compaction (#10034)

# External (non-OpenAI) Pull Request Requirements

Before opening this Pull Request, please read the dedicated
"Contributing" markdown file or your PR may be closed:
https://github.com/openai/codex/blob/main/docs/contributing.md

If your PR conforms to our contribution guidelines, replace this text
with a detailed and high quality description of your changes.

Include a link to a bug report or enhancement request.

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -598,6 +598,7 @@ server_notification_definitions! {
     ReasoningSummaryTextDelta => "item/reasoning/summaryTextDelta" (v2::ReasoningSummaryTextDeltaNotification),
     ReasoningSummaryPartAdded => "item/reasoning/summaryPartAdded" (v2::ReasoningSummaryPartAddedNotification),
     ReasoningTextDelta => "item/reasoning/textDelta" (v2::ReasoningTextDeltaNotification),
+    /// Deprecated: Use `ContextCompaction` item type instead.
     ContextCompacted => "thread/compacted" (v2::ContextCompactedNotification),
     DeprecationNotice => "deprecationNotice" (v2::DeprecationNoticeNotification),
     ConfigWarning => "configWarning" (v2::ConfigWarningNotification),

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -2029,6 +2029,9 @@ pub enum ThreadItem {
     #[serde(rename_all = "camelCase")]
     #[ts(rename_all = "camelCase")]
     ExitedReviewMode { id: String, review: String },
+    #[serde(rename_all = "camelCase")]
+    #[ts(rename_all = "camelCase")]
+    ContextCompaction { id: String },
 }
 
 impl From<CoreTurnItem> for ThreadItem {
@@ -2057,6 +2060,9 @@ impl From<CoreTurnItem> for ThreadItem {
                 id: search.id,
                 query: search.query,
             },
+            CoreTurnItem::ContextCompaction(compaction) => {
+                ThreadItem::ContextCompaction { id: compaction.id }
+            }
         }
     }
 }
@@ -2419,6 +2425,7 @@ pub struct WindowsWorldWritableWarningNotification {
     pub failed_scan: bool,
 }
 
+/// Deprecated: Use `ContextCompaction` item type instead.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]

codex-rs/app-server/README.md

@@ -431,7 +431,8 @@ Today both notifications carry an empty `items` array even when item events were
 - `imageView` — `{id, path}` emitted when the agent invokes the image viewer tool.
 - `enteredReviewMode` — `{id, review}` sent when the reviewer starts; `review` is a short user-facing label such as `"current changes"` or the requested target description.
 - `exitedReviewMode` — `{id, review}` emitted when the reviewer finishes; `review` is the full plain-text review (usually, overall notes plus bullet point findings).
-- `compacted` - `{threadId, turnId}` when codex compacts the conversation history. This can happen automatically.
+- `contextCompaction` — `{id}` emitted when codex compacts the conversation history. This can happen automatically.
+- `compacted` - `{threadId, turnId}` when codex compacts the conversation history. This can happen automatically. **Deprecated:** Use `contextCompaction` instead.
 
 All items emit two shared lifecycle events:
 

codex-rs/core/src/compact.rs

@@ -10,7 +10,6 @@ use crate::error::CodexErr;
 use crate::error::Result as CodexResult;
 use crate::features::Feature;
 use crate::protocol::CompactedItem;
-use crate::protocol::ContextCompactedEvent;
 use crate::protocol::EventMsg;
 use crate::protocol::TurnContextItem;
 use crate::protocol::TurnStartedEvent;
@@ -20,6 +19,7 @@ use crate::truncate::TruncationPolicy;
 use crate::truncate::approx_token_count;
 use crate::truncate::truncate_text;
 use crate::util::backoff;
+use codex_protocol::items::ContextCompactionItem;
 use codex_protocol::items::TurnItem;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseInputItem;
@@ -71,6 +71,9 @@ async fn run_compact_task_inner(
     turn_context: Arc<TurnContext>,
     input: Vec<UserInput>,
 ) {
+    let compaction_item = TurnItem::ContextCompaction(ContextCompactionItem::new());
+    sess.emit_turn_item_started(&turn_context, &compaction_item)
+        .await;
     let initial_input_for_turn: ResponseInputItem = ResponseInputItem::from(input);
 
     let mut history = sess.clone_history().await;
@@ -193,9 +196,8 @@ async fn run_compact_task_inner(
     });
     sess.persist_rollout_items(&[rollout_item]).await;
 
-    let event = EventMsg::ContextCompacted(ContextCompactedEvent {});
-    sess.send_event(&turn_context, event).await;
-
+    sess.emit_turn_item_completed(&turn_context, compaction_item)
+        .await;
     let warning = EventMsg::Warning(WarningEvent {
         message: "Heads up: Long threads and multiple compactions can cause the model to be less accurate. Start a new thread when possible to keep threads small and targeted.".to_string(),
     });

codex-rs/core/src/compact_remote.rs

@@ -5,10 +5,11 @@ use crate::codex::Session;
 use crate::codex::TurnContext;
 use crate::error::Result as CodexResult;
 use crate::protocol::CompactedItem;
-use crate::protocol::ContextCompactedEvent;
 use crate::protocol::EventMsg;
 use crate::protocol::RolloutItem;
 use crate::protocol::TurnStartedEvent;
+use codex_protocol::items::ContextCompactionItem;
+use codex_protocol::items::TurnItem;
 use codex_protocol::models::ResponseItem;
 
 pub(crate) async fn run_inline_remote_auto_compact_task(
@@ -40,6 +41,9 @@ async fn run_remote_compact_task_inner_impl(
     sess: &Arc<Session>,
     turn_context: &Arc<TurnContext>,
 ) -> CodexResult<()> {
+    let compaction_item = TurnItem::ContextCompaction(ContextCompactionItem::new());
+    sess.emit_turn_item_started(turn_context, &compaction_item)
+        .await;
     let history = sess.clone_history().await;
 
     // Required to keep `/undo` available after compaction
@@ -77,8 +81,7 @@ async fn run_remote_compact_task_inner_impl(
     sess.persist_rollout_items(&[RolloutItem::Compacted(compacted_item)])
         .await;
 
-    let event = EventMsg::ContextCompacted(ContextCompactedEvent {});
-    sess.send_event(turn_context, event).await;
-
+    sess.emit_turn_item_completed(turn_context, compaction_item)
+        .await;
     Ok(())
 }

codex-rs/core/tests/suite/compact.rs

@@ -8,12 +8,15 @@ use codex_core::config::Config;
 use codex_core::features::Feature;
 use codex_core::protocol::AskForApproval;
 use codex_core::protocol::EventMsg;
+use codex_core::protocol::ItemCompletedEvent;
+use codex_core::protocol::ItemStartedEvent;
 use codex_core::protocol::Op;
 use codex_core::protocol::RolloutItem;
 use codex_core::protocol::RolloutLine;
 use codex_core::protocol::SandboxPolicy;
 use codex_core::protocol::WarningEvent;
 use codex_protocol::config_types::ReasoningSummary;
+use codex_protocol::items::TurnItem;
 use codex_protocol::user_input::UserInput;
 use core_test_support::responses::ev_local_shell_call;
 use core_test_support::responses::ev_reasoning_item;
@@ -440,6 +443,80 @@ async fn manual_compact_emits_api_and_local_token_usage_events() {
     );
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn manual_compact_emits_context_compaction_items() {
+    skip_if_no_network!();
+
+    let server = start_mock_server().await;
+
+    let sse1 = sse(vec![
+        ev_assistant_message("m1", FIRST_REPLY),
+        ev_completed("r1"),
+    ]);
+    let sse2 = sse(vec![
+        ev_assistant_message("m2", SUMMARY_TEXT),
+        ev_completed("r2"),
+    ]);
+    mount_sse_sequence(&server, vec![sse1, sse2]).await;
+
+    let model_provider = non_openai_model_provider(&server);
+    let mut builder = test_codex().with_config(move |config| {
+        config.model_provider = model_provider;
+        set_test_compact_prompt(config);
+    });
+    let codex = builder.build(&server).await.unwrap().codex;
+
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "manual compact".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await
+        .unwrap();
+    wait_for_event(&codex, |event| matches!(event, EventMsg::TurnComplete(_))).await;
+
+    codex.submit(Op::Compact).await.unwrap();
+
+    let mut started_item = None;
+    let mut completed_item = None;
+    let mut legacy_event = false;
+    let mut saw_turn_complete = false;
+
+    while !saw_turn_complete || started_item.is_none() || completed_item.is_none() || !legacy_event
+    {
+        let event = codex.next_event().await.unwrap();
+        match event.msg {
+            EventMsg::ItemStarted(ItemStartedEvent {
+                item: TurnItem::ContextCompaction(item),
+                ..
+            }) => {
+                started_item = Some(item);
+            }
+            EventMsg::ItemCompleted(ItemCompletedEvent {
+                item: TurnItem::ContextCompaction(item),
+                ..
+            }) => {
+                completed_item = Some(item);
+            }
+            EventMsg::ContextCompacted(_) => {
+                legacy_event = true;
+            }
+            EventMsg::TurnComplete(_) => {
+                saw_turn_complete = true;
+            }
+            _ => {}
+        }
+    }
+
+    let started_item = started_item.expect("context compaction item started");
+    let completed_item = completed_item.expect("context compaction item completed");
+    assert_eq!(started_item.id, completed_item.id);
+    assert!(legacy_event);
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn multiple_auto_compact_per_task_runs_after_token_limit_hit() {
     skip_if_no_network!();
@@ -1179,6 +1256,89 @@ async fn auto_compact_runs_after_token_limit_hit() {
     );
 }
 
+// Windows CI only: bump to 4 workers to prevent SSE/event starvation and test timeouts.
+#[cfg_attr(windows, tokio::test(flavor = "multi_thread", worker_threads = 4))]
+#[cfg_attr(not(windows), tokio::test(flavor = "multi_thread", worker_threads = 2))]
+async fn auto_compact_emits_context_compaction_items() {
+    skip_if_no_network!();
+
+    let server = start_mock_server().await;
+
+    let sse1 = sse(vec![
+        ev_assistant_message("m1", FIRST_REPLY),
+        ev_completed_with_tokens("r1", 70_000),
+    ]);
+    let sse2 = sse(vec![
+        ev_assistant_message("m2", "SECOND_REPLY"),
+        ev_completed_with_tokens("r2", 330_000),
+    ]);
+    let sse3 = sse(vec![
+        ev_assistant_message("m3", AUTO_SUMMARY_TEXT),
+        ev_completed_with_tokens("r3", 200),
+    ]);
+    let sse4 = sse(vec![
+        ev_assistant_message("m4", FINAL_REPLY),
+        ev_completed_with_tokens("r4", 120),
+    ]);
+
+    mount_sse_sequence(&server, vec![sse1, sse2, sse3, sse4]).await;
+
+    let model_provider = non_openai_model_provider(&server);
+    let mut builder = test_codex().with_config(move |config| {
+        config.model_provider = model_provider;
+        set_test_compact_prompt(config);
+        config.model_auto_compact_token_limit = Some(200_000);
+    });
+    let codex = builder.build(&server).await.unwrap().codex;
+
+    let mut started_item = None;
+    let mut completed_item = None;
+    let mut legacy_event = false;
+
+    for user in [FIRST_AUTO_MSG, SECOND_AUTO_MSG, POST_AUTO_USER_MSG] {
+        codex
+            .submit(Op::UserInput {
+                items: vec![UserInput::Text {
+                    text: user.into(),
+                    text_elements: Vec::new(),
+                }],
+                final_output_json_schema: None,
+            })
+            .await
+            .unwrap();
+
+        loop {
+            let event = codex.next_event().await.unwrap();
+            match event.msg {
+                EventMsg::ItemStarted(ItemStartedEvent {
+                    item: TurnItem::ContextCompaction(item),
+                    ..
+                }) => {
+                    started_item = Some(item);
+                }
+                EventMsg::ItemCompleted(ItemCompletedEvent {
+                    item: TurnItem::ContextCompaction(item),
+                    ..
+                }) => {
+                    completed_item = Some(item);
+                }
+                EventMsg::ContextCompacted(_) => {
+                    legacy_event = true;
+                }
+                EventMsg::TurnComplete(_) if !event.id.starts_with("auto-compact-") => {
+                    break;
+                }
+                _ => {}
+            }
+        }
+    }
+
+    let started_item = started_item.expect("context compaction item started");
+    let completed_item = completed_item.expect("context compaction item completed");
+    assert_eq!(started_item.id, completed_item.id);
+    assert!(legacy_event);
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn auto_compact_runs_after_resume_when_token_usage_is_over_limit() {
     skip_if_no_network!();

codex-rs/core/tests/suite/compact_remote.rs

@@ -6,9 +6,12 @@ use anyhow::Result;
 use codex_core::CodexAuth;
 use codex_core::features::Feature;
 use codex_core::protocol::EventMsg;
+use codex_core::protocol::ItemCompletedEvent;
+use codex_core::protocol::ItemStartedEvent;
 use codex_core::protocol::Op;
 use codex_core::protocol::RolloutItem;
 use codex_core::protocol::RolloutLine;
+use codex_protocol::items::TurnItem;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseItem;
 use codex_protocol::user_input::UserInput;
@@ -201,13 +204,13 @@ async fn remote_compact_runs_automatically() -> Result<()> {
             final_output_json_schema: None,
         })
         .await?;
-    let message = wait_for_event_match(&codex, |ev| match ev {
+
+    let message = wait_for_event_match(&codex, |event| match event {
         EventMsg::ContextCompacted(_) => Some(true),
         _ => None,
     })
     .await;
-    wait_for_event(&codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
-
+    wait_for_event(&codex, |event| matches!(event, EventMsg::TurnComplete(_))).await;
     assert!(message);
     assert_eq!(compact_mock.requests().len(), 1);
     let follow_up_body = responses_mock.single_request().body_json().to_string();
@@ -217,6 +220,101 @@ async fn remote_compact_runs_automatically() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn remote_manual_compact_emits_context_compaction_items() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let harness = TestCodexHarness::with_builder(
+        test_codex()
+            .with_auth(CodexAuth::create_dummy_chatgpt_auth_for_testing())
+            .with_config(|config| {
+                config.features.enable(Feature::RemoteCompaction);
+            }),
+    )
+    .await?;
+    let codex = harness.test().codex.clone();
+
+    mount_sse_once(
+        harness.server(),
+        sse(vec![
+            responses::ev_assistant_message("m1", "REMOTE_REPLY"),
+            responses::ev_completed("resp-1"),
+        ]),
+    )
+    .await;
+
+    let compacted_history = vec![
+        ResponseItem::Message {
+            id: None,
+            role: "user".to_string(),
+            content: vec![ContentItem::InputText {
+                text: "REMOTE_COMPACTED_SUMMARY".to_string(),
+            }],
+            end_turn: None,
+        },
+        ResponseItem::Compaction {
+            encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
+        },
+    ];
+    let compact_mock = responses::mount_compact_json_once(
+        harness.server(),
+        serde_json::json!({ "output": compacted_history.clone() }),
+    )
+    .await;
+
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "manual remote compact".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await?;
+    wait_for_event(&codex, |event| matches!(event, EventMsg::TurnComplete(_))).await;
+
+    codex.submit(Op::Compact).await?;
+
+    let mut started_item = None;
+    let mut completed_item = None;
+    let mut legacy_event = false;
+    let mut saw_turn_complete = false;
+
+    while !saw_turn_complete || started_item.is_none() || completed_item.is_none() || !legacy_event
+    {
+        let event = codex.next_event().await.unwrap();
+        match event.msg {
+            EventMsg::ItemStarted(ItemStartedEvent {
+                item: TurnItem::ContextCompaction(item),
+                ..
+            }) => {
+                started_item = Some(item);
+            }
+            EventMsg::ItemCompleted(ItemCompletedEvent {
+                item: TurnItem::ContextCompaction(item),
+                ..
+            }) => {
+                completed_item = Some(item);
+            }
+            EventMsg::ContextCompacted(_) => {
+                legacy_event = true;
+            }
+            EventMsg::TurnComplete(_) => {
+                saw_turn_complete = true;
+            }
+            _ => {}
+        }
+    }
+
+    let started_item = started_item.expect("context compaction item started");
+    let completed_item = completed_item.expect("context compaction item completed");
+    assert_eq!(started_item.id, completed_item.id);
+    assert!(legacy_event);
+    assert_eq!(compact_mock.requests().len(), 1);
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn remote_compact_persists_replacement_history_in_rollout() -> Result<()> {
     skip_if_no_network!(Ok(()));

codex-rs/protocol/src/items.rs

@@ -2,6 +2,7 @@ use crate::models::WebSearchAction;
 use crate::protocol::AgentMessageEvent;
 use crate::protocol::AgentReasoningEvent;
 use crate::protocol::AgentReasoningRawContentEvent;
+use crate::protocol::ContextCompactedEvent;
 use crate::protocol::EventMsg;
 use crate::protocol::UserMessageEvent;
 use crate::protocol::WebSearchEndEvent;
@@ -21,6 +22,7 @@ pub enum TurnItem {
     AgentMessage(AgentMessageItem),
     Reasoning(ReasoningItem),
     WebSearch(WebSearchItem),
+    ContextCompaction(ContextCompactionItem),
 }
 
 #[derive(Debug, Clone, Deserialize, Serialize, TS, JsonSchema)]
@@ -57,6 +59,29 @@ pub struct WebSearchItem {
     pub action: WebSearchAction,
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize, TS, JsonSchema)]
+pub struct ContextCompactionItem {
+    pub id: String,
+}
+
+impl ContextCompactionItem {
+    pub fn new() -> Self {
+        Self {
+            id: uuid::Uuid::new_v4().to_string(),
+        }
+    }
+
+    pub fn as_legacy_event(&self) -> EventMsg {
+        EventMsg::ContextCompacted(ContextCompactedEvent {})
+    }
+}
+
+impl Default for ContextCompactionItem {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl UserMessageItem {
     pub fn new(content: &[UserInput]) -> Self {
         Self {
@@ -195,6 +220,7 @@ impl TurnItem {
             TurnItem::AgentMessage(item) => item.id.clone(),
             TurnItem::Reasoning(item) => item.id.clone(),
             TurnItem::WebSearch(item) => item.id.clone(),
+            TurnItem::ContextCompaction(item) => item.id.clone(),
         }
     }
 
@@ -204,6 +230,7 @@ impl TurnItem {
             TurnItem::AgentMessage(item) => item.as_legacy_events(),
             TurnItem::WebSearch(item) => vec![item.as_legacy_event()],
             TurnItem::Reasoning(item) => item.as_legacy_events(show_raw_agent_reasoning),
+            TurnItem::ContextCompaction(item) => vec![item.as_legacy_event()],
         }
     }
 }