refactor(subagent): drop host-user authority and split lifecycle publication
Remove the host-user continuation capability and the public residency query, then separate the seam's public event payloads from its internal lifecycle control interfaces. `followup()` now takes the exact live direct parent `Agent` instead of a `SubagentAuthority` union. No production adapter ever supplied user authority, so the `UserAuthorityGrant` brand token existed only to stop a forged discriminant from bypassing the direct-parent check — deleting the branch retires the token, its mint method, and that attack surface together. Narrowing `parent` from `Agent | undefined` to `Agent` removes three special cases, including the path where a parentless epoch dispatched its lifecycle events unscoped. Scoped-versus-global dispatch is now decided by the event, not by whether a caller happened to have a parent. `activationState()` had no caller; `ActivationState`, `ActivationObserver`, and `ContinuationHost` are package-private. New `src/lifecycle.ts` owns the contained emitter, the one-shot run observer, and the Activation observer, while `SubagentRunInfo`/`SubagentRunEndInfo` move to `src/types.ts` beside the other consumer-facing contracts. Those payloads are public API — dsh-jsonrpc, hooks-claude, and the package invariant all consume them — whereas the observer is a contract between two in-package collaborators, so they no longer share a home merely for both being lifecycle-shaped. The service keeps ownership of the scope carrier: `scopeTarget()` composes the service's own context filter, so a narrowed stand-in would silently change scope filtering. Also drops now-unused dsh-tasks-local and dsh-tool-tasks dev dependencies, and corrects the README claim that a pre-residency failure emits a terminal edge — that path only ever rethrew.
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@@ -99,7 +99,7 @@ Providers receive exactly this request: one-shot delegation has no service-resol
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## Continuable children and activations
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A **continuable background subagent** is one durable child Session with at most one process-local **Activation** — a residency epoch for a reconstructed child Agent. An Activation is not a request, result, cancellation, or Task boundary: it may execute many FIFO turns and stays resident while descendants it created are still running. The continuation manager owns activation admission, authority, the live ownership graph, cold resume, and child-first disposal; the Agent loop owns all turn ordering and execution. No continuable path creates a Task or an intermediate result-bearing wrapper.
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A **continuable background subagent** is one durable child Session with at most one process-local **Activation** — a residency epoch for a reconstructed child Agent. An Activation is not a request, result, cancellation, or Task boundary: it may execute many FIFO turns and stays resident while descendants it created are still running. The continuation manager owns activation admission, direct-parent authorization, the live ownership graph, cold resume, and child-first disposal; the Agent loop owns all turn ordering and execution. No continuable path creates a Task or an intermediate result-bearing wrapper.
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```text
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persisted Session
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@@ -113,17 +113,17 @@ persisted Session
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`SubagentService.followup()` is the sole continuation-message operation, and routing depends only on Activation residency:
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| Activation state | Sender | `followup` |
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|---|---|---|
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| `running` | parent or user | enqueue in the same Activation |
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| `waiting` | parent or user | wake the same Activation |
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| no Activation | parent or user | cold-resume a new Activation |
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| Activation state | `followup` |
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|---|---|
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| `running` | enqueue in the same Activation |
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| `waiting` | wake the same Activation |
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| no Activation | cold-resume a new Activation |
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`running` means the Agent has an active admission or turn, or waking inbox work; `waiting` means it is quiescent but still owns at least one child Activation that has not completed disposal; `settled` means quiescent with every owned child disposed, at which point the manager disposes the `AgentHandle` and removes the Activation. The manager derives these from Agent quiescence and the owned-child set rather than maintaining a second execution state machine, and `activationState()` reports the current value (`undefined` when no Activation is live).
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`running` means the Agent has an active admission or turn, or waking inbox work; `waiting` means it is quiescent but still owns at least one child Activation that has not completed disposal; `settled` means quiescent with every owned child disposed, at which point the manager disposes the `AgentHandle` and removes the Activation. The manager derives these internal conditions from Agent quiescence and the owned-child set rather than maintaining a second execution state machine.
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The Agent inbox is the only queue. Every continuation message becomes one `Agent.followup()` FIFO turn, so parent and user messages share one observable order and a follow-up cannot redirect a turn already underway. Successful delivery returns the accepted `MessageId`; the existing `agent/inbox/enqueue`, `agent/inbox/dequeue`, and `agent/inbox/discard` events remain the message-lifecycle observations, and the continuation layer defines no subagent-specific delivery route.
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The Agent inbox is the only queue. Every continuation message becomes one `Agent.followup()` FIFO turn, so accepted messages have one observable order and a follow-up cannot redirect a turn already underway. Successful delivery returns the accepted `MessageId`; the existing `agent/inbox/enqueue`, `agent/inbox/dequeue`, and `agent/inbox/discard` events remain the message-lifecycle observations, and the continuation layer defines no subagent-specific delivery route.
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Authority is supplied by a trusted host interaction or an exact live Agent tool context. The parent variant is admitted only when the authenticated Agent is the durable child's direct parent recorded in `SessionHeader.parentSession`. User authority carries an opaque grant that only `SubagentService.userAuthority()` mints, so a caller cannot claim it by writing the discriminant — a plugin holding `ctx.subagents`, including model-generated mount code, would otherwise bypass the direct-parent check for any known child id. `MessageSource` and `senderSessionId` are durable provenance after admission and grant no authority — the optional model-facing tool uses `CoordinatorMessageSource`, while a host adapter uses `{ kind: 'user' }`. User authority may cold-resume a child without loading its historical parent.
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Follow-up authority comes from an exact live Agent tool context. The authenticated Agent must be the durable child's direct parent recorded in `SessionHeader.parentSession`. `MessageSource` and `senderSessionId` are durable provenance after admission and grant no authority; the optional model-facing tool uses `CoordinatorMessageSource`.
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For both operations the caller signal owns lookup, materialization, and admission only until inbox acceptance. Afterwards the manager owns the Activation independently: later caller cancellation neither cancels the accepted turn nor disposes the child, and the seam exposes no public subagent cancellation or steering operation.
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@@ -140,25 +140,6 @@ interface CoordinatorMessageSource {
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}
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```
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```ts type-equiv
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/**
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* Who authorizes one continuable-subagent operation. Authority comes from a
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* trusted host interaction or an exact live Agent tool context; durable
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* {@link MessageSource} provenance never authorizes delivery.
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*/
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type SubagentAuthority =
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/** The exact live parent Agent whose tool context is making the call. */
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| { readonly kind: 'parent'; readonly agent: Agent }
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/**
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* A trusted host adapter acting for the human user. The `grant` must be the
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* exact token {@link SubagentService.userAuthority} minted, so a discriminant
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* alone cannot claim this authority — any plugin holding `ctx.subagents`,
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* including model-generated mount code, could otherwise forge it and bypass
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* the direct-parent check.
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*/
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| { readonly kind: 'user'; readonly grant: UserAuthorityGrant }
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```
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```ts type-equiv
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/** Options for following up with one continuable child. */
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interface SubagentFollowupOptions {
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@@ -179,18 +160,6 @@ interface ContinuableStart {
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}
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```
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```ts type-equiv
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/**
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* The public residency state of one continuable child, derived from Agent
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* quiescence and the owned-child set rather than a second state machine:
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* `running` — the Agent has an active admission or turn, or waking inbox work;
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* `waiting` — the Agent is quiescent but still owns undisposed children;
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* `settled` — quiescent with every owned child disposed, so the manager
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* disposes the `AgentHandle` and removes the Activation.
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*/
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type ActivationState = 'running' | 'waiting' | 'settled'
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```
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The provider participates only in preparing the initial creation spec, where `spawn` and `fork` differ. Its returned spec carries only detached provider-specific creation inputs — today the optional parent-history seed — and no Agent, `AgentHandle`, prompt delivery, result, disposal, or resume operation. Cold resume does not dispatch through a provider at all: the manager folds the generic descriptor, calls `ctx.agents.resume()` through the same activation-owner scope, and submits the waiting turn.
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```ts type-equiv
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