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fix(runtime): drain steerQueue at top of RunStream loop to close idle-window race #2492

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Merged
simonferquel merged 9 commits into from
Apr 22, 2026
+417 −11
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fix(runtime): drain steerQueue at top of RunStream loop to close idle-window race #2492

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a5dcc60
fix(runtime): drain steerQueue at top of RunStream loop to close idle…
simonferquel-clanker Apr 22, 2026
cb757e9
fix(runtime): inject top-of-turn steer messages as plain user messages
simonferquel-clanker Apr 22, 2026
64e9f25
fix(runtime): address review findings on steer-queue top-of-turn drain
simonferquel-clanker Apr 22, 2026
7761854
fix(runtime): close end-of-iteration steer race at res.Stopped boundary
simonferquel-clanker Apr 22, 2026
4a17981
fix(runtime): use wrap=false at end-of-iteration steer drain; tighten…
simonferquel-clanker Apr 22, 2026
b9de3aa
fix(lint): empty line between embedded and regular fields; use assert…
simonferquel-clanker Apr 22, 2026
1420a25
test(runtime): add content assertion for end-of-iter steer; document …
simonferquel-clanker Apr 22, 2026
225fd9c
refactor(runtime): remove system-reminder envelope from steer injection
simonferquel-clanker Apr 22, 2026
584d8b7
docs(runtime): tighten steer-drain comments in loop.go
simonferquel-clanker Apr 22, 2026
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38 changes: 27 additions & 11 deletions pkg/runtime/loop.go
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,12 @@ func (r *LocalRuntime) registerDefaultTools() {
})
}

// appendSteerAndEmit adds a steer message to the session and emits the corresponding event.
func (r *LocalRuntime) appendSteerAndEmit(sess *session.Session, sm QueuedMessage, events chan<- Event) {
sess.AddMessage(session.UserMessage(sm.Content, sm.MultiContent...))
events <- UserMessage(sm.Content, sess.ID, sm.MultiContent, len(sess.Messages)-1)
}

// finalizeEventChannel performs cleanup at the end of a RunStream goroutine:
// restores the previous elicitation channel, emits the StreamStopped event,
// fires hooks, and closes the events channel.
Expand Down Expand Up @@ -294,6 +300,16 @@ func (r *LocalRuntime) RunStream(ctx context.Context, sess *session.Session) <-c
}
}

// Drain steer messages queued while idle or before the first model call
// (covers idle-window and first-turn-miss races).
if steered := r.steerQueue.Drain(ctx); len(steered) > 0 {
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@rumpl rumpl Apr 22, 2026

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I don't understand why this one is needed here?

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@simonferquel simonferquel Apr 22, 2026

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2 cases:

  • if a user sends a steering message while the turn is being ended, you end up with the steering messages being sent after the next tool call of the next turn instead of immediately
  • when used as a library, in an app that consider all messages as "interrupting" - a la Claude Code - this simplify things a lot: you do not have to treat messages sent while the runner is idle differently than when it is active: they all come from the same queue

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@rumpl rumpl Apr 22, 2026

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I'm not talking about the case when the turn is being ended, that's lower in the code. I'm asking why are we steering before the turn starts

messageCountBeforeSteer := len(sess.GetAllMessages())
for _, sm := range steered {
r.appendSteerAndEmit(sess, sm, events)
}
r.compactIfNeeded(ctx, sess, a, m, contextLimit, messageCountBeforeSteer, events)
}

messages := sess.GetMessages(a)
slog.Debug("Retrieved messages for processing", "agent", a.Name(), "message_count", len(messages))

Expand Down Expand Up @@ -418,19 +434,10 @@ func (r *LocalRuntime) RunStream(ctx context.Context, sess *session.Session) <-c
// Record per-toolset model override for the next LLM turn.
toolModelOverride = resolveToolCallModelOverride(res.Calls, agentTools)

// --- STEERING: mid-turn injection ---
// Drain ALL pending steer messages. These are urgent course-
// corrections that the model should see on the very next
// iteration, wrapped in <system-reminder> tags.
// Drain steer messages that arrived during tool calls.
if steered := r.steerQueue.Drain(ctx); len(steered) > 0 {
for _, sm := range steered {
wrapped := fmt.Sprintf(
"<system-reminder>\nThe user sent the following message while you were working:\n%s\n\nPlease address this in your next response while continuing with your current tasks.\n</system-reminder>",
sm.Content,
)
userMsg := session.UserMessage(wrapped, sm.MultiContent...)
sess.AddMessage(userMsg)
events <- UserMessage(sm.Content, sess.ID, sm.MultiContent, len(sess.Messages)-1)
r.appendSteerAndEmit(sess, sm, events)
}

r.compactIfNeeded(ctx, sess, a, m, contextLimit, messageCountBeforeTools, events)
Expand All @@ -441,6 +448,15 @@ func (r *LocalRuntime) RunStream(ctx context.Context, sess *session.Session) <-c
slog.Debug("Conversation stopped", "agent", a.Name())
r.executeStopHooks(ctx, sess, a, res.Content, events)

// Re-check steer queue: closes the race between the mid-loop drain and this stop.
if steered := r.steerQueue.Drain(ctx); len(steered) > 0 {
for _, sm := range steered {
r.appendSteerAndEmit(sess, sm, events)
}
r.compactIfNeeded(ctx, sess, a, m, contextLimit, messageCountBeforeTools, events)
continue
}

// --- FOLLOW-UP: end-of-turn injection ---
// Pop exactly one follow-up message. Unlike steered
// messages, follow-ups are plain user messages that start
Expand Down
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