diff --git a/.github/pr-types.json b/.github/pr-types.json
new file mode 100644
index 0000000..2f3d64e
--- /dev/null
+++ b/.github/pr-types.json
@@ -0,0 +1,4 @@
+{
+  "all": ["feat!", "fix!", "revert!", "feat", "fix", "revert", "perf", "docs", "refactor", "test", "ci", "chore"],
+  "release": ["feat!", "fix!", "revert!", "feat", "fix", "revert", "perf", "docs"]
+}
diff --git a/.github/scripts/write_release_notes.py b/.github/scripts/write_release_notes.py
index 987e6bf..86b2b18 100644
--- a/.github/scripts/write_release_notes.py
+++ b/.github/scripts/write_release_notes.py
@@ -4,8 +4,7 @@
 import os
 import subprocess
 import sys
-
-PREFIXES = ["feat:", "fix:", "revert:", "perf:", "docs:"]
+from pathlib import Path
 
 
 def gh(*args: str) -> str:
@@ -14,14 +13,19 @@ def gh(*args: str) -> str:
     return result.stdout.strip()
 
 
-def latest_tag() -> str:
-    return gh("release", "list", "-L", "1", "--json", "tagName", "-q", ".[0].tagName")
+LATEST_TAG = gh("release", "list", "-L", "1", "--json", "tagName", "-q", ".[0].tagName")
+
+
+def release_types() -> list[str]:
+    """Return the PR types that appear in release notes."""
+    pr_types_file = Path(__file__).parent.parent / "pr-types.json"
+    return json.loads(pr_types_file.read_text())["release"]
 
 
 def merged_prs() -> list[dict]:
     """Return the number and title of PRs merged since the latest release."""
     repo = os.environ["GITHUB_REPOSITORY"]
-    release_date = gh("api", f"repos/{repo}/releases/tags/{latest_tag()}", "--jq", ".created_at")
+    release_date = gh("api", f"repos/{repo}/releases/tags/{LATEST_TAG}", "--jq", ".created_at")
     prs = gh(
         "pr",
         "list",
@@ -36,27 +40,24 @@ def merged_prs() -> list[dict]:
         "--limit",
         "50",
     )
-    return json.loads(prs)
+    return json.loads(prs)[::-1]  # Put oldest merged first.
 
 
 def release_notes(prs: list[dict], new_tag: str) -> str:
     """Return the release notes body for the given PRs.
 
-    Groups PRs by title prefix then breaking/non-breaking.
+    Groups PRs by title prefix, in the order given by pr-types.json.
     """
     entries = ""
-    for prefix in PREFIXES:
-        breaking_prefix = f"{prefix.removesuffix(':')}!:"
-        group = sorted(
-            (pr for pr in prs if pr["title"].startswith((prefix, breaking_prefix))),
-            key=lambda pr: (not pr["title"].startswith(breaking_prefix), pr["number"]),
-        )
-        for pr in group:
-            entries += f"- {pr['title']} (#{pr['number']})\n"
+    for pr_type in release_types():
+        prefix = f"{pr_type}:"
+        for pr in prs:
+            if pr["title"].startswith(prefix):
+                entries += f"- {pr['title']} (#{pr['number']})\n"
     if not entries:
         entries = "This is a maintenance release with no fixes or new features.\n"
     repo = os.environ["GITHUB_REPOSITORY"]
-    return f"{entries}\nChangelog: https://github.com/{repo}/compare/{latest_tag()}...{new_tag}"
+    return f"{entries}\nChangelog: https://github.com/{repo}/compare/{LATEST_TAG}...{new_tag}"
 
 
 if __name__ == "__main__":
diff --git a/.github/workflows/deps.yaml b/.github/workflows/deps.yaml
new file mode 100644
index 0000000..1d6f84d
--- /dev/null
+++ b/.github/workflows/deps.yaml
@@ -0,0 +1,21 @@
+name: Check Python deps
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+permissions: {}
+
+jobs:
+  deps:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Install uv
+        uses: astral-sh/setup-uv@c18668ad3cf93ea998bef934396af7bb5c839dc7  # v10.2.0
+      - name: Check uv.lock
+        run: uv lock --check
diff --git a/.github/workflows/pr-title.yaml b/.github/workflows/pr-title.yaml
new file mode 100644
index 0000000..9a2fe5d
--- /dev/null
+++ b/.github/workflows/pr-title.yaml
@@ -0,0 +1,28 @@
+name: Check PR title
+
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+
+permissions: {}
+
+jobs:
+  pr-title:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Check PR title
+        env:
+          TITLE: ${{ github.event.pull_request.title }}
+        run: |
+          set -euo pipefail
+          types="$(jq -r '.all | join(", ")' .github/pr-types.json)"
+          pattern="^(${types//, /|}): "
+          if [[ ! "$TITLE" =~ $pattern ]]; then
+            echo "PR title must start with one of: ${types}." >&2
+            exit 1
+          fi
diff --git a/.github/workflows/zizmor.yaml b/.github/workflows/zizmor.yaml
index 1a45ac9..3a75f15 100644
--- a/.github/workflows/zizmor.yaml
+++ b/.github/workflows/zizmor.yaml
@@ -14,8 +14,7 @@ jobs:
     permissions:
       security-events: write
     steps:
-      - name: Checkout repository
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
           persist-credentials: false
       - name: Install uv