Bulk-create Jira issues via REST API v3 (POST /issue/bulk, partial-failure handling)

Documented steps

1. POST https://your-domain.atlassian.net/rest/api/3/issue/bulk — creates up to 50 issues (and subtasks) per request; hard cap.
2. Body: {"issueUpdates":[{"fields":{...},"update":{...}}, ...]} — each element uses the same fields schema as single issue create; description/environment/textarea custom fields must be ADF doc objects, not strings.
3. Subtasks in the same batch: set issuetype to a subtask type id and include parent {"id" or "key"}; subtasks must be in the same project as the parent.
4. 201 is returned if ANY item succeeded: body {"issues":[{id,key,self},...],"errors":[...]} — always check both arrays; partial success still returns 201.
5. 400 only when ALL items are invalid: errors[] entries carry failedElementNumber (index into issueUpdates) and elementErrors with per-field messages — use it to map failures back.
6. Requires Browse Projects + Create Issues permission in each target project. Auth: Basic (email:API token) or OAuth2 write:jira-work.
7. Official docs: https://developer.atlassian.com/cloud/jira/platform/rest/v3/api-group-issues/