diff --git a/internal/deacon/manager.go b/internal/deacon/manager.go
index d4e45aa6..ec16bbf7 100644
--- a/internal/deacon/manager.go
+++ b/internal/deacon/manager.go
@@ -106,9 +106,11 @@ func (m *Manager) Start(agentOverride string) error {
 	theme := tmux.DeaconTheme()
 	_ = t.ConfigureGasTownSession(sessionID, theme, "", "Deacon", "health-check")
 
-	// Wait for Claude to start (non-fatal)
+	// Wait for Claude to start - fatal if Claude fails to launch
 	if err := t.WaitForCommand(sessionID, constants.SupportedShells, constants.ClaudeStartTimeout); err != nil {
-		// Non-fatal - try to continue anyway
+		// Kill the zombie session before returning error
+		_ = t.KillSessionWithProcesses(sessionID)
+		return fmt.Errorf("waiting for deacon to start: %w", err)
 	}
 
 	// Accept bypass permissions warning dialog if it appears.
diff --git a/internal/mayor/manager.go b/internal/mayor/manager.go
index eea57071..855cae31 100644
--- a/internal/mayor/manager.go
+++ b/internal/mayor/manager.go
@@ -114,9 +114,11 @@ func (m *Manager) Start(agentOverride string) error {
 	theme := tmux.MayorTheme()
 	_ = t.ConfigureGasTownSession(sessionID, theme, "", "Mayor", "coordinator")
 
-	// Wait for Claude to start (non-fatal)
+	// Wait for Claude to start - fatal if Claude fails to launch
 	if err := t.WaitForCommand(sessionID, constants.SupportedShells, constants.ClaudeStartTimeout); err != nil {
-		// Non-fatal - try to continue anyway
+		// Kill the zombie session before returning error
+		_ = t.KillSessionWithProcesses(sessionID)
+		return fmt.Errorf("waiting for mayor to start: %w", err)
 	}
 
 	// Accept bypass permissions warning dialog if it appears.
diff --git a/internal/refinery/manager.go b/internal/refinery/manager.go
index 41d539e8..0534cab4 100644
--- a/internal/refinery/manager.go
+++ b/internal/refinery/manager.go
@@ -223,10 +223,12 @@ func (m *Manager) Start(foreground bool, agentOverride string) error {
 		return fmt.Errorf("saving state: %w", err)
 	}
 
-	// Wait for Claude to start and show its prompt (non-fatal)
+	// Wait for Claude to start and show its prompt - fatal if Claude fails to launch
 	// WaitForRuntimeReady waits for the runtime to be ready
 	if err := t.WaitForRuntimeReady(sessionID, runtimeConfig, constants.ClaudeStartTimeout); err != nil {
-		// Non-fatal - try to continue anyway
+		// Kill the zombie session before returning error
+		_ = t.KillSessionWithProcesses(sessionID)
+		return fmt.Errorf("waiting for refinery to start: %w", err)
 	}
 
 	// Accept bypass permissions warning dialog if it appears.
diff --git a/internal/witness/manager.go b/internal/witness/manager.go
index bd26933a..78e262a8 100644
--- a/internal/witness/manager.go
+++ b/internal/witness/manager.go
@@ -211,9 +211,11 @@ func (m *Manager) Start(foreground bool, agentOverride string, envOverrides []st
 		return fmt.Errorf("saving state: %w", err)
 	}
 
-	// Wait for Claude to start (non-fatal).
+	// Wait for Claude to start - fatal if Claude fails to launch
 	if err := t.WaitForCommand(sessionID, constants.SupportedShells, constants.ClaudeStartTimeout); err != nil {
-		// Non-fatal - try to continue anyway
+		// Kill the zombie session before returning error
+		_ = t.KillSessionWithProcesses(sessionID)
+		return fmt.Errorf("waiting for witness to start: %w", err)
 	}
 
 	// Accept bypass permissions warning dialog if it appears.