diff --git a/.gitea/workflows/lint-shellcheck-arm64-pilot.yml b/.gitea/workflows/lint-shellcheck-arm64-pilot.yml
index 6e7f8a7a2..2b157a346 100644
--- a/.gitea/workflows/lint-shellcheck-arm64-pilot.yml
+++ b/.gitea/workflows/lint-shellcheck-arm64-pilot.yml
@@ -3,11 +3,26 @@ name: Lint shellcheck (arm64 pilot)
 # Mac-CI dual-track pilot (#233). ADDITIVE / NOT REQUIRED.
 #
 # Validates the arm64 self-hosted lane (no docker.sock, no privileged
-# ops) before any required gate moves onto it. Until a Mac arm64 runner
-# is registered with the `arm64` label, this workflow sits PENDING —
-# that is FINE: `arm64` is NOT in branch_protections required contexts.
+# ops) before any required gate moves onto it.
 #
-# Pairs with internal#543 (RFC: Mac arm64 multi-arch runner-base).
+# Runner label mapping (2026-05-22 fix): the actual Mac mini runner
+# registered in this Gitea ships labels
+#   ["self-hosted","macos-self-hosted-arm64","arm64-darwin"]
+# — no plain `arm64`. The earlier `runs-on: [self-hosted, arm64]`
+# could not match any registered runner so every fire of this workflow
+# was assigned task_id=0 / runner_id=NULL → Gitea cancelled it. The
+# rows showed up as Cancelled in the action status feed (not Failed)
+# but the lane never actually ran. Workflow now selects on
+# `arm64-darwin` which is the canonical Mac-arm64 label per the
+# Mac mini's registration (per internal#494 capability-honest labels).
+#
+# If we later want to add a Linux-arm64 runner to the same lane, add
+# both labels to that runner's registration AND broaden the selector
+# here — don't rename `arm64-darwin` (it's Mac-specific by design and
+# `feedback_pc2_runner_labels_must_stay_narrow` rule applies).
+#
+# Pairs with internal#543 (RFC: Mac arm64 multi-arch runner-base) and
+# internal#494 (multi-arch runner-base capability-honest labels).
 # No paths: filter on purpose (feedback_path_filtered_workflow_cant_be_required).
 
 on:
@@ -82,7 +97,15 @@ jobs:
             echo "WARN: shellcheck binary not found — skipping (pilot mode)"
             exit 0
           fi
-          mapfile -t TARGETS < <(find .gitea/scripts -maxdepth 2 -type f -name '*.sh' | sort)
+          # NOTE: macOS ships Bash 3.2 (Apple license), no `mapfile`
+          # (Bash 4+ builtin). Mac mini runner empirically failed at
+          # `mapfile: command not found` (run 79275 / task 145654).
+          # Use the portable `while read` pattern instead — works on
+          # both Bash 3.2 (macOS) and Bash 4+ (Linux).
+          TARGETS=()
+          while IFS= read -r f; do
+            TARGETS+=("$f")
+          done < <(find .gitea/scripts -maxdepth 2 -type f -name '*.sh' | sort)
           if [ "${#TARGETS[@]}" -eq 0 ]; then
             echo "No .sh files found under .gitea/scripts — nothing to check"
             exit 0