Shared cancel action — a fuz_app protocol action validating the spec+handler tuple pattern on a notification-kind action.
Semantics: the client sends `{jsonrpc, method: 'cancel', params:
{request_id}}` to abort an in-flight request on the same socket.
register_action_ws intercepts this notification and aborts the
matching pending request's ctx.signal. Unknown ids are no-ops by design —
races between response arrival and cancel delivery are safe without extra
coordination.
The handler field is an empty stub: cancel semantics are dispatcher-owned
(the dispatcher has the {request_id → AbortController} map, not the
handler). The handler exists for symmetry with other protocol actions
like heartbeat_action; the dispatcher never calls it. Consumers
spread cancel_action (or the protocol_actions bundle from
actions/protocol.ts) into their server's actions array so spec_by_method
knows about it (enabling input validation on incoming cancels) and so
create_rpc_client codegen produces app.api.cancel() when desired —
though FrontendWebsocketClient.request({signal}) sends the cancel on
abort without needing the typed API.
Wire format is snake_case cancel with {request_id}, not MCP's
$/cancelRequest with {requestId} — fuz_app's WS transport isn't MCP,
and adopting MCP's convention would leak protocol-specific framing into
the base transport. When MCP elicitation (Phase 5) lands, a translation
layer at the MCP adapter is the right seam.
4 declarations
Action<BaseHandlerContext> Protocol-action tuple — spread into the server's actions array (or via
protocol_actions from actions/protocol.ts) so the dispatcher registers the
spec for input validation and so create_rpc_client codegen sees the
method. The client doesn't need to call it directly;
FrontendWebsocketClient.request({signal}) sends the cancel notification
automatically when the signal fires.
{ method: string; kind: "remote_notification"; initiator: "frontend"; auth: null; side_effects: true; input: ZodObject<{ request_id: ZodUnion<readonly [ZodString, ZodNumber]>; }, $strict>; output: ZodVoid; async: true; description: string; } ActionSpec for the shared cancel. auth: null matches every other
remote-notification spec — upgrade-time auth has already admitted the
socket, so per-action auth on a fire-and-forget notification is moot. The
per-connection {request_id → AbortController} map enforces socket-scoped
ownership naturally: a different socket's cancel for the same id misses
in its own map.
(): void Placeholder handler — cancel semantics are owned by register_action_ws, not invoked per-handler. Exported for symmetry with the Action tuple shape; the dispatcher short-circuits cancel notifications before any handler lookup happens.
void ZodObject<{ request_id: ZodUnion<readonly [ZodString, ZodNumber]>; }, $strict> Params for the cancel notification. request_id is the id of the
pending request to abort. Must match the id of a request sent on the
same socket; cancels from other sockets (or for unknown ids) are ignored.