* Studio: persistent stdio MCP sessions so server state survives across tool calls
call_tool_sync spawned a fresh stdio subprocess per tool call
(keep_alive=False) and tore it down when the call returned, so any stateful
MCP server lost its state between calls: with @playwright/mcp,
browser_navigate opened the page in one subprocess and
browser_take_screenshot ran in a brand-new one, screenshotting about:blank.
Keep one connected client per (command, env) on a dedicated event-loop
thread and reuse it across calls:
- idle sessions are reaped after 5 minutes (in-flight calls excluded) and
everything closes at exit, preserving the old design's no-orphans property
- a dead subprocess is detected via is_connected() and retried once on a
fresh session; tool-level errors leave the session alone
- cancel and timeout semantics are unchanged, and a timed-out call does not
tear the session down
- updating a server's endpoint/env/enabled state or deleting it closes its
live session
- HTTP/SSE servers stay one-shot per call
* address review feedback
* fix stdio session cleanup
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* address review: per-thread MCP scope, close-during-connect and abort races
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* address review: unblock no-limit calls on close, drain borrowers before close, scope closes to url+env
* don't retry sessions closed by config changes, re-verify server row before caching, keep env secrets out of generation keys
* fail fast on connect errors and make the stdio key-lock wait cancellable
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* quote MCP scope parts so IDs with colons can't collide
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* serialize per-session stdio calls, span one timeout budget across connect and call, hash urls in generation keys
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Harden persistent stdio MCP sessions: crash recovery, concurrency, scoping
- Evict a stdio session on any transport-level (non-ToolError) call failure and
do not replay it, so a mid-call subprocess crash can no longer poison the scope.
Never gate liveness on Client.is_connected() (it only reports that a session
object exists, not that the subprocess is alive); add a version-adaptive
dead-transport probe that works on fastmcp 3.0.2 and newer.
- Re-check closed/defunct/config and transport liveness after acquiring the call
lock, and retire a session before releasing the lock, so a queued same-scope
caller never reuses a session that another caller's timeout already retired.
- Force a ProactorEventLoop on Windows so the stdio transport can always spawn
subprocesses regardless of the active event-loop policy.
- Scope stdio sessions per conversation: require thread_id to persist, and tag
the fields so a session_id and a thread_id with the same value cannot collide.
A session_id alone is project-wide, so it now falls back to a safe one-shot
session instead of sharing browser/DB/REPL state across conversations.
- Forward thread_id on the Anthropic Messages path.
- Treat timeout=None as unlimited on connect and the key lock (was capped at 60s).
- Bound the session cache (default 32, override via
UNSLOTH_STUDIO_MAX_STDIO_MCP_SESSIONS) with LRU eviction of idle sessions.
- Run config_check on cache hits, and log a redacted exe#digest label instead of
the raw command so credentials in argv never reach the logs.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Trim the stdio MCP session cache on release and skip close-generation for HTTP servers
Two fixes from review of the persistent stdio session lifecycle:
- Re-enforce the session cap when a session goes idle. A concurrent burst of
distinct-scope calls can overshoot the cap while every cached session is busy
(insert-time eviction only reclaims idle sessions), and the overshoot used to
persist until the 5-minute idle reaper. _release_stdio_session now trims the
idle overshoot back within the cap, without ever evicting an in-flight call.
- close_stdio_sessions() now no-ops for a specific non-stdio (HTTP/SSE) url.
Those transports are never cached as stdio sessions, so calling it on every
HTTP server update or delete used to accrue an unbounded close-generation entry.
Both are covered by regression tests that fail before the change and pass after.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Keep the live stdio MCP session across a display-name rename
The edit dialog resends url, headers, and use_oauth unchanged whenever a
server is saved, so gating the tool-cache invalidation and stdio session
close on field presence dropped the persistent process on a plain rename
or any no-op edit. Gate on a real value change against the stored row so
only a genuine endpoint, auth, or enable change closes the session.
Regression tests: a rename that resends unchanged url/headers/oauth keeps
the session; a real command change still closes it.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Tighten comments in the stdio MCP session lifecycle
Collapse a few verbose comments to fewer lines with the wording preserved,
and drop one that restated the clear_oauth_tokens_async docstring. Comments
only; no code change.
---------
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: danielhanchen <danielhanchen@gmail.com>
601155114d