From 706ba0ab25b67015e873440115011f385f3bf935 Mon Sep 17 00:00:00 2001
From: Charles Cunningham <ccunningham@openai.com>
Date: Sun, 8 Feb 2026 15:23:30 -0800
Subject: [PATCH] core: share model-visible byte estimator for history metrics

---
 codex-rs/core/src/context_manager/history.rs | 27 ++++++++++----------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/codex-rs/core/src/context_manager/history.rs b/codex-rs/core/src/context_manager/history.rs
index 7de0cf9101..53a364282f 100644
--- a/codex-rs/core/src/context_manager/history.rs
+++ b/codex-rs/core/src/context_manager/history.rs
@@ -269,11 +269,7 @@ impl ContextManager {
         self.items_after_last_model_generated_item()
             .iter()
             .fold(0usize, |acc, item| {
-                acc.saturating_add(
-                    serde_json::to_vec(item)
-                        .map(|bytes| bytes.len())
-                        .unwrap_or_default(),
-                )
+                acc.saturating_add(estimate_item_model_visible_bytes(item))
             })
     }
 
@@ -401,7 +397,11 @@ fn estimate_reasoning_length(encoded_len: usize) -> usize {
         .saturating_sub(650)
 }
 
-fn estimate_item_token_count(item: &ResponseItem) -> i64 {
+fn model_visible_text(item: &ResponseItem) -> String {
+    serde_json::to_string(item).unwrap_or_default()
+}
+
+fn estimate_item_model_visible_bytes(item: &ResponseItem) -> usize {
     match item {
         ResponseItem::GhostSnapshot { .. } => 0,
         ResponseItem::Reasoning {
@@ -410,17 +410,16 @@ fn estimate_item_token_count(item: &ResponseItem) -> i64 {
         }
         | ResponseItem::Compaction {
             encrypted_content: content,
-        } => {
-            let reasoning_bytes = estimate_reasoning_length(content.len());
-            i64::try_from(approx_tokens_from_byte_count(reasoning_bytes)).unwrap_or(i64::MAX)
-        }
-        item => {
-            let serialized = serde_json::to_string(item).unwrap_or_default();
-            i64::try_from(approx_token_count(&serialized)).unwrap_or(i64::MAX)
-        }
+        } => estimate_reasoning_length(content.len()),
+        item => model_visible_text(item).len(),
     }
 }
 
+fn estimate_item_token_count(item: &ResponseItem) -> i64 {
+    let bytes = estimate_item_model_visible_bytes(item);
+    i64::try_from(approx_tokens_from_byte_count(bytes)).unwrap_or(i64::MAX)
+}
+
 fn is_model_generated_item(item: &ResponseItem) -> bool {
     match item {
         ResponseItem::Message { role, .. } => role == "assistant",