Trait AgentCore 

pub trait AgentCore: Send + Sync {
    // Required methods
    fn create_session(
        &self,
        id: SessionId,
        cwd: PathBuf,
        mcp_servers: Vec<McpServer>,
        fs: Arc<dyn FsBackend>,
        shell: Arc<dyn ShellBackend>,
        frontend: Frontend,
    ) -> BoxFuture<'_, Result<Arc<dyn Session>, AgentError>>;
    fn load_session(
        &self,
        id: SessionId,
        fs: Arc<dyn FsBackend>,
        shell: Arc<dyn ShellBackend>,
        frontend: Frontend,
    ) -> BoxFuture<'_, Result<Arc<dyn Session>, AgentError>>;
    fn session(&self, id: &SessionId) -> Option<Arc<dyn Session>>;
}

Process-level agent root object.

defect-cli constructs a concrete implementation at startup (holding the LLM provider registry, built-in tool set, and configuration) and injects an Arc<dyn AgentCore> into defect-acp::serve.

Rationale for extracting a trait:

• Allows injecting a mock in tests without spinning up a real LLM.
• If an “embedded agent” (library mode called by a host application) emerges in the future, a second concrete implementation can be added without touching the ACP bridge code.

Required Methods

fn create_session( &self, id: SessionId, cwd: PathBuf, mcp_servers: Vec<McpServer>, fs: Arc<dyn FsBackend>, shell: Arc<dyn ShellBackend>, frontend: Frontend, ) -> BoxFuture<'_, Result<Arc<dyn Session>, AgentError>>

Creates a new session.

id is generated and passed in by the caller (the defect-acp session/new handler) — the filesystem backend already needs a SessionId when constructed outside of AgentCore::create_session (see the ACP filesystem delegation contract). Concrete implementations treat it as the authoritative external id and return AgentError::DuplicateSessionId on duplicates.

mcp_servers is the per-session MCP server list from the session/new request; the concrete implementation spawns subprocesses or establishes SSE connections during initialization, wrapping each MCP tool as a Tool and adding it to the session’s tool table.

fs is the session-level filesystem backend — defect-acp selects LocalFsBackend or AcpFsBackend at assembly time based on the client’s FileSystemCapabilities. The session holds an Arc to it, and all filesystem tool calls go through it.

shell is the session-level shell backend — defect-acp selects LocalShellBackend or AcpShellBackend at assembly time based on the client’s ClientCapabilities::terminal. The session holds an Arc to it, and all bash tool calls go through it.

frontend indicates how the agent is being accessed (Frontend::Acp carries the fs/shell delegation state negotiated during the ACP handshake) and is used to inject the # Environment section of the system prompt.

Errors

MCP startup failure, missing cwd, duplicate id, etc.

fn load_session( &self, id: SessionId, fs: Arc<dyn FsBackend>, shell: Arc<dyn ShellBackend>, frontend: Frontend, ) -> BoxFuture<'_, Result<Arc<dyn Session>, AgentError>>

Restore an existing session from persistent state.

frontend works the same as in AgentCore::create_session — the restored session also uses it to inject runtime environment information.

Errors

The session does not exist, the persisted data is corrupted, the restored cwd is unavailable, etc.

fn session(&self, id: &SessionId) -> Option<Arc<dyn Session>>

Look up an existing session by id.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl AgentCore for DefaultAgentCore