From 4a931bccab5879ab708647b2df8dadc052f128bf Mon Sep 17 00:00:00 2001
From: "Anderson A. Giacomolli" <agiacomolli@gmail.com>
Date: Sun, 8 Nov 2026 10:18:02 -0300
Subject: [PATCH] Wait until the view has no pending summary

Memory.Settle returns when every line of the chat view is built, so a
subagent that starts gets a view with no pending summary, and the view
holds every message so far. A pending line with no running build belongs
to a failed build, which waits for the next message, so Settle returns
an error in place of a wait that never ends. It also ends with its
context, so an interrupted turn does not wait.

Issue: b1ac698
---
 memory.go      | 38 +++++++++++++++++++++++++--
 memory_test.go | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++
 view.go        | 12 +++++++++
 3 files changed, 118 insertions(+), 2 deletions(-)

diff --git a/memory.go b/memory.go
index 9846c98..0fd7d83 100644
--- a/memory.go
+++ b/memory.go
@@ -12,8 +12,14 @@ import (
 	"time"
 )
 
-// errMemoryNoView tells that a chat has messages but no saved view.
-var errMemoryNoView = errors.New("the chat has messages but no saved view")
+var (
+	// errMemoryNoView tells that a chat has messages but no saved view.
+	errMemoryNoView = errors.New("the chat has messages but no saved view")
+
+	// errMemoryUnsettled tells that a line of the view stays pending,
+	// because its build failed.
+	errMemoryUnsettled = errors.New("a summary of the view failed, and it is tried again at the next message")
+)
 
 // openMemory opens the chat in root and starts the builds that are ready. The
 // clock gives the dates of new messages and the days of new nodes. The builds
@@ -195,6 +201,34 @@ func (m *Memory) Wait(ctx context.Context) error {
 	}
 }
 
+// Settle returns when the chat view has no pending line, so that every message
+// so far is summarized. A pending line with no build that runs belongs to a
+// failed build, which waits for the next message, so Settle returns
+// errMemoryUnsettled in place of a wait that never ends.
+func (m *Memory) Settle(ctx context.Context) error {
+	for {
+		m.mutex.Lock()
+		pending := m.chat.Pending()
+		running := m.queue.Running()
+		changed := m.changed
+		m.mutex.Unlock()
+
+		if !pending {
+			return nil
+		}
+
+		if running == 0 {
+			return errMemoryUnsettled
+		}
+
+		select {
+		case <-changed:
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+	}
+}
+
 // Flush returns when every write before the call is durable.
 func (m *Memory) Flush(ctx context.Context) error {
 	return m.syncer.Flush(ctx)
diff --git a/memory_test.go b/memory_test.go
index 001f852..4dee8b2 100644
--- a/memory_test.go
+++ b/memory_test.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"maps"
 	"os"
@@ -144,6 +145,75 @@ func TestMemoryRunsAtMostEightBuilds(t *testing.T) {
 	}
 }
 
+func TestMemorySettleWaitsForThePendingLines(t *testing.T) {
+	summarizer := newFakeSummarizer()
+	summarizer.gate = make(chan struct{})
+	memory, err := openMemory(t.Context(), t.TempDir(), newTestClock().Now, summarizer)
+	require.NoError(t, err)
+
+	defer func() {
+		require.NoError(t, memory.Close())
+	}()
+
+	_, err = memory.Append("echo", memoryLongText(0))
+	require.NoError(t, err)
+	require.Contains(t, memory.View(), viewPending)
+
+	settled := make(chan error, 1)
+	go func() {
+		settled <- memory.Settle(t.Context())
+	}()
+
+	select {
+	case err = <-settled:
+		require.Fail(t, "Settle returned before the build", "error: %v", err)
+	case <-time.After(50 * time.Millisecond):
+	}
+
+	close(summarizer.gate)
+	require.NoError(t, <-settled)
+	require.NotContains(t, memory.View(), viewPending)
+}
+
+func TestMemorySettleFailsWhileABuildFailed(t *testing.T) {
+	summarizer := newFakeSummarizer()
+	summarizer.SetFailing(true)
+	memory, err := openMemory(t.Context(), t.TempDir(), newTestClock().Now, summarizer)
+	require.NoError(t, err)
+
+	defer func() {
+		require.NoError(t, memory.Close())
+	}()
+
+	_, err = memory.Append("echo", memoryLongText(0))
+	require.NoError(t, err)
+	require.ErrorIs(t, memory.Settle(t.Context()), errMemoryUnsettled)
+
+	summarizer.SetFailing(false)
+	_, err = memory.Append("user", "retry")
+	require.NoError(t, err)
+	require.NoError(t, memory.Settle(t.Context()))
+}
+
+func TestMemorySettleEndsWithItsContext(t *testing.T) {
+	summarizer := newFakeSummarizer()
+	summarizer.gate = make(chan struct{})
+	memory, err := openMemory(t.Context(), t.TempDir(), newTestClock().Now, summarizer)
+	require.NoError(t, err)
+
+	defer func() {
+		require.NoError(t, memory.Close())
+	}()
+
+	_, err = memory.Append("echo", memoryLongText(0))
+	require.NoError(t, err)
+
+	ctx, cancel := context.WithTimeout(t.Context(), 50*time.Millisecond)
+	defer cancel()
+
+	require.ErrorIs(t, memory.Settle(ctx), context.DeadlineExceeded)
+}
+
 func TestMemoryStartsALeafAfterFewerThanEightUnbuilt(t *testing.T) {
 	summarizer := newFakeSummarizer()
 	summarizer.SetFailing(true)
diff --git a/view.go b/view.go
index 9fcd7d8..233e089 100644
--- a/view.go
+++ b/view.go
@@ -168,6 +168,18 @@ func (v *View) Refresh(node Node) {
 	}
 }
 
+// Pending tells if a line of the view is not built yet.
+func (v *View) Pending() bool {
+	for _, line := range v.lines {
+		_, built := v.nodes[line]
+		if !built {
+			return true
+		}
+	}
+
+	return false
+}
+
 // Render returns the view as the model reads it: one line "id+n|text" for each
 // node inside <chat> tags, with the newlines of the text as spaces.
 func (v *View) Render() string {
-- 
2.53.0