fix(agent): keep standalone greetings tool-free

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Kept standalone conversational greetings tool-free and prevented them from
+  triggering synthetic continuation turns, while retaining the normal tool
+  surface for greetings that also contain an action request.
+
 ## [5.3.5] - 2026-07-17
 
 ### Added

README.md

@@ -271,6 +271,10 @@ object-only backend that cannot execute it.
 | MCP | `mcp__<server>__<tool>` | Namespaced tools owned by their source manager |
 | Dynamic workflows | `dynamic_workflow` | Explicitly registered A3S Flow-backed, replayable per-turn workflows |
 
+Standalone greetings are conversational turns: the model receives no tool
+definitions and a friendly response is not converted into a synthetic
+continuation. A greeting that also asks for work keeps the normal tool surface.
+
 The built-in skill registry starts empty; skills come from configured
 directories, `AgentDir`, inline host input, or live registration. The
 model-visible `program` tool executes JavaScript in QuickJS, not arbitrary

core/src/agent/completion_runtime.rs

@@ -64,7 +64,9 @@ impl AgentLoop {
             candidate_text
         };
 
-        if !force_terminal && self.inject_continuation_if_needed(state, turn, &candidate_text) {
+        if !force_terminal
+            && self.inject_continuation_if_needed(state, turn, &candidate_text, effective_prompt)
+        {
             return CompletionFlow::Continue;
         }
 
@@ -152,7 +154,12 @@ impl AgentLoop {
         state: &mut ExecutionLoopState,
         turn: usize,
         candidate_text: &str,
+        effective_prompt: &str,
     ) -> bool {
+        if crate::tools::is_standalone_conversation(effective_prompt) {
+            return false;
+        }
+
         let looks_incomplete = Self::looks_incomplete(candidate_text);
         if looks_incomplete && state.repeated_incomplete_response(candidate_text) {
             tracing::warn!(

core/src/agent/tests.rs

@@ -3302,6 +3302,29 @@ async fn test_repeated_incomplete_text_converges_after_one_continuation() {
     assert_eq!(mock_client.call_count.load(Ordering::SeqCst), 2);
 }
 
+#[tokio::test]
+async fn test_standalone_greeting_does_not_trigger_continuation() {
+    let greeting = "I'll be happy to help. What would you like to work on?";
+    let mock_client = Arc::new(MockLlmClient::new(vec![
+        MockLlmClient::text_response(greeting),
+        MockLlmClient::text_response("This response must not be consumed."),
+    ]));
+    let agent = AgentLoop::new(
+        mock_client.clone(),
+        Arc::new(ToolExecutor::new("/tmp".to_string())),
+        test_tool_context(),
+        AgentConfig {
+            max_continuation_turns: 20,
+            max_tool_rounds: 100,
+            ..Default::default()
+        },
+    );
+
+    let result = agent.execute(&[], "你好", None).await.unwrap();
+    assert_eq!(result.text, greeting);
+    assert_eq!(mock_client.call_count.load(Ordering::SeqCst), 1);
+}
+
 #[tokio::test]
 async fn test_agent_multiple_tools_single_turn() {
     // LLM returns 2 tool calls in one response

core/src/tools/mod.rs

@@ -35,6 +35,7 @@ pub(crate) use invocation::{
 };
 pub use program_tool::{ProgramTool, MAX_PROGRAM_SCRIPT_SOURCE_BYTES};
 pub use registry::ToolRegistry;
+pub(crate) use selector::is_standalone_conversation;
 pub use selector::{select_tools_for_messages, select_tools_for_prompt};
 pub use task::{
     parallel_task_params_schema, task_params_schema, ParallelTaskParams, ParallelTaskTool,

core/src/tools/selector.rs

@@ -64,6 +64,39 @@ const PROGRAM_TERMS: &[&str] = &[
 
 const MCP_TERMS: &[&str] = &["mcp", "external tool", "external server", "外部工具"];
 
+const STANDALONE_CONVERSATION: &[&str] = &[
+    "hi",
+    "hi there",
+    "hello",
+    "hello there",
+    "hey",
+    "greetings",
+    "good morning",
+    "good afternoon",
+    "good evening",
+    "how are you",
+    "how's it going",
+    "hows it going",
+    "what's up",
+    "whats up",
+    "thanks",
+    "thank you",
+    "你好",
+    "您好",
+    "嗨",
+    "哈喽",
+    "哈啰",
+    "早",
+    "早上好",
+    "上午好",
+    "下午好",
+    "晚上好",
+    "在吗",
+    "你好吗",
+    "谢谢",
+    "多谢",
+];
+
 /// Select the tools that should be exposed to the model for this turn.
 ///
 /// The executor still owns every registered tool. This function only trims the
@@ -78,7 +111,7 @@ pub fn select_tools_for_messages(
 }
 
 pub fn select_tools_for_prompt(tools: &[ToolDefinition], prompt: &str) -> Vec<ToolDefinition> {
-    if tools.is_empty() {
+    if tools.is_empty() || is_standalone_conversation(prompt) {
         return Vec::new();
     }
 
@@ -114,6 +147,32 @@ pub fn select_tools_for_prompt(tools: &[ToolDefinition], prompt: &str) -> Vec<To
     selected
 }
 
+/// Return whether a prompt is only a short conversational acknowledgement.
+///
+/// This is deliberately exact after whitespace and terminal-punctuation
+/// normalization. A greeting that also contains an action must retain the
+/// ordinary tool surface.
+pub(crate) fn is_standalone_conversation(prompt: &str) -> bool {
+    let normalized = prompt
+        .trim()
+        .trim_matches(is_conversational_boundary)
+        .split_whitespace()
+        .collect::<Vec<_>>()
+        .join(" ")
+        .to_lowercase();
+
+    STANDALONE_CONVERSATION.contains(&normalized.as_str())
+}
+
+fn is_conversational_boundary(character: char) -> bool {
+    character.is_ascii_punctuation()
+        || character.is_whitespace()
+        || matches!(
+            character,
+            '。' | '，' | '、' | '！' | '？' | '…' | '～' | '👋'
+        )
+}
+
 fn should_include_mcp_tool(
     name: &str,
     name_lower: &str,
@@ -264,6 +323,38 @@ mod tests {
         assert!(!names.contains(&"mcp__github__create_issue"));
     }
 
+    #[test]
+    fn standalone_greetings_do_not_expose_tools() {
+        let tools = defs(&["read", "grep", "bash", "web_search", "task"]);
+
+        for prompt in [
+            "hi",
+            "Hello!",
+            "how are you?",
+            "你好",
+            "您好！",
+            "在吗？",
+            "谢谢",
+        ] {
+            assert!(
+                select_tools_for_prompt(&tools, prompt).is_empty(),
+                "standalone greeting exposed tools: {prompt}"
+            );
+        }
+    }
+
+    #[test]
+    fn greeting_with_an_action_keeps_relevant_tools() {
+        let selected = select_tools_for_prompt(
+            &defs(&["read", "grep", "web_search"]),
+            "Hello! Inspect this repository for the parser implementation.",
+        );
+        let names: Vec<_> = selected.iter().map(|tool| tool.name.as_str()).collect();
+
+        assert!(names.contains(&"read"));
+        assert!(names.contains(&"grep"));
+    }
+
     #[test]
     fn program_terms_enable_program_tool() {
         let selected = select_tools_for_prompt(