From 5d1d06d666daaf25d8bb6572545a9d7c06f04476 Mon Sep 17 00:00:00 2001
From: Adam Dangoor <adamdangoor@gmail.com>
Date: Tue, 8 Sep 2026 20:25:39 +0100
Subject: [PATCH 1/6] Enforce semantic line breaks with Snapper

---
 .github/workflows/semantic-line-breaks.yml | 29 ++++++++++++++++++++++
 docs/source/unreleased.rst                 |  4 +--
 2 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 .github/workflows/semantic-line-breaks.yml

diff --git a/.github/workflows/semantic-line-breaks.yml b/.github/workflows/semantic-line-breaks.yml
new file mode 100644
index 000000000..16647cd2d
--- /dev/null
+++ b/.github/workflows/semantic-line-breaks.yml
@@ -0,0 +1,29 @@
+name: Semantic line breaks
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+permissions: {}
+
+jobs:
+  semantic-line-breaks:
+    name: Snapper
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
+      - name: Check semantic line breaks
+        run: >-
+          git ls-files -z -- '*.md' '*.rst' ':(exclude)vendored/**'
+          | xargs -0 --no-run-if-empty
+          uvx
+          --from
+          'git+https://github.com/TurtleTech-ehf/snapper.git@bcd3458e27e4156ce4e0a0b55a227400328fb3b1'
+          snapper --max-width 0 --check
+
diff --git a/docs/source/unreleased.rst b/docs/source/unreleased.rst
index 22ac74723..d297d1976 100644
--- a/docs/source/unreleased.rst
+++ b/docs/source/unreleased.rst
@@ -1,8 +1,8 @@
 Unreleased changes
 ==================
 
-Changes that have landed on the main branch but are not yet part of a
-tagged release.  These entries are assembled into the
+Changes that have landed on the main branch but are not yet part of a tagged release.
+These entries are assembled into the
 :doc:`changelog` when the next release is published.
 
 .. towncrier-draft-entries::

From ab0aa2ceeaff777cb45e5a81cd6ebc1a7e99d1a7 Mon Sep 17 00:00:00 2001
From: Adam Dangoor <adamdangoor@gmail.com>
Date: Tue, 8 Sep 2026 20:53:55 +0100
Subject: [PATCH 2/6] Run Snapper through Prek

---
 .github/workflows/semantic-line-breaks.yml | 29 ----------------------
 prek.toml                                  | 13 ++++++++++
 pyproject.toml                             |  1 +
 3 files changed, 14 insertions(+), 29 deletions(-)
 delete mode 100644 .github/workflows/semantic-line-breaks.yml

diff --git a/.github/workflows/semantic-line-breaks.yml b/.github/workflows/semantic-line-breaks.yml
deleted file mode 100644
index 16647cd2d..000000000
--- a/.github/workflows/semantic-line-breaks.yml
+++ /dev/null
@@ -1,29 +0,0 @@
-name: Semantic line breaks
-
-on:
-  pull_request:
-  push:
-    branches:
-      - main
-
-permissions: {}
-
-jobs:
-  semantic-line-breaks:
-    name: Snapper
-    runs-on: ubuntu-latest
-    steps:
-      - name: Check out repository
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
-      - name: Check semantic line breaks
-        run: >-
-          git ls-files -z -- '*.md' '*.rst' ':(exclude)vendored/**'
-          | xargs -0 --no-run-if-empty
-          uvx
-          --from
-          'git+https://github.com/TurtleTech-ehf/snapper.git@bcd3458e27e4156ce4e0a0b55a227400328fb3b1'
-          snapper --max-width 0 --check
-
diff --git a/prek.toml b/prek.toml
index c013e7e46..9869ba179 100644
--- a/prek.toml
+++ b/prek.toml
@@ -364,6 +364,19 @@ hooks = [
     additional_dependencies = ["uv==0.11.7"],
     stages = ["pre-commit"]
   },
+  {
+    id = "snapper",
+    name = "snapper",
+    entry = "uv run --group=dev snapper --max-width 0 --in-place",
+    language = "python",
+    types_or = [
+      "rst",
+      "markdown"
+    ],
+    require_serial = true,
+    additional_dependencies = ["uv==0.11.7"],
+    stages = ["pre-commit"]
+  },
   {
     id = "vale",
     name = "vale",
diff --git a/pyproject.toml b/pyproject.toml
index d764b3dcd..db2eb3378 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -75,6 +75,7 @@ dev = [
     # use it to lint shell commands in GitHub workflow files.
     "shellcheck-py==0.11.0.1",
     "shfmt-py==4.1.0",
+    "snapper-fmt @ git+https://github.com/TurtleTech-ehf/snapper.git@bcd3458e27e4156ce4e0a0b55a227400328fb3b1",
     "sphinx==9.1.0",
     "sphinx-copybutton==0.5.2",
     "sphinx-lint==1.0.2",

From aeb67c94b11ba9ae65edc661e176425882b1ac77 Mon Sep 17 00:00:00 2001
From: Adam Dangoor <adamdangoor@gmail.com>
Date: Tue, 8 Sep 2026 21:15:47 +0100
Subject: [PATCH 3/6] Isolate the Snapper dependency group

---
 prek.toml      | 2 +-
 pyproject.toml | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/prek.toml b/prek.toml
index 9869ba179..9b3f03f22 100644
--- a/prek.toml
+++ b/prek.toml
@@ -367,7 +367,7 @@ hooks = [
   {
     id = "snapper",
     name = "snapper",
-    entry = "uv run --group=dev snapper --max-width 0 --in-place",
+    entry = "uv run --group=snapper snapper --max-width 0 --in-place",
     language = "python",
     types_or = [
       "rst",
diff --git a/pyproject.toml b/pyproject.toml
index db2eb3378..acaacc07a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -75,7 +75,6 @@ dev = [
     # use it to lint shell commands in GitHub workflow files.
     "shellcheck-py==0.11.0.1",
     "shfmt-py==4.1.0",
-    "snapper-fmt @ git+https://github.com/TurtleTech-ehf/snapper.git@bcd3458e27e4156ce4e0a0b55a227400328fb3b1",
     "sphinx==9.1.0",
     "sphinx-copybutton==0.5.2",
     "sphinx-lint==1.0.2",
@@ -98,6 +97,9 @@ dev = [
     "zizmor==1.30.0",
 ]
 release = [ "check-wheel-contents==0.6.3", "towncrier==26.9.0" ]
+snapper = [
+    "snapper-fmt @ git+https://github.com/TurtleTech-ehf/snapper.git@bcd3458e27e4156ce4e0a0b55a227400328fb3b1",
+]
 
 [tool.setuptools]
 packages.find.where = [

From aa02fe7428246f2f7bbf19368455f8b7765ef0e9 Mon Sep 17 00:00:00 2001
From: Adam Dangoor <adamdangoor@gmail.com>
Date: Tue, 8 Sep 2026 21:33:43 +0100
Subject: [PATCH 4/6] Enable Snapper Vale rules

---
 .vale.ini                             |  3 ++-
 styles/snapper/LongProseLine.yml      | 11 +++++++++++
 styles/snapper/SemanticLineBreaks.yml | 11 +++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 styles/snapper/LongProseLine.yml
 create mode 100644 styles/snapper/SemanticLineBreaks.yml

diff --git a/.vale.ini b/.vale.ini
index 250e9b2dd..547f93b8a 100644
--- a/.vale.ini
+++ b/.vale.ini
@@ -4,7 +4,8 @@ MinAlertLevel = error
 Packages = https://github.com/tbhb/vale-ai-tells/releases/download/v1.29.0/ai-tells.zip
 
 [*.{rst,md}]
-BasedOnStyles = ai-tells
+BasedOnStyles = ai-tells, snapper
+snapper.SemanticLineBreaks = error
 
 # These rules misclassify established technical, example, or release-note prose
 # in this repository. All other ai-tells rules remain enforced.
diff --git a/styles/snapper/LongProseLine.yml b/styles/snapper/LongProseLine.yml
new file mode 100644
index 000000000..1f5029f7d
--- /dev/null
+++ b/styles/snapper/LongProseLine.yml
@@ -0,0 +1,11 @@
+---
+# Vale style rule: flag prose lines that are suspiciously long.
+# Likely indicates wrapped text that should use semantic line breaks.
+extends: existence
+message: Prose line exceeds 120 characters. Consider running 'snapper' to break at
+  sentence boundaries.
+level: suggestion
+scope: paragraph
+# This catches lines > 120 chars that contain a period followed by a space.
+# Pure code or URLs are less likely to match.
+tokens: ['.{120,}']
diff --git a/styles/snapper/SemanticLineBreaks.yml b/styles/snapper/SemanticLineBreaks.yml
new file mode 100644
index 000000000..3f4edaf55
--- /dev/null
+++ b/styles/snapper/SemanticLineBreaks.yml
@@ -0,0 +1,11 @@
+---
+# Vale style rule: flag lines containing multiple sentences.
+# These should be broken at sentence boundaries.
+extends: existence
+message: Line contains multiple sentences. Run 'snapper --check' or reformat with
+  'snapper --in-place'.
+level: warning
+scope: paragraph
+# Match a sentence-ending punctuation followed by a space and a capital letter
+# on the same line (indicating two sentences on one line).
+tokens: ['[.!?]\\s+[A-Z]']

From 8ed531b5303c9945355fa78455405e63446d6882 Mon Sep 17 00:00:00 2001
From: Adam Dangoor <adamdangoor@gmail.com>
Date: Tue, 8 Sep 2026 21:57:20 +0100
Subject: [PATCH 5/6] Use the Snapper 0.11.0 release

---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index acaacc07a..5953bde45 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -98,7 +98,7 @@ dev = [
 ]
 release = [ "check-wheel-contents==0.6.3", "towncrier==26.9.0" ]
 snapper = [
-    "snapper-fmt @ git+https://github.com/TurtleTech-ehf/snapper.git@bcd3458e27e4156ce4e0a0b55a227400328fb3b1",
+    "snapper-fmt==0.11.0",
 ]
 
 [tool.setuptools]

From 5a99a71b3330636fd820e68c8700ad2c4eacc957 Mon Sep 17 00:00:00 2001
From: Adam Dangoor <adamdangoor@gmail.com>
Date: Tue, 8 Sep 2026 22:05:01 +0100
Subject: [PATCH 6/6] Use the development dependency group for Snapper

---
 prek.toml      | 2 +-
 pyproject.toml | 4 +---
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/prek.toml b/prek.toml
index 9b3f03f22..9869ba179 100644
--- a/prek.toml
+++ b/prek.toml
@@ -367,7 +367,7 @@ hooks = [
   {
     id = "snapper",
     name = "snapper",
-    entry = "uv run --group=snapper snapper --max-width 0 --in-place",
+    entry = "uv run --group=dev snapper --max-width 0 --in-place",
     language = "python",
     types_or = [
       "rst",
diff --git a/pyproject.toml b/pyproject.toml
index 5953bde45..57d650a43 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -75,6 +75,7 @@ dev = [
     # use it to lint shell commands in GitHub workflow files.
     "shellcheck-py==0.11.0.1",
     "shfmt-py==4.1.0",
+    "snapper-fmt==0.11.0",
     "sphinx==9.1.0",
     "sphinx-copybutton==0.5.2",
     "sphinx-lint==1.0.2",
@@ -97,9 +98,6 @@ dev = [
     "zizmor==1.30.0",
 ]
 release = [ "check-wheel-contents==0.6.3", "towncrier==26.9.0" ]
-snapper = [
-    "snapper-fmt==0.11.0",
-]
 
 [tool.setuptools]
 packages.find.where = [