Logged, per-agent plan collaboration state with deployment-owned guidance, direct `/plan [message]` entry and `/plan off` exit commands, and the reviewed `exit_plan_mode` exit. Plan mode is soft guidance; sandbox mode and approval policy remain independent enforcement axes.
`plan/mode` (`{ active: boolean }`) is a log-only, whole-value-replace `SessionEventMap` member. `foldPlanMode(events)` returns the last logged value or `false`, so resume, fork, and compaction recover plan state directly from the session log. UIs observe committed flips through `session/event`.
`ctx.planMode.set(agent, active)` commits immediately when the agent is idle — no boundary would arrive until the next prompt, so the standalone `plan/mode` event lands at once — and holds a pending selection for the next in-turn request boundary while the agent is running; it returns which of the two happened (`committed`/`queued`), a `cancelled` reversal, or a `noop`. `get(agent)` returns `{ active, pending? }`, separating the logged state shaping the current step from a user's mid-turn selection. Prompt submission, ordinary continuation, and request-recovery retry are all covered; a changed user selection contributes one plugin-sourced `user/message` notice when the last logged request header described the other state (both commit paths).
While active, `plan:policy` renders the configured `section`. The plugin always registers `exit_plan_mode`, keeping tool schemas stable across the transition; its execute path accepts only active plan mode and leaves it only after an exact user approval through `ctx.userInteraction`.
When `ctx.commands` is composed, the package registers `/plan [message]` and reserves the exact argument `off` for direct exit. Bare `/plan` selects plan mode; any other non-empty argument selects it first and is then submitted through `agent.steer()`, so it becomes the next step's ordinary logged user message under plan guidance. `/plan off` selects inactive without sending model input; it also cancels a pending entry before plan mode reaches a request.
When the composition mounts `ctx.sessionProjections` ([`@deepseek-ai/dsh-session-projection`](../../session-projection/session-projection/README.md)), this package registers the `plan` projection unit under an injected child. The unit folds two event kinds: a `command/run` record named `plan` sets the wanted target (`off` → inactive, anything else → active), and `plan/mode` commits the logged state and clears it; every other event returns the same state reference. `view` derives `{ active, pending }`, where `pending` is true only while an outstanding selection differs from the logged state — a pure replay quantity, so host restarts, other tabs, and cold reads all recover it from the log alone (the `/plan` handler calls `set()` before any failing path, keeping the logged request and the run plane from forking). The key merges into `SessionProjectionMap` from `src/types.ts` (served to host consumers via `./types` and client aggregates via `./client`); 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.
You are in plan mode. Explore and design before presenting the complete
plan through exit_plan_mode.
```
`section` is required and non-empty. Unknown keys fail at load. The package does not accept arbitrary named modes, tool filters, sandbox settings, or approval policy.
`/plan`, `/plan off`, and their terminal results stay outside model history. A non-empty suffix other than the exact `off` argument becomes one trimmed user text block through `agent.steer()` after plan mode is selected. An active `/plan off` selection contributes the standard logged user-switch notice only when the last request header described plan mode; cancelling a pending entry contributes none because no request observed it.
The optional message costs the same history tokens as submitting that text separately; bare `/plan` and `/plan off` add none. A narrated active exit adds the small retained switch notice.
The user block is append-only conversation growth. Entering or leaving plan mode changes the earlier policy section; a narrated exit notice is appended after the reusable request prefix.
The [`exit_plan_mode` schema](../../../docs/tool-catalog.md#deepseek-aidsh-plan-mode) remains available in both states; execution outside plan mode fails, while an approved in-mode review returns the canonical `{ approved: true }` value and renders the existing confirmation text. Rejection remains a failed call carrying review feedback.
- The `exit_plan_mode` review arc (submit → human review → approved flip or rejected feedback) is covered by package tests only; its assembled-application snapshot left with the retired ACP UI scenarios ([automation-only ACP](../../../.agents/notes/implemented/simplification/2026-07-23-acp-automation-only-protocol.md)) and the TUI keyless scenarios exercise only `/plan` entry and `/plan off` exit.
