fix: don't truncate at new lines (#6907)

codex-rs/core/src/truncate.rs

@@ -282,22 +282,11 @@ fn truncate_on_boundary(input: &str, max_len: usize) -> &str {
 }
 
 fn pick_prefix_end(s: &str, left_budget: usize) -> usize {
-    if let Some(head) = s.get(..left_budget)
-        && let Some(i) = head.rfind('\n')
-    {
-        return i + 1;
-    }
     truncate_on_boundary(s, left_budget).len()
 }
 
 fn pick_suffix_start(s: &str, right_budget: usize) -> usize {
     let start_tail = s.len().saturating_sub(right_budget);
-    if let Some(tail) = s.get(start_tail..)
-        && let Some(i) = tail.find('\n')
-    {
-        return start_tail + i + 1;
-    }
-
     let mut idx = start_tail.min(s.len());
     while idx < s.len() && !s.is_char_boundary(idx) {
         idx += 1;
@@ -420,7 +409,7 @@ mod tests {
     fn truncate_middle_tokens_handles_utf8_content() {
         let s = "😀😀😀😀😀😀😀😀😀😀\nsecond line with text\n";
         let (out, tokens) = truncate_with_token_budget(s, TruncationPolicy::Tokens(8));
-        assert_eq!(out, "😀😀😀😀…8 tokens truncated…");
+        assert_eq!(out, "😀😀😀😀…8 tokens truncated… line with text\n");
         assert_eq!(tokens, Some(16));
     }
 
@@ -428,7 +417,7 @@ mod tests {
     fn truncate_middle_bytes_handles_utf8_content() {
         let s = "😀😀😀😀😀😀😀😀😀😀\nsecond line with text\n";
         let out = truncate_text(s, TruncationPolicy::Bytes(20));
-        assert_eq!(out, "😀😀…31 chars truncated…");
+        assert_eq!(out, "😀😀…21 chars truncated…with text\n");
     }
 
     #[test]