compact: preserve incoming items during pre-turn trim retries

codex-rs/core/src/codex.rs

@@ -3406,10 +3406,10 @@ mod handlers {
         // Attempt to inject input into current task.
         if let Err(SteerInputError::NoActiveTurn(items)) = sess.steer_input(items, None).await {
             sess.seed_initial_context_if_needed(&current_context).await;
-            let resumed_model = sess.take_pending_resume_previous_model().await;
+            let previous_model = sess.previous_model().await;
             let pre_turn_context_items = sess.build_settings_update_items(
                 previous_context.as_ref(),
-                resumed_model.as_deref(),
+                previous_model.as_deref(),
                 &current_context,
             );
             let has_user_input = !items.is_empty();

codex-rs/core/src/compact.rs

@@ -167,6 +167,12 @@ async fn run_compact_task_inner(
         &[initial_input_for_turn.into()],
         turn_context.truncation_policy,
     );
+    // Keep incoming turn items and the compaction prompt pinned at the tail while trimming.
+    // Pre-turn compaction should fail with ContextWindowExceeded rather than dropping incoming
+    // items to force compaction to succeed.
+    let protected_tail_items = incoming_items
+        .as_ref()
+        .map_or(1_usize, |items| items.len().saturating_add(1));
 
     let mut truncated_count = 0usize;
 
@@ -224,7 +230,7 @@ async fn run_compact_task_inner(
                 return Err(CodexErr::Interrupted);
             }
             Err(e @ CodexErr::ContextWindowExceeded) => {
-                if turn_input_len > 1 {
+                if turn_input_len > 1 && history.raw_items().len() > protected_tail_items {
                     // Trim from the beginning to preserve cache (prefix-based) and keep recent
                     // messages intact.
                     error!(

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

@@ -3235,9 +3235,9 @@ async fn snapshot_request_shape_pre_turn_compaction_context_window_exceeded() {
     insta::assert_snapshot!(
         "pre_turn_compaction_context_window_exceeded_shapes",
         format_labeled_requests_snapshot(
-            "Pre-turn auto-compaction context-window failure: compaction request excludes the incoming user message and the turn errors.",
+            "Pre-turn auto-compaction context-window failure: compaction request includes the incoming user message and the turn errors.",
             &[(
-                "Local Compaction Request (Incoming User Excluded)",
+                "Local Compaction Request (Incoming User Included)",
                 &requests[1]
             ),]
         )
@@ -3249,6 +3249,87 @@ async fn snapshot_request_shape_pre_turn_compaction_context_window_exceeded() {
     );
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn pre_turn_local_compaction_trim_retries_keep_incoming_items() {
+    skip_if_no_network!();
+
+    let server = start_mock_server().await;
+    let compact_failed = sse_failed(
+        "compact-failed",
+        "context_length_exceeded",
+        CONTEXT_LIMIT_MESSAGE,
+    );
+    let request_log = mount_sse_sequence(
+        &server,
+        vec![
+            compact_failed.clone(),
+            compact_failed.clone(),
+            compact_failed.clone(),
+            compact_failed,
+        ],
+    )
+    .await;
+
+    let model_provider = non_openai_model_provider(&server);
+    let codex = test_codex()
+        .with_config(move |config| {
+            config.model_provider = model_provider;
+            set_test_compact_prompt(config);
+            config.model_auto_compact_token_limit = Some(1);
+        })
+        .build(&server)
+        .await
+        .expect("build codex")
+        .codex;
+
+    let incoming_text = "PRETURN_INCOMING_USER";
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: incoming_text.to_string(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await
+        .expect("submit user input");
+
+    let error_message = wait_for_event_match(&codex, |event| match event {
+        EventMsg::Error(err) => Some(err.message.clone()),
+        _ => None,
+    })
+    .await;
+    wait_for_event(&codex, |ev| matches!(ev, EventMsg::TurnComplete(_))).await;
+
+    assert!(
+        error_message.contains(
+            "Incoming user message and/or turn context is too large to fit in context window"
+        ),
+        "expected oversized incoming-items error, got {error_message}"
+    );
+
+    let compact_attempts = request_log.requests();
+    assert_eq!(
+        compact_attempts.len(),
+        4,
+        "expected pre-turn compaction to retry while trimming seeded history only"
+    );
+    for (index, request) in compact_attempts.iter().enumerate() {
+        let body = request.body_json().to_string();
+        assert!(
+            body_contains_text(&body, SUMMARIZATION_PROMPT),
+            "request {index} should be a compaction attempt"
+        );
+        assert!(
+            request
+                .message_input_texts("user")
+                .iter()
+                .any(|text| text == incoming_text),
+            "request {index} dropped incoming user text during trim retries"
+        );
+    }
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn snapshot_request_shape_manual_compact_without_previous_user_messages() {
     skip_if_no_network!();

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

@@ -139,7 +139,7 @@ async fn settings_only_empty_turn_persists_updates_for_next_non_empty_turn() ->
             final_output_json_schema: None,
             cwd: test.cwd_path().to_path_buf(),
             approval_policy: AskForApproval::Never,
-            sandbox_policy: SandboxPolicy::ReadOnly,
+            sandbox_policy: SandboxPolicy::new_read_only_policy(),
             model: model.clone(),
             effort: test.config.model_reasoning_effort,
             summary: ReasoningSummary::Auto,

codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_context_window_exceeded_shapes.snap

@@ -1,13 +1,14 @@
 ---
 source: core/tests/suite/compact.rs
-expression: "format_labeled_requests_snapshot(\"Pre-turn auto-compaction context-window failure: compaction request excludes the incoming user message and the turn errors.\",\n&[(\"Local Compaction Request (Incoming User Excluded)\", &requests[1]),])"
+expression: "format_labeled_requests_snapshot(\"Pre-turn auto-compaction context-window failure: compaction request includes the incoming user message and the turn errors.\",\n&[(\"Local Compaction Request (Incoming User Included)\", &requests[1]),])"
 ---
-Scenario: Pre-turn auto-compaction context-window failure: compaction request excludes the incoming user message and the turn errors.
+Scenario: Pre-turn auto-compaction context-window failure: compaction request includes the incoming user message and the turn errors.
 
-## Local Compaction Request (Incoming User Excluded)
+## Local Compaction Request (Incoming User Included)
 00:message/developer:<PERMISSIONS_INSTRUCTIONS>
 01:message/user:<AGENTS_MD>
 02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
 03:message/user:USER_ONE
 04:message/assistant:FIRST_REPLY
-05:message/user:<SUMMARIZATION_PROMPT>
+05:message/user:USER_TWO
+06:message/user:<SUMMARIZATION_PROMPT>