What
An MCP server declared with type "sdk" in a configuration file is now explicitly rejected with a dedicated error, unless the configuration comes from the in-process SDK (marked as source dynamic). The general "unknown server type" error message also no longer lists sdk as a valid type unless the source is dynamic.
Why
This closes off a way of declaring an sdk-type server that only an SDK host application should be able to register, giving a clearer error instead of letting it fail as a generic unknown type.
Names in the bundlesdk
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on Log at info level touched a line naming sdk after this was published.
For long-running agentic tasks, the TypeScript and Ruby tool runners support automatic [compaction](https://platform.claude.com/docs/en/build-with-claude/context-editing#client-side-compaction-sdk), which generates summaries when token usa…agents-and-tools/tool-use/tool-runner see the edit
Confirmed since
Anthropic's documentation has since written up sdk, on Error reference.
You tried to switch [output styles](/docs/en/output-styles) with `/output-style <style>` or `/config outputStyle=<style>` in a session whose setting sources exclude `local`. Examples are an [Agent SDK](/docs/en/agent-sdk/typescript) sessio…errors see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up sdk, on Error reference.