Update any issue fields in one write (requires version).

One call = one new version, whatever the number of fields (PO 2026-09-25). links replaces the whole list; board-core adds/removes the inverse links on the other issues in the same commit. transition_issue, assign_issue, move_to_sprint and link_issues stay available as single-purpose tools and follow the same rules. fields (custom fields, spec D129) is merged key by key: send only the keys you change, null removes one.

Call get_issue first and pass its version. Change ANY number of fields in ONE call (title, body, type, priority, severity, status, assignee, points, sprint, release, parent, labels, links) — one call makes exactly one new version, so do not split an edit into several calls. links replaces the whole list. Images in body: upload + attach_file first, then ![file name](path) (never base64). severity (bugs, D113): critical / high / medium / low — how bad it is, separate from priority. release: a planned release id, or null — children of an epic follow the epic's release unless they name another; use move_to_release when the user gives a reason. fields (custom fields, D129) is merged key by key: send only the keys you change, null deletes a value; same types and errors as create_issue (400 unknown_field / invalid_field_value / formula_readonly; types of the field must include the issue's type). Sales & Billing installments (D130): "invoiced" = set invoiced_at (+ invoice_no); "paid" = set paid_at and paid_amount (= amount when paid in full) — dates YYYY-MM-DD, today's date unless the user says another. Do not move the deal to Closed on your own: the deal's all_paid flag says when everything is collected — tell the user and move it only when asked. Rollup fields (D131: a goal's progress / linked, a deal's delivery_progress) are computed like formulas — never in fields (400 formula_readonly); read them in computed. links entries take an issue key of this or another project of the company (403 link_target_forbidden when you cannot open the target's project) or {type: "delivers", id: "KEY/R-n"} for a release (404 release_not_found when it does not exist). For a Roadmap & Goals goal, moving start / end is a fields change like any other. Body: Optional colour (D137, use sparingly; markdown stays the main format): <mark>text</mark> highlights (yellow; or <mark data-color="green">), <span data-color="red">text</span> colours text; colours yellow, green, red, blue, purple (e.g. green = passed / expected, red = bug / actual, purple = question); any other HTML is shown as plain text; keep the open and close tag in the same paragraph.

WRITE: version must be the version from your latest read of this file (get_issue for issues, list_comments for comments, list_sprints for sprints, get_doc for project docs, read_file for md files). If the file changed since, the call fails with 409 version_conflict and the error contains the current file (details.current, details.current_version): re-read it, re-apply your change on top of the current content and retry with the new version. Never overwrite someone else's change blindly — if your change and theirs disagree, ask the user which to keep.

You act with exactly the rights of the user who owns this token; a project you cannot see returns not_found.