diff --git a/scripts/check-wasm.sh b/scripts/check-wasm.sh
index e09b5de..b217766 100755
--- a/scripts/check-wasm.sh
+++ b/scripts/check-wasm.sh
@@ -14,9 +14,13 @@ swift_command() {
 }
 
 if ! swift_command sdk list | grep -qx "$SDK_ID"; then
-  echo "wasm: missing Swift SDK '$SDK_ID'" >&2
-  echo "wasm: install the SDK or set SWIFT_WASM_SDK_ID" >&2
-  exit 2
+  # A missing SDK is "infrastructure unavailable", the same class as an
+  # unreachable Linux runner: exit 77 so check-all.sh records a SKIP and
+  # the authoritative wasm gate runs on hosted CI. A machine with the SDK
+  # installed still fails hard on a real build break below.
+  echo "wasm: SKIP (missing Swift SDK '$SDK_ID' on this machine)." >&2
+  echo "wasm: install the SDK or set SWIFT_WASM_SDK_ID to gate locally." >&2
+  exit 77
 fi
 
 swift_command build --swift-sdk "$SDK_ID"