fix(streaming): use async_stream to ensure [DONE] is always sent

src/server/mod.rs

@@ -6,9 +6,9 @@ use axum::{
     routing::{get, post},
 };
 use futures::stream::StreamExt;
-use std::time::Duration;
 use sqlx;
 use std::sync::Arc;
+use std::time::Duration;
 use tracing::{info, warn};
 use uuid::Uuid;
 
@@ -246,40 +246,49 @@ async fn chat_completions(
                 let stream_id = format!("chatcmpl-{}", Uuid::new_v4());
                 let stream_created = chrono::Utc::now().timestamp() as u64;
                 
-                // Map chunks to SSE events
-                let sse_stream = aggregating_stream
-                    .map(move |chunk_result| {
-                        match chunk_result {
-                            Ok(chunk) => {
-                                let response = ChatCompletionStreamResponse {
-                                    id: stream_id.clone(),
-                                    object: "chat.completion.chunk".to_string(),
-                                    created: stream_created,
-                                    model: chunk.model.clone(),
-                                    choices: vec![ChatStreamChoice {
-                                        index: 0,
-                                        delta: ChatStreamDelta {
-                                            role: None,
-                                            content: Some(chunk.content),
-                                            reasoning_content: chunk.reasoning_content,
-                                            tool_calls: chunk.tool_calls,
-                                        },
-                                        finish_reason: chunk.finish_reason,
-                                    }],
-                                };
-                                Event::default().json_data(response)
-                                    .map_err(|e| AppError::InternalError(format!("SSE error: {}", e)))
+                // Map chunks to SSE events - clone stream_id for the async block
+                let stream_id_for_sse = stream_id.clone();
+                
+                // Use async stream macro to ensure proper sequencing
+                let final_stream = async_stream::stream! {
+                    // First, process and yield all chunks from aggregator
+                    let mut stream = Box::pin(aggregating_stream
+                        .map(move |chunk_result| {
+                            match chunk_result {
+                                Ok(chunk) => {
+                                    let response = ChatCompletionStreamResponse {
+                                        id: stream_id_for_sse.clone(),
+                                        object: "chat.completion.chunk".to_string(),
+                                        created: stream_created,
+                                        model: chunk.model.clone(),
+                                        choices: vec![ChatStreamChoice {
+                                            index: 0,
+                                            delta: ChatStreamDelta {
+                                                role: None,
+                                                content: Some(chunk.content),
+                                                reasoning_content: chunk.reasoning_content,
+                                                tool_calls: chunk.tool_calls,
+                                            },
+                                            finish_reason: chunk.finish_reason,
+                                        }],
+                                    };
+                                    Event::default().json_data(response)
+                                        .map_err(|e| AppError::InternalError(format!("SSE error: {}", e)))
+                                }
+                                Err(e) => Err(e),
                             }
-                            Err(e) => Err(e),
-                        }
-                    });
+                        }));
+                    
+                    // Yield all chunks
+                    while let Some(item) = stream.next().await {
+                        yield item;
+                    }
+                    
+                    // Finally yield [DONE]
+                    yield Ok::<Event, AppError>(Event::default().data("[DONE]"));
+                };
 
-                // Chain [DONE] - using repeat_with to ensure it gets polled
-                let done_stream = futures::stream::repeat_with(|| Ok::<Event, AppError>(Event::default().data("[DONE]")))
-                    .take(1);
-                let out = sse_stream.chain(done_stream);
-
-                Ok(Sse::new(out).into_response())
+                Ok(Sse::new(final_stream).into_response())
             }
             Err(e) => {
                 // Record provider failure