MCP type_text reports a refused paragraph break instead of typing the next line (#1356) (#1407)

crates/mcp/src/tests.rs

@@ -119,3 +119,36 @@ fn headless_sessions_keep_the_dictionary_in_memory() {
     h.session.run("review.addToDictionary", &json!({"word": "zxqmcpword2"})).expect("added");
     assert!(h.session.user_dict_path.is_none());
 }
+
+/// A backend whose paragraph break is refused while text insertion would succeed.
+struct RefusesParagraph {
+    calls: std::sync::Arc<std::sync::Mutex<Vec<String>>>,
+}
+
+impl crate::backend::Backend for RefusesParagraph {
+    fn call(&mut self, _method: &str, params: Value) -> Result<Value, String> {
+        let command = params["command"].as_str().unwrap_or("").to_string();
+        self.calls.lock().unwrap().push(command.clone());
+        match command.as_str() {
+            "text.newParagraph" => Err("paragraph break refused".into()),
+            _ => Ok(json!({"ok": true})),
+        }
+    }
+    fn has_ui(&self) -> bool {
+        false
+    }
+    fn describe(&self) -> String {
+        "refuses paragraphs".into()
+    }
+}
+
+/// #1356: a refused paragraph break is reported and the next line is not typed after it.
+#[test]
+fn type_text_stops_at_a_refused_paragraph_break() {
+    let calls = std::sync::Arc::new(std::sync::Mutex::new(Vec::new()));
+    let mut s = Server::new(Box::new(RefusesParagraph { calls: calls.clone() }));
+    let r = call(&mut s, 11, "tools/call", json!({"name": "type_text", "arguments": {"text": "one\ntwo", "paragraphs": true}}));
+    assert_eq!(r["result"]["isError"], true, "{r}");
+    assert!(r["result"]["content"][0]["text"].as_str().unwrap().contains("paragraph break refused"), "{r}");
+    assert_eq!(*calls.lock().unwrap(), vec!["text.insert", "text.newParagraph"]);
+}

crates/mcp/src/tools.rs

@@ -233,6 +233,9 @@ pub fn call_tool(b: &mut dyn Backend, name: &str, a: &Value) -> ToolResult {
                 for (i, line) in t.split('\n').enumerate() {
                     if i > 0 {
                         last = exec(b, "text.newParagraph", json!({}));
+                        if last.is_err() {
+                            break;
+                        }
                     }
                     if !line.is_empty() {
                         last = exec(b, "text.insert", json!({"text": line, "raw": true}));