diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
new file mode 100644
index 00000000..f70f33e7
--- /dev/null
+++ b/.git-blame-ignore-revs
@@ -0,0 +1,2 @@
+# Reformat JS, CSS, JSON and YAML with oxfmt (#357)
+8ae38e5ba6b5339fbd25f64dd22ce85a1e91cec7
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b495635c..7feca7c3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -119,3 +119,12 @@ jobs:
       - name: Lint the templates' JavaScript (primary only)
         if: matrix.is-primary
         run: uv run --group js python scripts/lint_js.py
+
+      - name: Check JS, CSS, JSON and YAML formatting (primary only)
+        if: matrix.is-primary
+        # Both checks run, so every file that needs formatting is listed
+        run: |
+          status=0
+          uv run --group js oxfmt --check || status=1
+          uv run --group js python scripts/fmt_templates.py --check || status=1
+          exit $status
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 51557172..c2fc0663 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -290,6 +290,17 @@ back verbatim. Each construct must sit on lines of its own; the script
 refuses anything else. Such files are found by their content, but they must
 also be listed in `ignorePatterns`, which a unit test checks.
 
+`just fmt-check` is part of `just ci`, and CI runs it once (on the primary
+job), so a change that isn't formatted fails; run `just fmt-js` before
+committing. The commit that first formatted the tree is listed in
+`.git-blame-ignore-revs`; to have `git blame` look past it, run once:
+
+```bash
+git config blame.ignoreRevsFile .git-blame-ignore-revs
+```
+
+GitHub's blame view reads the file by itself.
+
 When upgrading oxfmt, look at what a run *covers* as well as whether it
 passes: a release can start formatting a new language (Markdown arrived
 after 0.69), and then a bare run rewrites files nobody chose to format.
diff --git a/justfile b/justfile
index e21d760e..736c59aa 100644
--- a/justfile
+++ b/justfile
@@ -109,7 +109,7 @@ fmt-check:
     exit $status
 
 # Fail-fast order: format and lint take seconds, ty is faster than pyright, the full test suite runs last
-ci: format lint lint-js ty typecheck test-all
+ci: format lint lint-js fmt-check ty typecheck test-all
 
 # Regenerate the auto-generated TUI docs assets (screenshots) into docs/assets/tui
 docs-gen: