diff --git a/codex-rs/core/src/compact.rs b/codex-rs/core/src/compact.rs
index 40e6284deb..17963a04f8 100644
--- a/codex-rs/core/src/compact.rs
+++ b/codex-rs/core/src/compact.rs
@@ -11,6 +11,7 @@ use crate::error::Result as CodexResult;
 use crate::features::Feature;
 use crate::protocol::CompactedItem;
 use crate::protocol::ContextCompactedEvent;
+use crate::protocol::ContextCompactionStartedEvent;
 use crate::protocol::EventMsg;
 use crate::protocol::TurnContextItem;
 use crate::protocol::TurnStartedEvent;
@@ -70,6 +71,9 @@ async fn run_compact_task_inner(
     turn_context: Arc<TurnContext>,
     input: Vec<UserInput>,
 ) {
+    let start_event = EventMsg::ContextCompactionStarted(ContextCompactionStartedEvent {});
+    sess.send_event(&turn_context, start_event).await;
+
     let initial_input_for_turn: ResponseInputItem = ResponseInputItem::from(input);
 
     let mut history = sess.clone_history().await;
diff --git a/codex-rs/core/src/compact_remote.rs b/codex-rs/core/src/compact_remote.rs
index dd038c5287..bb360db3f2 100644
--- a/codex-rs/core/src/compact_remote.rs
+++ b/codex-rs/core/src/compact_remote.rs
@@ -6,6 +6,7 @@ use crate::codex::TurnContext;
 use crate::error::Result as CodexResult;
 use crate::protocol::CompactedItem;
 use crate::protocol::ContextCompactedEvent;
+use crate::protocol::ContextCompactionStartedEvent;
 use crate::protocol::EventMsg;
 use crate::protocol::RolloutItem;
 use crate::protocol::TurnStartedEvent;
@@ -40,6 +41,9 @@ async fn run_remote_compact_task_inner_impl(
     sess: &Arc<Session>,
     turn_context: &Arc<TurnContext>,
 ) -> CodexResult<()> {
+    let start_event = EventMsg::ContextCompactionStarted(ContextCompactionStartedEvent {});
+    sess.send_event(turn_context, start_event).await;
+
     let history = sess.clone_history().await;
 
     // Required to keep `/undo` available after compaction
diff --git a/codex-rs/core/src/rollout/policy.rs b/codex-rs/core/src/rollout/policy.rs
index 2d4a79cc22..4312650a95 100644
--- a/codex-rs/core/src/rollout/policy.rs
+++ b/codex-rs/core/src/rollout/policy.rs
@@ -42,6 +42,7 @@ pub(crate) fn should_persist_event_msg(ev: &EventMsg) -> bool {
         | EventMsg::AgentReasoning(_)
         | EventMsg::AgentReasoningRawContent(_)
         | EventMsg::TokenCount(_)
+        | EventMsg::ContextCompactionStarted(_)
         | EventMsg::ContextCompacted(_)
         | EventMsg::EnteredReviewMode(_)
         | EventMsg::ExitedReviewMode(_)
diff --git a/codex-rs/exec/src/event_processor_with_human_output.rs b/codex-rs/exec/src/event_processor_with_human_output.rs
index c4a5c27d9c..d6c17d4906 100644
--- a/codex-rs/exec/src/event_processor_with_human_output.rs
+++ b/codex-rs/exec/src/event_processor_with_human_output.rs
@@ -568,8 +568,11 @@ impl EventProcessor for EventProcessorWithHumanOutput {
                     ts_msg!(self, "task aborted: review ended");
                 }
             },
+            EventMsg::ContextCompactionStarted(_) => {
+                ts_msg!(self, "compact started");
+            }
             EventMsg::ContextCompacted(_) => {
-                ts_msg!(self, "context compacted");
+                ts_msg!(self, "compact ended");
             }
             EventMsg::CollabAgentSpawnBegin(_)
             | EventMsg::CollabAgentSpawnEnd(_)
diff --git a/codex-rs/mcp-server/src/codex_tool_runner.rs b/codex-rs/mcp-server/src/codex_tool_runner.rs
index b268b8f1b4..20a49c4fce 100644
--- a/codex-rs/mcp-server/src/codex_tool_runner.rs
+++ b/codex-rs/mcp-server/src/codex_tool_runner.rs
@@ -359,6 +359,7 @@ async fn run_codex_tool_session_inner(
                     | EventMsg::UndoCompleted(_)
                     | EventMsg::ExitedReviewMode(_)
                     | EventMsg::RequestUserInput(_)
+                    | EventMsg::ContextCompactionStarted(_)
                     | EventMsg::ContextCompacted(_)
                     | EventMsg::ThreadRolledBack(_)
                     | EventMsg::CollabAgentSpawnBegin(_)
diff --git a/codex-rs/protocol/src/protocol.rs b/codex-rs/protocol/src/protocol.rs
index d5accde8e8..42d85934c3 100644
--- a/codex-rs/protocol/src/protocol.rs
+++ b/codex-rs/protocol/src/protocol.rs
@@ -658,6 +658,9 @@ pub enum EventMsg {
     /// indicates the turn continued but the user should still be notified.
     Warning(WarningEvent),
 
+    /// Conversation history compaction has started.
+    ContextCompactionStarted(ContextCompactionStartedEvent),
+
     /// Conversation history was compacted (either automatically or manually).
     ContextCompacted(ContextCompactedEvent),
 
@@ -1049,6 +1052,9 @@ pub struct WarningEvent {
     pub message: String,
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
+pub struct ContextCompactionStartedEvent;
+
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
 pub struct ContextCompactedEvent;
 
diff --git a/codex-rs/tui/src/chatwidget.rs b/codex-rs/tui/src/chatwidget.rs
index 2518eb41bc..ff0a0eee50 100644
--- a/codex-rs/tui/src/chatwidget.rs
+++ b/codex-rs/tui/src/chatwidget.rs
@@ -2530,7 +2530,10 @@ impl ChatWidget {
                 self.on_entered_review_mode(review_request, from_replay)
             }
             EventMsg::ExitedReviewMode(review) => self.on_exited_review_mode(review),
-            EventMsg::ContextCompacted(_) => self.on_agent_message("Context compacted".to_owned()),
+            EventMsg::ContextCompactionStarted(_) => {
+                self.on_agent_message("Compact started".to_owned())
+            }
+            EventMsg::ContextCompacted(_) => self.on_agent_message("Compact ended".to_owned()),
             EventMsg::CollabAgentSpawnBegin(_) => {}
             EventMsg::CollabAgentSpawnEnd(ev) => self.on_collab_event(collab::spawn_end(ev)),
             EventMsg::CollabAgentInteractionBegin(_) => {}
diff --git a/codex-rs/tui2/src/chatwidget.rs b/codex-rs/tui2/src/chatwidget.rs
index ffc763e214..90eac1be9c 100644
--- a/codex-rs/tui2/src/chatwidget.rs
+++ b/codex-rs/tui2/src/chatwidget.rs
@@ -2301,7 +2301,10 @@ impl ChatWidget {
                 self.on_entered_review_mode(review_request)
             }
             EventMsg::ExitedReviewMode(review) => self.on_exited_review_mode(review),
-            EventMsg::ContextCompacted(_) => self.on_agent_message("Context compacted".to_owned()),
+            EventMsg::ContextCompactionStarted(_) => {
+                self.on_agent_message("Compact started".to_owned())
+            }
+            EventMsg::ContextCompacted(_) => self.on_agent_message("Compact ended".to_owned()),
             EventMsg::CollabAgentSpawnBegin(_) => {}
             EventMsg::CollabAgentSpawnEnd(ev) => self.on_collab_event(collab::spawn_end(ev)),
             EventMsg::CollabAgentInteractionBegin(_) => {}