The package landed here with one store spec; the rest of its tests were written
three layers up, so this layer and the two above it failed the per-file
coverage gate on 191 locations while every test passed.
Adds the node half's invariant companion, the two components, the registration
apply, and the stores' failure paths. `currentValue` drops a `?? ''` that an
empty roster already returned before reaching — the same shape the later layer
arrived at, so the two converge instead of conflicting.
Six review findings on the select surface, all reachable from the wire:
**Resume read the header, not the log.** The switch was recorded as
`agent-preset/selected` and every projection resolved from it, but `agentFor`
still composed from `inspected.meta.agentPreset` — the value written once at
creation. A blank session that switched and then ran turns came back after a
restart under the ORIGINAL preset, restoring that history under the tool set it
was not produced with, which is the mismatch this feature exists to prevent.
`inspected` already carries the events.
**Cold summaries dropped the preset entirely.** `summarizeCold` hand-copied
three header fields and omitted the fourth, so a restored session reported no
preset and the picker showed the deployment default. It now uses the same
projection the attached path does.
**`select` had no gate.** Two concurrent selects both passed the blank check;
the second `unmountPresetFor` then found no record, because the first had
already removed it, and both mounts installed into one agent layer. Selects on
one session now queue, and the blank check is re-read inside the queue. This is
not turn admission — a `session.prompt` racing a switch is the agent loop's to
reserve — but it closes the select-versus-select tear-down.
**A same-id restore was skipped.** The roster is a live directory, so "the same
inputs that worked a moment ago" does not hold: a changed file is exactly how a
same-id reselect fails, and skipping the restore left the agent with no
composition at all.
**`writable` was dead state**, initialized true and never set, so the row could
never disable. It now carries `settings.describe`'s bit — a browser that may
not write settings sees the current default and no control, rather than one
whose write answers `settings-not-exposed`.
**`list` was documented as id-ordered.** It is root-precedence order with each
root's own presets sorted, first root to supply an id winning.
A seat in the composer tool row, left of the model select, showing the preset
THIS session runs — its own recorded one, not the deployment default, because a
resumed session runs what it was created with. `SessionSummary` carries
`agentPreset` for that, alongside `cwd` and `origin`.
The switch exists only while the conversation has not started. After the first
turn the seat becomes a plain label rather than a disabled menu: a greyed
control reads as "temporarily unavailable", when in fact the choice is gone for
good. The seat never asks in that state, and the host refuses independently
with `agent-preset-locked`, so a stale client cannot slip one past it.
A rejected switch restores the previous value and surfaces the host's message
rather than leaving the seat showing something the session is not running.
One settings row picking which preset new sessions are composed from.
It is deliberately a new-session preference, not a live switch: a session's
preset is fixed at creation and the host refuses to adopt an existing session
under a different one, so the row says "applies to sessions you start from now
on" rather than implying it can retune a running agent.
Options and the current value come from one `agentPreset.list` call — the
roster already reports which id an unspecified session gets, so the row needs
no settings-schema introspection, unlike the permission row it is modelled on.
The write targets only the namespace's `default` field.
The menu marks `user` rows: a locally authored preset is exactly as privileged
as the plugins it names, and presenting it identically to a shipped one would
hide that.
An empty roster reads as `unavailable` and renders nothing, because composing
no presets is a valid deployment rather than a failure — distinct from a
roster call that failed, which surfaces its message.
Yichen Jiang