diff --git a/.github/workflows/core.yml b/.github/workflows/core.yml
index eddaada7c7..995cbf71e6 100644
--- a/.github/workflows/core.yml
+++ b/.github/workflows/core.yml
@@ -108,6 +108,18 @@ jobs:
         # Make sure the current directory is empty
         run: find . -delete
 
+      # Check that the Dockerfile is using the latest Ubuntu version.
+      # The version is hardcoded into the Dockerfile so that the OS
+      # for each release is fixed.
+      - name: Check Dockerfile Ubuntu version
+        run: |
+          latest_version=$(grep "VERSION_ID=" /etc/os-release | cut -d '"' -f 2)
+          docker_version=$(grep FROM docker/Dockerfile.vanilla | cut -d ':' -f 2)
+          if [[ "$docker_version" != "$latest_version" ]]; then
+            echo "Ubuntu version ${docker_version} in Dockerfile is out of date with latest version ${latest_version}"
+            exit 1
+          fi
+
       # Use a different mirror to fetch apt packages from to get around
       # temporary outage.
       # (https://askubuntu.com/questions/1549622/problem-with-archive-ubuntu-com-most-of-the-servers-are-not-responding)
diff --git a/.github/workflows/docker.yml b/.github/workflows/docker.yml
index 934b3e1193..33d2a4dd68 100644
--- a/.github/workflows/docker.yml
+++ b/.github/workflows/docker.yml
@@ -6,6 +6,14 @@ on:
       tag:
         description: Docker image tag
         type: string
+      build_dev:
+        description: Whether to build a developer vanilla-default container
+        type: boolean
+        default: false
+      branch:
+        description: Which Firedrake branch to build the containers from
+        type: string
+        default: "release"
     secrets:
       DOCKERHUB_USER:
         required: true
@@ -16,6 +24,14 @@ on:
       tag:
         description: Docker image tag
         type: string
+      build_dev:
+        description: Whether to build a developer vanilla-default container
+        type: boolean
+        default: false
+      branch:
+        description: Which Firedrake branch to build the containers from
+        type: string
+        default: "release"
 
 jobs:
   # Firedrake only
@@ -25,11 +41,18 @@ jobs:
       matrix:
         os: [Linux, macOS]
         arch: [default, complex]
-        include:
+        platform: [linux/amd64, linux/arm64]
+        # Cannot use inputs in exclude clauses, so add a dummy matrix dim
+        build_dev:
+          - ${{ inputs.build_dev }}
+        # exclude incompatible os+platform, and only build linux dev containers
+        exclude:
           - os: Linux
+            platform: linux/arm64
+          - os: macOS
             platform: linux/amd64
           - os: macOS
-            platform: linux/arm64
+            build_dev: true
     uses: ./.github/workflows/docker_build.yml
     with:
       os: ${{ matrix.os }}
@@ -37,6 +60,7 @@ jobs:
       arch: ${{ matrix.arch }}
       target: firedrake-vanilla-${{ matrix.arch }}
       tag: ${{ inputs.tag }}
+      branch: ${{ inputs.branch }}
       dockerfile: docker/Dockerfile.vanilla
     secrets: inherit
 
@@ -50,10 +74,12 @@ jobs:
     with:
       target: firedrake-vanilla-${{ matrix.arch }}
       tag: ${{ inputs.tag }}
+      tag_latest: ${{ ! inputs.build_dev }}
     secrets: inherit
 
   # Firedrake and friends
   docker_build_firedrake:
+    if: ${{ ! inputs.build_dev }}
     needs: docker_merge_vanilla
     uses: ./.github/workflows/docker_build.yml
     # Only build the 'firedrake' container for 'linux/amd64' because
@@ -69,15 +95,18 @@ jobs:
     secrets: inherit
 
   docker_merge_firedrake:
+    if: ${{ ! inputs.build_dev }}
     uses: ./.github/workflows/docker_merge.yml
     needs: docker_build_firedrake
     with:
       target: firedrake
       tag: ${{ inputs.tag }}
+      tag_latest: ${{ ! inputs.build_dev }}
     secrets: inherit
 
   # Firedrake with Jupyter notebooks
   docker_build_jupyter:
+    if: ${{ ! inputs.build_dev }}
     needs: docker_merge_firedrake
     uses: ./.github/workflows/docker_build.yml
     with:
@@ -89,9 +118,11 @@ jobs:
     secrets: inherit
 
   docker_merge_jupyter:
+    if: ${{ ! inputs.build_dev }}
     uses: ./.github/workflows/docker_merge.yml
     needs: docker_build_jupyter
     with:
       target: firedrake-jupyter
       tag: ${{ inputs.tag }}
+      tag_latest: ${{ ! inputs.build_dev }}
     secrets: inherit
diff --git a/.github/workflows/docker_build.yml b/.github/workflows/docker_build.yml
index ce1be1396e..005237b3a5 100644
--- a/.github/workflows/docker_build.yml
+++ b/.github/workflows/docker_build.yml
@@ -32,6 +32,12 @@ on:
         description: 'Firedrake arch to build'
         required: false
         type: string
+        default: 'default'
+      branch:
+        description: 'Firedrake branch to build'
+        required: false
+        type: string
+        default: 'release'
     secrets:
       # Docker login information
       DOCKERHUB_USER:
@@ -77,6 +83,7 @@ jobs:
           file: ${{ inputs.dockerfile }}
           build-args: |
             ARCH=${{ inputs.arch }}
+            BRANCH=${{ inputs.branch }}
           outputs: type=image,name=firedrakeproject/${{ inputs.target }},push-by-digest=true,name-canonical=true,push=true
 
       - name: Export digest
diff --git a/.github/workflows/docker_merge.yml b/.github/workflows/docker_merge.yml
index b7221fb10c..34414a638e 100644
--- a/.github/workflows/docker_merge.yml
+++ b/.github/workflows/docker_merge.yml
@@ -14,6 +14,10 @@ on:
         description: Docker image tag
         required: true
         type: string
+      tag_latest:
+        description: Whether to add additional 'latest' tag to containers
+        default: false
+        type: boolean
     secrets:
       # Docker login information
       DOCKERHUB_USER:
@@ -50,10 +54,16 @@ jobs:
       - name: Merge and push the per-platform images
         working-directory: ${{ runner.temp }}/digests
         run: |
-          docker buildx imagetools create \
-            -t firedrakeproject/${{ inputs.target }}:${{ inputs.tag }} \
-            -t firedrakeproject/${{ inputs.target }}:latest \
-            $(printf 'firedrakeproject/${{ inputs.target }}@sha256:%s ' *)
+          if [[ "${{ inputs.tag_latest }}" == "true" ]]; then
+            docker buildx imagetools create \
+              -t firedrakeproject/${{ inputs.target }}:${{ inputs.tag }} \
+              -t firedrakeproject/${{ inputs.target }}:latest \
+              $(printf "firedrakeproject/${{ inputs.target }}@sha256:%s " *)
+          else
+            docker buildx imagetools create \
+              -t firedrakeproject/${{ inputs.target }}:${{ inputs.tag }} \
+              $(printf "firedrakeproject/${{ inputs.target }}@sha256:%s " *)
+          fi
 
       - name: Inspect image
         run: |
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index a1430b57e7..9e59221826 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -13,3 +13,12 @@ jobs:
       # Only run macOS tests if the PR is labelled 'macOS'
       test_macos: ${{ contains(github.event.pull_request.labels.*.name, 'macOS') }}
     secrets: inherit
+
+  docker:
+    name: Build dev Docker containers
+    uses: ./.github/workflows/docker.yml
+    with:
+      tag: dev-main
+      branch: main
+      build_dev: true
+    secrets: inherit
diff --git a/.github/workflows/push.yml b/.github/workflows/push.yml
index 45573bd8f5..19d3b73c37 100644
--- a/.github/workflows/push.yml
+++ b/.github/workflows/push.yml
@@ -15,3 +15,12 @@ jobs:
       test_macos: true
       deploy_website: true
     secrets: inherit
+
+  docker:
+    name: Build developer Docker containers
+    uses: ./.github/workflows/docker.yml
+    with:
+      tag: dev-${{ github.ref_name }}
+      branch: ${{ github.ref_name }}
+      build_dev: true
+    secrets: inherit
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 37a02ef9c3..04dab5b8ee 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -19,4 +19,6 @@ jobs:
     uses: ./.github/workflows/docker.yml
     with:
       tag: ${{ github.ref_name }}
+      branch: ${{ github.ref_name }}
+      build_dev: false
     secrets: inherit
diff --git a/docker/Dockerfile.vanilla b/docker/Dockerfile.vanilla
index 58c2cb92e1..ff601ed4f5 100644
--- a/docker/Dockerfile.vanilla
+++ b/docker/Dockerfile.vanilla
@@ -1,10 +1,70 @@
 # Dockerfile for a plain Firedrake suitable for testing Firedrake components and applications
+# Firedrake is installed as a system package so doesn't require activating a venv.
+#
+# Three types of build are available:
+# 1. A "release" build for a specific version (e.g. 2025.4.2).
+# 2. A "release" build with the "release" branch at the latest commit.
+# 3. A "developer" build with the "main" branch at the latest commit
+#
+# A release build will install:
+#  - Firedrake in editable mode from the specified release tag or branch.
+#  - PETSc and SLEPc from the corresponding release (specified by firedrake-configure).
+# A developer build will install:
+#  - Firedrake in editable mode from the main branch.
+#  - PETSc and SLEPc from the main branch.
+#  - Python dependencies in editable mode that firedrake/main requires the latest main branch for (pyadjoint, ufl, etc).
+#
+# The two main command line arguments are:
+#
+# ARCH:
+#     The `--arch` argument to firedrake-configure, e.g. default, complex
+#
+# BRANCH:
+#     Whether to build a release version of Firedrake.
+#     Options:
+#      - "release"        Build from the latest release branch.
+#      - <release tag>    Build a specific release (e.g. 2025.4.2).
+#      - "main"           Build a developer install from the latest main branch.
+#
+# Extra apt packages and PETSc configure arguments can also be
+# provided with the following command line arguments:
+#
+# APT_EXTRA_PACKAGES:
+#     Extra packages to pass to `apt install`
+#
+# PETSC_EXTRA_ARGS:
+#     Extra arguments to pass to PETSc's `configure` script
+#
+# Example usage for a specific firedrake release with complex scalars:
+#  $ docker build \
+#     --file=Dockerfile.vanilla \
+#     --tag=firedrake:2025.4.2-complex \
+#     --build-arg ARCH=complex \
+#     --build-arg BRANCH=2025.4.2
+#
+# Example usage for building from firedrake main with real scalars, ml installed with PETSc, and valgrind installed with apt:
+#  $ docker build \
+#     --file=Dockerfile.vanilla \
+#     --tag=firedrake:main-latest \
+#     --build-arg ARCH=default \
+#     --build-arg BRANCH=main \
+#     --build-arg PETSC_EXTRA_ARGS="--download-ml" \
+#     --build-arg APT_EXTRA_PACKAGES="valgrind"
 
-FROM ubuntu:latest
+FROM ubuntu:24.04
 
 # Firedrake arch to build
 ARG ARCH="default"
 
+# Is this a release build?
+ARG BRANCH="release"
+
+# Extra system packages
+ARG APT_EXTRA_PACKAGES=
+
+# Extra PETSc configuration options
+ARG PETSC_EXTRA_ARGS=
+
 # Set '-o pipefail' to avoid linter error (https://github.com/hadolint/hadolint/wiki/DL4006)
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 
@@ -18,41 +78,57 @@ ENV TZ=Europe/London
 
 # Install 'parallel' because it is needed by 'firedrake-run-split-tests'
 RUN apt-get update \
-    && apt-get -y install curl parallel python3 python3-pip python3-venv sudo \
+    && apt-get -y install curl parallel python3 python3-pip python3-venv sudo graphviz graphviz-dev \
     && rm -rf /var/lib/apt/lists/*
 
 # Allow pip to install into system package locations without prompting
 ENV PIP_BREAK_SYSTEM_PACKAGES=1
 ENV OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1
 
-# Download firedrake-configure
-RUN curl -O --output-dir /opt https://raw.githubusercontent.com/firedrakeproject/firedrake/release/scripts/firedrake-configure
+# Where to download firedrake-configure from
+RUN curl -O --output-dir /opt https://raw.githubusercontent.com/firedrakeproject/firedrake/${BRANCH}/scripts/firedrake-configure
 
 # Install system dependencies
 RUN apt-get update \
     && apt-get -y install \
         $(python3 /opt/firedrake-configure --arch $ARCH --show-system-packages) \
+        ${APT_EXTRA_PACKAGES} \
     && rm -rf /var/lib/apt/lists/*
 
 # OpenMPI will complain if mpiexec is invoked as root unless these are set
 ENV OMPI_ALLOW_RUN_AS_ROOT=1 OMPI_ALLOW_RUN_AS_ROOT_CONFIRM=1
 
-# Install PETSc. We set the compiler optimisation flags manually here to
-# remove the default of '-march=native -mtune=native' which is not suitable for Docker images.
-RUN git clone --depth 1 --branch $(python3 /opt/firedrake-configure --show-petsc-version) https://gitlab.com/petsc/petsc.git /opt/petsc \
+# Install PETSc.
+# 1. Clone the release tag of PETSc if we're installing a Firedrake release.
+# 2. We set the compiler optimisation flags manually here to remove the default
+#    of '-march=native -mtune=native' which is not suitable for Docker images.
+# 3. Remove non-essential files to reduce container size (keep SLEPc for slepc4py).
+RUN if [ "${BRANCH}" != "main" ]; then \
+        CLONE_ARGS="--branch $(python3 /opt/firedrake-configure --show-petsc-version)"; \
+    fi; \
+    git clone --depth 1 ${CLONE_ARGS} https://gitlab.com/petsc/petsc.git /opt/petsc \
     && cd /opt/petsc \
     && python3 /opt/firedrake-configure --arch $ARCH --show-petsc-configure-options | \
         sed "s/-march=native -mtune=native/-mtune=generic/g" | \
-        xargs -L1 ./configure --with-make-np=8 --download-slepc \
-    && make \
-    && make check \
-    && rm -rf ./**/externalpackages \
-    && rm -rf ./src/docs \
+        xargs -L1 ./configure --with-make-np=8 --download-slepc ${PETSC_EXTRA_ARGS} \
+    && make; \
+    if [ $? -eq 1 ]; then \
+        cat configure.log; \
+        exit; \
+    fi; \
+    make check || exit; \
+    for pkg in $(ls ./arch-firedrake-${ARCH}/externalpackages/); do \
+      if [ "${pkg}" != "git.slepc" ]; then \
+        rm -rf  ./arch-firedrake-${ARCH}/${pkg} || exit; \
+      fi; \
+    done; \
+    rm -rf ./src/docs \
     && rm -f ./src/**/tutorials/output/* \
     && rm -f ./src/**/tests/output/* \
     && cd - || exit
 
 ENV PETSC_DIR=/opt/petsc PETSC_ARCH=arch-firedrake-$ARCH
+ENV SLEPC_DIR=$PETSC_DIR/$PETSC_ARCH
 ENV PATH="$PETSC_DIR/$PETSC_ARCH/bin:$PATH"
 
 ENV HDF5_MPI=ON
@@ -61,5 +137,34 @@ ENV CFLAGS="-mtune=generic" CPPFLAGS="-mtune=generic"
 ENV MPICC=$CC
 
 # Install Firedrake
-RUN pip install --verbose --no-binary h5py --src /opt \
-        --editable git+https://github.com/firedrakeproject/firedrake.git@release#egg=firedrake[docker]
+# - petsc4py and slepc4py are installed from source in PETSc repo.
+# - slepc4py is installed without build isolation so it links against
+#     the correct petsc4py version.
+# - Firedrake main branch requires main/master branch of some upstream
+#     packages. These are installed in editable mode.
+#     The order these are installed is important, e.g. FIAT must be installed
+#     before UFL otherwise `pip install fiat` will reinstall pypi ufl.
+#    && cd /opt/firedrake && git checkout JHopeCollins/more-flexible-docker && cd - \
+RUN git clone --branch ${BRANCH} \
+      https://github.com/firedrakeproject/firedrake.git /opt/firedrake \
+   && pip cache purge \
+   && pip install --verbose ${PETSC_DIR}/src/binding/petsc4py \
+   && pip install --verbose -r /opt/firedrake/requirements-build.txt \
+   && pip install --verbose --no-build-isolation \
+      ${SLEPC_DIR}/externalpackages/git.slepc/src/binding/slepc4py \
+   && pip install --verbose --no-binary h5py --no-build-isolation \
+      --editable '/opt/firedrake[docker]' || exit; \
+   if [ ${BRANCH} == "main" ]; then \
+      for pkg in \
+         "git+https://github.com/dolfin-adjoint/pyadjoint.git#egg=pyadjoint-ad" \
+         "git+https://github.com/firedrakeproject/fiat.git#egg=firedrake-fiat" \
+         "git+https://github.com/FEniCS/ufl.git#egg=fenics-ufl" \
+         ; do \
+            pip install --verbose  --src /opt --editable ${pkg} || exit; \
+        done; \
+    fi
+
+# Run the smoke tests.
+RUN cd /opt/firedrake/ \
+    && firedrake-check \
+    && firedrake-clean
diff --git a/docs/source/install.rst b/docs/source/install.rst
index b37ef042a0..8513d01801 100644
--- a/docs/source/install.rst
+++ b/docs/source/install.rst
@@ -595,7 +595,6 @@ should be followed:
 
    $ pip install --no-build-isolation --no-binary h5py --editable './firedrake[check]'
 
-
 Editing subpackages
 -------------------