diff --git a/pkg/tui/components/sidebar/main_test.go b/pkg/tui/components/sidebar/main_test.go
new file mode 100644
index 000000000..883f4f914
--- /dev/null
+++ b/pkg/tui/components/sidebar/main_test.go
@@ -0,0 +1,15 @@
+package sidebar
+
+import (
+	"os"
+	"testing"
+)
+
+// The test binary runs inside the repository checkout; pin the working
+// directory and branch so layouts do not depend on the checkout's branch name.
+func TestMain(m *testing.M) {
+	restore := SetWorkingDirectoryForTesting("/work/app", "")
+	code := m.Run()
+	restore()
+	os.Exit(code)
+}
diff --git a/pkg/tui/components/sidebar/sidebar.go b/pkg/tui/components/sidebar/sidebar.go
index 4e6f1aee3..0392bc724 100644
--- a/pkg/tui/components/sidebar/sidebar.go
+++ b/pkg/tui/components/sidebar/sidebar.go
@@ -2,6 +2,7 @@ package sidebar
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"log/slog"
 	"maps"
@@ -161,6 +162,31 @@ type Model interface {
 
 type gitBranchChangedMsg string
 
+// Seams for the process state the sidebar reads at construction. Unit tests
+// run inside the repository checkout, so without them the checkout's branch
+// name (60 characters in a merge queue) leaks into every rendered layout.
+var (
+	getwd         = os.Getwd
+	currentBranch = gitbranch.Current
+	watchBranch   = gitbranch.Watch
+)
+
+var errBranchWatcherDisabled = errors.New("sidebar: git branch watcher disabled for testing")
+
+// SetWorkingDirectoryForTesting makes every sidebar created afterwards report
+// dir and branch instead of the process's working directory and its git
+// branch, with no branch watcher, and returns a function restoring the
+// defaults. Call it from TestMain: it is not safe alongside running tests.
+func SetWorkingDirectoryForTesting(dir, branch string) (restore func()) {
+	prevGetwd, prevCurrent, prevWatch := getwd, currentBranch, watchBranch
+	getwd = func() (string, error) { return dir, nil }
+	currentBranch = func(string) string { return branch }
+	watchBranch = func(context.Context, string) (*gitbranch.Watcher, error) {
+		return nil, errBranchWatcherDisabled
+	}
+	return func() { getwd, currentBranch, watchBranch = prevGetwd, prevCurrent, prevWatch }
+}
+
 func waitForGitBranch(watcher *gitbranch.Watcher) tea.Cmd {
 	if watcher == nil {
 		return nil
@@ -397,9 +423,9 @@ func New(ar *animation.Runtime, ctx context.Context, sessionState *service.Sessi
 	ti.CharLimit = 50
 	ti.Prompt = "" // No prompt to maximize usable width in collapsed sidebar
 
-	rawDir, _ := os.Getwd()
+	rawDir, _ := getwd()
 	wd, branch := formatWorkingDirectory(rawDir)
-	branchWatcher, _ := gitbranch.Watch(ctx, rawDir)
+	branchWatcher, _ := watchBranch(ctx, rawDir)
 
 	m := &model{
 		ctx:               func() context.Context { return context.WithoutCancel(ctx) },
@@ -1024,7 +1050,7 @@ func (m *model) LoadFromSession(sess *session.Session) {
 		if m.gitBranchWatcher != nil {
 			m.gitBranchName = m.gitBranchWatcher.SetDir(sess.WorkingDir)
 		} else {
-			m.gitBranchName = gitbranch.Current(sess.WorkingDir)
+			m.gitBranchName = currentBranch(sess.WorkingDir)
 		}
 	}
 
@@ -1156,7 +1182,7 @@ func formatWorkingDirectory(rawDir string) (display, branch string) {
 	if rawDir == "" {
 		return "", ""
 	}
-	return pathx.ShortenHome(rawDir), gitbranch.Current(rawDir)
+	return pathx.ShortenHome(rawDir), currentBranch(rawDir)
 }
 
 // workingDirWithBranch returns the working directory path with the git branch
diff --git a/pkg/tui/components/sidebar/working_directory_test.go b/pkg/tui/components/sidebar/working_directory_test.go
new file mode 100644
index 000000000..2474a42a8
--- /dev/null
+++ b/pkg/tui/components/sidebar/working_directory_test.go
@@ -0,0 +1,30 @@
+package sidebar
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/docker/docker-agent/pkg/session"
+	"github.com/docker/docker-agent/pkg/tui/animation"
+	"github.com/docker/docker-agent/pkg/tui/service"
+)
+
+// TestNewIgnoresProcessGitState pins the TestMain seam: a new sidebar shows
+// the injected directory with no branch and no watcher, whatever repository
+// the test binary happens to run in.
+func TestNewIgnoresProcessGitState(t *testing.T) {
+	t.Parallel()
+
+	sess := session.New()
+	sb := New(animation.NewRuntime(), t.Context(), service.NewSessionState(sess))
+	m := sb.(*model)
+
+	// The display path is normalized to the OS separator.
+	assert.Equal(t, filepath.FromSlash("/work/app"), m.workingDirectory)
+	assert.Empty(t, m.gitBranchName)
+	require.Nil(t, m.gitBranchWatcher)
+	assert.Nil(t, m.Init(), "no watcher means nothing to wait for")
+}
diff --git a/pkg/tui/main_test.go b/pkg/tui/main_test.go
new file mode 100644
index 000000000..4a8e9433e
--- /dev/null
+++ b/pkg/tui/main_test.go
@@ -0,0 +1,18 @@
+package tui
+
+import (
+	"os"
+	"testing"
+
+	"github.com/docker/docker-agent/pkg/tui/components/sidebar"
+)
+
+// The test binary runs inside the repository checkout; pin the sidebar's
+// working directory and branch so layouts do not depend on the checkout's
+// branch name.
+func TestMain(m *testing.M) {
+	restore := sidebar.SetWorkingDirectoryForTesting("/work/app", "")
+	code := m.Run()
+	restore()
+	os.Exit(code)
+}
diff --git a/pkg/tui/page/chat/main_test.go b/pkg/tui/page/chat/main_test.go
new file mode 100644
index 000000000..45fc6c302
--- /dev/null
+++ b/pkg/tui/page/chat/main_test.go
@@ -0,0 +1,18 @@
+package chat
+
+import (
+	"os"
+	"testing"
+
+	"github.com/docker/docker-agent/pkg/tui/components/sidebar"
+)
+
+// The test binary runs inside the repository checkout; pin the sidebar's
+// working directory and branch so layouts do not depend on the checkout's
+// branch name.
+func TestMain(m *testing.M) {
+	restore := sidebar.SetWorkingDirectoryForTesting("/work/app", "")
+	code := m.Run()
+	restore()
+	os.Exit(code)
+}