Struct HostBridge 

pub struct HostBridge { /* private fields */ }

A JSON-RPC 2.0 bridge to a host process over stdin/stdout.

The bridge sends requests to the host on stdout and receives responses on stdin. A background task reads stdin and dispatches responses to waiting callers by request ID. All stdout writes are serialized through a mutex to prevent interleaving.

Implementations

impl HostBridge

pub fn new() -> Self

Create a new bridge and spawn the stdin reader task.

Must be called within a tokio LocalSet (uses spawn_local for the stdin reader since it’s single-threaded).

pub fn from_parts( pending: Arc<Mutex<HashMap<u64, Sender<Value>>>>, cancelled: Arc<AtomicBool>, stdout_lock: Arc<Mutex<()>>, start_id: u64, ) -> Self

Create a bridge from pre-existing shared state.

Unlike new(), does not spawn a stdin reader — the caller is responsible for dispatching responses into pending. This is used by ACP mode which already has its own stdin reader.

pub fn from_parts_with_writer( pending: Arc<Mutex<HashMap<u64, Sender<Value>>>>, cancelled: Arc<AtomicBool>, writer: HostBridgeWriter, start_id: u64, ) -> Self

pub async fn from_harn_module( vm: Vm, module_path: &Path, ) -> Result<Self, VmError>

Create an in-process host bridge backed by exported functions from a Harn module. Used by harn playground to avoid JSON-RPC boilerplate.

pub fn set_session_id(&self, id: &str)

Set the ACP session ID for session-scoped notifications.

pub fn set_script_name(&self, name: &str)

Set the currently executing script name (without .harn suffix).

pub async fn call(&self, method: &str, params: Value) -> Result<Value, VmError>

Send a JSON-RPC request to the host and wait for the response. Times out after 5 minutes to prevent deadlocks.

pub fn notify(&self, method: &str, params: Value)

Send a JSON-RPC notification to the host (no response expected). Serialized through the stdout mutex to prevent interleaving.

pub fn is_cancelled(&self) -> bool

Check if the host has sent a cancel notification.

pub fn take_resume_signal(&self) -> bool

pub fn signal_resume(&self)

pub fn set_daemon_idle(&self, idle: bool)

pub fn is_daemon_idle(&self) -> bool

pub fn take_skills_reload_signal(&self) -> bool

Consume any pending skills/update signal the host has sent. Returns true exactly once per notification, letting callers trigger a layered-discovery rebuild without polling false positives. See issue #73 for the hot-reload contract.

pub fn signal_skills_reload(&self)

Manually mark the skill catalog as stale. Used by tests and by the CLI when an internal event (e.g. harn install) should trigger the same rebuild a skills/update notification would.

pub async fn list_host_skills(&self) -> Result<Vec<Value>, VmError>

Call the host’s skills/list RPC and return the raw JSON array it responded with. Shape: [{ "id": "...", "name": "...", "description": "...", "source": "..." }, ...]. The CLI adapter converts each entry into a crate::skills::SkillManifestRef.

pub async fn list_host_tools(&self) -> Result<Vec<Value>, VmError>

Call the host’s host/tools/list RPC and return normalized tool descriptors. Shape: [{ "name": "...", "description": "...", "schema": {...}, "deprecated": false }, ...]. The bridge also accepts { "tools": [...] } and { "result": { "tools": [...] } } wrappers for lenient hosts.

pub async fn fetch_host_skill(&self, id: &str) -> Result<Value, VmError>

Call the host’s skills/fetch RPC for one skill id. Returns the raw JSON body so the CLI can inspect both the frontmatter fields and the skill markdown body in whatever shape the host sends.

pub async fn push_queued_user_message(&self, content: String, mode: &str)

pub async fn take_queued_user_messages( &self, include_interrupt_immediate: bool, include_finish_step: bool, include_wait_for_completion: bool, ) -> Vec<QueuedUserMessage>

pub async fn take_queued_user_messages_for( &self, checkpoint: DeliveryCheckpoint, ) -> Vec<QueuedUserMessage>

pub fn send_output(&self, text: &str)

Send an output notification (for log/print in bridge mode).

pub fn send_progress( &self, phase: &str, message: &str, progress: Option<i64>, total: Option<i64>, data: Option<Value>, )

Send a progress notification with optional numeric progress and structured data.

pub fn send_log(&self, level: &str, message: &str, fields: Option<Value>)

Send a structured log notification.

pub fn send_call_start( &self, call_id: &str, call_type: &str, name: &str, metadata: Value, )

Send a session/update with call_start — signals the beginning of an LLM call, tool call, or builtin call for observability.

pub fn send_call_progress( &self, call_id: &str, delta: &str, accumulated_tokens: u64, user_visible: bool, )

Send a session/update with call_progress — a streaming token delta from an in-flight LLM call.

pub fn send_call_end( &self, call_id: &str, call_type: &str, name: &str, duration_ms: u64, status: &str, metadata: Value, )

Send a session/update with call_end — signals completion of a call.

pub fn send_worker_update( &self, worker_id: &str, worker_name: &str, status: &str, metadata: Value, audit: Option<&MutationSessionRecord>, )

Send a worker lifecycle update for delegated/background execution.