diff --git a/internal/boot/boot.go b/internal/boot/boot.go
index 52f22c84..2b1a42f0 100644
--- a/internal/boot/boot.go
+++ b/internal/boot/boot.go
@@ -197,6 +197,11 @@ func (b *Boot) spawnTmux() error {
 	// Launch Claude with environment exported inline and initial triage prompt
 	// The "gt boot triage" prompt tells Boot to immediately start triage (GUPP principle)
 	startCmd := config.BuildAgentStartupCommand("boot", "deacon-boot", "", "gt boot triage")
+	// Wait for shell to be ready before sending keys (prevents "can't find pane" under load)
+	if err := b.tmux.WaitForShellReady(SessionName, 5*time.Second); err != nil {
+		_ = b.tmux.KillSession(SessionName)
+		return fmt.Errorf("waiting for shell: %w", err)
+	}
 	if err := b.tmux.SendKeys(SessionName, startCmd); err != nil {
 		return fmt.Errorf("sending startup command: %w", err)
 	}
diff --git a/internal/deacon/manager.go b/internal/deacon/manager.go
index 8d0f2262..43fda759 100644
--- a/internal/deacon/manager.go
+++ b/internal/deacon/manager.go
@@ -99,6 +99,11 @@ func (m *Manager) Start() error {
 		runtimeCmd,
 	)
 
+	// Wait for shell to be ready before sending keys (prevents "can't find pane" under load)
+	if err := t.WaitForShellReady(sessionID, 5*time.Second); err != nil {
+		_ = t.KillSession(sessionID)
+		return fmt.Errorf("waiting for shell: %w", err)
+	}
 	if err := t.SendKeysDelayed(sessionID, respawnCmd, 200); err != nil {
 		_ = t.KillSession(sessionID) // best-effort cleanup
 		return fmt.Errorf("starting Claude agent: %w", err)
diff --git a/internal/mayor/manager.go b/internal/mayor/manager.go
index 62b74085..3a6a985b 100644
--- a/internal/mayor/manager.go
+++ b/internal/mayor/manager.go
@@ -98,6 +98,11 @@ func (m *Manager) Start(agentOverride string) error {
 		_ = t.KillSession(sessionID) // best-effort cleanup
 		return fmt.Errorf("building startup command: %w", err)
 	}
+	// Wait for shell to be ready before sending keys (prevents "can't find pane" under load)
+	if err := t.WaitForShellReady(sessionID, 5*time.Second); err != nil {
+		_ = t.KillSession(sessionID)
+		return fmt.Errorf("waiting for shell: %w", err)
+	}
 	if err := t.SendKeysDelayed(sessionID, startupCmd, 200); err != nil {
 		_ = t.KillSession(sessionID) // best-effort cleanup
 		return fmt.Errorf("starting Claude agent: %w", err)
diff --git a/internal/polecat/session_manager.go b/internal/polecat/session_manager.go
index e24d8537..bc4e86a5 100644
--- a/internal/polecat/session_manager.go
+++ b/internal/polecat/session_manager.go
@@ -183,6 +183,11 @@ func (m *SessionManager) Start(polecat string, opts SessionStartOptions) error {
 	if command == "" {
 		command = config.BuildPolecatStartupCommand(m.rig.Name, polecat, m.rig.Path, "")
 	}
+	// Wait for shell to be ready before sending keys (prevents "can't find pane" under load)
+	if err := m.tmux.WaitForShellReady(sessionID, 5*time.Second); err != nil {
+		_ = m.tmux.KillSession(sessionID)
+		return fmt.Errorf("waiting for shell: %w", err)
+	}
 	if err := m.tmux.SendKeys(sessionID, command); err != nil {
 		return fmt.Errorf("sending command: %w", err)
 	}
diff --git a/internal/refinery/manager.go b/internal/refinery/manager.go
index 75302161..3f2262b4 100644
--- a/internal/refinery/manager.go
+++ b/internal/refinery/manager.go
@@ -210,6 +210,11 @@ func (m *Manager) Start(foreground bool) error {
 	// Restarts are handled by daemon via LIFECYCLE mail, not shell loops
 	// Export GT_ROLE and BD_ACTOR in the command since tmux SetEnvironment only affects new panes
 	command := config.BuildAgentStartupCommand("refinery", bdActor, m.rig.Path, "")
+	// Wait for shell to be ready before sending keys (prevents "can't find pane" under load)
+	if err := t.WaitForShellReady(sessionID, 5*time.Second); err != nil {
+		_ = t.KillSession(sessionID)
+		return fmt.Errorf("waiting for shell: %w", err)
+	}
 	if err := t.SendKeys(sessionID, command); err != nil {
 		// Clean up the session on failure (best-effort cleanup)
 		_ = t.KillSession(sessionID)
diff --git a/internal/witness/manager.go b/internal/witness/manager.go
index 3d67eff1..884048e8 100644
--- a/internal/witness/manager.go
+++ b/internal/witness/manager.go
@@ -183,6 +183,11 @@ func (m *Manager) Start(foreground bool) error {
 	// Export GT_ROLE and BD_ACTOR in the command since tmux SetEnvironment only affects new panes
 	// Pass m.rig.Path so rig agent settings are honored (not town-level defaults)
 	command := config.BuildAgentStartupCommand("witness", bdActor, m.rig.Path, "")
+	// Wait for shell to be ready before sending keys (prevents "can't find pane" under load)
+	if err := t.WaitForShellReady(sessionID, 5*time.Second); err != nil {
+		_ = t.KillSession(sessionID)
+		return fmt.Errorf("waiting for shell: %w", err)
+	}
 	if err := t.SendKeys(sessionID, command); err != nil {
 		_ = t.KillSession(sessionID) // best-effort cleanup
 		return fmt.Errorf("starting Claude agent: %w", err)