diff --git a/codex-rs/core/src/context_manager/history.rs b/codex-rs/core/src/context_manager/history.rs
index 035d0d286..7277f0b0c 100644
--- a/codex-rs/core/src/context_manager/history.rs
+++ b/codex-rs/core/src/context_manager/history.rs
@@ -84,9 +84,19 @@ impl ContextManager {
                 .unwrap_or(i64::MAX);
 
         let items_tokens = self.items.iter().fold(0i64, |acc, item| {
-            let serialized = serde_json::to_string(item).unwrap_or_default();
-            let item_tokens = i64::try_from(approx_token_count(&serialized)).unwrap_or(i64::MAX);
-            acc.saturating_add(item_tokens)
+            acc + match item {
+                ResponseItem::Reasoning {
+                    encrypted_content: Some(content),
+                    ..
+                }
+                | ResponseItem::CompactionSummary {
+                    encrypted_content: content,
+                } => estimate_reasoning_length(content.len()) as i64,
+                item => {
+                    let serialized = serde_json::to_string(item).unwrap_or_default();
+                    i64::try_from(approx_token_count(&serialized)).unwrap_or(i64::MAX)
+                }
+            }
         });
 
         Some(base_tokens.saturating_add(items_tokens))
@@ -145,21 +155,13 @@ impl ContextManager {
                     None
                 }
             })
-            .map(Self::estimate_reasoning_length)
+            .map(estimate_reasoning_length)
             .fold(0usize, usize::saturating_add);
 
         let token_estimate = approx_tokens_from_byte_count(total_reasoning_bytes);
         token_estimate as usize
     }
 
-    fn estimate_reasoning_length(encoded_len: usize) -> usize {
-        encoded_len
-            .saturating_mul(3)
-            .checked_div(4)
-            .unwrap_or(0)
-            .saturating_sub(650)
-    }
-
     pub(crate) fn get_total_token_usage(&self) -> i64 {
         self.token_info
             .as_ref()
@@ -247,6 +249,14 @@ fn is_api_message(message: &ResponseItem) -> bool {
     }
 }
 
+fn estimate_reasoning_length(encoded_len: usize) -> usize {
+    encoded_len
+        .saturating_mul(3)
+        .checked_div(4)
+        .unwrap_or(0)
+        .saturating_sub(650)
+}
+
 #[cfg(test)]
 #[path = "history_tests.rs"]
 mod tests;