ticket: return runtime websocket stream to planning

.yoi/tickets/00001KVZKSTJT/item.md

@@ -1,8 +1,8 @@
 ---
 title: 'worker-runtimeにWebSocket event stream serverを追加する'
-state: 'ready'
+state: 'planning'
 created_at: '2026-06-25T14:44:02Z'
-updated_at: '2026-06-25T16:34:16Z'
+updated_at: '2026-06-25T16:42:14Z'
 assignee: null
 ---
 

.yoi/tickets/00001KVZKSTJT/thread.md

@@ -21,4 +21,32 @@ Marked ready by `yoi ticket state`.
 Marked ready by `yoi ticket state`.
 
 
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-06-25T16:42:14Z from: ready to: planning reason: cli_state field: state -->
+
+## State changed
+
+State changed to `planning`.
+
+
+---
+
+<!-- event: decision author: hare at: 2026-06-25T16:42:14Z -->
+
+## Decision
+
+Returned to planning because the current ticket is not concrete enough.
+
+The purpose is specifically observation: Backend subscribes to a Runtime-owned WebSocket stream to receive Worker output and related runtime/worker events. It is not a command channel, not browser-facing, and not the path for sending user input.
+
+Before this can be ready, define the event model and protocol boundary concretely:
+- which Worker output events are streamed (text delta/final, reasoning visibility policy, tool call lifecycle, status, run started/completed/errored, usage, diagnostics);
+- whether the stream is runtime-wide, worker-scoped, or both;
+- event envelope shape, event id/cursor semantics, ordering, backlog, reconnect behavior, and unknown/expired cursor handling;
+- relationship between streamed output and transcript projection/event log persistence;
+- Backend client/proxy expectations and how Browser receives the projection without connecting directly to Runtime;
+- what is deliberately excluded from the stream, such as raw provider trace or raw full session log.
+
+
 ---