diff --git a/apps/backend/internal/agentctl/server/process/workspace_git_poll.go b/apps/backend/internal/agentctl/server/process/workspace_git_poll.go
index a389bc83c3..e0be429f58 100644
--- a/apps/backend/internal/agentctl/server/process/workspace_git_poll.go
+++ b/apps/backend/internal/agentctl/server/process/workspace_git_poll.go
@@ -39,6 +39,12 @@ func (wt *WorkspaceTracker) pollGitChanges(ctx context.Context) {
 		case <-wt.stopCh:
 			return
 		case <-ticker.C:
+			// Stop polling if the work directory was deleted (worktree removed)
+			if !wt.workDirExists() {
+				wt.logger.Warn("work directory no longer exists, stopping git polling",
+					zap.String("workDir", wt.workDir))
+				return
+			}
 			wt.checkGitChanges(ctx)
 		}
 	}
diff --git a/apps/backend/internal/agentctl/server/process/workspace_monitor.go b/apps/backend/internal/agentctl/server/process/workspace_monitor.go
index 984ff508af..c3dd707ce1 100644
--- a/apps/backend/internal/agentctl/server/process/workspace_monitor.go
+++ b/apps/backend/internal/agentctl/server/process/workspace_monitor.go
@@ -49,7 +49,16 @@ func (wt *WorkspaceTracker) monitorLoop(ctx context.Context) {
 			// Quick state check using mtime + diff-files
 			currentState, err := wt.getWorkspaceState(ctx)
 			if err != nil {
-				// Git command failed - skip this cycle and retry on next tick.
+				// Check if the work directory has been deleted (e.g., worktree removed
+				// after task was archived or PR branch was deleted). If so, stop the
+				// tracker to avoid spamming warnings every poll cycle.
+				if !wt.workDirExists() {
+					wt.logger.Warn("work directory no longer exists, stopping workspace tracker",
+						zap.String("workDir", wt.workDir))
+					return
+				}
+
+				// Git command failed for another reason - skip this cycle and retry on next tick.
 				// Don't update lastState so the change will be detected when git recovers.
 				wt.logger.Warn("failed to get workspace state, will retry next cycle",
 					zap.Error(err))
diff --git a/apps/backend/internal/agentctl/server/process/workspace_monitor_test.go b/apps/backend/internal/agentctl/server/process/workspace_monitor_test.go
new file mode 100644
index 0000000000..a3b024c966
--- /dev/null
+++ b/apps/backend/internal/agentctl/server/process/workspace_monitor_test.go
@@ -0,0 +1,43 @@
+package process
+
+import (
+	"context"
+	"os"
+	"testing"
+	"time"
+)
+
+func TestWorkspaceTracker_StopsWhenWorkDirDeleted(t *testing.T) {
+	isolateTestGitEnv(t)
+
+	repoDir, cleanup := setupTestRepo(t)
+	defer cleanup()
+
+	log := newTestLogger(t)
+	wt := NewWorkspaceTracker(repoDir, log)
+	wt.gitPollInterval = 100 * time.Millisecond
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	wt.Start(ctx)
+
+	// Delete the work directory to simulate worktree removal
+	if err := os.RemoveAll(repoDir); err != nil {
+		t.Fatalf("failed to remove workdir: %v", err)
+	}
+
+	// Both monitorLoop and pollGitChanges should exit within a few poll cycles
+	done := make(chan struct{})
+	go func() {
+		wt.wg.Wait()
+		close(done)
+	}()
+
+	select {
+	case <-done:
+		// Both goroutines exited — success
+	case <-time.After(5 * time.Second):
+		t.Fatal("workspace tracker goroutines did not stop after workdir was deleted")
+	}
+}
diff --git a/apps/backend/internal/agentctl/server/process/workspace_tracker.go b/apps/backend/internal/agentctl/server/process/workspace_tracker.go
index 29f955f925..cae8fcfa94 100644
--- a/apps/backend/internal/agentctl/server/process/workspace_tracker.go
+++ b/apps/backend/internal/agentctl/server/process/workspace_tracker.go
@@ -104,6 +104,15 @@ func resolveGitIndexPath(workDir string) string {
 	return indexPath
 }
 
+// workDirExists checks whether the workspace directory still exists on disk.
+// Used to detect deleted worktrees and stop polling loops gracefully.
+// The workDir is validated at construction time via resolveExistingWorkDir,
+// so this only checks for subsequent deletion (e.g., worktree cleanup).
+func (wt *WorkspaceTracker) workDirExists() bool {
+	_, err := os.Stat(wt.workDir) //nolint:gosec // workDir is validated at construction via resolveExistingWorkDir
+	return !os.IsNotExist(err)
+}
+
 // Start begins monitoring the workspace using polling (no fsnotify).
 // File changes are detected via git status polling, which is efficient and
 // doesn't consume file descriptors like fsnotify/kqueue does on macOS.