diff --git a/README.md b/README.md
index 8a4d974..c8385e9 100644
--- a/README.md
+++ b/README.md
@@ -8,12 +8,12 @@ Try it here: [https://future.attejuvonen.fi](https://future.attejuvonen.fi)
 
 ### Dev
 
-1. Set up environment variables
+1. Set up environment variables (e.g. in /.vscode/launch.json)
     - OPENAI_API_KEY
     - OPENAI_ORGANIZATION
     - LOG_ENDPOINT
 
-2. Run server.js with node v17
+2. Run server.js with node v17 (e.g. with VSCode run -> run without debugging)
 
 3. Open http://localhost:3000
 
diff --git a/fly.toml b/fly.toml
index 6dd8ee2..f751b9b 100644
--- a/fly.toml
+++ b/fly.toml
@@ -6,7 +6,7 @@ kill_timeout = 5
 processes = []
 
 [build]
-  builder = "heroku/buildpacks:20"
+  builder = "heroku/builder:24"
 
 [env]
   PORT = "8080"
diff --git a/public/index.html b/public/index.html
index 3765393..ea2fd40 100644
--- a/public/index.html
+++ b/public/index.html
@@ -872,9 +872,9 @@ <h1>
                 return Math.round(Math.random() * 40)
             }
             if (['.', '?', '!'].includes(nextChar)) {
-                return 300 + Math.round(Math.random() * 500)
+                return 150 + Math.round(Math.random() * 250)
             }
-            return Math.round(Math.random() * 120)
+            return Math.round(Math.random() * 60)
         }
 
         const stopSpinner = () => {
diff --git a/server.js b/server.js
index 77a7d45..f39409d 100644
--- a/server.js
+++ b/server.js
@@ -9,6 +9,10 @@ import PROMPT_QA_EXAMPLES from "./prompt-qa-examples.js";
 
 const PROMPT_INSTRUCTIONS = fs.readFileSync('prompt-instructions.txt', 'utf8');
 
+if (!process.env.OPENAI_ORGANIZATION || !process.env.OPENAI_API_KEY) {
+    throw new Error('Missing env variables for OpenAI authentication!')
+}
+
 const configuration = new Configuration({
     organization: process.env.OPENAI_ORGANIZATION,
     apiKey: process.env.OPENAI_API_KEY
@@ -100,7 +104,7 @@ const constructPromptChatGPT = (PROMPT_INSTRUCTIONS, PROMPT_QA_EXAMPLES, session
 
 const smokeTestAPI = async () => {
     try {
-        const response = await openai.retrieveModel("text-davinci-003");
+        const response = await openai.retrieveModel("gpt-4o-2024-05-13");
     } catch (error) {
         serverStatusGreen = false
         const errorMessage = error.response ? (error.response.status + error.response.data) : error.message
@@ -122,7 +126,7 @@ const getResponse = async (PROMPT_INSTRUCTIONS, PROMPT_QA_EXAMPLES, sessionHisto
     }
     try {
         const response = await openai.createChatCompletion({
-            model: "gpt-3.5-turbo-0301",
+            model: "gpt-4o-2024-05-13",
             messages: messages,
             max_tokens: 256,
             temperature: 0.4