diff --git a/internal/server/content_test.go b/internal/server/content_test.go
index ec98f019..a4a0e89f 100644
--- a/internal/server/content_test.go
+++ b/internal/server/content_test.go
@@ -72,7 +72,7 @@ func TestContentAPIAnswersTheHandshakeWithoutASession(t *testing.T) {
 	if !strings.Contains(body, `"api":0`) {
 		t.Errorf("body = %q, want the api generation", body)
 	}
-	if !strings.Contains(body, `"kit":["0.9.0","0.10.0","0.11.0","0.12.0","0.13.0","0.14.0","0.15.0"]`) {
+	if !strings.Contains(body, `"kit":["0.9.0","0.10.0","0.11.0","0.12.0","0.13.0","0.14.0","0.15.0","0.15.1"]`) {
 		t.Errorf("body = %q, want the kit versions served", body)
 	}
 	if !strings.Contains(body, `"gophenberg"`) {
@@ -358,7 +358,8 @@ func TestContentAPIAdvertisesTheTypesItServes(t *testing.T) {
 	if handshake.API != 0 {
 		t.Errorf("api = %d, want 0", handshake.API)
 	}
-	if !slices.Equal(handshake.Kit, []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0"}) {
+	want := []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0", "0.15.1"}
+	if !slices.Equal(handshake.Kit, want) {
 		t.Errorf("kit = %v, want the kit versions this release serves", handshake.Kit)
 	}
 	if len(handshake.Types) != 1 {
diff --git a/internal/themehost/kit.go b/internal/themehost/kit.go
index a2a93319..b77af3af 100644
--- a/internal/themehost/kit.go
+++ b/internal/themehost/kit.go
@@ -9,7 +9,7 @@ import (
 )
 
 // servedKits names the theme kit versions this release serves, oldest first.
-var servedKits = []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0"}
+var servedKits = []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0", "0.15.1"}
 
 // ServedKits returns the theme kit versions this release serves.
 func ServedKits() []string {
diff --git a/internal/themehost/kit_test.go b/internal/themehost/kit_test.go
index 99c7d1d5..3a1b11e5 100644
--- a/internal/themehost/kit_test.go
+++ b/internal/themehost/kit_test.go
@@ -17,10 +17,10 @@ func TestServedKitsNamesWhatThisReleaseServes(t *testing.T) {
 
 	served := themehost.ServedKits()
 
-	if !slices.Equal(served, []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0"}) {
+	if !slices.Equal(served, []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0", "0.15.1"}) {
 		t.Errorf("ServedKits() = %v, want the kit versions this release serves", served)
 	}
-	if themehost.NewestKit() != "0.15.0" {
+	if themehost.NewestKit() != "0.15.1" {
 		t.Errorf("NewestKit() = %q, want the newest of them", themehost.NewestKit())
 	}
 }
@@ -28,12 +28,12 @@ func TestServedKitsNamesWhatThisReleaseServes(t *testing.T) {
 func TestAThemeOnEitherServedKitIsAccepted(t *testing.T) {
 	t.Parallel()
 
-	for _, declared := range []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0"} {
+	for _, declared := range []string{"0.9.0", "0.10.0", "0.11.0", "0.12.0", "0.13.0", "0.14.0", "0.15.0", "0.15.1"} {
 		if !themehost.ServesKit(declared) {
 			t.Errorf("ServesKit(%q) = false, want a theme on a served kit accepted", declared)
 		}
 	}
-	for _, declared := range []string{"0.8.0", "0.10.3"} {
+	for _, declared := range []string{"0.8.0", "0.10.3", "0.15.2"} {
 		if themehost.ServesKit(declared) {
 			t.Errorf("ServesKit(%q) = true, want a kit this release cannot serve turned away", declared)
 		}
@@ -45,7 +45,7 @@ func TestServedKitsCannotBeChangedByACaller(t *testing.T) {
 
 	themehost.ServedKits()[0] = "9.9.9"
 
-	if themehost.NewestKit() != "0.15.0" {
+	if themehost.NewestKit() != "0.15.1" {
 		t.Errorf("NewestKit() = %q after a caller wrote to the returned slice", themehost.NewestKit())
 	}
 }
diff --git a/sdk/astro/CHANGELOG.md b/sdk/astro/CHANGELOG.md
index fc6ec227..9386894c 100644
--- a/sdk/astro/CHANGELOG.md
+++ b/sdk/astro/CHANGELOG.md
@@ -11,10 +11,11 @@ npm-style tag stays invisible to the Go toolchain, unlike a
 `sdk/astro/vX.Y.Z` tag naming the directory as a module. Versions
 through 0.8.0 shipped in step with Gophenberg under its `vX.Y.Z` tags.
 
-## Unreleased
+## [0.15.1] - 2026-10-13
 
 ### Changed
 
+- A theme built on 0.15.1 needs Gophenberg 0.18.2 or newer.
 - The kit parses blocks with `@wordpress/block-serialization-default-parser` 5.57.0.
 
 ### Fixed
diff --git a/sdk/astro/README.md b/sdk/astro/README.md
index 1568dc1f..ea665c39 100644
--- a/sdk/astro/README.md
+++ b/sdk/astro/README.md
@@ -18,6 +18,10 @@ pnpm add @gophenberg/astro
 
 Astro 7 is a peer dependency.
 
+A site runs a theme only when its Gophenberg release serves the kit
+version the theme was built on. See
+[Theme compatibility](https://docs.gophenberg.org/themes/compatibility/).
+
 ## Use
 
 Two files make an Astro project a theme.
diff --git a/sdk/astro/package.json b/sdk/astro/package.json
index 7944c688..881be15e 100644
--- a/sdk/astro/package.json
+++ b/sdk/astro/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "@gophenberg/astro",
-	"version": "0.15.0",
+	"version": "0.15.1",
 	"type": "module",
 	"license": "Apache-2.0",
 	"description": "Build a Gophenberg theme in Astro: routes, block rendering, and the theme contract.",