diff --git a/scripts/check-all.sh b/scripts/check-all.sh
index 44322fc..409768f 100755
--- a/scripts/check-all.sh
+++ b/scripts/check-all.sh
@@ -6,11 +6,24 @@
 
 set -euo pipefail
 
+# Exit code 77 from a gate means "skipped: runner/infrastructure unavailable"
+# (see scripts/check-linux.sh). A skip is non-fatal and must not block the
+# push; a real failure (any other non-zero) still aborts the whole gate.
+SKIP=77
+
 run_gate() {
   name="$1"
   shift
   printf '\n==> %s\n' "$name"
+  set +e
   "$@"
+  status=$?
+  set -e
+  if [ "$status" -eq "$SKIP" ]; then
+    printf '    SKIPPED (runner unavailable; authoritative gate runs on CI)\n'
+    return 0
+  fi
+  return "$status"
 }
 
 run_gate "style" bash scripts/check-style.sh
diff --git a/scripts/check-linux.sh b/scripts/check-linux.sh
index 18836aa..ff1357b 100755
--- a/scripts/check-linux.sh
+++ b/scripts/check-linux.sh
@@ -1,7 +1,41 @@
 #!/usr/bin/env bash
 
+# The remote commands below are deliberately composed on the client: local
+# config ($REMOTE_DIR, $LIMA_INSTANCE, $REMOTE_BUILD) is expanded here and sent
+# to the host as a literal string. That client-side expansion is intended, so
+# the SC2029 notes it raises are silenced file-wide rather than per line.
+# shellcheck disable=SC2029
+
 set -euo pipefail
 
+# Exit-code contract (consumed by check-all.sh run_gate):
+#
+#   0  - Linux gate ran and PASSED. Either this machine is Linux (the gate runs
+#        natively), or the self-hosted relay was reachable and the relayed
+#        Swift build/test succeeded.
+#   77 - Linux gate SKIPPED because the self-hosted relay is unavailable from
+#        this machine: ssh/rsync missing locally, the host is unreachable, it
+#        lacks limactl, the working dir cannot be created, the sync fails, or
+#        the VM will not start. This is a runner-availability limitation, NOT a
+#        code defect. The authoritative Linux gate is the GitHub-hosted
+#        workflow (.github/workflows/linux.yml: ubuntu-latest + swift:6.2),
+#        which runs on every push regardless of this relay.
+#   1  - Linux gate RAN on the relay but the Swift build/test FAILED. A real
+#        Linux failure. It must be fixed, never skipped.
+#
+# The 77-vs-1 split is the whole point. An unreachable runner must not block a
+# green local push (skip), and it must never mask a real Linux failure (which
+# stays a hard 1). When in doubt during the build stage we fail hard, because
+# masking a real failure is the worse error.
+
+SKIP=77
+
+skip() {
+  echo "linux: SKIP ($1)." >&2
+  echo "linux: authoritative Linux gate is GitHub-hosted .github/workflows/linux.yml." >&2
+  exit "$SKIP"
+}
+
 run_linux_gate() {
   if [ -n "${SWIFTLY_HOME_DIR:-}" ] && [ -f "$SWIFTLY_HOME_DIR/env.sh" ]; then
     # shellcheck source=/dev/null
@@ -14,6 +48,7 @@ run_linux_gate() {
   swift test -c release
 }
 
+# Native Linux: this machine IS the runner. Hard gate, no relay, no skip path.
 if [ "$(uname -s)" = "Linux" ]; then
   run_linux_gate
   exit 0
@@ -25,21 +60,41 @@ REMOTE_PARENT="${PUREYAML_LINUX_REMOTE_PARENT:-/Volumes/ClawSSD/tmp}"
 REMOTE_DIR="$REMOTE_PARENT/pureyaml-linux-check"
 REMOTE_SWIFTLY_HOME="${PUREYAML_LINUX_SWIFTLY_HOME:-/Volumes/ClawSSD/swiftly-linux/home}"
 REMOTE_SWIFTLY_BIN="${PUREYAML_LINUX_SWIFTLY_BIN:-/Volumes/ClawSSD/swiftly-linux/bin}"
+SSH_CONNECT_TIMEOUT="${PUREYAML_LINUX_SSH_TIMEOUT:-10}"
 
-if ! command -v ssh >/dev/null 2>&1; then
-  echo "linux: ssh is required outside Linux" >&2
-  exit 2
+# --- Stage A: connectivity and provisioning (soft; any failure => skip) ------
+# Everything here is relay infrastructure. If it is not available, the local
+# Linux check cannot run, but that is not a code failure: skip with 77.
+
+command -v ssh >/dev/null 2>&1 || skip "ssh not available on this machine"
+command -v rsync >/dev/null 2>&1 || skip "rsync not available on this machine"
+
+if ! ssh -o BatchMode=yes -o ConnectTimeout="$SSH_CONNECT_TIMEOUT" "$HOST" true >/dev/null 2>&1; then
+  skip "host '$HOST' is unreachable over ssh"
 fi
 
-if ! command -v rsync >/dev/null 2>&1; then
-  echo "linux: rsync is required outside Linux" >&2
-  exit 2
+if ! ssh "$HOST" "command -v limactl >/dev/null && mkdir -p '$REMOTE_DIR'" >/dev/null 2>&1; then
+  skip "host '$HOST' lacks limactl or cannot create '$REMOTE_DIR'"
 fi
 
-ssh "$HOST" "command -v limactl >/dev/null && mkdir -p '$REMOTE_DIR'"
-rsync -a --delete \
-  --exclude '.build' \
-  --exclude '.git' \
-  ./ "$HOST:$REMOTE_DIR/"
+if ! rsync -a --delete --exclude '.build' --exclude '.git' ./ "$HOST:$REMOTE_DIR/" >/dev/null 2>&1; then
+  skip "rsync to '$HOST:$REMOTE_DIR' failed"
+fi
 
-ssh "$HOST" "limactl start '$LIMA_INSTANCE' >/tmp/pureyaml-lima-start.log 2>&1 || true; limactl shell '$LIMA_INSTANCE' -- bash -lc 'export SWIFTLY_HOME_DIR=\"$REMOTE_SWIFTLY_HOME\" SWIFTLY_BIN_DIR=\"$REMOTE_SWIFTLY_BIN\"; [ -f \"\$SWIFTLY_HOME_DIR/env.sh\" ] && . \"\$SWIFTLY_HOME_DIR/env.sh\"; cd \"$REMOTE_DIR\" && swift --version && swift build && swift test && swift build -c release && swift test -c release'"
+if ! ssh "$HOST" "limactl start '$LIMA_INSTANCE' >/tmp/pureyaml-lima-start.log 2>&1"; then
+  skip "lima instance '$LIMA_INSTANCE' would not start on '$HOST'"
+fi
+
+# --- Stage B: the real Linux build/test (hard; failure => exit 1) ------------
+# The relay is up and the tree is synced. From here a non-zero exit is a real
+# Linux build/test failure and must propagate. (A connection drop mid-build
+# also lands here; failing hard is the conservative, correct choice.)
+
+REMOTE_BUILD="export SWIFTLY_HOME_DIR=\"$REMOTE_SWIFTLY_HOME\" SWIFTLY_BIN_DIR=\"$REMOTE_SWIFTLY_BIN\"; [ -f \"\$SWIFTLY_HOME_DIR/env.sh\" ] && . \"\$SWIFTLY_HOME_DIR/env.sh\"; cd \"$REMOTE_DIR\" && swift --version && swift build && swift test && swift build -c release && swift test -c release"
+
+if ssh "$HOST" "limactl shell '$LIMA_INSTANCE' -- bash -lc '$REMOTE_BUILD'"; then
+  exit 0
+fi
+
+echo "linux: relayed Swift build/test FAILED on '$HOST'. Real failure, not skipped." >&2
+exit 1