Progress changedspecification/2026-07-28/basic/patterns/progress

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# Progress

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The Model Context Protocol (MCP) supports optional progress tracking for long-running
operations through notification messages. The server **MAY** send progress notifications
to report the status of requests the client has issued.

## Progress Flow

When a client wants to *receive* progress updates for a request, it includes a
`progressToken` in the request metadata.

* Progress tokens **MUST** be a string or integer value
* Progress tokens can be chosen by the client using any means, but **MUST** be unique
  across all active requests.

```json theme={null}
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "some_method",
  "params": {
    "_meta": {
      "progressToken": "abc123"
    }
  }
}
```

The server **MAY** then send progress notifications containing:

* The original progress token
* The current progress value so far
* An optional "total" value
* An optional "message" value

```json theme={null}
{
  "jsonrpc": "2.0",
  "method": "notifications/progress",
  "params": {
    "progressToken": "abc123",
    "progress": 50,
    "total": 100,
    "message": "Reticulating splines..."
  }
}
```

* The `progress` value **MUST** increase with each notification, even if the total is
  unknown.
* The `progress` and the `total` values **MAY** be floating point.
* The `message` field **SHOULD** provide relevant human readable progress information.

## Behavior Requirements

1. Progress notifications **MUST** only reference tokens that:
   * Were provided in an active request
   * Are associated with an in-progress operation

2. Servers receiving a request with a progress token **MAY**:
   * Choose not to send any progress notifications
   * Send notifications at whatever frequency they deem appropriate
   * Omit the total value if unknown

```mermaid theme={null}
sequenceDiagram
    participant Client
    participant Server

    Note over Client,Server: Request with progress token
    Client->>Server: Method request with progressToken

    Note over Client,Server: Progress updates
    Server-->>Client: Progress notification (0.2/1.0)
    Server-->>Client: Progress notification (0.6/1.0)
    Server-->>Client: Progress notification (1.0/1.0)

    Note over Client,Server: Operation complete
    Server->>Client: Method response
```

## Implementation Notes

* Clients and servers **SHOULD** track active progress tokens
* Both parties **SHOULD** implement rate limiting to prevent flooding
* Progress notifications **MUST** stop after completion

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