diff --git a/.github/workflows/build-image.yml b/.github/workflows/build-image.yml
new file mode 100644
index 0000000000..d7b7906271
--- /dev/null
+++ b/.github/workflows/build-image.yml
@@ -0,0 +1,35 @@
+name: Build CI image
+
+# Called by prod.yml before the render jobs, so the image always exists and
+# matches the current Dockerfile/lock file. Unchanged layers come from the
+# registry cache, so a no-op rebuild is quick.
+on:
+  workflow_call:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push CI image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: docker/Dockerfile.ci
+          push: true
+          tags: ghcr.io/${{ github.repository }}:latest
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository }}:latest
+          cache-to: type=inline
diff --git a/.github/workflows/prod.yml b/.github/workflows/prod.yml
index 8a03c421d5..9865fb98b1 100644
--- a/.github/workflows/prod.yml
+++ b/.github/workflows/prod.yml
@@ -4,67 +4,226 @@ on:
   push:
     branches:
       - main
-      - dev
+      - parallel
 
 jobs:
-  pages:
-    name: Render-Blog
+
+  # ── 0. CI image ─────────────────────────────────────────────────────────────
+  image:
+    name: Build CI image
+    if: ${{ !github.event.pull_request.head.repo.fork }}
+    permissions:
+      contents: read
+      packages: write
+    uses: ./.github/workflows/build-image.yml
+
+  # ── 1. Parallel chunk rendering ─────────────────────────────────────────────
+  # Each chunk runs independently: installs deps, executes Python in its .qmd
+  # files, and uploads the resulting _freeze/ entries as an artifact.
+  # All 43 files from _quarto-prod.yml are covered across the 7 chunks.
+  render-chunk:
+    name: Render (${{ matrix.chunk }})
     runs-on: ubuntu-latest
+    needs: image
     if: ${{ !github.event.pull_request.head.repo.fork }}
-    steps:
+    container:
+      image: ghcr.io/${{ github.repository }}:latest
+      credentials:
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+    strategy:
+      matrix:
+        include:
+          - chunk: light
+            files: >-
+              index.qmd
+              404.qmd
+              content/getting-started/index.qmd
+              content/getting-started/01_environment.qmd
+              content/getting-started/02_data_analysis.qmd
+              content/getting-started/03_revisions.qmd
+              content/annexes/about.qmd
+              content/annexes/evaluation.qmd
+              content/annexes/corrections.qmd
+              content/git/index.qmd
+              content/git/introgit.qmd
+              content/git/exogit.qmd
+
+          - chunk: manip-1
+            files: >-
+              content/manipulation/index.qmd
+              content/manipulation/01_numpy.qmd
+              content/manipulation/02_pandas_intro.qmd
+              content/manipulation/02_pandas_joins.qmd
+              content/manipulation/02_pandas_stats.qmd
+              content/manipulation/02_pandas_beyond.qmd
+              content/manipulation/02a_pandas_tutorial.qmd
+              content/manipulation/02b_pandas_TP.qmd
+
+          - chunk: manip-2
+            files: >-
+              content/manipulation/03_geopandas_intro.qmd
+              content/manipulation/03_geopandas_tutorial.qmd
+              content/manipulation/03_geopandas_TP.qmd
+              content/manipulation/04a_webscraping_TP.qmd
+              content/manipulation/04c_API_TP.qmd
+              content/manipulation/04b_regex_TP.qmd
+              content/manipulation/05_parquet_s3.qmd
+
+          - chunk: visu
+            files: >-
+              content/visualisation/index.qmd
+              content/visualisation/matplotlib.qmd
+              content/visualisation/maps.qmd
+
+          - chunk: model-1
+            files: >-
+              content/modelisation/index.qmd
+              content/modelisation/0_preprocessing.qmd
+              content/modelisation/1_modelevaluation.qmd
+              content/modelisation/2_classification.qmd
 
+          - chunk: model-2
+            files: >-
+              content/modelisation/3_regression.qmd
+              content/modelisation/4_featureselection.qmd
+              content/modelisation/5_clustering.qmd
+              content/modelisation/6_pipeline.qmd
+              content/modelisation/7_mlapi.qmd
+
+          - chunk: nlp
+            files: >-
+              content/NLP/index.qmd
+              content/NLP/01_intro.qmd
+              content/NLP/02_exoclean.qmd
+              content/NLP/03_embedding.qmd
+
+    steps:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.ref }}
-          repository: ${{github.event.pull_request.head.repo.full_name}}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
 
-      - name: Configure safe.directory  # Workaround for actions/checkout#760
+      - name: Configure safe.directory
         run: git config --global --add safe.directory /__w/python-datascientist/python-datascientist
 
-      - name: Install system dependencies
+      - name: Restore environment
+        run: uv sync
+
+      - name: Install SpaCy corpus and check Quarto version
         run: |
-          sudo ./build/requirements.sh
+          uv run spacy download en_core_web_sm
+          uv run quarto --version
 
-      - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@v7
+      - name: Prepare config
+        run: |
+          rm _quarto.yml
+          cp _quarto-prod.yml _quarto.yml
+
+      - name: Prepare environment metadata
+        env:
+          TOKEN_API_INSEE: ${{ secrets.TOKEN_API_INSEE }}
+        run: uv run build/append-environment/append_environment.py
+
+      - name: Render chunk files
+        env:
+          TOKEN_API_INSEE: ${{ secrets.TOKEN_API_INSEE }}
+        run: |
+          for file in ${{ matrix.files }}; do
+            echo "::group::Rendering $file"
+            uv run quarto render "$file" --profile fr
+            echo "::endgroup::"
+          done
+
+      # _freeze/ entries are the execution results Quarto needs to skip
+      # re-execution in the assembly step. Profile is not part of the freeze
+      # path, so fr freeze entries are reused by the en render as well.
+      - name: Upload freeze artifacts
+        uses: actions/upload-artifact@v4
         with:
-          version: "latest"
+          name: freeze-chunk-${{ matrix.chunk }}
+          path: _freeze
+          if-no-files-found: warn
+
+  # ── 2. Site assembly and publication ────────────────────────────────────────
+  # Downloads all freeze artifacts, merges them, then runs the two-profile
+  # site render without re-executing any Python.
+  # Quarto has no --freeze CLI flag: `freeze: true` is set in _quarto.yml
+  # instead. Unlike `freeze: auto`, it reuses _freeze/ regardless of the
+  # source-file hash, which is required here because append_environment.py
+  # and sidebar.py both modify the .qmd files.
+  pages:
+    name: Assemble and publish
+    runs-on: ubuntu-latest
+    needs: render-chunk
+    if: ${{ !github.event.pull_request.head.repo.fork }}
+    container:
+      image: ghcr.io/${{ github.repository }}:latest
+      credentials:
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+
+      - name: Configure safe.directory
+        run: git config --global --add safe.directory /__w/python-datascientist/python-datascientist
 
       - name: Restore environment
         run: uv sync
 
-      # Step 3: Set up Quarto
-      - name: Set up quarto
-        uses: quarto-dev/quarto-actions/setup@v2
-        with:
-          version: 1.10.18
-
-      - name: Install SpaCy corpus and check quarto version
+      - name: Install SpaCy corpus and check Quarto version
         run: |
           uv run spacy download en_core_web_sm
           uv run quarto --version
 
-      - name: Prepare directory
+      - name: Prepare config
         run: |
           rm _quarto.yml
           cp _quarto-prod.yml _quarto.yml
+          sed -i 's/^  freeze: auto$/  freeze: true/' _quarto.yml
+          grep -q '^  freeze: true$' _quarto.yml
 
-      - name: Render website
+      - name: Prepare environment metadata
         env:
           TOKEN_API_INSEE: ${{ secrets.TOKEN_API_INSEE }}
-        run: |
-          uv run build/append-environment/append_environment.py
-          uv run quarto render --profile fr --to all
-          uv run build/sidebar.py --to english
-          uv run quarto render --profile en --to all
-          uv run build/sidebar.py --to french
+        run: uv run build/append-environment/append_environment.py
+
+      # upload-artifact stores the *contents* of _freeze/ (no _freeze/ prefix),
+      # so the artifacts are merged straight into _freeze/.
+      - name: Download all freeze artifacts
+        uses: actions/download-artifact@v4
+        with:
+          pattern: freeze-chunk-*
+          path: _freeze
+          merge-multiple: true
+
+      - name: Render website (fr)
+        env:
+          TOKEN_API_INSEE: ${{ secrets.TOKEN_API_INSEE }}
+        run: uv run quarto render --profile fr --to all
+
+      - name: Switch sidebar to English
+        run: uv run build/sidebar.py --to english
+
+      - name: Render website (en)
+        env:
+          TOKEN_API_INSEE: ${{ secrets.TOKEN_API_INSEE }}
+        run: uv run quarto render --profile en --to all
+
+      - name: Reset sidebar to French
+        run: uv run build/sidebar.py --to french
+
       - name: Archive build as artifacts
         uses: actions/upload-artifact@v4
         with:
           name: sitedir
-          path: |
-            _site
+          path: _site
+
       - name: Publish to Pages
         if: github.ref == 'refs/heads/main'
         run: |
@@ -72,24 +231,23 @@ jobs:
           git config --global user.name "Quarto GHA Workflow Runner"
           quarto publish gh-pages . --no-render --no-browser
 
+  # ── 3. Exercises and corrections (unchanged, run in parallel with above) ────
   enonces:
     name: Render exercises
     runs-on: ubuntu-latest
     if: ${{ !github.event.pull_request.head.repo.fork }}
     steps:
-
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.ref }}
           repository: ${{github.event.pull_request.head.repo.full_name}}
 
-      - name: Configure safe.directory  # Workaround for actions/checkout#760
+      - name: Configure safe.directory
         run: git config --global --add safe.directory /__w/python-datascientist/python-datascientist
 
       - name: Install system dependencies
-        run: |
-          sudo ./build/requirements.sh
+        run: sudo ./build/requirements.sh
 
       - name: Install the latest version of uv
         uses: astral-sh/setup-uv@v7
@@ -99,7 +257,6 @@ jobs:
       - name: Restore environment
         run: uv sync
 
-      # Step 3: Set up Quarto
       - name: Set up quarto
         uses: quarto-dev/quarto-actions/setup@v2
         with:
@@ -110,7 +267,6 @@ jobs:
           uv run spacy download en_core_web_sm
           uv run quarto --version
 
-          
       - name: Build and push notebooks
         uses: linogaliana/python-datascientist-actions@main
         with:
@@ -124,19 +280,17 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{ !github.event.pull_request.head.repo.fork }}
     steps:
-
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.ref }}
           repository: ${{github.event.pull_request.head.repo.full_name}}
 
-      - name: Configure safe.directory  # Workaround for actions/checkout#760
+      - name: Configure safe.directory
         run: git config --global --add safe.directory /__w/python-datascientist/python-datascientist
 
       - name: Install system dependencies
-        run: |
-          sudo ./build/requirements.sh
+        run: sudo ./build/requirements.sh
 
       - name: Install the latest version of uv
         uses: astral-sh/setup-uv@v7
@@ -146,7 +300,6 @@ jobs:
       - name: Restore environment
         run: uv sync
 
-      # Step 3: Set up Quarto
       - name: Set up quarto
         uses: quarto-dev/quarto-actions/setup@v2
         with:
@@ -157,7 +310,6 @@ jobs:
           uv run spacy download en_core_web_sm
           uv run quarto --version
 
-          
       - name: Build and push notebooks
         uses: linogaliana/python-datascientist-actions-corrections@main
         with:
@@ -166,5 +318,3 @@ jobs:
         env:
           TOKEN_API_INSEE: ${{ secrets.TOKEN_API_INSEE }}
           API_TOKEN_GITHUB: ${{ secrets.API_TOKEN_GITHUB }}
-
-
diff --git a/docker/Dockerfile.ci b/docker/Dockerfile.ci
new file mode 100644
index 0000000000..c161a35e2a
--- /dev/null
+++ b/docker/Dockerfile.ci
@@ -0,0 +1,43 @@
+FROM ubuntu:24.04
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Mirror build/requirements.sh + add curl for uv install
+RUN apt-get update && apt-get install -y \
+    graphviz wget curl git \
+    build-essential libmagic-dev libgdal-dev \
+    imagemagick && \
+    rm -rf /var/lib/apt/lists/*
+
+# Google Chrome for the selenium chapter (04a_webscraping_TP). The notebook
+# installs it with `!sudo apt-get`, which fails here: no sudo in the container.
+RUN wget -q https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb -O /tmp/chrome.deb && \
+    apt-get update && apt-get install -y /tmp/chrome.deb && \
+    rm /tmp/chrome.deb && rm -rf /var/lib/apt/lists/*
+
+# uv manages Python 3.13 itself (Ubuntu 24.04 ships 3.12)
+RUN curl -LsSf https://astral.sh/uv/install.sh | sh
+ENV PATH="/root/.local/bin:$PATH"
+
+# GitHub container jobs override HOME (/github/home), so keep uv's cache and
+# managed Python at fixed paths instead of under ~ to reuse them at run time.
+ENV UV_CACHE_DIR=/opt/uv/cache \
+    UV_PYTHON_INSTALL_DIR=/opt/uv/python \
+    UV_LINK_MODE=copy
+
+# Quarto
+ARG QUARTO_VERSION=1.10.18
+RUN wget -q "https://github.com/quarto-dev/quarto-cli/releases/download/v${QUARTO_VERSION}/quarto-${QUARTO_VERSION}-linux-amd64.tar.gz" && \
+    tar xzf "quarto-${QUARTO_VERSION}-linux-amd64.tar.gz" && \
+    mv "quarto-${QUARTO_VERSION}" /opt/quarto && \
+    ln -s /opt/quarto/bin/quarto /usr/local/bin/quarto && \
+    rm "quarto-${QUARTO_VERSION}-linux-amd64.tar.gz"
+
+# Pre-populate the uv download cache from the lock file.
+# The cache lands in /root/.cache/uv/ and persists in the image layers.
+# CI jobs that run uv sync will install from this cache (no PyPI download).
+WORKDIR /tmp/build
+COPY pyproject.toml uv.lock ./
+RUN uv sync --frozen
+
+WORKDIR /