diff --git a/.github/workflows/cd.yaml b/.github/workflows/cd.yaml
index bfc0c5b70..a6f38505f 100644
--- a/.github/workflows/cd.yaml
+++ b/.github/workflows/cd.yaml
@@ -162,9 +162,18 @@ jobs:
           kubectl version --client
 
       - name: 🔐 Validate static production authorization controls
+        # Both commands run unconditionally, and the step fails if either did.
+        # They are independent outputs over the same surface: `go test` is the
+        # verdict, `go run` is the only caller of the moved-entry diagnostics. A
+        # real aggregate mismatch fails BOTH, so short-circuiting on the first
+        # left the one failure that most needs explaining with no entry names at
+        # all (#3879). Covered by scripts/tests/test-authorization-gate-diagnostics.sh.
         run: |
-          go test ./scripts/validate-eks-ci-role-policy
-          go run ./scripts/validate-eks-ci-role-policy .
+          set -euo pipefail
+          status=0
+          go test ./scripts/validate-eks-ci-role-policy || status=1
+          go run ./scripts/validate-eks-ci-role-policy . || status=1
+          exit "$status"
 
       - name: ⚙️ Setup KSail for effective authorization validation
         shell: bash
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index f5e583072..b0fb6a8f9 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -230,6 +230,19 @@ jobs:
           shellcheck scripts/tests/test-regenerate-publish-workflow-approved-revisions.sh
           bash scripts/tests/test-regenerate-publish-workflow-approved-revisions.sh
 
+      # The authorization gate's verdict and its moved-entry diagnostics are two
+      # commands in one step, and a real aggregate mismatch fails BOTH — so a step
+      # that stopped at the first never ran the diagnostics on the one failure they
+      # exist to explain (#3879). That is a property of the STEP's shape, which no
+      # script it calls can enforce, so the test executes the step against stub
+      # binaries and ablates each assertion. Unconditional for the same reason as
+      # the steps above: its subjects are ci.yaml and cd.yaml themselves, which sit
+      # outside the k8s paths.
+      - name: 🔐 Validate the authorization gate reports its diagnostics
+        run: |
+          shellcheck scripts/tests/test-authorization-gate-diagnostics.sh
+          bash scripts/tests/test-authorization-gate-diagnostics.sh
+
       # Both subject guards above examine a file only when it already carries a
       # shared-publish-workflow subject, so an OCIRepository pointed at a devantler-tech
       # artifact with NO spec.verify at all is invisible to them — and refused by nothing
@@ -906,16 +919,24 @@ jobs:
         # The HEAD^1 checkout is diagnostic only: on an unapproved aggregate the
         # validator names the surface entries that differ from it. Without it the
         # verdict is identical and the moved entries are reported as unknown.
+        # Both commands run unconditionally, and the step fails if either did.
+        # They are independent outputs over the same surface: `go test` is the
+        # verdict, `go run` is the only caller of the moved-entry diagnostics. A
+        # real aggregate mismatch fails BOTH, so short-circuiting on the first
+        # left the one failure that most needs explaining with no entry names at
+        # all (#3879). Covered by scripts/tests/test-authorization-gate-diagnostics.sh.
         run: |
           set -euo pipefail
-          go test ./scripts/validate-eks-ci-role-policy
+          status=0
+          go test ./scripts/validate-eks-ci-role-policy || status=1
           base_root="$RUNNER_TEMP/approval-base-tree"
           if git worktree add --detach "$base_root" HEAD^1; then
-            go run ./scripts/validate-eks-ci-role-policy . "$base_root"
+            go run ./scripts/validate-eks-ci-role-policy . "$base_root" || status=1
           else
             echo "::warning::approval base checkout failed; an aggregate mismatch will not name moved entries"
-            go run ./scripts/validate-eks-ci-role-policy .
+            go run ./scripts/validate-eks-ci-role-policy . || status=1
           fi
+          exit "$status"
 
       - name: ⚙️ Setup KSail for effective authorization validation
         shell: bash
diff --git a/scripts/tests/test-authorization-gate-diagnostics.sh b/scripts/tests/test-authorization-gate-diagnostics.sh
new file mode 100755
index 000000000..8d6584f38
--- /dev/null
+++ b/scripts/tests/test-authorization-gate-diagnostics.sh
@@ -0,0 +1,231 @@
+#!/usr/bin/env bash
+# Prove the authorization gate reports BOTH of its outputs on a real mismatch
+# (devantler-tech/platform#3879).
+#
+# WHY THIS EXISTS. The "🔐 Validate static production authorization controls"
+# step runs two independent commands over the same surface:
+#
+#   * `go test ./scripts/validate-eks-ci-role-policy` — the verdict. On an
+#     unapproved aggregate TestValidateAuthorizationAcceptsCommittedPolicy
+#     t.Fatalf's with the bare fingerprint.
+#   * `go run ./scripts/validate-eks-ci-role-policy . "$base_root"` — the
+#     diagnostics. This is the ONLY caller of surfaceMismatchReport, the code
+#     #3836 added to name the surface entries that moved.
+#
+# A real aggregate mismatch fails BOTH. So a step that short-circuits on the
+# first command never reaches the second, and the failure that most needs an
+# explanation is the one reported with no entry names at all — measured on
+# #3878 (CI run 35257229458, job 105324573289): the approval base checked out
+# fine, `go test` failed with `a4781e58…`, and zero moved-entry lines were
+# emitted.
+#
+# The step's script is EXECUTED here against stub `go` and `git` binaries rather
+# than pattern-matched, so the assertions are about behaviour: which commands
+# ran, and what the step exited with. Every assertion is ABLATED against the
+# short-circuiting form the fix replaces; a check that cannot fail is not a
+# check.
+#
+# yq (mikefarah v4) reads the YAML. No network, no secrets, no Go toolchain.
+# Bash 3.2 compatible.
+set -euo pipefail
+
+root_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+readonly root_dir
+readonly job='validate-eks-authorization'
+readonly step='🔐 Validate static production authorization controls'
+readonly diagnostic_line='changed helm.toolkit.fluxcd.io/v2|HelmRelease|kube-system|hcloud-csi'
+
+work_dir="$(mktemp -d)"
+readonly work_dir
+trap 'rm -rf "${work_dir}"' EXIT
+
+failures=0
+
+fail() {
+  printf 'FAIL: %s\n' "$1" >&2
+  failures=$((failures + 1))
+}
+
+# extract_step prints the step's `run:` script for one workflow.
+extract_step() {
+  local workflow="$1"
+  yq -r \
+    ".jobs[\"${job}\"].steps[] | select(.name == \"${step}\") | .run" \
+    "${workflow}"
+}
+
+# step_shell_flags prints the flags the runner gives the step's interpreter, so
+# the script is exercised the way GitHub actually runs it rather than under a
+# bare `bash`. A step with no `shell:` key gets `bash -e {0}`; an explicit
+# `shell: bash` gets `bash --noprofile --norc -eo pipefail {0}`. The difference
+# decides whether a failing first command aborts the step, which is the very
+# property under test — running these under a plain `bash` reports a swallowed
+# failure that the runner would never produce.
+step_shell_flags() {
+  local workflow="$1" declared
+  declared="$(yq -r \
+    ".jobs[\"${job}\"].steps[] | select(.name == \"${step}\") | .shell // \"\"" \
+    "${workflow}")"
+  case "${declared}" in
+    bash) printf -- '-e -o pipefail' ;;
+    '') printf -- '-e' ;;
+    *) printf -- '-e' ;;
+  esac
+}
+
+# make_stubs builds a PATH directory whose `go` records each invocation and
+# exits with the caller's chosen status, and whose `git` always succeeds so the
+# approval-base branch is taken.
+#
+#   $1 work root   $2 `go test` exit status   $3 `go run` exit status
+make_stubs() {
+  local dir="$1" test_status="$2" run_status="$3"
+  mkdir -p "${dir}/bin"
+  cat >"${dir}/bin/go" <<EOF
+#!/usr/bin/env bash
+printf '%s\n' "\$1" >>"${dir}/invocations"
+case "\$1" in
+  test) printf 'FAIL\tgithub.com/devantler-tech/platform/scripts/validate-eks-ci-role-policy\n'; exit ${test_status} ;;
+  run)  printf 'EKS CI role policy: ${diagnostic_line}\n'; exit ${run_status} ;;
+esac
+exit 0
+EOF
+  cat >"${dir}/bin/git" <<'EOF'
+#!/usr/bin/env bash
+exit 0
+EOF
+  chmod +x "${dir}/bin/go" "${dir}/bin/git"
+  : >"${dir}/invocations"
+}
+
+# run_step executes a step script under the stubs and prints
+# "<exit status>|<space-separated go subcommands>|<stdout+stderr on one line>".
+#
+#   $1 script path   $2 `go test` exit status   $3 `go run` exit status
+#   $4 the runner's shell flags for that step
+run_step() {
+  local script="$1" test_status="$2" run_status="$3" shell_flags="$4"
+  local sandbox status output
+  sandbox="$(mktemp -d "${work_dir}/sandbox.XXXXXX")"
+  make_stubs "${sandbox}" "${test_status}" "${run_status}"
+  set +e
+  # shellcheck disable=SC2086 # shell_flags is a controlled flag list, not a path.
+  output="$(PATH="${sandbox}/bin:${PATH}" RUNNER_TEMP="${sandbox}" \
+    bash ${shell_flags} "${script}" 2>&1)"
+  status=$?
+  set -e
+  printf '%s|%s|%s\n' \
+    "${status}" \
+    "$(tr '\n' ' ' <"${sandbox}/invocations" | sed 's/ *$//')" \
+    "$(printf '%s' "${output}" | tr '\n' ' ')"
+}
+
+# field reads one of run_step's three fields. The captured output is LAST and is
+# read with an open-ended range, because a surface entry is itself pipe-separated
+# (`apiVersion|Kind|namespace|name`) — a fixed `-f3` truncates the diagnostics at
+# their first separator and reports a line that was printed as missing.
+field() {
+  case "$2" in
+    3) printf '%s' "$1" | cut -d'|' -f3- ;;
+    *) printf '%s' "$1" | cut -d'|' -f"$2" ;;
+  esac
+}
+
+# assert_gate_behaviour runs the four cases every copy of the step must satisfy.
+#
+#   $1 label   $2 script path   $3 shell flags
+#   $4 "diagnostics" to require the moved-entry line
+assert_gate_behaviour() {
+  local label="$1" script="$2" shell_flags="$3" mode="${4:-}"
+  local result
+
+  # Case A — a real aggregate mismatch: both commands fail. The step must run
+  # the diagnostics anyway, and must still fail.
+  result="$(run_step "${script}" 1 1 "${shell_flags}")"
+  case " $(field "${result}" 2) " in
+    *' run '*) : ;;
+    *) fail "${label}: a failing 'go test' short-circuited the step before 'go run' — the moved-entry diagnostics never execute on the one failure they exist to explain (got invocations: '$(field "${result}" 2)')" ;;
+  esac
+  [ "$(field "${result}" 1)" != "0" ] ||
+    fail "${label}: the step exited 0 while both commands failed"
+  if [ "${mode}" = "diagnostics" ]; then
+    case "$(field "${result}" 3)" in
+      *"${diagnostic_line}"*) : ;;
+      *) fail "${label}: the moved-entry diagnostics were not reported (got: '$(field "${result}" 3)')" ;;
+    esac
+  fi
+
+  # Case B — negative control: `go test` fails for a reason unrelated to the
+  # aggregate, so `go run` passes. Running both must not swallow the failure.
+  result="$(run_step "${script}" 1 0 "${shell_flags}")"
+  [ "$(field "${result}" 1)" != "0" ] ||
+    fail "${label}: a failing 'go test' was swallowed when 'go run' passed — the step reports success on a broken validator"
+
+  # Case C — the mirror of B, and the half of "the step fails if either did" that
+  # nothing else here covers: the verdict passes and only the diagnostics fail.
+  # Cases A, B and D are all satisfied by a step that ignores `go run` entirely,
+  # so dropping `|| status=1` from either `go run` line would otherwise land
+  # silently — and the diagnostics this gate exists for would stop being checked.
+  result="$(run_step "${script}" 0 1 "${shell_flags}")"
+  [ "$(field "${result}" 1)" != "0" ] ||
+    fail "${label}: a failing 'go run' was swallowed when 'go test' passed — the step reports success although the moved-entry diagnostics did not run"
+
+  # Case D — control: both pass, so the step passes.
+  result="$(run_step "${script}" 0 0 "${shell_flags}")"
+  [ "$(field "${result}" 1)" = "0" ] ||
+    fail "${label}: the step failed while both commands passed (exit $(field "${result}" 1): '$(field "${result}" 3)')"
+}
+
+for workflow_name in ci cd; do
+  workflow="${root_dir}/.github/workflows/${workflow_name}.yaml"
+  [ -f "${workflow}" ] || { fail "${workflow_name}.yaml is missing"; continue; }
+
+  script="${work_dir}/${workflow_name}-step.sh"
+  extract_step "${workflow}" >"${script}"
+  shell_flags="$(step_shell_flags "${workflow}")"
+  if [ ! -s "${script}" ] || grep -qx 'null' "${script}"; then
+    fail "${workflow_name}.yaml: job '${job}' has no step named '${step}' — the gate this test pins was renamed or removed"
+    continue
+  fi
+  grep -q 'validate-eks-ci-role-policy' "${script}" ||
+    fail "${workflow_name}.yaml: the extracted step does not invoke the authorization validator"
+
+  # ci.yaml checks out the approval base, so its diagnostics name the entries.
+  if grep -q 'approval-base-tree' "${script}"; then
+    assert_gate_behaviour "${workflow_name}.yaml" "${script}" "${shell_flags}" diagnostics
+  else
+    assert_gate_behaviour "${workflow_name}.yaml" "${script}" "${shell_flags}"
+  fi
+done
+
+# ABLATION. The short-circuiting form this fix replaces must fail Case A, and
+# must fail naming the short-circuit rather than something incidental. A test
+# that passes against the defect proves nothing.
+ablation="${work_dir}/ablation-step.sh"
+cat >"${ablation}" <<'EOF'
+set -euo pipefail
+go test ./scripts/validate-eks-ci-role-policy
+base_root="$RUNNER_TEMP/approval-base-tree"
+if git worktree add --detach "$base_root" HEAD^1; then
+  go run ./scripts/validate-eks-ci-role-policy . "$base_root"
+else
+  go run ./scripts/validate-eks-ci-role-policy .
+fi
+EOF
+ablation_result="$(run_step "${ablation}" 1 1 '-e')"
+case " $(field "${ablation_result}" 2) " in
+  *' run '*)
+    fail "ABLATION: the short-circuiting step reached 'go run', so Case A cannot detect the defect it is written for"
+    ;;
+  *) : ;;
+esac
+[ "$(field "${ablation_result}" 1)" != "0" ] ||
+  fail "ABLATION: the short-circuiting step exited 0, so Case B's control is not exercised"
+
+if [ "${failures}" -ne 0 ]; then
+  printf '%s: %d assertion(s) failed\n' "$(basename "$0")" "${failures}" >&2
+  exit 1
+fi
+
+printf '%s: authorization gate reports its verdict AND its diagnostics in ci.yaml and cd.yaml\n' \
+  "$(basename "$0")"