"""Session lifecycle: active-session slot leases, finalize/teardown/close, turn interrupt, WS-orphan reap scheduling, transport-scoped close.

Bodies are rebound onto server.py's globals at install time (see
method_ctx.bind_module), so they reference server.py globals bare.
"""

from __future__ import annotations

import contextlib

from .method_ctx import HandlerRegistry, bind_module

_registry = HandlerRegistry()


def _notify_session_boundary(event_type: str, session_id: str | None, platform: str | None = None) -> None:
    """Fire session lifecycle hooks with CLI parity."""
    with contextlib.suppress(Exception):
        from hermes_cli.lifecycle import finalize_session, invoke_hook

        if event_type == "on_session_finalize":
            finalize_session(session_id=session_id, platform=_resolve_agent_platform(platform))
        else:
            invoke_hook(event_type, session_id=session_id, platform=_resolve_agent_platform(platform))


_SESSION_OWNERSHIP_UNAVAILABLE = "Hermes could not safely reserve this session. Try again."

_AUTOMATIC_SESSION_END_REASONS = frozenset({
    "ws_orphan_reap", "ws_disconnect", "idle_timeout", "lru_evict", "tui_shutdown",
})


def _claim_active_session_slot(
    session_key: str, *, live_session_id: str, surface: str = "tui", profile_home: str | Path | None = None
) -> tuple[Any, str | None]:
    track_liveness = str(surface or "").strip().lower() == "desktop"
    try:
        from hermes_cli.active_sessions import try_acquire_active_session

        return try_acquire_active_session(
            session_id=session_key,
            surface=surface,
            config=_load_cfg(),
            metadata={"live_session_id": live_session_id},
            registry_home=profile_home,
            track_liveness=track_liveness,
        )
    except Exception as exc:
        logger.warning("Failed to claim active session slot: %s", exc)
        # Fail CLOSED regardless of surface: an errored claim has NOT proven the session
        # unowned, and proceeding lease-less is a silent double-writer hole.
        return (None, _SESSION_OWNERSHIP_UNAVAILABLE)


def _ensure_active_session_slot(sid: str, session: dict) -> str | None:
    """Claim this session's cap slot on its first real turn; None when ok.

    session.create/resume deliberately do NOT claim: tile paints, reconnect-resumes and
    abandoned drafts would hold invisible slots (no DB row) that starve the messaging
    gateway sharing the cap. Anything holding a slot must be user-visible.
    """
    if session.get("active_session_lease") is not None:
        return None
    lease, limit_message = _claim_active_session_slot(
        str(session.get("session_key") or ""),
        live_session_id=sid,
        surface=_session_source(session),
        profile_home=session.get("profile_home"),
    )
    if limit_message is not None:
        return limit_message
    session["active_session_lease"] = lease
    return None


def _release_active_session_lease(lease) -> bool:
    if lease is None:
        return True
    attempts = 3 if getattr(lease, "track_liveness", False) else 1
    for attempt in range(attempts):
        try:
            lease.release()
            break
        except Exception:
            if attempt + 1 >= attempts:
                logger.warning("Failed to release active session slot", exc_info=True)
                return False
            time.sleep(0.05 * (attempt + 1))
    return bool(getattr(lease, "released", True) or not getattr(lease, "enabled", True))


def _release_active_session_slot(session: dict | None) -> bool:
    if not session:
        return True
    lease = session.get("active_session_lease")
    if _release_active_session_lease(lease):
        if session.get("active_session_lease") is lease:
            session.pop("active_session_lease", None)
        return True
    return False


@contextlib.contextmanager
def _other_runtime_lease_guard(session_id: str, session: dict):
    """Release this runtime and lock sibling ownership through the DB write."""
    lease = session.get("active_session_lease")
    try:
        from hermes_cli.active_sessions import (
            active_session_liveness_guard,
            release_active_session_liveness_guard,
        )
    except Exception as exc:
        logger.warning(
            "Failed to load active session ownership guard; preserving session %s: %s", session_id, exc
        )
        yield True
        return

    last_error: Exception | None = None
    stack = contextlib.ExitStack()
    for attempt in range(3):
        try:
            if lease is not None and getattr(lease, "enabled", False):
                guard = release_active_session_liveness_guard(lease, session_id)
            else:
                guard = active_session_liveness_guard(session_id, registry_home=session.get("profile_home"))
            active = stack.enter_context(guard)
            break
        except Exception as exc:
            stack.close()
            stack = contextlib.ExitStack()
            last_error = exc
            if attempt < 2:
                time.sleep(0.05 * (attempt + 1))
    else:
        logger.warning(
            "Failed to inspect active session leases; preserving session %s: %s", session_id, last_error
        )
        yield True
        return
    try:
        yield active
    finally:
        stack.close()
        if (
            lease is not None
            and getattr(lease, "released", False)
            and session.get("active_session_lease") is lease
        ):
            session.pop("active_session_lease", None)


def _transfer_active_session_slot(sid: str, session: dict, *, new_session_id: str) -> bool:
    if not new_session_id:
        return False
    lease = session.get("active_session_lease")
    if lease is None:
        return True
    try:
        from hermes_cli.active_sessions import transfer_active_session

        if transfer_active_session(lease, session_id=new_session_id, metadata={"live_session_id": sid}):
            return True
    except Exception:
        logger.debug("Failed to transfer active session slot", exc_info=True)

    if getattr(lease, "track_liveness", False):
        return False

    # Fallback (entry pruned / pid-check transiently failed): reserve the new slot BEFORE
    # releasing the old one so a gateway at the cap can't grab the freed slot and leave
    # this session lease-less. On reserve failure KEEP the old lease.
    new_lease, limit_message = _claim_active_session_slot(
        new_session_id,
        live_session_id=sid,
        surface=_session_source(session),
        profile_home=session.get("profile_home"),
    )
    if new_lease is not None:
        old_lease = session.pop("active_session_lease", None)
        if old_lease is not None:
            try:
                old_lease.release()
            except Exception:
                logger.debug("Failed to release stale active session slot", exc_info=True)
        session["active_session_lease"] = new_lease
        return True
    if limit_message:
        logger.warning(
            "Compression session lease re-anchor failed (kept old lease): "
            "sid=%s new_session_id=%s reason=%s",
            sid, new_session_id, limit_message,
        )
    return False


# Sources this backend must never end in state.db: the messaging gateway owns those
# sessions and the TUI is only a viewer (ending one causes the Groundhog Day routing
# loop, see _finalize_session). Self-created and CLI sources are NOT gateway-owned.
_NON_GATEWAY_SOURCES = frozenset({
    "", "tui", "cli", "webui", "desktop", "cron", "kanban", "subagent", "test",
    "local", "acp", "webhook", "api_server", "msgraph_webhook",
})


def _is_gateway_owned_source(source: str) -> bool:
    """True when ``source`` is a messaging-gateway platform owning its session lifecycle.

    Structural: any source resolving to a gateway ``Platform`` (enum member or plugin via
    ``Platform._missing_``) counts, so new platforms are covered automatically. Self-owned
    sources (``local``/``webhook``/``api_server`` are Platform members) are excluded explicitly.
    """
    src = (source or "").strip().lower()
    if src in _NON_GATEWAY_SOURCES:
        return False
    try:
        from gateway.config import Platform

        Platform(src)  # raises ValueError for arbitrary non-platform strings
        return True
    except Exception:
        return False


def _lifecycle_own_sid(session: dict, sid_hint: str = "") -> str:
    """Live UI sid for ``session``: hint, stamped ``_sid``, else registry scan."""
    own_sid = str(sid_hint or session.get("_sid") or "")
    if not own_sid:
        try:
            with _sessions_lock:
                for _cand_sid, _cand in _sessions.items():
                    if _cand is session:
                        own_sid = _cand_sid
                        break
        except Exception:
            own_sid = ""
    return own_sid


def _finalize_session(session: dict | None, end_reason: str = "tui_close") -> None:
    """Best-effort finalize hook + memory commit; mirrors the CLI exit path so a
    force-quit mid-turn (double Ctrl-C, terminal close, SIGHUP) loses nothing."""
    if not session or session.get("_finalized"):
        return
    session["_finalized"] = True
    history_ready = session.get("resume_history_ready")
    if history_ready is not None and not history_ready.is_set():
        session["resume_history_error"] = "session resume cancelled"
        history_ready.set()
    _desktop_automatic_cleanup = (
        end_reason in _AUTOMATIC_SESSION_END_REASONS
        and _session_source(session).strip().lower() == "desktop"
    )
    # Automatic Desktop cleanup releases its lease inside the lock-held lifecycle guard
    # below; explicit close and non-Desktop paths keep force/end semantics.
    if not _desktop_automatic_cleanup:
        _release_active_session_slot(session)
    stop_event = session.get("_notif_stop")
    if stop_event is not None:
        stop_event.set()

    agent = session.get("agent")
    lock = session.get("history_lock")
    with (lock if lock is not None else contextlib.nullcontext()):
        history = list(session.get("history", []))

    # Persist via ``_persist_session``'s marker-based dedup (same contract as the
    # gateway-shutdown flush). Do NOT pass ``conversation_history``: ``session["history"]``
    # and ``_session_messages`` alias the SAME list after a turn, so the flush would treat
    # every message as durable and skip it — data loss when finalize is the sole persist
    # path after a WS disconnect/restart.
    if agent is not None and hasattr(agent, "_persist_session"):
        snapshot = getattr(agent, "_session_messages", None)
        if snapshot:
            with contextlib.suppress(Exception):
                agent._persist_session(snapshot)

    # interrupted=True so crash-recovery plugins can flush state (mirrors cli.py atexit).
    if agent is not None:
        with contextlib.suppress(Exception):
            from hermes_cli.lifecycle import invoke_hook

            invoke_hook(
                "on_session_end",
                session_id=getattr(agent, "session_id", None) or session.get("session_key", ""),
                completed=False,
                interrupted=True,
                model=getattr(agent, "model", "unknown"),
                platform=getattr(agent, "platform", None) or "tui",
            )

    if agent is not None and history and hasattr(agent, "commit_memory_session"):
        with contextlib.suppress(Exception):
            agent.commit_memory_session(history)

    session_key = session.get("session_key")
    session_id = getattr(agent, "session_id", None) or session_key
    _notify_session_boundary("on_session_finalize", session_id, _session_source(session))

    # End the state.db row so it doesn't linger as a ghost in /resume. Use session_id
    # (agent.session_id), not session_key: after compression the key may be the stale
    # ended parent while session_id is the live continuation.
    if _desktop_automatic_cleanup and not session_id:
        _release_active_session_slot(session)
    _lifecycle_guard = (
        _other_runtime_lease_guard(session_id, session)
        if _desktop_automatic_cleanup and session_id
        else contextlib.nullcontext(False)
    )
    with _lifecycle_guard as _other_runtime_owns_lifecycle:
        _tui_owns_lifecycle = not _other_runtime_owns_lifecycle
        if _other_runtime_owns_lifecycle:
            logger.info(
                "Preserving session %s during %s: another backend owns an active lease",
                session_id, end_reason,
            )
        if session_id:
            with contextlib.suppress(Exception):
                # The *session's* profile state.db (app-global remote mode), not the launch profile's.
                with _session_db(session) as db:
                    if db is not None:
                        # Never end gateway-originated sessions (Groundhog Day loop: the
                        # gateway's self-heal recovers to the parent, compression splits back
                        # to the reaped child, repeat on every message).
                        row = db.get_session(session_id)
                        source = (row or {}).get("source", "")
                        if _is_gateway_owned_source(source):
                            _tui_owns_lifecycle = False
                        elif _tui_owns_lifecycle:
                            db.end_session(session_id, end_reason)

    # In-flight async delegations end WITH the session (no return address left). Always
    # interrupt by THIS live UI sid; by durable session_key only when the TUI owns the
    # lifecycle — closing a viewer tab must not kill the gateway's own background work.
    with contextlib.suppress(Exception):
        from tools.async_delegation import interrupt_for_session

        interrupt_for_session(
            session_key=str(session_key or "") if _tui_owns_lifecycle else "",
            origin_ui_session_id=_lifecycle_own_sid(session),
            reason=end_reason,
        )

    # Close the slash-worker in this single ``_finalized``-guarded chokepoint so a direct
    # _finalize_session caller can't leak it. Idempotent: close() is poll()-guarded.
    with contextlib.suppress(Exception):
        worker = session.get("slash_worker")
        if worker:
            worker.close()


# End reasons where the BACKEND reclaimed a session the client never asked to close;
# without a signal the client's next prompt fails against a forgotten id. Client-initiated
# reasons (``tui_close`` etc.) are deliberately absent.
_RECLAIM_END_REASONS = frozenset({"idle_timeout", "lru_evict", "ws_orphan_reap"})


def _announce_session_reclaimed(session: dict, end_reason: str) -> None:
    """Tell connected clients a session was reclaimed out from under them.

    Broadcast, not session-targeted: reap paths run on timer threads with no contextvar
    binding and the WS-orphan case has lost its transport, so ``_emit`` would bottom out
    on stdio. Best-effort; never breaks teardown.
    """
    if end_reason not in _RECLAIM_END_REASONS:
        return
    try:
        _broadcast_global_event(
            "session.reclaimed",
            {
                "session_id": str(session.get("_sid") or ""),
                "stored_session_id": str(session.get("session_key") or ""),
                "reason": end_reason,
            },
        )
    except Exception:
        logger.debug("session.reclaimed broadcast failed", exc_info=True)


def _teardown_session(session: dict | None, *, end_reason: str = "tui_close") -> None:
    """Fully tear down a session: finalize, unregister notifier, close agent.

    Shared by ``session.close`` and the orphaned-WS reaper. The slash-worker is closed in
    ``_finalize_session`` (the single chokepoint), NOT here. Idempotent via ``_finalized``.
    """
    if not session:
        return
    _finalize_session(session, end_reason=end_reason)
    _announce_session_reclaimed(session, end_reason)
    with contextlib.suppress(Exception):
        from tools.approval import unregister_gateway_notify

        if key := session.get("session_key"):
            unregister_gateway_notify(key)
    with contextlib.suppress(Exception):
        agent = session.get("agent")
        if agent is not None and hasattr(agent, "close"):
            agent.close()


def _attach_worker(sid: str, session: dict, worker) -> None:
    """Store worker on session iff sid still maps to it, else close it — a
    concurrent teardown already popped the session and would orphan the worker."""
    with _sessions_lock:
        if _sessions.get(sid) is session:
            session["slash_worker"] = worker
            return
    worker.close()


def _pop_session_by_id(sid: str) -> dict | None:
    """Atomically detach one live session from the registry — the ownership claim for
    teardown (a concurrent close/reaper then no-ops). Separate from ``_teardown_session``
    because finalization does slow external work that must not run under
    ``_session_resume_lock``."""
    with _sessions_lock:
        session = _sessions.get(sid)
        if session is not None:
            session["_closing"] = True
            _sessions.pop(sid, None)
    if session is None:
        return None
    # Out of _sessions now, so teardown can't recover the live id by scanning — stamp it.
    session["_sid"] = sid
    return session


def _teardown_popped_session(session: dict | None, *, end_reason: str = "tui_close") -> bool:
    """Finish a close after the caller has atomically detached the session."""
    if session is None:
        return False
    run_thread = session.get("_run_thread")
    if end_reason != "tui_shutdown" and run_thread is not None and run_thread is not threading.current_thread():
        try:
            if run_thread.is_alive():
                run_thread.join(timeout=_TURN_SETTLE_BEFORE_CLOSE_SECONDS)
            if run_thread.is_alive():
                logger.warning(
                    "session turn thread still alive after %.1fs teardown grace",
                    _TURN_SETTLE_BEFORE_CLOSE_SECONDS,
                )
        except Exception:
            logger.debug("failed waiting for session turn thread", exc_info=True)
    _teardown_session(session, end_reason=end_reason)
    return True


def _close_session_by_id(
    sid: str, *, end_reason: str = "tui_close", predicate: Callable[[dict], bool] | None = None
) -> bool:
    """Idempotent teardown funnel for callers with no resume race (resume-sensitive callers
    pop under ``_session_resume_lock`` and call ``_teardown_popped_session`` after releasing
    it). Automatic reapers pass ``predicate`` to revalidate under ``_sessions_lock`` right
    before the claim, so a stale scan can't close a session that reattached."""
    if predicate is None:
        session = _pop_session_by_id(sid)
    else:
        with _sessions_lock:
            current = _sessions.get(sid)
            if current is None or not predicate(current):
                return False
            session = _pop_session_by_id(sid)
    return _teardown_popped_session(session, end_reason=end_reason)


def _ws_session_is_detached(session: dict | None) -> bool:
    """True if a live session is still bound to the disconnected-WS sentinel."""
    return bool(
        session and not session.get("_finalized") and session.get("transport") is _detached_ws_transport
    )


def _ws_session_is_orphaned(session: dict | None) -> bool:
    """True if a WS session sits on ``_detached_ws_transport`` (where
    ``handle_ws`` parks disconnected clients) with no in-flight turn."""
    return bool(_ws_session_is_detached(session) and not session.get("running"))


def _interrupt_session_turn(sid: str, session: dict, *, request_id: str | None = None) -> bool:
    """Apply the shared ``session.interrupt`` contract to one claimed session; returns
    whether the compute-host control channel was used. The WS orphan reaper reuses this so
    a dead client gets the same partial-history and queued-prompt semantics."""
    use_compute_host = _session_uses_compute_host(session)
    should_interrupt = bool(session.get("running"))
    run_thread_alive = False

    if use_compute_host:
        # The host owns the live turn (parent `running` can lag a blocked tool), so let it
        # decide. Gate on `_compute_host_active`: HostSupervisor.interrupt() calls start(),
        # so forwarding blindly for a lazy session would spawn a child just to interrupt.
        if should_interrupt or session.get("_compute_host_active"):
            _get_compute_host_supervisor().interrupt(sid, request_id=request_id)
    else:
        run_thread = session.get("_run_thread")
        run_thread_alive = run_thread is not None and run_thread.is_alive()

    with session["history_lock"]:
        session["_turn_cancel_requested"] = True
        session["queued_prompt"] = None
        session.pop("queued_prompts", None)
        session["_queued_prompt_generation"] = int(session.get("_queued_prompt_generation", 0)) + 1

    if not use_compute_host:
        if should_interrupt:
            from agent.interrupt_compat import request_hard_interrupt

            request_hard_interrupt(session.get("agent"))
        if not run_thread_alive:
            with session["history_lock"]:
                if session.get("running"):
                    session["running"] = False
                    _clear_inflight_turn(session)

    _clear_pending(sid)
    with contextlib.suppress(Exception):
        from tools.approval import resolve_gateway_approval

        resolve_gateway_approval(session["session_key"], "deny", resolve_all=True)
    return use_compute_host


def _session_owns_durable_lifecycle(session_id: str | None) -> bool:
    """Whether this TUI/desktop session may end its durable DB row by key
    (never for gateway-originated sessions — the TUI is only a viewer there)."""
    if not session_id:
        return True
    try:
        db = _get_db()
        if db is None:
            return True
        row = db.get_session(session_id)
        return not _is_gateway_owned_source((row or {}).get("source", ""))
    except Exception:
        return True


def _session_async_delegation_selectors(session: dict | None, *, sid_hint: str = "") -> tuple[str, str]:
    """Ownership selectors for async background work tied to one UI session."""
    if not session:
        return "", ""
    own_sid = _lifecycle_own_sid(session, sid_hint)
    agent = session.get("agent")
    session_key = str(session.get("session_key") or "")
    session_id = getattr(agent, "session_id", None) or session_key
    owned_session_key = session_key if _session_owns_durable_lifecycle(session_id) else ""
    return own_sid, owned_session_key


def _session_has_active_delegations(sid: str, session: dict | None = None) -> bool:
    """True when UI session ``sid`` still owns live background work — by live UI sid AND,
    when the TUI owns the durable lifecycle (never for gateway-viewer tabs), by durable
    session_key so a delegation from an earlier tab of the same session keeps it alive."""
    if session is None:
        with _sessions_lock:
            session = _sessions.get(sid)
    own_sid, owned_session_key = _session_async_delegation_selectors(session, sid_hint=sid)
    if not own_sid and not owned_session_key:
        return False
    try:
        from tools.async_delegation import has_live_for_session

        return has_live_for_session(session_key=owned_session_key, origin_ui_session_id=own_sid)
    except Exception:
        logger.debug("Failed to query active delegations for UI session %s", sid, exc_info=True)
        # A transient registry/import failure must not become destructive cleanup.
        return True


# One pending WS-orphan reap Timer per live sid; guarded by _sessions_lock. Cancelled by
# _cancel_ws_orphan_reap from every resume/reuse/transport-rebind path — otherwise a reap
# could fire on a reattached session and trigger a reap->broadcast->resume storm.
_pending_ws_reaps: dict[str, threading.Timer] = {}


def _cancel_ws_orphan_reap(sid: str) -> None:
    """Cancel a pending WS-orphan reap for ``sid`` (client came back). Called from every
    path that re-binds a live transport; closes the fired-but-not-run Timer race and stops
    dead Timers accumulating on flappy clients."""
    with _sessions_lock:
        timer = _pending_ws_reaps.pop(sid, None)
    if timer is not None:
        with contextlib.suppress(Exception):
            timer.cancel()


def _ws_orphan_turn_activity_is_fresh(session: dict) -> bool:
    """Whether a detached RUNNING turn's activity clock (``_touch_activity``, the watchdog's
    clock) is still fresh — the reaper must NOT interrupt healthy detached work (closed
    laptop, backgrounded app). Conservative fallbacks keep the wedged-turn safety net:
    disabled threshold, missing/opaque agent, unreadable summary or never-stamped clock all
    report NOT fresh, i.e. eligible for interrupt-at-grace."""
    if _WS_ORPHAN_ACTIVITY_STALE_S <= 0:
        return False
    agent = session.get("agent")
    summary_fn = getattr(agent, "get_activity_summary", None)
    if not callable(summary_fn):
        return False
    try:
        elapsed = summary_fn().get("seconds_since_activity")
        return elapsed is not None and float(elapsed) < _WS_ORPHAN_ACTIVITY_STALE_S
    except Exception:
        return False


def _schedule_ws_orphan_reap(sid: str, *, delay_s: float | None = None) -> None:
    """After a grace window, reap session ``sid`` iff it's still orphaned. Called from the
    WS-disconnect path; a reconnect or ``session.resume`` cancels the reap by re-binding a
    live transport. Disabled when the grace is 0."""
    if _WS_ORPHAN_REAP_GRACE_S <= 0:
        return

    def _reap() -> None:
        # Serialize the re-check against session.resume (rebinds under _session_resume_lock).
        # Claim teardown by popping under both locks, then release the resume lock before
        # slow finalization. Ordering is always resume_lock -> sessions_lock (RLock).
        reschedule_delay = None
        interrupt_session = None
        session = None
        with _session_resume_lock:
            # Drop this Timer's registration so a concurrent _cancel_ws_orphan_reap can't
            # cancel a dead Timer while a rescheduled one (registered below) is the owner.
            with _sessions_lock:
                _pending_ws_reaps.pop(sid, None)
            current = _sessions.get(sid)
            if current is None or not _ws_session_is_detached(current):
                return
            if _session_has_active_delegations(sid, current):
                reschedule_delay = _WS_ORPHAN_REAP_GRACE_S
            elif current.get("running"):
                if not current.get("_client_gone_interrupt_requested") and (
                    _ws_orphan_turn_activity_is_fresh(current)
                ):
                    # Client-absent but producing: keep running detached (the sentinel
                    # buffers emits) and re-check each grace interval.
                    logger.debug(
                        "client_gone sid=%s action=defer (turn activity fresh; stale threshold %.0fs)",
                        sid, _WS_ORPHAN_ACTIVITY_STALE_S,
                    )
                    reschedule_delay = _WS_ORPHAN_REAP_GRACE_S
                else:
                    # Mid-turn detached sessions must never drop the single Timer: interrupt
                    # once after grace, then poll until turn-finalization settles.
                    polls = int(current.get("_client_gone_interrupt_polls") or 0) + 1
                    current["_client_gone_interrupt_polls"] = polls
                    if polls > _WS_ORPHAN_INTERRUPT_REAP_MAX_POLLS:
                        # Never settled inside the budget — force-reap rather than park forever.
                        logger.error(
                            "client_gone sid=%s: turn did not settle after %d "
                            "interrupt polls (%.0fs) — force-reaping detached session",
                            sid, polls - 1, (polls - 1) * _WS_ORPHAN_INTERRUPT_REAP_POLL_S,
                        )
                        session = _pop_session_by_id(sid)
                    else:
                        if not current.get("_client_gone_interrupt_requested"):
                            current["_client_gone_interrupt_requested"] = True
                            interrupt_session = current
                        reschedule_delay = _WS_ORPHAN_INTERRUPT_REAP_POLL_S
            else:
                session = _pop_session_by_id(sid)

        if interrupt_session is not None:
            try:
                isolated = _interrupt_session_turn(sid, interrupt_session, request_id=f"client-gone-{sid}")
                logger.info("client_gone sid=%s action=interrupt turn_isolation=%s", sid, isolated)
            except Exception:
                logger.exception("client_gone interrupt failed sid=%s", sid)
                with _sessions_lock:
                    if _sessions.get(sid) is interrupt_session:
                        interrupt_session.pop("_client_gone_interrupt_requested", None)

        if reschedule_delay is not None:
            _schedule_ws_orphan_reap(sid, delay_s=reschedule_delay)
            return
        if session is not None and session.get("_client_gone_interrupt_requested"):
            logger.info("client_gone sid=%s action=reap", sid)
        _teardown_popped_session(session, end_reason="ws_orphan_reap")

    timer = threading.Timer(_WS_ORPHAN_REAP_GRACE_S if delay_s is None else max(0.0, delay_s), _reap)
    timer.daemon = True
    with _sessions_lock:
        prior = _pending_ws_reaps.pop(sid, None)
        _pending_ws_reaps[sid] = timer
    if prior is not None:
        with contextlib.suppress(Exception):
            prior.cancel()
    timer.start()


def _close_sessions_for_transport(transport, *, end_reason: str = "ws_disconnect") -> tuple[int, int]:
    """Single WS-disconnect teardown entry point: reap close_on_disconnect sessions
    (sidecar/dashboard) immediately and re-point the rest at the detached transport so
    later emits don't hit a dead socket; those go to the grace-windowed WS-orphan reaper.
    Returns ``(reaped, detached)`` counts."""
    with _sessions_lock:
        owned = [(sid, s) for sid, s in _sessions.items() if s.get("transport") is transport]
    reaped = 0
    detached = 0
    for sid, session in owned:
        claimed_for_teardown = None
        should_schedule_reap = False
        # session.resume fast-path rebinds under _session_resume_lock: take it before
        # re-checking so a reconnect can't move the transport between check and claim.
        with _session_resume_lock:
            with _sessions_lock:
                current = _sessions.get(sid)
                if current is not session:
                    continue
                if current.get("transport") is not transport:
                    # The reconnect owns this session now; drop only the old viewer registration.
                    (current.get("viewers") or {}).pop(transport, None)
                    continue
                if current.get("close_on_disconnect"):
                    claimed_for_teardown = _pop_session_by_id(sid)
                else:
                    # Point at the drop sentinel (NOT real stdio) so _ws_session_is_orphaned
                    # recognizes it; standalone `hermes --tui` keeps real _stdio. UNLESS
                    # another window (multi-window pop-out viewer) still shows the session:
                    # re-bind to the most recent surviving viewer instead of stranding it.
                    viewers = current.get("viewers") or {}
                    viewers.pop(transport, None)
                    remaining = [
                        (ts, vt) for vt, ts in viewers.items()
                        if vt is not transport and not _transport_is_dead(vt)
                    ]
                    if remaining:
                        remaining.sort(key=lambda item: item[0])
                        current["transport"] = remaining[-1][1]
                    else:
                        current["transport"] = _detached_ws_transport
                        current.pop("_client_gone_interrupt_requested", None)
                        should_schedule_reap = True
        if claimed_for_teardown is not None:
            if _teardown_popped_session(claimed_for_teardown, end_reason=end_reason):
                reaped += 1
        elif should_schedule_reap:
            detached += 1
            with contextlib.suppress(Exception):
                _schedule_ws_orphan_reap(sid)
    return reaped, detached


def register(server) -> None:
    """Publish this module's helpers + handlers onto ``server``, rebound to its globals."""
    bind_module(globals(), server, skip=("_",))