Struct ToolCapabilities 

pub struct ToolCapabilities {
    pub watcher_exit_path: Option<PathBuf>,
    pub tool_register_tx: Option<UnboundedSender<Vec<Arc<dyn Tool>>>>,
    pub session_manager: Option<Arc<SessionManager>>,
    pub subagent_registry: Option<Arc<Mutex<SubagentRegistry>>>,
    pub event_queue: Option<Arc<EventQueue>>,
    pub delegation_parent: Option<String>,
    pub secret_prompt: Option<SecretPromptHandle>,
    pub orchestration: Option<Arc<OrchestrationRuntime>>,
    pub tool_activation: Option<ActivationCapability>,
    pub mcp_leases: Option<McpLeaseCapability>,
    pub extension_leases: Option<ExtensionLeaseCapability>,
    pub memory_context: Option<MemoryContextCapability>,
}

Runtime capability handles — shared services a tool may require.

Fields

watcher_exit_path: Option<PathBuf>

tool_register_tx: Option<UnboundedSender<Vec<Arc<dyn Tool>>>>

session_manager: Option<Arc<SessionManager>>

subagent_registry: Option<Arc<Mutex<SubagentRegistry>>>

event_queue: Option<Arc<EventQueue>>

delegation_parent: Option<String>

Current worker handle when this context belongs to a delegated runtime. None denotes the foreground root.

secret_prompt: Option<SecretPromptHandle>

orchestration: Option<Arc<OrchestrationRuntime>>

Runtime-enforced delegation/lifecycle policy. When present, every spawn path must authorize before creating channels, threads, or provider runtimes.

tool_activation: Option<ActivationCapability>

Discovery/activation capability context (Task 17): passive catalog snapshot + retained session-set handle + host-supplied activation authority. None (default for manual fixtures and non-stream contexts) means the discovery/activation builtins fail typed and no model-initiated activation is possible.

mcp_leases: Option<McpLeaseCapability>

Session-scoped exact MCP lease capability (Task 19): exact session identity + shared runtime manager. None (default for non-stream contexts) means deferred MCP tools fail typed and start nothing.

extension_leases: Option<ExtensionLeaseCapability>

Session-scoped exact EXTENSION lease capability (Task 20): exact session identity + shared extension runtime manager. None (default for non-stream contexts) means deferred extension tools fail typed and start nothing.

memory_context: Option<MemoryContextCapability>

Session-scoped continuous-memory context capability (task A4, spec §7.2): shared per-session memory state + host-owned grant scope. None (default for non-stream contexts) means the memory_context builtin can commit nothing — lease-granting actions fail typed, while status/disable still answer deterministically Off (memory off requires no infrastructure).