fix(openai-ws): enforce passthrough turn lifecycle

backend/internal/handler/openai_gateway_handler_test.go

@@ -1875,6 +1875,212 @@ func TestOpenAIResponsesWebSocket_FailoverOnUpstreamUsageLimitEvent(t *testing.T
 	require.Equal(t, []int64{int64(9902)}, accountRepo.rateLimitedIDs)
 }
 
+func TestOpenAIResponsesWebSocket_FirstOutputTimeoutWithoutDownstreamReusesClientForOneFailover(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	firstHitCh := make(chan []byte, 1)
+	secondHitCh := make(chan []byte, 1)
+	var firstConnections atomic.Int32
+	var secondConnections atomic.Int32
+
+	firstUpstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		firstConnections.Add(1)
+		conn, err := coderws.Accept(w, r, &coderws.AcceptOptions{CompressionMode: coderws.CompressionContextTakeover})
+		if err != nil {
+			return
+		}
+		defer func() { _ = conn.CloseNow() }()
+
+		readCtx, cancelRead := context.WithTimeout(r.Context(), 3*time.Second)
+		_, payload, readErr := conn.Read(readCtx)
+		cancelRead()
+		if readErr == nil {
+			firstHitCh <- payload
+		}
+
+		select {
+		case <-r.Context().Done():
+		case <-time.After(3 * time.Second):
+		}
+	}))
+	defer firstUpstream.Close()
+
+	secondUpstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		secondConnections.Add(1)
+		conn, err := coderws.Accept(w, r, &coderws.AcceptOptions{CompressionMode: coderws.CompressionContextTakeover})
+		if err != nil {
+			return
+		}
+		defer func() { _ = conn.CloseNow() }()
+
+		readCtx, cancelRead := context.WithTimeout(r.Context(), 3*time.Second)
+		_, payload, readErr := conn.Read(readCtx)
+		cancelRead()
+		if readErr == nil {
+			secondHitCh <- payload
+		}
+
+		for _, event := range []string{
+			`{"type":"response.created","response":{"id":"resp_ws_timeout_b","model":"gpt-5.1"}}`,
+			`{"type":"response.output_text.delta","response_id":"resp_ws_timeout_b","delta":"recovered"}`,
+			`{"type":"response.completed","response":{"id":"resp_ws_timeout_b","model":"gpt-5.1","usage":{"input_tokens":1,"output_tokens":1}}}`,
+		} {
+			writeCtx, cancelWrite := context.WithTimeout(r.Context(), 3*time.Second)
+			writeErr := conn.Write(writeCtx, coderws.MessageText, []byte(event))
+			cancelWrite()
+			if writeErr != nil {
+				return
+			}
+		}
+		readCtx, cancelRead = context.WithTimeout(r.Context(), 3*time.Second)
+		_, _, _ = conn.Read(readCtx)
+		cancelRead()
+	}))
+	defer secondUpstream.Close()
+
+	groupID := int64(4212)
+	accounts := []service.Account{
+		{
+			ID:          9912,
+			Name:        "openai-ws-first-semantic-timeout",
+			Platform:    service.PlatformOpenAI,
+			Type:        service.AccountTypeAPIKey,
+			Status:      service.StatusActive,
+			Schedulable: true,
+			Concurrency: 1,
+			Priority:    1,
+			Credentials: map[string]any{"api_key": "sk-first", "base_url": firstUpstream.URL},
+			Extra: map[string]any{
+				"openai_apikey_responses_websockets_v2_enabled": true,
+				"openai_apikey_responses_websockets_v2_mode":    service.OpenAIWSIngressModePassthrough,
+			},
+		},
+		{
+			ID:          9913,
+			Name:        "openai-ws-failover-healthy",
+			Platform:    service.PlatformOpenAI,
+			Type:        service.AccountTypeAPIKey,
+			Status:      service.StatusActive,
+			Schedulable: true,
+			Concurrency: 1,
+			Priority:    2,
+			Credentials: map[string]any{"api_key": "sk-second", "base_url": secondUpstream.URL},
+			Extra: map[string]any{
+				"openai_apikey_responses_websockets_v2_enabled": true,
+				"openai_apikey_responses_websockets_v2_mode":    service.OpenAIWSIngressModePassthrough,
+			},
+		},
+	}
+
+	cfg := &config.Config{}
+	cfg.RunMode = config.RunModeSimple
+	cfg.Default.RateMultiplier = 1
+	cfg.Security.URLAllowlist.Enabled = false
+	cfg.Security.URLAllowlist.AllowInsecureHTTP = true
+	cfg.Gateway.OpenAIFirstOutputTimeoutSeconds = 1
+	cfg.Gateway.OpenAIWS.Enabled = true
+	cfg.Gateway.OpenAIWS.APIKeyEnabled = true
+	cfg.Gateway.OpenAIWS.ResponsesWebsocketsV2 = true
+	cfg.Gateway.OpenAIWS.ModeRouterV2Enabled = true
+	cfg.Gateway.OpenAIWS.DialTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.ReadTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.WriteTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.IngressInterTurnIdleTimeoutSeconds = 3
+	cfg.Gateway.MaxAccountSwitches = 3
+
+	accountRepo := &openAIWSFailoverHandlerAccountRepoStub{accounts: accounts}
+	rateLimitSvc := service.NewRateLimitService(accountRepo, nil, cfg, nil, nil)
+	billingCacheSvc := service.NewBillingCacheService(nil, nil, nil, nil, nil, nil, cfg, nil)
+	gatewaySvc := service.NewOpenAIGatewayService(
+		accountRepo, nil, nil, nil, nil, nil, nil, cfg, nil, nil,
+		service.NewBillingService(cfg, nil), rateLimitSvc, billingCacheSvc,
+		nil, &service.DeferredService{}, nil, nil, nil, nil, nil, nil, nil,
+	)
+	cache := &concurrencyCacheMock{
+		acquireUserSlotFn: func(context.Context, int64, int, string) (bool, error) { return true, nil },
+		acquireAccountSlotFn: func(context.Context, int64, int, string) (bool, error) {
+			return true, nil
+		},
+	}
+	h := &OpenAIGatewayHandler{
+		gatewayService:      gatewaySvc,
+		billingCacheService: billingCacheSvc,
+		apiKeyService:       &service.APIKeyService{},
+		concurrencyHelper:   NewConcurrencyHelper(service.NewConcurrencyService(cache), SSEPingFormatNone, time.Second),
+		maxAccountSwitches:  3,
+	}
+
+	apiKey := &service.APIKey{
+		ID:      1812,
+		GroupID: &groupID,
+		User:    &service.User{ID: 1712, Status: service.StatusActive},
+		Group:   &service.Group{ID: groupID, Platform: service.PlatformOpenAI, Status: service.StatusActive},
+	}
+	handlerDone := make(chan struct{})
+	router := gin.New()
+	router.Use(func(c *gin.Context) {
+		c.Set(string(middleware.ContextKeyAPIKey), apiKey)
+		c.Set(string(middleware.ContextKeyUser), middleware.AuthSubject{UserID: apiKey.User.ID, Concurrency: 1})
+		c.Next()
+	})
+	router.GET("/openai/v1/responses", func(c *gin.Context) {
+		h.ResponsesWebSocket(c)
+		close(handlerDone)
+	})
+	handlerServer := httptest.NewServer(router)
+	defer handlerServer.Close()
+
+	dialCtx, cancelDial := context.WithTimeout(context.Background(), 3*time.Second)
+	clientConn, _, err := coderws.Dial(
+		dialCtx,
+		"ws"+strings.TrimPrefix(handlerServer.URL, "http")+"/openai/v1/responses",
+		&coderws.DialOptions{CompressionMode: coderws.CompressionContextTakeover},
+	)
+	cancelDial()
+	require.NoError(t, err)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	writeCtx, cancelWrite := context.WithTimeout(context.Background(), 3*time.Second)
+	err = clientConn.Write(writeCtx, coderws.MessageText, []byte(`{"type":"response.create","model":"gpt-5.1","stream":false}`))
+	cancelWrite()
+	require.NoError(t, err)
+
+	var eventTypes []string
+	readCtx, cancelRead := context.WithTimeout(context.Background(), 6*time.Second)
+	for {
+		_, event, readErr := clientConn.Read(readCtx)
+		require.NoError(t, readErr)
+		eventType := gjson.GetBytes(event, "type").String()
+		eventTypes = append(eventTypes, eventType)
+		if eventType == "response.completed" {
+			require.Equal(t, "resp_ws_timeout_b", gjson.GetBytes(event, "response.id").String())
+			break
+		}
+	}
+	cancelRead()
+	require.Contains(t, eventTypes, "response.output_text.delta")
+	require.NoError(t, clientConn.Close(coderws.StatusNormalClosure, "done"))
+
+	select {
+	case <-handlerDone:
+	case <-time.After(3 * time.Second):
+		t.Fatal("websocket handler did not finish after healthy failover turn")
+	}
+	select {
+	case <-firstHitCh:
+	case <-time.After(3 * time.Second):
+		t.Fatal("first upstream did not receive replayable request")
+	}
+	select {
+	case <-secondHitCh:
+	case <-time.After(3 * time.Second):
+		t.Fatal("second upstream did not receive replayed request")
+	}
+	require.Equal(t, int32(1), firstConnections.Load())
+	require.Equal(t, int32(1), secondConnections.Load())
+	require.NotContains(t, accountRepo.rateLimitedIDs, int64(9913), "healthy failover account must not be penalized")
+}
+
 func runOpenAIResponsesWebSocketUsageLogCase(t *testing.T, tc openAIResponsesWSUsageLogCase) openAIResponsesWSUsageLogResult {
 	t.Helper()
 	gin.SetMode(gin.TestMode)

backend/internal/service/openai_ws_client_read.go

@@ -22,6 +22,29 @@ func ReadOpenAIWSClientMessage(
 	timeout time.Duration,
 	timeoutStatus coderws.StatusCode,
 	timeoutReason string,
+) (coderws.MessageType, []byte, error) {
+	return readOpenAIWSClientMessageWithTimeoutStart(
+		controlCtx,
+		conn,
+		timeout,
+		timeoutStatus,
+		timeoutReason,
+		nil,
+		nil,
+	)
+}
+
+// readOpenAIWSClientMessageWithTimeoutStart supports readers whose timeout
+// starts after a state transition, such as a completed passthrough turn. When
+// timeoutActive is nil, a positive timeout starts immediately.
+func readOpenAIWSClientMessageWithTimeoutStart(
+	controlCtx context.Context,
+	conn *coderws.Conn,
+	timeout time.Duration,
+	timeoutStatus coderws.StatusCode,
+	timeoutReason string,
+	timeoutStart <-chan struct{},
+	timeoutActive func() bool,
 ) (coderws.MessageType, []byte, error) {
 	if conn == nil {
 		return 0, nil, errors.New("openai websocket client connection is nil")
@@ -36,13 +59,33 @@ func ReadOpenAIWSClientMessage(
 		readDone <- openAIWSClientReadResult{messageType: messageType, payload: payload, err: err}
 	}()
 
-	var timeoutCh <-chan time.Time
 	var timer *time.Timer
-	if timeout > 0 {
-		timer = time.NewTimer(timeout)
+	var timeoutCh <-chan time.Time
+	startTimeout := func() {
+		if timeout <= 0 || (timeoutActive != nil && !timeoutActive()) {
+			return
+		}
+		if timer == nil {
+			timer = time.NewTimer(timeout)
+		} else {
+			if !timer.Stop() {
+				select {
+				case <-timer.C:
+				default:
+				}
+			}
+			timer.Reset(timeout)
+		}
 		timeoutCh = timer.C
-		defer timer.Stop()
 	}
+	if timeoutActive == nil || timeoutActive() {
+		startTimeout()
+	}
+	defer func() {
+		if timer != nil {
+			timer.Stop()
+		}
+	}()
 
 	closeAndJoin := func(status coderws.StatusCode, reason string, cause error) (coderws.MessageType, []byte, error) {
 		_ = conn.Close(status, reason)
@@ -51,20 +94,24 @@ func ReadOpenAIWSClientMessage(
 		return 0, nil, NewOpenAIWSClientCloseError(status, reason, cause)
 	}
 
-	select {
-	case result := <-readDone:
-		return result.messageType, result.payload, result.err
-	case <-timeoutCh:
-		return closeAndJoin(timeoutStatus, timeoutReason, context.DeadlineExceeded)
-	case <-controlCtx.Done():
-		cause := context.Cause(controlCtx)
-		if errors.Is(cause, ErrOpenAIWSIngressLeaseLost) {
-			return closeAndJoin(
-				coderws.StatusTryAgainLater,
-				"websocket ingress capacity lease lost; please reconnect",
-				cause,
-			)
+	for {
+		select {
+		case result := <-readDone:
+			return result.messageType, result.payload, result.err
+		case <-timeoutStart:
+			startTimeout()
+		case <-timeoutCh:
+			return closeAndJoin(timeoutStatus, timeoutReason, context.DeadlineExceeded)
+		case <-controlCtx.Done():
+			cause := context.Cause(controlCtx)
+			if errors.Is(cause, ErrOpenAIWSIngressLeaseLost) {
+				return closeAndJoin(
+					coderws.StatusTryAgainLater,
+					"websocket ingress capacity lease lost; please reconnect",
+					cause,
+				)
+			}
+			return closeAndJoin(coderws.StatusGoingAway, "websocket request canceled", cause)
 		}
-		return closeAndJoin(coderws.StatusGoingAway, "websocket request canceled", cause)
 	}
 }

backend/internal/service/openai_ws_v2/passthrough_relay.go

@@ -52,6 +52,7 @@ type RelayTurnResult struct {
 type RelayExit struct {
 	Stage           string
 	Err             error
+	Graceful        bool
 	WroteDownstream bool
 }
 
@@ -65,6 +66,9 @@ type RelayOptions struct {
 	OnUsageParseFailure             func(eventType string, usageRaw string)
 	OnTurnComplete                  func(turn RelayTurnResult)
 	BeforeWriteClient               func(msgType coderws.MessageType, payload []byte, wroteDownstream bool) error
+	BeforeClientWrite               func(msgType coderws.MessageType, payload []byte)
+	AfterClientWrite                func(msgType coderws.MessageType, payload []byte, writeErr error)
+	BeforeRelayCancel               func(exit RelayExit)
 	ReadClientFrame                 func(ctx context.Context, clientConn FrameConn) (coderws.MessageType, []byte, error)
 	OnTrace                         func(event RelayTraceEvent)
 	Now                             func() time.Time
@@ -226,7 +230,9 @@ func Relay(
 		options.OnUsageParseFailure,
 		options.OnTurnComplete,
 		options.BeforeWriteClient,
-		func() {
+		options.BeforeClientWrite,
+		options.AfterClientWrite,
+		func(msgType coderws.MessageType, payload []byte) {
 			if options.StartClientAfterFirstDownstream {
 				startClientReader()
 			}
@@ -241,6 +247,13 @@ func Relay(
 	go runIdleWatchdog(relayCtx, nowFn, options.IdleTimeout, &lastActivity, onTrace, exitCh)
 
 	firstExit := <-exitCh
+	// An outer ingress cancellation is a control-plane close, not a graceful
+	// upstream disconnect. Leave the client connection open here so the
+	// adapter can emit the precise lease/request close code. Internal
+	// relayCancel does not cancel ctx and therefore does not take this path.
+	if ctx.Err() != nil {
+		firstExit.graceful = false
+	}
 	emitRelayTrace(onTrace, RelayTraceEvent{
 		Stage:           "first_exit",
 		Direction:       relayDirectionFromStage(firstExit.stage),
@@ -248,6 +261,14 @@ func Relay(
 		WroteDownstream: firstExit.wroteDownstream,
 		Error:           relayErrorString(firstExit.err),
 	})
+	if options.BeforeRelayCancel != nil {
+		options.BeforeRelayCancel(RelayExit{
+			Stage:           firstExit.stage,
+			Err:             firstExit.err,
+			Graceful:        firstExit.graceful,
+			WroteDownstream: firstExit.wroteDownstream,
+		})
+	}
 	combinedWroteDownstream := firstExit.wroteDownstream
 	secondExit := relayExitSignal{graceful: true}
 	hasSecondExit := false
@@ -422,7 +443,9 @@ func runUpstreamToClient(
 	onUsageParseFailure func(eventType string, usageRaw string),
 	onTurnComplete func(turn RelayTurnResult),
 	beforeWriteClient func(msgType coderws.MessageType, payload []byte, wroteDownstream bool) error,
-	afterWriteClient func(),
+	beforeClientWrite func(msgType coderws.MessageType, payload []byte),
+	afterClientWrite func(msgType coderws.MessageType, payload []byte, writeErr error),
+	afterWriteClient func(msgType coderws.MessageType, payload []byte),
 	dropDownstreamWrites *atomic.Bool,
 	forwardedFrames *atomic.Int64,
 	droppedFrames *atomic.Int64,
@@ -498,21 +521,28 @@ func runUpstreamToClient(
 			markActivity()
 			continue
 		}
-		if err := writeClient(msgType, payload); err != nil {
+		if beforeClientWrite != nil {
+			beforeClientWrite(msgType, payload)
+		}
+		writeErr := writeClient(msgType, payload)
+		if afterClientWrite != nil {
+			afterClientWrite(msgType, payload, writeErr)
+		}
+		if writeErr != nil {
 			emitRelayTrace(onTrace, RelayTraceEvent{
 				Stage:           "write_client_failed",
 				Direction:       "upstream_to_client",
 				MessageType:     relayMessageTypeString(msgType),
 				PayloadBytes:    len(payload),
 				WroteDownstream: wroteDownstream,
-				Error:           err.Error(),
+				Error:           writeErr.Error(),
 			})
-			exitCh <- relayExitSignal{stage: "write_client", err: err, wroteDownstream: wroteDownstream}
+			exitCh <- relayExitSignal{stage: "write_client", err: writeErr, wroteDownstream: wroteDownstream}
 			return
 		}
 		wroteDownstream = true
 		if afterWriteClient != nil {
-			afterWriteClient()
+			afterWriteClient(msgType, payload)
 		}
 		if forwardedFrames != nil {
 			forwardedFrames.Add(1)

backend/internal/service/openai_ws_v2/passthrough_relay_internal_test.go

@@ -125,6 +125,8 @@ func TestRunUpstreamToClient_ErrorAndDropPaths(t *testing.T) {
 			nil,
 			nil,
 			nil,
+			nil,
+			nil,
 			drop,
 			nil,
 			nil,
@@ -156,6 +158,8 @@ func TestRunUpstreamToClient_ErrorAndDropPaths(t *testing.T) {
 			nil,
 			nil,
 			nil,
+			nil,
+			nil,
 			drop,
 			nil,
 			nil,
@@ -190,6 +194,8 @@ func TestRunUpstreamToClient_ErrorAndDropPaths(t *testing.T) {
 			nil,
 			nil,
 			nil,
+			nil,
+			nil,
 			drop,
 			nil,
 			dropped,

backend/internal/service/openai_ws_v2/passthrough_relay_test.go

@@ -31,6 +31,12 @@ type delayedReadFrameConn struct {
 	once       sync.Once
 }
 
+type readStartSpyFrameConn struct {
+	base      FrameConn
+	started   chan struct{}
+	startOnce sync.Once
+}
+
 type closeSpyFrameConn struct {
 	closeCalls atomic.Int32
 }
@@ -126,6 +132,19 @@ func (c *delayedReadFrameConn) Close() error {
 	return c.base.Close()
 }
 
+func (c *readStartSpyFrameConn) ReadFrame(ctx context.Context) (coderws.MessageType, []byte, error) {
+	c.startOnce.Do(func() { close(c.started) })
+	return c.base.ReadFrame(ctx)
+}
+
+func (c *readStartSpyFrameConn) WriteFrame(ctx context.Context, msgType coderws.MessageType, payload []byte) error {
+	return c.base.WriteFrame(ctx, msgType, payload)
+}
+
+func (c *readStartSpyFrameConn) Close() error {
+	return c.base.Close()
+}
+
 func (c *closeSpyFrameConn) ReadFrame(ctx context.Context) (coderws.MessageType, []byte, error) {
 	if ctx == nil {
 		ctx = context.Background()
@@ -661,6 +680,51 @@ func TestRelay_ContextCanceled(t *testing.T) {
 	require.NotNil(t, relayExit)
 }
 
+func TestRelay_DownstreamPreambleStartsClientReader(t *testing.T) {
+	clientBase := newPassthroughTestFrameConn(nil, false)
+	clientConn := &readStartSpyFrameConn{base: clientBase, started: make(chan struct{})}
+	upstreamConn := newPassthroughTestFrameConn(nil, false)
+	resultCh := make(chan *RelayExit, 1)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	go func() {
+		_, relayExit := Relay(
+			ctx,
+			clientConn,
+			upstreamConn,
+			[]byte(`{"type":"response.create","model":"gpt-5.1"}`),
+			RelayOptions{
+				StartClientAfterFirstDownstream: true,
+			},
+		)
+		resultCh <- relayExit
+	}()
+
+	upstreamConn.readCh <- passthroughTestFrame{
+		msgType: coderws.MessageText,
+		payload: []byte(`{"type":"response.created","response":{"id":"resp_semantic_gate"}}`),
+	}
+	require.Eventually(t, func() bool { return len(clientBase.Writes()) == 1 }, time.Second, 10*time.Millisecond)
+	select {
+	case <-clientConn.started:
+	case <-time.After(time.Second):
+		t.Fatal("response.created did not start the client reader")
+	}
+
+	upstreamConn.readCh <- passthroughTestFrame{
+		msgType: coderws.MessageText,
+		payload: []byte(`{"type":"response.completed","response":{"id":"resp_semantic_gate","usage":{"input_tokens":1,"output_tokens":1}}}`),
+	}
+	_ = upstreamConn.Close()
+	select {
+	case relayExit := <-resultCh:
+		require.Nil(t, relayExit)
+	case <-time.After(time.Second):
+		t.Fatal("relay did not finish after terminal event and upstream close")
+	}
+}
+
 func TestRelay_TraceEvents_ContainsLifecycleStages(t *testing.T) {
 	t.Parallel()
 

backend/internal/service/openai_ws_v2_passthrough_adapter.go

@@ -7,7 +7,9 @@ import (
 	"net/http"
 	"net/url"
 	"strings"
+	"sync"
 	"sync/atomic"
+	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/openai"
@@ -18,7 +20,11 @@ import (
 )
 
 type openAIWSClientFrameConn struct {
-	conn *coderws.Conn
+	conn                 *coderws.Conn
+	controlCtx           context.Context
+	interTurnIdleTimeout time.Duration
+	interTurnStarted     chan struct{}
+	waitingForNextTurn   atomic.Bool
 }
 
 // openAIWSPolicyEnforcingFrameConn wraps a client-side FrameConn and runs
@@ -193,16 +199,379 @@ func openAIWSPassthroughRequestModelFromSessionFrame(payload []byte) string {
 
 const openaiWSV2PassthroughModeFields = "ws_mode=passthrough ws_router=v2"
 
-var _ openaiwsv2.FrameConn = (*openAIWSClientFrameConn)(nil)
+var errOpenAIWSPassthroughFirstOutputTimeout = errors.New("openai websocket passthrough first output timeout")
+var errOpenAIWSPassthroughActiveTurnTimeout = errors.New("openai websocket passthrough active turn read timeout")
 
-func (c *openAIWSClientFrameConn) ReadFrame(ctx context.Context) (coderws.MessageType, []byte, error) {
-	if c == nil || c.conn == nil {
+type openAIWSPassthroughDeadlinePhase uint8
+
+const (
+	openAIWSPassthroughDeadlinePhaseFirstSemantic openAIWSPassthroughDeadlinePhase = iota + 1
+	openAIWSPassthroughDeadlinePhaseActiveRead
+)
+
+type openAIWSPassthroughFirstOutputDeadline struct {
+	timeout         time.Duration
+	startedAt       time.Time
+	requestModel    string
+	reasoningEffort string
+	phase           openAIWSPassthroughDeadlinePhase
+}
+
+type openAIWSPassthroughFirstOutputTimeoutError struct {
+	deadline openAIWSPassthroughFirstOutputDeadline
+}
+
+func (e *openAIWSPassthroughFirstOutputTimeoutError) Error() string {
+	return errOpenAIWSPassthroughFirstOutputTimeout.Error()
+}
+
+func (e *openAIWSPassthroughFirstOutputTimeoutError) Unwrap() error {
+	return errOpenAIWSPassthroughFirstOutputTimeout
+}
+
+type openAIWSPassthroughActiveTurnTimeoutError struct{}
+
+func (e *openAIWSPassthroughActiveTurnTimeoutError) Error() string {
+	return errOpenAIWSPassthroughActiveTurnTimeout.Error()
+}
+
+func (e *openAIWSPassthroughActiveTurnTimeoutError) Unwrap() error {
+	return errOpenAIWSPassthroughActiveTurnTimeout
+}
+
+type openAIWSPassthroughFirstOutputDeadlineState struct {
+	armed      bool
+	generation uint64
+	deadline   openAIWSPassthroughFirstOutputDeadline
+}
+
+type openAIWSPassthroughTurnLifecycle struct {
+	mu       sync.Mutex
+	inFlight bool
+}
+
+func newOpenAIWSPassthroughTurnLifecycle(inFlight bool) *openAIWSPassthroughTurnLifecycle {
+	return &openAIWSPassthroughTurnLifecycle{inFlight: inFlight}
+}
+
+func (l *openAIWSPassthroughTurnLifecycle) beginResponseCreate(onAccepted func()) bool {
+	if l == nil {
+		return false
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	if l.inFlight {
+		return false
+	}
+	l.inFlight = true
+	if onAccepted != nil {
+		onAccepted()
+	}
+	return true
+}
+
+func (l *openAIWSPassthroughTurnLifecycle) cancelResponseCreate() {
+	if l == nil {
+		return
+	}
+	l.mu.Lock()
+	l.inFlight = false
+	l.mu.Unlock()
+}
+
+func (l *openAIWSPassthroughTurnLifecycle) beginTerminalWrite() {
+	if l != nil {
+		l.mu.Lock()
+	}
+}
+
+func (l *openAIWSPassthroughTurnLifecycle) finishTerminalWrite(succeeded bool, onSucceeded func()) {
+	if l == nil {
+		return
+	}
+	if succeeded {
+		if onSucceeded != nil {
+			onSucceeded()
+		}
+		l.inFlight = false
+	}
+	l.mu.Unlock()
+}
+
+type openAIWSPassthroughFirstOutputFrameConn struct {
+	inner             openaiwsv2.FrameConn
+	resolveDeadline   func(payload []byte) openAIWSPassthroughFirstOutputDeadline
+	activeReadTimeout time.Duration
+
+	mu              sync.Mutex
+	state           openAIWSPassthroughFirstOutputDeadlineState
+	deadlineChanged chan struct{}
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) ReadFrame(ctx context.Context) (coderws.MessageType, []byte, error) {
+	if c == nil || c.inner == nil {
 		return coderws.MessageText, nil, errOpenAIWSConnClosed
 	}
 	if ctx == nil {
 		ctx = context.Background()
 	}
-	return c.conn.Read(ctx)
+
+	type readResult struct {
+		msgType coderws.MessageType
+		payload []byte
+		err     error
+	}
+	readCtx, cancelRead := context.WithCancel(ctx)
+	readResultCh := make(chan readResult, 1)
+	go func() {
+		msgType, payload, err := c.inner.ReadFrame(readCtx)
+		readResultCh <- readResult{msgType: msgType, payload: payload, err: err}
+	}()
+
+	var timer *time.Timer
+	var timerCh <-chan time.Time
+	resetTimer := func() {
+		state := c.deadlineState()
+		if timer != nil {
+			if !timer.Stop() {
+				select {
+				case <-timer.C:
+				default:
+				}
+			}
+		}
+		if !state.armed || state.deadline.timeout <= 0 {
+			timerCh = nil
+			return
+		}
+		remaining := time.Until(state.deadline.startedAt.Add(state.deadline.timeout))
+		if remaining < 0 {
+			remaining = 0
+		}
+		if timer == nil {
+			timer = time.NewTimer(remaining)
+		} else {
+			timer.Reset(remaining)
+		}
+		timerCh = timer.C
+	}
+	resetTimer()
+
+	defer func() {
+		cancelRead()
+		if timer != nil {
+			timer.Stop()
+		}
+	}()
+	for {
+		select {
+		case result := <-readResultCh:
+			if result.err == nil {
+				c.observeUpstreamActivity(result.msgType, result.payload)
+			}
+			return result.msgType, result.payload, result.err
+		case <-c.deadlineChanged:
+			resetTimer()
+		case <-timerCh:
+			state := c.deadlineState()
+			if !state.armed || state.deadline.timeout <= 0 || time.Now().Before(state.deadline.startedAt.Add(state.deadline.timeout)) {
+				resetTimer()
+				continue
+			}
+			if ctx.Err() != nil {
+				cancelRead()
+				<-readResultCh
+				return coderws.MessageText, nil, ctx.Err()
+			}
+			cancelRead()
+			<-readResultCh
+			if state.deadline.phase == openAIWSPassthroughDeadlinePhaseActiveRead {
+				return coderws.MessageText, nil, &openAIWSPassthroughActiveTurnTimeoutError{}
+			}
+			return coderws.MessageText, nil, &openAIWSPassthroughFirstOutputTimeoutError{deadline: state.deadline}
+		case <-ctx.Done():
+			cancelRead()
+			<-readResultCh
+			return coderws.MessageText, nil, ctx.Err()
+		}
+	}
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) WriteFrame(ctx context.Context, msgType coderws.MessageType, payload []byte) error {
+	if c == nil || c.inner == nil {
+		return errOpenAIWSConnClosed
+	}
+	generation := uint64(0)
+	if msgType == coderws.MessageText && strings.TrimSpace(gjson.GetBytes(payload, "type").String()) == "response.create" {
+		generation = c.armDeadline(payload)
+	}
+	if err := c.inner.WriteFrame(ctx, msgType, payload); err != nil {
+		c.disarmDeadline(generation)
+		return err
+	}
+	return nil
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) Close() error {
+	if c == nil || c.inner == nil {
+		return nil
+	}
+	return c.inner.Close()
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) armDeadline(payload []byte) uint64 {
+	if c == nil || c.resolveDeadline == nil {
+		return 0
+	}
+	deadline := c.resolveDeadline(payload)
+	if deadline.timeout <= 0 {
+		return 0
+	}
+	if deadline.startedAt.IsZero() {
+		deadline.startedAt = time.Now()
+	}
+	deadline.phase = openAIWSPassthroughDeadlinePhaseFirstSemantic
+	c.mu.Lock()
+	c.state.generation++
+	generation := c.state.generation
+	c.state.armed = true
+	c.state.deadline = deadline
+	c.mu.Unlock()
+	c.notifyDeadlineChanged()
+	return generation
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) observeUpstreamActivity(msgType coderws.MessageType, payload []byte) {
+	if c == nil {
+		return
+	}
+	if msgType == coderws.MessageText && openAIWSPassthroughIsTerminalOutput(payload) {
+		c.disarmDeadline(0)
+		return
+	}
+	state := c.deadlineState()
+	if state.armed && state.deadline.phase == openAIWSPassthroughDeadlinePhaseActiveRead {
+		c.armActiveReadDeadline()
+		return
+	}
+	if msgType == coderws.MessageText && openAIWSPassthroughStartsSemanticOutput(payload) {
+		c.armActiveReadDeadline()
+	}
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) armActiveReadDeadline() {
+	if c == nil {
+		return
+	}
+	if c.activeReadTimeout <= 0 {
+		c.disarmDeadline(0)
+		return
+	}
+	c.mu.Lock()
+	c.state.generation++
+	c.state.armed = true
+	c.state.deadline = openAIWSPassthroughFirstOutputDeadline{
+		timeout:   c.activeReadTimeout,
+		startedAt: time.Now(),
+		phase:     openAIWSPassthroughDeadlinePhaseActiveRead,
+	}
+	c.mu.Unlock()
+	c.notifyDeadlineChanged()
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) disarmDeadline(generation uint64) {
+	if c == nil {
+		return
+	}
+	c.mu.Lock()
+	if !c.state.armed || (generation != 0 && generation != c.state.generation) {
+		c.mu.Unlock()
+		return
+	}
+	c.state.armed = false
+	c.mu.Unlock()
+	c.notifyDeadlineChanged()
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) deadlineState() openAIWSPassthroughFirstOutputDeadlineState {
+	if c == nil {
+		return openAIWSPassthroughFirstOutputDeadlineState{}
+	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.state
+}
+
+func (c *openAIWSPassthroughFirstOutputFrameConn) notifyDeadlineChanged() {
+	if c == nil || c.deadlineChanged == nil {
+		return
+	}
+	select {
+	case c.deadlineChanged <- struct{}{}:
+	default:
+	}
+}
+
+func openAIWSPassthroughStartsSemanticOutput(payload []byte) bool {
+	eventType := strings.TrimSpace(gjson.GetBytes(payload, "type").String())
+	switch eventType {
+	case "response.completed", "response.done", "response.failed", "response.incomplete", "response.cancelled", "response.canceled":
+		return true
+	case "", "response.created", "response.in_progress", "response.output_item.added", "response.output_item.done":
+		return false
+	}
+	return strings.Contains(eventType, ".delta") ||
+		strings.HasPrefix(eventType, "response.output_text") ||
+		strings.HasPrefix(eventType, "response.output")
+}
+
+func openAIWSPassthroughIsTerminalOutput(payload []byte) bool {
+	switch strings.TrimSpace(gjson.GetBytes(payload, "type").String()) {
+	case "response.completed", "response.done", "response.failed", "response.incomplete", "response.cancelled", "response.canceled":
+		return true
+	default:
+		return false
+	}
+}
+
+var _ openaiwsv2.FrameConn = (*openAIWSClientFrameConn)(nil)
+var _ openaiwsv2.FrameConn = (*openAIWSPassthroughFirstOutputFrameConn)(nil)
+
+func (c *openAIWSClientFrameConn) ReadFrame(ctx context.Context) (coderws.MessageType, []byte, error) {
+	if c == nil || c.conn == nil {
+		return coderws.MessageText, nil, errOpenAIWSConnClosed
+	}
+	controlCtx := ctx
+	if c.controlCtx != nil {
+		controlCtx = c.controlCtx
+	}
+	msgType, payload, err := readOpenAIWSClientMessageWithTimeoutStart(
+		controlCtx,
+		c.conn,
+		c.interTurnIdleTimeout,
+		coderws.StatusNormalClosure,
+		"websocket idle timeout",
+		c.interTurnStarted,
+		func() bool { return c.waitingForNextTurn.Load() },
+	)
+	return msgType, payload, err
+}
+
+func (c *openAIWSClientFrameConn) markTurnStarted() {
+	if c != nil {
+		c.waitingForNextTurn.Store(false)
+	}
+}
+
+func (c *openAIWSClientFrameConn) markTurnCompleted() {
+	if c == nil {
+		return
+	}
+	c.waitingForNextTurn.Store(true)
+	select {
+	case c.interTurnStarted <- struct{}{}:
+	default:
+	}
 }
 
 func (c *openAIWSClientFrameConn) WriteFrame(ctx context.Context, msgType coderws.MessageType, payload []byte) error {
@@ -429,19 +798,68 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 	if !ok {
 		return errors.New("openai ws passthrough upstream connection does not support frame relay")
 	}
+	relayUpstreamFrameConn := &openAIWSPassthroughFirstOutputFrameConn{
+		inner:             upstreamFrameConn,
+		activeReadTimeout: s.openAIWSPassthroughIdleTimeout(),
+		deadlineChanged:   make(chan struct{}, 1),
+		resolveDeadline: func(payload []byte) openAIWSPassthroughFirstOutputDeadline {
+			reasoningEffort := ""
+			if current := usageMeta.reasoningEffort.Load(); current != nil {
+				reasoningEffort = *current
+			}
+			timeout := s.openAIFirstOutputTimeout(reasoningEffort)
+			if timeout <= 0 {
+				timeout = s.openAIWSPassthroughIdleTimeout()
+			}
+			model := openAIWSPassthroughRequestModelForFrame(payload)
+			if model == "" {
+				model = usageMeta.requestModelForFrame(payload)
+			}
+			if model == "" {
+				model = requestModel
+			}
+			return openAIWSPassthroughFirstOutputDeadline{
+				timeout:         timeout,
+				startedAt:       time.Now(),
+				requestModel:    model,
+				reasoningEffort: reasoningEffort,
+			}
+		},
+	}
 
 	completedTurns := atomic.Int32{}
+	turnLifecycle := newOpenAIWSPassthroughTurnLifecycle(true)
+	clientFrameConn := &openAIWSClientFrameConn{
+		conn:                 clientConn,
+		controlCtx:           ctx,
+		interTurnIdleTimeout: s.openAIWSIngressInterTurnIdleTimeout(),
+		interTurnStarted:     make(chan struct{}, 1),
+	}
 	policyClientConn := &openAIWSPolicyEnforcingFrameConn{
-		inner: &openAIWSClientFrameConn{conn: clientConn},
+		inner: clientFrameConn,
 		// 注意线程安全：filter 仅在 runClientToUpstream 这一条
 		// goroutine 中被调用（passthrough_relay.go: ReadFrame loop），
 		// capturedSessionModel 的读写都发生在该 goroutine 内，因此无需
 		// 加锁/原子化。
-		filter: func(msgType coderws.MessageType, payload []byte) ([]byte, *OpenAIFastBlockedError, error) {
+		filter: func(msgType coderws.MessageType, payload []byte) (out []byte, blocked *OpenAIFastBlockedError, filterErr error) {
 			if msgType != coderws.MessageText {
 				return payload, nil, nil
 			}
-			if strings.TrimSpace(gjson.GetBytes(payload, "type").String()) == "response.create" {
+			eventType := strings.TrimSpace(gjson.GetBytes(payload, "type").String())
+			isResponseCreate := eventType == "response.create"
+			acceptedTurn := false
+			if isResponseCreate {
+				if !turnLifecycle.beginResponseCreate(clientFrameConn.markTurnStarted) {
+					err := errors.New("overlapping response.create is not supported")
+					return payload, nil, NewOpenAIWSClientCloseError(coderws.StatusPolicyViolation, err.Error(), err)
+				}
+				defer func() {
+					if !acceptedTurn {
+						turnLifecycle.cancelResponseCreate()
+					}
+				}()
+			}
+			if isResponseCreate {
 				if account.IsOpenAIOAuth() && isOpenAIResponsesLiteWebSocketPayload(payload) {
 					litePayload, _, liteErr := normalizeOpenAIResponsesLiteToolsPayload(payload)
 					if liteErr != nil {
@@ -450,7 +868,7 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 					payload = litePayload
 				}
 			}
-			if strings.TrimSpace(gjson.GetBytes(payload, "type").String()) == "response.create" && hooks != nil && hooks.BeforeRequest != nil {
+			if isResponseCreate && hooks != nil && hooks.BeforeRequest != nil {
 				turnNo := int(completedTurns.Load()) + 1
 				if turnNo < 2 {
 					turnNo = 2
@@ -499,9 +917,9 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 			//     extractOpenAIServiceTierFromBody 返回 nil；这里有意
 			//     覆盖（Store(nil)），因为 OpenAI 上游对该帧实际不传
 			//     service_tier 时按 default 处理，billing 应如实反映。
-			if policyErr == nil && blocked == nil &&
-				strings.TrimSpace(gjson.GetBytes(payload, "type").String()) == "response.create" {
+			if policyErr == nil && blocked == nil && isResponseCreate {
 				usageMeta.updateFromResponseCreate(out, model, requestModelForThisFrame)
+				acceptedTurn = true
 			}
 			return out, blocked, policyErr
 		},
@@ -521,7 +939,7 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 	}
 	upstreamFirstMessageSent := false
 	firstWriteCtx, cancelFirstWrite := context.WithTimeout(ctx, s.openAIWSWriteTimeout())
-	firstWriteErr := upstreamFrameConn.WriteFrame(firstWriteCtx, coderws.MessageText, firstClientMessage)
+	firstWriteErr := relayUpstreamFrameConn.WriteFrame(firstWriteCtx, coderws.MessageText, firstClientMessage)
 	cancelFirstWrite()
 	if firstWriteErr != nil {
 		return wrapOpenAIWSIngressTurnError(
@@ -550,11 +968,14 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 	relayResult, relayExit := openaiwsv2.RunEntry(openaiwsv2.EntryInput{
 		Ctx:                ctx,
 		ClientConn:         policyClientConn,
-		UpstreamConn:       upstreamFrameConn,
+		UpstreamConn:       relayUpstreamFrameConn,
 		FirstClientMessage: firstClientMessage,
 		Options: openaiwsv2.RelayOptions{
-			WriteTimeout:                    s.openAIWSWriteTimeout(),
-			IdleTimeout:                     s.openAIWSPassthroughIdleTimeout(),
+			WriteTimeout: s.openAIWSWriteTimeout(),
+			// Passthrough idle is enforced only after a completed turn by
+			// clientFrameConn. The relay-wide activity watchdog would also
+			// terminate a healthy active upstream turn.
+			IdleTimeout:                     0,
 			FirstMessageType:                coderws.MessageText,
 			FirstMessageSent:                upstreamFirstMessageSent,
 			StartClientAfterFirstDownstream: true,
@@ -603,6 +1024,27 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 					hooks.AfterTurn(turnNo, turnResult, nil)
 				}
 			},
+			BeforeClientWrite: func(msgType coderws.MessageType, payload []byte) {
+				if msgType == coderws.MessageText && openAIWSPassthroughIsTerminalOutput(payload) {
+					turnLifecycle.beginTerminalWrite()
+				}
+			},
+			AfterClientWrite: func(msgType coderws.MessageType, payload []byte, writeErr error) {
+				if msgType == coderws.MessageText && openAIWSPassthroughIsTerminalOutput(payload) {
+					turnLifecycle.finishTerminalWrite(writeErr == nil, clientFrameConn.markTurnCompleted)
+				}
+			},
+			BeforeRelayCancel: func(exit openaiwsv2.RelayExit) {
+				if context.Cause(ctx) != nil {
+					return
+				}
+				status, reason, ok := openAIWSPassthroughRelayClientClose(exit, int(completedTurns.Load()))
+				if !ok {
+					return
+				}
+				_ = clientConn.Close(status, reason)
+				_ = clientConn.CloseNow()
+			},
 			BeforeWriteClient: func(msgType coderws.MessageType, payload []byte, wroteDownstream bool) error {
 				if msgType != coderws.MessageText {
 					return nil
@@ -650,6 +1092,17 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 			},
 		},
 	})
+	if cause := context.Cause(ctx); cause != nil {
+		status := coderws.StatusGoingAway
+		reason := "websocket request canceled"
+		if errors.Is(cause, ErrOpenAIWSIngressLeaseLost) {
+			status = coderws.StatusTryAgainLater
+			reason = "websocket ingress capacity lease lost; please reconnect"
+		}
+		_ = clientConn.Close(status, reason)
+		_ = clientConn.CloseNow()
+		return NewOpenAIWSClientCloseError(status, reason, cause)
+	}
 
 	result := &OpenAIForwardResult{
 		RequestID: relayResult.RequestID,
@@ -704,6 +1157,41 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 	)
 
 	relayErr := relayExit.Err
+	var firstOutputTimeoutErr *openAIWSPassthroughFirstOutputTimeoutError
+	if errors.As(relayErr, &firstOutputTimeoutErr) {
+		deadline := firstOutputTimeoutErr.deadline
+		failoverErr := s.newOpenAIFirstOutputTimeoutError(
+			ctx,
+			c,
+			account,
+			deadline.startedAt,
+			deadline.requestModel,
+			deadline.reasoningEffort,
+			deadline.timeout,
+			"websocket_first_semantic_output",
+			handshakeHeaders,
+		)
+		if turnCount == 0 && !relayExit.WroteDownstream {
+			relayErr = failoverErr
+		} else {
+			// The handler only retains the initial response.create across
+			// account attempts. Replaying it after a later-turn timeout would
+			// duplicate the first turn, so later turns end the client session.
+			relayErr = NewOpenAIWSClientCloseError(
+				coderws.StatusGoingAway,
+				"upstream produced no semantic output; please reconnect",
+				firstOutputTimeoutErr,
+			)
+		}
+	}
+	var activeTurnTimeoutErr *openAIWSPassthroughActiveTurnTimeoutError
+	if errors.As(relayErr, &activeTurnTimeoutErr) {
+		relayErr = NewOpenAIWSClientCloseError(
+			coderws.StatusGoingAway,
+			"upstream websocket read timeout; please reconnect",
+			activeTurnTimeoutErr,
+		)
+	}
 	if relayExit.Stage == "idle_timeout" {
 		relayErr = NewOpenAIWSClientCloseError(
 			coderws.StatusPolicyViolation,
@@ -722,6 +1210,28 @@ func (s *OpenAIGatewayService) proxyResponsesWebSocketV2Passthrough(
 	return turnErr
 }
 
+func openAIWSPassthroughRelayClientClose(exit openaiwsv2.RelayExit, completedTurns int) (coderws.StatusCode, string, bool) {
+	var closeErr *OpenAIWSClientCloseError
+	if errors.As(exit.Err, &closeErr) {
+		return closeErr.StatusCode(), closeErr.Reason(), true
+	}
+	var activeTurnTimeoutErr *openAIWSPassthroughActiveTurnTimeoutError
+	if errors.As(exit.Err, &activeTurnTimeoutErr) {
+		return coderws.StatusGoingAway, "upstream websocket read timeout; please reconnect", true
+	}
+	var firstOutputTimeoutErr *openAIWSPassthroughFirstOutputTimeoutError
+	if errors.As(exit.Err, &firstOutputTimeoutErr) {
+		if completedTurns > 0 || exit.WroteDownstream {
+			return coderws.StatusGoingAway, "upstream produced no semantic output; please reconnect", true
+		}
+		return 0, "", false
+	}
+	if !exit.Graceful && exit.Stage == "read_upstream" {
+		return coderws.StatusInternalError, "upstream websocket proxy failed", true
+	}
+	return 0, "", false
+}
+
 func (s *OpenAIGatewayService) mapOpenAIWSPassthroughDialError(
 	err error,
 	statusCode int,

backend/internal/service/openai_ws_v2_passthrough_lifecycle_test.go

@@ -0,0 +1,591 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	coderws "github.com/coder/websocket"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+	"github.com/tidwall/gjson"
+)
+
+type stagedPassthroughFrame struct {
+	messageType coderws.MessageType
+	payload     []byte
+}
+
+type stagedPassthroughConn struct {
+	frames    chan stagedPassthroughFrame
+	writes    chan []byte
+	closed    chan struct{}
+	closeOnce sync.Once
+}
+
+func newStagedPassthroughConn() *stagedPassthroughConn {
+	return &stagedPassthroughConn{
+		frames: make(chan stagedPassthroughFrame, 4),
+		writes: make(chan []byte, 4),
+		closed: make(chan struct{}),
+	}
+}
+
+func (c *stagedPassthroughConn) Send(payload string) {
+	c.frames <- stagedPassthroughFrame{messageType: coderws.MessageText, payload: []byte(payload)}
+}
+
+func (c *stagedPassthroughConn) WriteJSON(context.Context, any) error { return nil }
+
+func (c *stagedPassthroughConn) ReadMessage(ctx context.Context) ([]byte, error) {
+	_, payload, err := c.ReadFrame(ctx)
+	return payload, err
+}
+
+func (c *stagedPassthroughConn) Ping(context.Context) error { return nil }
+
+func (c *stagedPassthroughConn) ReadFrame(ctx context.Context) (coderws.MessageType, []byte, error) {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	select {
+	case <-ctx.Done():
+		return coderws.MessageText, nil, ctx.Err()
+	case <-c.closed:
+		return coderws.MessageText, nil, errOpenAIWSConnClosed
+	case frame := <-c.frames:
+		return frame.messageType, append([]byte(nil), frame.payload...), nil
+	}
+}
+
+func (c *stagedPassthroughConn) WriteFrame(ctx context.Context, _ coderws.MessageType, payload []byte) error {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-c.closed:
+		return errOpenAIWSConnClosed
+	default:
+	}
+	var parsed any
+	if err := json.Unmarshal(payload, &parsed); err != nil {
+		return err
+	}
+	select {
+	case c.writes <- append([]byte(nil), payload...):
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-c.closed:
+		return errOpenAIWSConnClosed
+	}
+	return nil
+}
+
+func (c *stagedPassthroughConn) Close() error {
+	c.closeOnce.Do(func() { close(c.closed) })
+	return nil
+}
+
+type stagedPassthroughDialer struct {
+	conn openAIWSClientConn
+}
+
+func (d *stagedPassthroughDialer) Dial(context.Context, string, http.Header, string) (openAIWSClientConn, int, http.Header, error) {
+	return d.conn, http.StatusSwitchingProtocols, http.Header{}, nil
+}
+
+func newPassthroughLifecycleService(cfg *config.Config, upstream *stagedPassthroughConn) *OpenAIGatewayService {
+	return &OpenAIGatewayService{
+		cfg:                       cfg,
+		httpUpstream:              &httpUpstreamRecorder{},
+		cache:                     &stubGatewayCache{},
+		openaiWSResolver:          NewOpenAIWSProtocolResolver(cfg),
+		toolCorrector:             NewCodexToolCorrector(),
+		openaiWSPassthroughDialer: &stagedPassthroughDialer{conn: upstream},
+	}
+}
+
+func passthroughLifecycleConfig() *config.Config {
+	cfg := &config.Config{}
+	cfg.Security.URLAllowlist.Enabled = false
+	cfg.Security.URLAllowlist.AllowInsecureHTTP = true
+	cfg.Gateway.OpenAIFirstOutputTimeoutSeconds = 1
+	cfg.Gateway.OpenAIWS.Enabled = true
+	cfg.Gateway.OpenAIWS.APIKeyEnabled = true
+	cfg.Gateway.OpenAIWS.ResponsesWebsocketsV2 = true
+	cfg.Gateway.OpenAIWS.ModeRouterV2Enabled = true
+	cfg.Gateway.OpenAIWS.IngressModeDefault = OpenAIWSIngressModeCtxPool
+	cfg.Gateway.OpenAIWS.IngressInterTurnIdleTimeoutSeconds = 1
+	cfg.Gateway.OpenAIWS.DialTimeoutSeconds = 3
+	cfg.Gateway.OpenAIWS.ReadTimeoutSeconds = 1
+	cfg.Gateway.OpenAIWS.WriteTimeoutSeconds = 3
+	return cfg
+}
+
+func passthroughLifecycleAccount() *Account {
+	return &Account{
+		ID:          901,
+		Name:        "passthrough-lifecycle",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeAPIKey,
+		Status:      StatusActive,
+		Schedulable: true,
+		Concurrency: 1,
+		Credentials: map[string]any{"api_key": "sk-test"},
+		Extra: map[string]any{
+			"openai_apikey_responses_websockets_v2_mode": OpenAIWSIngressModePassthrough,
+		},
+	}
+}
+
+func startPassthroughLifecycleServer(
+	t *testing.T,
+	controlCtx context.Context,
+	svc *OpenAIGatewayService,
+	account *Account,
+) (*httptest.Server, <-chan error) {
+	t.Helper()
+	serverErr := make(chan error, 1)
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		conn, err := coderws.Accept(w, r, &coderws.AcceptOptions{CompressionMode: coderws.CompressionContextTakeover})
+		if err != nil {
+			serverErr <- err
+			return
+		}
+		defer func() { _ = conn.CloseNow() }()
+
+		msgType, firstMessage, err := ReadOpenAIWSClientMessage(
+			controlCtx,
+			conn,
+			3*time.Second,
+			coderws.StatusPolicyViolation,
+			"missing first response.create message",
+		)
+		if err != nil {
+			serverErr <- err
+			return
+		}
+		if msgType != coderws.MessageText {
+			serverErr <- errors.New("first message was not text")
+			return
+		}
+
+		recorder := httptest.NewRecorder()
+		ginCtx, _ := gin.CreateTestContext(recorder)
+		req := r.Clone(controlCtx)
+		req.Header = req.Header.Clone()
+		ginCtx.Request = req
+		serverErr <- svc.ProxyResponsesWebSocketFromClient(controlCtx, ginCtx, conn, account, "sk-test", firstMessage, nil)
+	}))
+	return server, serverErr
+}
+
+func dialPassthroughLifecycleClient(t *testing.T, server *httptest.Server) *coderws.Conn {
+	t.Helper()
+	dialCtx, cancelDial := context.WithTimeout(context.Background(), 3*time.Second)
+	clientConn, _, err := coderws.Dial(dialCtx, "ws"+strings.TrimPrefix(server.URL, "http"), nil)
+	cancelDial()
+	require.NoError(t, err)
+	writeCtx, cancelWrite := context.WithTimeout(context.Background(), 3*time.Second)
+	err = clientConn.Write(writeCtx, coderws.MessageText, []byte(`{"type":"response.create","model":"gpt-5.1","stream":false}`))
+	cancelWrite()
+	require.NoError(t, err)
+	return clientConn
+}
+
+func readPassthroughLifecycleFrame(t *testing.T, clientConn *coderws.Conn, timeout time.Duration) ([]byte, error) {
+	t.Helper()
+	readCtx, cancelRead := context.WithTimeout(context.Background(), timeout)
+	_, payload, err := clientConn.Read(readCtx)
+	cancelRead()
+	return payload, err
+}
+
+func requirePassthroughUpstreamWrite(t *testing.T, upstream *stagedPassthroughConn, timeout time.Duration) []byte {
+	t.Helper()
+	select {
+	case payload := <-upstream.writes:
+		return payload
+	case <-time.After(timeout):
+		t.Fatal("passthrough request was not forwarded upstream")
+		return nil
+	}
+}
+
+func TestOpenAIWSPassthroughTurnLifecycle_SerializesTerminalCommitAndNextTurn(t *testing.T) {
+	clientFrameConn := &openAIWSClientFrameConn{interTurnStarted: make(chan struct{}, 1)}
+	clientFrameConn.markTurnCompleted()
+	lifecycle := newOpenAIWSPassthroughTurnLifecycle(true)
+	lifecycle.beginTerminalWrite()
+
+	admitted := make(chan bool, 1)
+	go func() {
+		admitted <- lifecycle.beginResponseCreate(clientFrameConn.markTurnStarted)
+	}()
+	select {
+	case <-admitted:
+		t.Fatal("next response.create was admitted before terminal commit completed")
+	case <-time.After(50 * time.Millisecond):
+	}
+
+	lifecycle.finishTerminalWrite(true, clientFrameConn.markTurnCompleted)
+	select {
+	case ok := <-admitted:
+		require.True(t, ok)
+	case <-time.After(time.Second):
+		t.Fatal("next response.create remained blocked after terminal commit")
+	}
+	require.False(t, clientFrameConn.waitingForNextTurn.Load(), "accepted next turn must win over terminal idle state")
+
+	lifecycle = newOpenAIWSPassthroughTurnLifecycle(true)
+	lifecycle.beginTerminalWrite()
+	admitted = make(chan bool, 1)
+	go func() {
+		admitted <- lifecycle.beginResponseCreate(nil)
+	}()
+	lifecycle.finishTerminalWrite(false, func() {
+		t.Error("failed terminal write must not commit idle state")
+	})
+	require.False(t, <-admitted, "failed terminal write must keep the current turn in flight")
+}
+
+func TestPassthroughLifecycle_LeaseLossSendsRetryClose(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.created","response":{"id":"resp_lease","model":"gpt-5.1"}}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(passthroughLifecycleConfig(), upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	event, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.created", gjson.GetBytes(event, "type").String())
+	cancelControl(ErrOpenAIWSIngressLeaseLost)
+
+	_, err = readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	var closeErr coderws.CloseError
+	require.ErrorAs(t, err, &closeErr)
+	require.Equal(t, coderws.StatusTryAgainLater, closeErr.Code)
+	require.Equal(t, "websocket ingress capacity lease lost; please reconnect", closeErr.Reason)
+	select {
+	case <-serverErr:
+	case <-time.After(3 * time.Second):
+		t.Fatal("passthrough lease-loss reader did not exit")
+	}
+}
+
+func TestPassthroughLifecycle_CompletedTurnStartsInterTurnIdle(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.completed","response":{"id":"resp_idle","model":"gpt-5.1","usage":{"input_tokens":1,"output_tokens":1}}}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(passthroughLifecycleConfig(), upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	event, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.completed", gjson.GetBytes(event, "type").String())
+	_, err = readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	var closeErr coderws.CloseError
+	require.ErrorAs(t, err, &closeErr)
+	require.Equal(t, coderws.StatusNormalClosure, closeErr.Code)
+	require.Equal(t, "websocket idle timeout", closeErr.Reason)
+	select {
+	case <-serverErr:
+	case <-time.After(3 * time.Second):
+		t.Fatal("passthrough idle reader did not exit")
+	}
+}
+
+func TestPassthroughLifecycle_ActiveTurnInactivityUsesReadTimeout(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.output_text.delta","response_id":"resp_active","delta":"hello"}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(passthroughLifecycleConfig(), upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	delta, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.output_text.delta", gjson.GetBytes(delta, "type").String())
+	_, err = readPassthroughLifecycleFrame(t, clientConn, 2500*time.Millisecond)
+	var websocketCloseErr coderws.CloseError
+	require.ErrorAs(t, err, &websocketCloseErr)
+	require.Equal(t, coderws.StatusGoingAway, websocketCloseErr.Code)
+	require.Equal(t, "upstream websocket read timeout; please reconnect", websocketCloseErr.Reason)
+	select {
+	case err := <-serverErr:
+		var closeErr *OpenAIWSClientCloseError
+		require.ErrorAs(t, err, &closeErr)
+		require.Equal(t, coderws.StatusGoingAway, closeErr.StatusCode())
+		require.Equal(t, "upstream websocket read timeout; please reconnect", closeErr.Reason())
+	case <-time.After(2500 * time.Millisecond):
+		t.Fatal("passthrough active turn remained unbounded after upstream activity stopped")
+	}
+}
+
+func TestPassthroughLifecycle_PreambleAllowsPromptClientCancel(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	cfg := passthroughLifecycleConfig()
+	cfg.Gateway.OpenAIFirstOutputTimeoutSeconds = 3
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.created","response":{"id":"resp_cancel","model":"gpt-5.1"}}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(cfg, upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+	require.Equal(t, "response.create", gjson.GetBytes(requirePassthroughUpstreamWrite(t, upstream, time.Second), "type").String())
+
+	created, err := readPassthroughLifecycleFrame(t, clientConn, time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.created", gjson.GetBytes(created, "type").String())
+	writeCtx, cancelWrite := context.WithTimeout(context.Background(), time.Second)
+	err = clientConn.Write(writeCtx, coderws.MessageText, []byte(`{"type":"response.cancel","response_id":"resp_cancel"}`))
+	cancelWrite()
+	require.NoError(t, err)
+	cancelFrame := requirePassthroughUpstreamWrite(t, upstream, 500*time.Millisecond)
+	require.Equal(t, "response.cancel", gjson.GetBytes(cancelFrame, "type").String())
+
+	require.NoError(t, clientConn.Close(coderws.StatusNormalClosure, "done"))
+	select {
+	case <-serverErr:
+	case <-time.After(3 * time.Second):
+		t.Fatal("passthrough cancel test did not exit")
+	}
+}
+
+func TestPassthroughLifecycle_RejectsOverlappingResponseCreate(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	cfg := passthroughLifecycleConfig()
+	cfg.Gateway.OpenAIFirstOutputTimeoutSeconds = 3
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.created","response":{"id":"resp_overlap_first","model":"gpt-5.1"}}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(cfg, upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+	require.Equal(t, "response.create", gjson.GetBytes(requirePassthroughUpstreamWrite(t, upstream, time.Second), "type").String())
+
+	created, err := readPassthroughLifecycleFrame(t, clientConn, time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.created", gjson.GetBytes(created, "type").String())
+	writeCtx, cancelWrite := context.WithTimeout(context.Background(), time.Second)
+	err = clientConn.Write(writeCtx, coderws.MessageText, []byte(`{"type":"response.create","model":"gpt-5.1"}`))
+	cancelWrite()
+	require.NoError(t, err)
+
+	_, err = readPassthroughLifecycleFrame(t, clientConn, time.Second)
+	var websocketCloseErr coderws.CloseError
+	require.ErrorAs(t, err, &websocketCloseErr)
+	require.Equal(t, coderws.StatusPolicyViolation, websocketCloseErr.Code)
+	require.Equal(t, "overlapping response.create is not supported", websocketCloseErr.Reason)
+	select {
+	case err := <-serverErr:
+		var closeErr *OpenAIWSClientCloseError
+		require.ErrorAs(t, err, &closeErr)
+		require.Equal(t, coderws.StatusPolicyViolation, closeErr.StatusCode())
+		require.Equal(t, "overlapping response.create is not supported", closeErr.Reason())
+	case <-time.After(3 * time.Second):
+		t.Fatal("overlapping response.create did not terminate passthrough")
+	}
+}
+
+func TestPassthroughLifecycle_ActiveTurnActivityRefreshesReadTimeout(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.output_text.delta","response_id":"resp_active_refresh","delta":"one"}`)
+	go func() {
+		for _, event := range []string{
+			`{"type":"response.output_text.delta","response_id":"resp_active_refresh","delta":"two"}`,
+			`{"type":"response.output_text.delta","response_id":"resp_active_refresh","delta":"three"}`,
+			`{"type":"response.completed","response":{"id":"resp_active_refresh","model":"gpt-5.1","usage":{"input_tokens":1,"output_tokens":3}}}`,
+		} {
+			timer := time.NewTimer(600 * time.Millisecond)
+			<-timer.C
+			timer.Stop()
+			upstream.Send(event)
+		}
+	}()
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(passthroughLifecycleConfig(), upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	for _, wantType := range []string{
+		"response.output_text.delta",
+		"response.output_text.delta",
+		"response.output_text.delta",
+		"response.completed",
+	} {
+		frame, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+		require.NoError(t, err)
+		require.Equal(t, wantType, gjson.GetBytes(frame, "type").String())
+	}
+	require.NoError(t, clientConn.Close(coderws.StatusNormalClosure, "done"))
+	select {
+	case <-serverErr:
+	case <-time.After(3 * time.Second):
+		t.Fatal("passthrough active-turn refresh test did not exit")
+	}
+}
+
+func TestPassthroughLifecycle_TerminalSwitchesToInterTurnIdleTimeout(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	cfg := passthroughLifecycleConfig()
+	cfg.Gateway.OpenAIWS.ReadTimeoutSeconds = 1
+	cfg.Gateway.OpenAIWS.IngressInterTurnIdleTimeoutSeconds = 2
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.completed","response":{"id":"resp_idle_first","model":"gpt-5.1","usage":{"input_tokens":1,"output_tokens":1}}}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(cfg, upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+	require.Equal(t, "response.create", gjson.GetBytes(requirePassthroughUpstreamWrite(t, upstream, 3*time.Second), "type").String())
+
+	completed, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "resp_idle_first", gjson.GetBytes(completed, "response.id").String())
+	time.Sleep(1300 * time.Millisecond)
+	writeCtx, cancelWrite := context.WithTimeout(context.Background(), 3*time.Second)
+	err = clientConn.Write(writeCtx, coderws.MessageText, []byte(`{"type":"response.create","model":"gpt-5.1","previous_response_id":"resp_idle_first"}`))
+	cancelWrite()
+	require.NoError(t, err)
+	require.Equal(t, "response.create", gjson.GetBytes(requirePassthroughUpstreamWrite(t, upstream, 3*time.Second), "type").String())
+	upstream.Send(`{"type":"response.completed","response":{"id":"resp_idle_second","model":"gpt-5.1","usage":{"input_tokens":1,"output_tokens":1}}}`)
+	completed, err = readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "resp_idle_second", gjson.GetBytes(completed, "response.id").String())
+	_, err = readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	var websocketCloseErr coderws.CloseError
+	require.ErrorAs(t, err, &websocketCloseErr)
+	require.Equal(t, coderws.StatusNormalClosure, websocketCloseErr.Code)
+	require.Equal(t, "websocket idle timeout", websocketCloseErr.Reason)
+
+	select {
+	case err := <-serverErr:
+		var closeErr *OpenAIWSClientCloseError
+		require.ErrorAs(t, err, &closeErr)
+		require.Equal(t, coderws.StatusNormalClosure, closeErr.StatusCode())
+		require.Equal(t, "websocket idle timeout", closeErr.Reason())
+	case <-time.After(3 * time.Second):
+		t.Fatal("passthrough terminal turn did not use inter-turn idle timeout")
+	}
+}
+
+func TestPassthroughLifecycle_FirstOutputTimeoutRemainsBounded(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	upstream := newStagedPassthroughConn()
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(passthroughLifecycleConfig(), upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	select {
+	case err := <-serverErr:
+		var failoverErr *UpstreamFailoverError
+		require.ErrorAs(t, err, &failoverErr)
+		require.Equal(t, http.StatusGatewayTimeout, failoverErr.StatusCode)
+		require.Contains(t, string(failoverErr.ResponseBody), "first_output_timeout")
+	case <-time.After(2500 * time.Millisecond):
+		t.Fatal("passthrough first output was left unbounded")
+	}
+}
+
+func TestPassthroughLifecycle_ResponseCreatedTimeoutClosesWithoutFailover(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.created","response":{"id":"resp_preamble","model":"gpt-5.1"}}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(passthroughLifecycleConfig(), upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	created, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.created", gjson.GetBytes(created, "type").String())
+	_, err = readPassthroughLifecycleFrame(t, clientConn, 2500*time.Millisecond)
+	var websocketCloseErr coderws.CloseError
+	require.ErrorAs(t, err, &websocketCloseErr)
+	require.Equal(t, coderws.StatusGoingAway, websocketCloseErr.Code)
+	require.Equal(t, "upstream produced no semantic output; please reconnect", websocketCloseErr.Reason)
+	select {
+	case err := <-serverErr:
+		var failoverErr *UpstreamFailoverError
+		require.NotErrorAs(t, err, &failoverErr)
+		var closeErr *OpenAIWSClientCloseError
+		require.ErrorAs(t, err, &closeErr)
+		require.Equal(t, coderws.StatusGoingAway, closeErr.StatusCode())
+		require.Equal(t, "upstream produced no semantic output; please reconnect", closeErr.Reason())
+	case <-time.After(2500 * time.Millisecond):
+		t.Fatal("response.created timeout did not close the passthrough connection")
+	}
+}
+
+func TestPassthroughLifecycle_SecondTurnTimeoutIsNotFailoverSafe(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	controlCtx, cancelControl := context.WithCancelCause(context.Background())
+	defer cancelControl(context.Canceled)
+	upstream := newStagedPassthroughConn()
+	upstream.Send(`{"type":"response.completed","response":{"id":"resp_first","model":"gpt-5.1","usage":{"input_tokens":1,"output_tokens":1}}}`)
+	server, serverErr := startPassthroughLifecycleServer(t, controlCtx, newPassthroughLifecycleService(passthroughLifecycleConfig(), upstream), passthroughLifecycleAccount())
+	defer server.Close()
+	clientConn := dialPassthroughLifecycleClient(t, server)
+	defer func() { _ = clientConn.CloseNow() }()
+
+	completed, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.completed", gjson.GetBytes(completed, "type").String())
+	writeCtx, cancelWrite := context.WithTimeout(context.Background(), 3*time.Second)
+	err = clientConn.Write(writeCtx, coderws.MessageText, []byte(`{"type":"response.create","model":"gpt-5.1","previous_response_id":"resp_first"}`))
+	cancelWrite()
+	require.NoError(t, err)
+	upstream.Send(`{"type":"response.created","response":{"id":"resp_second","model":"gpt-5.1"}}`)
+
+	created, err := readPassthroughLifecycleFrame(t, clientConn, 3*time.Second)
+	require.NoError(t, err)
+	require.Equal(t, "response.created", gjson.GetBytes(created, "type").String())
+	_, err = readPassthroughLifecycleFrame(t, clientConn, 2500*time.Millisecond)
+	var websocketCloseErr coderws.CloseError
+	require.ErrorAs(t, err, &websocketCloseErr)
+	require.Equal(t, coderws.StatusGoingAway, websocketCloseErr.Code)
+	require.Equal(t, "upstream produced no semantic output; please reconnect", websocketCloseErr.Reason)
+	select {
+	case err := <-serverErr:
+		var failoverErr *UpstreamFailoverError
+		require.NotErrorAs(t, err, &failoverErr, "handler must not replay the initial request on another account for a later-turn timeout")
+		var closeErr *OpenAIWSClientCloseError
+		require.ErrorAs(t, err, &closeErr)
+		require.Equal(t, coderws.StatusGoingAway, closeErr.StatusCode())
+	case <-time.After(2500 * time.Millisecond):
+		t.Fatal("second turn first semantic output was left unbounded")
+	}
+}