diff --git a/codex-rs/core/src/context_manager/history.rs b/codex-rs/core/src/context_manager/history.rs
index f990a80dce..17e7e33c7d 100644
--- a/codex-rs/core/src/context_manager/history.rs
+++ b/codex-rs/core/src/context_manager/history.rs
@@ -333,7 +333,8 @@ impl ContextManager {
     /// This function enforces a couple of invariants on the in-memory history:
     /// 1. every call (function/custom) has a corresponding output entry
     /// 2. every output has a corresponding call entry
-    /// 3. when images are unsupported, image content is stripped from messages and tool outputs
+    /// 3. trailing reasoning items are dropped before the next user message and at prompt end
+    /// 4. when images are unsupported, image content is stripped from messages and tool outputs
     fn normalize_history(&mut self, input_modalities: &[InputModality]) {
         // all function/tool calls must have a corresponding output
         normalize::ensure_call_outputs_present(&mut self.items);
@@ -341,6 +342,9 @@ impl ContextManager {
         // all outputs must have a corresponding function/tool call
         normalize::remove_orphan_outputs(&mut self.items);
 
+        // interrupted turns can leave replay-unsafe trailing reasoning before the next user item
+        normalize::remove_trailing_reasoning_before_user_messages(&mut self.items);
+
         // strip images when model does not support them
         normalize::strip_images_when_unsupported(input_modalities, &mut self.items);
     }
diff --git a/codex-rs/core/src/context_manager/history_tests.rs b/codex-rs/core/src/context_manager/history_tests.rs
index 71b3aded0c..b6bb257bbe 100644
--- a/codex-rs/core/src/context_manager/history_tests.rs
+++ b/codex-rs/core/src/context_manager/history_tests.rs
@@ -442,6 +442,59 @@ fn for_prompt_preserves_image_generation_calls_when_images_are_supported() {
     );
 }
 
+#[test]
+fn for_prompt_drops_trailing_reasoning_before_next_user_message() {
+    let history = create_history_with_items(vec![
+        user_input_text_msg("first"),
+        assistant_msg("done"),
+        reasoning_msg("orphaned"),
+        user_input_text_msg("second"),
+    ]);
+
+    assert_eq!(
+        history.for_prompt(&default_input_modalities()),
+        vec![
+            user_input_text_msg("first"),
+            assistant_msg("done"),
+            user_input_text_msg("second"),
+        ]
+    );
+}
+
+#[test]
+fn for_prompt_drops_trailing_reasoning_at_prompt_end() {
+    let history = create_history_with_items(vec![
+        user_input_text_msg("first"),
+        assistant_msg("done"),
+        reasoning_msg("orphaned"),
+    ]);
+
+    assert_eq!(
+        history.for_prompt(&default_input_modalities()),
+        vec![user_input_text_msg("first"), assistant_msg("done"),]
+    );
+}
+
+#[test]
+fn for_prompt_keeps_reasoning_when_followed_by_assistant_message() {
+    let history = create_history_with_items(vec![
+        user_input_text_msg("first"),
+        reasoning_msg("kept"),
+        assistant_msg("done"),
+        user_input_text_msg("second"),
+    ]);
+
+    assert_eq!(
+        history.for_prompt(&default_input_modalities()),
+        vec![
+            user_input_text_msg("first"),
+            reasoning_msg("kept"),
+            assistant_msg("done"),
+            user_input_text_msg("second"),
+        ]
+    );
+}
+
 #[test]
 fn for_prompt_clears_image_generation_result_when_images_are_unsupported() {
     let history = create_history_with_items(vec![
diff --git a/codex-rs/core/src/context_manager/normalize.rs b/codex-rs/core/src/context_manager/normalize.rs
index 839bae331e..5bb67f5b5d 100644
--- a/codex-rs/core/src/context_manager/normalize.rs
+++ b/codex-rs/core/src/context_manager/normalize.rs
@@ -194,6 +194,33 @@ pub(crate) fn remove_orphan_outputs(items: &mut Vec<ResponseItem>) {
     });
 }
 
+pub(crate) fn remove_trailing_reasoning_before_user_messages(items: &mut Vec<ResponseItem>) {
+    let mut normalized = Vec::with_capacity(items.len());
+    let mut removed_count = 0usize;
+
+    for item in items.drain(..) {
+        if matches!(&item, ResponseItem::Message { role, .. } if role == "user") {
+            while matches!(normalized.last(), Some(ResponseItem::Reasoning { .. })) {
+                normalized.pop();
+                removed_count += 1;
+            }
+        }
+
+        normalized.push(item);
+    }
+
+    while matches!(normalized.last(), Some(ResponseItem::Reasoning { .. })) {
+        normalized.pop();
+        removed_count += 1;
+    }
+
+    if removed_count > 0 {
+        info!("Removed {removed_count} trailing reasoning item(s) before user input or prompt end");
+    }
+
+    *items = normalized;
+}
+
 pub(crate) fn remove_corresponding_for(items: &mut Vec<ResponseItem>, item: &ResponseItem) {
     match item {
         ResponseItem::FunctionCall { call_id, .. } => {