diff --git a/.python-version b/.python-version
new file mode 100644
index 0000000..e4fba21
--- /dev/null
+++ b/.python-version
@@ -0,0 +1 @@
+3.12
diff --git a/README.md b/README.md
index 31fdf4a..d67473a 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,21 @@
 # python-flask-server
+
+## Heroku deployment
+
+This app targets the `heroku-26` stack and Python 3.12. Heroku uses the
+`app.json` stack for Review Apps and Heroku CI, and `.python-version` keeps the
+Python major version consistent while allowing automatic patch updates.
+
+To upgrade the existing Cedar app, change its stack before the next deployment:
+
+```sh
+heroku stack:set heroku-26 --app easyeyes-python-flask-server
+```
+
+The next build uses Heroku-26. Confirm the deployed stack and Python version
+afterward:
+
+```sh
+heroku stack --app easyeyes-python-flask-server
+heroku run python --version --app easyeyes-python-flask-server
+```
diff --git a/app.json b/app.json
new file mode 100644
index 0000000..76dbec6
--- /dev/null
+++ b/app.json
@@ -0,0 +1,4 @@
+{
+  "name": "EasyEyes Python Flask Server",
+  "stack": "heroku-26"
+}