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feat(streaming): stream assistant tokens on-device and over the cloud

Thread an optional TokenSink through the InferenceBackend trait so a turn streams text as it is generated while still returning the full result. - LocalBackend streams via onde stream_message / stream_tool_results when no tools are offered. onde's tool-aware path must buffer to detect tool calls, so streaming covers the tools-disabled and final forced-text rounds. - OpenAiBackend streams via SSE (stream:true), reassembling content and index-keyed tool_calls; adds the reqwest "stream" feature. - TUI renders live tokens with <think> reasoning hidden. - ACP emits AgentMessageChunk deltas live, stripping <think> across chunk boundaries. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

paydii committed Jun 27, 2026 at 08:38 UTC 33432e5e59517a4bf5309af30839d67fae8fd3e6
4 files changed +527 -71
Cargo.toml
+1 -1
@@ -43,6 +43,6 @@ serde_json = "1"
43 toml = "0.8"
44 async-trait = "0.1"
45 regex = "1"
46 -reqwest = { version = "0.12", default-features = false, features = ["blocking", "json", "rustls-tls"] }
46 +reqwest = { version = "0.12", default-features = false, features = ["blocking", "json", "rustls-tls", "stream"] }
47 uuid = { version = "1", features = ["v4"] }
48 rpassword = "7"
src/backend.rs
+311 -6
@@ -62,24 +62,40 @@ pub struct TurnResult {
62 /// Backend errors are plain strings. Callers map them to ACP errors.
63 pub type BackendError = String;
64
65 +/// A sink for streaming assistant text deltas to the UI as they are produced.
66 +///
67 +/// When a caller passes `Some(sink)`, a streaming-capable backend forwards each
68 +/// text fragment through it as the model emits it; the returned [`TurnResult`]
69 +/// still carries the fully assembled text (and any tool calls). When the sink is
70 +/// `None`, the backend runs in non-streaming mode. Unbounded so the inference
71 +/// task never blocks on a slow consumer.
72 +pub type TokenSink = tokio::sync::mpsc::UnboundedSender<String>;
73 +
74 // ── The trait ───────────────────────────────────────────────────────────────────
75
76 /// A swappable inference backend driving siGit Code's agent loop.
77 #[async_trait]
78 pub trait InferenceBackend: Send + Sync {
79 /// Start an assistant turn from a new user message, offering `tools`.
80 + ///
81 + /// If `sink` is `Some`, text is streamed through it as it is generated. A
82 + /// backend may decline to stream a given round (for example, on-device
83 + /// inference cannot stream while it is still deciding whether to call a
84 + /// tool); in that case the text is delivered only via the returned result.
85 async fn send_message_with_tools(
86 &self,
87 text: &str,
88 tools: &[ToolSpec],
89 + sink: Option<&TokenSink>,
90 ) -> Result<TurnResult, BackendError>;
91
92 /// Continue the turn by returning tool results. `tools` may be `None` on the
78 - /// final round to force a text answer.
93 + /// final round to force a text answer. `sink` streams that text when set.
94 async fn send_tool_results(
95 &self,
96 results: Vec<ToolResult>,
97 tools: Option<&[ToolSpec]>,
98 + sink: Option<&TokenSink>,
99 ) -> Result<TurnResult, BackendError>;
100
101 /// Whether inference runs over the network (a configured provider) rather
@@ -118,7 +134,22 @@ impl InferenceBackend for LocalBackend {
134 &self,
135 text: &str,
136 tools: &[ToolSpec],
137 + sink: Option<&TokenSink>,
138 ) -> Result<TurnResult, BackendError> {
139 + // onde's tool-aware path is non-streaming: it has to buffer the whole
140 + // reply to detect tool calls. We can only stream when no tools are on
141 + // offer (a plain answer), which is exactly the tools-disabled case.
142 + if let Some(sink) = sink
143 + && tools.is_empty()
144 + {
145 + let rx = self
146 + .engine
147 + .stream_message(text)
148 + .await
149 + .map_err(|error| error.to_string())?;
150 + return drain_onde_stream(rx, sink).await;
151 + }
152 +
153 let onde_tools = to_onde_tools(tools);
154 let result = self
155 .engine
@@ -132,6 +163,7 @@ impl InferenceBackend for LocalBackend {
163 &self,
164 results: Vec<ToolResult>,
165 tools: Option<&[ToolSpec]>,
166 + sink: Option<&TokenSink>,
167 ) -> Result<TurnResult, BackendError> {
168 let onde_results: Vec<onde::inference::ToolResult> = results
169 .into_iter()
@@ -140,6 +172,20 @@ impl InferenceBackend for LocalBackend {
172 content: result.content,
173 })
174 .collect();
175 +
176 + // The final round passes `tools = None` to force a text answer; that's
177 + // the only round onde can stream, since no further tool calls are parsed.
178 + if let Some(sink) = sink
179 + && tools.is_none()
180 + {
181 + let rx = self
182 + .engine
183 + .stream_tool_results(onde_results, None)
184 + .await
185 + .map_err(|error| error.to_string())?;
186 + return drain_onde_stream(rx, sink).await;
187 + }
188 +
189 let onde_tools = tools.map(to_onde_tools);
190 let result = self
191 .engine
@@ -154,6 +200,38 @@ impl InferenceBackend for LocalBackend {
200 }
201 }
202
203 +/// Drain an onde streaming receiver, forwarding each token to `sink` and
204 +/// assembling the full text. onde reports stream failures as a final chunk whose
205 +/// `finish_reason` is `"error: …"`; surface those as a backend error.
206 +async fn drain_onde_stream(
207 + mut rx: tokio::sync::mpsc::Receiver<onde::inference::StreamChunk>,
208 + sink: &TokenSink,
209 +) -> Result<TurnResult, BackendError> {
210 + let mut text = String::new();
211 + while let Some(chunk) = rx.recv().await {
212 + if !chunk.delta.is_empty() {
213 + text.push_str(&chunk.delta);
214 + // The receiver is the UI; if it's gone the turn is being cancelled,
215 + // so stop assembling rather than spinning the model to completion.
216 + if sink.send(chunk.delta).is_err() {
217 + break;
218 + }
219 + }
220 + if chunk.done {
221 + if let Some(reason) = chunk.finish_reason
222 + && let Some(message) = reason.strip_prefix("error: ")
223 + {
224 + return Err(message.to_string());
225 + }
226 + break;
227 + }
228 + }
229 + Ok(TurnResult {
230 + text,
231 + tool_calls: Vec::new(),
232 + })
233 +}
234 +
235 /// Convert an `onde` tool-aware result into the neutral [`TurnResult`].
236 fn onde_result_to_turn(result: onde::inference::ToolAwareResult) -> TurnResult {
237 TurnResult {
@@ -230,14 +308,20 @@ impl OpenAiBackend {
308 }
309
310 /// POST the current history (plus `tools`) and apply the assistant reply to
233 - /// history, returning the neutral turn result.
234 - async fn complete(&self, tools: Option<&[ToolSpec]>) -> Result<TurnResult, BackendError> {
311 + /// history, returning the neutral turn result. Streams via SSE when `sink`
312 + /// is set; otherwise reads a single JSON response.
313 + async fn complete(
314 + &self,
315 + tools: Option<&[ToolSpec]>,
316 + sink: Option<&TokenSink>,
317 + ) -> Result<TurnResult, BackendError> {
318 let url = format!("{}/chat/completions", self.base_url.trim_end_matches('/'));
319 + let streaming = sink.is_some();
320
321 let mut body = serde_json::json!({
322 "model": self.model,
323 "messages": *self.history.lock().await,
240 - "stream": false,
324 + "stream": streaming,
325 });
326 if let Some(tools) = tools
327 && !tools.is_empty()
@@ -260,6 +344,15 @@ impl OpenAiBackend {
344 return Err(format!("endpoint returned {status}: {detail}"));
345 }
346
347 + if let Some(sink) = sink {
348 + self.consume_stream(response, sink).await
349 + } else {
350 + self.consume_json(response).await
351 + }
352 + }
353 +
354 + /// Parse a single non-streaming chat-completion response.
355 + async fn consume_json(&self, response: reqwest::Response) -> Result<TurnResult, BackendError> {
356 let parsed: ChatCompletion = response
357 .json()
358 .await
@@ -289,6 +382,150 @@ impl OpenAiBackend {
382
383 Ok(TurnResult { text, tool_calls })
384 }
385 +
386 + /// Consume an OpenAI Server-Sent Events stream, forwarding content deltas to
387 + /// `sink` and reassembling any tool calls (which arrive fragmented across
388 + /// chunks, keyed by `index`).
389 + async fn consume_stream(
390 + &self,
391 + response: reqwest::Response,
392 + sink: &TokenSink,
393 + ) -> Result<TurnResult, BackendError> {
394 + use futures::StreamExt;
395 +
396 + let mut stream = response.bytes_stream();
397 + // Newlines are ASCII, so splitting raw bytes on `\n` never bisects a
398 + // multibyte UTF-8 sequence; we only lossily decode whole lines.
399 + let mut buffer: Vec<u8> = Vec::new();
400 + let mut text = String::new();
401 + let mut tool_accum: Vec<StreamingToolCall> = Vec::new();
402 + let mut done = false;
403 +
404 + while let Some(item) = stream.next().await {
405 + let bytes = item.map_err(|error| format!("stream read error: {error}"))?;
406 + buffer.extend_from_slice(&bytes);
407 +
408 + while let Some(pos) = buffer.iter().position(|&b| b == b'\n') {
409 + let line: Vec<u8> = buffer.drain(..=pos).collect();
410 + let line = String::from_utf8_lossy(&line);
411 + let line = line.trim();
412 +
413 + let Some(data) = line.strip_prefix("data:") else {
414 + continue;
415 + };
416 + let data = data.trim();
417 + if data == "[DONE]" {
418 + done = true;
419 + break;
420 + }
421 + if data.is_empty() {
422 + continue;
423 + }
424 +
425 + let chunk: StreamCompletion = match serde_json::from_str(data) {
426 + Ok(chunk) => chunk,
427 + // Skip keep-alive comments and anything we can't parse rather
428 + // than aborting a turn over one malformed frame.
429 + Err(_) => continue,
430 + };
431 +
432 + let Some(choice) = chunk.choices.into_iter().next() else {
433 + continue;
434 + };
435 + if let Some(content) = choice.delta.content
436 + && !content.is_empty()
437 + {
438 + text.push_str(&content);
439 + if sink.send(content).is_err() {
440 + // Consumer dropped (turn cancelled) — stop reading.
441 + done = true;
442 + break;
443 + }
444 + }
445 + for delta in choice.delta.tool_calls.into_iter().flatten() {
446 + let index = delta.index.unwrap_or(0) as usize;
447 + if tool_accum.len() <= index {
448 + tool_accum.resize_with(index + 1, StreamingToolCall::default);
449 + }
450 + let slot = &mut tool_accum[index];
451 + if let Some(id) = delta.id {
452 + slot.id = id;
453 + }
454 + if let Some(function) = delta.function {
455 + if let Some(name) = function.name {
456 + slot.name = name;
457 + }
458 + if let Some(arguments) = function.arguments {
459 + slot.arguments.push_str(&arguments);
460 + }
461 + }
462 + }
463 + }
464 +
465 + if done {
466 + break;
467 + }
468 + }
469 +
470 + let tool_calls: Vec<ToolCall> = tool_accum
471 + .iter()
472 + .filter(|call| !call.name.is_empty())
473 + .enumerate()
474 + .map(|(index, call)| ToolCall {
475 + id: if call.id.is_empty() {
476 + format!("call_{index}")
477 + } else {
478 + call.id.clone()
479 + },
480 + name: call.name.clone(),
481 + arguments: call.arguments.clone(),
482 + })
483 + .collect();
484 +
485 + // Record the assistant turn so later tool results have context.
486 + self.history
487 + .lock()
488 + .await
489 + .push(streamed_assistant_history(&text, &tool_calls));
490 +
491 + Ok(TurnResult { text, tool_calls })
492 + }
493 +}
494 +
495 +/// One tool call being reassembled from streamed deltas.
496 +#[derive(Default)]
497 +struct StreamingToolCall {
498 + id: String,
499 + name: String,
500 + arguments: String,
501 +}
502 +
503 +/// Rebuild the assistant message for replay in history after a streamed turn,
504 +/// preserving any tool calls so the follow-up request is well-formed. Mirrors
505 +/// [`ResponseMessage::into_history_value`] for the non-streaming path.
506 +fn streamed_assistant_history(text: &str, tool_calls: &[ToolCall]) -> serde_json::Value {
507 + let mut message = serde_json::json!({ "role": "assistant" });
508 + message["content"] = if text.is_empty() {
509 + serde_json::Value::Null
510 + } else {
511 + serde_json::Value::String(text.to_string())
512 + };
513 + if !tool_calls.is_empty() {
514 + message["tool_calls"] = serde_json::json!(
515 + tool_calls
516 + .iter()
517 + .map(|call| serde_json::json!({
518 + "id": call.id,
519 + "type": "function",
520 + "function": {
521 + "name": call.name,
522 + "arguments": call.arguments,
523 + }
524 + }))
525 + .collect::<Vec<_>>()
526 + );
527 + }
528 + message
529 }
530
531 #[async_trait]
@@ -297,18 +534,20 @@ impl InferenceBackend for OpenAiBackend {
534 &self,
535 text: &str,
536 tools: &[ToolSpec],
537 + sink: Option<&TokenSink>,
538 ) -> Result<TurnResult, BackendError> {
539 self.history
540 .lock()
541 .await
542 .push(serde_json::json!({ "role": "user", "content": text }));
305 - self.complete(Some(tools)).await
543 + self.complete(Some(tools), sink).await
544 }
545
546 async fn send_tool_results(
547 &self,
548 results: Vec<ToolResult>,
549 tools: Option<&[ToolSpec]>,
550 + sink: Option<&TokenSink>,
551 ) -> Result<TurnResult, BackendError> {
552 {
553 let mut history = self.history.lock().await;
@@ -320,7 +559,7 @@ impl InferenceBackend for OpenAiBackend {
559 }));
560 }
561 }
323 - self.complete(tools).await
562 + self.complete(tools, sink).await
563 }
564
565 fn is_remote(&self) -> bool {
@@ -390,6 +629,46 @@ struct ResponseFunction {
629 arguments: String,
630 }
631
632 +// ── OpenAI streaming (SSE) chunk shapes ─────────────────────────────────────────
633 +
634 +#[derive(Debug, Deserialize)]
635 +struct StreamCompletion {
636 + #[serde(default)]
637 + choices: Vec<StreamChoice>,
638 +}
639 +
640 +#[derive(Debug, Deserialize)]
641 +struct StreamChoice {
642 + #[serde(default)]
643 + delta: StreamDelta,
644 +}
645 +
646 +#[derive(Debug, Default, Deserialize)]
647 +struct StreamDelta {
648 + #[serde(default)]
649 + content: Option<String>,
650 + #[serde(default)]
651 + tool_calls: Option<Vec<StreamToolCallDelta>>,
652 +}
653 +
654 +#[derive(Debug, Deserialize)]
655 +struct StreamToolCallDelta {
656 + #[serde(default)]
657 + index: Option<u32>,
658 + #[serde(default)]
659 + id: Option<String>,
660 + #[serde(default)]
661 + function: Option<StreamFunctionDelta>,
662 +}
663 +
664 +#[derive(Debug, Deserialize)]
665 +struct StreamFunctionDelta {
666 + #[serde(default)]
667 + name: Option<String>,
668 + #[serde(default)]
669 + arguments: Option<String>,
670 +}
671 +
672 #[cfg(test)]
673 mod tests {
674 use super::*;
@@ -422,6 +701,32 @@ mod tests {
701 assert_eq!(json[0]["function"]["parameters"]["type"], "object");
702 }
703
704 + #[test]
705 + fn streamed_assistant_history_omits_empty_tool_calls() {
706 + let value = streamed_assistant_history("hello", &[]);
707 + assert_eq!(value["role"], "assistant");
708 + assert_eq!(value["content"], "hello");
709 + assert!(value.get("tool_calls").is_none());
710 + }
711 +
712 + #[test]
713 + fn streamed_assistant_history_preserves_tool_calls() {
714 + let calls = vec![ToolCall {
715 + id: "call_0".to_string(),
716 + name: "read_file".to_string(),
717 + arguments: r#"{"path":"a.rs"}"#.to_string(),
718 + }];
719 + let value = streamed_assistant_history("", &calls);
720 + assert!(value["content"].is_null());
721 + assert_eq!(value["tool_calls"][0]["id"], "call_0");
722 + assert_eq!(value["tool_calls"][0]["type"], "function");
723 + assert_eq!(value["tool_calls"][0]["function"]["name"], "read_file");
724 + assert_eq!(
725 + value["tool_calls"][0]["function"]["arguments"],
726 + r#"{"path":"a.rs"}"#
727 + );
728 + }
729 +
730 #[test]
731 fn assistant_message_with_tool_calls_round_trips() {
732 let message = ResponseMessage {
src/chat.rs
+89 -35
@@ -75,7 +75,7 @@ mod tui {
75 use anyhow::Result;
76 use crossterm::event::{Event, EventStream, KeyCode, KeyEvent, KeyEventKind, KeyModifiers};
77 use futures::StreamExt;
78 - use onde::inference::{ChatEngine, SamplingConfig, StreamChunk};
78 + use onde::inference::{ChatEngine, SamplingConfig};
79
80 use crate::backend::{InferenceBackend, LocalBackend, OpenAiBackend, ToolResult, ToolSpec};
81 use crate::models::{ModelCacheHealth, ModelPickerItem, ModelSource, build_model_picker_items};
@@ -148,6 +148,11 @@ mod tui {
148 enum InferenceUpdate {
149 /// show tool name in chat while it runs
150 ToolUse(String),
151 + /// a streamed token fragment of the assistant's reply
152 + Delta(String),
153 + /// the streamed reply is complete; commit the accumulated buffer
154 + StreamEnd,
155 + /// a complete (non-streamed) assistant reply
156 Response(String),
157 Error(String),
158 }
@@ -164,7 +169,8 @@ mod tui {
169 input: String,
170 cursor: usize,
171 scroll_offset: u16,
167 - stream_rx: Option<mpsc::Receiver<StreamChunk>>,
172 + /// true while assistant tokens are streaming into `stream_buf`
173 + streaming: bool,
174 stream_buf: String,
175 inference_rx: Option<mpsc::Receiver<InferenceUpdate>>,
176 model_load_rx: Option<mpsc::Receiver<ModelLoadUpdate>>,
@@ -260,7 +266,7 @@ mod tui {
266 input: String::new(),
267 cursor: 0,
268 scroll_offset: 0,
263 - stream_rx: None,
269 + streaming: false,
270 stream_buf: String::new(),
271 inference_rx: None,
272 model_load_rx: None,
@@ -298,11 +304,11 @@ mod tui {
304 }
305
306 fn is_streaming(&self) -> bool {
301 - self.stream_rx.is_some()
307 + self.streaming
308 }
309
310 fn finalize_stream(&mut self) {
305 - self.stream_rx = None;
311 + self.streaming = false;
312 if !self.stream_buf.is_empty() {
313 let text = std::mem::take(&mut self.stream_buf);
314 self.messages.push(ChatMessage::assistant(text));
@@ -311,11 +317,23 @@ mod tui {
317 }
318
319 fn push_stream_delta(&mut self, delta: &str) {
320 + self.streaming = true;
321 self.stream_buf.push_str(delta);
322 + // Hide reasoning the way the rest of the app does: keep the "thinking"
323 + // spinner until visible (non-<think>) text appears, then show the
324 + // live reply. Don't call stop_thinking() — that drops the channel.
325 + let (_think, visible) = super::strip_think_blocks(&self.stream_buf);
326 + self.thinking = visible.trim().is_empty();
327 self.blink_counter = self.blink_counter.wrapping_add(1);
328 self.blink_on = self.blink_counter % 4 < 2;
329 }
330
331 + /// The portion of the streaming buffer to show live, with reasoning hidden.
332 + fn visible_stream(&self) -> String {
333 + let (_think, visible) = super::strip_think_blocks(&self.stream_buf);
334 + visible
335 + }
336 +
337 fn start_thinking(&mut self) {
338 self.thinking = true;
339 self.thinking_tick = 0;
@@ -444,8 +462,9 @@ mod tui {
462 for msg in &self.messages {
463 lines += wrapped_line_count(&msg.text, msg.role, w);
464 }
447 - if !self.stream_buf.is_empty() {
448 - lines += wrapped_line_count(&self.stream_buf, Role::Assistant, w);
465 + let visible = self.visible_stream();
466 + if !visible.is_empty() {
467 + lines += wrapped_line_count(&visible, Role::Assistant, w);
468 }
469 if self.thinking || self.switching_model {
470 lines += 1;
@@ -851,10 +870,11 @@ mod tui {
870 render_chat_message(&mut lines, msg, inner_width as usize);
871 }
872
854 - if !app.stream_buf.is_empty() {
873 + let streamed_visible = app.visible_stream();
874 + if !streamed_visible.is_empty() {
875 let fake = ChatMessage {
876 role: Role::Assistant,
857 - text: app.stream_buf.clone(),
877 + text: streamed_visible,
878 think_block: None,
879 };
880 render_chat_message(&mut lines, &fake, inner_width as usize);
@@ -1387,7 +1407,36 @@ mod tui {
1407 vec![]
1408 };
1409
1390 - let mut result = match backend.send_message_with_tools(&text, &tools).await {
1410 + // Bridge the backend's token sink (plain strings) onto the UI update
1411 + // channel as `Delta` messages. The forwarder lives for the whole turn.
1412 + let (delta_tx, mut delta_rx) = mpsc::unbounded_channel::<String>();
1413 + let forward_tx = tx.clone();
1414 + let forwarder = tokio::spawn(async move {
1415 + while let Some(piece) = delta_rx.recv().await {
1416 + if forward_tx
1417 + .send(InferenceUpdate::Delta(piece))
1418 + .await
1419 + .is_err()
1420 + {
1421 + break;
1422 + }
1423 + }
1424 + });
1425 +
1426 + // The first round offers tools, so on-device inference can't stream it
1427 + // (it must buffer to detect tool calls). With tools disabled there are
1428 + // none to offer, so it streams directly.
1429 + let first_sink = if tools.is_empty() {
1430 + Some(&delta_tx)
1431 + } else {
1432 + None
1433 + };
1434 + let mut streamed = first_sink.is_some();
1435 +
1436 + let mut result = match backend
1437 + .send_message_with_tools(&text, &tools, first_sink)
1438 + .await
1439 + {
1440 Ok(r) => r,
1441 Err(err) => {
1442 let _ = tx.send(InferenceUpdate::Error(err)).await;
@@ -1398,6 +1447,8 @@ mod tui {
1447 let mut round = 0;
1448
1449 while !result.tool_calls.is_empty() && round < MAX_TOOL_ROUNDS {
1450 + // any tool call means the first round didn't produce a final answer
1451 + streamed = false;
1452 round += 1;
1453 log::info!("tool round {} — {} call(s)", round, result.tool_calls.len());
1454
@@ -1421,14 +1472,24 @@ mod tui {
1472 });
1473 }
1474
1424 - // on the last round, pass no tools so the model must produce text
1475 + // on the last round, pass no tools so the model must produce text —
1476 + // that's also the round we can stream on-device.
1477 let next_tools = if round < MAX_TOOL_ROUNDS {
1478 Some(tools.as_slice())
1479 } else {
1480 None
1481 };
1482 + let sink = if next_tools.is_none() {
1483 + streamed = true;
1484 + Some(&delta_tx)
1485 + } else {
1486 + None
1487 + };
1488
1431 - match backend.send_tool_results(tool_results, next_tools).await {
1489 + match backend
1490 + .send_tool_results(tool_results, next_tools, sink)
1491 + .await
1492 + {
1493 Ok(r) => result = r,
1494 Err(err) => {
1495 let _ = tx.send(InferenceUpdate::Error(err)).await;
@@ -1437,6 +1498,11 @@ mod tui {
1498 }
1499 }
1500
1501 + // Drop the sink so the forwarder finishes draining any buffered tokens
1502 + // before we commit the reply.
1503 + drop(delta_tx);
1504 + let _ = forwarder.await;
1505 +
1506 if result.tool_calls.is_empty() {
1507 if result.text.is_empty() {
1508 log::warn!(
@@ -1449,6 +1515,9 @@ mod tui {
1515 .to_string(),
1516 ))
1517 .await;
1518 + } else if streamed {
1519 + // tokens already went out as deltas; just commit the buffer
1520 + let _ = tx.send(InferenceUpdate::StreamEnd).await;
1521 } else {
1522 let _ = tx.send(InferenceUpdate::Response(result.text)).await;
1523 }
@@ -1588,29 +1657,6 @@ mod tui {
1657 app.tick();
1658 }
1659
1591 - // ── Streaming LLM tokens ──────────────────────────────────────
1592 - chunk = async {
1593 - match app.stream_rx.as_mut() {
1594 - Some(rx) => rx.recv().await,
1595 - None => pending().await,
1596 - }
1597 - } => {
1598 - match chunk {
1599 - Some(chunk) => {
1600 - if !chunk.delta.is_empty() {
1601 - app.push_stream_delta(&chunk.delta);
1602 - }
1603 - if chunk.done {
1604 - app.finalize_stream();
1605 - }
1606 - }
1607 - // sender dropped without done=true
1608 - None => {
1609 - app.finalize_stream();
1610 - }
1611 - }
1612 - }
1613 -
1660 // ── inference updates from background task ───────────────────
1661 update = async {
1662 match app.inference_rx.as_mut() {
@@ -1622,16 +1668,24 @@ mod tui {
1668 Some(InferenceUpdate::ToolUse(name)) => {
1669 app.messages.push(ChatMessage::system(format!("🔧 {name}")));
1670 }
1671 + Some(InferenceUpdate::Delta(delta)) => {
1672 + app.push_stream_delta(&delta);
1673 + }
1674 + Some(InferenceUpdate::StreamEnd) => {
1675 + app.finalize_stream();
1676 + }
1677 Some(InferenceUpdate::Response(text)) => {
1678 app.stop_thinking();
1679 app.messages.push(ChatMessage::assistant(text));
1680 }
1681 Some(InferenceUpdate::Error(msg)) => {
1682 + app.finalize_stream();
1683 app.stop_thinking();
1684 app.messages.push(ChatMessage::system(format!("error: {msg}")));
1685 }
1686 None => {
1687 // task finished, possibly with no text to show
1688 + app.finalize_stream();
1689 app.stop_thinking();
1690 }
1691 }
src/main.rs
+126 -29
@@ -61,6 +61,7 @@ use onde::inference::{ChatEngine, GgufModelConfig};
61
62 use crate::backend::{
63 InferenceBackend, LocalBackend, OpenAiBackend, ToolResult as BackendToolResult, ToolSpec,
64 + TurnResult,
65 };
66 use std::path::PathBuf;
67 use std::sync::atomic::{AtomicBool, Ordering};
@@ -568,6 +569,72 @@ impl SiGitAgent {
569 ))
570 }
571
572 + /// Run one inference turn (`fut`) while concurrently forwarding any streamed
573 + /// tokens to the editor. The sink receiver is drained as the future runs, so
574 + /// chunks reach the client live rather than all at once when it resolves.
575 + ///
576 + /// `assembled`/`sent`/`streamed_any` persist across the turns of a single
577 + /// prompt so reasoning is stripped consistently and we never re-send text.
578 + #[allow(clippy::too_many_arguments)]
579 + async fn drain_turn<F>(
580 + &self,
581 + cx: &ConnectionTo<Client>,
582 + session_id: &SessionId,
583 + fut: F,
584 + sink_rx: &mut tokio::sync::mpsc::UnboundedReceiver<String>,
585 + assembled: &mut String,
586 + sent: &mut String,
587 + streamed_any: &mut bool,
588 + ) -> Result<TurnResult, backend::BackendError>
589 + where
590 + F: std::future::Future<Output = Result<TurnResult, backend::BackendError>>,
591 + {
592 + tokio::pin!(fut);
593 + let result = loop {
594 + tokio::select! {
595 + done = &mut fut => break done,
596 + Some(piece) = sink_rx.recv() => {
597 + self.emit_visible_chunk(cx, session_id, &piece, assembled, sent, streamed_any);
598 + }
599 + }
600 + };
601 + // Flush tokens that landed between the last poll and the future resolving.
602 + while let Ok(piece) = sink_rx.try_recv() {
603 + self.emit_visible_chunk(cx, session_id, &piece, assembled, sent, streamed_any);
604 + }
605 + result
606 + }
607 +
608 + /// Append a streamed fragment, strip `<think>` reasoning from the running
609 + /// text, and send only the newly revealed visible suffix as a chunk. Tracking
610 + /// the assembled text (not just deltas) keeps think-block stripping correct
611 + /// even when a tag spans chunk boundaries.
612 + fn emit_visible_chunk(
613 + &self,
614 + cx: &ConnectionTo<Client>,
615 + session_id: &SessionId,
616 + piece: &str,
617 + assembled: &mut String,
618 + sent: &mut String,
619 + streamed_any: &mut bool,
620 + ) {
621 + assembled.push_str(piece);
622 + let (_think, visible) = chat::strip_think_blocks(assembled);
623 + match visible.strip_prefix(sent.as_str()) {
624 + Some(extra) if !extra.is_empty() => {
625 + let extra = extra.to_string();
626 + *sent = visible;
627 + *streamed_any = true;
628 + self.send_assistant_message(cx, session_id.clone(), extra)
629 + .ok();
630 + }
631 + // No new visible text, or the visible prefix changed retroactively
632 + // (rare, e.g. a late-closing think tag): just resync without
633 + // resending what's already on the wire.
634 + _ => *sent = visible,
635 + }
636 + }
637 +
638 fn send_tool_call_update(
639 &self,
640 cx: &ConnectionTo<Client>,
@@ -1076,8 +1143,26 @@ impl SiGitAgent {
1143
1144 let tools = agent_tools_as_specs();
1145
1079 - let mut result = backend
1080 - .send_message_with_tools(&user_text, &tools)
1146 + // Token sink: backends stream assistant text through this while a turn
1147 + // runs. We forward the visible portion to the editor as agent-message
1148 + // chunks live (see `drain_turn` / `emit_visible_chunk`). The sink stays
1149 + // alive for the whole prompt so `recv()` only ends when a turn future
1150 + // resolves, never because every sender was dropped.
1151 + let (sink, mut sink_rx) = tokio::sync::mpsc::unbounded_channel::<String>();
1152 + let mut assembled = String::new();
1153 + let mut sent = String::new();
1154 + let mut streamed_any = false;
1155 +
1156 + let mut result = self
1157 + .drain_turn(
1158 + cx,
1159 + &session_id,
1160 + backend.send_message_with_tools(&user_text, &tools, Some(&sink)),
1161 + &mut sink_rx,
1162 + &mut assembled,
1163 + &mut sent,
1164 + &mut streamed_any,
1165 + )
1166 .await
1167 .map_err(|error| {
1168 log::error!("send_message_with_tools failed: {error}");
@@ -1120,39 +1205,51 @@ impl SiGitAgent {
1205 None // last round: force text
1206 };
1207
1123 - result = backend
1124 - .send_tool_results(tool_results, next_tools)
1208 + result = self
1209 + .drain_turn(
1210 + cx,
1211 + &session_id,
1212 + backend.send_tool_results(tool_results, next_tools, Some(&sink)),
1213 + &mut sink_rx,
1214 + &mut assembled,
1215 + &mut sent,
1216 + &mut streamed_any,
1217 + )
1218 .await
1219 .map_err(|e| agent_client_protocol::Error::new(-32603, e.to_string()))?;
1220 }
1221
1129 - // ── Send the final text response ─────────────────────────────────
1130 - let reply_text = result.text.trim().to_string();
1131 -
1132 - let final_text = if reply_text.is_empty() {
1133 - if round > 0 {
1134 - log::warn!(
1135 - "prompt({}) — model returned empty reply after {} tool round(s)",
1136 - session_id,
1137 - round
1138 - );
1139 - "Something went wrong — the edits didn't go through. Try rephrasing what you need, or point me at the specific lines.".to_string()
1222 + // ── Final text response ───────────────────────────────────────────
1223 + // If anything streamed, the visible reply is already on the wire; only
1224 + // send a trailing block for the non-streamed path (e.g. on-device direct
1225 + // answers, which onde can't stream while tools are on offer).
1226 + if !streamed_any {
1227 + let reply_text = result.text.trim().to_string();
1228 + let final_text = if reply_text.is_empty() {
1229 + if round > 0 {
1230 + log::warn!(
1231 + "prompt({}) — model returned empty reply after {} tool round(s)",
1232 + session_id,
1233 + round
1234 + );
1235 + "Something went wrong — the edits didn't go through. Try rephrasing what you need, or point me at the specific lines.".to_string()
1236 + } else {
1237 + log::warn!(
1238 + "prompt({}) — model returned empty reply (no tool rounds)",
1239 + session_id
1240 + );
1241 + String::new()
1242 + }
1243 } else {
1141 - log::warn!(
1142 - "prompt({}) — model returned empty reply (no tool rounds)",
1143 - session_id
1144 - );
1145 - String::new()
1146 - }
1147 - } else {
1148 - // strip <think> blocks so reasoning tokens stay hidden
1149 - let (_think, visible) = chat::strip_think_blocks(&reply_text);
1150 - visible
1151 - };
1244 + // strip <think> blocks so reasoning tokens stay hidden
1245 + let (_think, visible) = chat::strip_think_blocks(&reply_text);
1246 + visible
1247 + };
1248
1153 - if !final_text.is_empty() {
1154 - self.send_assistant_message(cx, session_id.clone(), final_text)
1155 - .ok();
1249 + if !final_text.is_empty() {
1250 + self.send_assistant_message(cx, session_id.clone(), final_text)
1251 + .ok();
1252 + }
1253 }
1254
1255 log::info!("prompt({}) complete — {} tool round(s)", session_id, round);