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[Server][Client] Remove JSON-RPC batch support - #680
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MCP removed batching in 2025-06-18. A JSON array is refused with -32600 for every protocol version, and MessageFactory::create() returns one message and throws on invalid input.
chr-hertel
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CodeWithKyrian,
Nyholm and
soyuka
as code owners
November 8, 2026 12:17
chr-hertel
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🟡 Changes recommended
An empty JSON array bypasses rejection, allowing a POST with a valid handshake session to return HTTP 200 or SSE instead of the documented HTTP 400.
1 open issue
What changed in this PR
Removes JSON-RPC batch support from the PHP SDK’s server and client, including for negotiated 2025-03-26 connections.
Changes:
- Changes
MessageFactory::create()to return one message and throw on invalid input. - Simplifies dispatch, HTTP responses, notification buses, and scope handling for single messages.
- Updates tests and documentation, and records the breaking changes.
| File | Description |
|---|---|
| tests/Unit/Server/Wire/InboundClassifierTest.php | Updates batch classification expectations. |
| tests/Unit/Server/Transport/StreamableHttpTransportTest.php | Tests batch rejection and single-response ordering. |
| tests/Unit/Server/Transport/StdioDualEraTest.php | Tests rejection without settling the protocol era. |
| tests/Unit/Server/Transport/Http/OAuth/ScopePolicyTest.php | Tests default scopes for non-message inputs. |
| tests/Unit/Server/Transport/Http/Middleware/AuthorizationMiddlewareTest.php | Removes batch scope-union coverage. |
| tests/Unit/Server/Transport/AccessTokenFlowTest.php | Verifies rejected batches cannot execute tools. |
| tests/Unit/Server/Subscription/NotificationBusTest.php | Tests skipping unreadable cached entries. |
| tests/Unit/Server/ProtocolTest.php | Replaces batch processing tests with rejection coverage. |
| tests/Unit/Server/ProtocolSessionLockTest.php | Removes batch-specific lock tests. |
| tests/Unit/Server/BuilderTest.php | Adapts extension assertions to single messages. |
| tests/Unit/JsonRpc/MessageFactoryTest.php | Tests single-message returns and thrown exceptions. |
| tests/Unit/JsonRpc/MalformedInputTest.php | Expects exceptions for malformed input. |
| tests/Unit/Client/Transport/StdioTransportTest.php | Retains notification ordering coverage without batches. |
| tests/Unit/Client/Transport/HttpTransportTest.php | Replaces batch fixtures in stream coverage. |
| tests/Unit/Client/ProtocolTest.php | Tests dropping server batches with a warning. |
| src/Server/Wire/InboundClassifier.php | Rejects batches across protocol eras. |
| src/Server/Transport/TransportInterface.php | Updates single-response documentation. |
| src/Server/Transport/StreamableHttpTransport.php | Stores and returns one JSON-RPC response. |
| src/Server/Transport/StdioTransport.php | Adapts routing and cancellation parsing. |
| src/Server/Transport/Http/OAuth/ScopePolicy.php | Computes scopes for one decoded message. |
| src/Server/Subscription/Psr6NotificationBus.php | Parses one notification per cached entry. |
| src/Server/Subscription/Psr16NotificationBus.php | Parses one notification per cached entry. |
| src/Server/Stateless/StatelessProtocol.php | Handles factory validation exceptions. |
| src/Server/Protocol.php | Simplifies dispatch and session resolution. |
| src/JsonRpc/MessageFactory.php | Removes batch parsing and size configuration. |
| src/Client/Transport/HttpTransport.php | Matches individual stream responses only. |
| src/Client/Protocol.php | Dispatches one message and logs invalid input. |
| docs/run/protocol-eras.md | Documents batch rejection across eras. |
| docs/run/http.md | Replaces batch-limit guidance with rejection behavior. |
| CHANGELOG.md | Records server, client, and factory breaking changes. |
Review effort: Balanced
It decoded like {} and got past the classifier, which answered it with HTTP 200 in a session.
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MCP removed batching in
2025-06-18, so a JSON array is refused with-32600for every protocol version - that includes2025-03-26, which requires batches and which we still negotiate. I didn't find a well-adopted client that sends them, but can't see into the closed-source ones.[BC Break]
MessageFactory::create()returns one message and throws on invalid input,$maxBatchSizeis gone - seeCHANGELOG.md.