fix(agent): preserve active turn during context retry rebuild

pkg/agent/pipeline_llm.go

@@ -369,15 +369,21 @@ func (p *Pipeline) CallLLM(
 				contextualSkills = ts.agent.ContextBuilder.ResolveActiveSkillsForContext(ts.activeSkills)
 			}
 			ts.recordSkillContextSnapshot(skillContextTriggerContextRetryRebuild, contextualSkills)
+			stableHistory, protectedTurnTail := splitHistoryForActiveTurn(
+				exec.history,
+				ts.persistedMessagesSnapshot(),
+			)
 			buildMessages := func(trimmedHistory []providers.Message) []providers.Message {
-				rebuildPromptReq := promptBuildRequestForTurn(ts, trimmedHistory, exec.summary, "", nil)
+				fullHistory := append(append([]providers.Message(nil), trimmedHistory...), protectedTurnTail...)
+				rebuildPromptReq := promptBuildRequestForTurn(ts, fullHistory, exec.summary, "", nil)
 				rebuildPromptReq.ActiveSkills = append([]string(nil), contextualSkills...)
 				return ts.agent.ContextBuilder.BuildMessagesFromPrompt(rebuildPromptReq)
 			}
 			originalHistoryCount := len(exec.history)
 			var fit bool
-			exec.history, exec.callMessages, fit = trimHistoryToFitContextWindow(
+			var trimmedStableHistory []providers.Message
-				exec.history,
+			trimmedStableHistory, exec.callMessages, fit = trimHistoryToFitContextWindow(
+				stableHistory,
 				func(trimmedHistory []providers.Message) []providers.Message {
 					rebuilt := buildMessages(trimmedHistory)
 					if exec.gracefulTerminal {
@@ -389,7 +395,8 @@ func (p *Pipeline) CallLLM(
 				exec.providerToolDefs,
 				ts.agent.MaxTokens,
 			)
-			exec.messages = buildMessages(exec.history)
+			exec.history = append(trimmedStableHistory, protectedTurnTail...)
+			exec.messages = buildMessages(trimmedStableHistory)
 			if exec.gracefulTerminal {
 				msgs := append([]providers.Message(nil), exec.messages...)
 				exec.callMessages = append(msgs, ts.interruptHintMessage())
@@ -406,13 +413,21 @@ func (p *Pipeline) CallLLM(
 				})
 			} else if !fit {
 				logger.WarnCF("agent", "Context still exceeds budget after retry compaction rebuild", map[string]any{
-					"session_key":    ts.sessionKey,
+					"session_key":         ts.sessionKey,
-					"retry":          retry,
+					"retry":               retry,
-					"history_msgs":   len(exec.history),
+					"history_msgs":        len(exec.history),
-					"context_window": ts.agent.ContextWindow,
+					"protected_turn_msgs": len(protectedTurnTail),
-					"max_tokens":     ts.agent.MaxTokens,
+					"context_window":      ts.agent.ContextWindow,
+					"max_tokens":          ts.agent.MaxTokens,
 				})
 			}
+			if !fit {
+				err = fmt.Errorf(
+					"context window still exceeded after retry compaction; refusing to drop active turn messages: %w",
+					err,
+				)
+				break
+			}
 			continue
 		}
 		break

pkg/agent/turn_state.go

@@ -634,13 +634,17 @@ func (ts *turnState) recordPersistedMessage(msg providers.Message) {
 	ts.persistedMessages = append(ts.persistedMessages, msg)
 }
 
+func (ts *turnState) persistedMessagesSnapshot() []providers.Message {
+	ts.mu.RLock()
+	defer ts.mu.RUnlock()
+	return append([]providers.Message(nil), ts.persistedMessages...)
+}
+
 func (ts *turnState) refreshRestorePointFromSession(agent *AgentInstance) {
 	history := agent.Sessions.GetHistory(ts.sessionKey)
 	summary := agent.Sessions.GetSummary(ts.sessionKey)
 
-	ts.mu.RLock()
+	persisted := ts.persistedMessagesSnapshot()
-	persisted := append([]providers.Message(nil), ts.persistedMessages...)
-	ts.mu.RUnlock()
 
 	if matched := matchingTurnMessageTail(history, persisted); matched > 0 {
 		history = append([]providers.Message(nil), history[:len(history)-matched]...)
@@ -680,13 +684,83 @@ func (ts *turnState) restoreSession(agent *AgentInstance) error {
 func matchingTurnMessageTail(history, persisted []providers.Message) int {
 	maxMatch := min(len(history), len(persisted))
 	for size := maxMatch; size > 0; size-- {
-		if reflect.DeepEqual(history[len(history)-size:], persisted[len(persisted)-size:]) {
+		if messageSlicesEquivalent(history[len(history)-size:], persisted[len(persisted)-size:]) {
 			return size
 		}
 	}
 	return 0
 }
 
+func splitHistoryForActiveTurn(
+	history []providers.Message,
+	persisted []providers.Message,
+) ([]providers.Message, []providers.Message) {
+	matched := matchingTurnMessageTail(history, persisted)
+	if matched <= 0 {
+		return append([]providers.Message(nil), history...), nil
+	}
+
+	stable := append([]providers.Message(nil), history[:len(history)-matched]...)
+	protected := append([]providers.Message(nil), history[len(history)-matched:]...)
+	return stable, protected
+}
+
+func messageSlicesEquivalent(a, b []providers.Message) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if !messagesEquivalent(a[i], b[i]) {
+			return false
+		}
+	}
+	return true
+}
+
+func messagesEquivalent(a, b providers.Message) bool {
+	return reflect.DeepEqual(normalizeMessageForComparison(a), normalizeMessageForComparison(b))
+}
+
+func normalizeMessageForComparison(msg providers.Message) providers.Message {
+	msg.PromptLayer = ""
+	msg.PromptSlot = ""
+	msg.PromptSource = ""
+
+	if len(msg.Media) == 0 {
+		msg.Media = nil
+	}
+	if len(msg.Attachments) == 0 {
+		msg.Attachments = nil
+	}
+	if len(msg.SystemParts) == 0 {
+		msg.SystemParts = nil
+	} else {
+		msg.SystemParts = append([]providers.ContentBlock(nil), msg.SystemParts...)
+		for i := range msg.SystemParts {
+			msg.SystemParts[i].PromptLayer = ""
+			msg.SystemParts[i].PromptSlot = ""
+			msg.SystemParts[i].PromptSource = ""
+		}
+	}
+	if len(msg.ToolCalls) == 0 {
+		msg.ToolCalls = nil
+	} else {
+		msg.ToolCalls = append([]providers.ToolCall(nil), msg.ToolCalls...)
+		for i := range msg.ToolCalls {
+			msg.ToolCalls[i].Name = ""
+			msg.ToolCalls[i].Arguments = nil
+			msg.ToolCalls[i].ThoughtSignature = ""
+			if msg.ToolCalls[i].Function != nil {
+				fn := *msg.ToolCalls[i].Function
+				fn.ThoughtSignature = ""
+				msg.ToolCalls[i].Function = &fn
+			}
+		}
+	}
+
+	return msg
+}
+
 func (ts *turnState) interruptHintMessage() providers.Message {
 	_, hint := ts.gracefulInterruptRequested()
 	content := "Interrupt requested. Stop scheduling tools and provide a short final summary."

pkg/agent/turn_state_test.go

@@ -0,0 +1,112 @@
+package agent
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/sipeed/picoclaw/pkg/providers"
+)
+
+func TestMatchingTurnMessageTail_IgnoresInternalRuntimeFields(t *testing.T) {
+	history := []providers.Message{
+		{Role: "user", Content: "question"},
+		{
+			Role: "assistant",
+			ToolCalls: []providers.ToolCall{
+				{
+					ID:   "call_1",
+					Type: "function",
+					Function: &providers.FunctionCall{
+						Name:      "read_file",
+						Arguments: `{"path":"/tmp/test"}`,
+					},
+				},
+			},
+		},
+	}
+
+	persisted := []providers.Message{
+		userPromptMessage("question", nil),
+		{
+			Role: "assistant",
+			ToolCalls: []providers.ToolCall{
+				{
+					ID:               "call_1",
+					Type:             "function",
+					Name:             "read_file",
+					Arguments:        map[string]any{"path": "/tmp/test"},
+					ThoughtSignature: "internal-signature",
+					Function: &providers.FunctionCall{
+						Name:             "read_file",
+						Arguments:        `{"path":"/tmp/test"}`,
+						ThoughtSignature: "internal-signature",
+					},
+				},
+			},
+		},
+	}
+
+	if got := matchingTurnMessageTail(history, persisted); got != 2 {
+		t.Fatalf("matchingTurnMessageTail() = %d, want 2", got)
+	}
+}
+
+func TestSplitHistoryForActiveTurn_ProtectsPersistedTail(t *testing.T) {
+	history := []providers.Message{
+		{Role: "user", Content: "old question"},
+		{Role: "assistant", Content: "old answer"},
+		{Role: "user", Content: "current question"},
+		{Role: "tool", Content: "tool output", ToolCallID: "call_1"},
+	}
+
+	persisted := []providers.Message{
+		userPromptMessage("current question", nil),
+		{Role: "tool", Content: "tool output", ToolCallID: "call_1"},
+	}
+
+	stable, protected := splitHistoryForActiveTurn(history, persisted)
+	if len(stable) != 2 {
+		t.Fatalf("stable history len = %d, want 2", len(stable))
+	}
+	if len(protected) != 2 {
+		t.Fatalf("protected tail len = %d, want 2", len(protected))
+	}
+	if protected[0].Content != "current question" {
+		t.Fatalf("protected[0].Content = %q, want current question", protected[0].Content)
+	}
+}
+
+func TestTrimHistoryToFitContextWindow_WithProtectedTurnTailKeepsActiveTurn(t *testing.T) {
+	current := strings.Repeat("current turn ", 80)
+	history := []providers.Message{
+		{Role: "user", Content: strings.Repeat("old turn ", 60)},
+		{Role: "assistant", Content: strings.Repeat("old reply ", 60)},
+		{Role: "user", Content: current},
+	}
+
+	stable, protected := splitHistoryForActiveTurn(history, []providers.Message{
+		userPromptMessage(current, nil),
+	})
+	trimmedStable, messages, fit := trimHistoryToFitContextWindow(
+		stable,
+		func(trimmedHistory []providers.Message) []providers.Message {
+			return append(append([]providers.Message(nil), trimmedHistory...), protected...)
+		},
+		120,
+		nil,
+		0,
+	)
+
+	if fit {
+		t.Fatal("expected protected active turn alone to remain over budget")
+	}
+	if len(trimmedStable) != 0 {
+		t.Fatalf("trimmed stable history len = %d, want 0", len(trimmedStable))
+	}
+	if len(messages) != 1 {
+		t.Fatalf("messages len = %d, want 1 protected active-turn message", len(messages))
+	}
+	if messages[0].Content != current {
+		t.Fatalf("messages[0].Content = %q, want protected current turn", messages[0].Content)
+	}
+}