[Server] Reject JSON-RPC batch requests - #424
Open
ez-lbz wants to merge 1 commit into
Open
Conversation
MCP no longer supports JSON-RPC batches: a POST body must be a single JSON-RPC message. MessageFactory currently accepts top-level arrays and hydrates each entry, so a batch is handled as a set of messages instead of being refused outright. Reject any top-level array as invalid input before any entry is hydrated, and drop the now-dead maxBatchSize cap and its constructor parameter. Update the affected unit tests and the transports docs to match.
ez-lbz
requested review from
CodeWithKyrian,
Nyholm,
chr-hertel and
soyuka
as code owners
August 16, 2026 15:03
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
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
MCP no longer supports JSON-RPC batches: a POST body must be a single JSON-RPC message.
MessageFactorycurrently accepts top-level arrays and hydrates each entry, so a batch is processed as a set of messages instead of being refused outright.This change rejects any top-level array as invalid input before any entry is hydrated, returning a single
InvalidInputMessageException(the existing per-message error contract) instead of processing the batch. The now-deadmaxBatchSizecap, its constructor parameter, andDEFAULT_MAX_BATCH_SIZEare removed.Tests:
MessageFactoryTest: batch payloads (valid, mixed, and error-containing) are asserted to be rejected wholesale; obsoletemaxBatchSizetests removed.MalformedInputTest: a batch payload is asserted to be rejected without hydrating any entry.Server\ProtocolTest: batch input is asserted to produce a single Invalid Request error and to never hydrate batch entries.