Cluster mode: SubscribeToTask on replica with paused ActiveTask returns stale INPUT_REQUIRED and closes

Finding: In a2a-sdk 1.2.2 cluster mode (VersionedDatabaseTaskStore plus DatabaseTaskEventStream), an external report says SubscribeToTask on a replica that ran an earlier turn ending in INPUT_REQUIRED returns a stale INPUT_REQUIRED snapshot and closes the stream, while a later turn is still running on another replica (https://github.com/a2aproject/a2a-python/issues/1323). This is an external report; KFA did not reproduce it. Reported scenario: replica A runs turn 1 and pauses with INPUT_REQUIRED. The client's reply lands on replica B, which runs turn 2 (WORKING then COMPLETED). If the client resubscribes during turn 2 and is routed to A, A returns Task(INPUT_REQUIRED) and closes. A replica C that never saw the task returns Task(WORKING), then status updates through COMPLETED. The reporter says this happened in 5 of 5 runs, and GetTask afterwards showed COMPLETED (issue body). The reported effect is that a client may wrongly conclude the agent is still waiting for input. No exception text was reported. Reporter's analysis (hypothesis, not maintainer-confirmed): on_subscribe_to_task in default_request_handler_v2.py takes a local fast path whenever the replica's ActiveTaskRegistry has an entry for the task. After a turn ends in an interrupted state the ActiveTask stays registered but idle. Subscribing to it returns the TaskManager's cached snapshot without invalidating it, then follows a local in-memory queue that never receives events produced on B (issue body). The reporter notes that the handler has already read the current snapshot and version from the versioned store, so the remote subscribe path would give the right answer. The reporter also says the code is unchanged on main, but other versions were not checked here. Thread status: one commenter, with GitHub association NONE (so not a maintainer-confirmed cause), says the root-cause analysis is correct and prefers the first proposed fix: use the local path only while the local ActiveTask has a request in flight, otherwise use the remote subscribe path. The commenter mentions PR #1327 as adding ActiveTask.request_in_flight() and updating the condition (https://github.com/a2aproject/a2a-python/issues/1323#issuecomment-6077538149). That PR was not supplied, so its review, merge and release status are unknown. The issue is open and no released fix is shown. Proposed mitigation (source-backed, not verified by KFA): the same commenter suggests subclassing DefaultRequestHandlerV2 and overriding on_subscribe_to_task to check whether the local task's execution lock is held, falling back to _subscribe_remote when the task is idle or not running locally. No code or testing was provided, so treat it as a lead requiring local validation. Limitations: external report only; the reproduction output was reported by the author and not rerun; only 1.2.2 is named; fix and release status are unknown.