Fix benchmark regression

Cargo.toml

@@ -38,6 +38,7 @@ ignore = "0.4"
 rand = "0.9"
 iana-time-zone = "0.1"
 image = { version = "0.25", default-features = false, features = ["png", "jpeg", "gif", "webp"] }
+libc = "0.2"
 ratatui = { version = "0.30", default-features = false, features = ["crossterm_0_29"] }
 reqwest = { version = "0.12", default-features = false, features = ["blocking", "json", "rustls-tls"] }
 regex = "1"

crates/browser-use-agent/Cargo.toml

@@ -26,6 +26,7 @@ rand.workspace = true
 regex.workspace = true
 reqwest = { workspace = true, features = ["stream"] }
 rustls.workspace = true
+libc.workspace = true
 serde.workspace = true
 serde_json.workspace = true
 sha2.workspace = true

crates/browser-use-agent/src/compact/mod.rs

@@ -302,7 +302,18 @@ pub fn compacted_history_from_summary(
     summary_suffix: CompactionSummary,
     token_limit: usize,
 ) -> CompactedHistory {
-    let summary_text = format!("{SUMMARY_PREFIX}\n{}", summary_suffix.text);
+    // The empty-summary fallback must apply to the SUFFIX, before the prefix
+    // is prepended — otherwise the prefix makes the combined string non-empty
+    // and the fallback in build_compacted_history never fires. A summarize()
+    // pass that returns no text then ships "...Here is the summary...:" followed
+    // by NOTHING, leaving the post-compaction model with total amnesia (real_v8
+    // task 24: 30 thrash turns, task lost).
+    let suffix_text = if summary_suffix.text.trim().is_empty() {
+        "(no summary available)".to_string()
+    } else {
+        summary_suffix.text.clone()
+    };
+    let summary_text = format!("{SUMMARY_PREFIX}\n{suffix_text}");
     let user_messages: Vec<String> = history.iter().filter_map(real_user_message_text).collect();
     let items = build_compacted_history(&user_messages, &summary_text, token_limit);
 

crates/browser-use-agent/src/compact/tests.rs

@@ -370,11 +370,11 @@ async fn context_window_exceeded_with_only_prompt_left_propagates() {
 }
 
 #[tokio::test]
-async fn empty_model_summary_yields_prefix_only_summary() {
-    // The model returns an empty summary => summary_text = PREFIX + "\n" + "".
-    // (The "(no summary available)" placeholder only applies when the WHOLE
-    // summary_text is empty, which it never is here because the prefix is present;
-    // codex compact.rs:516.)
+async fn empty_model_summary_yields_no_summary_available_fallback() {
+    // The model returns an empty summary => the SUFFIX falls back to
+    // "(no summary available)" BEFORE the prefix is prepended (codex
+    // compact.rs:516). Shipping PREFIX+"" gave the post-compaction model
+    // total amnesia (real_v8 task 24).
     let history = vec![user_item("a user message")];
     let sampler = ScriptedSampler::new(vec![Ok(String::new())]);
 
@@ -390,7 +390,10 @@ async fn empty_model_summary_yields_prefix_only_summary() {
 
     let last = item_text(compacted.items.last().unwrap());
     assert_eq!(last, compacted.summary_text);
-    assert_eq!(compacted.summary_text, format!("{SUMMARY_PREFIX}\n"));
+    assert_eq!(
+        compacted.summary_text,
+        format!("{SUMMARY_PREFIX}\n(no summary available)")
+    );
 }
 
 // ---- (5) end-to-end through the real TurnLoop -----------------------------