diff --git a/test/utils/ktesting/internal/synctestinit/synctestinit_test.go b/test/utils/ktesting/internal/synctestinit/synctestinit_test.go
new file mode 100644
index 00000000000..2920313f1c9
--- /dev/null
+++ b/test/utils/ktesting/internal/synctestinit/synctestinit_test.go
@@ -0,0 +1,43 @@
+/*
+Copyright The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+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.
+*/
+
+package ktesting_test
+
+import (
+	"testing"
+	"testing/synctest"
+
+	"k8s.io/kubernetes/test/utils/ktesting"
+)
+
+// TestSyncTestInit matches the corresponding test in the main package. It
+// exists here as the only test inside this package because signal.Notify fails
+// inside a synctest bubble when called for the first time in a process and we
+// want to enforce that situation.
+func TestSyncTestInit(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		// This must work inside a synctest bubble, despite Deadline panicking there.
+		// We then don't have a deadline.
+		tCtx := ktesting.Init(t)
+		deadline, ok := tCtx.Deadline()
+		if ok {
+			tCtx.Errorf("Expected no deadline, got %s", deadline)
+		}
+		if !tCtx.IsSyncTest() {
+			tCtx.Errorf("Expected to run as synctest")
+		}
+	})
+}
diff --git a/test/utils/ktesting/signals.go b/test/utils/ktesting/signals.go
index 4edef18bd96..3a0a759ead5 100644
--- a/test/utils/ktesting/signals.go
+++ b/test/utils/ktesting/signals.go
@@ -77,7 +77,14 @@ var _ ginkgoReporter = &progressReporter{}
 // USR1 signal, similar to the corresponding Ginkgo feature.
 //
 // This support is active until the last test terminates.
-func (p *progressReporter) init(tb TB) context.Context {
+//
+// Inside a bubble, signal.Notify fails with "select on synctest channel from
+// outside bubble" if (and only if) it gets called for the first time, so we
+// have to avoid setting up signal handling to be on the safe side.
+func (p *progressReporter) init(tb TB, isSyncTest bool) context.Context {
+	if isSyncTest {
+		return context.Background()
+	}
 	if _, ok := tb.(testing.TB); !ok {
 		// Not in a Go unit test.
 		return context.Background()
diff --git a/test/utils/ktesting/tcontext.go b/test/utils/ktesting/tcontext.go
index c9002527190..43d62a506f4 100644
--- a/test/utils/ktesting/tcontext.go
+++ b/test/utils/ktesting/tcontext.go
@@ -117,8 +117,24 @@ type ContextTB interface {
 // Ginkgo create a fresh context for cleanup code.
 //
 // Can be called more than once per test to get different contexts with
-// independent cancellation. The default behavior describe above can be
+// independent cancellation. The default behavior described above can be
 // modified via optional functional options defined in [initoption].
+//
+// Can be called inside a synctest bubble. Signal handling (cleaning up on
+// SIGINT, progress reporting on SIGUSR1) then does not get initialized because
+// code running inside a bubble should not depend on outside input. Progress
+// reporting still works when some parent test already initialized it.
+// Therefore the recommended pattern is to initialize ktesting first, then
+// create the synctest bubble:
+//
+//	func TestSomething(t *testing.T) { ktesting.Init(t).SyncTest("", testSomething) }
+//	func testSomething(tCtx ktesting.TContext) { ... }
+//
+// This pattern also has the advantage that the test code cannot accidentally
+// use the testing.T instance directly. The same works for normal tests:
+//
+//	func TestSomething(t *testing.T) { testSomething(ktesting.Init(t)) }
+//	func testSomething(tCtx ktesting.TContext) { ... }
 func Init(tb TB, opts ...InitOption) TContext {
 	tb.Helper()
 
@@ -130,13 +146,31 @@ func Init(tb TB, opts ...InitOption) TContext {
 	}
 
 	// We don't need a Deadline implementation, testing.B doesn't have it.
-	// But if we have one, we'll use it to set a timeout shortly before
-	// the deadline. This needs to come before we wrap tb.
-	deadlineTB, deadlineOK := tb.(interface {
+	// But if we have one, we use it to determine the deadline and
+	// set a timeout shortly before it.
+	//
+	// This also allows us to detect a synctest bubble.
+	isSyncTest := false
+	var deadline *time.Time
+	if deadlineTB, deadlineOK := tb.(interface {
 		Deadline() (time.Time, bool)
-	})
+	}); deadlineOK {
+		func() {
+			defer func() {
+				// Calling testing.T.Deadline panics inside a synctest bubble.
+				// There's no API to detect that in advance, so here we react
+				// by catching the panic.
+				if r := recover(); r != nil {
+					isSyncTest = true
+				}
+			}()
+			if d, ok := deadlineTB.Deadline(); ok {
+				deadline = &d
+			}
+		}()
+	}
 
-	ctx := defaultProgressReporter.init(tb)
+	ctx := defaultProgressReporter.init(tb, isSyncTest)
 	var header func() string
 	if c.PerTestOutput {
 		logger := newLogger(tb, c.BufferLogs)
@@ -145,16 +179,15 @@ func Init(tb TB, opts ...InitOption) TContext {
 	}
 
 	var cancelTimeout func(cause string)
-	if deadlineOK {
-		if deadline, ok := deadlineTB.Deadline(); ok {
-			timeLeft := time.Until(deadline)
-			timeLeft -= CleanupGracePeriod
-			ctx, cancelTimeout = withTimeout(ctx, tb, timeLeft, fmt.Sprintf("test suite deadline (%s) is close, need to clean up before the %s cleanup grace period", deadline.Truncate(time.Second), CleanupGracePeriod))
-		}
+	if deadline != nil {
+		timeLeft := time.Until(*deadline)
+		timeLeft -= CleanupGracePeriod
+		ctx, cancelTimeout = withTimeout(ctx, tb, timeLeft, fmt.Sprintf("test suite deadline (%s) is close, need to clean up before the %s cleanup grace period", deadline.Truncate(time.Second), CleanupGracePeriod))
 	}
 
 	// Construct new TContext with context and settings as determined above.
 	tCtx := InitCtx(ctx, tb)
+	tCtx.isSyncTest = isSyncTest
 	if cancelTimeout != nil {
 		tCtx.cancel = cancelTimeout
 	} else {
@@ -366,7 +399,7 @@ type TContext struct {
 	// It's empty if there are no steps.
 	steps string
 
-	// for SyncTest
+	// for IsSyncTest
 	isSyncTest bool
 
 	// for WithClient
@@ -483,6 +516,9 @@ func (tCtx TContext) Run(name string, cb func(tCtx TContext)) bool {
 // the bubble directly in the current test context.
 //
 // Only works in Go unit tests.
+//
+// Cleaning up on SIGINT is not available because code running inside a bubble
+// should not depend on outside input.
 func (tCtx TContext) SyncTest(name string, cb func(tCtx TContext)) bool {
 	return run(tCtx, name, true, cb)
 }
diff --git a/test/utils/ktesting/tcontext_test.go b/test/utils/ktesting/tcontext_test.go
index e5f5f7f00ce..01a03015b32 100644
--- a/test/utils/ktesting/tcontext_test.go
+++ b/test/utils/ktesting/tcontext_test.go
@@ -19,6 +19,8 @@ package ktesting_test
 import (
 	"sync"
 	"testing"
+	"testing/synctest"
+	"time"
 
 	"github.com/onsi/gomega"
 	"github.com/stretchr/testify/assert"
@@ -59,6 +61,76 @@ func TestCancelAutomatic(t *testing.T) {
 	}()
 }
 
+func TestSyncTestInit(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		// This must work inside a synctest bubble, despite Deadline panicking there.
+		// We then don't have a deadline.
+		tCtx := ktesting.Init(t)
+		deadline, ok := tCtx.Deadline()
+		if ok {
+			tCtx.Errorf("Expected no deadline, got %s", deadline)
+		}
+		if !tCtx.IsSyncTest() {
+			tCtx.Errorf("Expected to run as synctest")
+		}
+	})
+}
+
+func TestNormalInit(t *testing.T) {
+	// The outcome depends on how the unit test was started.
+	// See below for deterministic deadline/no deadline testing.
+	expectDeadline, expectOK := t.Deadline()
+	expectDeadline = expectDeadline.Add(-ktesting.CleanupGracePeriod)
+	tCtx := ktesting.Init(t)
+	actualDeadline, actualOK := tCtx.Deadline()
+	tCtx.Expect(actualOK).To(gomega.Equal(expectOK), "have deadline")
+	if expectOK {
+		tCtx.Expect(actualDeadline).To(gomega.BeTemporally("~", expectDeadline, 2*time.Second), "deadline")
+	}
+	if tCtx.IsSyncTest() {
+		tCtx.Errorf("Expected to not run as synctest")
+	}
+}
+
+func TestNoDeadline(t *testing.T) {
+	mockT := &deadlineT{T: t, deadline: nil}
+	tCtx := ktesting.Init(mockT)
+	deadline, ok := tCtx.Deadline()
+	if ok {
+		tCtx.Errorf("Expected no deadline, got %s", deadline)
+	}
+}
+
+func TestDeadline(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		// Inside a synctest bubble this is always in the future.
+		mockDeadline := time.Date(2000, 01, 01, 0, 0, 0, 0, time.UTC)
+		mockT := &deadlineT{T: t, deadline: &mockDeadline}
+		tCtx := ktesting.Init(mockT)
+		actualDeadline, ok := tCtx.Deadline()
+		if ok {
+			expectDeadline := mockDeadline.Add(-ktesting.CleanupGracePeriod)
+			tCtx.Expect(actualDeadline).To(gomega.BeTemporally("==", expectDeadline), "deadline")
+		} else {
+			tCtx.Error("Expected a deadline, got none")
+		}
+	})
+}
+
+// deadlineT overrides Deadline, returning false if no
+// deadline is configured and the deadline otherwise.
+type deadlineT struct {
+	*testing.T
+	deadline *time.Time
+}
+
+func (t *deadlineT) Deadline() (time.Time, bool) {
+	if t.deadline == nil {
+		return time.Time{}, false
+	}
+	return *t.deadline, true
+}
+
 func TestCancelCtx(t *testing.T) {
 	tCtx := ktesting.Init(t)
 	var discardLogger klog.Logger