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Remove Tasks (SEP-1686) from the SDK (#2714)

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Max 2026-06-02 17:27:05 +01:00 • committed by GitHub
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docs/migration.md
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@ -595,7 +595,7 @@ The `RequestContext` class has been split to separate shared fields from server-
**`RequestContext` changes:**
- Type parameters reduced from `RequestContext[SessionT, LifespanContextT, RequestT]` to `RequestContext[SessionT]`
- Server-specific fields (`lifespan_context`, `experimental`, `request`, `close_sse_stream`, `close_standalone_sse_stream`) moved to new `ServerRequestContext` class in `mcp.server.context`
- Server-specific fields (`lifespan_context`, `request`, `close_sse_stream`, `close_standalone_sse_stream`) moved to new `ServerRequestContext` class in `mcp.server.context`
**Before (v1):**
@ -861,7 +861,7 @@ server = Server("my-server", on_list_tools=handle_list_tools, on_call_tool=handl
**Key differences:**
- Handlers receive `(ctx, params)` instead of the full request object or unpacked arguments. `ctx` is a `ServerRequestContext` with `session`, `lifespan_context`, and `experimental` fields (plus `request_id`, `meta`, etc. for request handlers). `params` is the typed request params object.
- Handlers receive `(ctx, params)` instead of the full request object or unpacked arguments. `ctx` is a `ServerRequestContext` with `session` and `lifespan_context` fields (plus `request_id`, `meta`, etc. for request handlers). `params` is the typed request params object.
- Handlers return the full result type (e.g. `ListToolsResult`) rather than unwrapped values (e.g. `list[Tool]`).
- The automatic `jsonschema` input/output validation that the old `call_tool()` decorator performed has been removed. There is no built-in replacement — if you relied on schema validation in the lowlevel server, you will need to validate inputs yourself in your handler.
@ -872,7 +872,7 @@ All handlers receive `ctx: ServerRequestContext` as the first argument. The seco
| v1 decorator | v2 constructor kwarg | `params` type | return type |
|---|---|---|---|
| `@server.list_tools()` | `on_list_tools` | `PaginatedRequestParams \| None` | `ListToolsResult` |
| `@server.call_tool()` | `on_call_tool` | `CallToolRequestParams` | `CallToolResult \| CreateTaskResult` |
| `@server.call_tool()` | `on_call_tool` | `CallToolRequestParams` | `CallToolResult` |
| `@server.list_resources()` | `on_list_resources` | `PaginatedRequestParams \| None` | `ListResourcesResult` |
| `@server.list_resource_templates()` | `on_list_resource_templates` | `PaginatedRequestParams \| None` | `ListResourceTemplatesResult` |
| `@server.read_resource()` | `on_read_resource` | `ReadResourceRequestParams` | `ReadResourceResult` |
@ -1039,37 +1039,11 @@ from mcp.server import ServerRequestContext
# but None in notification handlers
```
### Experimental: task handler decorators removed
### Experimental Tasks support removed
The experimental decorator methods on `ExperimentalHandlers` (`@server.experimental.list_tasks()`, `@server.experimental.get_task()`, etc.) have been removed.
Tasks (SEP-1686) have been removed from the MCP specification and are no longer part of this SDK. The `mcp.client.experimental`, `mcp.server.experimental`, `mcp.shared.experimental`, and `mcp.server.lowlevel.experimental` modules have been removed, along with all `Task*` types, the `tasks` capability fields, `Tool.execution`, and the `experimental` properties on `ClientSession`, `ServerSession`, `Server`, and `ServerRequestContext`.
Default task handlers are still registered automatically via `server.experimental.enable_tasks()`. Custom handlers can be passed as `on_*` kwargs to override specific defaults.
**Before (v1):**
```python
server = Server("my-server")
server.experimental.enable_tasks()
@server.experimental.get_task()
async def custom_get_task(request: GetTaskRequest) -> GetTaskResult:
...
```
**After (v2):**
```python
from mcp.server import Server, ServerRequestContext
from mcp.types import GetTaskRequestParams, GetTaskResult
async def custom_get_task(ctx: ServerRequestContext, params: GetTaskRequestParams) -> GetTaskResult:
...
server = Server("my-server")
server.experimental.enable_tasks(on_get_task=custom_get_task)
```
Tasks are expected to return as a separate MCP extension in a future release.
## Deprecations