SDK MCP server manifests now report per-server outcomes and have rules for remote sessions

What

The Agent SDK lets a program drive Claude Code from code. MCP servers are add-ons that give Claude extra tools, and some run inside the host program itself. The SDK could already pass a "manifest" for each such server: the server's answers to its start-up call (initialize) and its tool-list call (tools/list), so Claude Code does not have to ask for them live. This release changes how those manifests are accepted and reported, especially in remote sessions, which run on Anthropic's cloud rather than on your own computer.

• sdkMcpServerManifestsOrigin is a new optional field in the SDK's initialize request. Its value host_per_send marks that the host put the manifests together for this particular send. Remote session transports ignore a manifest without this mark, and Claude Code refuses marked manifests older than five minutes.
• sdk_mcp_manifests_parked is a new field in the initialize response. For each SDK MCP server it reports one outcome: parked, already_connected, protocol_version_mismatch, malformed or not_honoured. A parked manifest answers the server's initialize and first tools/list without a live round trip.
• On remote-session workers, manifests are not honoured and the servers go through the normal handshake over the control channel. Before, manifests were honoured everywhere except on an older kind of worker, and no per-server outcome was reported.
• The sdk_mcp_manifests refresh channel is offered only when the server-controlled switch tengu_sdk_mcp_manifests allows it (built-in fallback: on). For remote transports it also needs a session limited to the owner's account (owner_account_only) and the switch tengu_ccr_sdk_mcp_remote_manifests (built-in fallback: off). Otherwise only sdk_mcp_tools_list_changed is used. A separate helper gives the reasons flag_off and flag_unsettled. Before, tengu_sdk_mcp_manifests was checked once per session.
• A list that held only mcp_read_resource_v1 now also holds sdk_mcp_tools_list_changed and sdk_mcp_manifests. The same change adds the name model_saved_successor_notice to a list and passes a new gateCause detail in one internal report.

Why

A host that uses manifests to speed up MCP server start-up can now see, for each server, whether the shortcut was used and why not. In remote sessions the shortcut depends on the origin marker, the manifest's age and the remote switch. No reading has been taken of tengu_ccr_sdk_mcp_remote_manifests, so whether remote sessions use manifests in practice is not known.