Fix Streamable HTTP WebClient transport to accept SSE frames without event field - #5783
Closed
ZhangDT-sky wants to merge 2 commits into
Closed
Fix Streamable HTTP WebClient transport to accept SSE frames without event field#5783ZhangDT-sky wants to merge 2 commits into
event field#5783ZhangDT-sky wants to merge 2 commits into
Conversation
Signed-off-by: ZhangDT-sky <485918776@qq.com>
Signed-off-by: ZhangDT-sky <485918776@qq.com>
Kehrlann
added
mcp
bug
Contributor
|
For reference, here's the Java SDK equivalent modelcontextprotocol/java-sdk#913 |
Kehrlann
reviewed
Aug 4, 2026
Kehrlann
left a comment
Kehrlann
left a comment
Contributor
There was a problem hiding this comment.
Thank you for your contribution.
I have one open question before we merge this.
Comment on lines
+507
to
+510
| if (data == null || data.isEmpty()) { | ||
| logger.debug("Ignoring SSE message event with empty data: {}", event); | ||
| return Tuples.of(Optional.empty(), List.of()); | ||
| } |
Contributor
There was a problem hiding this comment.
This is untested; what's the use-case?
|
|
||
| private static boolean isMessageEvent(@Nullable String eventType) { | ||
| // Per SSE semantics, missing/blank event type defaults to "message". | ||
| return eventType == null || eventType.isEmpty() || MESSAGE_EVENT_TYPE.equals(eventType); |
Contributor
There was a problem hiding this comment.
Suggested change
| return eventType == null || eventType.isEmpty() || MESSAGE_EVENT_TYPE.equals(eventType); | |
| return !StringUtils.hasLength(eventType) || MESSAGE_EVENT_TYPE.equals(eventType); |
Contributor
|
Merged as part of db7544a. Thank you for your contribution! |
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
3 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.
Summary
This PR fixes SSE parsing in
WebClientStreamableHttpTransportfor Streamable HTTP.Per SSE semantics, when
event:is omitted, the event type defaults tomessage.Previously, the transport only accepted frames where
event == "message"explicitly, so validdata:-only frames could be dropped.This could cause JSON-RPC responses (including
initialize) to be ignored and lead to startup/timeout failures.Root Cause
WebClientStreamableHttpTransport.parse(...)only parsed SSE frames when:event.event().equals("message")If
event.event()wasnull(or empty), the frame was ignored.Changes
WebClientStreamableHttpTransportto treat all of the following as message events:event == nullevent == ""event == "message"WebClientStreamableHttpTransportSseParsingIT#shouldParseSseEventWithoutEventFieldAsMessageThe test serves
text/event-streamwith onlydata:(noevent:) and verifies the JSON-RPC response is parsed and delivered.Why This Is Safe
event: messagebehavior is unchanged.Verification
data:-only SSE frames.Fixes #5780