---
model: claude-fable-5[1m]
service: claude
timestamp: 2026-06-10T17:11:42Z
git_ref: datad_service
diff_cmd: git log -1 -p --follow -- ai/prompt-io/claude/20260610T171142Z_119d2c04_prompt_io.md
---

NOTE: diff-ref mode entry (code committed in the same
commit as this log); backfilled from the live dev
session transcript per the `/prompt-io` skill rules.

> `git log -1 -p --follow -- piker/data/_daemon.py`

Generated symbols + key design decisions:

- `_datad_service_mods: list[str]` — datad-always
  enabled mods, the data-side successor to the old
  `piker.brokers._daemon._data_mods` set; kept minimal
  per the caps-sec model.
- `_setup_persistent_datad()` — `@tractor.context`
  lifetime fixture: console-log setup then allocates
  the actor-global feed bus via
  `feed.get_feed_bus(brokername, service_nursery)`
  exactly as the old brokerd fixture did, pinned open
  with `ctx.started()` + `sleep_forever()`.
- `datad_init()` — actor name `f'datad.{brokername}'`;
  copies backend `_spawn_kwargs` (CRITICAL for `ib`'s
  `infect_asyncio=True`); builds `enable_modules` from
  `getattr(brokermod, '_datad_mods',
  getattr(brokermod, '__enable_modules__', []))` as
  the flat-backend fallback.
- `spawn_datad()` — `Services.actor_n.start_actor()` +
  `Services.start_service_task()` exactly mirroring
  `spawn_brokerd()`; dedup-composes enable mods via
  `list(dict.fromkeys(...))`.
- `maybe_spawn_datad()` — wraps `maybe_spawn_daemon(
  service_name=f'datad.{brokername}', ...)`.

> `git log -1 -p --follow -- piker/service/_actor_runtime.py`
> `git log -1 -p --follow -- piker/service/__init__.py`
> `git log -1 -p --follow -- tests/test_services.py`

Design rationale (verbatim from session):

- `_root_modules` must gain `piker.data._daemon` so
  `pikerd_portal.run(spawn_datad, ...)` resolves in
  the root.
- the `Services`-based impl style deliberately mirrors
  `spawn_brokerd()` so the eventual `tractor.hilevel`
  `ServiceMngr` port (see the `service_mng_to_tractor`
  branch's d8c21d44 prep, surfaced by the
  user-requested branch-overlap survey) lands
  symmetrically on both spawn fns.
- mod placement (`piker/data/_daemon.py` vs.
  generalizing `piker.brokers._daemon`) follows the
  per-subsystem daemon-mod convention
  (`.clearing._ems`, `.data._sampling`) and resolves
  the existing TODO at `brokers/_daemon.py:49` ("move
  this def to the `.data` subpkg").