fix(mcp): call onclose when standalone SSE stream aborts on client disconnect#1804
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ctonneslan wants to merge 2 commits intohonojs:mainfrom
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fix(mcp): call onclose when standalone SSE stream aborts on client disconnect#1804ctonneslan wants to merge 2 commits intohonojs:mainfrom
ctonneslan wants to merge 2 commits intohonojs:mainfrom
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When a client disconnects from the GET SSE stream (network drop, process exit, etc.), the stream abort handler only cleans up internal state but never notifies the application via onclose. Since MCP clients typically do not send DELETE requests when they disconnect, the SSE stream dropping is the only signal that the client is gone. Now calls onclose when the standalone GET SSE stream (identified by the _GET_stream ID) aborts, matching the semantic intent of onclose. Fixes honojs#1762
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@ctonneslan Thank you for the PR. Hey @MathurAditya724 , can you handle this? |
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## main #1804 +/- ##
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Coverage 91.73% 91.73%
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Lines 3785 3787 +2
Branches 957 958 +1
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+ Hits 3472 3474 +2
Misses 281 281
Partials 32 32
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Summary
Calls
onclosewhen the standalone GET SSE stream aborts (client disconnect), so applications can detect when an MCP client is gone.Problem
When a client opens a GET SSE stream and then disconnects (process exit, network drop), the transport's
stream.onAborthandler fires and cleans up#streamMapping, but the disconnection is never propagated to theonclosecallback.oncloseis only called insideclose(), which is triggered by an explicit DELETE request. In practice, MCP clients (Cursor, Claude Code, etc.) do not send DELETE when they disconnect. The SSE stream dropping is the only signal available.This means applications have no way to know when a client has gone away.
Fix
When the standalone GET SSE stream (identified by
_GET_streamID) aborts, callthis.onclose?.()to notify the application. This only fires for the standalone stream, not for per-request POST SSE streams.Changes
packages/mcp/src/streamable-http.ts: Addedonclosecall in the standalone SSE stream'sonAborthandlerFixes #1762