From c52d25d5765bf232add60ab23898f941ccb7d76c Mon Sep 17 00:00:00 2001
From: Chris Tate <chris@ctate.dev>
Date: Sat, 4 Apr 2026 10:25:12 -0500
Subject: [PATCH] Fix HAR capture missing API requests under heavy traffic
 (#1135)

The CDP event broadcast buffer (256 events) was too small for pages with
many concurrent API requests, causing silent event drops. Modern SPAs
routinely fire 100+ API calls during page load, generating 300+ CDP
network events that would overflow the buffer between drain cycles.

Changes:
- Increase CDP broadcast buffer from 256 to 4096 (event channel) and
  512 to 4096 (raw channel)
- Reduce background drain interval from 500ms to 100ms
- Handle Network.loadingFailed events in HAR recording
- Enable Network.enable on cross-origin iframe sessions during HAR
  recording and request tracking
- Allow Network events from iframe sessions through the session filter
- Log a warning when buffer overflow occurs instead of silently dropping

Fixes #1128

Co-authored-by: ctate <366502+ctate@users.noreply.github.com>
---
 cli/src/native/actions.rs    | 58 ++++++++++++++++++++++++++++++++++--
 cli/src/native/cdp/client.rs |  4 +--
 cli/src/native/daemon.rs     |  2 +-
 3 files changed, 59 insertions(+), 5 deletions(-)

diff --git a/cli/src/native/actions.rs b/cli/src/native/actions.rs
index b2070a3..c8f154d 100644
--- a/cli/src/native/actions.rs
+++ b/cli/src/native/actions.rs
@@ -562,6 +562,12 @@ impl DaemonState {
                     .client
                     .send_command_no_params("Accessibility.enable", Some(iframe_sid.as_str()))
                     .await;
+                if self.har_recording || self.request_tracking {
+                    let _ = mgr
+                        .client
+                        .send_command_no_params("Network.enable", Some(iframe_sid.as_str()))
+                        .await;
+                }
             }
         }
         for sid in &drained.detached_iframe_sessions {
@@ -727,7 +733,17 @@ impl DaemonState {
                         false
                     };
 
-                    if !session_matches {
+                    // Allow Network events from cross-origin iframe sessions
+                    // when HAR recording or request tracking is active.
+                    let iframe_network_event = !session_matches
+                        && (self.har_recording || self.request_tracking)
+                        && event.method.starts_with("Network.")
+                        && event
+                            .session_id
+                            .as_ref()
+                            .is_some_and(|sid| self.iframe_sessions.values().any(|v| v == sid));
+
+                    if !session_matches && !iframe_network_event {
                         continue;
                     }
 
@@ -963,6 +979,33 @@ impl DaemonState {
                                 }
                             }
                         }
+                        "Network.loadingFailed" if self.har_recording => {
+                            let request_id = event
+                                .params
+                                .get("requestId")
+                                .and_then(|v| v.as_str())
+                                .unwrap_or("");
+                            let timestamp = event.params.get("timestamp").and_then(|v| v.as_f64());
+                            let error_text = event
+                                .params
+                                .get("errorText")
+                                .and_then(|v| v.as_str())
+                                .unwrap_or("Failed");
+                            if let Some(entry) = self
+                                .har_entries
+                                .iter_mut()
+                                .rev()
+                                .find(|e| e.request_id == request_id)
+                            {
+                                if entry.status.is_none() {
+                                    entry.status = Some(0);
+                                    entry.status_text = error_text.to_string();
+                                }
+                                if let Some(ts) = timestamp {
+                                    entry.loading_finished_timestamp = Some(ts);
+                                }
+                            }
+                        }
                         "Page.screencastFrame" => {
                             // Frame broadcasting and acks are handled in real-time by the
                             // stream server's background CDP event loop. Here we just
@@ -1008,7 +1051,10 @@ impl DaemonState {
                     }
                 }
                 Err(broadcast::error::TryRecvError::Empty) => break,
-                Err(broadcast::error::TryRecvError::Lagged(_)) => continue,
+                Err(broadcast::error::TryRecvError::Lagged(n)) => {
+                    eprintln!("[agent-browser] Warning: CDP event buffer overflowed, {} events dropped. Network requests may be missing from HAR output.", n);
+                    continue;
+                }
                 Err(broadcast::error::TryRecvError::Closed) => {
                     self.event_rx = None;
                     break;
@@ -5854,6 +5900,14 @@ async fn handle_har_start(state: &mut DaemonState) -> Result<Value, String> {
     mgr.client
         .send_command_no_params("Network.enable", Some(&session_id))
         .await?;
+    // Also enable Network on cross-origin iframe sessions so their
+    // requests are captured in the HAR output.
+    for iframe_sid in state.iframe_sessions.values() {
+        let _ = mgr
+            .client
+            .send_command_no_params("Network.enable", Some(iframe_sid.as_str()))
+            .await;
+    }
     state.har_recording = true;
     state.har_entries.clear();
     Ok(json!({ "started": true }))
diff --git a/cli/src/native/cdp/client.rs b/cli/src/native/cdp/client.rs
index 621973a..45e0a51 100644
--- a/cli/src/native/cdp/client.rs
+++ b/cli/src/native/cdp/client.rs
@@ -87,8 +87,8 @@ impl CdpClient {
         let ws_tx = Arc::new(Mutex::new(ws_tx));
 
         let pending: PendingMap = Arc::new(Mutex::new(HashMap::new()));
-        let (event_tx, _) = broadcast::channel(256);
-        let (raw_tx, _) = broadcast::channel(512);
+        let (event_tx, _) = broadcast::channel(4096);
+        let (raw_tx, _) = broadcast::channel(4096);
 
         let pending_clone = pending.clone();
         let event_tx_clone = event_tx.clone();
diff --git a/cli/src/native/daemon.rs b/cli/src/native/daemon.rs
index 90a78a1..2aabed0 100644
--- a/cli/src/native/daemon.rs
+++ b/cli/src/native/daemon.rs
@@ -156,7 +156,7 @@ async fn run_socket_server(
     let (reset_tx, mut reset_rx) = mpsc::channel::<()>(64);
     let reset_tx = idle_timeout_ms.map(|_| Arc::new(reset_tx));
 
-    let mut drain_interval = tokio::time::interval(Duration::from_millis(500));
+    let mut drain_interval = tokio::time::interval(Duration::from_millis(100));
     drain_interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);
 
     loop {