diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4ae277f..bbdd9f5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -32,6 +32,17 @@ jobs:
       - name: Install Python validator dependencies
         run: pip install "jsonschema>=4,<5" regex
 
+      # Prose gate (make prose-check): ms-check over docs/ + README with the
+      # rule set from pyproject.toml - em-dashes (the STYLE.md ban) and
+      # invisible characters (the W-INVISIBLE-CHAR class, applied to our own
+      # prose; its first run found a raw U+0000 in a proposal code example).
+      # Pinned like every other gate dependency: a floating linter version is
+      # a gate whose rules change under the repo.
+      - name: Prose gate (manuscript-tools ms-check)
+        run: |
+          pip install manuscript-tools==0.11.0
+          make prose-check
+
       - name: Lesson-types drift gate (regenerate from schema, expect no diff)
         run: node scripts/generate-lesson-types.mjs --check
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index e400b7e..569d5f5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,33 @@ All notable changes to `learn-content-engine`. The format is inspired by
 
 ## [Unreleased]
 
+### Prose gate: manuscript-tools ms-check over docs/ + README
+
+The sibling library `manuscript-tools` (PyPI, pinned 0.11.0) already
+carries the invisible-characters check this engine's lint was seeded
+from, plus the em-dash ban the blog STYLE rules demand - so the docs
+prose is now gated by it instead of by convention. `make prose-check`
+(and CI) runs `ms-check` with two rules active (`no-dashes`,
+`no-invisible-chars`; the German-prose and whitespace heuristics are
+disabled via `pyproject.toml` because they are wrong for an English
+Markdown corpus). Guards learned today, applied here: the gate proves
+the file set is non-empty before trusting a green run (`ms-check` exits
+0 on an empty set, manuscript-tools#9), `STYLE.md` is excluded because
+it SHOWS the banned characters, and the CHANGELOG stays out because old
+entries describe a point in time.
+
+The gate earned its keep on its first measured run: a raw U+0000 sat in
+a code example of `docs/proposals/author-ergonomics-app-track.md` (a
+join separator quoted as the real byte instead of its escape - the same
+pattern engine#135 removed from the sources, third instance today). Now
+spelled as the escape. Seeded probes: an em-dash and a zero-width space
+each turn the gate red; an empty docs set trips the floor.
+
+The comparison also went the other way: manuscript-tools' checker and
+sanitizer are both blind to the C1 control range `U+0080-U+009F` (the
+cp1252-mojibake class this engine's lint covers); reported as
+manuscript-tools#11.
+
 ### Source files are text to every tool again (engine#135)
 
 `src/stable-id-stability.ts` carried four RAW NUL bytes as key
diff --git a/Makefile b/Makefile
index db5a03f..9393a28 100644
--- a/Makefile
+++ b/Makefile
@@ -61,6 +61,16 @@ sync-types-check: ## Exit non-zero if the generated lesson types drift from the
 conformance-real: build ## Clone all public content repos (read-only) and run every set + lesson through the full engine pipeline
 	node scripts/conformance-real.mjs
 
+prose-check: ## Prose gate over docs/ + README (ms-check: em-dashes, invisible chars)
+	@# Floor first: ms-check exits 0 on an empty file set (manuscript-tools#9,
+	@# fails open), so the gate proves the set is non-empty before trusting a
+	@# green run. STYLE.md is excluded on purpose: it SHOWS the banned
+	@# characters. CHANGELOG stays out: old entries describe a point in time.
+	@test "$$(find docs -name '*.md' ! -name 'STYLE.md' | wc -l)" -ge 10 \
+		|| { echo "prose-check: docs/ yields fewer than 10 markdown files - wrong directory?"; exit 2; }
+	ms-check docs --exclude "blog/STYLE.md" --exclude "blog/de/STYLE.md"
+	ms-check README.md
+
 # ─── Package ─────────────────────────────────────────────────────────
 
 pack-dry: build ## Show publish contents of the tarball without publishing
diff --git a/docs/proposals/author-ergonomics-app-track.md b/docs/proposals/author-ergonomics-app-track.md
index aae22e1..2c10a4a 100644
Binary files a/docs/proposals/author-ergonomics-app-track.md and b/docs/proposals/author-ergonomics-app-track.md differ
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..1cbcf3a
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,18 @@
+# This repo is an npm package; this file exists ONLY to configure the
+# manuscript-tools prose gate (make prose-check, pinned in CI). ms-check
+# resolves [tool.manuscript-tools] from the closest pyproject.toml - having
+# our own here also stops a stray parent-directory config from leaking in.
+#
+# Active rules after the disables: no-dashes (the STYLE.md em-dash ban) and
+# no-invisible-chars (the W-INVISIBLE-CHAR class, applied to our own prose -
+# it found a raw U+0000 in a proposal's code example on its first run).
+# Disabled because they are wrong for this corpus: the docs are mostly
+# English Markdown with tables and code blocks, so German quote style,
+# double-space and formatting heuristics fire on legitimate text.
+[tool.manuscript-tools]
+disable = [
+  "no-double-spaces",
+  "non-german-quotes",
+  "broken-formatting",
+  "no-repeated-words",
+]