ticket: define system reminder lane

work-items/open/20260527-000020-system-reminder-injection-generalization/item.md

@@ -1,28 +1,69 @@
 ---
 id: 20260527-000020-system-reminder-injection-generalization
 slug: system-reminder-injection-generalization
-title: system-reminder 注入機構の汎用化（2件目の利用者が出た時に検討。タグ形式 `<system-reminder>...</system-reminder>` の規約は session-todo-reminder で先行確立。注入された Item は worker.history に append する方針）
+title: Generalize system-reminder history append lane
 status: open
 kind: task
 priority: P2
-labels: [migrated]
+labels: [pod, llm-worker, history, system-reminder]
 created_at: 2026-05-27T00:00:20Z
-updated_at: 2026-05-27T00:00:20Z
+updated_at: 2026-05-29T04:46:00Z
 assignee: null
 legacy_ticket: null
 ---
 
-## Migration reference
-
-- legacy_ticket: null
-- migrated_from: TODO.md / tickets directory migration on 2026-05-27
-
-# system-reminder 注入機構の汎用化（2件目の利用者が出た時に検討。タグ形式 `<system-reminder>...</system-reminder>` の規約は session-todo-reminder で先行確立。注入された Item は worker.history に append する方針）
-
 ## Background
 
-This work item was migrated from an unfinished TODO.md entry that did not have a dedicated legacy ticket file.
+`session-todo-reminder` established the first concrete `<system-reminder>...</system-reminder>` user: Task inactivity reminders are appended through `pending_history_appends` so the reminder is persisted in `worker.history` before the next LLM request. This follows the context-processing rule that new non-volatile input must be appended to history rather than injected only into request context.
+
+The current implementation should now be generalized so future reminder producers do not each hand-roll XML tags, `SystemItem` construction, source labeling, cooldown/priority plumbing, or history-append integration.
+
+This ticket is about making the system-reminder append lane a small typed facility. It is not about adding new reminder policies beyond existing Task reminders.
+
+## Requirements
+
+- Introduce a typed internal representation for pending system reminders.
+  - text/body
+  - source/kind, e.g. task inactivity
+  - optional priority/order key if needed
+  - helper that renders the body inside `<system-reminder>...</system-reminder>` exactly once
+- Route reminders through the existing `Interceptor::pending_history_appends` lane.
+  - The final result must still be `Item::System(SystemItem { kind: InvokeKind::SystemReminder, ... })` or equivalent current protocol type.
+  - The reminder must be appended to `worker.history`; do not introduce hidden request-only context injection.
+- Refactor `session-todo-reminder` to use this typed helper/facility.
+  - Task reminder behavior, thresholds, cooldown, and tests should remain unchanged.
+  - The helper should prevent double-wrapping if the body is already tagged, or the API should make double-wrapping impossible.
+- Keep `Notify` / `PodEvent` behavior unchanged.
+  - Do not merge raw notify and system reminder semantics.
+  - If they share buffering mechanics, keep the public behavior and rendered tags distinct.
+- Keep ordering deterministic.
+  - If multiple reminder producers are added later, ordering should be explicit or stable.
+  - For now, existing Task reminder order relative to Notify/PodEvent should be preserved unless there is a clear reason to change it.
+- Add docs/comments near the facility explaining the rule:
+  - system reminders are durable input and must be appended through history.
+  - they are not transient UI notices.
+  - they are not prompt-cache/context-only injections.
 
 ## Acceptance criteria
 
-- Define the concrete requirements before implementation.
+- There is a typed system-reminder helper/facility rather than ad-hoc string construction in Task reminder code.
+- Task inactivity reminders still appear as `<system-reminder>...</system-reminder>` in `pending_history_appends` output.
+- The helper emits `InvokeKind::SystemReminder` / current system-reminder item kind.
+- Existing Task reminder tests continue to pass.
+- New focused tests cover:
+  - rendering wraps body once.
+  - source/kind is retained or observable where appropriate.
+  - Task reminder uses the helper and remains history-append based.
+  - no hidden context-only injection path is introduced.
+- `cargo fmt --check`
+- `cargo check -p pod -p llm-worker -p session-store`
+- Relevant focused tests, e.g. `cargo test -p pod reminder --no-default-features`.
+
+## Out of scope
+
+- Adding a second reminder policy.
+- Changing Task reminder thresholds/cooldown.
+- Changing Notify/PodEvent user-visible behavior.
+- UI actionbar notices.
+- Prompt text changes.
+- Generic notification center or reminder scheduling service.