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Fix streaming deadlock and harden websocket/SSE chat flow #7

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Merged
jbold merged 5 commits into from
Feb 8, 2026
Merged

Fix streaming deadlock and harden websocket/SSE chat flow #7

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faa8393
test: add full rust/wasm/e2e suite with ci gates
jbold Feb 8, 2026
18a5537
test: build mock-channel wasm fixture before rust suite
jbold Feb 8, 2026
8680d8b
test: build wasm fixture plugins for rust ci
jbold Feb 8, 2026
acc9710
Fix streaming deadlock and harden websocket/sse chat flow
jbold Feb 8, 2026
056b389
Merge remote-tracking branch 'origin/main' into feat/testing-suite-ph…
jbold Feb 8, 2026
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22 changes: 22 additions & 0 deletions Cargo.lock
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186 changes: 144 additions & 42 deletions src/agent/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -91,52 +91,84 @@ impl AgentRunner {
return Ok(());
}

// Create an internal channel to collect events from this LLM call
let (inner_tx, mut inner_rx) = mpsc::channel::<AgentEvent>(32);

provider
.call_streaming(&current_messages, tools, system_prompt, inner_tx)
.await?;

// Collect events, forwarding text/usage/error to client,
// collecting tool_use calls for dispatch
let mut tool_calls: Vec<(String, String, serde_json::Value)> = Vec::new();
let tool_calls: Vec<(String, String, serde_json::Value)> = {
// Create an internal channel to collect events from this LLM call.
// We must drain this channel while provider streaming is in-flight;
// otherwise long responses can fill the buffer and deadlock.
let (inner_tx, mut inner_rx) = mpsc::channel::<AgentEvent>(32);
let mut tool_calls: Vec<(String, String, serde_json::Value)> = Vec::new();
let mut provider_done = false;
let mut provider_error: Option<anyhow::Error> = None;

let provider_call =
provider.call_streaming(&current_messages, tools, system_prompt, inner_tx);
tokio::pin!(provider_call);

loop {
tokio::select! {
result = &mut provider_call, if !provider_done => {
provider_done = true;
if let Err(e) = result {
provider_error = Some(e);
}
}
maybe_event = inner_rx.recv() => {
let Some(event) = maybe_event else {
if !provider_done {
if let Err(e) = (&mut provider_call).await {
provider_error = Some(e);
}
}
break;
};

while let Some(event) = inner_rx.recv().await {
match event {
AgentEvent::Text(ref _t) => {
let _ = tx.send(event).await;
}
AgentEvent::ToolUse {
ref id,
ref name,
ref input,
} => {
// Forward to client so they can observe
let _ = tx
.send(AgentEvent::ToolUse {
id: id.clone(),
name: name.clone(),
input: input.clone(),
})
.await;
tool_calls.push((id.clone(), name.clone(), input.clone()));
}
AgentEvent::Usage { .. } => {
let _ = tx.send(event).await;
}
AgentEvent::Error(ref _e) => {
let _ = tx.send(event).await;
}
AgentEvent::Done => {
// Don't forward Done yet — we may need to continue the loop
match event {
AgentEvent::Text(ref _t) => {
let _ = tx.send(event).await;
}
AgentEvent::ToolUse {
ref id,
ref name,
ref input,
} => {
// Forward to client so they can observe
let _ = tx
.send(AgentEvent::ToolUse {
id: id.clone(),
name: name.clone(),
input: input.clone(),
})
.await;
tool_calls.push((id.clone(), name.clone(), input.clone()));
}
AgentEvent::Usage { .. } => {
let _ = tx.send(event).await;
}
AgentEvent::Error(ref _e) => {
let _ = tx.send(event).await;
}
AgentEvent::Done => {
// Don't forward Done yet — we may need to continue the loop
}
AgentEvent::ToolResult { .. } => {
// Shouldn't come from provider, but forward if it does
let _ = tx.send(event).await;
}
}
}
}
AgentEvent::ToolResult { .. } => {
// Shouldn't come from provider, but forward if it does
let _ = tx.send(event).await;

if provider_done && inner_rx.is_closed() && inner_rx.is_empty() {
break;
}
}
}

if let Some(e) = provider_error {
return Err(e);
}

tool_calls
};

// If no tool calls, we're done
if tool_calls.is_empty() {
Expand Down Expand Up @@ -366,3 +398,73 @@ impl Default for AgentRunner {
Self::new()
}
}

#[cfg(test)]
mod tests {
use super::{AgentEvent, AgentRunner, providers};
use crate::sandbox::PluginHost;
use async_trait::async_trait;
use std::sync::Arc;
use tokio::sync::{RwLock, mpsc};
use tokio::time::{Duration, timeout};

struct BurstProvider {
chunks: usize,
}

#[async_trait]
impl providers::LlmProvider for BurstProvider {
async fn call_streaming(
&self,
_messages: &[serde_json::Value],
_tools: &[serde_json::Value],
_system_prompt: Option<&str>,
tx: mpsc::Sender<AgentEvent>,
) -> anyhow::Result<()> {
for i in 0..self.chunks {
tx.send(AgentEvent::Text(format!("chunk-{i}"))).await?;
}
tx.send(AgentEvent::Done).await?;
Ok(())
}
}

#[tokio::test]
async fn run_with_tools_drains_stream_while_provider_is_running() {
let runner = AgentRunner::new();
let provider = BurstProvider { chunks: 64 };
let plugins = Arc::new(RwLock::new(PluginHost::new()));
let (tx, mut rx) = mpsc::channel::<AgentEvent>(256);

timeout(
Duration::from_secs(5),
runner.run_with_tools(
&provider,
vec![serde_json::json!({
"role": "user",
"content": "hello",
})],
&[],
None,
&plugins,
tx,
),
)
.await
.expect("runner should not deadlock")
.expect("runner should succeed");

let mut text_count = 0usize;
let mut saw_done = false;
while let Ok(event) = rx.try_recv() {
match event {
AgentEvent::Text(_) => text_count += 1,
AgentEvent::Done => saw_done = true,
_ => {}
}
}

assert_eq!(text_count, 64);
assert!(saw_done);
}
}
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