diff --git a/cli/src/generation_input.rs b/cli/src/generation_input.rs
index 74f2ec61..4a18af64 100644
--- a/cli/src/generation_input.rs
+++ b/cli/src/generation_input.rs
@@ -10,12 +10,14 @@
 //! **Experimental, `#[doc(hidden)]`**: a stability-exempt seam for tooling, not
 //! a public library surface.
 
+use std::collections::HashMap;
 use std::fs;
 use std::path::Path;
 
 use griff_core::corpus::{source_sha256, ChunkMeta};
 use griff_core::generation_input::{corpus_material, prepare_chunk, LoadedChunk};
 use griff_core::import;
+use griff_core::score::Score;
 
 pub use griff_core::generation_input::{
     bar_rhythms, generation_request_from_score, gesture_control_from_chunks, CorpusMaterial,
@@ -33,6 +35,17 @@ pub use griff_core::generation_input::{
 /// # Errors
 /// [`GenerationInputError::Corpus`] when `dir` cannot be read.
 pub fn load_corpus_material(dir: &Path) -> Result<CorpusMaterial, GenerationInputError> {
+    load_corpus_material_with(dir, |bytes| import::import_score_auto(bytes).ok())
+}
+
+/// The load loop with the source importer injected, so a test can count how
+/// often a source is parsed. The corpus is ~25x redundant (≈400 sources behind
+/// ≈9,900 chunks), so parsing each tab once instead of once per chunk is the
+/// difference between a ~112 s and a ~4.5 s full load — measured, not guessed.
+fn load_corpus_material_with(
+    dir: &Path,
+    mut import: impl FnMut(&[u8]) -> Option<Score>,
+) -> Result<CorpusMaterial, GenerationInputError> {
     let entries = fs::read_dir(dir).map_err(|e| {
         GenerationInputError::Corpus(format!("cannot read corpus dir {}: {e}", dir.display()))
     })?;
@@ -43,10 +56,11 @@ pub fn load_corpus_material(dir: &Path) -> Result<CorpusMaterial, GenerationInpu
         .collect();
     record_names.sort_unstable();
 
+    let mut cache: HashMap<String, Score> = HashMap::new();
     let mut loaded = Vec::new();
     let mut skipped = Vec::new();
     for name in record_names {
-        match load_chunk(dir, &name) {
+        match load_chunk(dir, &name, &mut cache, &mut import) {
             Some(chunk) => loaded.push(chunk),
             None => skipped.push(name),
         }
@@ -54,22 +68,182 @@ pub fn load_corpus_material(dir: &Path) -> Result<CorpusMaterial, GenerationInpu
     Ok(corpus_material(loaded, skipped))
 }
 
-/// Reads one chunk record and its source tab off disk, then prepares it through
-/// core. `None` when the record does not parse, the source is
-/// missing/unimportable, or the prepared slice carries no sounding track — the
-/// caller reports the record as skipped.
-fn load_chunk(dir: &Path, record_name: &str) -> Option<LoadedChunk> {
+/// Reads one chunk record and prepares it through core, importing its source
+/// tab (or reusing an already-parsed one from `cache`). `None` when the record
+/// does not parse, the source is missing/unimportable/hash-mismatched, or the
+/// prepared slice carries no sounding track — the caller reports it as skipped.
+fn load_chunk(
+    dir: &Path,
+    record_name: &str,
+    cache: &mut HashMap<String, Score>,
+    import: &mut impl FnMut(&[u8]) -> Option<Score>,
+) -> Option<LoadedChunk> {
     let meta: ChunkMeta =
         serde_json::from_str(&fs::read_to_string(dir.join(record_name)).ok()?).ok()?;
-    let bytes = fs::read(dir.join(&meta.source.filename)).ok()?;
-    // A filename is not an identity: when the record pins the source's hash
-    // (schema v9), a same-named but different file must not silently supply the
-    // notes. A mismatch is a load failure, reported like a missing source.
-    if let Some(expected) = &meta.source.sha256 {
-        if &source_sha256(&bytes) != expected {
-            return None;
+    // Key the parsed source by its content hash (v9) — falling back to the
+    // filename for pre-v9 records — so every chunk of one tab reuses a single
+    // parse. Determinism is unchanged: `prepare_chunk` slices an immutable
+    // `&Score`, so a shared parse yields exactly the per-chunk-parse result.
+    let key = meta
+        .source
+        .sha256
+        .clone()
+        .unwrap_or_else(|| meta.source.filename.clone());
+    if !cache.contains_key(&key) {
+        let bytes = fs::read(dir.join(&meta.source.filename)).ok()?;
+        // A filename is not an identity: when the record pins the source's hash
+        // (schema v9), a same-named but different file must not silently supply
+        // the notes. A mismatch is a load failure — and a cache miss, so the
+        // check runs for every distinct expected hash, never bypassed by reuse.
+        if let Some(expected) = &meta.source.sha256 {
+            if &source_sha256(&bytes) != expected {
+                return None;
+            }
+        }
+        cache.insert(key.clone(), import(&bytes)?);
+    }
+    prepare_chunk(meta, cache.get(&key)?)
+}
+
+#[cfg(test)]
+mod tests {
+    #![allow(clippy::expect_used, clippy::unwrap_used)]
+
+    use super::{import, load_corpus_material_with, source_sha256, Score};
+    use griff_core::corpus::{ChunkId, ChunkMeta, SourceFormat, SourceRef};
+    use griff_core::event::{NoteMarks, Pitch, Tempo, Ticks, TimeSignature, Tuning, Velocity};
+    use griff_core::midi;
+    use griff_core::score::{
+        AtomEvent, AtomNote, EventGroup, EventGroupKind, LossReport, MasterBar, RepeatMarker,
+        Track, Voice,
+    };
+    use griff_core::slice::TickRange;
+    use std::cell::Cell;
+    use std::{env, fs, process};
+
+    fn note(start: u32, pitch: u8) -> AtomEvent {
+        AtomEvent::Note(AtomNote {
+            absolute_start: Ticks(start),
+            duration: Ticks(480),
+            pitch: Pitch::new(pitch).unwrap(),
+            velocity: Velocity::new(90).unwrap(),
+            marks: NoteMarks::empty(),
+            position: None,
+        })
+    }
+
+    fn two_bar_source() -> Score {
+        let master_bars = (0..2usize)
+            .map(|i| {
+                let start = u32::try_from(i).unwrap().saturating_mul(1920);
+                MasterBar {
+                    index: i,
+                    tick_range: TickRange::new(Ticks(start), Ticks(start.saturating_add(1920)))
+                        .unwrap(),
+                    time_signature: TimeSignature {
+                        numerator: 4,
+                        denominator: 4,
+                    },
+                    tempo: Tempo::new(120.0).unwrap(),
+                    repeat: RepeatMarker::default(),
+                }
+            })
+            .collect();
+        let atoms = [
+            note(0, 40),
+            note(480, 43),
+            note(960, 45),
+            note(1440, 47),
+            note(1920, 50),
+            note(2400, 47),
+            note(2880, 45),
+            note(3360, 43),
+        ];
+        Score {
+            ticks_per_quarter: 480,
+            master_bars,
+            tracks: vec![Track {
+                name: None,
+                channel: 0,
+                voices: vec![Voice {
+                    id: 0,
+                    event_groups: atoms
+                        .into_iter()
+                        .map(|a| EventGroup {
+                            kind: EventGroupKind::Single,
+                            atoms: vec![a],
+                            technique_spans: Vec::new(),
+                        })
+                        .collect(),
+                }],
+                tuning: Tuning::standard_e(),
+            }],
+            source_meta: None,
+            loss: LossReport::new(),
         }
     }
-    let source = import::import_score_auto(&bytes).ok()?;
-    prepare_chunk(meta, &source)
+
+    fn chunk_meta(id: &str, sha: &str, bars: (u32, u32)) -> ChunkMeta {
+        ChunkMeta {
+            id: ChunkId(id.to_owned()),
+            title: String::new(),
+            source: SourceRef {
+                filename: "s.mid".to_owned(),
+                format: SourceFormat::Midi,
+                bar_range: Some(bars),
+                track_index: Some(0),
+                sha256: Some(sha.to_owned()),
+            },
+            tempo_bpm: 120.0,
+            ticks_per_quarter: 480,
+            time_signature: (4, 4),
+            tuning: "standard_e".to_owned(),
+            tags: Vec::new(),
+            boundaries: Vec::new(),
+            techniques: Vec::new(),
+            quality_flags: Vec::new(),
+            reviewer: None,
+            structure: None,
+            gesture: None,
+            complexity: None,
+            duplicate: None,
+            style_cohort: None,
+            ensemble: None,
+            rights: None,
+            created_at: String::new(),
+            updated_at: String::new(),
+        }
+    }
+
+    #[test]
+    fn one_source_is_parsed_once_for_all_its_chunks() {
+        let dir = env::temp_dir().join(format!("griff_loadcache_{}", process::id()));
+        fs::create_dir_all(&dir).unwrap();
+        let bytes = midi::export_score(&two_bar_source()).unwrap();
+        let sha = source_sha256(&bytes);
+        fs::write(dir.join("s.mid"), &bytes).unwrap();
+        for (id, bars) in [("a", (0_u32, 0_u32)), ("b", (1, 1))] {
+            fs::write(
+                dir.join(format!("{id}.chunk.json")),
+                serde_json::to_string(&chunk_meta(id, &sha, bars)).unwrap(),
+            )
+            .unwrap();
+        }
+
+        let imports = Cell::new(0_usize);
+        let material = load_corpus_material_with(&dir, |b| {
+            imports.set(imports.get().saturating_add(1));
+            import::import_score_auto(b).ok()
+        })
+        .expect("corpus loads");
+
+        assert_eq!(material.references.len(), 2, "both chunks load");
+        assert_eq!(
+            imports.get(),
+            1,
+            "the shared source is parsed once, not once per chunk"
+        );
+
+        fs::remove_dir_all(&dir).ok();
+    }
 }