Claude Code makes the v2 MCP client and 2026-07-28 negotiation the default on Bedrock, Vertex and Foundry

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v2.1.274 switches Bedrock, Vertex, Foundry and telemetry-disabled installs to the v2 MCP client with MCP 2026-07-28 protocol negotiation against direct HTTP servers, matching what other installs already did; opt out with `MCP_SDK_GENERATION=v1` or `MCP_PROTOCOL_NEGOTIATION=legacy`. The same release fixes Streamable HTTP MCP tool calls timing out at about five minutes even when a longer per-server `timeout` was configured, `http` servers that only speak legacy HTTP+SSE failing when they answer the first request with a 422, prompts and resources not refreshing when a server sends list-changed notifications without declaring `listChanged`, and 403 `insufficient_scope` refusals being reported as an expired sign-in rather than naming the missing permissions.