diff --git a/poc-memory/src/transcript.rs b/poc-memory/src/transcript.rs
index beaf08a..3919050 100644
--- a/poc-memory/src/transcript.rs
+++ b/poc-memory/src/transcript.rs
@@ -203,11 +203,12 @@ impl Iterator for TailMessages {
 
             let obj_bytes = &self.mmap[open..=close];
 
-            // Quick byte check: skip objects that aren't user/assistant
-            // messages. Avoids serde-parsing megabyte tool_result objects.
-            let is_user = memchr::memmem::find(obj_bytes, b"\"type\":\"user\"").is_some();
+            // The "type" field is near the start of top-level objects.
+            // Only check the first 200 bytes to avoid scanning megabyte objects.
+            let prefix = &obj_bytes[..obj_bytes.len().min(200)];
+            let is_user = memchr::memmem::find(prefix, b"\"type\":\"user\"").is_some();
             let is_assistant = !is_user
-                && memchr::memmem::find(obj_bytes, b"\"type\":\"assistant\"").is_some();
+                && memchr::memmem::find(prefix, b"\"type\":\"assistant\"").is_some();
             if !is_user && !is_assistant { continue; }
 
             let obj: Value = match serde_json::from_slice(obj_bytes) {