refactor(agent): remove message metadata channel

packages/core/agent/README.md

@@ -48,7 +48,7 @@ The lifecycle edges have two important local caveats. `agent/created` runs after
 
 Most interception points are cooperative waterfalls returning seam-specific decisions. Turn-scoped asynchronous seams receive one explicit `AbortSignal`, with `signal` immediately before a waterfall's final `next`; listeners may cooperate but must not retain it as authority over another turn. The signal remains authoritative through terminal policy and is retired immediately before `turn/end` publication, so terminal observers and the following durability flush cannot cancel completed turn work. `agent/pre-step` and `agent/post-step` are serial checkpoints around a step's durable work, while `agent/request-error` is the failed-model-request recovery waterfall: it receives the exact error, normalized failure facts, immutable prior-retried facts, and signal after the failed step closes; a retry opens a new numbered step. `agent/turn-stop` is the terminal serial fold: it runs after ordinary continuation and steering folding, and a returned stop remains in force through turn close and flush so later steering cannot create an extra step or turn. Ordinary queued prompts remain intact. Effective broad cancellation first emits the observe-only `agent/cancel-requested` with its resolved typed cause, then clears queues and aborts; notification failures are contained and cannot veto the stop. The [explicit-cancellation decision](../../../.agents/notes/implemented/architecture/2026-07-16-explicit-turn-cancellation.md) owns signal lifetime; the [agent-scope runtime-design Agent Note](../../../.agents/notes/implemented/architecture/2026-07-12-agent-scope-runtime-design.md#three-execution-boundaries-are-deliberately-one-way) owns scoped dispatch and terminal settlement.
 
-`PromptDecision.additionalContexts` is an array so every context keeps its own source, metadata, and placement. `SendOptions.contexts` binds the same shape to one queued message before prompt interception: the default allow decision carries it forward, while a blocked prompt records no context. Absent or `separate` placement writes an independent injected `user/message` (plugin/goal source); `prompt-prefix` writes the context, `## My request:` delimiter, and effective prompt into one `user/message` or `steering/message`, whose model-hidden envelope retains the direct prompt and context descriptors for human replay. A listener that wraps a downstream allow preserves its `content` and `additionalContexts` unless it intentionally replaces either field; the returned allow is authoritative. A `ContinuationDecision` reason is narrower: it becomes a `steering/message` without attached context metadata.
+`PromptDecision.additionalContexts` is an array so every context keeps its own source and placement. `SendOptions.contexts` binds the same shape to one queued message before prompt interception: the default allow decision carries it forward, while a blocked prompt records no context. Absent or `separate` placement writes an independent injected `user/message`; `prompt-prefix` writes the context, `## My request:` delimiter, and effective prompt into one `user/message` or `steering/message`, whose model-hidden envelope retains the direct prompt and context sources for human replay. A listener that wraps a downstream allow preserves its `content` and `additionalContexts` unless it intentionally replaces either field; the returned allow is authoritative. A `ContinuationDecision` reason is narrower: it becomes a `steering/message` without attached contexts.
 
 Turn and step boundaries and the model token stream are durable `session/event` facts rather than mirrored `agent/*` notifications. Consumers read `turn/*`, `step/*`, and `assistant/chunk` from the session feed; tool policy and outcome observation belong to the complete pipeline documented by [`dsh-tools`](../tools/README.md).
 
@@ -59,7 +59,7 @@ The handle every plugin programs against:
 - `agent.send(content, options?)` — the one delivery primitive over the (`target` × `wakeup`) matrix; `Agent` is an abstract class whose `followup`/`steer`/`inject` aliases are fixed-preset delegates to it. It returns the accepted message's opaque `AgentMessageId`, which the message's `agent/inbox/enqueue`/`dequeue`/`discard` events carry so a caller can correlate a queued item with its lifecycle. `target: 'next-turn'` (default) queues one independent FIFO item that, if claimed, becomes the sole ordinary message in its turn; `wakeup` (default `true`) wakes a parked driver, while `wakeup: false` queues without waking. `target: 'next-step'` with `wakeup: true` submits steering, and with `wakeup: false` injects durable context without running the model. Omitting `options.source` attests direct human input as `{ kind: 'user' }` (injection defaults to `{ kind: 'plugin', plugin: '' }`) and may authorize policy consumers, so plugins, schedulers, and other non-human producers provide their own source. Content, resolved source, and `options.contexts` become one detached, deeply frozen lossless-JSON record before `agent/inbox/enqueue` and enqueue; invalid data throws synchronously, and caller or notification-listener in-place mutation cannot change the log or model input. After admission, separate contexts become injected `user/message` events, while prompt-prefix contexts are baked before the effective request in the same `user/message`; a block or replacement of the default additional-context decision can discard them. The [one-send-one-turn Agent Note](../../../.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.md) owns the turn rationale.
 - `agent.followup(content, options?)` — the `next-turn`/wakeup preset of `send()`: queue an ordinary follow-up turn and wake the driver.
 - `agent.steer(content, options?)` — the `next-step`/wakeup preset: while running, queue steering for the next checkpoint without dispatching `agent/prompt-submit`; when idle, delegate to a woken follow-up. Attached contexts remain in the same frozen record; separate contexts append immediately after the steering event, while prompt-prefix contexts are baked into that steering event. Both survive late-steering conversion to queued input and disappear with their message on cancellation or terminal discard. Policy can still stop before another step; after turn close and its checkpoint, remaining steering becomes later queued input unless terminal turn policy, cancellation, or disposal discards it.
-- `agent.inject(content, options?)` — the `next-step`/no-wakeup preset: accept detached in-session context without running the model; the next request sees its `user/message` (default plugin source) with `content` rendered verbatim as a user-role message. `options.meta` persists opaque JSON state without rendering it. While a turn is open it joins that turn, deferring FIFO while the current tool batch executes and draining before turn close if execution is interrupted; while idle it is wrapped in a one-shot `injection` turn and durability checkpoint ([the turn-enclosure invariant](../../../.agents/notes/implemented/architecture/2026-06-15-turn-enclosure-invariant.md)). Injection bypasses the FIFOs and emits no `agent/inbox/*` event.
+- `agent.inject(content, options?)` — the `next-step`/no-wakeup preset: accept detached in-session context without running the model; the next request sees its `user/message` with `content` rendered verbatim as user-role input and provenance carried entirely by `source`. While a turn is open it joins that turn, deferring FIFO while the current tool batch executes and draining before turn close if execution is interrupted; while idle it is wrapped in a one-shot `injection` turn and durability checkpoint ([the turn-enclosure invariant](../../../.agents/notes/implemented/architecture/2026-06-15-turn-enclosure-invariant.md)). Injection bypasses the FIFOs and emits no `agent/inbox/*` event.
 - `agent.cancel(cause, options?)` — cancel the active turn and, unless `options.keepInbox`, ALL pending work. Callers must choose the `user | parent` cause explicitly; an active holder copies its discriminant into a detached frozen signal reason before aborting. An effective call emits `agent/cancel-requested` with the cause before clearing queued and steering work; dropped items are reported on `agent/inbox/discard`, and observers may synchronize state but cannot veto cancellation. `keepInbox: true` aborts the turn but preserves queued and steering items (no discard, and un-started work is not dropped). The same-process typed seam adds no runtime validation or compatibility fallback for untyped callers. Repeated active-turn cancellation is first-wins for the signal, and idle cancellation is a safe no-op with no notification. ACP maps to `user`, while in-process parent propagation maps to `parent`. The cause is runtime-only; durable `turn/end` stays coarse `aborted`.
 - `agent.whenIdle()` — resolve once the agent reaches quiescence after settling out of `running` (idle → immediately; disposed → awaits the loop exit). A non-owner's quiescence-observation hook: it observes the work settling WITHOUT tearing the agent down. Teardown is separate — a lifecycle owner stops and unregisters via `AgentHandle.dispose()`, which awaits the loop exit directly.
 - `agent.session`, `agent.status`, `agent.options`, `agent.id`

packages/core/agent/src/types.ts

@@ -26,7 +26,7 @@ import type { Context } from 'cordis'
 import type { Branded } from '@deepseek-ai/dsh-brand'
 import type { Scoped } from '@deepseek-ai/dsh-scope'
 import type { ContentBlock, LlmCallConfig, LlmFailure, MessageSource } from '@deepseek-ai/dsh-llm'
-import type { JsonValue, Session, SessionId } from '@deepseek-ai/dsh-session'
+import type { Session, SessionId } from '@deepseek-ai/dsh-session'
 import type {} from '@deepseek-ai/dsh-system-prompt'
 declare module '@deepseek-ai/dsh-system-prompt' {
   interface AssembleContext {
@@ -78,8 +78,6 @@ export interface SendOptions {
    * records them directly at its next checkpoint.
    */
   contexts?: HookContext[]
-  /** Opaque JSON state retained on the durable message but hidden from the model. */
-  meta?: JsonValue
 }
 
 /** Options accepted by the fixed-preset aliases, which own `target` and `wakeup`. */
@@ -106,9 +104,7 @@ export function AgentMessageId(id: string): AgentMessageId {
  * message's enqueue, dequeue, and discard events. Source defaults are already
  * applied, so these are the exact values the item was accepted with. `steering`
  * is true for a `next-step` item drained between steps; a `next-turn` item is
- * claimed at a turn boundary. `SendOptions.meta` is intentionally omitted: it is
- * durable model-hidden state that lands on the eventual `user/message`/
- * `steering/message`, not live-event routing data.
+ * claimed at a turn boundary.
  */
 export interface AgentMessage {
   /** The id `send` returned for this message. */
@@ -150,8 +146,6 @@ export interface HookContext {
    * request delimiter to the same user-role message as its attached prompt.
    */
   placement?: 'separate' | 'prompt-prefix'
-  /** Opaque JSON state retained in the session event but hidden from the model. */
-  meta?: JsonValue
 }
 
 /**
@@ -414,7 +408,7 @@ declare module 'cordis' {
      * @param step - the step whose request this is.
      * @param signal - the current turn's explicit abort signal.
      * Scope-filtered dispatch (`@deepseek-ai/dsh-scope`): agent-scoped listeners receive only that agent.
-     * @mode compose
+     * @mode waterfall
      */
     'agent/request'(this: Scoped<Agent>, agent: Agent, turn: number, step: number, signal: AbortSignal, next: () => Promise<LlmCallConfig>): Promise<LlmCallConfig>
     /**