diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b074b4a..0d1f17e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -63,6 +63,9 @@ jobs:
     needs: verify
     runs-on: ubuntu-latest
     timeout-minutes: 10
+    env:
+      # Names this job's stacks, so its final step removes exactly these (scripts/lib/ci-project.sh).
+      EKKLESIA_CI_JOB_KEY: infrastructure-smoke
     steps:
       - name: Check out repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
@@ -72,13 +75,29 @@ jobs:
           # in this workflow pushes, so the credential is never needed after checkout.
           persist-credentials: false
 
+      # A job the runner killed (cancelled, or past the runner's own time limit) never ran its
+      # cleanup. Anything a CI job left on this shared daemon more than three hours ago goes first.
+      - name: Sweep stale CI stacks from the runner
+        run: bash scripts/ci-sweep.sh --stale
+
+      - name: Prove the sweep removes exactly what it should, against real Docker resources
+        run: bash scripts/test-ci-sweep.sh
+
       - name: Exercise PostgreSQL and S3 infrastructure
         run: bash scripts/smoke-infrastructure.sh
 
+      # Whatever happened above, this job's own stacks do not outlive it.
+      - name: Remove this job's CI stacks
+        if: always()
+        run: bash scripts/ci-sweep.sh --job
+
   migration-smoke:
     needs: verify
     runs-on: ubuntu-latest
     timeout-minutes: 15
+    env:
+      # Names this job's stacks, so its final step removes exactly these (scripts/lib/ci-project.sh).
+      EKKLESIA_CI_JOB_KEY: migration-smoke
     steps:
       - name: Check out repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
@@ -88,6 +107,11 @@ jobs:
           # in this workflow pushes, so the credential is never needed after checkout.
           persist-credentials: false
 
+      # A job the runner killed (cancelled, or past the runner's own time limit) never ran its
+      # cleanup. Anything a CI job left on this shared daemon more than three hours ago goes first.
+      - name: Sweep stale CI stacks from the runner
+        run: bash scripts/ci-sweep.sh --stale
+
       - name: Set up Node.js
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
         with:
@@ -104,11 +128,18 @@ jobs:
       - name: Exercise transactional migrations against PostgreSQL
         run: pnpm test:migrations:integration
 
+      # Whatever happened above, this job's own stacks do not outlive it.
+      - name: Remove this job's CI stacks
+        if: always()
+        run: bash scripts/ci-sweep.sh --job
+
   image-build:
     needs: verify
     runs-on: ubuntu-latest
     timeout-minutes: 20
     env:
+      # Names this job's stacks, so its final step removes exactly these (scripts/lib/ci-project.sh).
+      EKKLESIA_CI_JOB_KEY: image-build
       # Cache mounts in deploy/Dockerfile need BuildKit; this selects it even where the Docker CLI
       # has no buildx plugin.
       DOCKER_BUILDKIT: "1"
@@ -121,22 +152,33 @@ jobs:
           # in this workflow pushes, so the credential is never needed after checkout.
           persist-credentials: false
 
+      # A job the runner killed (cancelled, or past the runner's own time limit) never ran its
+      # cleanup. Anything a CI job left on this shared daemon more than three hours ago goes first.
+      - name: Sweep stale CI stacks from the runner
+        run: bash scripts/ci-sweep.sh --stale
+
       # The platform-only image (ADR 0044): a checkout has no `modules/`, so this proves the image
       # builds, validates, and assembles with zero modules. Build only — no registry login, no
       # credentials, no push, no tag anywhere but this runner's local image store.
       # Tagged per run and attempt, not only per commit: a pull request and a push of the same commit
       # can build at once on one runner's Docker daemon, and neither may remove the other's image.
+      # Labeled like every CI stack, so this job's final step removes it even if the build is killed.
       - name: Build the production image without modules
-        run: >-
-          docker build
-          --file deploy/Dockerfile
-          --build-arg REVISION="$GITHUB_SHA"
-          --tag ekklesia-ci:"$GITHUB_SHA-${GITHUB_RUN_ID:-0}-${GITHUB_RUN_ATTEMPT:-1}"
-          .
+        shell: bash
+        run: |
+          source scripts/lib/ci-project.sh
+          docker build \
+            --file deploy/Dockerfile \
+            --build-arg REVISION="$GITHUB_SHA" \
+            --label "${EKKLESIA_CI_LABEL}=$(ci_project_name image)" \
+            --label "${EKKLESIA_CI_CREATED_LABEL}=$(date +%s)" \
+            --tag ekklesia-ci:"$GITHUB_SHA-${GITHUB_RUN_ID:-0}-${GITHUB_RUN_ATTEMPT:-1}" \
+            .
 
-      - name: Remove the image from the runner
+      # Whatever happened above, this job's own stacks do not outlive it.
+      - name: Remove this job's CI stacks
         if: always()
-        run: docker image rm --force ekklesia-ci:"$GITHUB_SHA-${GITHUB_RUN_ID:-0}-${GITHUB_RUN_ATTEMPT:-1}" || true
+        run: bash scripts/ci-sweep.sh --job
 
   deploy-smoke:
     needs: verify
@@ -151,6 +193,8 @@ jobs:
           - same-origin
           - split
     env:
+      # Names this job's stacks, so its final step removes exactly these (scripts/lib/ci-project.sh).
+      EKKLESIA_CI_JOB_KEY: deploy-smoke-${{ matrix.topology }}
       DOCKER_BUILDKIT: "1"
       EKKLESIA_SMOKE_TOPOLOGY: ${{ matrix.topology }}
     steps:
@@ -162,6 +206,11 @@ jobs:
           # in this workflow pushes, so the credential is never needed after checkout.
           persist-credentials: false
 
+      # A job the runner killed (cancelled, or past the runner's own time limit) never ran its
+      # cleanup. Anything a CI job left on this shared daemon more than three hours ago goes first.
+      - name: Sweep stale CI stacks from the runner
+        run: bash scripts/ci-sweep.sh --stale
+
       # The reference deployment end to end (ADR 0044): a platform-only image, base + proxy with
       # Caddy's internal CA (test-only), an explicit migration apply against this job's own fresh
       # PostgreSQL, then the API, Dashboard, storage delivery, client-address chain, and verify-full
@@ -169,3 +218,8 @@ jobs:
       # it; nothing is pushed, published, or logged in to.
       - name: Smoke-test the reference deployment (${{ matrix.topology }})
         run: bash scripts/smoke-deploy.sh
+
+      # Whatever happened above, this job's own stacks do not outlive it.
+      - name: Remove this job's CI stacks
+        if: always()
+        run: bash scripts/ci-sweep.sh --job
diff --git a/docs/development/security.md b/docs/development/security.md
index 56e692b..5291347 100644
--- a/docs/development/security.md
+++ b/docs/development/security.md
@@ -746,6 +746,33 @@ The declarations are kept deliberately: they are already correct for a supported
 for GitHub Actions, and keeping them means the upgrade does not require re-deriving the intent. They
 are documented as ignored, not removed.
 
+### Disposable stacks never outlive their job
+
+Every CI script removes its own Compose stack in an `EXIT` trap, but a trap never runs when the runner
+kills the job container: a cancelled job, or the runner's own time limit. One such stack ran on the
+shared runner for two days. So stack cleanup has three layers:
+
+- **The script's own trap**, for every ordinary failure.
+- **A final `if: always()` step** in every job that starts stacks: `scripts/ci-sweep.sh --job` removes
+  everything that job started, at any age, even after a failed step.
+- **A sweep before every such job starts**: `scripts/ci-sweep.sh --stale` removes anything a CI job
+  left more than three hours ago, which catches whatever a killed job could not clean up itself.
+
+A stack is found by name and label, never by guesswork (`scripts/lib/ci-project.sh`):
+
+- every CI Compose project is named `ekklesia-ci-<run>-<attempt>-<job key>-…`, and Compose labels
+  its containers, networks, and volumes with that name;
+- anything a script starts outside Compose carries `org.riverofglorymn.ekklesia.ci.project`;
+- images also carry the time CI built them, because an image's own creation time can be its base's.
+
+The job key is per matrix leg, so one leg's cleanup cannot match another's running stack. Nothing
+outside the `ekklesia-ci-` prefix is ever removed. A job container attached to a stack's network is
+disconnected, never removed.
+
+**This is not a substitute for a runner-side reaper.** A stack killed with its job is removed only
+when another job that sweeps runs on the same runner. Bounded execution and teardown are still the
+runner host's to enforce, as above.
+
 ### Runner topology is not verified
 
 **The runner topology is not verified in this repository and is not documented here as though it
diff --git a/docs/development/testing.md b/docs/development/testing.md
index 218427c..d4a9f18 100644
--- a/docs/development/testing.md
+++ b/docs/development/testing.md
@@ -159,6 +159,12 @@ also receives a safely named disposable database. Direct host runs use a Docker-
 port bound only to `127.0.0.1`; a containerized Gitea job joins the isolated Compose network and
 uses the PostgreSQL service name.
 
+In CI, a stack whose job was killed before its own cleanup ran is still removed: by that job's final
+`if: always()` step, or by the stale sweep before a later job starts (`scripts/ci-sweep.sh`, see
+[Disposable stacks never outlive their job](security.md#disposable-stacks-never-outlive-their-job)).
+`bash scripts/test-ci-sweep.sh` proves what the sweep removes and what it leaves alone, against real
+Docker resources.
+
 The live suite proves fresh read-only planning, initial and incremental application, genuine
 no-op behavior, exact applied checksums and history, edited or corrupt history rejection,
 whole-batch DDL rollback, Drizzle breakpoint execution, real advisory-lock concurrency and
diff --git a/scripts/ci-sweep.sh b/scripts/ci-sweep.sh
new file mode 100755
index 0000000..681fa88
--- /dev/null
+++ b/scripts/ci-sweep.sh
@@ -0,0 +1,205 @@
+#!/usr/bin/env bash
+# Removes disposable CI stacks from the Docker daemon: containers, networks, volumes, images, and
+# staging directories on the Docker host.
+#
+#   bash scripts/ci-sweep.sh --stale [--max-age-seconds N]   any CI stack older than N (default 3 h)
+#   bash scripts/ci-sweep.sh --job                           this job's own stacks, at any age
+#
+# Every CI script already removes its own stack in an EXIT trap, but a trap never runs when the runner
+# kills the job container: a cancelled job, or the runner's own time limit (Gitea 1.24 ignores
+# `timeout-minutes`). So each workflow job that starts stacks ends with `--job` in an `if: always()`
+# step, and begins with `--stale`, which catches whatever a killed job left before it could clean up.
+#
+# What a stack is, and how it is found, is defined in scripts/lib/ci-project.sh: a Compose project
+# named with the `ekklesia-ci-` prefix (Compose labels everything it creates with that name), plus
+# anything labeled EKKLESIA_CI_LABEL. Nothing outside that prefix is ever touched, at any age.
+#
+# --stale's threshold is far above any job's run time, so a stack another job on this daemon is using
+# right now is never young enough to match. --job refuses to run outside CI: locally, its prefix would
+# match a developer's own stacks.
+#
+# Best effort by design: a resource that cannot be removed is reported, and the sweep goes on. Output
+# names resources only; nothing a stack holds is printed.
+
+set -Eeuo pipefail
+
+repository_root="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+# shellcheck source=scripts/lib/ci-project.sh
+source "$repository_root/scripts/lib/ci-project.sh"
+
+compose_label="com.docker.compose.project"
+mode=""
+max_age_seconds="${EKKLESIA_CI_SWEEP_MAX_AGE_SECONDS:-10800}"
+
+usage() {
+  echo "usage: ci-sweep.sh --stale [--max-age-seconds N] | --job" >&2
+  exit 2
+}
+
+while (($# > 0)); do
+  case "$1" in
+  --stale | --job)
+    [[ -z "$mode" ]] || usage
+    mode="${1#--}"
+    ;;
+  --max-age-seconds)
+    [[ "${2:-}" =~ ^[0-9]+$ ]] || usage
+    max_age_seconds="$2"
+    shift
+    ;;
+  *) usage ;;
+  esac
+  shift
+done
+[[ -n "$mode" ]] || usage
+
+if [[ "$mode" == job ]]; then
+  [[ -n "${GITHUB_RUN_ID:-}" ]] || {
+    echo "ci-sweep: --job runs only in CI (GITHUB_RUN_ID is unset); locally it would match your own stacks." >&2
+    exit 2
+  }
+  prefix="$(ci_job_prefix)"
+  cutoff=""
+else
+  prefix="$EKKLESIA_CI_PREFIX"
+  cutoff="$(($(date +%s) - max_age_seconds))"
+fi
+
+if ! docker info >/dev/null 2>&1; then
+  echo "ci-sweep: no Docker daemon reachable; nothing to sweep."
+  exit 0
+fi
+
+removed=0
+warn() {
+  echo "ci-sweep: warning: $*" >&2
+}
+
+# selected <project> <created>: whether a resource belongs to the sweep.
+selected() {
+  local project="$1" created="$2" seconds
+  [[ -n "$project" && "$project" == "$prefix"* ]] || return 1
+  [[ -z "$cutoff" ]] && return 0
+  seconds="$(date -d "$created" +%s 2>/dev/null)" || return 1
+  ((seconds <= cutoff))
+}
+
+# --- Containers: Compose's own, and those a script started itself --------------------------------
+mapfile -t containers < <(
+  {
+    docker ps --all --quiet --no-trunc --filter "label=${compose_label}"
+    docker ps --all --quiet --no-trunc --filter "label=${EKKLESIA_CI_LABEL}"
+  } | sort -u
+)
+for id in "${containers[@]}"; do
+  [[ -n "$id" ]] || continue
+  record="$(docker inspect --format \
+    "{{index .Config.Labels \"${compose_label}\"}}|{{index .Config.Labels \"${EKKLESIA_CI_LABEL}\"}}|{{.Created}}|{{.Name}}" \
+    "$id" 2>/dev/null)" || continue
+  IFS='|' read -r compose_project ci_project created name <<<"$record"
+  project="${compose_project:-$ci_project}"
+  selected "$project" "$created" || continue
+  if docker rm --force --volumes "$id" >/dev/null 2>&1; then
+    echo "ci-sweep: removed container ${name#/} (${project})"
+    removed=$((removed + 1))
+  else
+    warn "could not remove container ${name#/}"
+  fi
+done
+
+# --- Networks: anything still attached (a job container) is disconnected, never removed ---------
+mapfile -t networks < <(docker network ls --quiet --no-trunc --filter "label=${compose_label}")
+for id in "${networks[@]}"; do
+  [[ -n "$id" ]] || continue
+  # A network's creation time is a time value, not a string: ask for RFC 3339, which `date` reads.
+  record="$(docker network inspect --format \
+    "{{index .Labels \"${compose_label}\"}}|{{.Created.Format \"2006-01-02T15:04:05Z07:00\"}}|{{.Name}}" \
+    "$id" 2>/dev/null)" || continue
+  IFS='|' read -r project created name <<<"$record"
+  selected "$project" "$created" || continue
+  for endpoint in $(docker network inspect --format '{{range $id, $_ := .Containers}}{{$id}} {{end}}' "$id" 2>/dev/null); do
+    docker network disconnect --force "$id" "$endpoint" >/dev/null 2>&1 ||
+      warn "could not disconnect a container from network ${name}"
+  done
+  if docker network rm "$id" >/dev/null 2>&1; then
+    echo "ci-sweep: removed network ${name} (${project})"
+    removed=$((removed + 1))
+  else
+    warn "could not remove network ${name}"
+  fi
+done
+
+# --- Volumes ---------------------------------------------------------------------------------------
+mapfile -t volumes < <(
+  {
+    docker volume ls --quiet --filter "label=${compose_label}"
+    docker volume ls --quiet --filter "label=${EKKLESIA_CI_LABEL}"
+  } | sort -u
+)
+for name in "${volumes[@]}"; do
+  [[ -n "$name" ]] || continue
+  record="$(docker volume inspect --format \
+    "{{index .Labels \"${compose_label}\"}}|{{index .Labels \"${EKKLESIA_CI_LABEL}\"}}|{{.CreatedAt}}" \
+    "$name" 2>/dev/null)" || continue
+  IFS='|' read -r compose_project ci_project created <<<"$record"
+  project="${compose_project:-$ci_project}"
+  selected "$project" "$created" || continue
+  if docker volume rm --force "$name" >/dev/null 2>&1; then
+    echo "ci-sweep: removed volume ${name} (${project})"
+    removed=$((removed + 1))
+  else
+    warn "could not remove volume ${name}"
+  fi
+done
+
+# --- Images built for a stack ------------------------------------------------------------------------
+mapfile -t images < <(docker image ls --quiet --no-trunc --filter "label=${EKKLESIA_CI_LABEL}" | sort -u)
+for id in "${images[@]}"; do
+  [[ -n "$id" ]] || continue
+  # Judged by when CI built it (EKKLESIA_CI_CREATED_LABEL), never by the image's own creation time,
+  # which BuildKit may have taken from its base. An image without that label is never swept by age.
+  record="$(docker image inspect --format \
+    "{{index .Config.Labels \"${EKKLESIA_CI_LABEL}\"}}|{{index .Config.Labels \"${EKKLESIA_CI_CREATED_LABEL}\"}}" \
+    "$id" 2>/dev/null)" || continue
+  IFS='|' read -r project built <<<"$record"
+  if [[ -n "$cutoff" ]]; then
+    [[ "$built" =~ ^[0-9]+$ ]] || continue
+    selected "$project" "@${built}" || continue
+  else
+    selected "$project" "" || continue
+  fi
+  if docker image rm --force "$id" >/dev/null 2>&1; then
+    echo "ci-sweep: removed image ${id#sha256:} (${project})"
+    removed=$((removed + 1))
+  else
+    warn "could not remove image ${id#sha256:}"
+  fi
+done
+
+# --- Staging directories on the Docker host ------------------------------------------------------
+# A deploy smoke run inside a job container stages its mounted files under the Docker host's /tmp,
+# named for its project, as root-owned files; they hold that run's disposable secrets and keys. They
+# are removed with the same pinned image that created them. If that image is not on this daemon, no
+# smoke has staged anything here.
+image="$(sed -n 's/^[[:space:]]*image: \(postgres:[^[:space:]]*\)$/\1/p' "$repository_root/deploy/compose.yaml" | head -1)"
+if [[ -n "$image" ]] && docker image inspect "$image" >/dev/null 2>&1; then
+  age=()
+  # `find -mmin +0` does not match something younger than a minute, so a threshold under a minute
+  # sweeps without an age filter, like the rest of this script.
+  if [[ -n "$cutoff" ]] && ((max_age_seconds >= 60)); then
+    age=(-mmin "+$((max_age_seconds / 60))")
+  fi
+  if staged="$(docker run --rm --entrypoint find -v /tmp:/host-tmp "$image" \
+    /host-tmp -mindepth 1 -maxdepth 1 -type d -name "${prefix}*" "${age[@]}" \
+    -print -exec rm -rf {} + 2>/dev/null)"; then
+    while IFS= read -r directory; do
+      [[ -n "$directory" ]] || continue
+      echo "ci-sweep: removed staging directory /tmp/${directory#/host-tmp/}"
+      removed=$((removed + 1))
+    done <<<"$staged"
+  else
+    warn "could not sweep staging directories on the Docker host"
+  fi
+fi
+
+echo "ci-sweep: ${mode} sweep removed ${removed} resource(s)."
diff --git a/scripts/lib/ci-project.sh b/scripts/lib/ci-project.sh
new file mode 100644
index 0000000..a028dbc
--- /dev/null
+++ b/scripts/lib/ci-project.sh
@@ -0,0 +1,40 @@
+# shellcheck shell=bash
+# How CI names, labels, and later finds the disposable stacks it starts.
+#
+# Every Compose project a CI script starts is named
+#
+#   ekklesia-ci-<run id>-<run attempt>-<job key>-<kind>-<pid><random>
+#
+# and Compose labels every container, network, and volume it creates with that name. What a script
+# creates outside Compose (a browser container, a volume, an image) gets EKKLESIA_CI_LABEL with the
+# same name. scripts/ci-sweep.sh finds stacks by those labels: this job's own, by the prefix up to
+# the job key (in a final `if: always()` step), and any CI stack by age (before a job starts).
+#
+# The job key is EKKLESIA_CI_JOB_KEY, which the workflow sets per job, and per matrix leg where a job
+# has one, so that one leg's cleanup cannot match another leg's running stack. Outside CI the
+# identifiers are "local".
+
+# shellcheck disable=SC2034 # read by the scripts that source this
+EKKLESIA_CI_LABEL="org.riverofglorymn.ekklesia.ci.project"
+# On images, when they were built, in Unix seconds. An image's own creation time is not that: BuildKit
+# gives an image that only adds metadata its base's time, and a reproducible build a fixed one. A
+# stale sweep that trusted it could remove an image another job is using right now.
+EKKLESIA_CI_CREATED_LABEL="org.riverofglorymn.ekklesia.ci.created"
+EKKLESIA_CI_PREFIX="ekklesia-ci-"
+
+# ci_name_safe <text>: lower case, and only what a Compose project name may contain.
+ci_name_safe() {
+  local text="${1//[^a-zA-Z0-9_-]/-}"
+  printf '%s' "${text,,}"
+}
+
+# ci_job_prefix: every project this job starts begins with exactly this.
+ci_job_prefix() {
+  ci_name_safe "ekklesia-ci-${GITHUB_RUN_ID:-local}-${GITHUB_RUN_ATTEMPT:-0}-${EKKLESIA_CI_JOB_KEY:-${GITHUB_JOB:-local}}-"
+}
+
+# ci_project_name <kind>: a project name unique to this invocation. Not only per run: several runs,
+# and several jobs of one run, share a runner's Docker daemon, and job containers often share a PID.
+ci_project_name() {
+  ci_name_safe "ekklesia-ci-${GITHUB_RUN_ID:-local}-${GITHUB_RUN_ATTEMPT:-0}-${EKKLESIA_CI_JOB_KEY:-${GITHUB_JOB:-local}}-${1:?ci_project_name needs a kind}-$$-${RANDOM}${RANDOM}"
+}
diff --git a/scripts/smoke-deploy.sh b/scripts/smoke-deploy.sh
index 8ac81cc..ece1296 100755
--- a/scripts/smoke-deploy.sh
+++ b/scripts/smoke-deploy.sh
@@ -39,6 +39,8 @@ cd "$repository_root"
 
 # shellcheck source=scripts/lib/compose-diagnostics.sh
 source "$repository_root/scripts/lib/compose-diagnostics.sh"
+# shellcheck source=scripts/lib/ci-project.sh
+source "$repository_root/scripts/lib/ci-project.sh"
 
 for command in docker openssl awk; do
   command -v "$command" >/dev/null || {
@@ -67,7 +69,10 @@ same-origin | split) ;;
 esac
 
 run_id="$(openssl rand -hex 4)"
-project="ekklesia-deploy-smoke-${run_id}"
+# Unique per invocation, and findable by run and job if this script is killed before its trap runs
+# (scripts/lib/ci-project.sh, scripts/ci-sweep.sh). Everything started outside Compose below carries
+# the same name in EKKLESIA_CI_LABEL.
+project="$(ci_project_name "deploy-${topology}")"
 work="$(mktemp -d)"
 image="${EKKLESIA_SMOKE_IMAGE:-}"
 built_image=""
@@ -186,7 +191,9 @@ fail() {
 if [[ -z "$image" && "$topology" == same-origin ]]; then
   step "Building the platform-only image"
   built_image="ekklesia-deploy-smoke:${run_id}"
-  DOCKER_BUILDKIT=1 docker build --quiet --file deploy/Dockerfile --tag "$built_image" . >/dev/null
+  DOCKER_BUILDKIT=1 docker build --quiet --file deploy/Dockerfile --tag "$built_image" \
+    --label "${EKKLESIA_CI_LABEL}=${project}" --label "${EKKLESIA_CI_CREATED_LABEL}=$(date +%s)" \
+    . >/dev/null
   image="$built_image"
 elif [[ -z "$image" ]]; then
   # TEST-ONLY: the repository's module template, installed as the module `example`, in a copy of the
@@ -206,6 +213,7 @@ elif [[ -z "$image" ]]; then
   sed -i 's|^  templates/module:$|  modules/example:|' "$context/pnpm-lock.yaml"
   built_image="ekklesia-deploy-smoke:${run_id}"
   DOCKER_BUILDKIT=1 docker build --quiet --file "$context/deploy/Dockerfile" --tag "$built_image" \
+    --label "${EKKLESIA_CI_LABEL}=${project}" --label "${EKKLESIA_CI_CREATED_LABEL}=$(date +%s)" \
     "$context" >/dev/null || fail "the test-module image did not build."
   rm -rf "$context"
   image="$built_image"
@@ -362,6 +370,7 @@ client() {
   local mode="$1"
   shift
   docker run --rm --read-only --cap-drop ALL --security-opt no-new-privileges \
+    --label "${EKKLESIA_CI_LABEL}=${project}" \
     --network "$edge_network" "$@" "${host_mappings[@]}" \
     -e NODE_EXTRA_CA_CERTS=/smoke/client-ca.pem -e SMOKE_HOSTNAME="$hostname" \
     -e SMOKE_DASHBOARD_HOSTNAME="$dashboard_hostname" \
@@ -401,7 +410,7 @@ if [[ "$topology" == split ]]; then
   browser_container="${project}-browser"
   # The image's entry script passes its arguments on unquoted, so none may contain a space: the
   # hostnames reach Chromium through /etc/hosts, which it reads, rather than a resolver rule.
-  docker run --detach --rm --name "$browser_container" \
+  docker run --detach --rm --name "$browser_container" --label "${EKKLESIA_CI_LABEL}=${project}" \
     --cap-drop ALL --security-opt no-new-privileges --tmpfs /tmp \
     --network "$edge_network" --ip "$browser_address" "${host_mappings[@]}" \
     "$browser_image" \
@@ -410,6 +419,7 @@ if [[ "$topology" == split ]]; then
   cp scripts/lib/deploy-smoke-browser.mjs "$work/browser.mjs"
   stage browser.mjs
   docker run --rm --read-only --cap-drop ALL --security-opt no-new-privileges \
+    --label "${EKKLESIA_CI_LABEL}=${project}" \
     --network "$edge_network" \
     -e SMOKE_CDP_ADDRESS="${browser_address}:9222" \
     -e SMOKE_HOSTNAME="$hostname" -e SMOKE_DASHBOARD_HOSTNAME="$dashboard_hostname" \
@@ -423,9 +433,9 @@ if [[ "$topology" == split ]]; then
     kiosk_container="${project}-kiosk"
     kiosk_volume="${project}-kiosk-profile"
     kiosk_address="10.249.${octet}.250"
-    docker volume create "$kiosk_volume" >/dev/null
+    docker volume create --label "${EKKLESIA_CI_LABEL}=${project}" "$kiosk_volume" >/dev/null
     start_kiosk() {
-      docker run --detach --rm --name "$kiosk_container" \
+      docker run --detach --rm --name "$kiosk_container" --label "${EKKLESIA_CI_LABEL}=${project}" \
         --cap-drop ALL --security-opt no-new-privileges --tmpfs /tmp \
         --network "$edge_network" --ip "$kiosk_address" "${host_mappings[@]}" \
         -v "${kiosk_volume}:/profile" \
diff --git a/scripts/smoke-infrastructure.sh b/scripts/smoke-infrastructure.sh
index 8cbcebe..1165640 100755
--- a/scripts/smoke-infrastructure.sh
+++ b/scripts/smoke-infrastructure.sh
@@ -9,6 +9,8 @@ cd "$repository_root"
 source "$repository_root/scripts/lib/compose-job-network.sh"
 # shellcheck source=scripts/lib/compose-diagnostics.sh
 source "$repository_root/scripts/lib/compose-diagnostics.sh"
+# shellcheck source=scripts/lib/ci-project.sh
+source "$repository_root/scripts/lib/ci-project.sh"
 
 command -v docker >/dev/null || {
   echo "Docker is required for the infrastructure smoke test." >&2
@@ -30,11 +32,9 @@ if [[ "$curl_help" != *"--aws-sigv4"* ]]; then
   exit 1
 fi
 
-# Unique per invocation, not only per run: several runs can share a runner's Docker daemon at once,
-# and the shell's PID is often identical across job containers.
-raw_project="ekklesia-smoke-${GITHUB_RUN_ID:-local}-${GITHUB_RUN_ATTEMPT:-0}-$$-${RANDOM}${RANDOM}"
-project="${raw_project//[^a-zA-Z0-9_-]/-}"
-project="${project,,}"
+# Unique per invocation, and findable by run and job if this script is killed before its trap runs
+# (scripts/lib/ci-project.sh, scripts/ci-sweep.sh).
+project="$(ci_project_name infrastructure)"
 temporary_directory="$(mktemp -d)"
 payload_file="$temporary_directory/payload.txt"
 download_file="$temporary_directory/download.txt"
diff --git a/scripts/test-ci-sweep.sh b/scripts/test-ci-sweep.sh
new file mode 100755
index 0000000..ccb5def
--- /dev/null
+++ b/scripts/test-ci-sweep.sh
@@ -0,0 +1,129 @@
+#!/usr/bin/env bash
+# Proves scripts/ci-sweep.sh against real Docker resources: what it removes, and above all what it
+# leaves alone. CI runs it before trusting the sweep with a shared runner's daemon.
+#
+#   bash scripts/test-ci-sweep.sh
+#
+# Every resource it creates is named and labeled for this run alone, under fake run identifiers, so
+# it can never touch a real stack; and it removes all of them on exit, whatever happens.
+
+set -Eeuo pipefail
+
+repository_root="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$repository_root"
+
+image="$(sed -n 's/^[[:space:]]*image: \(postgres:[^[:space:]]*\)$/\1/p' deploy/compose.yaml | head -1)"
+[[ -n "$image" ]] || {
+  echo "test-ci-sweep: no pinned PostgreSQL image in deploy/compose.yaml." >&2
+  exit 1
+}
+docker image inspect "$image" >/dev/null 2>&1 || docker pull --quiet "$image" >/dev/null
+
+nonce="$(openssl rand -hex 4)"
+compose_label="com.docker.compose.project"
+ci_label="org.riverofglorymn.ekklesia.ci.project"
+failures=0
+created=()
+
+check() {
+  if eval "$1"; then
+    echo "ok   $2"
+  else
+    echo "FAIL $2"
+    failures=$((failures + 1))
+  fi
+}
+
+# project_exists <project>: any container, network, volume, or image still carries its label.
+project_exists() {
+  local project="$1"
+  [[ -n "$(
+    docker ps --all --quiet --filter "label=${compose_label}=${project}"
+    docker ps --all --quiet --filter "label=${ci_label}=${project}"
+    docker network ls --quiet --filter "label=${compose_label}=${project}"
+    docker volume ls --quiet --filter "label=${compose_label}=${project}"
+    docker image ls --quiet --filter "label=${ci_label}=${project}"
+  )" ]]
+}
+
+staging_exists() {
+  docker run --rm --entrypoint test -v /tmp:/host-tmp "$image" -d "/host-tmp/$1"
+}
+
+# make_stack <project>: what a CI script leaves behind when it is killed: a Compose-labeled network,
+# volume, and running container; a CI-labeled container and image; and a staging directory on the
+# Docker host.
+make_stack() {
+  local project="$1"
+  created+=("$project")
+  docker network create --label "${compose_label}=${project}" "${project}_default" >/dev/null
+  docker volume create --label "${compose_label}=${project}" "${project}_data" >/dev/null
+  docker run --detach --name "${project}-db" --label "${compose_label}=${project}" \
+    --network "${project}_default" -v "${project}_data:/data" --entrypoint sleep "$image" 600 >/dev/null
+  docker run --detach --name "${project}-browser" --label "${ci_label}=${project}" \
+    --entrypoint sleep "$image" 600 >/dev/null
+  printf 'FROM %s\nLABEL %s=%s %s=%s\n' "$image" "$ci_label" "$project" \
+    "org.riverofglorymn.ekklesia.ci.created" "$(date +%s)" |
+    docker build --quiet --tag "${project}-image:test" - >/dev/null
+  docker run --rm --entrypoint mkdir -v /tmp:/host-tmp "$image" -p "/host-tmp/${project}"
+}
+
+job_container="test-ci-sweep-job-${nonce}"
+cleanup() {
+  local status=$?
+  trap - EXIT INT TERM
+  docker rm --force "$job_container" >/dev/null 2>&1 || true
+  for project in "${created[@]}"; do
+    docker ps --all --quiet --filter "label=${compose_label}=${project}" | xargs -r docker rm --force >/dev/null 2>&1 || true
+    docker ps --all --quiet --filter "label=${ci_label}=${project}" | xargs -r docker rm --force >/dev/null 2>&1 || true
+    docker network rm "${project}_default" >/dev/null 2>&1 || true
+    docker volume rm --force "${project}_data" >/dev/null 2>&1 || true
+    docker image rm --force "${project}-image:test" >/dev/null 2>&1 || true
+    docker run --rm --entrypoint rm -v /tmp:/host-tmp "$image" -rf "/host-tmp/${project}" >/dev/null 2>&1 || true
+  done
+  exit "$status"
+}
+trap cleanup EXIT INT TERM
+
+# shellcheck source=scripts/lib/ci-project.sh
+source "$repository_root/scripts/lib/ci-project.sh"
+
+# Fake run identifiers: nothing here can match a real run's stacks.
+export GITHUB_RUN_ID="sweeptest${nonce}"
+export GITHUB_RUN_ATTEMPT="1"
+mine="$(EKKLESIA_CI_JOB_KEY=alpha ci_project_name mine)"
+sibling="$(EKKLESIA_CI_JOB_KEY=beta ci_project_name sibling)"
+foreign="ekklesia-sweep-control-${nonce}"
+for project in "$mine" "$sibling" "$foreign"; do
+  make_stack "$project"
+done
+# A job container connected to this job's stack network, exactly as compose-job-network.sh does.
+docker run --detach --name "$job_container" --entrypoint sleep "$image" 600 >/dev/null
+docker network connect "${mine}_default" "$job_container"
+
+echo "--- --job removes this job's stacks, at any age, and nothing else"
+EKKLESIA_CI_JOB_KEY=alpha bash scripts/ci-sweep.sh --job
+check '! project_exists "$mine"' "this job's containers, network, volume, and image are gone"
+check '! staging_exists "$mine"' "this job's staging directory on the Docker host is gone"
+check 'project_exists "$sibling"' "another job's stack in the same run is left alone"
+check 'project_exists "$foreign"' "a stack outside the CI prefix is left alone"
+check 'docker inspect "$job_container" >/dev/null 2>&1' \
+  "a job container connected to the stack's network is disconnected, never removed"
+
+echo "--- --job refuses to run outside CI, where it could remove a developer's own stacks"
+check '! env -u GITHUB_RUN_ID bash scripts/ci-sweep.sh --job >/dev/null 2>&1' \
+  "--job without GITHUB_RUN_ID fails"
+
+echo "--- --stale removes only CI stacks older than its threshold"
+bash scripts/ci-sweep.sh --stale
+check 'project_exists "$sibling"' "a young CI stack survives the default threshold"
+bash scripts/ci-sweep.sh --stale --max-age-seconds 0
+check '! project_exists "$sibling"' "a CI stack older than the threshold is removed"
+check '! staging_exists "$sibling"' "its staging directory too"
+check 'project_exists "$foreign"' "a stack outside the CI prefix is never removed, at any age"
+
+if ((failures > 0)); then
+  echo "test-ci-sweep: ${failures} check(s) failed." >&2
+  exit 1
+fi
+echo "CI sweep checks passed."
diff --git a/scripts/test-migrations-integration.sh b/scripts/test-migrations-integration.sh
index 29d4dd1..847caf0 100755
--- a/scripts/test-migrations-integration.sh
+++ b/scripts/test-migrations-integration.sh
@@ -9,6 +9,8 @@ cd "$repository_root"
 source "$repository_root/scripts/lib/compose-job-network.sh"
 # shellcheck source=scripts/lib/compose-diagnostics.sh
 source "$repository_root/scripts/lib/compose-diagnostics.sh"
+# shellcheck source=scripts/lib/ci-project.sh
+source "$repository_root/scripts/lib/ci-project.sh"
 
 command -v docker >/dev/null || {
   echo "Docker is required for the PostgreSQL migration integration suite." >&2
@@ -27,11 +29,9 @@ if ! compose_job_network_initialize; then
   exit 1
 fi
 
-# Unique per invocation, not only per run: several runs (and several jobs of one run) can share a
-# runner's Docker daemon at once, and the shell's PID is often identical across job containers.
-raw_project="ekklesia-migration-${GITHUB_RUN_ID:-local}-${GITHUB_RUN_ATTEMPT:-0}-${GITHUB_JOB:-job}-$$-${RANDOM}${RANDOM}"
-project="${raw_project//[^a-zA-Z0-9_-]/-}"
-project="${project,,}"
+# Unique per invocation, and findable by run and job if this script is killed before its trap runs
+# (scripts/lib/ci-project.sh, scripts/ci-sweep.sh).
+project="$(ci_project_name migration)"
 
 export POSTGRES_DB="ekklesia_migration_test"
 export POSTGRES_USER="ekklesia_migration_test"
diff --git a/tests/ci-scripts.test.ts b/tests/ci-scripts.test.ts
index 7203ada..e498d70 100644
--- a/tests/ci-scripts.test.ts
+++ b/tests/ci-scripts.test.ts
@@ -4,6 +4,7 @@ import path from "node:path";
 import { fileURLToPath } from "node:url";
 import { promisify } from "node:util";
 import { describe, expect, it } from "vitest";
+import { parse } from "yaml";
 
 /**
  * The scripts CI runs against a shared Docker daemon. Several runs, and several jobs of one run, can
@@ -59,21 +60,68 @@ describe("CI scripts on a shared Docker daemon", () => {
     }
   });
 
-  it("give every Compose project a name unique to the invocation, not only the run", async () => {
-    expect(await source("scripts/test-migrations-integration.sh")).toMatch(
-      /raw_project="ekklesia-migration-[^"\n]*\$\$-\$\{RANDOM\}\$\{RANDOM\}"/u,
+  it("name every stack through one helper: the reserved CI prefix, the job's key, and a unique suffix", async () => {
+    const helper = await source("scripts/lib/ci-project.sh");
+    // Run, attempt, job key, kind, then a per-invocation suffix: unique even when job containers
+    // share a PID, and findable later by run and job alone (scripts/ci-sweep.sh --job).
+    expect(helper).toContain(
+      "ekklesia-ci-${GITHUB_RUN_ID:-local}-${GITHUB_RUN_ATTEMPT:-0}-${EKKLESIA_CI_JOB_KEY:-${GITHUB_JOB:-local}}-",
     );
-    expect(await source("scripts/smoke-infrastructure.sh")).toMatch(
-      /raw_project="ekklesia-smoke-[^"\n]*\$\$-\$\{RANDOM\}\$\{RANDOM\}"/u,
-    );
-    const deploy = await source("scripts/smoke-deploy.sh");
-    expect(deploy).toContain('run_id="$(openssl rand -hex 4)"');
-    expect(deploy).toContain('project="ekklesia-deploy-smoke-${run_id}"');
+    expect(helper).toContain("$$-${RANDOM}${RANDOM}");
     for (const relativePath of ciScripts) {
-      expect(await source(relativePath), relativePath).toContain('--project-name "$project"');
+      const text = await source(relativePath);
+      expect(text, relativePath).toContain('source "$repository_root/scripts/lib/ci-project.sh"');
+      expect(text, relativePath).toMatch(/^project="\$\(ci_project_name [a-z"${}_-]+\)"$/mu);
+      expect(text, relativePath).not.toContain("raw_project=");
+      expect(text, relativePath).toContain('--project-name "$project"');
     }
   });
 
+  it("label everything the deploy smoke creates outside Compose, so a sweep can find it", async () => {
+    // Continuation lines joined, so each command is checked whole.
+    const deploy = (await source("scripts/smoke-deploy.sh")).replace(/\\\n\s*/gu, " ");
+    const creating = deploy
+      .split("\n")
+      .filter((line) => /\bdocker (?:run --detach|volume create|build)\b/u.test(line));
+    expect(creating.length).toBeGreaterThanOrEqual(4);
+    for (const line of creating) {
+      expect(line).toContain('--label "${EKKLESIA_CI_LABEL}=${project}"');
+    }
+  });
+
+  it("sweep stale stacks before, and this job's own stacks after, every job that starts any", async () => {
+    const workflow = parse(await source(".github/workflows/ci.yml")) as {
+      jobs: Record<
+        string,
+        { env?: Record<string, string>; steps: { if?: string; run?: string; name?: string }[] }
+      >;
+    };
+    const startsStacks =
+      /smoke-infrastructure\.sh|test:migrations:integration|smoke-deploy\.sh|docker build/u;
+    const jobs = Object.entries(workflow.jobs).filter(([, job]) =>
+      job.steps.some((step) => startsStacks.test(step.run ?? "")),
+    );
+    expect(jobs.map(([id]) => id).sort()).toEqual(
+      ["deploy-smoke", "image-build", "infrastructure-smoke", "migration-smoke"].sort(),
+    );
+    for (const [id, job] of jobs) {
+      expect(job.env?.EKKLESIA_CI_JOB_KEY, id).toBeTruthy();
+      const runs = job.steps.map((step) => step.run ?? "");
+      const firstStack = runs.findIndex((run) => startsStacks.test(run));
+      const stale = runs.findIndex((run) => run.includes("bash scripts/ci-sweep.sh --stale"));
+      const own = job.steps.findIndex(
+        (step) =>
+          step.if === "always()" && (step.run ?? "").includes("bash scripts/ci-sweep.sh --job"),
+      );
+      expect(stale, `${id}: stale sweep`).toBeGreaterThanOrEqual(0);
+      expect(stale, `${id}: stale sweep runs first`).toBeLessThan(firstStack);
+      expect(own, `${id}: its own cleanup, always`).toBeGreaterThan(firstStack);
+      expect(own, `${id}: cleanup is the last step`).toBe(job.steps.length - 1);
+    }
+    // One matrix leg's cleanup must never remove the other leg's running stack.
+    expect(workflow.jobs["deploy-smoke"]?.env?.EKKLESIA_CI_JOB_KEY).toContain("matrix.topology");
+  });
+
   it("choose the deploy smoke's edge subnet from those not in use, and choose again on a race", async () => {
     const deploy = await source("scripts/smoke-deploy.sh");
     expect(deploy).not.toMatch(/^octet=\$\(\(RANDOM/mu);