Struct DefaultHandler 

pub struct DefaultHandler {
    pub sink: Box<dyn IoSink>,
    pub read_root: Option<PathBuf>,
    pub budget_remaining: Arc<AtomicU64>,
    pub budget_ceiling: Option<u64>,
    pub program: Option<Arc<Program>>,
    pub chat_registry: Option<Arc<ChatRegistry>>,
    pub mcp_clients: McpClientCache,
    /* private fields */
}

Fields

sink: Box<dyn IoSink>

read_root: Option<PathBuf>

Optional read root for io.read — when set, io.read("p") resolves to read_root.join(p). Lets tests run without touching the real fs.

budget_remaining: Arc<AtomicU64>

Per-run budget pool (#225). Arc<AtomicU64> so parallel branches share one counter without locking. Initialized to the policy ceiling at handler construction; each call to a function with declared [budget(N)] deducts N atomically via note_call_budget. Cloning the handler is intentional for net.serve / chat handlers — they share the same pool.

budget_ceiling: Option<u64>

The original ceiling that budget_remaining started at, kept for diagnostics so a BudgetExceeded error can report (used, ceiling) rather than just “exceeded by N”.

program: Option<Arc<Program>>

Shared reference to the program, needed by net.serve so the handler can spin up fresh VMs to dispatch incoming requests. None if the handler was constructed without a program.

chat_registry: Option<Arc<ChatRegistry>>

Chat registry; populated by net.serve_ws’s per-message dispatch so chat.broadcast / chat.send work from inside a handler invocation.

mcp_clients: McpClientCache

LRU cache of agent.call_mcp clients keyed by the command-line string (#197). Avoids spawn-per-call cost when an agent invokes the same MCP server in tight loops. Capped — when the cache is full, the least-recently-used entry is dropped (its subprocess is reaped on Drop).

Implementations

impl DefaultHandler

pub fn new(policy: Policy) -> Self

pub fn with_program(self, program: Arc<Program>) -> Self

pub fn with_chat_registry(self, registry: Arc<ChatRegistry>) -> Self

pub fn with_sink(self, sink: Box<dyn IoSink>) -> Self

pub fn with_read_root(self, root: PathBuf) -> Self

Trait Implementations

impl EffectHandler for DefaultHandler

fn note_call_budget(&mut self, cost: u64) -> Result<(), String>

Per-call budget enforcement (#225). VM calls this before invoking any function whose signature declares [budget(N)]. The cost N is deducted atomically from the shared pool; returning Err aborts the call before any frame is pushed.

fn dispatch( &mut self, kind: &str, op: &str, args: Vec<Value>, ) -> Result<Value, String>