Reject incomplete AI completions before showing generated answers

crates/searchi-ai/src/lib.rs

@@ -165,6 +165,15 @@ impl AiClient {
             .into_iter()
             .next()
             .ok_or(AiError::InvalidResponse("AI endpoint returned no choices"))?;
+        if choice
+            .finish_reason
+            .as_deref()
+            .is_some_and(|reason| reason != "stop")
+        {
+            return Err(AiError::InvalidResponse(
+                "AI endpoint did not finish a complete answer",
+            ));
+        }
         let content = choice.message.content.ok_or(AiError::InvalidResponse(
             "AI endpoint returned no textual content",
         ))?;
@@ -351,6 +360,9 @@ struct Completion {
 #[derive(Deserialize)]
 struct Choice {
     message: Message,
+    // Some compatible local servers omit this. When present, incomplete,
+    // filtered or tool-directed completions must not appear as finished drafts.
+    finish_reason: Option<String>,
 }
 #[derive(Deserialize)]
 struct Message {

crates/searchi-ai/src/tests.rs

@@ -20,6 +20,39 @@ fn completion(answer: &str, citations: Vec<&str>) -> Vec<u8> {
     serde_json::to_vec(&serde_json::json!({"choices":[{"message":{"content":serde_json::json!({"answer":answer,"citations":citations}).to_string()}}]})).unwrap()
 }
 type Wire = Arc<Mutex<Option<(String, Vec<u8>)>>>;
+
+#[test]
+fn incomplete_or_filtered_completions_are_not_accepted_as_finished_answers() {
+    for reason in ["length", "content_filter", "tool_calls", "unexpected"] {
+        let mut body: serde_json::Value = serde_json::from_slice(&completion(
+            "Sixty days written notice. [selected]",
+            vec!["selected"],
+        ))
+        .unwrap();
+        body["choices"][0]["finish_reason"] = serde_json::json!(reason);
+        let (base, _, worker) = server(200, serde_json::to_vec(&body).unwrap(), Duration::ZERO);
+        let result = AiClient::new(config(base)).unwrap().generate(&request());
+        worker.join().unwrap();
+        assert_eq!(
+            result.unwrap_err(),
+            AiError::InvalidResponse("AI endpoint did not finish a complete answer")
+        );
+    }
+}
+
+#[test]
+fn explicit_stop_completion_is_accepted() {
+    let mut body: serde_json::Value = serde_json::from_slice(&completion(
+        "Sixty days written notice. [selected]",
+        vec!["selected"],
+    ))
+    .unwrap();
+    body["choices"][0]["finish_reason"] = serde_json::json!("stop");
+    let (base, _, worker) = server(200, serde_json::to_vec(&body).unwrap(), Duration::ZERO);
+    let result = AiClient::new(config(base)).unwrap().generate(&request());
+    worker.join().unwrap();
+    assert!(result.is_ok());
+}
 fn server(status: u16, body: Vec<u8>, delay: Duration) -> (String, Wire, thread::JoinHandle<()>) {
     server_with_length(status, body, delay, true)
 }