conformance/incluster/Containerfile

@@ -0,0 +1,168 @@
+# =============================================================================
+# conformance-runner — the image the in-cluster L2/L3 Chainsaw Job actually runs.
+# Closes docs/plans/l2-l3-conformance-ci-wiring.md §3 item 1.
+#
+# WHY THIS EXISTS. chainsaw-job.yaml pins `ghcr.io/kyverno/chainsaw:v0.2.12` and
+# `command: ["./run.sh"]`. That image carries the chainsaw binary and almost nothing else —
+# no bash, no python3, no kubectl, no git. So the committed Job could never have run: it
+# would have failed at exec of `./run.sh`. This image carries exactly what
+# `conformance/run.sh` needs:
+#
+#   bash      run.sh and every tests/**/check.sh are bash (arrays, mapfile, BASH_SOURCE)
+#   python3   lib/{run_l1_offline,gen_coverage,merge_junit,emit_skipped_junit,status}.py
+#             (stdlib only — conformance/versions.env PYTHON_MIN=3.9, so no pip layer)
+#   chainsaw  the L1/L2/L3 runner itself (run_chainsaw / lint_tests)
+#   kubectl   conf_cluster_reachable()'s `kubectl cluster-info` preflight + probe scripts
+#   git       the init-container's `clone --depth 1` + `checkout <SHA>` (§3 item 2) and
+#             run.sh's `rev-parse --short HEAD` for the run id
+#   tar/gzip/coreutils  the `=== ARTIFACTS-TGZ-BASE64 ===` results channel (§3 item 3)
+#
+# VERSIONS COME FROM infra/devcontainer/versions.env — NOT from new pins invented here.
+# That file is the single source of truth for CHAINSAW_VERSION / KUBECTL_VERSION /
+# FEDORA_VERSION, and build-image.sh sources it and passes them in as --build-arg. The
+# ARG defaults below are deliberately EMPTY so a build that forgets to pass them fails
+# loudly (see the assertion in the first RUN) instead of silently baking a stale version.
+#
+# KNOWN LIMIT — READ BEFORE CHOOSING THE JOB'S `args`.
+# `run.sh` runs the selected OFFLINE L0/L1 checks (run_offline_checks) before it ever
+# touches the cluster, for ANY selection that is not offline-only. Those checks shell out
+# to flux / promtool / kyverno / kustomize, which this image deliberately does NOT carry —
+# baking the whole devcontainer toolchain into the runner would roughly double its size to
+# re-run work that ci/l0.sh + ci/l1.sh already did offline in the same CI run. So the Job
+# must select the cluster-gated layers only, e.g. `args: ["--layer", "l2"]` /
+# `["--layer", "l3"]`, where offline_selected_dirs() resolves to nothing and
+# run_offline_checks() returns 0. `--layer all` and a bare `--requirements <IDs>` would drag
+# the L0 checks in and fail on a missing tool. Flagged to the plan owner; choosing the Job's
+# args is T-6.1b's call, not this image's.
+#
+# THE ADMISSION CONTRACT THIS IMAGE MUST SATISFY.
+# platform/kyverno/admission/conformance-trigger-job-shape.yaml is a fail-closed Enforce
+# ClusterPolicy (R-SEC-02) and it is the security boundary. It requires the Job's container
+# to be `gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:*` — a DIGEST,
+# never a tag — with `runAsNonRoot: true` and `allowPrivilegeEscalation: false`. Two
+# consequences are baked in here:
+#
+#   1. `USER` is NUMERIC. With `runAsNonRoot: true` and no explicit `runAsUser`, the kubelet
+#      REJECTS an image whose USER is a name it cannot resolve to a uid
+#      ("container has runAsNonRoot and image has non-numeric user"). So: USER 65532:65532.
+#   2. The pod is `readOnlyRootFilesystem: true` and the policy admits only the `workspace`
+#      and `results` volumes — there is no writable /tmp and one cannot be added without
+#      changing the boundary. So HOME and every cache path point INTO /workspace (the
+#      emptyDir), not at the read-only root. That is why HOME=/workspace below.
+# =============================================================================
+
+# --- builder: fetch the pinned release binaries ------------------------------
+# A full Fedora for the download stage (it has curl + tar); none of it ships in the runtime
+# image, so the runner does not carry a downloader it has no business having at runtime.
+ARG FEDORA_VERSION=44
+FROM registry.fedoraproject.org/fedora:${FEDORA_VERSION} AS builder
+
+ARG CHAINSAW_VERSION=
+ARG KUBECTL_VERSION=
+ARG TARGETARCH=amd64
+
+# Fail the BUILD — not the Job, three weeks later — if a pin was not passed in.
+RUN set -eux; \
+    : "${CHAINSAW_VERSION:?pass --build-arg CHAINSAW_VERSION from infra/devcontainer/versions.env}"; \
+    : "${KUBECTL_VERSION:?pass --build-arg KUBECTL_VERSION from infra/devcontainer/versions.env}"
+
+# Same URLs and the same arch handling as infra/devcontainer/Containerfile, so the chainsaw
+# and kubectl in this image are the same builds the toolbox gate runs with. kubectl's
+# published sha256 is verified; chainsaw publishes no per-asset checksum file at a stable
+# URL, so its integrity rests on the tag + TLS (and, after the operator pushes, on this
+# image's own digest).
+RUN set -eux; \
+    mkdir -p /out; \
+    curl -fsSL "https://dl.k8s.io/release/v${KUBECTL_VERSION}/bin/linux/${TARGETARCH}/kubectl" \
+      -o /out/kubectl; \
+    curl -fsSL "https://dl.k8s.io/release/v${KUBECTL_VERSION}/bin/linux/${TARGETARCH}/kubectl.sha256" \
+      -o /tmp/kubectl.sha256; \
+    echo "$(cat /tmp/kubectl.sha256)  /out/kubectl" | sha256sum -c -; \
+    curl -fsSL "https://github.com/kyverno/chainsaw/releases/download/v${CHAINSAW_VERSION}/chainsaw_linux_${TARGETARCH}.tar.gz" \
+      | tar -xz -C /out chainsaw; \
+    chmod 0755 /out/kubectl /out/chainsaw; \
+    /out/kubectl version --client=true --output=yaml >/dev/null; \
+    /out/chainsaw version >/dev/null
+
+# --- runtime -----------------------------------------------------------------
+ARG FEDORA_VERSION=44
+FROM registry.fedoraproject.org/fedora-minimal:${FEDORA_VERSION}
+
+ARG CHAINSAW_VERSION=
+ARG KUBECTL_VERSION=
+ARG FEDORA_VERSION=44
+# Nonroot uid/gid. 65532 is the distroless `nonroot` convention; the value is arbitrary but
+# it MUST be numeric and non-zero — see "THE ADMISSION CONTRACT" above.
+ARG RUNNER_UID=65532
+ARG RUNNER_GID=65532
+
+LABEL org.opencontainers.image.title="conformance-runner" \
+      org.opencontainers.image.description="bash + python3 + chainsaw + kubectl + git for the in-cluster L2/L3 conformance Job (conformance/run.sh)" \
+      org.opencontainers.image.source="https://gitea.home.keithjackson.dev/Home-Network/home-network-k3s-impl" \
+      org.opencontainers.image.documentation="conformance/incluster/README.md" \
+      homelab.keithjackson.dev/requirements="R-TEST-02,R-SEC-02"
+
+# bash: run.sh + every check.sh.  python3: the stdlib report generators.
+# git-core: the init-container clone (git-core, not git — drops the perl/svn tail).
+# coreutils/findutils/grep/sed/gawk: find, sort, base64, xargs, sed -nE, awk in lib/*.sh.
+# tar+gzip: the base64-tar results channel.  diffutils: `diff` in the L1 golden compare.
+# ca-certificates: TLS for the init clone and for kubectl's in-cluster API calls.
+RUN set -eux; \
+    microdnf -y install --setopt=install_weak_deps=0 --nodocs \
+      bash python3 git-core coreutils findutils grep sed gawk tar gzip diffutils \
+      ca-certificates; \
+    microdnf clean all; \
+    rm -rf /var/cache/* /var/log/dnf*
+
+COPY --from=builder /out/kubectl /out/chainsaw /usr/local/bin/
+
+# The nonroot account is written directly rather than pulling in shadow-utils to run useradd
+# once. HOME is /workspace because at runtime that emptyDir is the only writable path.
+RUN set -eux; \
+    echo "runner:x:${RUNNER_UID}:${RUNNER_GID}:conformance runner:/workspace:/bin/bash" >> /etc/passwd; \
+    echo "runner:x:${RUNNER_GID}:" >> /etc/group; \
+    install -d -m 0775 -o "${RUNNER_UID}" -g "${RUNNER_GID}" /workspace
+
+# SYSTEM-level config, because HOME is an emptyDir that starts empty on every run and the
+# root filesystem is read-only — a runtime `--global` write would fail.
+# safe.directory=*: the init-container clones into the shared emptyDir and the main container
+# then runs `rev-parse` over it; any uid mismatch between the two would otherwise abort with
+# "detected dubious ownership". The repo is fetched fresh per run into an emptyDir, so there
+# is no pre-existing hostile checkout this relaxes a check against.
+RUN set -eux; \
+    printf '%s\n' \
+      '[safe]' \
+      '	directory = *' \
+      '[advice]' \
+      '	detachedHead = false' \
+      > /etc/gitconfig; \
+    chmod 0644 /etc/gitconfig
+
+# Provenance: what is actually in this layer, readable from a running pod.
+RUN set -eux; \
+    { echo "fedora=${FEDORA_VERSION}"; \
+      echo "chainsaw=${CHAINSAW_VERSION}"; \
+      echo "kubectl=${KUBECTL_VERSION}"; \
+      echo "bash=$(bash --version | head -1)"; \
+      echo "python3=$(python3 --version)"; \
+      echo "git=$(git --version)"; \
+    } > /etc/conformance-runner-versions; \
+    chmod 0444 /etc/conformance-runner-versions
+
+# Every writable path points into the `workspace` emptyDir — the root filesystem is
+# read-only and the admission policy forbids adding a third volume for scratch.
+ENV HOME=/workspace \
+    XDG_CACHE_HOME=/workspace/.cache \
+    XDG_CONFIG_HOME=/workspace/.config \
+    TMPDIR=/workspace/.tmp \
+    PYTHONDONTWRITEBYTECODE=1 \
+    CONF_ROOT=/workspace/conformance
+
+USER ${RUNNER_UID}:${RUNNER_GID}
+WORKDIR /workspace
+
+# No ENTRYPOINT on purpose. The admission policy pins `command: ["./run.sh"]` with
+# `workingDir: /workspace/conformance`; an ENTRYPOINT here would either be ignored or
+# prepend something the policy cannot see. `bash` is the interactive fallback for a human
+# debugging the image locally.
+CMD ["/bin/bash"]

conformance/incluster/README.md

@@ -27,7 +27,22 @@ credentials — the Job's own scoped ServiceAccount does (R-SEC-02).
   audit item.
 - `chainsaw-job.yaml` — the Job skeleton. Single entrypoint `./run.sh`; CI sets `args` to
   `--requirements <touched IDs>` (merge gate) or `--layer all --strict-coverage` (phase
-  exit). Image pinned to `versions.env` `CHAINSAW_IMAGE`.
+  exit). **Its `image:` is STALE**: it still names `ghcr.io/kyverno/chainsaw:v0.2.12`, which
+  (a) cannot run `./run.sh` at all and (b) is DENIED at admission. The trigger renders this
+  template per run with `CONFORMANCE_RUNNER_IMAGE` injected (plan §3 item 4, T-6.1b); until
+  that lands, treat the literal `image:` here as a placeholder, not a pin.
+- `Containerfile` — the **`conformance-runner`** image: `bash` + `python3` + `chainsaw` +
+  `kubectl` + `git`, non-root (numeric uid 65532) and working under a read-only root
+  filesystem. This is what the Job actually needs; the stock chainsaw image carries none of
+  it. Versions are `--build-arg`-injected from `infra/devcontainer/versions.env` — the single
+  source of truth — so the chainsaw/kubectl in the runner are the same pins the toolbox gate
+  uses. Read its header before changing the Job's `args`: `run.sh` runs the selected offline
+  L0/L1 checks for any non-offline-only selection, and those need flux/promtool/kyverno/
+  kustomize, which this image deliberately omits. Use `--layer l2` / `--layer l3`.
+- `build-image.sh` — builds the above, **verifies the toolchain by running it** inside the
+  image as uid 65532 with `--read-only`, and prints the digest. It **never pushes**: it
+  prints the exact `podman push --digestfile …` command for the operator instead. See
+  `conformance/versions.env` `CONFORMANCE_RUNNER_IMAGE` for the post-push pin.
 
 ## Flow
 1. CI (Gitea Actions, delivered in T-6.1b) creates a Job from `chainsaw-job.yaml` (via a

conformance/incluster/build-image.sh

@@ -0,0 +1,156 @@
+#!/usr/bin/env bash
+###############################################################################
+# conformance/incluster/build-image.sh — build the pinned `conformance-runner`
+# image and print its digest. Closes docs/plans/l2-l3-conformance-ci-wiring.md §3 item 1.
+#
+#   ./build-image.sh                 # build + verify + print the digest and push command
+#   ./build-image.sh --no-verify     # build only (skip the in-image tool proof)
+#   ENGINE=docker ./build-image.sh   # build with docker instead of podman
+#
+# THIS SCRIPT NEVER PUSHES. Publishing is an operator action: the registry credential is
+# not an agent's to hold, and the pushed digest is what a fail-closed admission policy
+# then trusts. So this builds locally, proves the toolchain works INSIDE the image as the
+# non-root uid the policy demands, and prints the exact `podman push` line for a human.
+#
+# VERSIONS ARE NOT DEFINED HERE. They are read from infra/devcontainer/versions.env, the
+# single source of truth (CHAINSAW_VERSION, KUBECTL_VERSION, FEDORA_VERSION) — the same
+# pins the toolbox gate runs with. Nothing in this file invents a version.
+#
+# THE DIGEST CAVEAT — read it before pasting a digest into anything.
+# The digest printed here is the LOCAL manifest digest. It is normally identical to the
+# registry digest (podman pushes the manifest it already has rather than recompressing),
+# but that is a property of the push, not a guarantee. So the push command below uses
+# `--digestfile`: the digest the registry actually returns is the authoritative one, and
+# that is the one that goes into conformance/versions.env.
+###############################################################################
+set -euo pipefail
+
+HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "${HERE}/../.." && pwd)"
+ENGINE="${ENGINE:-podman}"
+
+VERIFY=1
+for arg in "$@"; do
+  case "$arg" in
+    --no-verify) VERIFY=0 ;;
+    -h|--help) sed -n '2,/^####/p' "${BASH_SOURCE[0]}" | sed '$d' | sed 's/^# \{0,1\}//'; exit 0 ;;
+    *) echo "unknown argument: $arg" >&2; exit 2 ;;
+  esac
+done
+
+log()  { printf '\n\033[1m==> %s\033[0m\n' "$*"; }
+info() { printf '    %s\n' "$*"; }
+die()  { printf '\033[31mERROR: %s\033[0m\n' "$*" >&2; exit 1; }
+
+command -v "${ENGINE}" >/dev/null 2>&1 || die "'${ENGINE}' not on PATH (set ENGINE=docker to use docker)"
+
+# --- pins: sourced, never invented -------------------------------------------
+TOOLCHAIN_ENV="${REPO_ROOT}/infra/devcontainer/versions.env"
+[ -f "${TOOLCHAIN_ENV}" ] || die "missing ${TOOLCHAIN_ENV} — the pins live there, not here"
+# shellcheck disable=SC1090
+source "${TOOLCHAIN_ENV}"
+: "${CHAINSAW_VERSION:?CHAINSAW_VERSION not set in ${TOOLCHAIN_ENV}}"
+: "${KUBECTL_VERSION:?KUBECTL_VERSION not set in ${TOOLCHAIN_ENV}}"
+: "${FEDORA_VERSION:?FEDORA_VERSION not set in ${TOOLCHAIN_ENV}}"
+
+# --- image name: fixed by the admission policy -------------------------------
+# platform/kyverno/admission/conformance-trigger-job-shape.yaml admits ONLY
+# gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:*. The repository path
+# is therefore not a preference; a different path is a DENIED Job. Do not "improve" it here.
+IMAGE_REPO="gitea.home.keithjackson.dev/home-network/conformance-runner"
+# The tag is build convenience only (a human-readable handle for the push). Admission
+# ignores it: only the digest is ever referenced from a Job.
+IMAGE_TAG="chainsaw${CHAINSAW_VERSION}-kubectl${KUBECTL_VERSION}-fc${FEDORA_VERSION}"
+IMAGE_REF="${IMAGE_REPO}:${IMAGE_TAG}"
+
+log "Building ${IMAGE_REF}"
+info "engine            ${ENGINE} ($(${ENGINE} --version 2>/dev/null | head -1))"
+info "pins from         ${TOOLCHAIN_ENV}"
+info "  CHAINSAW        ${CHAINSAW_VERSION}"
+info "  KUBECTL         ${KUBECTL_VERSION}"
+info "  FEDORA          ${FEDORA_VERSION}"
+
+"${ENGINE}" build \
+  --file "${HERE}/Containerfile" \
+  --tag "${IMAGE_REF}" \
+  --build-arg "CHAINSAW_VERSION=${CHAINSAW_VERSION}" \
+  --build-arg "KUBECTL_VERSION=${KUBECTL_VERSION}" \
+  --build-arg "FEDORA_VERSION=${FEDORA_VERSION}" \
+  "${HERE}"
+
+# --- verify: the point of the whole exercise ---------------------------------
+# The stock chainsaw image "had" chainsaw and still could not run ./run.sh. So prove the
+# tools EXECUTE, and prove they execute as the NON-ROOT uid with a READ-ONLY root
+# filesystem — the shape the admission policy forces. A pass here is the only evidence
+# this image is usable; a build that merely succeeded is not.
+if [ "${VERIFY}" -eq 1 ]; then
+  log "Verifying the toolchain inside the image (non-root, read-only rootfs)"
+  "${ENGINE}" run --rm \
+    --user 65532:65532 \
+    --read-only \
+    --tmpfs /workspace:rw,mode=1777 \
+    --entrypoint "" \
+    "${IMAGE_REF}" \
+    /bin/bash -euo pipefail -c '
+      echo "--- id ---";             id
+      echo "--- HOME ---";           echo "HOME=${HOME}"
+      echo "--- bash ---";           bash --version | head -1
+      echo "--- python3 ---";        python3 --version
+      echo "--- git ---";            git --version
+      echo "--- kubectl ---";        kubectl version --client
+      echo "--- chainsaw ---";       chainsaw version
+      echo "--- baked versions ---"; cat /etc/conformance-runner-versions
+      echo "--- rootfs is read-only (expected: a failure) ---"
+      if touch /should-fail 2>/dev/null; then echo "UNEXPECTED: rootfs is writable"; exit 1; fi
+      echo "confirmed: / is read-only"
+      echo "--- HOME is writable (the workspace emptyDir) ---"
+      touch "${HOME}/.probe" && echo "confirmed: ${HOME} is writable"
+      echo "--- uid is non-zero ---"
+      [ "$(id -u)" -ne 0 ] && echo "confirmed: running as uid $(id -u), not root"
+    '
+  log "Toolchain verified"
+fi
+
+# --- digest ------------------------------------------------------------------
+DIGEST="$("${ENGINE}" image inspect --format '{{.Digest}}' "${IMAGE_REF}")"
+IMAGE_ID="$("${ENGINE}" image inspect --format '{{.Id}}' "${IMAGE_REF}")"
+SIZE="$("${ENGINE}" image inspect --format '{{.Size}}' "${IMAGE_REF}")"
+
+log "Built ${IMAGE_REF}"
+info "local manifest digest  ${DIGEST}"
+info "image id               ${IMAGE_ID}"
+info "size                   $(( SIZE / 1024 / 1024 )) MiB"
+
+cat <<EOF
+
+================================================================================
+NOT PUSHED. Publishing is an operator action — this script holds no registry
+credential and will never acquire one.
+
+OPERATOR: run these two commands, then paste the digest from the digestfile into
+conformance/versions.env (CONFORMANCE_RUNNER_IMAGE) via a PR:
+
+    ${ENGINE} login gitea.home.keithjackson.dev
+
+    ${ENGINE} push --digestfile /tmp/conformance-runner.digest \\
+      ${IMAGE_REF}
+
+Then:
+
+    cat /tmp/conformance-runner.digest
+    # -> sha256:....  THIS is the authoritative digest, not the local one above.
+
+    # conformance/versions.env
+    CONFORMANCE_RUNNER_IMAGE="${IMAGE_REPO}@\$(cat /tmp/conformance-runner.digest)"
+
+WHY THE DIGEST AND NOT THE TAG: platform/kyverno/admission/conformance-trigger-job-shape.yaml
+is a fail-closed Enforce policy. It DENIES any conformance-trigger Job whose image is not
+${IMAGE_REPO}@sha256:<digest>. A tag reference is denied,
+and so is any other repository path.
+
+TIGHTEN THE BOUNDARY AFTERWARDS: that policy's header asks for the wildcard
+\`${IMAGE_REPO}@sha256:*\` to be replaced with the
+LITERAL digest once the image exists, closing the "anyone who can push to this path" gap.
+That is a separate, human-reviewed PR against the security boundary.
+================================================================================
+EOF

conformance/versions.env

@@ -6,6 +6,10 @@
 
 # Chainsaw — L1 rendering / L2 behavioral / L3 fault-injection runner (ADR-0011).
 CHAINSAW_VERSION="v0.2.12"
+# The UPSTREAM chainsaw image. It is NOT what the in-cluster Job runs — see
+# CONFORMANCE_RUNNER_IMAGE below. It carries the chainsaw binary and essentially nothing
+# else (no bash, no python3, no kubectl, no git), so `command: ["./run.sh"]` on this image
+# fails at exec. Kept only as the provenance of the chainsaw binary we rebuild from.
 CHAINSAW_IMAGE="ghcr.io/kyverno/chainsaw:v0.2.12"
 
 # kubectl — used by run.sh for cluster reachability preflight and by probe scripts.
@@ -18,3 +22,46 @@ KYVERNO_VERSION="v1.19.0"
 # Python 3 — coverage generator + JUnit emitter use stdlib only (no pip deps), so the
 # only constraint is a modern interpreter.
 PYTHON_MIN="3.9"
+
+# --- In-cluster conformance runner image -------------------------------------
+# Built from conformance/incluster/Containerfile by conformance/incluster/build-image.sh.
+# This — not CHAINSAW_IMAGE — is what the L2/L3 Job runs (bash + python3 + chainsaw +
+# kubectl + git). Closes docs/plans/l2-l3-conformance-ci-wiring.md §3 item 1.
+#
+# THE REPOSITORY PATH IS NOT A PREFERENCE. platform/kyverno/admission/
+# conformance-trigger-job-shape.yaml is a fail-closed Enforce ClusterPolicy (R-SEC-02) that
+# ADMITS a conformance-trigger Job only when its image matches
+#   gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:*
+# Any other path, and any TAG reference, is DENIED at admission. Do not "tidy" these values.
+CONFORMANCE_RUNNER_IMAGE_REPO="gitea.home.keithjackson.dev/home-network/conformance-runner"
+# Build handle only. Admission never sees the tag; a Job must reference the digest.
+CONFORMANCE_RUNNER_IMAGE_TAG="chainsaw0.2.12-kubectl1.36.4-fc44"
+#
+# ############################################################################
+# # DIGEST DELIBERATELY EMPTY — THE IMAGE HAS NOT BEEN PUBLISHED YET.        #
+# ############################################################################
+# The image has been BUILT and its toolchain verified locally (non-root uid 65532,
+# read-only rootfs: bash 5.3.9, Python 3.14.7, git 2.55.0, kubectl v1.36.4, chainsaw 0.2.12,
+# and `./run.sh --layer l2 --no-cluster` completing with rc 0). It has NOT been pushed:
+# pushing needs a registry credential, and publishing the artifact a fail-closed security
+# boundary then trusts is an OPERATOR action, not an agent's.
+#
+# OPERATOR, to complete the pin:
+#   1. ./conformance/incluster/build-image.sh          # rebuild, verify, print the commands
+#   2. podman login gitea.home.keithjackson.dev
+#   3. podman push --digestfile /tmp/conformance-runner.digest \
+#        "${CONFORMANCE_RUNNER_IMAGE_REPO}:${CONFORMANCE_RUNNER_IMAGE_TAG}"
+#   4. Set CONFORMANCE_RUNNER_IMAGE_DIGEST below to `cat /tmp/conformance-runner.digest`
+#      — the digest the REGISTRY returned, not the local manifest digest the build printed.
+#   5. Land steps 4 in a PR (this file is GitOps input, not a live edit).
+#
+# UNTIL THEN: this is empty on purpose, NOT a placeholder to be guessed at. An empty value
+# makes any consumer that renders the Job fail visibly; a fake or stale digest would instead
+# produce an ImagePullBackOff that looks like a cluster fault. Do not invent one.
+CONFORMANCE_RUNNER_IMAGE_DIGEST=""
+CONFORMANCE_RUNNER_IMAGE="${CONFORMANCE_RUNNER_IMAGE_DIGEST:+${CONFORMANCE_RUNNER_IMAGE_REPO}@${CONFORMANCE_RUNNER_IMAGE_DIGEST}}"
+#
+# AFTERWARDS, TIGHTEN THE BOUNDARY: the header of conformance-trigger-job-shape.yaml asks for
+# its `@sha256:*` wildcard to be replaced with the LITERAL digest once the image exists —
+# that closes the residual "anyone who can push to this path" gap. Separate PR, human
+# reviewed, because it edits the security boundary itself.