Goose 1.50.1 rolls back the "prefer latest MCP version" change that 1.50.0 shipped six days earlier, after it broke stdio and streamable_http extension startup

Goose, whose repository now lives in the aaif-goose GitHub organization, released v1.49.0 on 2026-09-03 with a cluster of MCP-relevant changes: MCP sampling for reasoning-first responses (#11092), pre-registered OAuth clients for streamable_http extensions (#11182), MCP conformance tests added to the project's CI (#10940), Unicode tag sanitization in MCP prompts (#11453), and a fix that preserves existing extensions when a new MCP server is added (#11339).

v1.50.0 followed on 2026-09-08 with "Prefer latest MCP version" (PR #11827), described in the pull request as a change that "updates goose to prefer the 2026-07-28 protocol version." The change moved Goose's default client lifecycle from always issuing the legacy initialize handshake to first probing server/discover for the newer revision and falling back to the legacy path only under specific conditions.

Two regressions surfaced against that default. Issue #12040 reported that stdio extensions whose servers support protocol versions no newer than 2025-11-25 failed to start, because the new Auto lifecycle mode "only falls back to the legacy initialize handshake on a 10s discover timeout or a legacy JSON-RPC error, not on an empty version intersection with a discover-capable server," so a spec-compliant older server was rejected outright instead of being negotiated down. Issue #11965 reported a second failure: streamable_http extensions against servers that keep their notification channel open but send nothing on it, valid behavior per the transport spec, failed with "unexpected server response: empty sse stream" and were torn down even though their initialize exchange had already succeeded.

v1.50.1, released 2026-09-14, reverted the change under the release-note heading "Roll back MCP default version selection update," linking commit 6d8152a99adbd149783d9d0cc2b43ce2755cca95, the commit that had introduced the preference. The rollback itself shipped as pull request #12064, "fix(revert): roll back 6d8152a99adbd149783d9d0cc2b43ce2755cca95," which closes both #12040 and #11965.