nautilus_derive/websocket/

client.rs

// -------------------------------------------------------------------------------------------------
//  Copyright (C) 2015-2026 Nautech Systems Pty Ltd. All rights reserved.
//  https://nautechsystems.io
//
//  Licensed under the GNU Lesser General Public License Version 3.0 (the "License");
//  You may not use this file except in compliance with the License.
//  You may obtain a copy of the License at https://www.gnu.org/licenses/lgpl-3.0.en.html
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
// -------------------------------------------------------------------------------------------------

//! `tokio-tungstenite`-backed WebSocket client for the Derive JSON-RPC stream.
//!
//! [`DeriveWebSocketClient`] orchestrates the connection lifecycle and exposes
//! a typed surface for `public/login` + the initial `ticker` channel. The
//! actual I/O runs in `super::handler::FeedHandler`; the client communicates
//! with it through an unbounded command channel and consumes
//! [`DeriveWsMessage`] events.

use std::{
    fmt::Debug,
    sync::{
        Arc,
        atomic::{AtomicBool, AtomicU8, AtomicU64, Ordering},
    },
    time::Duration,
};

use alloy::signers::local::PrivateKeySigner;
use arc_swap::ArcSwap;
use dashmap::DashMap;
#[cfg(test)]
use nautilus_common::live::get_runtime;
use nautilus_core::{
    UUID4,
    string::secret::{REDACTED, SecretString},
};
use nautilus_live::{
    SocketControl,
    task::{SharedTaskSlot, TaskJoinOutcome, TaskSlot, finish_task},
};
use nautilus_network::{
    http::create_standard_nautilus_headers,
    mode::ConnectionMode,
    ratelimiter::clock::MonotonicClock,
    websocket::{
        AuthTracker, TransportBackend, WebSocketClient, WebSocketConfig, channel_message_handler,
    },
};
use serde::{Serialize, de::DeserializeOwned};
use serde_json::Value;
use ustr::Ustr;
use zeroize::Zeroizing;

use super::{
    error::{DeriveWsError, Result},
    handler::{
        DeriveWsMessage, FeedHandler, HandlerCommand, orderbook_subscribe_params,
        ticker_subscribe_params, trades_subscribe_params,
    },
    messages::{
        DeriveWsChannel, WsLoginParams, WsLoginResult, WsSubscribeParams, WsSubscribeResult,
        WsUnsubscribeParams, WsUnsubscribeResult, methods, orderbook_channel, ticker_channel,
        trades_channel,
    },
};
use crate::{
    common::{
        consts::{
            RECONNECT_BACKOFF_FACTOR, RECONNECT_BASE_BACKOFF, RECONNECT_JITTER_MS,
            RECONNECT_MAX_BACKOFF, RECONNECT_TIMEOUT, WS_HEARTBEAT_SECS, WS_HEARTBEAT_TIMEOUT,
            WS_REQUEST_TIMEOUT,
        },
        enums::DeriveEnvironment,
        rate_limit::{
            DeriveRateLimiter, FixedWindowLimiter, FixedWindowLimits, RateClass,
            rate_class_for_method,
        },
        urls,
    },
    http::{
        models::{
            DeriveCancelByInstrumentResult, DeriveCancelByLabelResult, DeriveEmptyResult,
            DeriveOpenOrdersResult, DeriveOrder, DeriveOrderResult, DeriveReplaceOutcome,
            DeriveReplaceResult,
        },
        query::{
            DeriveCancelAllParams, DeriveCancelByInstrumentParams, DeriveCancelByLabelParams,
            DeriveCancelParams, DeriveCancelTriggerOrderParams, DeriveGetTriggerOrdersParams,
            DeriveOrderParams, DeriveReplaceParams, DeriveTriggerOrderParams,
        },
    },
    signing::auth::build_ws_login,
};

/// Credentials for `public/login`. The session-key signer never escapes the
/// client; only the wallet address is exposed via [`Debug`].
#[derive(Clone)]
pub struct DeriveWsCredentials {
    /// Derive Chain smart-contract wallet address (`0x`-prefixed, 42 chars).
    pub wallet_address: String,
    /// secp256k1 session-key signer.
    pub signer: PrivateKeySigner,
}

impl DeriveWsCredentials {
    /// Constructs credentials by parsing `session_key_hex` into a signer.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::Transport`] when the session-key hex cannot be parsed.
    pub fn new(wallet_address: impl Into<String>, session_key_hex: &str) -> Result<Self> {
        let signer: PrivateKeySigner = session_key_hex
            .parse()
            .map_err(|e| DeriveWsError::transport(format!("invalid session key: {e}")))?;
        Ok(Self {
            wallet_address: wallet_address.into(),
            signer,
        })
    }
}

impl Debug for DeriveWsCredentials {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct(stringify!(DeriveWsCredentials))
            .field("wallet_address", &self.wallet_address)
            .field("signer", &REDACTED)
            .finish()
    }
}

// Fixed-window rate limiter shared with the command handles so each frame is
// paced in the caller's task before it is enqueued for the feed handler.
type WsRateLimiter = DeriveRateLimiter;

const MAX_SESSION_RECOVERY_ATTEMPTS: u32 = 3;
const SUBSCRIPTION_ACCEPTED_STATUSES: &[&str] = &["ok"];
const SUBSCRIPTION_REPLAY_ACCEPTED_STATUSES: &[&str] = &["ok", "already subscribed"];
pub(super) const UNAUTHENTICATED_CONNECTION_EPOCH: u64 = u64::MAX;

/// WebSocket client for the Derive JSON-RPC stream.
///
/// Construct with [`Self::new`] (public-only) or [`Self::with_credentials`]
/// when private channels and signed actions are needed. Call [`Self::connect`]
/// before any subscribe call; [`Self::disconnect`] tears the connection down.
#[derive(Debug)]
pub struct DeriveWebSocketClient {
    url: String,
    transport_backend: TransportBackend,
    proxy_url: Option<SecretString>,
    connection_mode: Arc<ArcSwap<AtomicU8>>,
    connection_epoch: Arc<ArcSwap<AtomicU64>>,
    signal: Arc<AtomicBool>,
    auth_tracker: AuthTracker,
    authenticated_epoch: Arc<AtomicU64>,
    credentials: Option<DeriveWsCredentials>,
    next_id: Arc<AtomicU64>,
    cmd_tx: Arc<tokio::sync::RwLock<tokio::sync::mpsc::UnboundedSender<HandlerCommand>>>,
    out_rx: Option<tokio::sync::mpsc::UnboundedReceiver<DeriveWsMessage>>,
    subscriptions: Arc<DashMap<String, ()>>,
    subscription_lock: Arc<tokio::sync::Mutex<()>>,
    task_handle: TaskSlot<()>,
    send_task: Arc<SharedTaskSlot<()>>,
    shutdown_errors: Vec<String>,
    request_timeout: Duration,
    conn_id: Arc<ArcSwap<String>>,
    rate_limiter: Arc<WsRateLimiter>,
    socket_control: Option<SocketControl>,
}

#[derive(Clone, Debug)]
pub(crate) struct DeriveWebSocketShutdownHandle {
    signal: Arc<AtomicBool>,
}

impl DeriveWebSocketShutdownHandle {
    pub(crate) fn begin_shutdown(&self) {
        self.signal.store(true, Ordering::Release);
    }
}

struct DeriveWebSocketSetupGuard {
    shutdown: DeriveWebSocketShutdownHandle,
    armed: bool,
}

impl DeriveWebSocketSetupGuard {
    fn new(shutdown: DeriveWebSocketShutdownHandle) -> Self {
        Self {
            shutdown,
            armed: true,
        }
    }

    fn disarm(mut self) {
        self.armed = false;
    }
}

impl Drop for DeriveWebSocketSetupGuard {
    fn drop(&mut self) {
        if self.armed {
            self.shutdown.begin_shutdown();
        }
    }
}

/// Cloneable command handle for Derive public market data subscriptions.
#[derive(Debug, Clone)]
pub struct DeriveWebSocketSubscriptionHandle {
    cmd_tx: Arc<tokio::sync::RwLock<tokio::sync::mpsc::UnboundedSender<HandlerCommand>>>,
    subscriptions: Arc<DashMap<String, ()>>,
    subscription_lock: Arc<tokio::sync::Mutex<()>>,
    request_timeout: Duration,
    rate_limiter: Arc<WsRateLimiter>,
}

/// Cloneable handle for issuing signed `private/*` trading requests over the
/// WebSocket transport.
///
/// Carries the same `cmd_tx` the owning [`DeriveWebSocketClient`] swaps on
/// connect/reconnect, so a handle obtained at construction stays valid for the
/// client's lifetime. The handle is transport-only: it sends the pre-signed
/// body and surfaces the venue's JSON-RPC outcome. Session authorization is the
/// client's responsibility (via `public/login`).
#[derive(Debug, Clone)]
pub struct DeriveWsExecutionHandle {
    cmd_tx: Arc<tokio::sync::RwLock<tokio::sync::mpsc::UnboundedSender<HandlerCommand>>>,
    auth_tracker: AuthTracker,
    request_timeout: Duration,
    conn_id: Arc<ArcSwap<String>>,
    rate_limiter: Arc<WsRateLimiter>,
}

#[derive(Debug)]
pub(crate) struct MatchingRateLimitReservation {
    method: &'static str,
    instrument_name: Ustr,
    window: u32,
}

impl DeriveWebSocketClient {
    /// Builds a public-only client. URL falls back to the environment default
    /// when `url` is `None`.
    #[must_use]
    pub fn new(
        url: Option<String>,
        environment: DeriveEnvironment,
        transport_backend: TransportBackend,
        proxy_url: Option<String>,
    ) -> Self {
        let url = url.unwrap_or_else(|| urls::ws_url(environment).to_string());
        Self::build(
            url,
            transport_backend,
            proxy_url,
            None,
            FixedWindowLimits::websocket(None, None),
        )
    }

    /// Builds a client that will issue `public/login` on connect and replay
    /// it after each reconnect.
    ///
    /// `max_matching_requests_per_second` sets the account-wide matching
    /// allowance for order writes and `max_per_instrument_matching_requests_per_second`
    /// the independent per-instrument allowance; `None` applies the Trader-tier
    /// default of each. See [`crate::common::rate_limit`].
    #[must_use]
    pub fn with_credentials(
        url: Option<String>,
        environment: DeriveEnvironment,
        transport_backend: TransportBackend,
        proxy_url: Option<String>,
        credentials: DeriveWsCredentials,
        max_matching_requests_per_second: Option<u32>,
        max_per_instrument_matching_requests_per_second: Option<u32>,
    ) -> Self {
        let url = url.unwrap_or_else(|| urls::ws_url(environment).to_string());
        let limits = FixedWindowLimits::websocket(
            max_matching_requests_per_second,
            max_per_instrument_matching_requests_per_second,
        );
        Self::build(url, transport_backend, proxy_url, Some(credentials), limits)
    }

    fn build(
        url: String,
        transport_backend: TransportBackend,
        proxy_url: Option<String>,
        credentials: Option<DeriveWsCredentials>,
        limits: FixedWindowLimits,
    ) -> Self {
        let connection_mode = Arc::new(ArcSwap::new(Arc::new(AtomicU8::new(
            ConnectionMode::Closed as u8,
        ))));
        let connection_epoch = Arc::new(ArcSwap::new(Arc::new(AtomicU64::new(0))));

        // Placeholder channel; replaced by connect() before commands are issued.
        let (placeholder_tx, _) = tokio::sync::mpsc::unbounded_channel();

        // Matching writes draw on the account-wide and per-instrument
        // allowances; custom cancellation methods have their own windows and
        // login, subscription, and reads use the non-matching allowance.
        // Handles pace each frame in the caller's task before enqueueing, so
        // the feed handler never sleeps.
        let rate_limiter = Arc::new(FixedWindowLimiter::new(limits, MonotonicClock {}));
        Self {
            url,
            transport_backend,
            proxy_url: proxy_url.map(SecretString::from),
            connection_mode,
            connection_epoch,
            signal: Arc::new(AtomicBool::new(false)),
            auth_tracker: AuthTracker::new(),
            authenticated_epoch: Arc::new(AtomicU64::new(UNAUTHENTICATED_CONNECTION_EPOCH)),
            credentials,
            next_id: Arc::new(AtomicU64::new(1)),
            cmd_tx: Arc::new(tokio::sync::RwLock::new(placeholder_tx)),
            out_rx: None,
            subscriptions: Arc::new(DashMap::new()),
            subscription_lock: Arc::new(tokio::sync::Mutex::new(())),
            task_handle: TaskSlot::new(),
            send_task: Arc::new(SharedTaskSlot::new()),
            shutdown_errors: Vec::new(),
            request_timeout: WS_REQUEST_TIMEOUT,
            conn_id: Arc::new(ArcSwap::from_pointee(UUID4::new().to_string())),
            rate_limiter,
            socket_control: None,
        }
    }

    /// Configures socket state reporting and reconnect control.
    #[must_use]
    pub fn with_socket_control(mut self, control: SocketControl) -> Self {
        self.socket_control = Some(control);
        self
    }

    /// Returns the configured WebSocket URL.
    #[must_use]
    pub fn url(&self) -> &str {
        &self.url
    }

    /// Sets the per-operation WebSocket timeout (login, subscribe, reads, writes).
    ///
    /// Must be called before `connect()`. Defaults to `WS_REQUEST_TIMEOUT`.
    pub fn set_request_timeout(&mut self, timeout: Duration) {
        self.request_timeout = timeout;
    }

    /// Returns `true` when credentials are configured and the venue has
    /// confirmed the latest `public/login`. Cleared on reconnect.
    #[must_use]
    pub fn is_authenticated(&self) -> bool {
        self.auth_tracker.is_authenticated()
            && self.is_active()
            && self.authenticated_epoch.load(Ordering::Acquire)
                == self.connection_epoch.load().load(Ordering::Acquire)
    }

    /// Returns `true` while the underlying transport is in the active state.
    #[must_use]
    pub fn is_active(&self) -> bool {
        self.connection_mode.load().load(Ordering::Relaxed) == ConnectionMode::Active as u8
    }

    /// Establishes the WebSocket connection and spawns the I/O handler task.
    ///
    /// When credentials are configured, issues `public/login` and awaits the
    /// venue's acknowledgement before returning.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::Transport`] for handshake failures and
    /// propagates [`DeriveWsError::Auth`] / [`DeriveWsError::JsonRpc`] when
    /// the login flow fails.
    pub async fn connect(&mut self) -> Result<()> {
        // Fast path requires authenticated session when creds are configured;
        // otherwise fall through and rebuild so `Ok` always implies authenticated.
        let auth_ok = self.credentials.is_none() || self.is_authenticated();
        if self.is_active() && auth_ok && self.task_handle.is_some() {
            log::warn!("Derive WebSocket already connected");
            return Ok(());
        }

        // Tear down stale state so we don't orphan the old handler task on rebuild.
        if self.task_handle.is_some() || !self.send_task.is_empty() {
            log::debug!("Tearing down stale Derive WebSocket state before connect");
            self.teardown().await?;
        }

        self.signal.store(false, Ordering::Release);
        let setup_guard = DeriveWebSocketSetupGuard::new(self.shutdown_handle());

        self.authenticated_epoch
            .store(UNAUTHENTICATED_CONNECTION_EPOCH, Ordering::Release);

        let (message_handler, raw_rx) = channel_message_handler();
        let headers = create_standard_nautilus_headers();

        let cfg = WebSocketConfig {
            url: self.url.clone(),
            headers,
            heartbeat_interval_secs: Some(WS_HEARTBEAT_SECS),
            heartbeat_payload: None,
            connect_timeout_ms: Some(RECONNECT_TIMEOUT.as_millis() as u64),
            reconnect_delay_initial_ms: Some(RECONNECT_BASE_BACKOFF.as_millis() as u64),
            reconnect_delay_max_ms: Some(RECONNECT_MAX_BACKOFF.as_millis() as u64),
            reconnect_backoff_factor: Some(RECONNECT_BACKOFF_FACTOR),
            reconnect_jitter_ms: Some(RECONNECT_JITTER_MS),
            reconnect_max_attempts: None,
            heartbeat_timeout_secs: Some(WS_HEARTBEAT_TIMEOUT.as_secs()),
            idle_timeout_ms: None,
            backend: self.transport_backend,
            proxy_url: self
                .proxy_url
                .as_ref()
                .map(|value| value.expose_secret().to_owned()),
        };
        // Rate limiting runs caller-side via `self.rate_limiter` before frames
        // are enqueued, so the network client's own limiter is left unconfigured
        // and never sleeps inside the single feed-handler task.
        let client = WebSocketClient::builder()
            .config(cfg)
            .message_handler(message_handler)
            .maybe_state_sink(self.socket_control.as_ref().map(SocketControl::sink))
            .connect()
            .await
            .map_err(|e| DeriveWsError::transport(e.to_string()))?;

        // Register the tracker so the network controller clears
        // `is_authenticated()` on dead-socket detection, not just on the
        // later RECONNECTED sentinel.
        client.set_auth_tracker(self.auth_tracker.clone(), false);

        let (cmd_tx, cmd_rx) = tokio::sync::mpsc::unbounded_channel::<HandlerCommand>();
        let (out_tx, out_rx) = tokio::sync::mpsc::unbounded_channel::<DeriveWsMessage>();

        *self.cmd_tx.write().await = cmd_tx.clone();
        self.out_rx = Some(out_rx);
        self.conn_id.store(Arc::new(UUID4::new().to_string()));

        let connection_mode = client.connection_mode_atomic();
        let connection_epoch = client.connection_epoch_atomic();
        let reconnect_handle = client.reconnect_handle();
        self.connection_mode.store(Arc::clone(&connection_mode));
        self.connection_epoch.store(Arc::clone(&connection_epoch));
        log::debug!("Derive WebSocket connected: {}", self.url);

        if let Err(e) = cmd_tx.send(HandlerCommand::SetClient(client)) {
            return Err(DeriveWsError::transport(format!(
                "failed to send SetClient command: {e}",
            )));
        }

        let signal = Arc::clone(&self.signal);
        let auth_tracker = self.auth_tracker.clone();
        let authenticated_epoch = Arc::clone(&self.authenticated_epoch);
        let next_id = Arc::clone(&self.next_id);
        let credentials = self.credentials.clone();
        let subscriptions = Arc::clone(&self.subscriptions);
        let subscription_lock = Arc::clone(&self.subscription_lock);
        let conn_id = Arc::clone(&self.conn_id);
        let cmd_tx_for_loop = cmd_tx.clone();
        let rate_limiter = Arc::clone(&self.rate_limiter);
        let request_timeout = self.request_timeout;
        let recovery_connection_mode = Arc::clone(&connection_mode);
        let recovery_connection_epoch = Arc::clone(&connection_epoch);
        let send_task = Arc::clone(&self.send_task);

        if let Err(e) = self.task_handle.spawn(async move {
            let (recovery_tx, mut recovery_rx) = tokio::sync::mpsc::unbounded_channel::<u64>();
            let recovery_out_tx = out_tx.clone();
            let recovery_cmd_tx = cmd_tx_for_loop.clone();
            let recovery_auth_tracker = auth_tracker.clone();
            let recovery_authenticated_epoch = Arc::clone(&authenticated_epoch);
            let recovery_subscriptions = Arc::clone(&subscriptions);
            let recovery_subscription_lock = Arc::clone(&subscription_lock);
            let recovery_rate_limiter = Arc::clone(&rate_limiter);
            let recovery_credentials = credentials.clone();
            let recovery_mode = Arc::clone(&recovery_connection_mode);
            let recovery_epoch = Arc::clone(&recovery_connection_epoch);
            let mut recovery_tasks = tokio::task::JoinSet::new();

            recovery_tasks.spawn(async move {
                while let Some(mut requested_epoch) = recovery_rx.recv().await {
                    while let Ok(epoch) = recovery_rx.try_recv() {
                        requested_epoch = requested_epoch.max(epoch);
                    }

                    loop {
                        match recover_session(
                            &recovery_rate_limiter,
                            &recovery_cmd_tx,
                            &recovery_auth_tracker,
                            &recovery_authenticated_epoch,
                            &recovery_mode,
                            &recovery_epoch,
                            recovery_credentials.as_ref(),
                            &recovery_subscriptions,
                            &recovery_subscription_lock,
                            request_timeout,
                        )
                        .await
                        {
                            Ok(recovered_epoch) => {
                                while let Ok(epoch) = recovery_rx.try_recv() {
                                    requested_epoch = requested_epoch.max(epoch);
                                }

                                if requested_epoch > recovered_epoch
                                    || !session_connection_is_active(
                                        &recovery_mode,
                                        &recovery_epoch,
                                        recovered_epoch,
                                    )
                                {
                                    continue;
                                }

                                if recovery_out_tx.send(DeriveWsMessage::Reconnected).is_err() {
                                    log::debug!("Derive outer receiver dropped during recovery");
                                }
                                break;
                            }
                            Err(e) => {
                                let mut retry = false;

                                while let Ok(epoch) = recovery_rx.try_recv() {
                                    requested_epoch = requested_epoch.max(epoch);
                                    retry = true;
                                }

                                if retry {
                                    continue;
                                }
                                log::error!("Derive WebSocket session recovery failed: {e}");
                                let _ = recovery_out_tx
                                    .send(DeriveWsMessage::SessionRecoveryFailed(e.to_string()));
                                let _ = recovery_cmd_tx.send(HandlerCommand::Disconnect);
                                return;
                            }
                        }
                    }
                }
            });

            let mut handler = FeedHandler::new_with_send_task(
                signal,
                cmd_rx,
                raw_rx,
                next_id,
                auth_tracker.clone(),
                Arc::clone(&authenticated_epoch),
                send_task,
            );

            loop {
                match handler.next().await {
                    Some(DeriveWsMessage::Reconnected) => {
                        log::info!("Derive WebSocket re-establishing session after reconnect");
                        conn_id.store(Arc::new(UUID4::new().to_string()));
                        let epoch = recovery_connection_epoch.load(Ordering::Acquire);
                        if recovery_tx.send(epoch).is_err() {
                            log::error!("Derive WebSocket recovery task stopped unexpectedly");
                            let _ = cmd_tx_for_loop.send(HandlerCommand::Disconnect);
                        }
                    }
                    Some(msg) => {
                        if out_tx.send(msg).is_err() {
                            log::debug!("Derive outer receiver dropped, exiting stream loop");
                            break;
                        }
                    }
                    None => {
                        log::debug!("Derive handler task ended");
                        break;
                    }
                }
            }
        }) {
            let shutdown_result = self.teardown().await;
            return Err(DeriveWsError::transport(match shutdown_result {
                Ok(()) => format!("failed to start WebSocket handler task: {e}"),
                Err(shutdown_error) => format!(
                    "failed to start WebSocket handler task: {e}; startup rollback failed: \
                     {shutdown_error}"
                ),
            }));
        }

        if let Some(control) = &self.socket_control {
            control.register(move || reconnect_handle.request_reconnect());
        }

        if let Some(creds) = self.credentials.clone()
            && let Err(e) = login_via_handler(
                &self.rate_limiter,
                &cmd_tx,
                &self.auth_tracker,
                &self.authenticated_epoch,
                &connection_mode,
                &connection_epoch,
                &creds,
                self.request_timeout,
            )
            .await
        {
            // Without teardown, a retry connect() would short-circuit on
            // is_active() and return Ok without a valid session.
            log::warn!("Derive WebSocket login failed; tearing down transport: {e}");
            self.teardown().await?;
            return Err(e);
        }

        setup_guard.disarm();
        Ok(())
    }

    pub(crate) fn begin_shutdown(&self) {
        self.signal.store(true, Ordering::Release);
    }

    pub(crate) fn shutdown_handle(&self) -> DeriveWebSocketShutdownHandle {
        DeriveWebSocketShutdownHandle {
            signal: Arc::clone(&self.signal),
        }
    }

    /// Signals the handler to disconnect, aborts the spawn task, and resets
    /// the client's transport-related state. Shared by [`Self::disconnect`]
    /// and the login-failure branch of [`Self::connect`].
    async fn teardown(&mut self) -> Result<()> {
        self.begin_shutdown();

        if let Err(e) = self.cmd_tx.read().await.send(HandlerCommand::Disconnect) {
            log::debug!(
                "Failed to enqueue Disconnect command (handler may already be shut down): {e}",
            );
        }

        match finish_task(
            &mut self.task_handle,
            Duration::from_secs(2),
            Duration::from_secs(2),
        )
        .await
        {
            None | Some(TaskJoinOutcome::Completed(()) | TaskJoinOutcome::Aborted) => {}
            Some(TaskJoinOutcome::Failed(error)) => self
                .shutdown_errors
                .push(format!("WebSocket handler task failed: {error}")),
            Some(TaskJoinOutcome::Incomplete) => self
                .shutdown_errors
                .push("WebSocket handler task did not stop after abort".to_string()),
        }

        if self.task_handle.is_some() {
            if let Some(control) = &self.socket_control {
                control.deregister();
            }
            return self.take_shutdown_result();
        }

        match self
            .send_task
            .finish(Duration::from_secs(1), Duration::from_secs(2))
            .await
        {
            None | Some(TaskJoinOutcome::Completed(()) | TaskJoinOutcome::Aborted) => {}
            Some(TaskJoinOutcome::Failed(error)) => self
                .shutdown_errors
                .push(format!("WebSocket send worker failed: {error}")),
            Some(TaskJoinOutcome::Incomplete) => self
                .shutdown_errors
                .push("WebSocket send worker did not stop after abort".to_string()),
        }

        if !self.send_task.is_empty() {
            if let Some(control) = &self.socket_control {
                control.deregister();
            }
            return self.take_shutdown_result();
        }

        // Subscriptions are also dropped: the venue session ended with the
        // transport, so a fresh connect() must re-issue them.
        let (placeholder_tx, _) = tokio::sync::mpsc::unbounded_channel();
        *self.cmd_tx.write().await = placeholder_tx;
        self.out_rx = None;
        self.connection_mode
            .store(Arc::new(AtomicU8::new(ConnectionMode::Closed as u8)));
        self.connection_epoch.store(Arc::new(AtomicU64::new(0)));
        self.auth_tracker.invalidate();
        self.authenticated_epoch
            .store(UNAUTHENTICATED_CONNECTION_EPOCH, Ordering::Release);
        self.subscriptions.clear();
        self.signal.store(false, Ordering::Relaxed);

        if let Some(control) = &self.socket_control {
            control.deregister();
        }

        self.take_shutdown_result()
    }

    fn take_shutdown_result(&mut self) -> Result<()> {
        if self.shutdown_errors.is_empty() {
            Ok(())
        } else {
            Err(DeriveWsError::transport(
                std::mem::take(&mut self.shutdown_errors).join("; "),
            ))
        }
    }

    /// Disconnects the WebSocket connection and awaits the handler task.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::Transport`] when the disconnect command
    /// cannot be enqueued; the handler still tears down on signal.
    pub async fn disconnect(&mut self) -> Result<()> {
        log::debug!("Disconnecting Derive WebSocket");
        self.begin_shutdown();
        self.teardown().await
    }

    /// Subscribes to `ticker_slim.{instrument_name}.{interval}`. `interval` is the
    /// millisecond cadence string the venue exposes (e.g. `"100"`, `"1000"`).
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_ticker(&self, instrument_name: &str, interval: &str) -> Result<()> {
        self.subscription_handle()
            .subscribe_ticker(instrument_name, interval)
            .await
    }

    /// Unsubscribes from `ticker_slim.{instrument_name}.{interval}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_ticker(&self, instrument_name: &str, interval: &str) -> Result<()> {
        self.subscription_handle()
            .unsubscribe_ticker(instrument_name, interval)
            .await
    }

    /// Subscribes to `orderbook.{instrument_name}.{group}.{depth}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_orderbook(
        &self,
        instrument_name: &str,
        group: &str,
        depth: &str,
    ) -> Result<()> {
        self.subscription_handle()
            .subscribe_orderbook(instrument_name, group, depth)
            .await
    }

    /// Unsubscribes from `orderbook.{instrument_name}.{group}.{depth}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_orderbook(
        &self,
        instrument_name: &str,
        group: &str,
        depth: &str,
    ) -> Result<()> {
        self.subscription_handle()
            .unsubscribe_orderbook(instrument_name, group, depth)
            .await
    }

    /// Subscribes to `trades.{instrument_type}.{currency}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_trades(&self, instrument_type: &str, currency: &str) -> Result<()> {
        self.subscription_handle()
            .subscribe_trades(instrument_type, currency)
            .await
    }

    /// Unsubscribes from `trades.{instrument_type}.{currency}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_trades(&self, instrument_type: &str, currency: &str) -> Result<()> {
        self.subscription_handle()
            .unsubscribe_trades(instrument_type, currency)
            .await
    }

    /// Subscribes to a list of channel topics in a single `subscribe` frame.
    ///
    /// Used by the execution client to bulk-subscribe to the private
    /// `{subaccount_id}.orders`, `{subaccount_id}.trades`, and
    /// `{subaccount_id}.balances` channels after login.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_channels<C>(&self, channels: Vec<C>) -> Result<()>
    where
        C: Into<DeriveWsChannel>,
    {
        self.subscription_handle()
            .subscribe_channels(channels)
            .await
    }

    /// Unsubscribes from a list of channel topics in a single
    /// `unsubscribe` frame.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_channels<C>(&self, channels: Vec<C>) -> Result<()>
    where
        C: Into<DeriveWsChannel>,
    {
        self.subscription_handle()
            .unsubscribe_channels(channels)
            .await
    }

    /// Returns the next event emitted by the handler.
    pub async fn next_event(&mut self) -> Option<DeriveWsMessage> {
        if let Some(rx) = self.out_rx.as_mut() {
            rx.recv().await
        } else {
            None
        }
    }

    /// Returns the count of channels the client currently has confirmed
    /// subscriptions for.
    #[must_use]
    pub fn subscription_count(&self) -> usize {
        self.subscriptions.len()
    }

    /// Returns a cloneable handle for issuing subscription commands.
    #[must_use]
    pub fn subscription_handle(&self) -> DeriveWebSocketSubscriptionHandle {
        DeriveWebSocketSubscriptionHandle {
            cmd_tx: Arc::clone(&self.cmd_tx),
            subscriptions: Arc::clone(&self.subscriptions),
            subscription_lock: Arc::clone(&self.subscription_lock),
            request_timeout: self.request_timeout,
            rate_limiter: Arc::clone(&self.rate_limiter),
        }
    }

    /// Returns a cloneable handle for issuing signed `private/*` trading
    /// requests.
    ///
    /// The handle shares the client's command channel, so it stays valid across
    /// reconnects (the channel is swapped behind a shared lock). Obtain it once
    /// and clone it into each order-submission task.
    #[must_use]
    pub fn execution_handle(&self) -> DeriveWsExecutionHandle {
        DeriveWsExecutionHandle {
            cmd_tx: Arc::clone(&self.cmd_tx),
            auth_tracker: self.auth_tracker.clone(),
            request_timeout: self.request_timeout,
            conn_id: Arc::clone(&self.conn_id),
            rate_limiter: Arc::clone(&self.rate_limiter),
        }
    }

    /// Takes the event receiver from the client.
    ///
    /// This lets the live data client own the receive loop while subscription
    /// commands continue through [`Self::subscription_handle`].
    pub fn take_event_receiver(
        &mut self,
    ) -> Option<tokio::sync::mpsc::UnboundedReceiver<DeriveWsMessage>> {
        self.out_rx.take()
    }
}

impl Drop for DeriveWebSocketClient {
    fn drop(&mut self) {
        self.signal.store(true, Ordering::Relaxed);

        if let Some(handle) = self.task_handle.as_ref() {
            handle.abort();
        }

        if let Some(control) = &self.socket_control {
            control.deregister();
        }
    }
}

impl DeriveWebSocketSubscriptionHandle {
    pub(crate) fn has_subscription(&self, channel: &str) -> bool {
        self.subscriptions.contains_key(channel)
    }

    pub(crate) fn forget_subscription(&self, channel: &str) {
        self.subscriptions.remove(channel);
    }

    pub(crate) fn remember_subscription(&self, channel: &str) {
        self.subscriptions.insert(channel.to_string(), ());
    }

    /// Subscribes to `ticker_slim.{instrument_name}.{interval}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_ticker(&self, instrument_name: &str, interval: &str) -> Result<()> {
        let channel = ticker_channel(instrument_name, interval);
        let params = ticker_subscribe_params(instrument_name, interval);
        self.send_subscribe(channel, &params).await
    }

    /// Unsubscribes from `ticker_slim.{instrument_name}.{interval}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_ticker(&self, instrument_name: &str, interval: &str) -> Result<()> {
        let channel = ticker_channel(instrument_name, interval);
        self.send_unsubscribe(channel).await
    }

    /// Subscribes to `orderbook.{instrument_name}.{group}.{depth}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_orderbook(
        &self,
        instrument_name: &str,
        group: &str,
        depth: &str,
    ) -> Result<()> {
        let channel = orderbook_channel(instrument_name, group, depth);
        let params = orderbook_subscribe_params(instrument_name, group, depth);
        self.send_subscribe(channel, &params).await
    }

    /// Unsubscribes from `orderbook.{instrument_name}.{group}.{depth}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_orderbook(
        &self,
        instrument_name: &str,
        group: &str,
        depth: &str,
    ) -> Result<()> {
        let channel = orderbook_channel(instrument_name, group, depth);
        self.send_unsubscribe(channel).await
    }

    /// Subscribes to `trades.{instrument_type}.{currency}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_trades(&self, instrument_type: &str, currency: &str) -> Result<()> {
        let channel = trades_channel(instrument_type, currency);
        let params = trades_subscribe_params(instrument_type, currency);
        self.send_subscribe(channel, &params).await
    }

    /// Unsubscribes from `trades.{instrument_type}.{currency}`.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_trades(&self, instrument_type: &str, currency: &str) -> Result<()> {
        let channel = trades_channel(instrument_type, currency);
        self.send_unsubscribe(channel).await
    }

    /// Subscribes to multiple channel topics in a single `subscribe` frame.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn subscribe_channels<C>(&self, channels: Vec<C>) -> Result<()>
    where
        C: Into<DeriveWsChannel>,
    {
        let channels = channels.into_iter().map(Into::into).collect::<Vec<_>>();
        if channels.is_empty() {
            return Ok(());
        }
        let _guard = self.subscription_lock.lock().await;
        let params = WsSubscribeParams { channels };
        let cmd_tx = self.cmd_tx.read().await.clone();
        let result: WsSubscribeResult = send_request(
            &self.rate_limiter,
            &cmd_tx,
            methods::PUBLIC_SUBSCRIBE,
            &params,
            self.request_timeout,
        )
        .await?;

        let (confirmed, failure) =
            subscription_outcome(&params.channels, &result, SUBSCRIPTION_ACCEPTED_STATUSES);

        for channel in confirmed {
            self.subscriptions.insert(channel, ());
        }
        failure.map_or(Ok(()), Err)
    }

    /// Unsubscribes from multiple channel topics in a single
    /// `unsubscribe` frame.
    ///
    /// # Errors
    ///
    /// Propagates JSON-RPC errors raised by the venue and transport-level
    /// failures.
    pub async fn unsubscribe_channels<C>(&self, channels: Vec<C>) -> Result<()>
    where
        C: Into<DeriveWsChannel>,
    {
        let channels = channels.into_iter().map(Into::into).collect::<Vec<_>>();
        if channels.is_empty() {
            return Ok(());
        }
        let _guard = self.subscription_lock.lock().await;
        let topics = channel_topics(&channels);
        let params = WsUnsubscribeParams { channels };
        let cmd_tx = self.cmd_tx.read().await.clone();
        let _: WsUnsubscribeResult = send_request(
            &self.rate_limiter,
            &cmd_tx,
            methods::PUBLIC_UNSUBSCRIBE,
            &params,
            self.request_timeout,
        )
        .await?;

        for channel in topics {
            self.subscriptions.remove(&channel);
        }

        Ok(())
    }

    async fn send_subscribe(&self, channel: String, params: &WsSubscribeParams) -> Result<()> {
        let _guard = self.subscription_lock.lock().await;
        let cmd_tx = self.cmd_tx.read().await.clone();
        let result: WsSubscribeResult = send_request(
            &self.rate_limiter,
            &cmd_tx,
            methods::PUBLIC_SUBSCRIBE,
            params,
            self.request_timeout,
        )
        .await?;

        let (confirmed, failure) =
            subscription_outcome(&params.channels, &result, SUBSCRIPTION_ACCEPTED_STATUSES);

        if confirmed.iter().any(|topic| topic == &channel) {
            self.subscriptions.insert(channel, ());
        }
        failure.map_or(Ok(()), Err)
    }

    async fn send_unsubscribe(&self, channel: String) -> Result<()> {
        let _guard = self.subscription_lock.lock().await;
        let params = WsUnsubscribeParams {
            channels: vec![DeriveWsChannel::from(channel.clone())],
        };
        let cmd_tx = self.cmd_tx.read().await.clone();
        let _: WsUnsubscribeResult = send_request(
            &self.rate_limiter,
            &cmd_tx,
            methods::PUBLIC_UNSUBSCRIBE,
            &params,
            self.request_timeout,
        )
        .await?;

        self.subscriptions.remove(&channel);

        Ok(())
    }
}

impl DeriveWsExecutionHandle {
    /// Returns the current WebSocket connection id used by trigger orders.
    #[must_use]
    pub fn conn_id(&self) -> String {
        self.conn_id.load_full().as_ref().clone()
    }

    /// Submits a signed order via `private/order`.
    ///
    /// `params` must be the fully-built signed body from
    /// [`crate::http::query::order_to_derive_payload`]. Returns the accepted
    /// order echoed by the venue.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn submit_order(&self, params: &DeriveOrderParams) -> Result<DeriveOrder> {
        let reservation = self
            .reserve_matching_request(methods::PRIVATE_ORDER, &params.instrument_name)
            .await?;
        self.submit_order_after_rate_limit(params, reservation)
            .await
    }

    pub(crate) async fn submit_order_after_rate_limit(
        &self,
        params: &DeriveOrderParams,
        reservation: MatchingRateLimitReservation,
    ) -> Result<DeriveOrder> {
        self.ensure_authenticated(methods::PRIVATE_ORDER)?;
        debug_assert_eq!(reservation.method, methods::PRIVATE_ORDER);
        self.refresh_matching_reservation(&reservation).await;
        let cmd_tx = self.cmd_tx.read().await.clone();
        let result: DeriveOrderResult = send_request_typed_after_rate_limit(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_ORDER,
            params,
            self.request_timeout,
        )
        .await?;
        Ok(result.order)
    }

    /// Submits a signed trigger order via `private/trigger_order`.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn submit_trigger_order(
        &self,
        params: &DeriveTriggerOrderParams,
    ) -> Result<DeriveOrder> {
        let reservation = self
            .reserve_matching_request(
                methods::PRIVATE_TRIGGER_ORDER,
                &params.order.instrument_name,
            )
            .await?;
        self.submit_trigger_order_after_rate_limit(params, reservation)
            .await
    }

    pub(crate) async fn submit_trigger_order_after_rate_limit(
        &self,
        params: &DeriveTriggerOrderParams,
        reservation: MatchingRateLimitReservation,
    ) -> Result<DeriveOrder> {
        self.ensure_authenticated(methods::PRIVATE_TRIGGER_ORDER)?;
        debug_assert_eq!(reservation.method, methods::PRIVATE_TRIGGER_ORDER);
        self.refresh_matching_reservation(&reservation).await;
        let cmd_tx = self.cmd_tx.read().await.clone();
        let result: DeriveOrderResult = send_request_typed_after_rate_limit(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_TRIGGER_ORDER,
            params,
            self.request_timeout,
        )
        .await?;
        Ok(result.order)
    }

    /// Modifies a working order by cancelling it and submitting a replacement
    /// through the venue's `private/replace`.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn modify_order(&self, params: &DeriveReplaceParams) -> Result<DeriveReplaceOutcome> {
        let reservation = self
            .reserve_matching_request(methods::PRIVATE_REPLACE, &params.order.instrument_name)
            .await?;
        self.modify_order_after_rate_limit(params, reservation)
            .await
    }

    pub(crate) async fn modify_order_after_rate_limit(
        &self,
        params: &DeriveReplaceParams,
        reservation: MatchingRateLimitReservation,
    ) -> Result<DeriveReplaceOutcome> {
        self.ensure_authenticated(methods::PRIVATE_REPLACE)?;
        debug_assert_eq!(reservation.method, methods::PRIVATE_REPLACE);
        self.refresh_matching_reservation(&reservation).await;
        let cmd_tx = self.cmd_tx.read().await.clone();
        let result: DeriveReplaceResult = send_request_typed_after_rate_limit(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_REPLACE,
            params,
            self.request_timeout,
        )
        .await?;
        result
            .into_outcome(&params.order_id_to_cancel, &params.order.label)
            .map_err(|message| {
                DeriveWsError::Serde(<serde_json::Error as serde::de::Error>::custom(message))
            })
    }

    /// Cancels a single order via `private/cancel`.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn cancel_order(&self, params: &DeriveCancelParams) -> Result<()> {
        self.require_authenticated(methods::PRIVATE_CANCEL).await?;
        let cmd_tx = self.cmd_tx.read().await.clone();
        let _: DeriveEmptyResult = send_request_for_instrument(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_CANCEL,
            params,
            self.request_timeout,
            params.instrument_name,
        )
        .await?;
        Ok(())
    }

    /// Cancels every open order for one instrument via `private/cancel_by_instrument`.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn cancel_by_instrument(
        &self,
        params: &DeriveCancelByInstrumentParams,
    ) -> Result<DeriveCancelByInstrumentResult> {
        self.require_authenticated(methods::PRIVATE_CANCEL_BY_INSTRUMENT)
            .await?;
        let cmd_tx = self.cmd_tx.read().await.clone();
        send_request_typed_for_instrument(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_CANCEL_BY_INSTRUMENT,
            params,
            self.request_timeout,
            params.instrument_name,
        )
        .await
    }

    /// Cancels a single trigger order via `private/cancel_trigger_order`.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn cancel_trigger_order(
        &self,
        params: &DeriveCancelTriggerOrderParams,
    ) -> Result<DeriveOrder> {
        self.require_authenticated(methods::PRIVATE_CANCEL_TRIGGER_ORDER)
            .await?;
        let cmd_tx = self.cmd_tx.read().await.clone();
        send_request_typed(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_CANCEL_TRIGGER_ORDER,
            params,
            self.request_timeout,
        )
        .await
    }

    /// Cancels every open order with the given label via
    /// `private/cancel_by_label`.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn cancel_by_label(
        &self,
        params: &DeriveCancelByLabelParams,
    ) -> Result<DeriveCancelByLabelResult> {
        self.require_authenticated(methods::PRIVATE_CANCEL_BY_LABEL)
            .await?;
        let cmd_tx = self.cmd_tx.read().await.clone();
        send_request_typed(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_CANCEL_BY_LABEL,
            params,
            self.request_timeout,
        )
        .await
    }

    /// Returns currently untriggered trigger orders via
    /// `private/get_trigger_orders`.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn get_trigger_orders(
        &self,
        params: &DeriveGetTriggerOrdersParams,
    ) -> Result<DeriveOpenOrdersResult> {
        self.require_authenticated(methods::PRIVATE_GET_TRIGGER_ORDERS)
            .await?;
        let cmd_tx = self.cmd_tx.read().await.clone();
        send_request_typed(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_GET_TRIGGER_ORDERS,
            params,
            self.request_timeout,
        )
        .await
    }

    /// Cancels every open order on the subaccount (the venue's
    /// `private/cancel_all`), optionally scoped to an instrument.
    ///
    /// # Errors
    ///
    /// Returns [`DeriveWsError::JsonRpc`] for venue rejections and
    /// [`DeriveWsError::Transport`] / [`DeriveWsError::Timeout`] when the
    /// outcome is ambiguous.
    pub async fn cancel_all_orders(&self, params: &DeriveCancelAllParams) -> Result<()> {
        self.require_authenticated(methods::PRIVATE_CANCEL_ALL)
            .await?;
        let cmd_tx = self.cmd_tx.read().await.clone();
        let _: DeriveEmptyResult = send_request(
            &self.rate_limiter,
            &cmd_tx,
            methods::PRIVATE_CANCEL_ALL,
            params,
            self.request_timeout,
        )
        .await?;
        Ok(())
    }

    pub(crate) async fn reserve_matching_request(
        &self,
        operation: &'static str,
        instrument_name: &Ustr,
    ) -> Result<MatchingRateLimitReservation> {
        self.require_authenticated(operation).await?;
        debug_assert_eq!(rate_class_for_method(operation), RateClass::Matching);
        let window = self
            .rate_limiter
            .await_class_ready(RateClass::Matching, Some(instrument_name))
            .await;
        self.ensure_authenticated(operation)?;
        Ok(MatchingRateLimitReservation {
            method: operation,
            instrument_name: *instrument_name,
            window,
        })
    }

    // Signing between the reservation and the reserved send can cross a
    // window boundary; a rolled window re-acquires so the departure draws on
    // its own window's cells.
    async fn refresh_matching_reservation(&self, reservation: &MatchingRateLimitReservation) {
        self.rate_limiter
            .ensure_window_current(
                RateClass::Matching,
                Some(&reservation.instrument_name),
                reservation.window,
            )
            .await;
    }

    fn ensure_authenticated(&self, operation: &'static str) -> Result<()> {
        if self.auth_tracker.is_authenticated() {
            return Ok(());
        }

        Err(DeriveWsError::Authentication {
            operation: operation.to_string(),
            reason: "WebSocket session is not authenticated".to_string(),
        })
    }

    async fn require_authenticated(&self, operation: &'static str) -> Result<()> {
        if self
            .auth_tracker
            .wait_for_authenticated(self.request_timeout)
            .await
        {
            return Ok(());
        }

        Err(DeriveWsError::Authentication {
            operation: operation.to_string(),
            reason: "WebSocket session is not authenticated".to_string(),
        })
    }
}

// Awaits the venue's raw `result`, bounded by `timeout`. A dropped responder
// (handler torn down on reconnect) surfaces as `RequestCancelled`, a timeout as
// `Timeout`; both leave a state-changing write's outcome ambiguous.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum RequestRateLimit {
    /// Pace the request now, against the class buckets plus the carried
    /// instrument's per-instrument bucket when present.
    Await(Option<Ustr>),
    /// A matching reservation already consumed the cells; do not pace or
    /// consume again.
    Reserved,
}

async fn send_raw<P>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
) -> Result<Value>
where
    P: Serialize + ?Sized,
{
    send_raw_with_rate_limit(
        rate_limiter,
        cmd_tx,
        method,
        params,
        timeout,
        RequestRateLimit::Await(None),
        None,
    )
    .await
}

// Awaits the venue's raw `result` for a matching write that carries an
// instrument, pacing it against the account-wide and per-instrument buckets.
async fn send_raw_for_instrument<P>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
    instrument_name: Ustr,
) -> Result<Value>
where
    P: Serialize + ?Sized,
{
    send_raw_with_rate_limit(
        rate_limiter,
        cmd_tx,
        method,
        params,
        timeout,
        RequestRateLimit::Await(Some(instrument_name)),
        None,
    )
    .await
}

async fn send_raw_after_rate_limit<P>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
) -> Result<Value>
where
    P: Serialize + ?Sized,
{
    send_raw_with_rate_limit(
        rate_limiter,
        cmd_tx,
        method,
        params,
        timeout,
        RequestRateLimit::Reserved,
        None,
    )
    .await
}

async fn send_raw_with_rate_limit<P>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
    rate_limit: RequestRateLimit,
    connection_epoch: Option<u64>,
) -> Result<Value>
where
    P: Serialize + ?Sized,
{
    let params = SecretString::from(serde_json::to_string(params)?);

    if let RequestRateLimit::Await(instrument_name) = rate_limit {
        rate_limiter
            .await_class_ready(rate_class_for_method(method), instrument_name.as_ref())
            .await;
    }

    let (response_tx, response_rx) = tokio::sync::oneshot::channel();
    cmd_tx
        .send(HandlerCommand::Request {
            method,
            params,
            connection_epoch,
            response_tx,
        })
        .map_err(|e| DeriveWsError::transport(format!("failed to enqueue `{method}`: {e}")))?;

    // On timeout the handler's `pending` entry leaks until the next reconnect's
    // `fail_pending` drains it; the later send to the dropped receiver is a
    // no-op logged at debug.
    match tokio::time::timeout(timeout, response_rx).await {
        Ok(Ok(outcome)) => outcome,
        Ok(Err(_)) => Err(DeriveWsError::RequestCancelled {
            method: method.to_owned(),
        }),
        Err(_) => Err(DeriveWsError::Timeout {
            method: method.to_owned(),
        }),
    }
}

// Decodes the result, treating a null/absent `result` as `R::default()` (for
// login/subscribe/unsubscribe and the cancel family's `DeriveEmptyResult`).
async fn send_request<P, R>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
) -> Result<R>
where
    P: Serialize + ?Sized,
    R: Default + DeserializeOwned,
{
    let value = send_raw(rate_limiter, cmd_tx, method, params, timeout).await?;
    decode_default_result(value)
}

// Same as `send_request` for a matching write that carries an instrument, so
// the venue's per-instrument allowance is paced alongside the global one.
async fn send_request_for_instrument<P, R>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
    instrument_name: Ustr,
) -> Result<R>
where
    P: Serialize + ?Sized,
    R: Default + DeserializeOwned,
{
    let value = send_raw_for_instrument(
        rate_limiter,
        cmd_tx,
        method,
        params,
        timeout,
        instrument_name,
    )
    .await?;
    decode_default_result(value)
}

// Keep strict result decoding while reserving both matching buckets
async fn send_request_typed_for_instrument<P, R>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
    instrument_name: Ustr,
) -> Result<R>
where
    P: Serialize + ?Sized,
    R: DeserializeOwned,
{
    let value = send_raw_for_instrument(
        rate_limiter,
        cmd_tx,
        method,
        params,
        timeout,
        instrument_name,
    )
    .await?;
    Ok(serde_json::from_value(value)?)
}

fn decode_default_result<R>(value: Value) -> Result<R>
where
    R: Default + DeserializeOwned,
{
    if value.is_null() {
        Ok(R::default())
    } else {
        Ok(serde_json::from_value(value)?)
    }
}

async fn send_request_on_connection<P, R>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
    connection_epoch: u64,
) -> Result<R>
where
    P: Serialize + ?Sized,
    R: Default + DeserializeOwned,
{
    let value = send_raw_with_rate_limit(
        rate_limiter,
        cmd_tx,
        method,
        params,
        timeout,
        RequestRateLimit::Await(None),
        Some(connection_epoch),
    )
    .await?;

    decode_default_result(value)
}

// Decodes the result with no `Default` fallback, for `private/order` and
// `private/replace` whose success result is always a populated object.
async fn send_request_typed<P, R>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
) -> Result<R>
where
    P: Serialize + ?Sized,
    R: DeserializeOwned,
{
    let value = send_raw(rate_limiter, cmd_tx, method, params, timeout).await?;
    Ok(serde_json::from_value(value)?)
}

async fn send_request_typed_after_rate_limit<P, R>(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    method: &'static str,
    params: &P,
    timeout: Duration,
) -> Result<R>
where
    P: Serialize + ?Sized,
    R: DeserializeOwned,
{
    let value = send_raw_after_rate_limit(rate_limiter, cmd_tx, method, params, timeout).await?;
    Ok(serde_json::from_value(value)?)
}

fn channel_topics(channels: &[DeriveWsChannel]) -> Vec<String> {
    channels.iter().map(ToString::to_string).collect()
}

#[expect(
    clippy::too_many_arguments,
    reason = "authentication state is passed explicitly for epoch fencing"
)]
async fn login_via_handler(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    auth_tracker: &AuthTracker,
    authenticated_epoch: &AtomicU64,
    connection_mode: &AtomicU8,
    connection_epoch: &AtomicU64,
    creds: &DeriveWsCredentials,
    timeout: Duration,
) -> Result<()> {
    let _receiver = auth_tracker.begin();
    let expected_epoch = connection_epoch.load(Ordering::Acquire);

    match send_login_request(rate_limiter, cmd_tx, creds, timeout, expected_epoch).await {
        Ok(())
            if complete_session_authentication(
                auth_tracker,
                authenticated_epoch,
                connection_mode,
                connection_epoch,
                expected_epoch,
            ) =>
        {
            log::debug!("Derive WebSocket authenticated");

            Ok(())
        }
        Ok(()) => {
            let e = DeriveWsError::transport(
                "connection changed while completing WebSocket authentication",
            );
            authenticated_epoch.store(UNAUTHENTICATED_CONNECTION_EPOCH, Ordering::Release);
            auth_tracker.fail(e.to_string());
            Err(e)
        }
        Err(e) => {
            authenticated_epoch.store(UNAUTHENTICATED_CONNECTION_EPOCH, Ordering::Release);
            auth_tracker.fail(e.to_string());
            Err(e)
        }
    }
}

async fn send_login_request(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    creds: &DeriveWsCredentials,
    timeout: Duration,
    connection_epoch: u64,
) -> Result<()> {
    let login = build_ws_login(&creds.wallet_address, &creds.signer)?;
    let params = Zeroizing::new(WsLoginParams {
        wallet: login.wallet,
        timestamp: login.timestamp,
        signature: login.signature,
    });
    let result = send_request_on_connection::<_, WsLoginResult>(
        rate_limiter,
        cmd_tx,
        methods::PUBLIC_LOGIN,
        &*params,
        timeout,
        connection_epoch,
    )
    .await?;

    if matches!(result, WsLoginResult::Success { success: false }) {
        return Err(DeriveWsError::Authentication {
            operation: methods::PUBLIC_LOGIN.to_string(),
            reason: "venue returned an unsuccessful login result".to_string(),
        });
    }

    Ok(())
}

#[expect(
    clippy::too_many_arguments,
    reason = "recovery state is passed explicitly for epoch fencing"
)]
async fn recover_session(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    auth_tracker: &AuthTracker,
    authenticated_epoch: &AtomicU64,
    connection_mode: &AtomicU8,
    connection_epoch: &AtomicU64,
    creds: Option<&DeriveWsCredentials>,
    subscriptions: &DashMap<String, ()>,
    subscription_lock: &tokio::sync::Mutex<()>,
    timeout: Duration,
) -> Result<u64> {
    let _guard = subscription_lock.lock().await;
    let _receiver = creds.map(|_| auth_tracker.begin());

    for attempt in 1..=MAX_SESSION_RECOVERY_ATTEMPTS {
        let expected_epoch = wait_for_session_connection(connection_mode, connection_epoch).await?;

        let result = async {
            if !session_connection_is_active(connection_mode, connection_epoch, expected_epoch) {
                return Err(DeriveWsError::transport(
                    "connection changed before WebSocket session recovery",
                ));
            }

            if let Some(creds) = creds {
                send_login_request(rate_limiter, cmd_tx, creds, timeout, expected_epoch).await?;
            }
            let channels: Vec<String> = subscriptions
                .iter()
                .map(|entry| entry.key().clone())
                .collect();
            subscribe_via_handler(rate_limiter, cmd_tx, channels, timeout, expected_epoch).await?;

            if !session_connection_is_active(connection_mode, connection_epoch, expected_epoch) {
                return Err(DeriveWsError::transport(
                    "connection changed during WebSocket session recovery",
                ));
            }

            Ok(())
        }
        .await;

        match result {
            Ok(()) => {
                if creds.is_some()
                    && !complete_session_authentication(
                        auth_tracker,
                        authenticated_epoch,
                        connection_mode,
                        connection_epoch,
                        expected_epoch,
                    )
                {
                    continue;
                }

                if creds.is_some() {
                    log::info!("Derive WebSocket session re-authenticated");
                }

                return Ok(expected_epoch);
            }
            Err(e) if attempt < MAX_SESSION_RECOVERY_ATTEMPTS => {
                let multiplier = 1_u32 << (attempt - 1);
                let delay = RECONNECT_BASE_BACKOFF
                    .saturating_mul(multiplier)
                    .min(RECONNECT_MAX_BACKOFF);
                log::warn!(
                    "Derive WebSocket session recovery attempt {attempt}/{MAX_SESSION_RECOVERY_ATTEMPTS} failed: {e}; retrying in {delay:?}",
                );
                tokio::time::sleep(delay).await;
            }
            Err(e) => {
                authenticated_epoch.store(UNAUTHENTICATED_CONNECTION_EPOCH, Ordering::Release);

                if creds.is_some() {
                    auth_tracker.fail(e.to_string());
                }
                return Err(e);
            }
        }
    }

    let e = DeriveWsError::transport("WebSocket session changed while recovery completed");
    authenticated_epoch.store(UNAUTHENTICATED_CONNECTION_EPOCH, Ordering::Release);

    if creds.is_some() {
        auth_tracker.fail(e.to_string());
    }
    Err(e)
}

async fn wait_for_session_connection(
    connection_mode: &AtomicU8,
    connection_epoch: &AtomicU64,
) -> Result<u64> {
    loop {
        match ConnectionMode::from_atomic(connection_mode) {
            ConnectionMode::Active => return Ok(connection_epoch.load(Ordering::Acquire)),
            ConnectionMode::Reconnect => tokio::time::sleep(RECONNECT_BASE_BACKOFF).await,
            ConnectionMode::Disconnect | ConnectionMode::Closed => {
                return Err(DeriveWsError::transport(
                    "WebSocket closed during session recovery",
                ));
            }
        }
    }
}

fn complete_session_authentication(
    auth_tracker: &AuthTracker,
    authenticated_epoch: &AtomicU64,
    connection_mode: &AtomicU8,
    connection_epoch: &AtomicU64,
    expected_epoch: u64,
) -> bool {
    if !session_connection_is_active(connection_mode, connection_epoch, expected_epoch) {
        return false;
    }

    authenticated_epoch.store(expected_epoch, Ordering::Release);
    auth_tracker.succeed();

    if session_connection_is_active(connection_mode, connection_epoch, expected_epoch) {
        true
    } else {
        authenticated_epoch.store(UNAUTHENTICATED_CONNECTION_EPOCH, Ordering::Release);
        auth_tracker.invalidate();
        false
    }
}

fn session_connection_is_active(
    connection_mode: &AtomicU8,
    connection_epoch: &AtomicU64,
    expected_epoch: u64,
) -> bool {
    ConnectionMode::from_atomic(connection_mode).is_active()
        && connection_epoch.load(Ordering::Acquire) == expected_epoch
}

async fn subscribe_via_handler(
    rate_limiter: &WsRateLimiter,
    cmd_tx: &tokio::sync::mpsc::UnboundedSender<HandlerCommand>,
    channels: Vec<String>,
    timeout: Duration,
    connection_epoch: u64,
) -> Result<()> {
    if channels.is_empty() {
        return Ok(());
    }

    let params = WsSubscribeParams {
        channels: channels.into_iter().map(DeriveWsChannel::from).collect(),
    };
    let result: WsSubscribeResult = send_request_on_connection(
        rate_limiter,
        cmd_tx,
        methods::PUBLIC_SUBSCRIBE,
        &params,
        timeout,
        connection_epoch,
    )
    .await?;

    let (_, failure) = subscription_outcome(
        &params.channels,
        &result,
        SUBSCRIPTION_REPLAY_ACCEPTED_STATUSES,
    );
    failure.map_or(Ok(()), Err)
}

fn subscription_outcome(
    requested: &[DeriveWsChannel],
    result: &WsSubscribeResult,
    accepted_statuses: &[&str],
) -> (Vec<String>, Option<DeriveWsError>) {
    let mut confirmed = Vec::with_capacity(requested.len());
    let mut failures = Vec::new();

    for channel in requested {
        let topic = channel.to_string();
        match result.status.get(channel) {
            Some(status) if accepted_statuses.contains(&status.as_str()) => confirmed.push(topic),
            Some(status) => failures.push(format!("{topic}: {status}")),
            None if result.channels.contains(channel) => confirmed.push(topic),
            None => failures.push(format!("{topic}: missing channel status")),
        }
    }

    let failure = (!failures.is_empty()).then(|| DeriveWsError::Subscription {
        details: failures.join(", "),
    });
    (confirmed, failure)
}

#[cfg(test)]
mod tests {
    use rstest::rstest;

    use super::*;
    use crate::common::rate_limit::RateBucket;

    #[rstest]
    fn test_public_client_defaults_to_environment_url() {
        let client = DeriveWebSocketClient::new(
            None,
            DeriveEnvironment::Mainnet,
            TransportBackend::default(),
            None,
        );
        assert!(client.url().starts_with("wss://"));
        assert!(client.url().contains("api.lyra.finance"));
        assert!(!client.is_authenticated());
        assert!(!client.is_active());
        assert_eq!(client.subscription_count(), 0);
    }

    #[tokio::test]
    async fn test_execution_auth_barrier_waits_for_authentication() {
        let client = DeriveWebSocketClient::with_credentials(
            None,
            DeriveEnvironment::Mainnet,
            TransportBackend::default(),
            None,
            DeriveWsCredentials::new(
                "0x000000000000000000000000000000000000aaaa",
                "0x2ae8be44db8a590d20bffbe3b6872df9b569147d3bf6801a35a28281a4816bbd",
            )
            .unwrap(),
            None,
            None,
        );
        let execution = client.execution_handle();
        let auth_tracker = execution.auth_tracker.clone();
        let _receiver = auth_tracker.begin();
        let tracker_for_task = auth_tracker.clone();

        get_runtime().spawn(async move {
            tokio::time::sleep(Duration::from_millis(10)).await;
            tracker_for_task.succeed();
        });

        execution
            .require_authenticated(methods::PRIVATE_ORDER)
            .await
            .expect("barrier should wait for successful authentication");
    }

    #[tokio::test]
    async fn test_execution_auth_barrier_fails_on_terminal_auth_failure() {
        let client = DeriveWebSocketClient::with_credentials(
            None,
            DeriveEnvironment::Mainnet,
            TransportBackend::default(),
            None,
            DeriveWsCredentials::new(
                "0x000000000000000000000000000000000000aaaa",
                "0x2ae8be44db8a590d20bffbe3b6872df9b569147d3bf6801a35a28281a4816bbd",
            )
            .unwrap(),
            None,
            None,
        );
        let execution = client.execution_handle();
        let _receiver = execution.auth_tracker.begin();
        execution.auth_tracker.fail("bad signature");

        let error = execution
            .require_authenticated(methods::PRIVATE_ORDER)
            .await
            .expect_err("terminal auth failure must reject private operations");

        assert!(matches!(error, DeriveWsError::Authentication { .. }));
    }

    #[tokio::test]
    async fn test_session_recovery_waits_for_reconnecting_transport() {
        let connection_mode = Arc::new(AtomicU8::new(ConnectionMode::Reconnect as u8));
        let connection_epoch = Arc::new(AtomicU64::new(1));
        let mode_for_task = Arc::clone(&connection_mode);
        let epoch_for_task = Arc::clone(&connection_epoch);

        get_runtime().spawn(async move {
            tokio::time::sleep(Duration::from_millis(10)).await;
            epoch_for_task.store(2, Ordering::Release);
            mode_for_task.store(ConnectionMode::Active as u8, Ordering::Release);
        });

        let epoch = tokio::time::timeout(
            Duration::from_secs(1),
            wait_for_session_connection(&connection_mode, &connection_epoch),
        )
        .await
        .expect("session recovery should resume after reconnect")
        .expect("active replacement connection should be accepted");

        assert_eq!(epoch, 2);
    }

    #[rstest]
    fn test_testnet_client_routes_to_demo_url() {
        let client = DeriveWebSocketClient::new(
            None,
            DeriveEnvironment::Testnet,
            TransportBackend::default(),
            None,
        );
        assert!(client.url().contains("demo"));
    }

    #[rstest]
    fn test_credentials_constructor_parses_session_key() {
        let creds = DeriveWsCredentials::new(
            "0x000000000000000000000000000000000000aaaa",
            "0x2ae8be44db8a590d20bffbe3b6872df9b569147d3bf6801a35a28281a4816bbd",
        )
        .unwrap();
        assert!(creds.wallet_address.starts_with("0x"));
        let client = DeriveWebSocketClient::with_credentials(
            None,
            DeriveEnvironment::Testnet,
            TransportBackend::default(),
            None,
            creds,
            None,
            None,
        );
        assert!(client.url().contains("demo"));
        assert!(!client.is_authenticated());
    }

    #[rstest]
    fn test_credentials_debug_redacts_signer() {
        let creds = DeriveWsCredentials::new(
            "0xWALLET",
            "0x2ae8be44db8a590d20bffbe3b6872df9b569147d3bf6801a35a28281a4816bbd",
        )
        .unwrap();
        let debug = format!("{creds:?}");
        assert!(debug.contains("redacted"));
        assert!(debug.contains("0xWALLET"));
        assert!(!debug.contains("2ae8be44"));
    }

    #[rstest]
    fn test_credentials_constructor_rejects_invalid_session_key() {
        let err = DeriveWsCredentials::new("0xWALLET", "not-a-hex-key").unwrap_err();
        assert!(err.to_string().contains("invalid session key"));
    }

    #[rstest]
    #[tokio::test]
    async fn test_send_raw_times_out_when_no_response_arrives() {
        // Keep the receiver alive so the request enqueues, but never reply: the
        // bounded await must surface a Timeout rather than hang forever.
        let (cmd_tx, _cmd_rx) = tokio::sync::mpsc::unbounded_channel::<HandlerCommand>();
        let rate_limiter: WsRateLimiter =
            FixedWindowLimiter::new(FixedWindowLimits::websocket(None, None), MonotonicClock {});
        let err = send_raw(
            &rate_limiter,
            &cmd_tx,
            methods::PRIVATE_ORDER,
            &serde_json::json!({}),
            Duration::from_millis(50),
        )
        .await
        .expect_err("must time out");

        match err {
            DeriveWsError::Timeout { method } => assert_eq!(method, methods::PRIVATE_ORDER),
            other => panic!("expected Timeout, was {other:?}"),
        }
    }

    #[rstest]
    #[tokio::test]
    async fn test_send_request_typed_rejects_null_result() {
        // `private/order` and `private/replace` always return a populated
        // object on success; a null result is a protocol violation that must
        // surface as a serde error (classified ambiguous by the exec client).
        let (cmd_tx, mut cmd_rx) = tokio::sync::mpsc::unbounded_channel::<HandlerCommand>();
        tokio::spawn(async move {
            if let Some(HandlerCommand::Request { response_tx, .. }) = cmd_rx.recv().await {
                let _ = response_tx.send(Ok(Value::Null));
            }
        });
        let rate_limiter: WsRateLimiter =
            FixedWindowLimiter::new(FixedWindowLimits::websocket(None, None), MonotonicClock {});
        let result: Result<DeriveOrderResult> = send_request_typed(
            &rate_limiter,
            &cmd_tx,
            methods::PRIVATE_ORDER,
            &serde_json::json!({}),
            Duration::from_secs(1),
        )
        .await;
        assert!(matches!(result, Err(DeriveWsError::Serde(_))));
    }

    #[rstest]
    #[tokio::test]
    async fn test_reserved_send_does_not_wait_for_or_consume_second_quota_cell() {
        let rate_limiter: WsRateLimiter =
            FixedWindowLimiter::new(FixedWindowLimits::websocket(None, None), MonotonicClock {});

        for _ in 0..5 {
            rate_limiter
                .check_bucket(RateBucket::Matching)
                .expect("reservation consumes the matching window");
        }
        let (cmd_tx, mut cmd_rx) = tokio::sync::mpsc::unbounded_channel::<HandlerCommand>();
        tokio::spawn(async move {
            if let Some(HandlerCommand::Request { response_tx, .. }) = cmd_rx.recv().await {
                let _ = response_tx.send(Ok(serde_json::json!({"accepted": true})));
            }
        });

        let response = tokio::time::timeout(
            Duration::from_millis(100),
            send_raw_after_rate_limit(
                &rate_limiter,
                &cmd_tx,
                methods::PRIVATE_ORDER,
                &serde_json::json!({}),
                Duration::from_secs(1),
            ),
        )
        .await
        .expect("reserved send must not wait for quota")
        .expect("reserved send succeeds");

        assert_eq!(response, serde_json::json!({"accepted": true}));
        assert!(
            rate_limiter.check_bucket(RateBucket::Matching).is_err(),
            "reserved send must not consume a second cell",
        );
    }
}