modelcontextprotocol/rust-sdk rmcp-v3.0.0-beta.1 on GitHub

route SEP-2260 associated server requests to the originating SSE stream (#1029)
[breaking] add distributed SSE event store (#1024)
add client-side TTL-honoring response cache (SEP-2549) (#1025)
[breaking] Implement SEP-2663 Tasks Extension (#1020)
add subscription listen streams (SEP-2575) (#1000)
(auth) bind DCR client credentials to issuing authorization server (SEP-2352) (#998)
add modern client lifecycle modes (SEP-2575) (#995)
(auth) accumulate client-side scopes during step-up authorization (#888)
[breaking] add server discovery and negotiation (SEP-2575) (#973)
(conformance) add SEP-2243 header validation tool (#997)
[breaking] align metadata models with draft schema (#993)
[breaking] implement SEP-2549 cache hints (#889)
[breaking] add MRTR behavior support (SEP-2322) (#929)
[breaking] type Annotations.lastModified as a string (#956)
[breaking] add SEP-2243 HTTP standard headers (#907)
relax outputSchema to accept non-object JSON Schema types (SEP-2106) (#895)
[breaking] relax tool result structuredContent type (SEP-2106) (#933)
[breaking] add MRTR model types (SEP-2322) (#915)

reap completed response send tasks (#1026)
accept stringified numeric response IDs (#1021)
re-register after auth server change (#1011)
.with_stateful_mode -> .with_legacy_session_mode (#1015)
preserve negotiated progress responses (#1005)
(server) serve draft-version requests statelessly per SEP-2567 (#999)
pass client header conformance (#1012)
(auth) add an SDK path for pre-registered OAuth clients (#994)
(transport) cancel in-flight request on stateless streamable-HTTP client disconnect (#857) (#967)
(auth) distinguish rejected refresh tokens from transient failures (#963)
(auth) validate discovered metadata issuer (#996)
bound streamable HTTP memory usage (#970)
(streamable-http) preserve progress in JSON mode (#990)
specify compatible sse-stream version (#968)
flag schema derive on schemars feature (#966)

BREAKING: rename StreamableHttpServerConfig::stateful_mode to legacy_session_mode (and the builder with_stateful_mode to with_legacy_session_mode) to clarify that the option only affects legacy protocol versions (< 2026-07-28); per SEP-2567 the 2026-07-28 draft version is always served statelessly (#999)