A preset is now ONE composition per process, not one per session. The roster
mounts it once under a synthetic standing scope; each agent joins by having
its scope key parented to the mount's. Two mechanisms in dsh-scope carry the
whole change: registration views walk the parent chain (global → preset →
agent, nearest shadowing farthest — ScopedLayers.chainLayers), and scoped
event dispatch admits a listener tagged with an ancestor of the carrier key,
which is what lets a standing composition's plan/compaction/token listeners
observe each agent composed under it while a sibling preset's stay deaf.
The preset plugins already key their state by Session/Agent — they predate
presets and were written for the shared world — so sharing one instance is a
return to their design, not a rewrite. Preset ymls are unchanged: one mount
per preset means one Entry per preset, whose entry-local realms keep two
presets' services apart exactly as they kept two sessions' apart before.
The standing scope hangs off the service's UNTRACED context (selfCtx): a
method invoked through the traceable proxy sees this.ctx rebound to the
caller and carrying its shadow, and a subtree minted from that resolves every
service through the shadow's fiber instead of each entry's own inject store —
preset rows then fail on the very services they declare.
A standing mount survives its agents deliberately. The composition a running
session joined must outlive the file changing or disappearing underneath it;
reclamation happens at whole-tree teardown, and file edits reach only future
generations (the authoring layer swaps the pointer, never disposes a joined
generation).
A composition that shares one `isolate` realm across rows needs a
`cordis:group` row, and a preset living outside this workspace — the
authored ones under the Harness home — cannot resolve
`@cordisjs/plugin-group` by name: Node's upward `node_modules` walk
never reaches the harness from there. Registering it as a loader builtin
beside `cordis:include` loads both through the ambient module pipeline
instead.
Record it in the preset Agent Note, which leans on the realm vocabulary
without saying where the group row comes from, and drop the preset
README's limitation claiming this builtin is unavailable — it described
the state this change ends.
The test's assertion had a vacuous escape: `provide` mints the root
symbol unconditionally, so the `rootKey === undefined` disjunct could
never hold and the comment claiming the root realm never learned the
name was wrong. Pin both halves — the symbol exists, nothing is stored
under it — and clean up the global the fixture writes.
Records are pruned by observation rather than by a disposal hook, for the
reason the module already states: three different owners can tear a
subtree down, and a cleared `uid` is what they share. That leaves the
pruning to whoever reads — and the only production reader is the
invariant companion, whose package is a development composition a
shipped host never loads.
So a live host pruned nothing: every session ever composed left a record
retaining its whole disposed subtree, since the fiber holds its config
and that config is the key its EntryTree is stored under.
Prune on the mount path too. Every session takes it, which bounds the
set at one generation of dead records instead of one per session.
A preset is a directory holding one `agent.cordis.yml`. Mounting it under an
agent's scope context during `setup(agentCtx)` gives that one session its own
tools and prompt sections while every other live session keeps its own.
No registry gains a tier. `dsh-tools` and `dsh-system-prompt` already file
registrations into the calling context's scope layer, and entry contexts chain
to the context a subtree was plugged into, so a composition mounted under
`agent.ctx` is that agent's alone and unwinds with it.
The mount audits itself because a directly-plugged subtree is absent from
`ctx.loader.entries()` and no boot audit covers it. It rejects an unscoped
target, a row that never became usable, and a row that published a service into
the root service realm — that last one is process-global rather than
per-session, and its collision with the next session surfaces as an unhandled
rejection `setup` never observes, leaving a half-composed agent that looks
healthy. The package invariant re-checks that rule on every service
notification, since a row publishing from a timer would escape a one-shot audit.
Raises the `packages/README.md` word ceiling from 920 to 980: the group table
must enumerate every group, and the new `preset/` row is necessary content.
Design: .agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.md
