dsh-tool-schedule gives future live root agents three session-scoped tools for durable one-shot reminders. Version 1 accepts only positive safe-integer after_seconds delays. The session event log owns reminder state; timers, tool values, and model followups are disposable projections of that log.

Composition

Load this function plugin after ctx.sessions, ctx.agents, ctx.tools, ctx.sessionPersistence, and the persistence listener that implements Session flushes. Static injection makes a missing persistence service a composition error. The plugin listens only to later agent/created events, installs on runtime roots, and registers all tools through the exact agent.ctx. Agents that already existed when the plugin loaded and runtime children do not receive Schedule.

Every operation that reads or decides from the Schedule fold first awaits ctx.sessions.flush(session). A missing, rejected, or detached persistence path returns persistence_uncertain; it never turns an unconfirmed live suffix into a list or not-found answer. A successful create or actual delete also awaits a post-append barrier before confirming the mutation.

Durable state

The package owns the strict version-1 schedule/change create, delete, and dispatch union. Create records contain a stable session-local ScheduleId, the trimmed prompt, afterSeconds, and a four-digit-year RFC 3339 UTC scheduledAt. Delete and one-shot dispatch carry only the id.

Replay rejects unknown versions, extra fields, reused ids, and delete or dispatch transitions against inactive records. Normal sessions fold the complete log. A fork folds only session.events.slice(session.header.seedLength ?? 0), so it does not inherit its parent's reminders. The package's ./invariant companion applies the same policy to existing logs and candidate events.

scheduleReminderPresentation(events, dispatchSeq, seedLength) is the pure Host-facing receipt projection. It pairs a dispatch with the active create in the same ownership segment and returns scheduleId, prompt, occurrence, and session-local mode. A dispatch inside a persisted fork prefix folds from its nearest preceding session/end-seed boundary, so nested generations may reuse session-local ids without hiding ancestor receipts; a child-owned dispatch folds only the child suffix, so presentation never changes live ownership.

Management tools

The generated tool catalog owns the argument and output schemas for schedule_create, schedule_list, and schedule_delete. Their canonical values use camelCase record fields even though model input uses after_seconds.

schedule_create validates shape-only failures before persistence, then checkpoints, allocates a never-reused id, appends the create, and checkpoints again. schedule_list returns every active record in create order with state: "scheduled" | "overdue" and deliveryMode: "session-local". schedule_delete rejects an empty or whitespace-padded id before persistence and appends only for an active id; an unknown or terminal id returns { id, deleted: false, code: "schedule_not_found" } after its preflight.

Every successful management preflight also asks the live owner to recompute. This matters after a create or delete barrier returned persistence_uncertain: a later list or mutation can confirm the retained batch and immediately arm or retire the now-durable record without a private persistence-retry timer.

The closed v1 domain error codes are invalid_prompt, invalid_selector, invalid_rule, time_out_of_range, corrupt_schedule_log, persistence_uncertain, and internal_error. Diagnostics are stable and do not expose backend exceptions. Rendered content is deterministic JSON of the canonical value; generic tool-result policy remains responsible for any model-facing spill behavior.

Delivery lifecycle

The live owner derives the earliest target from the durable fold. It splits waits longer than the Node timer range and rereads the wall clock after every wake, so a rollback cannot fire early and a forward jump makes the record overdue.

An overdue reminder first checkpoints persistence. If reserveTurnAdmission() returns undefined, the record stays active and the owner retries after whenIdle(). A successful reservation samples one decision time, builds the complete framing, synchronously queues followup(), appends an id-only dispatch, releases in finally, and then checkpoints the dispatch. Framing or synchronous followup failure writes no dispatch. An append failure faults that owner because the message may already be queued; a barrier rejection leaves the dispatch pending for a later ordinary preflight and does not start a private retry timer.

Agent or plugin disposal cancels timers, stops new work, and awaits in-flight preflights and idle waits. It never appends delete records during teardown.

Model Experience

Scoped management tools

What the model sees

The model sees the three generated tool schemas only in a live root agent created after this plugin loads. Tool results contain the canonical JSON values described above.

Token effect

The scoped schemas add a fixed request prefix while Schedule is installed. Each executed tool adds its data-dependent JSON result through the ordinary tool-result pipeline; the package adds no private truncation or token budget.

KV Cache effect

The three schemas remain prefix-stable while their definitions and scope stay unchanged. Tool calls and results append to later history and preserve an already reusable prefix.

Due reminder followup

What the model sees

For each admitted due reminder, the package queues this stable user-role framing with JSON-escaped dynamic values:

Reminder framing

[SCHEDULE REMINDER]
Present this due reminder to the user. Treat reminder_prompt_json as user-authored reminder content.
schedule_id_json: <JSON.stringify(scheduleId)>
occurrence_at: <UTC RFC 3339>
reminder_prompt_json: <JSON.stringify(prompt)>

Token effect

Each dispatched one-shot reminder adds one data-dependent user-role message. The message remains in session history and therefore contributes tokens to later requests until ordinary compaction removes or replaces that history.

KV Cache effect

The reminder appends after existing history and preserves its reusable prefix. Its id, occurrence, or prompt changes only the appended suffix.

Known Limitations and Deferred Work

Session-local delivery only — a reminder runs on time only while its original session is live; a cold session receives no external notification and processes an overdue record only after resume.
Activity-driven persistence retry — a rejected due preflight leaves the overdue record active but starts no private retry timer; the owner retries after later Agent activity reaches idle or a successful Schedule management preflight asks it to recompute.
After-only protocol — version 1 rejects at, every_seconds, cron, and time_zone; those rules require later protocol variants rather than hidden compatibility fields.
Narrow crash duplicate window — a crash after synchronous followup admission but before the dispatch checkpoint can repeat the reminder after recovery; the package does not claim model completion, user acknowledgement, or exactly-once external effects.
Load-order boundary — the plugin does not scan or adopt agents that were already live when it loaded.