docs(scope,agent-presets): standing-mount model, parent chain, and the Agent Note

packages/preset/agent-presets/README.md

@@ -2,9 +2,9 @@
 
 English | [中文](README.zh.md)
 
-Per-session agent composition. A **preset** is a directory holding one `agent.cordis.yml`; mounting it under an agent's scope context gives that one session its own tools, prompt sections, and other model-facing contributions, while every other live session keeps its own.
+Per-preset agent composition. A **preset** is a directory holding one `agent.cordis.yml`; the roster mounts it ONCE per process under a standing scope, and each session that names it joins by having its agent scope key parented to the mount's (`dsh-scope`'s parent chain). The mount's tools, prompt sections, and projection units exist exactly once and cover every joined agent — its plugins key their state by Session/Agent, so sessions stay apart inside one shared instance — and a host reader with no agent at all (a cold transcript read) resolves the same standing registrations by preset id.
 
-The mechanism is entirely Cordis: entry contexts chain to the context a subtree was plugged into, and both [`dsh-tools`](../../core/tools/README.md) and [`dsh-system-prompt`](../../core/system-prompt/README.md) file registrations into the calling context's scope layer. Mounting a composition under `agent.ctx` therefore makes it that agent's alone, and unwinds it with the agent, without any new layering in those registries.
+The mechanism is two seams. Entry contexts chain to the context a subtree was plugged into, and both [`dsh-tools`](../../core/tools/README.md) and [`dsh-system-prompt`](../../core/system-prompt/README.md) file registrations into the calling context's scope layer — so the standing mount's contributions land in the PRESET's layer. What carries them to each session is `dsh-scope`'s parent chain: an agent's views resolve `agent → preset → global` (nearest shadowing farthest), and the mount's listeners are admitted for every agent parented under it while a sibling preset's stay deaf.
 
 ## Service: `AgentPresets` (ctx key: `agentPresets`)
 
@@ -13,13 +13,13 @@ Discovery is unmemoized: `list()` and `resolve()` re-read the roots on every cal
 - `ctx.agentPresets.defaultId: string` The preset id mounted when a caller names none.
 - `ctx.agentPresets.list(): Promise<AgentPreset[]>` Every preset the configured roots currently supply, earlier root winning a duplicate id.
 - `ctx.agentPresets.resolve(id?): Promise<AgentPreset>` One preset by id, defaulting to `defaultId`. Throws naming the available ids when no root supplies it.
-- `ctx.agentPresets.mount(agentCtx, id?): Promise<AgentPreset>` Compose one agent from a preset and return the preset that was mounted, for the caller to record.
+- `ctx.agentPresets.mount(agentCtx, id?): Promise<AgentPreset>` Compose one agent from a preset — ensure its standing mount (single-flight) and parent the agent's scope key to it — returning the preset for the caller to record.
 
 `AgentPreset` carries `id` (the directory name), `trust` (`system` or `user`, from the root it was found under), and `path` (the absolute composition file).
 
 ### Where to call `mount()`
 
-The agent factory's `setup(agentCtx)` hook is the one supported call site. Only there is the composition installed while the agent is still unpublished, so a rejected mount rolls the whole creation back rather than leaving a half-composed session. The subtree is owned by `agentCtx`'s fiber, so it unwinds with the agent and the caller receives no disposer.
+The agent factory's `setup(agentCtx)` hook is the one supported call site. Only there is the join installed while the agent is still unpublished, so a rejected composition rolls the whole creation back rather than leaving a half-composed session. The standing subtree is owned by the roster service's own fiber — deliberately its UNTRACED context, because a subtree minted from a traced `this.ctx` resolves every service through the caller's shadow fiber instead of each entry's own inject store — so it survives every agent and unwinds only with the whole tree. A settled mount is permanent for the process: the composition a running session joined must outlive its file changing or disappearing underneath it, so file edits reach only future generations.
 
 ## Config
 
@@ -38,7 +38,7 @@ A directly-plugged subtree is absent from `ctx.loader.entries()`, so no boot aud
 
 **A row that never became usable.** The loader already rejects a row whose module failed to import or whose plugin threw; what remains is a row still waiting for a service the composition never supplies, which the audit names.
 
-**A row that published a service into the root realm.** Such a service is process-global rather than per-session, so the second session mounting the same preset collides with the first. A preset that genuinely owns a service puts it behind an `isolate` realm — entry-local for one session's private instance, or a shared label when several sessions should share one — or the service belongs in the host composition instead.
+**A row that published a service into the root realm.** Such a service is process-global, so the second preset publishing the same name collides with the first, and a host reader would resolve one preset's instance for every session. A preset that genuinely owns a service puts it behind an `isolate` realm — entry-local realms keep two presets' same-named services apart exactly as they once kept two sessions' apart — or the service belongs in the host composition instead.
 
 The package invariant re-checks that last rule on every service notification, because a row that publishes from a timer or an asynchronous continuation would escape the one-shot audit.
 
@@ -48,7 +48,7 @@ Presets are compositions, so a preset is exactly as privileged as the plugins it
 
 ## Model Experience
 
-Indirectly, through the plugins a mounted composition registers, which own every tool schema and prompt section the preset makes visible to its one agent.
+Indirectly, through the plugins a standing composition registers, which own every tool schema and prompt section the preset makes visible to the agents joined to it.
 
 #### KV Cache effect
 
@@ -56,6 +56,7 @@ Prefix-stable for the life of an agent: a composition is installed once, before
 
 ## Known Limitations and Deferred Work
 
-- **A preset cannot be changed on a live agent** — the mount happens once during creation, so switching a running session's composition would mean unwinding its subtree mid-turn, dropping tools the model may already have called. Changing the default affects only sessions created afterwards.
+- **A preset cannot be changed on a live agent** — the join happens once during creation, so switching a running session's composition would strand tools the model may already have called. Changing the default affects only sessions created afterwards.
+- **A standing mount reads its file once per process** — the first session to name a preset fixes its composition until the whole tree unloads; edits reach only future generations, and nothing reclaims a superseded generation while the process lives (bounded by how often compositions are edited, not by sessions).
 - **Display names are the directory id** — a preset carries no manifest, so pickers and settings surfaces show the id until a consumer needs richer metadata.
 - **Root scans are not watched** — every read hits the filesystem instead, which keeps the roster fresh but puts one `readdir` per root on each `list()`.