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Plans are execution strategies for complex tasks that require multiple steps. Agents may share plans with Clients through session/update notifications, providing real-time visibility into their thinking and progress. plan_update carries a plan object with a type discriminator, and every plan format includes a required planId so Clients can track multiple plans independently. The stable plan content type is items. The draft unstable schema also includes additional plan operations while the Plan Operations RFD is in progress.

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Creating Plans

When the language model creates an execution plan, the Agent SHOULD report it to the Client with plan_update.

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Item-Based Plans

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plan.type
string
required
The plan content type.
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plan.planId
PlanId
required
A unique identifier for this plan within the session.
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plan.entries
PlanEntry[]
required
An array of plan entries representing the tasks to be accomplished.

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Unstable Plan Operations

The draft unstable schema includes markdown plans, file-backed plans, and explicit plan removal. These operations are not part of the stable schema yet. Clients using the draft unstable schema MUST tolerate these variants. Tolerating a variant means the Client can deserialize and validate it, then render it, preserve it for replay or proxying, or ignore it.

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Markdown Plans

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File Plans

Plan file URIs MUST be absolute.

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Removing Plans

Agents can remove a plan by sending plan_removed with the plan ID:

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Extensibility

plan.type values can be custom or future variants when Clients can preserve or display them generically. Custom plan content types MUST begin with _; unknown non-underscore plan content types are reserved for future ACP variants. Every plan content variant, including custom or future variants, MUST carry a planId.

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Plan Entries

Each plan entry represents a specific task or goal within the overall execution strategy:
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content
string
required
A human-readable description of what this task aims to accomplish
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priority
PlanEntryPriority
required
The relative importance of this task.
  • high
  • medium
  • low
Custom or future priority values can be used for display hints. Custom priorities MUST begin with _; unknown non-underscore priorities are reserved for future ACP variants.
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status
PlanEntryStatus
required
The current execution status of this task
  • pending
  • in_progress
  • completed
  • cancelled
Custom or future status values can be used when Clients can preserve or display a generic plan-entry state. Custom statuses MUST begin with _; unknown non-underscore statuses are reserved for future ACP variants.

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Updating Plans

As the Agent progresses through the plan, it SHOULD report updates by sending more session/update notifications with the same sessionUpdate: "plan_update" structure and planId. For item-based plans, the Agent MUST send a complete list of all plan entries in each update and their current status. The Client MUST replace the current contents of that plan completely.

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Dynamic Planning

Plans can evolve during execution. The Agent MAY add, remove, or modify plan entries as it discovers new requirements or completes tasks, allowing it to adapt based on what it learns.