diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa80013..1d36dd4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,34 @@
 # Changelog
 
+## [4.0.1] - 2026-09-28
+
+### Fixed
+
+- **A run with no API key now says so when it finishes**, not only when it
+  starts. Without a key the command SUCCEEDS: it reads the 7 days anonymous
+  access allows, writes 433 rows of Magic Kingdom instead of about 94,000, and
+  exits 0. The notice was printed before a run that takes minutes, so it scrolled
+  away, and the last thing on screen was `done: 433 rows` -- which for someone
+  who has just paid for 400 days is indistinguishable from success. There is a
+  file, there is no error, and the number means nothing unless you already know
+  what it should have been.
+
+  The README and the command's own `--help` now `export THEMEPARKS_API_KEY`
+  before the example that needs it, and still say `--list` does not: finding a
+  park before you have paid is the point of that flag.
+
+### Added
+
+- **A committed mutant list** (`tests/mutation/mutants.json`) and a nightly,
+  non-gating job that runs it. An author-written mutant list contains the
+  mutations that author's tests already catch -- one scored 14/14 on this package
+  while an independent sweep found 27 survivors, including the defect 4.0.0
+  exists to fix. The list is committed so a reviewer can see what is checked and,
+  more usefully, what is not. Its first run found two gaps, both closed here: a
+  spent hourly budget on a resumed run deleted the accumulated archive, and
+  `str(EntityType.SHOW)` reached a CSV cell as `EntityType.SHOW` rather than
+  `SHOW`.
+
 ## [4.0.0] - 2026-09-28
 
 **3.3.0 was yanked: incomplete CSV export and a resume defect.**
diff --git a/pyproject.toml b/pyproject.toml
index 1a42116..0239642 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "themeparks"
-version = "4.0.0"
+version = "4.0.1"
 description = "Official SDK for the ThemeParks.wiki API"
 readme = "README.md"
 requires-python = ">=3.9"
diff --git a/uv.lock b/uv.lock
index bfc6c00..72f52ad 100644
--- a/uv.lock
+++ b/uv.lock
@@ -2114,7 +2114,7 @@ wheels = [
 
 [[package]]
 name = "themeparks"
-version = "4.0.0"
+version = "4.0.1"
 source = { editable = "." }
 dependencies = [
     { name = "eval-type-backport", marker = "python_full_version < '3.10'" },