fix(openai): make tool_call arguments optional and fix silent stream termination (#6309)

Signed-off-by: rabi <ramishra@redhat.com>

crates/goose/src/agents/reply_parts.rs

@@ -235,7 +235,9 @@ impl Agent {
         };
 
         Ok(Box::pin(try_stream! {
-            while let Some(Ok((mut message, usage))) = stream.next().await {
+            while let Some(result) = stream.next().await {
+                let (mut message, usage) = result?;
+
                 // Store the model information in the global store
                 if let Some(usage) = usage.as_ref() {
                     crate::providers::base::set_current_model(&usage.model);
@@ -492,4 +494,44 @@ mod tests {
 
         Ok(())
     }
+
+    #[tokio::test]
+    async fn test_stream_error_propagation() {
+        use futures::StreamExt;
+
+        type StreamItem = Result<(Option<Message>, Option<ProviderUsage>), ProviderError>;
+        let stream = futures::stream::iter(vec![
+            Ok((Some(Message::assistant().with_text("chunk1")), None)),
+            Ok((Some(Message::assistant().with_text("chunk2")), None)),
+            Err(ProviderError::RequestFailed(
+                "simulated stream error".to_string(),
+            )),
+        ] as Vec<StreamItem>);
+
+        let mut pinned = Box::pin(stream);
+        let mut results = Vec::new();
+        let mut error_seen = false;
+
+        while let Some(result) = pinned.next().await {
+            match result {
+                Ok((message, _usage)) => {
+                    if let Some(msg) = message {
+                        results.push(msg.as_concat_text());
+                    }
+                }
+                Err(_e) => {
+                    error_seen = true;
+                    break;
+                }
+            }
+        }
+
+        assert_eq!(results.len(), 2);
+        assert_eq!(results[0], "chunk1");
+        assert_eq!(results[1], "chunk2");
+        assert!(
+            error_seen,
+            "Error should have been propagated, not silently ignored"
+        );
+    }
 }

crates/goose/src/providers/formats/openai.rs

@@ -18,10 +18,11 @@ use serde_json::{json, Value};
 use std::borrow::Cow;
 use std::ops::Deref;
 
-#[derive(Serialize, Deserialize, Debug)]
+#[derive(Serialize, Deserialize, Debug, Default)]
 struct DeltaToolCallFunction {
     name: Option<String>,
-    arguments: String, // chunk of encoded JSON,
+    #[serde(default)]
+    arguments: String,
 }
 
 #[derive(Serialize, Deserialize, Debug)]