diff --git a/.gitignore b/.gitignore
index fff3377..c159944 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,4 +21,4 @@ lerna-debug.log*
 *.sln
 *.sw?
 
-backend/.secrets.js
+backend/.env
diff --git a/README.md b/README.md
index f59793f..853e905 100644
--- a/README.md
+++ b/README.md
@@ -24,12 +24,12 @@ unzip kongruity.zip
 cd kongruity
 ```
 
-### 2. Create a secrets file
+### 2. Create an environment file
 
-The backend expects a `.secrets.js` file containing an Anthropic API key in the root `backend/` directory. This file is git-ignored and must be created manually:
+The backend expects a `.env` file containing an Anthropic API key in the root `backend/` directory. This file is git-ignored and must be created manually:
 
 ```bash
-echo 'export const anthropicApiKey = "<your Anthropic API key>"' > backend/.secrets.js
+echo 'ANTHROPIC_API_KEY=<your Anthropic API key>' > backend/.env
 ```
 
 Replace `<your Anthropic API key>` with your actual key.
diff --git a/backend/server.js b/backend/server.js
index f62c4e6..fbb2fef 100644
--- a/backend/server.js
+++ b/backend/server.js
@@ -1,3 +1,4 @@
+import 'dotenv/config';
 import app from './app.js';
 
 const PORT = process.env.PORT || 3001;
diff --git a/backend/services/clustering.service.js b/backend/services/clustering.service.js
index f1e72d1..bd81d98 100644
--- a/backend/services/clustering.service.js
+++ b/backend/services/clustering.service.js
@@ -1,8 +1,7 @@
 import Anthropic from "@anthropic-ai/sdk";
-import { anthropicApiKey } from "../.secrets.js";
 
 const client = new Anthropic({
-  apiKey: anthropicApiKey,
+  apiKey: process.env.ANTHROPIC_API_KEY,
 });
 
 const buildPrompt = (notes) => {
diff --git a/backend/tests/Clustering.service.test.js b/backend/tests/Clustering.service.test.js
index 34cc13a..74a0596 100644
--- a/backend/tests/Clustering.service.test.js
+++ b/backend/tests/Clustering.service.test.js
@@ -14,10 +14,6 @@ vi.mock('@anthropic-ai/sdk', () => {
   };
 });
 
-vi.mock('../.secrets.js', () => ({
-  anthropicApiKey: 'test-key-not-real',
-}));
-
 import { clusterNotes } from '../services/clustering.service.js';
 
 const MOCK_NOTES = [