diff --git a/src/common/ordered_terminal_events.rs b/src/common/ordered_terminal_events.rs
index 7461391..6f27c88 100644
--- a/src/common/ordered_terminal_events.rs
+++ b/src/common/ordered_terminal_events.rs
@@ -60,6 +60,17 @@ pub enum OrderedTerminalEventType {
     AgentConversationReplayStarted,
     /// Marks the end of historical agent conversation replay.
     AgentConversationReplayEnded,
+    /// Emitted by the sandboxed Oz AgentDriver when the cloud-mode setup phase is complete but no
+    /// initial LLM turn will follow (e.g. empty-prompt local-to-cloud handoff with
+    /// `--skip-initial-turn`). The viewer uses this to tear down the Cloud Mode Setup V2
+    /// "Running setup commands…" chip and clear `BlockList::is_executing_oz_environment_startup_commands`
+    /// without needing to wait for the first `AppendedExchange`.
+    ///
+    /// There is no matching `AmbientSetupPhaseStarted` variant: setup-phase start is already
+    /// implicit in the existing `SetupCommandState` transitions on the viewer (the default
+    /// `running_group_id` is `Some(initial)` once scrollback arrives), so an explicit start
+    /// marker would be redundant.
+    AmbientSetupPhaseEnded,
 }
 
 /// Represents the size of a PTY. Mimics the winsize struct that
@@ -82,6 +93,7 @@ impl std::fmt::Debug for OrderedTerminalEventType {
             Self::AgentResponseEvent { .. } => f.write_str("AgentResponseEvent"),
             Self::AgentConversationReplayStarted => f.write_str("AgentConversationReplayStarted"),
             Self::AgentConversationReplayEnded => f.write_str("AgentConversationReplayEnded"),
+            Self::AmbientSetupPhaseEnded => f.write_str("AmbientSetupPhaseEnded"),
         }
     }
 }
@@ -97,6 +109,7 @@ impl OrderedTerminalEventType {
             | OrderedTerminalEventType::CommandExecutionFinished { .. }
             | OrderedTerminalEventType::AgentConversationReplayStarted
             | OrderedTerminalEventType::AgentConversationReplayEnded
+            | OrderedTerminalEventType::AmbientSetupPhaseEnded
             | OrderedTerminalEventType::Resize { .. } => Byte::from_u64(0),
         }
     }
@@ -114,3 +127,31 @@ impl OrderedTerminalEvent {
         self.event_type.num_bytes()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn ambient_setup_phase_ended_serializes_as_unit_variant() {
+        let event_type = OrderedTerminalEventType::AmbientSetupPhaseEnded;
+        let json = serde_json::to_string(&event_type).expect("serialize");
+        assert_eq!(json, "\"AmbientSetupPhaseEnded\"");
+    }
+
+    #[test]
+    fn ambient_setup_phase_ended_round_trips() {
+        let event = OrderedTerminalEvent {
+            event_no: 42,
+            event_type: OrderedTerminalEventType::AmbientSetupPhaseEnded,
+        };
+        let json = serde_json::to_string(&event).expect("serialize");
+        let parsed: OrderedTerminalEvent = serde_json::from_str(&json).expect("deserialize");
+        assert_eq!(parsed.event_no, 42);
+        assert!(matches!(
+            parsed.event_type,
+            OrderedTerminalEventType::AmbientSetupPhaseEnded
+        ));
+        assert_eq!(parsed.num_bytes(), Byte::from_u64(0));
+    }
+}