Concepts

Core concepts

• The directory owns access. Its create and load methods return a Session binding only after the host authorizes it. It can validate the working directory, additional directories, and MCP servers before opening the Session.
• Shiitake owns Session state. The ACP adapter projects messages, tool calls, progress, cancellation, and terminal results. It does not own the transcript or delete the durable Session.
• An ACP connection owns its lease. Closing a Session or connection releases its host-provided client lease and observation. An active prompt is cancelled and allowed to settle for up to five seconds by default when its Session closes.
• The server is an adapter. createShiitakeAcpServer exposes the same agent through the maintained Streamable HTTP transport; it does not supply authorization by itself.

Editor capabilities

The adapter uses ACP SDK 1.7 and stable protocol v1. Initialization returns the supported protocol version even when an editor offers another version; the editor decides whether it can continue. Session listing is advertised only when the authorized host directory supplies it. Local lists saved project Sessions.

A host may supply a terminal login method. It is advertised only when the editor supports terminal authentication; the editor runs the login command in a separate interactive process. Hosted directories do not acquire Local credentials.

Text resources retain their URI and contents in prompt context. Resource links retain their name and URI for the Agent’s authorized tools to resolve. Images, including embedded image resources, enter Shiitake’s bounded prompt admission and persist as Pi image content. History replays images through ACP. Audio and other binary resources return invalid_params; they are not silently discarded.

Protocol references: initialization and content.