fix(scope): close remaining ownership boundaries

packages/core/agent/README.md

@@ -20,7 +20,7 @@ The scoped-registration surface: `Agent.ctx` is the agent's scope context (`dsh-
 Agent *creation* is provided by the plugin implementing `AgentFactory` (`dsh-agent-loop`), registered via `setFactory`. This keeps creation on the `dsh-agent` interface so consumers (UI, the ACP bridge) program against `ctx.agents` without depending on the concrete loop package.
 
 - `ctx.agents.setFactory(factory: AgentFactory): () => Promise<void> | void` — register the creation factory (the loop calls this on construction). Throws on a second factory; the slot clears on dispose.
-- `ctx.agents.create(options: CreateAgentOptions): Promise<AgentHandle>` — snapshot caller-owned IDs/options/metadata/seed, construct and await optional setup while unpublished, insert and announce both session and agent, open the `agent/session-start` driving boundary, then start a new loop on the caller-supplied `sessionId`. Agent/session IDs are reserved across setup; setup rejection or owner unload publishes nothing. Publication is rollback-covered: if a creation listener throws, entries and scope unwind but effects of already-delivered notifications remain observable; an agent whose announcement began emits `agent/disposed` during that rollback. Rejects if no factory is registered.
+- `ctx.agents.create(options: CreateAgentOptions): Promise<AgentHandle>` — snapshot caller-owned IDs/options/metadata and hand the one-read raw seed synchronously to the session boundary for one-pass lossless-JSON materialization, construct and await optional setup while unpublished, insert and announce both session and agent, open the `agent/session-start` driving boundary, then start a new loop on the caller-supplied `sessionId`. Agent/session IDs are reserved across setup; seed rejection, setup rejection, or owner unload publishes nothing. Publication is rollback-covered: if a creation listener throws, entries and scope unwind but effects of already-delivered notifications remain observable; an agent whose announcement began emits `agent/disposed` during that rollback. Rejects if no factory is registered.
 - `ctx.agents.resume(options: ResumeAgentOptions): Promise<AgentHandle>` — snapshot caller-owned IDs/options, load a persisted session ([session persistence](../../../docs/rfc/implemented/architecture/2026-06-14-session-persistence.md)), mint a fresh agent scope, await optional setup while unpublished, then follow the same insert → announce → session-start → loop-start boundary. The IDs are reserved across persistence load and setup; load/setup rejection or owner unload publishes nothing. Rejects if no factory is registered or session persistence is unconfigured.
 
 `AgentHandle = { agent: Agent; dispose(): Promise<void> }`. The disposer is a **capability** — only the holder can tear this agent down. `dispose()` stops the loop, `await`s its exit plus every outstanding idle-injection flush (quiescence — NOT just the `disposed` status flip), unregisters the agent, removes its session from the store, and finally unwinds its scoped world. This order captures every agent-started `session/flush` before the session is detached and keeps scoped listeners alive through those checkpoints. `ctx.agents.get(id)` still returns a bare `Agent` — the handle is only for the OWNER that created it. The ACP bridge and in-process subagent backends are production consumers; config-created agents are owned by the loop fiber and never need a handle.

packages/core/agent/src/index.ts

@@ -48,7 +48,10 @@ export interface CreateAgentOptions {
    * `cwd`/`parentSession`/`seedLength` fields of
    * {@link CreateSessionOptions.meta} in dsh-session (the internal-only
    * `createdAt`, used when reconstructing a persisted session, is deliberately
-   * excluded — a factory caller never sets it).
+   * excluded — a factory caller never sets it). The factory reads this raw
+   * reference once and hands it synchronously to the session boundary, which
+   * rejects an exotic shell and captures each accepted field once before any
+   * asynchronous setup.
    */
   meta?: { cwd?: string; parentSession?: SessionId; seedLength?: number }
   /**
@@ -57,9 +60,11 @@ export interface CreateAgentOptions {
    * prefix so `deriveMessages()`/`lastTurnNumber` continue from it — used by the
    * in-process FORK subagent backend to seed a child with a balanced
    * completed-turn prefix of the parent's log. The prefix MUST be contiguous
-   * from seq 0 and balanced (no open turn/step, no dangling tool-call), or the
-   * session constructor (and the dev-mode invariants replay) reject it. Absent
-   * for a fresh (spawn) child.
+   * from seq 0, carry only lossless-JSON data, and be balanced (no open
+   * turn/step, no dangling tool-call), or the session constructor (and the
+   * dev-mode invariants replay) reject it. The factory passes the raw seed to
+   * the synchronous one-pass validator/copier; it never pre-clones and thereby
+   * sanitizes exotic prototypes. Absent for a fresh (spawn) child.
    */
   seed?: SessionEvent[]
   /** Per-agent options (model, …). */