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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"session_idle_timeout is not exposed via streamable_http_app() and can cancel active requests","articleBody":"## Summary\n\nThe `session_idle_timeout` feature currently has two linked problems:\n\n1. it is implemented on `StreamableHTTPSessionManager` but not exposed through the canonical `streamable_http_app()` API surface\n2. it can terminate a session while a request is actively in flight\n\n## Why this looks like a bug\n\nPR #1994 / #2022 describe `session_idle_timeout` as a way to reap sessions that receive **no HTTP requests** for the configured duration.\n\nThat implies two things:\n\n- users of the high-level StreamableHTTP API should be able to configure it without dropping down to manual session-manager wiring\n- a request that is currently being processed should not count as an idle session\n\nToday neither of those expectations holds.\n\n## Problem 1: not exposed by `streamable_http_app()`\n\n`StreamableHTTPSessionManager(...)` accepts `session_idle_timeout`, but:\n\n- `mcp.server.lowlevel.server.Server.streamable_http_app(...)` does not\n- `mcp.server.mcpserver.server.MCPServer.streamable_http_app(...)` does not\n\nSo the recommended high-level API cannot configure a supported session-manager feature.\n\n### Reproduction\n\n```python\nfrom mcp.server import Server\n\napp = Server(\"demo\")\napp.streamable_http_app(session_idle_timeout=30)\n```\n\n### Observed behavior\n\n```python\nTypeError: Server.streamable_http_app() got an unexpected keyword argument 'session_idle_timeout'\n```\n\n## Problem 2: active requests can be cancelled by the idle timeout\n\nWith a short idle timeout and a handler that takes longer than that timeout, the session can be reaped mid-request and the client waits until timeout / session termination rather than receiving the tool result.\n\n### Reproduction outline\n\n- configure `StreamableHTTPSessionManager(app=..., session_idle_timeout=...)`\n- make a tool handler sleep longer than the timeout\n- call the tool over StreamableHTTP\n\n### Observed behavior\n\nOn current `main`, the active request can be terminated before the handler finishes, and the client fails instead of receiving the result.\n\n## Expected behavior\n\n- `streamable_http_app()` should expose `session_idle_timeout`\n- idle reaping should only happen when the session has no in-flight requests\n- once the last active request finishes, the idle deadline can resume normally\n\n## Validation\n\nI reproduced both behaviors locally against current `main`.\n\nI also verified that a minimal patch can fix both together by:\n\n1. threading `session_idle_timeout` through the low-level + MCPServer `streamable_http_app()` wrappers\n2. suspending idle reaping while at least one request is in flight\n3. restoring the idle deadline after the last active request completes\n\nA focused regression suite in `tests/server/test_streamable_http_manager.py` can cover:\n\n- passthrough from `streamable_http_app(session_idle_timeout=...)`\n- active request longer than the timeout still completes successfully\n- existing idle-session reaping still works once requests are finished\n","author":{"url":"https://github.com/shaun0927","@type":"Person","name":"shaun0927"},"datePublished":"2026-04-16T15:38:12.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/2455/python-sdk/issues/2455"}