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Fix stdio client shutdown bugs and rebuild the stdio test suite (#2773)

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Max 2026-06-05 16:15:43 +01:00 • committed by GitHub
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@ -105,6 +105,46 @@ The `headers`, `timeout`, `sse_read_timeout`, and `auth` parameters have been re
Note: `sse_client` retains its `headers`, `timeout`, `sse_read_timeout`, and `auth` parameters — only the streamable HTTP transport changed.
### `terminate_windows_process` removed
The deprecated `mcp.os.win32.utilities.terminate_windows_process` function has been
removed. Process termination is handled internally by the `stdio_client` context
manager; there is no replacement API. The Windows tree-termination helper
`terminate_windows_process_tree` no longer accepts a `timeout_seconds` argument —
the value was never used (Job Object termination is immediate).
### `stdio_client` no longer kills children of a gracefully-exited server on POSIX
When a server exits on its own after `stdio_client` closes its stdin, background
child processes the server leaves behind are no longer killed on POSIX — their
lifetime is the server's business. The old behavior was a side effect of a shutdown
wait gated on the stdio pipes closing rather than on process exit: a child holding
an inherited pipe made a well-behaved server look hung, so its whole process tree
was killed. (That gating is an asyncio behavior specific to Python 3.11+ — on
Python 3.10 and the trio backend the old wait already resolved on process exit, so
the spurious kill never fired there.) A server that does not exit within the grace
period is still terminated
along with its entire process group. On Windows, children stay in the server's Job
Object and are still killed at shutdown — now deterministically when the job handle
is closed, rather than whenever the handle happened to be garbage-collected.
If you relied on `stdio_client` killing everything the server spawned, make the
server terminate its own children on shutdown (its stdin reaching EOF is the
shutdown signal), or clean up the process tree from the host application after
`stdio_client` exits.
Two related shutdown refinements: `stdio_client` now closes its end of the pipes
deterministically at shutdown, so a surviving child that keeps writing to an
inherited stdout receives `EPIPE`/`SIGPIPE` once the client is gone (previously the
pipe lingered until garbage collection); and a failed write to a server that is
still running now surfaces as a closed connection (`CONNECTION_CLOSED`) on the read
side instead of leaving requests waiting indefinitely.
`terminate_posix_process_tree` now requires the process to lead its own process
group (spawned with `start_new_session=True`); the `getpgid()` lookup and the
per-process terminate/kill fallback are gone. The win32 utilities logger is now
named `mcp.os.win32.utilities` (was `client.stdio.win32`).
### Removed type aliases and classes
The following deprecated type aliases and classes have been removed from `mcp.types`: