diff --git a/crates/ogar-action-handler/Cargo.toml b/crates/ogar-action-handler/Cargo.toml
index f9f3ed1..eff02f2 100644
--- a/crates/ogar-action-handler/Cargo.toml
+++ b/crates/ogar-action-handler/Cargo.toml
@@ -33,3 +33,6 @@ lance-graph-ontology = { git = "https://github.com/AdaWorldAPI/lance-graph", bra
 ogar-from-ruff = { path = "../ogar-from-ruff" }
 # On ruff `main` (O-2 de-pin done 2026-07-06); keep in lockstep with ogar-from-ruff.
 ruff_spo_triplet = { git = "https://github.com/AdaWorldAPI/ruff", branch = "main" }
+# DR64 relation composition (relcomp), for the lab probe
+# `tests/ogit_schema_composition.rs`. Test-only.
+dr-math-binding-probe = { git = "https://github.com/AdaWorldAPI/lance-graph", branch = "main" }
diff --git a/crates/ogar-action-handler/tests/ogit_schema_composition.rs b/crates/ogar-action-handler/tests/ogit_schema_composition.rs
new file mode 100644
index 0000000..bab2ad3
--- /dev/null
+++ b/crates/ogar-action-handler/tests/ogit_schema_composition.rs
@@ -0,0 +1,381 @@
+//! Lab probe: OGIT's `ogit:allowed` edge whitelist composed as Boolean
+//! relations through lance-graph's DR64 relcomp kernel
+//! (`dr-math-binding-probe`), checked against naive enumeration.
+//!
+//! The input is [`OgitTables`]' `Allowed` lanes (`src`, `verb`, `dst`, one row
+//! per allowed edge). Two compositions:
+//!
+//! 1. **Chainable verb pairs.** `targets` (verb × type: verb `v` may end at
+//!    type `t`) composed with `sources` (type × verb: an edge with verb `w` may
+//!    start at `t`) gives verb × verb: `v ; w` is chainable when some type is a
+//!    target of `v` and a source of `w`. This is the schema-level composition
+//!    table a DT64 slot registry over OGIT verbs would need.
+//! 2. **Typed composition of named verbs.** For selected verbs, the type ×
+//!    type relation `R_v`, and `R_v ∘ R_w` and a three-verb chain in both
+//!    associations.
+//!
+//! Every relcomp result is compared pair by pair with an enumeration that
+//! shares no code with the kernel. The schema mirror of the inverse-pair
+//! candidates (`consistsOf` / `isPartOf`) is measured and printed; nothing is
+//! asserted about it, because schema mirroring is not evidence that the
+//! instance relations are inverse.
+//!
+//! The OGIT checkout is found like the other OGIT tests: `OGIT_FORK_PATH`,
+//! else `OGIT` next to this repository. A missing checkout fails the test.
+
+#[allow(dead_code)]
+#[path = "../../ogar-from-schema/src/ogit_checkout.rs"]
+mod ogit_checkout;
+
+use std::collections::BTreeSet;
+use std::sync::OnceLock;
+
+use dr_math_binding_probe::{
+    Axis, AxisKind, BoundDr64, Focus, FrameRevisions, FrameStore, Guards, MethodSignature, Operand,
+    Scope, bind_dr64,
+    relcomp::{Chain, RelExpr, Rows},
+};
+use ogar_action_handler::ogit::{Lane, OgitTables, Table};
+
+const W: usize = 64;
+const FOCUS: Focus = Focus { revision: 1 };
+const SCOPE: Scope = Scope { id: 1 };
+const VERB_AXIS: Axis = Axis {
+    class: 1,
+    kind: AxisKind::Capability,
+};
+const TYPE_AXIS: Axis = Axis {
+    class: 2,
+    kind: AxisKind::Identity,
+};
+
+fn tables() -> &'static OgitTables {
+    static TABLES: OnceLock<OgitTables> = OnceLock::new();
+    TABLES
+        .get_or_init(|| OgitTables::load(&ogit_checkout::root()).expect("the OGIT checkout loads"))
+}
+
+/// The allowed edges as `(src type, verb, dst type)` row ids.
+fn edges(t: &OgitTables) -> Vec<(usize, usize, usize)> {
+    let (s, v, d) = (
+        t.lane(Lane::AllowedSrc),
+        t.lane(Lane::AllowedVerb),
+        t.lane(Lane::AllowedDst),
+    );
+    (0..s.len())
+        .map(|i| (s[i] as usize, v[i] as usize, d[i] as usize))
+        .collect()
+}
+
+/// A Boolean relation stored as 64 × 64 blocks, row-block major.
+#[derive(Clone, PartialEq, Eq, Debug)]
+struct Blocked {
+    rows: usize,
+    cols: usize,
+    blocks: Vec<Rows>,
+}
+
+impl Blocked {
+    fn new(rows: usize, cols: usize) -> Self {
+        Self {
+            rows,
+            cols,
+            blocks: vec![[0u64; W]; rows.div_ceil(W) * cols.div_ceil(W)],
+        }
+    }
+    fn col_blocks(&self) -> usize {
+        self.cols.div_ceil(W)
+    }
+    fn set(&mut self, i: usize, j: usize) {
+        let b = (i / W) * self.col_blocks() + j / W;
+        self.blocks[b][i % W] |= 1u64 << (j % W);
+    }
+    fn get(&self, i: usize, j: usize) -> bool {
+        let b = (i / W) * self.col_blocks() + j / W;
+        (self.blocks[b][i % W] >> (j % W)) & 1 == 1
+    }
+    fn block(&self, bi: usize, bj: usize) -> &Rows {
+        &self.blocks[bi * self.col_blocks() + bj]
+    }
+    fn count(&self) -> usize {
+        self.blocks
+            .iter()
+            .flatten()
+            .map(|w| w.count_ones() as usize)
+            .sum()
+    }
+}
+
+/// A relation together with the axes its rows and columns live on.
+struct Rel<'a> {
+    m: &'a Blocked,
+    row: Axis,
+    col: Axis,
+}
+
+fn store() -> FrameStore {
+    FrameStore::new(FrameRevisions {
+        source: 1,
+        relation_map: 1,
+        coordinates: 1,
+    })
+}
+
+fn bind<'a>(st: &FrameStore, r: &Rel<'_>, ordinal: u16, rows: &'a Rows) -> BoundDr64<'a> {
+    let sig = MethodSignature::presence(7, ordinal, r.row, r.col);
+    let at = Guards {
+        frame: st.seal(),
+        focus: FOCUS,
+        scope: SCOPE,
+    };
+    bind_dr64(
+        st,
+        sig,
+        sig,
+        &at,
+        (FOCUS, SCOPE),
+        Operand {
+            rows,
+            validity: None,
+        },
+    )
+    .expect("a two-valued Distinct operand binds")
+}
+
+/// `a ∘ b`; every block product goes through `Chain::eval`.
+fn compose(st: &FrameStore, a: &Rel<'_>, b: &Rel<'_>) -> Blocked {
+    assert_eq!(a.m.cols, b.m.rows, "inner dimensions");
+    let mut out = Blocked::new(a.m.rows, b.m.cols);
+    let order = RelExpr::comp(RelExpr::Leaf(0), RelExpr::Leaf(1));
+    let n = out.col_blocks();
+    for bi in 0..a.m.rows.div_ceil(W) {
+        for bk in 0..b.m.cols.div_ceil(W) {
+            let mut acc = [0u64; W];
+            for bj in 0..a.m.cols.div_ceil(W) {
+                let chain = Chain::new(
+                    st,
+                    vec![
+                        bind(st, a, 0, a.m.block(bi, bj)),
+                        bind(st, b, 1, b.m.block(bj, bk)),
+                    ],
+                )
+                .expect("domains line up");
+                let (rows, _) = chain.eval(&order).expect("order covers the chain");
+                for (dst, src) in acc.iter_mut().zip(rows.iter()) {
+                    *dst |= src;
+                }
+            }
+            out.blocks[bi * n + bk] = acc;
+        }
+    }
+    out
+}
+
+/// `R_v`: type × type edges of one verb.
+fn verb_relation(t: &OgitTables, curie: &str) -> Blocked {
+    let v = usize::from(
+        t.verb_id(curie)
+            .unwrap_or_else(|| panic!("{curie} is a verb"))
+            .0,
+    );
+    let n = t.rows(Table::Type);
+    let mut r = Blocked::new(n, n);
+    for (s, verb, d) in edges(t) {
+        if verb == v {
+            r.set(s, d);
+        }
+    }
+    r
+}
+
+/// Naive composition of two type × type relations, sharing no code with the
+/// kernel.
+fn naive_compose(a: &Blocked, b: &Blocked) -> BTreeSet<(usize, usize)> {
+    let mut out = BTreeSet::new();
+    for i in 0..a.rows {
+        for j in 0..a.cols {
+            if !a.get(i, j) {
+                continue;
+            }
+            for k in 0..b.cols {
+                if b.get(j, k) {
+                    out.insert((i, k));
+                }
+            }
+        }
+    }
+    out
+}
+
+/// A pair set back as a square matrix.
+fn naive_matrix(p: &BTreeSet<(usize, usize)>, n: usize) -> Blocked {
+    let mut m = Blocked::new(n, n);
+    for &(i, j) in p {
+        m.set(i, j);
+    }
+    m
+}
+
+fn pairs(m: &Blocked) -> BTreeSet<(usize, usize)> {
+    let mut out = BTreeSet::new();
+    for i in 0..m.rows {
+        for j in 0..m.cols {
+            if m.get(i, j) {
+                out.insert((i, j));
+            }
+        }
+    }
+    out
+}
+
+#[test]
+fn chainable_verb_pairs_match_enumeration() {
+    let t = tables();
+    let (n_types, n_verbs) = (t.rows(Table::Type), t.rows(Table::Verb));
+    let e = edges(t);
+    assert!(
+        n_types > W && n_verbs > W,
+        "both axes need block composition"
+    );
+
+    let mut targets = Blocked::new(n_verbs, n_types);
+    let mut sources = Blocked::new(n_types, n_verbs);
+    for &(s, v, d) in &e {
+        targets.set(v, d);
+        sources.set(s, v);
+    }
+    let st = store();
+    let chainable = compose(
+        &st,
+        &Rel {
+            m: &targets,
+            row: VERB_AXIS,
+            col: TYPE_AXIS,
+        },
+        &Rel {
+            m: &sources,
+            row: TYPE_AXIS,
+            col: VERB_AXIS,
+        },
+    );
+
+    // Enumeration: for each type, every verb that may end there times every
+    // verb that may start there.
+    let mut into: Vec<BTreeSet<usize>> = vec![BTreeSet::new(); n_types];
+    let mut out_of: Vec<BTreeSet<usize>> = vec![BTreeSet::new(); n_types];
+    for &(s, v, d) in &e {
+        into[d].insert(v);
+        out_of[s].insert(v);
+    }
+    let mut expected = BTreeSet::new();
+    for ty in 0..n_types {
+        for &v in &into[ty] {
+            for &w in &out_of[ty] {
+                expected.insert((v, w));
+            }
+        }
+    }
+    assert_eq!(pairs(&chainable), expected);
+    assert!(!expected.is_empty());
+    let used: BTreeSet<usize> = e.iter().map(|&(_, v, _)| v).collect();
+    eprintln!(
+        "reader: {} files rejected, {} names declared twice, {} unresolved references",
+        t.rejected().len(),
+        t.duplicates().len(),
+        t.unresolved().len()
+    );
+    let mut by_table = std::collections::BTreeMap::new();
+    for u in t.unresolved() {
+        *by_table.entry(format!("{:?}", u.table)).or_insert(0usize) += 1;
+    }
+    eprintln!("unresolved by table: {by_table:?}");
+    let mut rejected_by_kind = std::collections::BTreeMap::new();
+    for r in t.rejected() {
+        let kind = ["/entities/", "/verbs/", "/attributes/"]
+            .into_iter()
+            .find(|k| r.contains(k))
+            .unwrap_or("other");
+        *rejected_by_kind.entry(kind).or_insert(0usize) += 1;
+    }
+    eprintln!("rejected files by kind: {rejected_by_kind:?}");
+    for u in t
+        .unresolved()
+        .iter()
+        .filter(|u| u.table == Table::Verb)
+        .take(5)
+    {
+        eprintln!("unresolved verb: {} in {}", u.name, u.from);
+    }
+    eprintln!(
+        "OGIT tables: {n_types} types, {n_verbs} verbs ({} used in allowed edges), {} allowed edges; \
+         {} chainable verb pairs of {} possible among used verbs",
+        used.len(),
+        e.len(),
+        chainable.count(),
+        used.len() * used.len()
+    );
+}
+
+#[test]
+fn typed_composition_of_named_verbs_matches_enumeration() {
+    let t = tables();
+    let st = store();
+    let rel = |m| Rel {
+        m,
+        row: TYPE_AXIS,
+        col: TYPE_AXIS,
+    };
+    let consists = verb_relation(t, "ogit:consistsOf");
+    let part_of = verb_relation(t, "ogit:isPartOf");
+    let contains = verb_relation(t, "ogit:contains");
+
+    for (name, a, b) in [
+        ("consistsOf ; isPartOf", &consists, &part_of),
+        ("isPartOf ; contains", &part_of, &contains),
+        ("contains ; contains", &contains, &contains),
+    ] {
+        let comp = compose(&st, &rel(a), &rel(b));
+        let expected = naive_compose(a, b);
+        assert_eq!(pairs(&comp), expected, "{name}");
+        eprintln!("{name}: {} type pairs", expected.len());
+    }
+
+    // Three verbs, both associations, through the kernel.
+    // consistsOf ; isPartOf ; consistsOf. (consistsOf ; isPartOf ; contains is
+    // empty on this schema, which would make the check vacuous.)
+    let consists_part = compose(&st, &rel(&consists), &rel(&part_of));
+    let part_consists = compose(&st, &rel(&part_of), &rel(&consists));
+    let left = compose(&st, &rel(&consists_part), &rel(&consists));
+    let right = compose(&st, &rel(&consists), &rel(&part_consists));
+    assert_eq!(
+        pairs(&left),
+        naive_compose(
+            &naive_matrix(&naive_compose(&consists, &part_of), consists.rows),
+            &consists
+        ),
+        "the three-verb chain matches enumeration"
+    );
+    assert_eq!(
+        left, right,
+        "composition is associative on the schema relations"
+    );
+    assert_ne!(left.count(), 0, "the three-verb chain is non-empty");
+}
+
+#[test]
+fn inverse_candidate_mirror_is_measured() {
+    let t = tables();
+    let consists = pairs(&verb_relation(t, "ogit:consistsOf"));
+    let part_of = pairs(&verb_relation(t, "ogit:isPartOf"));
+    let mirrored: BTreeSet<(usize, usize)> = consists.iter().map(|&(a, b)| (b, a)).collect();
+    let both = mirrored.intersection(&part_of).count();
+    assert!(both > 0, "the candidate has some schema support");
+    eprintln!(
+        "consistsOf: {} type pairs; isPartOf: {}; consistsOf mirrored into isPartOf: {both} \
+         ({} consistsOf pairs have no isPartOf mirror, {} isPartOf pairs have no consistsOf mirror)",
+        consists.len(),
+        part_of.len(),
+        mirrored.difference(&part_of).count(),
+        part_of.difference(&mirrored).count()
+    );
+}