diff --git a/server/src/llm/providers/claude_code.rs b/server/src/llm/providers/claude_code.rs
index 7bc5493..c075c92 100644
--- a/server/src/llm/providers/claude_code.rs
+++ b/server/src/llm/providers/claude_code.rs
@@ -246,10 +246,11 @@ fn run_pty_session(
                     continue;
                 }
 
-                slog!(
-                    "[pty-debug] processing: {}...",
-                    &trimmed[..trimmed.len().min(120)]
-                );
+                let mut end = trimmed.len().min(120);
+                while !trimmed.is_char_boundary(end) {
+                    end -= 1;
+                }
+                slog!("[pty-debug] processing: {}...", &trimmed[..end]);
 
                 // Try to parse as JSON
                 if let Ok(json) = serde_json::from_str::<serde_json::Value>(trimmed)