reload_plugins can now add plugins mid-session

What

A plugin is an add-on package for Claude Code. Programs that drive Claude Code through the SDK (its developer kit) send a reload_plugins request to reload plugins. That request now takes an optional add_plugins list:

• Each entry is { type: "local", path } with an absolute path, the same shape as the SDK plugins option. It joins the session as one more --plugin-dir would, and plugins already loaded stay loaded.
• The plugins are installed before the reload, optionally without looking for their MCP servers.
• If the reload is held because it would affect the cache, or it fails, the added plugins are undone.
• Refusals come back with an error message. The request is refused for callers on another machine, when managed settings set disableSideloadFlags, for Remote Control and cloud workers, in cloud-hosted sessions (which used to let it through), and with sandbox_deny_failed when a running sandbox, the protective boundary around commands Claude runs, cannot keep shell commands out of the new folders.

Also changed:

• mcp_call accepts result_not_for_model, passed on as resultNotForModel. It is ignored on connections that do not redact.
• A settings pins result now includes settingsFiles, and a change summary tracks changes to agentProxy.

Why

A host program can add plugins to a running session without restarting it. Organizations that block sideloaded plugins with disableSideloadFlags also block this route.