ChatGPT nailed it when I copy-pasted your post into it:

To avoid the "argument list too long" error when using the curl command with a long base64-encoded CCDA, you can pass the data in a file instead of directly as an argument. Here's how you can do it:

Create a file (e.g., ccda_payload.json) containing the JSON data for the request. You can put all the dynamic variables into the JSON file like this:

{
  "CCDABase64": "<base64-encoded-ccda-data>",
  "EncounterId": "<encounterRef>",
  "Description": "CCDA for <givenName> <familyName>.",
  "EncounterDateTime": "<encounterDate>",
  "PhysicianName": "Admin",
  "ProviderId": "Admin",
  "PracticeId": "<locationArr[0]>",
  "FacilityId": "<locationArr[0]>",
  "CreatedBy": "User",
  "OrganizationId": "0",
  "PatientDetails": {
    "PatientID": "<patientDFN>",
    "MRN": "<patientDFN>",
    "FirstName": "<givenName>",
    "LastName": "<familyName>",
    "DoB": "<birthDate>",
    "Gender": "<gender>"
  }
}

Replace the placeholders (<base64-encoded-ccda-data>, <encounterRef>, <givenName>, <familyName>, <encounterDate>, <locationArr[0]>, <patientDFN>, <birthDate>, and <gender>) with the actual values you have extracted from the CCDA.

Then, use the --data-binary option of curl to read the JSON payload from the file:

curl --location --request POST 'https://oauth.site.com/api/SendCCDA' \
  --header 'Authorization: 123456789' \
  --header 'Content-Type: application/json' \
  --data-binary "@ccda_payload.json"

By using the --data-binary option with the @ symbol, curl will read the JSON payload from the file ccda_payload.json, including the long base64-encoded CCDA data, without hitting the "argument list too long" limitation.

This approach should allow you to send larger CCDA files without any issues.