fix: Handle SSE controller closed state in error logging#795
Merged
jirispilka merged 2 commits intomasterfrom May 6, 2026
Merged
fix: Handle SSE controller closed state in error logging#795jirispilka merged 2 commits intomasterfrom
jirispilka merged 2 commits intomasterfrom
Conversation
WebStandardStreamableHTTPServerTransport.writeSSEEvent throws
ERR_INVALID_STATE ("Invalid state: Controller is already closed") when
the SSE ReadableStream controller was closed by client cancellation
before a queued event was flushed. The SDK forwards it to onerror.
This is client-disconnect noise, not a server fault, so route it
through the same softFail branch as the other known disconnect
patterns to avoid Mezmo error alerts (#793).
https://claude.ai/code/session_01LpjxNt1eBv8qBZcKLozmj1
jirispilka
changed the title
MQ37
approved these changes
May 5, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Added "Controller is already closed" to the soft-fail error pattern
This error has been raised in MCP SKD recently
"{"code":"ERR_INVALID_STATE","message":"Invalid state: Controller is already closed","name":"TypeError","stack":"TypeError [ERR_INVALID_STATE]: Invalid state: Controller is already closed\n at ReadableStreamDefaultController.enqueue (node:internal/webstreams/readablestream:1102:13)\n at WebStandardStreamableHTTPServerTransport.writeSSEEvent (f...[truncated]"},"msg":"[MCP Error]"}"
closes #793