diff --git a/.gitea/workflows/reusable/node-quality.yml b/.gitea/workflows/reusable/node-quality.yml
index 328a385..cd0daee 100644
--- a/.gitea/workflows/reusable/node-quality.yml
+++ b/.gitea/workflows/reusable/node-quality.yml
@@ -143,6 +143,19 @@ jobs:
             $env_args \
             "${{ inputs.node-image }}" sh -euxc '${{ inputs.install-command }} && ${{ inputs.quality-command }}'
 
-      - name: cleanup per-run cache dir
+      # PLAT-014: the helper container writes root-owned files (tsx workers,
+      # playwright, compile caches) into the per-run cache mount; the host job
+      # runs as non-root gitea-runner since the 2026-08-30 runner governance,
+      # so a host-side rm -rf fails with EACCES and reds the job (playbook #18
+      # family). Clean as container root using the image this job already
+      # pulled, then rmdir the host-created directory itself.
+      - name: cleanup per-run cache dir (container root)
         if: always() && inputs.cache-mode == 'per-run'
-        run: rm -rf -- "${TOOL_CACHE_DIR:-}"
+        run: |
+          set -eu
+          [ -n "${TOOL_CACHE_DIR:-}" ] || exit 0
+          docker run --rm \
+            -v "${TOOL_CACHE_DIR}":/cleanup-root \
+            "${{ inputs.node-image }}" \
+            find /cleanup-root -mindepth 1 -delete
+          rmdir "${TOOL_CACHE_DIR}"
diff --git a/.gitea/workflows/reusable/oci-build-push-verify.yml b/.gitea/workflows/reusable/oci-build-push-verify.yml
index eccb6c2..990c7ae 100644
--- a/.gitea/workflows/reusable/oci-build-push-verify.yml
+++ b/.gitea/workflows/reusable/oci-build-push-verify.yml
@@ -305,6 +305,15 @@ jobs:
           } >>"${GITHUB_STEP_SUMMARY:-/dev/stdout}"
           cat "$digest_file"
 
-      - name: cleanup per-run cache dir
+      # PLAT-014: same ownership fix as node-quality — see the comment there
+      # (host non-root runner cannot rm container-root-owned cache files).
+      - name: cleanup per-run cache dir (container root)
         if: always() && inputs.build-command != '' && inputs.cache-mode == 'per-run'
-        run: rm -rf -- "${TOOL_CACHE_DIR:-}"
+        run: |
+          set -eu
+          [ -n "${TOOL_CACHE_DIR:-}" ] || exit 0
+          docker run --rm \
+            -v "${TOOL_CACHE_DIR}":/cleanup-root \
+            "${{ inputs.node-image }}" \
+            find /cleanup-root -mindepth 1 -delete
+          rmdir "${TOOL_CACHE_DIR}"
diff --git a/README.md b/README.md
index e3926c6..fad7676 100644
--- a/README.md
+++ b/README.md
@@ -33,6 +33,7 @@ jobs:
 ## 迁移与同步
 
 - 2026-08-27 定稿：曾按初版决策试建 est/ci-workflows，因 est org 私有闸门不可跨仓调用而删除（用户改批 mu-ref 宿主）；同日自 est/Est-Infra 上移 tools/ci。
+- 2026-08-31 v4（PLAT-014，Issue #75）：per-run 缓存清理步改容器 root 执行（node-image `find /cleanup-root -mindepth 1 -delete` + 宿主 `rmdir`）——08-30 非 root runner 治理后宿主 rm 撞容器 root 属主文件必 EACCES（坑 #18 同族，Seabed run 917 两次复现）；v3 保持不动，per-run 调用方（est/Seabed）应升 @v4，fixed 模式调用方（est/Reef）无清理步可留 @v3。
 - 2026-08-29 v3：模板 checkout 恢复 mu-ref/actions-checkout@v4（JS action）+ HEAD==SHA postcondition——P1-10 的 JS 迁移（est/Est-Infra@57cc9f7，08-27 09:39）在 08-27 12:07 上移建仓时被回退为 P1-7 host-clone fallback 血统，v3 恢复并经 Seabed 私仓探针验证；无调用方的孤儿模板 `reusable/checkout.yml` 删除（reusable 不可嵌套调用，其守卫已内联进两个模板）。
 - helper Dockerfile 的可复现 bake 与 ops 巡检脚本仍属项目级（Est-Infra / gitea-host-setup）。