diff --git a/.github/RUNNER_SETUP.md b/.github/RUNNER_SETUP.md
index 400e3f4..2ae5040 100644
--- a/.github/RUNNER_SETUP.md
+++ b/.github/RUNNER_SETUP.md
@@ -1,19 +1,33 @@
-# Self-hosted runner setup (macOS arm64)
+# Self-hosted runner setup (Debian container)
 
 This repo is public, so only run the runner for trusted workflows. `ci.yml` has no `pull_request` trigger on purpose: a fork PR can edit the workflow and run on this machine.
 
-1. Repo → Settings → Actions → Runners → **New self-hosted runner** → macOS / ARM64.
-   Follow the download and `./config.sh --url ... --token ...` steps in `~/actions-runner`.
-   Keep the default labels (`self-hosted`, `macOS`, `ARM64`).
-2. Install as a launchd service: `./svc.sh install && ./svc.sh start`.
-3. The service does not load shell profiles. Add the tool directories to `~/actions-runner/.path`
-   (one `PATH` line, then `./svc.sh stop && ./svc.sh start`):
+The runner is the `myoung34/github-runner:debian-bookworm` image. Jobs use `runs-on: [self-hosted, linux]`, which matches the image's default `self-hosted`, `Linux` and `X64`/`ARM64` labels.
+The image has no ruff, uv, gitleaks or actionlint, so each job installs what it needs with `.github/scripts/setup-tools.sh`.
+The script downloads pinned releases, verifies their SHA-256 checksums, caches them under `$RUNNER_TOOL_CACHE`, and adds them to `PATH`.
+To bump a tool, change the version at the top of the script.
+The script needs `curl`, `tar`, `sha256sum` and `install`, which the image provides.
 
-   ```
-   /Users/<you>/.local/bin:/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin
-   ```
+## docker-compose
 
-4. Install the tools the workflow calls directly: `brew install gitleaks actionlint jq`
-   (`uv` provides `uvx ruff` and `uvx pip-audit`).
-5. Repo → Settings → Actions → General → Fork pull request workflows →
-   **Require approval for all outside collaborators**.
+```yaml
+services:
+  github-runner:
+    image: myoung34/github-runner:debian-bookworm
+    restart: always
+    environment:
+      REPO_URL: "https://github.com/nprasad2077/MNIST"
+      RUNNER_TOKEN: "<registration token>" # Settings → Actions → Runners → New self-hosted runner
+      RUNNER_NAME: "coolify-debian-runner"
+      RUNNER_WORKDIR: "/tmp/runner/work"
+    # No docker.sock mount: the jobs don't use Docker, and the socket gives every job root on the host.
+```
+
+- The registration token expires after about an hour. Keep it out of git; set it in Coolify's environment variables, not in this file.
+- The container filesystem is disposable. When the container is recreated, the next run downloads the tools again.
+
+## Repo setting
+
+Settings → Actions → General → Fork pull request workflows → **Require approval for all outside collaborators**.
+
+Check the container with `docker exec <container> bash -c 'cd "$(mktemp -d)" && curl -sSfL https://raw.githubusercontent.com/nprasad2077/MNIST/dev/.github/scripts/setup-tools.sh | bash -s uv gitleaks actionlint'`.
diff --git a/.github/scripts/setup-tools.sh b/.github/scripts/setup-tools.sh
new file mode 100644
index 0000000..4bef1fe
--- /dev/null
+++ b/.github/scripts/setup-tools.sh
@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+# Install pinned CI tools (Linux x64/arm64) on the self-hosted runner and put them on PATH.
+# Usage: setup-tools.sh [uv] [gitleaks] [actionlint]
+# Needs only curl, tar and sha256sum. Downloads are verified against the published checksums.
+set -euo pipefail
+
+UV_VERSION=0.10.7
+GITLEAKS_VERSION=8.30.1
+ACTIONLINT_VERSION=1.7.12
+
+# Versions are part of the path, so bumping a pin installs into a fresh directory.
+BIN="${RUNNER_TOOL_CACHE:-$HOME/.cache}/mnist-ci/uv${UV_VERSION}-gl${GITLEAKS_VERSION}-al${ACTIONLINT_VERSION}/bin"
+
+case "$(uname -m)" in
+  x86_64) UV_ARCH=x86_64 GL_ARCH=x64 AL_ARCH=amd64 ;;
+  aarch64 | arm64) UV_ARCH=aarch64 GL_ARCH=arm64 AL_ARCH=arm64 ;;
+  *) echo "::error::unsupported architecture $(uname -m)"; exit 1 ;;
+esac
+
+# Download <base>/<archive>, verify it against <base>/<sums>, extract <members...> into $BIN.
+install_tarball() {
+  local base=$1 archive=$2 sums=$3 strip=$4
+  shift 4
+  local tmp
+  tmp=$(mktemp -d)
+  curl -sSfL --retry 3 -o "$tmp/$archive" "$base/$archive"
+  curl -sSfL --retry 3 -o "$tmp/$sums" "$base/$sums"
+  (cd "$tmp" && grep -F "  $archive" "$sums" | sha256sum -c -)
+  tar -xzf "$tmp/$archive" -C "$tmp"
+  mkdir -p "$BIN"
+  for member in "$@"; do
+    install -m 0755 "$tmp/${strip}${member}" "$BIN/$member"
+  done
+  rm -rf "$tmp"
+}
+
+for tool in "$@"; do
+  if [ -x "$BIN/$tool" ]; then
+    continue
+  fi
+  case "$tool" in
+    uv)
+      triple="uv-${UV_ARCH}-unknown-linux-gnu"
+      # uv publishes one .sha256 per archive; reuse the same verification path.
+      base="https://github.com/astral-sh/uv/releases/download/${UV_VERSION}"
+      tmp=$(mktemp -d)
+      curl -sSfL --retry 3 -o "$tmp/$triple.tar.gz" "$base/$triple.tar.gz"
+      curl -sSfL --retry 3 -o "$tmp/$triple.tar.gz.sha256" "$base/$triple.tar.gz.sha256"
+      (cd "$tmp" && sha256sum -c "$triple.tar.gz.sha256")
+      tar -xzf "$tmp/$triple.tar.gz" -C "$tmp"
+      mkdir -p "$BIN"
+      install -m 0755 "$tmp/$triple/uv" "$tmp/$triple/uvx" "$BIN/"
+      rm -rf "$tmp"
+      ;;
+    gitleaks)
+      install_tarball "https://github.com/gitleaks/gitleaks/releases/download/v${GITLEAKS_VERSION}" \
+        "gitleaks_${GITLEAKS_VERSION}_linux_${GL_ARCH}.tar.gz" "gitleaks_${GITLEAKS_VERSION}_checksums.txt" "" gitleaks
+      ;;
+    actionlint)
+      install_tarball "https://github.com/rhysd/actionlint/releases/download/v${ACTIONLINT_VERSION}" \
+        "actionlint_${ACTIONLINT_VERSION}_linux_${AL_ARCH}.tar.gz" "actionlint_${ACTIONLINT_VERSION}_checksums.txt" "" actionlint
+      ;;
+    *) echo "::error::unknown tool: $tool"; exit 1 ;;
+  esac
+done
+
+if [ -n "${GITHUB_PATH:-}" ]; then
+  echo "$BIN" >> "$GITHUB_PATH"
+fi
+export PATH="$BIN:$PATH"
+for tool in "$@"; do
+  case "$tool" in
+    gitleaks) "$tool" version ;;
+    actionlint) "$tool" -version | head -1 ;;
+    *) "$tool" --version ;;
+  esac
+done
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d303430..706bf05 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,65 +19,76 @@ env:
 
 jobs:
   lint-notebooks:
-    runs-on: self-hosted
+    runs-on: [self-hosted, linux]
     steps:
       - uses: actions/checkout@v4
         with:
           persist-credentials: false
+      - run: bash .github/scripts/setup-tools.sh uv
       - run: uvx "ruff@${RUFF_VERSION}" check --output-format=github notebooks/
 
   format-notebooks:
-    runs-on: self-hosted
+    runs-on: [self-hosted, linux]
     continue-on-error: true # advisory: notebooks were never formatted
     steps:
       - uses: actions/checkout@v4
         with:
           persist-credentials: false
+      - run: bash .github/scripts/setup-tools.sh uv
       - run: uvx "ruff@${RUFF_VERSION}" format --check notebooks/
 
   secret-scan:
-    runs-on: self-hosted
+    runs-on: [self-hosted, linux]
     steps:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
           persist-credentials: false
+      - run: bash .github/scripts/setup-tools.sh gitleaks
       - run: gitleaks detect --source . --redact --verbose
 
   dep-audit:
-    runs-on: self-hosted
+    runs-on: [self-hosted, linux]
     continue-on-error: true # advisory: pins are stale; Dependabot tracks bumps
     steps:
       - uses: actions/checkout@v4
         with:
           persist-credentials: false
+      - run: bash .github/scripts/setup-tools.sh uv
       # Audit the pins only; installing requirements.txt fails on pywinpty.
       - run: uvx pip-audit -r requirements.txt --no-deps --disable-pip
 
   workflow-lint:
-    runs-on: self-hosted
+    runs-on: [self-hosted, linux]
     steps:
       - uses: actions/checkout@v4
         with:
           persist-credentials: false
+      - run: bash .github/scripts/setup-tools.sh actionlint
       - run: actionlint
 
   notebook-hygiene:
-    runs-on: self-hosted
+    runs-on: [self-hosted, linux]
     steps:
       - uses: actions/checkout@v4
         with:
           persist-credentials: false
+      - run: bash .github/scripts/setup-tools.sh uv
       - run: uv run --python 3.11 --no-project python .github/scripts/notebook_hygiene.py
 
   summary:
     if: always()
     needs: [lint-notebooks, format-notebooks, secret-scan, dep-audit, workflow-lint, notebook-hygiene]
-    runs-on: self-hosted
+    runs-on: [self-hosted, linux]
     steps:
       - name: Write job summary
         env:
-          RESULTS: ${{ toJSON(needs) }}
+          LINT: ${{ needs.lint-notebooks.result }}
+          FORMAT: ${{ needs.format-notebooks.result }}
+          SECRETS: ${{ needs.secret-scan.result }}
+          AUDIT: ${{ needs.dep-audit.result }}
+          WORKFLOW: ${{ needs.workflow-lint.result }}
+          HYGIENE: ${{ needs.notebook-hygiene.result }}
           EVENT: ${{ github.event_name }}
           REF_NAME: ${{ github.ref_name }}
           ACTOR: ${{ github.actor }}
@@ -88,7 +99,12 @@ jobs:
             echo
             echo "| Job | Result |"
             echo "|---|---|"
-            echo "$RESULTS" | jq -r 'to_entries[] | "| \(.key) | \(.value.result) |"'
+            echo "| lint-notebooks | $LINT |"
+            echo "| format-notebooks | $FORMAT |"
+            echo "| secret-scan | $SECRETS |"
+            echo "| dep-audit | $AUDIT |"
+            echo "| workflow-lint | $WORKFLOW |"
+            echo "| notebook-hygiene | $HYGIENE |"
             echo
             echo "- **Trigger:** $EVENT"
             echo "- **Ref:** $REF_NAME @ ${GITHUB_SHA::7}"