From debe29a6dcad660efd9af9ca387d99ee841a0537 Mon Sep 17 00:00:00 2001
From: Rodrigo Rodriguez <rodriguez@pragmatismo.com.br>
Date: Thu, 30 Apr 2026 16:45:37 -0300
Subject: [PATCH] fix: start.bas redundant execution with atomic SET NX guard

---
 botserver/src/core/bot/mod.rs | 45 ++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/botserver/src/core/bot/mod.rs b/botserver/src/core/bot/mod.rs
index f129f3dd..00011f57 100644
--- a/botserver/src/core/bot/mod.rs
+++ b/botserver/src/core/bot/mod.rs
@@ -772,23 +772,37 @@ let system_prompt = if !message.active_switchers.is_empty() {
         {
             // Execute start.bas on first message only (use Redis flag to prevent re-execution)
             let actual_session_id = session.id.to_string();
+            let start_bas_flag_key = format!("start_bas_executed:{}", actual_session_id);
 
             // Check Redis flag - only execute start.bas once per session
+            // We use SET NX to atomically check and set the flag
             let should_execute_start_bas = if let Some(cache) = &self.state.cache {
                 if let Ok(mut conn) = cache.get_multiplexed_async_connection().await {
-                    let key = format!("start_bas_executed:{}", actual_session_id);
-                    let already_executed: Option<String> = redis::cmd("GET")
-                        .arg(&key)
+                    let was_set: Option<String> = redis::cmd("SET")
+                        .arg(&start_bas_flag_key)
+                        .arg("1")
+                        .arg("NX")
+                        .arg("EX")
+                        .arg(86400) // 24h TTL
                         .query_async(&mut conn)
                         .await
-                        .ok()
-                        .flatten();
-                    already_executed.is_none()
+                        .ok();
+                    
+                    // If SET NX returned "OK" (Some("OK")), it means it was the first time
+                    // If it returned nil (None), it means it was already set
+                    let is_first_time = was_set.is_some();
+                    
+                    if !is_first_time {
+                        trace!("start.bas already executed for session {}, skipping in stream_response", actual_session_id);
+                    }
+                    is_first_time
                 } else {
-                    true // No cache connection, execute as fallback
+                    warn!("Failed to get Redis connection for start.bas guard, skipping to avoid redundant execution");
+                    false 
                 }
             } else {
-                true // No cache configured, execute as fallback
+                trace!("No cache configured, skipping start.bas guard in stream_response");
+                false
             };
 
         if should_execute_start_bas {
@@ -845,20 +859,7 @@ let system_prompt = if !message.active_switchers.is_empty() {
 
             match result {
                 Ok(Ok(())) => {
-                    trace!("start.bas completed successfully for session {}", actual_session_id);
-                    // Set Redis flag so start.bas does not run again for this session
-                    if let Some(cache) = &self.state.cache {
-                        if let Ok(mut conn) = cache.get_multiplexed_async_connection().await {
-                            let key = format!("start_bas_executed:{}", actual_session_id);
-                            let _: Result<(), redis::RedisError> = redis::cmd("SET")
-                                .arg(&key)
-                                .arg("1")
-                                .arg("EX")
-                                .arg(86400) // 24h TTL
-                                .query_async(&mut conn)
-                                .await;
-                        }
-                    }
+                    info!("start.bas completed successfully for session {}", actual_session_id);
                 }
                 Ok(Err(e)) => {
                     error!("start.bas error for session {}: {}", actual_session_id, e);