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Streamable HTTP: client sets Mcp-Name raw and does not Base64-encode a non-header-safe name

Status: Open.

#1243 In modelcontextprotocol/go-sdk;

· arpankernel opened on Sep 5, 2026

mcp: CallToolResult structuredContent loses large integer precision

Status: Open.

#1236 In modelcontextprotocol/go-sdk;

· CaliLuke opened on Sep 4, 2026

A response is still written for a request after notifications/cancelled

P2Moderate issues, valuable feature requestsModerate issues, valuable feature requests

Status: Open.

#1235 In modelcontextprotocol/go-sdk;

· ddromanidis opened on Sep 3, 2026

Streamable HTTP: a Base64-encoded Mcp-Name is rejected as a header mismatch instead of decoded

P1Significant bug affecting many usersSignificant bug affecting many users

Status: Open.

#1234 In modelcontextprotocol/go-sdk;

· ddromanidis opened on Sep 3, 2026

Streamable HTTP: a 2026-07-28 POST carrying Last-Event-ID is refused instead of ignored

Status: Open.

#1233 In modelcontextprotocol/go-sdk;

· ddromanidis opened on Sep 3, 2026

mcp: add StreamableHTTPOptions.StreamKeepAlive — the SSE keep-alive comment the 2026-07-28 spec encourages for subscriptions/listen

Status: Open.

#1229 In modelcontextprotocol/go-sdk;

· yhxlele opened on Sep 2, 2026

mcp: ResourceUpdated notifies subscribers serially, so one stalled stream write starves every other subscriber of the URI

Status: Open.

#1227 In modelcontextprotocol/go-sdk;

· yhxlele opened on Sep 2, 2026

mcp: tools/call omits required resultType when a receiving middleware short-circuits

P3Nice to haves, rare edge casesNice to haves, rare edge cases

Status: Open.

Bug

#1225 In modelcontextprotocol/go-sdk;

· roncodingenthusiast opened on Sep 1, 2026

mcp: a malformed JSON frame terminates the stdio session

Status: Open.

#1209 In modelcontextprotocol/go-sdk;

· blackwell-systems opened on Aug 29, 2026

Session-lifecycle bookkeeping logs at info, spamming multiple log lines per request on stateless streamable HTTP

P3Nice to haves, rare edge casesNice to haves, rare edge cases

Status: Open.

Bug

#1204 In modelcontextprotocol/go-sdk;

· tjhop opened on Aug 28, 2026

mcp: typed tool arguments lose precision for large int64 values

Status: Open.

#1201 In modelcontextprotocol/go-sdk;

· huskar-t opened on Aug 27, 2026

sse: Close does not drain incoming; Read can deliver stale messages after Close and POST can return false 202

P3Nice to haves, rare edge casesNice to haves, rare edge cases

Status: Open.

#1191 In modelcontextprotocol/go-sdk;

· junnhwan opened on Aug 23, 2026