diff --git a/cli/common/ui/spinner.go b/cli/common/ui/spinner.go
index 775eb97dc0..f805b3bc2a 100644
--- a/cli/common/ui/spinner.go
+++ b/cli/common/ui/spinner.go
@@ -12,20 +12,26 @@ import (
 
 const (
 	spinnerFrameInterval = 80 * time.Millisecond
+	// Without a spinner a notice becomes a line that piles up instead of being redrawn; at the
+	// heartbeat cadence (10s) a 5-minute stall would print 30 lines, so it matches the 60-second
+	// cadence of compile's interim reports.
+	noticeLineInterval = 60 * time.Second
 )
 
 var spinnerFrames = []string{"⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"}
 
 type TerminalSpinner struct {
-	writer      io.Writer
-	Enabled     bool
-	message     string
-	frame       int
-	done        chan struct{}
-	stopped     chan struct{}
-	stopOnce    sync.Once
-	mutex       sync.Mutex
-	stoppedFlag bool
+	writer       io.Writer
+	Enabled      bool
+	message      string
+	frame        int
+	done         chan struct{}
+	stopped      chan struct{}
+	stopOnce     sync.Once
+	mutex        sync.Mutex
+	stoppedFlag  bool
+	now          func() time.Time
+	lastNoticeAt time.Time
 }
 
 func NewToolSpinner(stderr io.Writer, showFeedback bool) *TerminalSpinner {
@@ -41,15 +47,16 @@ func NewLaunchSpinner(stdout io.Writer, stderr io.Writer) *TerminalSpinner {
 
 // Maps connection-stage progress events to the contextual executing message
 // and passes display-ready payloads (such as the heartbeat main-thread stall
-// notice) through to the spinner verbatim. Without this mapping the stall
-// diagnosis built by the IPC client would never reach the user.
+// notice) through verbatim as notices, which are written as lines even when no
+// spinner is shown. Without this mapping the stall diagnosis built by the IPC
+// client would never reach the user.
 func NewSpinnerProgressFunc(spinner *TerminalSpinner, executingMessage string) progress.Func {
 	return func(event progress.Event) {
 		if event.Stage == progress.StageConnected || event.Stage == progress.StageAccepted {
 			spinner.Update(executingMessage)
 			return
 		}
-		spinner.Update(event.Message)
+		spinner.Notice(event.Message)
 	}
 }
 
@@ -60,6 +67,7 @@ func newSpinner(writer io.Writer, enabled bool, message string) *TerminalSpinner
 		message: message,
 		done:    make(chan struct{}),
 		stopped: make(chan struct{}),
+		now:     time.Now,
 	}
 
 	if !enabled {
@@ -87,8 +95,35 @@ func (spinner *TerminalSpinner) Update(message string) {
 	spinner.render()
 }
 
+// Notice shows a message that must reach the reader even when no spinner is
+// shown, because agents read stderr through a pipe rather than a terminal. An
+// enabled spinner shows it in place; otherwise it is written as a plain line, at
+// most once per noticeLineInterval.
+func (spinner *TerminalSpinner) Notice(message string) {
+	if spinner.Enabled {
+		spinner.Update(message)
+		return
+	}
+
+	spinner.mutex.Lock()
+	defer spinner.mutex.Unlock()
+	if spinner.stoppedFlag {
+		return
+	}
+	now := spinner.now()
+	if !spinner.lastNoticeAt.IsZero() && now.Sub(spinner.lastNoticeAt) < noticeLineInterval {
+		return
+	}
+	spinner.lastNoticeAt = now
+	_, _ = fmt.Fprintln(spinner.writer, message)
+}
+
 func (spinner *TerminalSpinner) Stop() {
 	if !spinner.Enabled {
+		// Marked stopped so a notice that arrives after the command ends writes no line.
+		spinner.mutex.Lock()
+		spinner.stoppedFlag = true
+		spinner.mutex.Unlock()
 		return
 	}
 
diff --git a/cli/common/ui/spinner_test.go b/cli/common/ui/spinner_test.go
index f3d058e41e..59000147e2 100644
--- a/cli/common/ui/spinner_test.go
+++ b/cli/common/ui/spinner_test.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/hatayama/unity-cli-loop/common/progress"
 )
@@ -247,3 +248,86 @@ func TestSpinnerRenderAfterStopWritesNothing(t *testing.T) {
 		t.Fatalf("render after Stop wrote output: %q", stderr.String()[len(afterStop):])
 	}
 }
+
+func TestDisabledSpinnerNoticeWritesOneLine(t *testing.T) {
+	// Verifies a notice on a disabled spinner reaches stderr as one plain line without terminal control codes.
+	var stderr bytes.Buffer
+	spinner := newSpinner(&stderr, false, "Connecting to Unity...")
+
+	spinner.Notice("Unity main thread stuck 30s; check modal/long operation...")
+
+	want := "Unity main thread stuck 30s; check modal/long operation...\n"
+	if stderr.String() != want {
+		t.Fatalf("disabled spinner notice = %q, want %q", stderr.String(), want)
+	}
+}
+
+func TestDisabledSpinnerNoticeRateLimitsToOneLinePerMinute(t *testing.T) {
+	// Verifies notices without a spinner are written at most once per minute so a long stall does not pile up lines.
+	var stderr bytes.Buffer
+	spinner := newSpinner(&stderr, false, "Connecting to Unity...")
+	start := time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC)
+	current := start
+	spinner.now = func() time.Time { return current }
+
+	spinner.Notice("first")
+	current = start.Add(59 * time.Second)
+	spinner.Notice("second")
+	current = start.Add(60 * time.Second)
+	spinner.Notice("third")
+
+	if stderr.String() != "first\nthird\n" {
+		t.Fatalf("rate-limited notices = %q, want %q", stderr.String(), "first\nthird\n")
+	}
+}
+
+func TestDisabledSpinnerNoticeAfterStopWritesNothing(t *testing.T) {
+	// Verifies a notice that arrives after Stop on a disabled spinner is dropped.
+	var stderr bytes.Buffer
+	spinner := newSpinner(&stderr, false, "Connecting to Unity...")
+	spinner.Stop()
+
+	spinner.Notice("late notice")
+
+	if stderr.Len() != 0 {
+		t.Fatalf("notice after Stop wrote output: %q", stderr.String())
+	}
+}
+
+func TestEnabledSpinnerNoticeUpdatesInPlace(t *testing.T) {
+	// Verifies a notice on an enabled spinner replaces the spinner message instead of writing its own line.
+	var stderr bytes.Buffer
+	spinner := newSpinner(&stderr, true, "Connecting to Unity...")
+
+	spinner.Notice("stall notice")
+	spinner.Stop()
+
+	output := stderr.String()
+	if !strings.Contains(output, "stall notice") {
+		t.Fatalf("enabled spinner output did not include the notice: %q", output)
+	}
+	if strings.Contains(output, "stall notice\n") {
+		t.Fatalf("enabled spinner wrote the notice as its own line: %q", output)
+	}
+}
+
+func TestSpinnerProgressFuncWritesStallNoticeAsLineWithoutSpinner(t *testing.T) {
+	// Verifies that without a spinner, connection events stay silent while the stall notice is written as a line.
+	var stderr bytes.Buffer
+	spinner := newSpinner(&stderr, false, "Connecting to Unity...")
+	progressFunc := NewSpinnerProgressFunc(spinner, "Executing get-logs...")
+
+	progressFunc(progress.Event{Stage: progress.StageConnected})
+	if stderr.Len() != 0 {
+		t.Fatalf("connection event wrote output without a spinner: %q", stderr.String())
+	}
+	progressFunc(progress.Event{
+		Stage:   progress.StageMessage,
+		Message: "Unity main thread stuck 30s; check modal/long operation...",
+	})
+
+	want := "Unity main thread stuck 30s; check modal/long operation...\n"
+	if stderr.String() != want {
+		t.Fatalf("stall notice without spinner = %q, want %q", stderr.String(), want)
+	}
+}
diff --git a/cli/dispatcher/shared-inputs-stamp.json b/cli/dispatcher/shared-inputs-stamp.json
index ef93adeb92..b040c259e1 100644
--- a/cli/dispatcher/shared-inputs-stamp.json
+++ b/cli/dispatcher/shared-inputs-stamp.json
@@ -1,4 +1,4 @@
 {
   "schemaVersion": 1,
-  "sharedInputsHash": "23acd185b352d8863851088bbfb9623193a604c0"
+  "sharedInputsHash": "292bd6079496d0865f852146f0a3829d8492dfd0"
 }
diff --git a/cli/project-runner/shared-inputs-stamp.json b/cli/project-runner/shared-inputs-stamp.json
index 325526c139..be37531b5e 100644
--- a/cli/project-runner/shared-inputs-stamp.json
+++ b/cli/project-runner/shared-inputs-stamp.json
@@ -1,4 +1,4 @@
 {
   "schemaVersion": 1,
-  "sharedInputsHash": "fb98448944d852bca377103bb80ee814c12e49d1"
+  "sharedInputsHash": "1db5b8eb574726147b628d2832ceac7a691426ba"
 }