curl -sS -X POST https://app.opentrain.ai/api/public/v1/milestones/<MILESTONE_ID>/fund \
  -H "Authorization: Bearer $OT_API_TOKEN"

opentrain milestones fund --milestone-id <MILESTONE_ID> --json

{
  "milestoneId": "<MILESTONE_ID>"
}

{
  "approval": {
    "id": "<APPROVAL_ID>",
    "type": "milestone_fund",
    "status": "pending",
    "contractId": "<CONTRACT_ID>",
    "milestoneId": "<MILESTONE_ID>",
    "jobId": "<JOB_ID>",
    "approvalUrl": "https://app.opentrain.ai/approvals/<APPROVAL_ID>",
    "expiresAt": "2026-06-15T10:00:00.000Z",
    "resolvedAt": null,
    "result": null,
    "createdAt": "2026-06-12T10:00:00.000Z"
  },
  "message": "Funding request recorded. A signed-in human must confirm this approval in the OpenTrain app before any money moves."
}

{
  "error": "No payment method on file. A human must add a card in the OpenTrain app before milestone funding can be requested.",
  "code": "CONFLICT",
  "requestId": "<REQUEST_ID>",
  "details": {
    "milestoneId": "<MILESTONE_ID>",
    "reason": "payment_method_required",
    "billingUrl": "https://app.opentrain.ai/employer-settings?tab=billing"
  }
}