diff --git a/enterprise/coderd/x/chatd/chatd_test.go b/enterprise/coderd/x/chatd/chatd_test.go
index b959d7002f..a59a61780b 100644
--- a/enterprise/coderd/x/chatd/chatd_test.go
+++ b/enterprise/coderd/x/chatd/chatd_test.go
@@ -1471,6 +1471,14 @@ func TestSubscribeRelayDrainWithinGraceLeavesBufferRetained(t *testing.T) {
 		require.NoError(t, worker.Close())
 	})
 
+	// Use a mock clock for the subscriber so the relay drain
+	// timer never fires until we explicitly advance it. This
+	// removes the nondeterministic 200ms race between the drain
+	// timer and the multi-hop snapshot forwarding pipeline.
+	subscriberClock := quartz.NewMock(t)
+	trapDrain := subscriberClock.Trap().NewTimer("drain")
+	defer trapDrain.Close()
+
 	// Subscriber dials through to the worker. On cancel the relay
 	// drain fires well inside the worker's 5s grace, exercising the
 	// cleanupStreamIfIdle early-return path.
@@ -1490,7 +1498,7 @@ func TestSubscribeRelayDrainWithinGraceLeavesBufferRetained(t *testing.T) {
 			return nil, nil, nil, xerrors.New("worker subscribe failed")
 		}
 		return snapshot, relayEvents, cancel, nil
-	}, nil)
+	}, subscriberClock)
 
 	ctx := testutil.Context(t, testutil.WaitLong)
 	user, org, model := seedChatDependencies(ctx, t, db)
@@ -1514,9 +1522,13 @@ func TestSubscribeRelayDrainWithinGraceLeavesBufferRetained(t *testing.T) {
 	// the assistant message and at least one message_part so we know
 	// processChat's defer has flipped buffering=false and populated
 	// bufferRetainedAt before the subscriber detaches.
+	//
+	// Each Eventually gets its own context so one slow assertion
+	// cannot starve subsequent ones of their deadline.
 	var committedAssistantMsgs int
 	var messagePartsSeen int
-	testutil.Eventually(ctx, t, func(context.Context) bool {
+	evCtx1 := testutil.Context(t, testutil.WaitLong)
+	testutil.Eventually(evCtx1, t, func(context.Context) bool {
 		select {
 		case event := <-events:
 			switch event.Type {
@@ -1533,7 +1545,15 @@ func TestSubscribeRelayDrainWithinGraceLeavesBufferRetained(t *testing.T) {
 		}
 	}, testutil.IntervalFast)
 
-	testutil.Eventually(ctx, t, func(ctx context.Context) bool {
+	// Wait for the drain timer to be armed by the relay manager,
+	// then release and advance the subscriber clock past the drain
+	// timeout. This deterministically fires the drain without
+	// relying on wall-clock timing.
+	trapDrain.MustWait(ctx).MustRelease(ctx)
+	subscriberClock.Advance(200 * time.Millisecond).MustWait(ctx)
+
+	evCtx2 := testutil.Context(t, testutil.WaitLong)
+	testutil.Eventually(evCtx2, t, func(ctx context.Context) bool {
 		fromDB, dbErr := db.GetChatByID(ctx, chat.ID)
 		if dbErr != nil {
 			return false
@@ -1550,7 +1570,8 @@ func TestSubscribeRelayDrainWithinGraceLeavesBufferRetained(t *testing.T) {
 	// worker observes the teardown. The retry itself re-enters
 	// cleanupStreamIfIdle via its own cancel defer but still
 	// early-returns because grace is still open.
-	testutil.Eventually(ctx, t, func(ctx context.Context) bool {
+	evCtx3 := testutil.Context(t, testutil.WaitLong)
+	testutil.Eventually(evCtx3, t, func(ctx context.Context) bool {
 		snap, _, snapCancel, ok := worker.Subscribe(ctx, chat.ID, nil, math.MaxInt64)
 		if !ok {
 			return false