Bitrix24 tasks (server side)

Scope: Bitrix24 on-premise · Verified: tasks 26.300.100, main 26.800.0

Task	Read
Pick the API layer; create, update, complete, delete; errors	`rules/writing.md`
One task or lists: filters, sort, paging, dates	`rules/reading.md`
Members, deadlines and time zones, checklists, tags, projects, templates, comments	`rules/details.md`
Access actions, events and their arguments, REST mapping	`rules/access-events.md`

Invariants

Write through the V2 commands (AddTaskCommand, UpdateTaskCommand …; legacy CTaskItem/CTasks end in the same V2 services). Never write TaskTable or member/checklist tables: counters, chat, search, events and recycle bin are skipped.
Commands do not check rights. Check TaskAccessService/TaskAccessController for the acting user before run().
Pass the acting user id explicitly (userId in configs). Agents and CLI have no $USER; CTasks::Add without USER_ID acts as user 1.
Dates in V2 entities are Unix timestamps (deadlineTs). Never pass site-format strings from background code.
Keep V2 calls in one /local gateway class: commands take V2\Internal\… entities and configs that may change between releases. The V2 layer is verified in tasks 26.300.100 only; if class_exists(AddTaskCommand::class) is false, use CTaskItem.
New task card: comments are messages in the task chat (see rules/details.md, bitrix24-im).