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refactor: remove request_ctx ContextVar, thread Context explicitly (#2203)

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Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>
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Max Isbey 2026-03-04 13:23:02 +00:00 • committed by GitHub
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docs/migration.md
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@ -288,6 +288,37 @@ app = Starlette(routes=[Mount("/", app=mcp.streamable_http_app(json_response=Tru
**Note:** DNS rebinding protection is automatically enabled when `host` is `127.0.0.1`, `localhost`, or `::1`. This now happens in `sse_app()` and `streamable_http_app()` instead of the constructor.
### `MCPServer.get_context()` removed
`MCPServer.get_context()` has been removed. Context is now injected by the framework and passed explicitly — there is no ambient ContextVar to read from.
**If you were calling `get_context()` from inside a tool/resource/prompt:** use the `ctx: Context` parameter injection instead.
**Before (v1):**
```python
@mcp.tool()
async def my_tool(x: int) -> str:
ctx = mcp.get_context()
await ctx.info("Processing...")
return str(x)
```
**After (v2):**
```python
@mcp.tool()
async def my_tool(x: int, ctx: Context) -> str:
await ctx.info("Processing...")
return str(x)
```
### `MCPServer.call_tool()`, `read_resource()`, `get_prompt()` now accept a `context` parameter
`MCPServer.call_tool()`, `MCPServer.read_resource()`, and `MCPServer.get_prompt()` now accept an optional `context: Context | None = None` parameter. The framework passes this automatically during normal request handling. If you call these methods directly and omit `context`, a Context with no active request is constructed for you — tools that don't use `ctx` work normally, but any attempt to use `ctx.session`, `ctx.request_id`, etc. will raise.
The internal layers (`ToolManager.call_tool`, `Tool.run`, `Prompt.render`, `ResourceTemplate.create_resource`, etc.) now require `context` as a positional argument.
### Replace `RootModel` by union types with `TypeAdapter` validation
The following union types are no longer `RootModel` subclasses:
@ -694,7 +725,7 @@ If you prefer the convenience of automatic wrapping, use `MCPServer` which still
### Lowlevel `Server`: `request_context` property removed
The `server.request_context` property has been removed. Request context is now passed directly to handlers as the first argument (`ctx`). The `request_ctx` module-level contextvar is now an internal implementation detail and should not be relied upon.
The `server.request_context` property has been removed. Request context is now passed directly to handlers as the first argument (`ctx`). The `request_ctx` module-level contextvar has been removed entirely.
**Before (v1):**