diff --git a/.github/workflows/code_changes.yaml b/.github/workflows/code_changes.yaml
index 3ffa1b7d9a..2241a3dc59 100644
--- a/.github/workflows/code_changes.yaml
+++ b/.github/workflows/code_changes.yaml
@@ -80,7 +80,17 @@ jobs:
         - name: Install uv
           uses: astral-sh/setup-uv@v8.1.0
         - name: Check formatting
-          run: uvx ruff format --check .
+          # With the ruff that uv.lock pins, so a new ruff release cannot change
+          # what Lint accepts until the lock is updated.
+          run: |
+            set -euo pipefail
+            ruff=$(uv export --frozen --extra dev --no-hashes --no-header | { grep -E '^ruff==' || true; } | cut -d' ' -f1)
+            if [ "$(printf '%s' "$ruff" | grep -c '^ruff==')" != 1 ]; then
+              echo "::error::uv.lock should pin exactly one ruff; found: ${ruff:-none}"
+              exit 1
+            fi
+            echo "RUFF=$ruff" >> "$GITHUB_ENV"
+            uvx --from "$ruff" ruff format --check .
         - name: Lint
           # The ruff rules pyproject.toml selects, then two pyflakes rules it
           # ignores, checked in the package: F811, a definition that a later
@@ -89,8 +99,8 @@ jobs:
           # notice 16), and F821, an undefined name. Neither has a finding
           # in the package today.
           run: |
-            uvx ruff check .
-            uvx ruff check --select F811,F821 policyengine_uk
+            uvx --from "$RUFF" ruff check .
+            uvx --from "$RUFF" ruff check --select F811,F821 policyengine_uk
   # The same suite as pull requests (test-suite.yaml), on the merged commit.
   Test:
     needs: Tested
diff --git a/.github/workflows/pr_code_changes.yaml b/.github/workflows/pr_code_changes.yaml
index e959391554..2f22d1ed82 100644
--- a/.github/workflows/pr_code_changes.yaml
+++ b/.github/workflows/pr_code_changes.yaml
@@ -110,7 +110,17 @@ jobs:
         - name: Install uv
           uses: astral-sh/setup-uv@v8.1.0
         - name: Check formatting
-          run: uvx ruff format --check .
+          # With the ruff that uv.lock pins, so a new ruff release cannot change
+          # what Lint accepts until the lock is updated.
+          run: |
+            set -euo pipefail
+            ruff=$(uv export --frozen --extra dev --no-hashes --no-header | { grep -E '^ruff==' || true; } | cut -d' ' -f1)
+            if [ "$(printf '%s' "$ruff" | grep -c '^ruff==')" != 1 ]; then
+              echo "::error::uv.lock should pin exactly one ruff; found: ${ruff:-none}"
+              exit 1
+            fi
+            echo "RUFF=$ruff" >> "$GITHUB_ENV"
+            uvx --from "$ruff" ruff format --check .
         - name: Lint
           # The ruff rules pyproject.toml selects, then two pyflakes rules it
           # ignores, checked in the package: F811, a definition that a later
@@ -119,8 +129,8 @@ jobs:
           # notice 16), and F821, an undefined name. Neither has a finding
           # in the package today.
           run: |
-            uvx ruff check .
-            uvx ruff check --select F811,F821 policyengine_uk
+            uvx --from "$RUFF" ruff check .
+            uvx --from "$RUFF" ruff check --select F811,F821 policyengine_uk
         - name: No agent working notes at the repository root
           # Agent jobs keep their working notes at the root of their
           # worktree, and #2376's REPORT.md and PROGRESS.md reached main by
@@ -150,16 +160,10 @@ jobs:
     steps:
       - name: Checkout repo
         uses: actions/checkout@v6
-      - name: Install uv
-        uses: astral-sh/setup-uv@v8.1.0
-      - name: Set up Python
-        uses: actions/setup-python@v6
-        with:
-          python-version: '3.13'
-      - name: Install package
-        run: uv pip install -e .[dev] --system
-      - name: Install policyengine
-        run: uv pip install policyengine --system
+      # The environment the tests use: uv.lock with the dev extra (which
+      # includes jupyter-book), so a new release cannot change the build.
+      - name: Install the locked environment
+        uses: ./.github/actions/test-environment
       - name: Test documentation builds
         run: make documentation
   # The YAML tests, the Python tests on five runners, and the check that
diff --git a/.github/workflows/pr_docs_changes.yaml b/.github/workflows/pr_docs_changes.yaml
index f3468523a3..09f7d5cad6 100644
--- a/.github/workflows/pr_docs_changes.yaml
+++ b/.github/workflows/pr_docs_changes.yaml
@@ -26,19 +26,9 @@ jobs:
       steps:
           - name: Checkout repo
             uses: actions/checkout@v6
-          - name: Install uv
-            uses: astral-sh/setup-uv@v8.1.0
-
-          - name: Set up Python
-            uses: actions/setup-python@v6
-            with:
-                python-version: '3.13'
-              
-          - name: Install package
-            run: uv pip install -e .[dev] --system
-          - name: Install policyengine
-            run: uv pip install policyengine --system
-          - name: Install JB
-            run: uv pip install "jupyter-book>=2.0.0a0" --system
+          # The environment the tests use: uv.lock with the dev extra (which
+          # includes jupyter-book), so a new release cannot change the build.
+          - name: Install the locked environment
+            uses: ./.github/actions/test-environment
           - name: Test documentation builds
             run: make documentation
\ No newline at end of file
diff --git a/.github/workflows/versioning.yaml b/.github/workflows/versioning.yaml
index d929669041..c605d856e0 100644
--- a/.github/workflows/versioning.yaml
+++ b/.github/workflows/versioning.yaml
@@ -269,7 +269,17 @@ jobs:
       - name: Install uv
         uses: astral-sh/setup-uv@v8.1.0
       - name: Check formatting
-        run: uvx ruff format --check .
+        # With the ruff that uv.lock pins, so a new ruff release cannot change
+        # what Lint accepts until the lock is updated.
+        run: |
+          set -euo pipefail
+          ruff=$(uv export --frozen --extra dev --no-hashes --no-header | { grep -E '^ruff==' || true; } | cut -d' ' -f1)
+          if [ "$(printf '%s' "$ruff" | grep -c '^ruff==')" != 1 ]; then
+            echo "::error::uv.lock should pin exactly one ruff; found: ${ruff:-none}"
+            exit 1
+          fi
+          echo "RUFF=$ruff" >> "$GITHUB_ENV"
+          uvx --from "$ruff" ruff format --check .
       - name: Lint
         # The ruff rules pyproject.toml selects, then two pyflakes rules it
         # ignores, checked in the package: F811, a definition that a later
@@ -278,8 +288,8 @@ jobs:
         # notice 16), and F821, an undefined name. Neither has a finding
         # in the package today.
         run: |
-          uvx ruff check .
-          uvx ruff check --select F811,F821 policyengine_uk
+          uvx --from "$RUFF" ruff check .
+          uvx --from "$RUFF" ruff check --select F811,F821 policyengine_uk
 
   Compat:
     # What a user gets: the wheel, with the newest dependencies it allows,
diff --git a/changelog.d/ci-lint-docs-from-lock.fixed.md b/changelog.d/ci-lint-docs-from-lock.fixed.md
new file mode 100644
index 0000000000..f631b550c1
--- /dev/null
+++ b/changelog.d/ci-lint-docs-from-lock.fixed.md
@@ -0,0 +1 @@
+- Lint and the documentation build now install from uv.lock, as the tests already do, so a new release of ruff, jupyter-book or another dependency cannot change what pull requests are checked against.