# @deepseek-ai/dsh-tool-todo

English | [中文](README.zh.md)

The model-facing `todo_write` tool: the agent's whole task list, replaced wholesale on each call.

## What it does

Registers one tool, `todo_write(todos: [{ content, status }])`, on `ctx.tools`. The model sends the ENTIRE list every call — there are no partial updates or per-item edits. Each call appends a `todo/write` event (the full list snapshot) to the calling agent's session log via `agent.session.append('todo/write', { todos })`; the current list is the most recent such event (last-write-wins on replay).

`status` is one of `pending`, `in_progress`, or `completed`.

## Single owner

The list belongs to the ONE agent session that called the tool. There is no subagent/shared/swarm scope: a non-agent caller (no `exec.agent`) has nowhere to write the list and is rejected. This is a deliberate scope limit — see the Agent Note.

## Validation

Beyond the schema's type/required/enum checks, `execute` rejects an empty or duplicate `content`, more than one `in_progress` task (a coherent plan has at most one task active), and any item key beyond `content`/`status` — an extended item shape (ids, nesting) fails loud instead of silently flattening, keeping the logged snapshot equal to what the model believes it wrote. Ordering and the discipline of keeping the list current are left to the model via the tool description.

## Rendering

The canonical result is `{ todos, counts: { pending, inProgress, completed } }`; its Native renderer returns the compact update acknowledgement. The tool also writes the full `todo/write` session event. UIs subscribe to the event stream and render that durable list themselves: the [TUI app](../../examples/tui-demo) and the [web client](../../client/ui-conversation) show a plan strip (plus a dedicated web tool row) off the standing plan — latest `todo/write` with no later `turn/start` ([display](../../../.agents/notes/implemented/feature/2026-07-23-web-todo-display.md), [lifetime](../../../.agents/notes/implemented/feature/2026-07-28-todo-plan-clears-on-next-turn.md)).

## Session projection

When the composition mounts `ctx.sessionProjections` ([`@deepseek-ai/dsh-session-projection`](../../session-projection/session-projection/README.md)), this package registers the `todos` projection unit under an injected child: `init` = `null` (no write yet), `apply` = take the whole list from each `todo/write` and clear to `null` on each `turn/start` (standing plan; `turn/end` keeps the finished checklist; every other event returns the same state reference), `view` = identity, `stateVersion` = 2. The key merges into `SessionProjectionMap` here (via the interface package's `/types` outlet); the framework drives the unit and carriers serve the value on the history tail page and the `session/projection` push frame. Compositions without the registry are unaffected. Lifetime rationale: [todo plan clears on next turn](../../../.agents/notes/implemented/feature/2026-07-28-todo-plan-clears-on-next-turn.md).

## Export shape

A function/namespace plugin: it exports `name` / `inject` / `apply` and NO default. A stray `export default` would collapse the module via the Loader's `unwrapExports` and drop `inject` (see [docs/postmortem/0001](../../../docs/postmortem/0001-acp-default-export-drops-inject.md)).

## Model Experience

### Tool schema

#### What the model sees

The model sees the generated [`todo_write` schema](../../../docs/tool-catalog.md#deepseek-aidsh-tool-todo).

#### Token effect

Fixed schema cost on every request where the tool is visible.

#### KV Cache effect

Prefix-stable while the definition and visibility are unchanged. Plugin lifecycle or scoped restrictions may invalidate reuse from this schema.

### Tool-call history and result

#### What the model sees

Each assistant tool call retains the entire replacement list in its arguments. Success returns exactly `Updated todo list: <pending> pending, <inProgress> in progress, <completed> completed.` Stable failures are ``Error: invalid todo: `content` must be a non-empty string``, `Error: invalid todos: duplicate content "<content>"`, `Error: invalid todos: at most one task may be in_progress, got <count>`, and `Error: todo_write requires an owning agent session`. The full `todo/write` session event is UI and replay state, not a second model message.

#### Token effect

Token growth scales with every full list the model submits, and those call arguments remain until compaction. The result itself is small and fixed-shape.

#### KV Cache effect

Append-only; newly visible content follows the reusable request prefix and does not invalidate existing KV-cache entries.

## Known Limitations and Deferred Work

- **Single-owner scope only** — the list belongs to the one calling agent session; subagent/shared/swarm scopes are a deliberate cut (see § Single owner), and a non-agent caller is rejected.
- **The item shape is deliberately minimal** — `content` plus three-state `status`; whole-list replacement needs no stable id, priority, or active-form fields.
- **Whole-list replacement is the only operation** — no partial updates, no read-back tool; the model must resend the entire list each call.
