diff --git a/examples/1036-errors-failable-smoke.sx b/examples/1036-errors-failable-smoke.sx
index 2a90f32..76c354e 100644
--- a/examples/1036-errors-failable-smoke.sx
+++ b/examples/1036-errors-failable-smoke.sx
@@ -51,6 +51,24 @@ sm_first :: (a: s32, b: s32) -> (s32, !) {
     return v;
 }
 
+// --- Composition (ERR E5.1): failable closures, widening, generics ---
+
+// Closure(...) param, try-propagated (the env is carried)
+sm_run :: (cb: Closure(s32) -> (s32, !SmokeErr), n: s32) -> (s32, !SmokeErr) {
+    return try cb(n);
+}
+
+// bare fn-type param: a NON-failable closure literal widens into the failable
+// slot (the ∅-widening adapter wraps `{value, 0}`)
+sm_widen :: (cb: (s32) -> (s32, !SmokeErr), n: s32) -> s32 {
+    return cb(n) catch e -1;
+}
+
+// generic ($T) value-carrying failable composition, monomorphized per call
+sm_wrap :: ($T: Type, f: Closure() -> (T, !SmokeErr)) -> (T, !SmokeErr) {
+    return try f();
+}
+
 main :: () {
     // error.X as a typed value + {} interpolation renders the tag name
     e0 : SmokeErr = error.BadDigit;
@@ -100,5 +118,17 @@ main :: () {
     hv, herr := sm_acquire(true);
     print("acquire ok:\n");
     iv, ierr := sm_acquire(false);
+
+    // composition: inline failable closure literal through a Closure(...) param
+    cl := sm_run(closure((x: s32) -> (s32, !SmokeErr) { if x < 0 { raise error.BadDigit; } return x * 2; }), 6) catch e -1;
+    print("closure-run: {}\n", cl);                                                     // 12
+    print("closure-run-err: {}\n", sm_run(closure((x: s32) -> (s32, !SmokeErr) { raise error.Empty; }), 1) catch e -9); // -9
+
+    // non-failable closure literal widened into the failable bare slot
+    print("widen: {}\n", sm_widen(closure((x: s32) -> s32 => x + 1), 9));               // 10
+
+    // generic failable composition (monomorphized at s32)
+    print("wrap: {}\n", sm_wrap(s32, closure(() -> (s32, !SmokeErr) { return 42; })) catch e 0); // 42
+
     print("errors ok\n");
 }
diff --git a/examples/expected/1036-errors-failable-smoke.stdout b/examples/expected/1036-errors-failable-smoke.stdout
index 26b45c5..b185783 100644
--- a/examples/expected/1036-errors-failable-smoke.stdout
+++ b/examples/expected/1036-errors-failable-smoke.stdout
@@ -16,4 +16,8 @@ acquire fail:
   defer A
 acquire ok:
   defer A
+closure-run: 12
+closure-run-err: -9
+widen: 10
+wrap: 42
 errors ok