diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a55087d4..d6435891 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -220,10 +220,16 @@ jobs:
       - name: cargo test
         run: cargo test --workspace --locked
       - name: exhaustive 24-bit family membership oracle
-        run: >-
-          cargo test -p labcolors-core
-          family_tests::axis_membership_matches_the_full_srgb8_cube_oracle
-          --locked -- --ignored --exact
+        shell: bash
+        run: |
+          set -euo pipefail
+          test_name='family_artifact_tests::axis_membership_matches_the_full_srgb8_cube_oracle'
+          cargo test -p labcolors-core --lib --locked -- --ignored --list --format terse |
+            awk -v expected="${test_name}: test" '
+              $0 == expected { matches += 1 }
+              END { exit(matches == 1 ? 0 : 1) }
+            '
+          cargo test -p labcolors-core --lib "${test_name}" --locked -- --ignored --exact
       - name: prove core capability projection boundary
         shell: bash
         run: |
diff --git a/crates/labcolors-core/src/family_artifact_tests.rs b/crates/labcolors-core/src/family_artifact_tests.rs
index c33986cc..7e16b079 100644
--- a/crates/labcolors-core/src/family_artifact_tests.rs
+++ b/crates/labcolors-core/src/family_artifact_tests.rs
@@ -372,6 +372,37 @@ fn full_srgb8_set_cardinality_reaches_codec_admission() {
     );
 }
 
+#[test]
+#[ignore = "full 24-bit domain oracle runs once in CI outside mutation tests"]
+fn axis_membership_matches_the_full_srgb8_cube_oracle() {
+    let members = (0_u16..=255)
+        .map(|value| {
+            let value = value as u8;
+            ColorSignal::from_srgb8(Srgb8::new([value; 3]))
+        })
+        .collect::<Vec<_>>();
+    let (certificate, encoded) = encode_fixture_family_artifact_v2(
+        definition(),
+        &members,
+        FixtureFamilyArtifactCodecV1::CanonicalMembersV1,
+    )
+    .unwrap();
+    let admitted = load_fixture(certificate, encoded).unwrap();
+
+    for red in 0_u16..=255 {
+        for green in 0_u16..=255 {
+            for blue in 0_u16..=255 {
+                let bytes = [red as u8, green as u8, blue as u8];
+                assert_eq!(
+                    admitted.contains(ColorSignal::from_srgb8(Srgb8::new(bytes))),
+                    bytes[0] == bytes[1] && bytes[1] == bytes[2],
+                    "full-domain disagreement at {bytes:?}",
+                );
+            }
+        }
+    }
+}
+
 #[test]
 fn central_loader_rejects_a_decoder_that_lies_about_member_count() {
     let members = signals(&[[0, 0, 1], [0, 0, 2]]);