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+# How to launch external SMART on FHIR apps from mcode/request-generator
+
+## Setup
+
+### In mcode/rems-admin
+
+Overwrite `SMART_ENDPOINT` in the `.env`. Overwriting environment variables in a `.env.local` does not work (this is a bug). For example, if you are using a registered app in a Meld Sandbox, your `SMART_ENDPOINT` may look like this:
+
+```.env
+SMART_ENDPOINT = https://smartlauncher.interop.community/sample-app/launch?client_id=sampleapp&platform=meld
+```
+
+### In mcode/request-generator
+
+Set these environment variables in your `.env.local` to overwrite the default values in the `.env`. You must be added to the REMS sandbox on Meld to log in and authenticate when running request-generator locally.
+
+```.env
+REACT_APP_CLIENT = ed8b940e-4aaa-4209-b17d-69dfe67543b9
+REACT_APP_EHR_BASE = https://gw.interop.community/REMS/data
+REACT_APP_EHR_SERVER_TO_BE_SENT_TO_REMS_ADMIN_FOR_PREFETCH = https://gw.interop.community/REMS/data
+REACT_APP_EHR_SERVER = https://gw.interop.community/REMS/data
+REACT_APP_SMART_LAUNCH_URL = https://smartlauncher.interop.community/sample-app/launch?client_id=sampleapp&platform=meld
+```
+
+### Where to grab the environment variable values if using a Meld Sandbox
+
+1. `REACT_APP_CLIENT`: This is taken from Apps > Request Generator > Settings > Registered App Details > Client Id. Request Generator refers to the registered mcode/request-generator app in your Meld sandbox.
+2. `REACT_APP_EHR_BASE`, `REACT_APP_EHR_SERVER_TO_BE_SENT_TO_REMS_ADMIN_FOR_PREFETCH`, `REACT_APP_EHR_SERVER`: These are taken from your Meld sandbox's sidebar, under Settings > Sandbox > Secured FHIR Server URL.
+3. `REACT_APP_SMART_LAUNCH_URL`, `SMART_ENDPOINT`: This is taken from Apps > Sample App > Settings > Registered App Details > App Launch URI\*.
+
+## How to run
+
+1. Start request-generator normally and go to `http://localhost:3000/`. Click the "Authorize" button.
+2. Start rems-admin normally.
+3. In request-generator, click the "Select a Patient" button.
+4. Select Jon Snow (id: 130803).
+5. Click the "Launch SMART on FHIR app" button. This opens the SMART on FHIR app launch page provided as values to the `REACT_APP_SMART_LAUNCH_URL` and `SMART_ENDPOINT` environment variables.
+6. Click the "Authorize" button.
+7. You should see the expected SMART on FHIR app launch properly.
+8. Go back to request-generator and issue an order-sign hook, and click on the "Patient Enrollment Form" button.
+9. You should see the expected SMART on FHIR app launch.
+
+## Running other Registered SMART on FHIR Apps from Meld
+
+Log in to Meld at https://meld.interop.community/. Go to My Sandboxes > REMS > Apps to try out the other Registered Apps. The example above manually tests (1). You can try the remaining options after (2) just by changing the `REACT_APP_SMART_LAUNCH_URL` and `SMART_ENDPOINT` environment variables.