feat!: remove SSE transport support #562
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SSE transport has been removed from the MCP specification in favor of streamable HTTP. This removes all SSE-specific transport code: - Remove `transport-sse-client` and `transport-sse-server` features - Remove `SseClientTransport` and `SseServer` types - Remove SSE-specific examples (`counter_sse`, `counter_sse_directly`) - Migrate auth examples from SSE to streamable HTTP - Update tests to remove SSE transport usage - Update documentation BREAKING CHANGE: The following have been removed: - `transport-sse-client` feature - `transport-sse-client-reqwest` feature - `transport-sse-server` feature - `SseClientTransport` type - `SseServer` type - `sse_client` and `sse_server` modules Users should migrate to streamable HTTP transport which provides equivalent functionality. See `StreamableHttpClientTransport` and `StreamableHttpService` for the replacement APIs. Ref: #561 (comment)
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I think removing SSE now is too early for SDK. |
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SSE is super unstable ... There is no reason to promote it . It not a bug, it just the wrong architecture. SSE needs sticky sessions and it very hostile load balancers. HTTP streamable is preferred way to connect remotely. |
This is not promoting it, but rather it existed in spec 2024-11-05 before, and we cannot start deleting it directly. Marking it as obsolete and deleting it in a later version would be more suitable for code evolution. As an SDK, we are not following the upper application layer, but rather adopting a gradual strategy based on specifications, especially for features that need to be abandoned. |
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This is an SDK not a consumer API. You can drop and refactor as much you need to make the SDK cleaner and more secure. It won't force auto update on people repos. This is a Rust context, that means if someone upgrade blindly, the compiler will not warn, it will refuse to obey. There is no (I shipped it, production blew because protocol was removed... javascript/ruby/python style) They have 2 options:
Your thinking is not wrong, but this SDK case is an exception. The SSE spec was rushed and was afterthought, it never worked more than few minutes. The STDIO in 2024 is still used in few abandoned repos, but SSE had no production implementation , zero serious user base. IDEs implemented remote MCP after HTTP streamable got released, and Claude code and other are supporting spec of June 2025+. I will stand corrected if you show me 1 single serious app that still depends on 2024 SSE. The work is already done by @domdomegg. We just have to merge it. |
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I reviewed and approved before seeing this conversation @jokemanfire @seuros @jokemanfire I am interested to hear if you have concerns about simply removing it now @domdomegg You may also be able to provide context on what you've seen other SDKs do, etc |
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I still prefer to mark n+1 as dropped and n+2 as deleted for the evolution of Rust code.But @seuros as mentioned, there's zero serious user base, feel free to do this. |
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Yeah, I agree. Merging. Thanks @domdomegg |
BREAKING CHANGE: Remove SSE transport (/sse, /message endpoints) Changes: - Remove SSE transport - deprecated in MCP spec, removed in rmcp 0.11 - Add error module with thiserror for standardized error handling - Add clippy.toml for fine-grained lint configuration - Add Config builder pattern for fluent API - Enhance test helpers with start_with_auth() and test client utilities - Update documentation to reflect Streamable HTTP only refs: - modelcontextprotocol/rust-sdk#561 - modelcontextprotocol/rust-sdk#562
SSE transport has been removed from the MCP specification in favor of streamable HTTP. This removes all SSE-specific transport code.
Changes
transport-sse-clientandtransport-sse-serverfeaturesSseClientTransportandSseServertypescounter_sse,counter_sse_directly)Breaking changes
The following have been removed:
transport-sse-clientfeaturetransport-sse-client-reqwestfeaturetransport-sse-serverfeatureSseClientTransporttypeSseServertypesse_clientandsse_servermodulesUsers should migrate to streamable HTTP transport. See
StreamableHttpClientTransportandStreamableHttpServicefor the replacement APIs.Ref: #561 (comment)