Plan Tool

Shared persistent scratchpad for multi-agent collaboration.

Overview

The plan tool gives agents a shared, persistent scratchpad of named documents. Any agent in a multi-agent config that loads the plan toolset can read and write the same plans, and those plans survive across sessions. This makes it straightforward to wire a planner agent that sketches work and one or more executor agents that consume it without any custom tool wiring.

Plans are stored as JSON files in the Docker Agent data directory (~/.cagent/plans/ by default). Agents that share a process serialize on a single mutex, and every write or delete additionally holds an advisory lock on a sentinel file in the plans directory, so writers in separate Docker Agent processes are serialized too: concurrent edits can never silently overwrite each other, and a stale revision always fails with a deterministic version conflict. Writes are atomic (temp file + rename), so a reader never observes partial content.

Configuration

toolsets:
  - type: plan

No additional options are required. All agents that include type: plan in their toolsets share the same plans.

Available Tools

Cheap edits with file-based revisions

Re-sending a whole plan on every revision is expensive. The file-based tools let an agent edit a plan without paying input-token cost for its body:

1. export_plan_to_file writes the current plan content to a path. The content is written to disk and is not returned.
2. The agent edits that file in place with its filesystem tools.
3. update_plan_from_file commits the file's new contents as the next revision.

Free-form status

Each plan carries a free-form status string. There is no fixed vocabulary: define your own in the system prompt (e.g. idle, in-progress, blocked, done, canceled). Read and write it independently of the body with get_plan_status and set_plan_status, or pass status to write_plan and update_plan_from_file. The TUI surfaces the status next to the plan title.

Optimistic locking

When several sessions edit the same plan, concurrent writes could silently overwrite each other. Every read returns a revision number; pass the value you last read as last_known_revision to write_plan, update_plan_from_file, set_plan_status, or delete_plan. If the plan changed since (its current revision no longer matches), the write is rejected with a version-conflict error and the caller should re-read the plan and retry. The revision check and the write happen under the storage's cross-process file lock, so the conflict is detected reliably even when the competing writer runs in a different Docker Agent process. Omit last_known_revision to write unconditionally (last writer wins).

Plan Names

Plan names must match the pattern [a-z0-9][a-z0-9_-]* (lowercase letters, digits, -, _). This is enforced structurally so two different inputs can never collapse onto the same file and path-traversal is impossible by construction.

Plan Fields

Each plan document contains:

Example

Two agents collaborate on a shared plan — the architect drafts it and the builder refines it:

agents:
  root:
    model: anthropic/claude-sonnet-4-5
    description: Coordinator
    instruction: |
      Route work between the architect and the builder.
    handoffs: [architect, builder]

  architect:
    model: anthropic/claude-sonnet-4-5
    description: Drafts high-level plans
    instruction: |
      Use list_plans and read_plan to inspect existing plans, then write_plan
      to create or revise one. Always read before writing. When done, hand off
      to the builder.
    toolsets:
      - type: plan
    handoffs: [builder]

  builder:
    model: openai/gpt-4o
    description: Adds implementation steps to plans
    instruction: |
      Read the architect's plan with read_plan, then use write_plan to append
      concrete implementation steps. Always read before writing. When done,
      hand off back to root.
    toolsets:
      - type: plan
    handoffs: [root]

See examples/shared_plan.yaml for a complete working example.

Error Handling

• read_plan returns a distinct "not found" error when a plan does not exist, as opposed to any other I/O error, so callers can tell "plan missing" from "plan unreadable."
• list_plans skips corrupt entries but reports them in a warnings field so an agent can detect and recover from a bad state (e.g., by calling delete_plan).
• delete_plan can remove a corrupt plan to recover from a bad state.

Managing plans from the host

Shared plans can also be inspected and managed outside a session with the docker agent plans command group: list, get, create, update, set status, export, and delete — with the same optimistic-locking semantics as the tools (--expected-version guards a write and a stale version fails with exit code 3; --force writes unconditionally). Session plans (the per-session "draft, review, execute" plan) can be listed, read, and exported through the same commands but stay owned by their session and cannot be mutated from the host.

$ docker agent plans list
$ docker agent plans get release > plan.md
$ docker agent plans update release --file ./plan.md --expected-version 1

The /plans browser in the TUI

Inside the full-screen TUI, the /plans slash command (also in the Ctrl+K command palette) opens a plan browser over the same store the agents use, so changes made by agents mid-session appear immediately. The list shows every shared plan plus the current session's session plan, with each plan's scope, identity (name, or session ID for the session plan), status, version (- for the unversioned session plan), last update time, and title.

Keybindings:

Every mutation is guarded by the version shown on screen (the same optimistic locking as last_known_revision): if an agent changed the plan in the meantime, the write is rejected, a notification reports the current version, the newer content is left intact and re-read into the browser, and an edit draft is kept in a temp file so nothing is lost. Session plans are read-only here — status, edit, and delete report why instead of attempting the write. The browser also refreshes live when agents in the same process write, re-status, or delete plans (and when this session's agent updates its session plan); in the lean TUI, which has no overlays, /plans is unavailable.