fix(tui): count loop guard blocks as failures (#1658)

CHANGELOG.md

@@ -47,6 +47,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   legacy Windows console hosts now automatically enable low-motion rendering,
   disable fancy animations, and resolve `synchronized_output = "auto"` to off
   so streaming redraws do not overlap or visibly flicker (#1590).
+- **LoopGuard blocks now count as failed tool calls.** Identical tool-call
+  blocks now return a failed tool result instead of a success, so repeated
+  blocked checklist/tool retries can trip the existing failure warning and halt
+  path instead of spinning indefinitely (#1574).
 
 ### Thanks
 
@@ -59,7 +63,9 @@ picker catalog work harvested from #1201. Thanks to
 **[@kunpeng-ai-lab](https://github.com/kunpeng-ai-lab)** for the Windows
 composer scroll fix harvested from #1578, and **WuMing
 ([@asdfg314284230](https://github.com/asdfg314284230))** for the Windows
-PowerShell flicker fix harvested from #1591.
+PowerShell flicker fix harvested from #1591. Thanks to
+**[@maker316](https://github.com/maker316)** for the LoopGuard/checklist loop
+report in #1574.
 
 ## [0.8.37] - 2026-05-14
 

crates/tui/CHANGELOG.md

@@ -47,6 +47,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   legacy Windows console hosts now automatically enable low-motion rendering,
   disable fancy animations, and resolve `synchronized_output = "auto"` to off
   so streaming redraws do not overlap or visibly flicker (#1590).
+- **LoopGuard blocks now count as failed tool calls.** Identical tool-call
+  blocks now return a failed tool result instead of a success, so repeated
+  blocked checklist/tool retries can trip the existing failure warning and halt
+  path instead of spinning indefinitely (#1574).
 
 ### Thanks
 
@@ -59,7 +63,9 @@ picker catalog work harvested from #1201. Thanks to
 **[@kunpeng-ai-lab](https://github.com/kunpeng-ai-lab)** for the Windows
 composer scroll fix harvested from #1578, and **WuMing
 ([@asdfg314284230](https://github.com/asdfg314284230))** for the Windows
-PowerShell flicker fix harvested from #1591.
+PowerShell flicker fix harvested from #1591. Thanks to
+**[@maker316](https://github.com/maker316)** for the LoopGuard/checklist loop
+report in #1574.
 
 ## [0.8.37] - 2026-05-14
 

crates/tui/src/core/engine/turn_loop.rs

@@ -7,6 +7,10 @@
 
 use super::*;
 
+fn loop_guard_block_tool_result(message: String) -> ToolResult {
+    ToolResult::error(message).with_metadata(json!({"loop_guard": "identical_tool_call"}))
+}
+
 impl Engine {
     pub(super) async fn handle_deepseek_turn(
         &mut self,
@@ -1214,10 +1218,7 @@ impl Engine {
                         loop_guard.record_attempt(&tool_name, &tool_input)
                 {
                     crate::logging::warn(message.clone());
-                    guard_result = Some(
-                        ToolResult::success(message)
-                            .with_metadata(json!({"loop_guard": "identical_tool_call"})),
-                    );
+                    guard_result = Some(loop_guard_block_tool_result(message));
                 }
 
                 plans.push(ToolExecutionPlan {
@@ -2023,6 +2024,24 @@ mod tests {
         assert!(!should_hold_turn_for_subagents(0, 0));
     }
 
+    #[test]
+    fn loop_guard_block_tool_result_counts_as_failure() {
+        let result = loop_guard_block_tool_result("Blocked: repeated call".to_string());
+
+        assert!(
+            !result.success,
+            "LoopGuard blocks must count as tool failures so repeated blocked calls can trip halt handling"
+        );
+        assert_eq!(
+            result
+                .metadata
+                .as_ref()
+                .and_then(|m| m.get("loop_guard"))
+                .and_then(|v| v.as_str()),
+            Some("identical_tool_call")
+        );
+    }
+
     #[test]
     fn resolve_auto_effort_ignores_stored_turn_metadata() {
         let messages = vec![Message {