diff --git a/crates/effects/src/ocio/tests.rs b/crates/effects/src/ocio/tests.rs
index fe93dd25a..e17fd782a 100644
--- a/crates/effects/src/ocio/tests.rs
+++ b/crates/effects/src/ocio/tests.rs
@@ -396,3 +396,43 @@ fn color_stabilizer_samples_the_reference_at_the_points_reference_positions() {
         assert!((o(x) - (a + b * v(x))).abs() < 1e-3, "x {x}");
     }
 }
+
+/// Writes `text` to `dir/name` with modification time `secs` (so an edit within the file system's
+/// time resolution still moves the stamp), returning the path.
+fn write_dated(dir: &std::path::Path, name: &str, text: &str, secs: u64) -> String {
+    let path = dir.join(name);
+    std::fs::write(&path, text).unwrap();
+    let f = std::fs::File::options().write(true).open(&path).unwrap();
+    f.set_modified(std::time::UNIX_EPOCH + std::time::Duration::from_secs(secs)).unwrap();
+    path.to_string_lossy().into_owned()
+}
+
+/// #3538: OCIO File Transform read a file once per process; an edited, created, repaired or
+/// deleted file was never followed.
+#[test]
+fn an_ocio_transform_file_is_read_again_once_it_changes() {
+    const BLACK: &str = "LUT_1D_SIZE 2\n0 0 0\n0 0 0\n";
+    const WHITE: &str = "LUT_1D_SIZE 2\n1 1 1\n1 1 1\n";
+    let dir = std::env::temp_dir().join(format!("ec-fx-3538-file-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let at = |src: &str| load_file(src).map(|x| x.apply([0.5; 3], 1, false, ""));
+    let edited = write_dated(dir.as_path(), "edited.cube", BLACK, 1_000);
+    assert_eq!(at(&edited), Some([0.0; 3]));
+    write_dated(dir.as_path(), "edited.cube", WHITE, 2_000);
+    assert_eq!(at(&edited), Some([1.0; 3]), "an edited file, same size");
+    let created = dir.as_path().join("created.cube").to_string_lossy().into_owned();
+    assert_eq!(at(&created), None);
+    write_dated(dir.as_path(), "created.cube", WHITE, 1_000);
+    assert_eq!(at(&created), Some([1.0; 3]), "a file created after a failed load");
+    let repaired = write_dated(dir.as_path(), "repaired.cube", "not a lut", 1_000);
+    assert_eq!(at(&repaired), None);
+    write_dated(dir.as_path(), "repaired.cube", WHITE, 2_000);
+    assert_eq!(at(&repaired), Some([1.0; 3]), "a repaired file");
+    std::fs::remove_file(&repaired).unwrap();
+    assert_eq!(at(&repaired), None, "a deleted file");
+    // Inline text is its own content: the same text is the same transform.
+    let inline = load_file(BLACK).unwrap();
+    assert!(Arc::ptr_eq(&inline, &load_file(BLACK).unwrap()));
+    std::fs::remove_dir_all(&dir).unwrap();
+}
diff --git a/crates/effects/src/ocio_config/tests.rs b/crates/effects/src/ocio_config/tests.rs
index b616e6263..c36e467ea 100644
--- a/crates/effects/src/ocio_config/tests.rs
+++ b/crates/effects/src/ocio_config/tests.rs
@@ -410,3 +410,45 @@ fn builtin_styles() {
 fn rgb_white_xyz() -> [f64; 3] {
     [D65[0] / D65[1], 1.0, (1.0 - D65[0] - D65[1]) / D65[1]]
 }
+
+/// #3538: a custom `.ocio` config, and the LUTs it reads, were read once per process.
+#[test]
+fn an_ocio_config_and_its_luts_are_read_again_once_they_change() {
+    const BLACK: &str = "LUT_1D_SIZE 2\n0 0 0\n0 0 0\n";
+    const WHITE: &str = "LUT_1D_SIZE 2\n1 1 1\n1 1 1\n";
+    let dir = std::env::temp_dir().join(format!("ec-fx-3538-config-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    std::fs::create_dir_all(dir.as_path().join("luts")).unwrap();
+    let write = |name: &str, text: &str, secs: u64| {
+        let path = dir.as_path().join(name);
+        std::fs::write(&path, text).unwrap();
+        let f = std::fs::File::options().write(true).open(&path).unwrap();
+        f.set_modified(std::time::UNIX_EPOCH + std::time::Duration::from_secs(secs)).unwrap();
+        path.to_string_lossy().into_owned()
+    };
+    let config = |space: &str| {
+        format!(
+            "ocio_profile_version: 2\nsearch_path: luts\nroles:\n  scene_linear: lin\ncolorspaces:\n  - !<ColorSpace>\n    name: lin\n  - !<ColorSpace>\n    name: {space}\n    to_reference: !<FileTransform> {{src: grade.cube, interpolation: linear}}\n  - !<ColorSpace>\n    name: later\n    to_reference: !<FileTransform> {{src: later.cube, interpolation: linear}}\n"
+        )
+    };
+    let src = dir.as_path().join("config.ocio").to_string_lossy().into_owned();
+    assert!(load_config(&src).is_err(), "no config yet");
+    write("config.ocio", &config("graded"), 1_000);
+    write("luts/grade.cube", BLACK, 1_000);
+    let to_lin = |space: &str| {
+        let c = load_config(&src).unwrap();
+        c.convert(c.space(space).unwrap(), c.space("lin").unwrap(), [0.5; 3])
+    };
+    assert_eq!(to_lin("graded"), [0.0; 3], "a config created after a failed load");
+    write("luts/grade.cube", WHITE, 2_000);
+    assert_eq!(to_lin("graded"), [1.0; 3], "a LUT the config reads, edited");
+    assert_eq!(to_lin("later"), [0.5; 3], "a LUT not there yet passes through");
+    write("luts/later.cube", BLACK, 1_000);
+    assert_eq!(to_lin("later"), [0.0; 3], "a LUT the config reads, created");
+    write("config.ocio", &config("regraded"), 2_000);
+    assert!(load_config(&src).unwrap().space("regraded").is_some(), "an edited config");
+    std::fs::remove_file(&src).unwrap();
+    assert!(load_config(&src).is_err(), "a deleted config");
+    std::fs::remove_dir_all(&dir).unwrap();
+}