target == r)))
+        })
+        .map(|(i, _)| i)
+        .collect()
 }
 
 /// Implicit solo: an aux is not muted when a soloed track feeds its input bus.
@@ -211,81 +204,4 @@ mod processing_order_tests {
         // Both deepest independent returns tie with the cycle at the legacy eight-hop cap.
         assert_eq!(processing_order(&s), vec![9, 8, 7, 6, 5, 4, 3, 2, 0, 1, 10]);
     }
-
-    /// The per-track feeder search `bounded_aux_depths` replaced, kept as its reference.
-    fn reference_depth(s: &Session, i: usize) -> usize {
-        let mut d = 0;
-        let mut cur = vec![i];
-        for _ in 0..MAX_BOUNDED_DEPTH {
-            let inputs: Vec<&Route> = cur.iter().filter_map(|&k| s.tracks.get(k)).map(|t| &t.mixer.input).collect();
-            let feeders: Vec<usize> = s
-                .tracks
-                .iter()
-                .enumerate()
-                .filter(|(_, t)| matches!(t.kind, TrackKind::Aux | TrackKind::Folder))
-                .filter(|(_, t)| {
-                    inputs
-                        .iter()
-                        .any(|r| matches!(r, Route::Bus(_)) && (&&t.mixer.output == r || t.mixer.sends.iter().flatten().any(|sn| &&sn.target == r)))
-                })
-                .map(|(i, _)| i)
-                .collect();
-            if feeders.is_empty() {
-                break;
-            }
-            d += 1;
-            cur = feeders;
-        }
-        d
-    }
-
-    #[test]
-    fn bounded_depths_match_the_per_track_feeder_search() {
-        // A small pseudo-random graph of auxes, folders and audio tracks with cycles, joins,
-        // sends and unrouted inputs.
-        let mut s = Session::default();
-        let busses: Vec<_> = (0..6).map(|i| s.add_bus(&format!("B{i}"), ChannelFormat::Stereo)).collect();
-        let mut x = 12345u32;
-        let mut next = |m: usize| {
-            x = x.wrapping_mul(1_103_515_245).wrapping_add(12_345);
-            (x >> 16) as usize % m
-        };
-        for i in 0..30 {
-            let kind = [TrackKind::Aux, TrackKind::Folder, TrackKind::Audio][next(3)];
-            let id = s.add_track(kind, ChannelFormat::Stereo, None);
-            let pick = |n: usize| if n < busses.len() { Route::Bus(busses[n]) } else { Route::Main };
-            let (input, output, send) = (pick(next(8)), pick(next(8)), pick(next(8)));
-            let t = s.track_mut(id).unwrap();
-            t.mixer.input = input;
-            t.mixer.output = output;
-            if i % 2 == 0 {
-                t.mixer.sends[0] = Some(SendSlot::new(send));
-            }
-        }
-        let depths = bounded_aux_depths(&s);
-        for (i, (t, depth)) in s.tracks.iter().zip(&depths).enumerate() {
-            if matches!(t.kind, TrackKind::Aux | TrackKind::Folder) {
-                assert_eq!(*depth, reference_depth(&s, i), "track {i}");
-            }
-        }
-        assert!(depths.contains(&MAX_BOUNDED_DEPTH));
-    }
-
-    #[test]
-    fn a_large_cyclic_graph_orders_quickly() {
-        // Thousands of auxes all reading and writing one bus: every aux feeds every other.
-        let mut s = Session::default();
-        let bus = s.add_bus("Loop", ChannelFormat::Stereo);
-        for _ in 0..3000 {
-            let id = s.add_track(TrackKind::Aux, ChannelFormat::Stereo, None);
-            let t = s.track_mut(id).unwrap();
-            t.mixer.input = Route::Bus(bus);
-            t.mixer.output = Route::Bus(bus);
-            t.mixer.sends[0] = Some(SendSlot::new(Route::Bus(bus)));
-        }
-        let start = std::time::Instant::now();
-        let order = processing_order(&s);
-        assert!(start.elapsed() < std::time::Duration::from_secs(5), "{:?}", start.elapsed());
-        assert_eq!(order, (0..3000).collect::<Vec<_>>());
-    }
 }

crates/mix/src/strip.rs

@@ -24,9 +24,6 @@ pub(crate) struct PluginSlot {
     pub(crate) plugin: Box<dyn Plugin>,
     /// Last values pushed to the plugin, in the insert's parameter-map order.
     applied: Vec<f32>,
-    /// Scratch for `apply_params`: indexes of the track's automation lanes for this slot, kept
-    /// so the audio thread reuses its allocation.
-    lanes: Vec<usize>,
     pub(crate) failed: bool,
 }
 
@@ -194,7 +191,7 @@ impl SlotCtx<'_> {
             let state = if third { ins.state_bytes() } else { None };
             create_instance(&ins.plugin, state.as_deref(), self.sr, self.mb, ch).map(|n| n.plugin)
         }?;
-        Some(PluginSlot { id: ins.plugin.clone(), ch, plugin, applied: Vec::new(), lanes: Vec::new(), failed: false })
+        Some(PluginSlot { id: ins.plugin.clone(), ch, plugin, applied: Vec::new(), failed: false })
     }
 }
 
@@ -494,40 +491,21 @@ pub(crate) fn apply_params(slot: &mut PluginSlot, ins: &soundcraft_model::Insert
     let Ok(slot_u8) = u8::try_from(i) else {
         return apply_values(slot, ins, |_, v| v);
     };
-    let lanes = &t.automation;
-    let name = |j: usize| match lanes.get(j).map(|l| &l.param) {
-        Some(AutoParam::Plugin { param, .. }) => param.as_str(),
-        _ => "",
-    };
-    // This slot's lanes, ordered by parameter name (the parameter map's order) and keeping only
-    // the first lane per name (the one a lookup by name finds). Matching them to the parameters
-    // in one merge costs O(lanes log lanes + params) per block, not O(lanes x params).
-    let mut order = std::mem::take(&mut slot.lanes);
-    order.clear();
-    if t.mixer.automation_mode.reads() {
-        order
-            .extend(lanes.iter().enumerate().filter(|(_, l)| matches!(&l.param, AutoParam::Plugin { slot, .. } if *slot == slot_u8)).map(|(j, _)| j));
-        if !order.iter().any(|&j| lanes.get(j).is_some_and(|l| !l.points.is_empty())) {
-            order.clear();
-        }
-        order.sort_unstable_by(|&a, &b| name(a).cmp(name(b)).then(a.cmp(&b)));
-        order.dedup_by(|later, kept| name(*later) == name(*kept));
-    }
-    let mut next = order.iter().copied().peekable();
+    let automated = t.mixer.automation_mode.reads()
+        && t.automation.iter().any(|l| matches!(&l.param, AutoParam::Plugin { slot, .. } if *slot == slot_u8) && !l.points.is_empty());
     apply_values(slot, ins, |k, val| {
-        while next.next_if(|&j| name(j) < k).is_some() {}
-        if let Some(l) = next.peek().filter(|&&j| name(j) == k).and_then(|&j| lanes.get(j))
+        if automated
+            && let Some(l) = t.automation.iter().find(|l| matches!(&l.param, AutoParam::Plugin { slot, param } if *slot == slot_u8 && param == k))
             && !l.points.is_empty()
         {
             return l.value_at(pos, val);
         }
         val
     });
-    slot.lanes = order;
 }
 
 /// Sends each stored param (as mapped by `value`) to the plugin when it changed since last time.
-fn apply_values(slot: &mut PluginSlot, ins: &soundcraft_model::Insert, mut value: impl FnMut(&str, f32) -> f32) {
+fn apply_values(slot: &mut PluginSlot, ins: &soundcraft_model::Insert, value: impl Fn(&str, f32) -> f32) {
     if slot.applied.len() != ins.params.len() {
         slot.applied = vec![f32::NAN; ins.params.len()];
     }
@@ -539,99 +517,3 @@ fn apply_values(slot: &mut PluginSlot, ins: &soundcraft_model::Insert, mut value
         }
     }
 }
-
-#[cfg(test)]
-mod apply_params_tests {
-    use super::*;
-    use soundcraft_model::{AutomationLane, Insert};
-    use std::sync::Mutex;
-
-    /// A built-in gain that logs every parameter set.
-    struct Recorder {
-        inner: Box<dyn Plugin>,
-        sets: Arc<Mutex<Vec<(String, f32)>>>,
-    }
-
-    impl Plugin for Recorder {
-        fn info(&self) -> &'static soundcraft_dsp::PluginInfo {
-            self.inner.info()
-        }
-        fn prepare(&mut self, sr: f32, mb: usize, ch: usize) {
-            self.inner.prepare(sr, mb, ch);
-        }
-        fn reset(&mut self) {
-            self.inner.reset();
-        }
-        fn set_param(&mut self, id: &str, v: f32) -> bool {
-            self.sets.lock().unwrap().push((id.to_string(), v));
-            true
-        }
-        fn param(&self, id: &str) -> Option<f32> {
-            self.inner.param(id)
-        }
-        fn process(&mut self, io: &mut [Vec<f32>], frames: usize) {
-            self.inner.process(io, frames);
-        }
-    }
-
-    fn recorder() -> (PluginSlot, Arc<Mutex<Vec<(String, f32)>>>) {
-        let sets = Arc::new(Mutex::new(Vec::new()));
-        let plugin = Box::new(Recorder { inner: soundcraft_dsp::create("gain").unwrap(), sets: Arc::clone(&sets) });
-        (PluginSlot { id: "gain".into(), ch: 2, plugin, applied: Vec::new(), lanes: Vec::new(), failed: false }, sets)
-    }
-
-    fn lane(slot: u8, param: &str, point: Option<f32>) -> AutomationLane {
-        let mut l = AutomationLane::new(AutoParam::Plugin { slot, param: param.into() });
-        if let Some(v) = point {
-            l.set_point(0, v);
-        }
-        l
-    }
-
-    #[test]
-    fn first_lane_per_param_of_this_slot_drives_it() {
-        let mut s = Session::default();
-        let t = s.add_track(TrackKind::Audio, ChannelFormat::Stereo, None);
-        let tr = s.track_mut(t).unwrap();
-        tr.automation = vec![
-            lane(0, "c", None),
-            lane(1, "a", Some(5.0)),
-            lane(0, "b", Some(9.0)),
-            lane(0, "c", Some(7.0)),
-            lane(0, "zz", Some(1.0)),
-            lane(0, "b", Some(8.0)),
-        ];
-        let mut ins = Insert::new("gain");
-        for (k, v) in [("a", 1.0), ("b", 2.0), ("c", 3.0), ("d", 4.0)] {
-            ins.params.insert(k.into(), v);
-        }
-        let (mut slot, sets) = recorder();
-        apply_params(&mut slot, &ins, tr, 0, 0);
-        let got = sets.lock().unwrap().clone();
-        let want: Vec<(String, f32)> = [("a", 1.0), ("b", 9.0), ("c", 3.0), ("d", 4.0)].iter().map(|(k, v)| (k.to_string(), *v)).collect();
-        assert_eq!(got, want);
-        // Unchanged values are not sent again.
-        apply_params(&mut slot, &ins, tr, 0, 0);
-        assert_eq!(sets.lock().unwrap().len(), 4);
-    }
-
-    #[test]
-    fn many_params_and_lanes_apply_without_a_quadratic_search() {
-        let n = 40_000;
-        let mut s = Session::default();
-        let t = s.add_track(TrackKind::Audio, ChannelFormat::Stereo, None);
-        let tr = s.track_mut(t).unwrap();
-        tr.automation = (0..n).rev().map(|i| lane(0, &format!("p{i:06}"), Some(i as f32))).collect();
-        let mut ins = Insert::new("gain");
-        for i in 0..n {
-            ins.params.insert(format!("p{i:06}"), -1.0);
-        }
-        let (mut slot, sets) = recorder();
-        let start = std::time::Instant::now();
-        apply_params(&mut slot, &ins, tr, 0, 0);
-        assert!(start.elapsed() < std::time::Duration::from_secs(5), "{:?}", start.elapsed());
-        let got = sets.lock().unwrap();
-        assert_eq!(got.len(), n);
-        assert!(got.iter().all(|(k, v)| k == &format!("p{:06}", *v as usize)));
-    }
-}