The backend never sent a JSON-RPC request; when it needed an answer from the
renderer it hand-correlated a `*.request` notification with a later `*.respond`
method through four module-level dicts, a timeout thread and 13 derived
`*.expire` names, plus a separate reconnect snapshot per prompt kind. That is a
second request/response layer built on a protocol that already has one.
`tui_gateway/server_requests.py` sends `{id: "srq-…", method, params}` and
blocks on the response frame with that id (string ids never collide with the
clients' integer ids). One `request.cancel {id, method, reason}` notification
withdraws a request on timeout / interrupt / session close. `open_requests` on
`session.resume` / `session.activate` / `session.events.since` re-delivers
unanswered requests after a reconnect; the shared TypeScript channel does that
itself before the caller sees the result. Batch clarify keeps its per-question
locks as a normal `clarify.lock` RPC (the last lock resolves the request).
Approvals stay queue-backed (`tools.approval` owns the timeout, `/approve all`,
coalescing): the request resolves the queue entry and the entry's own
resolution withdraws the request through `register_gateway_settle`.
Deleted: `_block`, `_respond`, `_pending`, `_answers`,
`_pending_prompt_payloads`, `_batch_clarify`, `_EXPIRING_REQUESTS`, the
`*.respond` methods, every `*.request` / `*.expire` event, `pending_clarify`.
Compute-host (turn isolation) mirrors the child's open request and relays the
response frame / lock to it. Desktop, TUI and shared clients register
`onRequest` handlers where they used to switch on `*.request` events; answers
are response frames over the socket the request arrived on, so #91684's
owner-routing class cannot recur for prompts.
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