fix(session): preserve archived history across summarize truncation

pkg/session/jsonl_backend.go

@@ -68,11 +68,13 @@ func (b *JSONLBackend) TruncateHistory(key string, keepLast int) {
 	}
 }
 
-// Save persists session state. Since the JSONL store fsyncs every write
-// immediately, the data is already durable. Save runs compaction to reclaim
-// space from logically truncated messages (no-op when there are none).
+// Save persists session state. JSONL writes are already durable because
+// Add*/Set*/Truncate* fsync metadata/data on each write, so Save is a no-op.
+//
+// Keeping Save non-compacting preserves full append-only JSONL archives for
+// UI/history inspection even when runtime context uses logical truncation.
 func (b *JSONLBackend) Save(key string) error {
-	return b.store.Compact(context.Background(), key)
+	return nil
 }
 
 // Close releases resources held by the underlying store.

pkg/session/jsonl_backend_test.go

@@ -1,7 +1,11 @@
 package session_test
 
 import (
+	"bufio"
 	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/sipeed/picoclaw/pkg/memory"
@@ -177,3 +181,57 @@ func TestJSONLBackend_SummarizeFlow(t *testing.T) {
 		t.Errorf("first message = %q, want %q", history[0].Content, "msg 16")
 	}
 }
+
+func TestJSONLBackend_SavePreservesArchivedJSONLLinesAfterTruncate(t *testing.T) {
+	dir := t.TempDir()
+	store, err := memory.NewJSONLStore(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { store.Close() })
+	b := session.NewJSONLBackend(store)
+
+	for i := 0; i < 12; i++ {
+		b.AddMessage("s1", "user", fmt.Sprintf("msg %d", i))
+	}
+	b.TruncateHistory("s1", 3)
+
+	// Runtime context remains truncated.
+	history := b.GetHistory("s1")
+	if len(history) != 3 {
+		t.Fatalf("got %d messages, want 3", len(history))
+	}
+
+	if err := b.Save("s1"); err != nil {
+		t.Fatal(err)
+	}
+
+	// Archive file should still retain full append-only history lines.
+	lineCount, err := countNonEmptyLines(filepath.Join(dir, "s1.jsonl"))
+	if err != nil {
+		t.Fatalf("countNonEmptyLines() error = %v", err)
+	}
+	if lineCount != 12 {
+		t.Fatalf("lineCount = %d, want 12", lineCount)
+	}
+}
+
+func countNonEmptyLines(path string) (int, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return 0, err
+	}
+	defer f.Close()
+
+	n := 0
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		if strings.TrimSpace(scanner.Text()) != "" {
+			n++
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return 0, err
+	}
+	return n, nil
+}

web/backend/api/session.go

@@ -164,7 +164,7 @@ func (h *Handler) readSessionMessages(path string, skip int) ([]providers.Messag
 	return msgs, nil
 }
 
-func (h *Handler) readJSONLSession(dir, sessionID string) (sessionFile, error) {
+func (h *Handler) readJSONLSession(dir, sessionID string, includeArchived bool) (sessionFile, error) {
 	sessionKey := picoSessionPrefix + sessionID
 	base := filepath.Join(dir, sanitizeSessionKey(sessionKey))
 	jsonlPath := base + ".jsonl"
@@ -175,7 +175,13 @@ func (h *Handler) readJSONLSession(dir, sessionID string) (sessionFile, error) {
 		return sessionFile{}, err
 	}
 
-	messages, err := h.readSessionMessages(jsonlPath, meta.Skip)
+	skip := meta.Skip
+	if includeArchived {
+		// Web history APIs should expose the full transcript archive rather than
+		// the runtime context window that uses logical skip-truncation.
+		skip = 0
+	}
+	messages, err := h.readSessionMessages(jsonlPath, skip)
 	if err != nil {
 		return sessionFile{}, err
 	}
@@ -406,7 +412,7 @@ func (h *Handler) handleListSessions(w http.ResponseWriter, r *http.Request) {
 			if !ok {
 				continue
 			}
-			sess, loadErr = h.readJSONLSession(dir, sessionID)
+			sess, loadErr = h.readJSONLSession(dir, sessionID, true)
 			if loadErr == nil && isEmptySession(sess) {
 				continue
 			}
@@ -419,6 +425,7 @@ func (h *Handler) handleListSessions(w http.ResponseWriter, r *http.Request) {
 					if jsonlSess, jsonlErr := h.readJSONLSession(
 						dir,
 						jsonlSessionID,
+						true,
 					); jsonlErr == nil &&
 						!isEmptySession(jsonlSess) {
 						continue
@@ -508,7 +515,7 @@ func (h *Handler) handleGetSession(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	sess, err := h.readJSONLSession(dir, sessionID)
+	sess, err := h.readJSONLSession(dir, sessionID, true)
 	if err == nil && isEmptySession(sess) {
 		err = os.ErrNotExist
 	}

web/backend/api/session_test.go

@@ -217,6 +217,72 @@ func TestHandleGetSession_JSONLStorage(t *testing.T) {
 	}
 }
 
+func TestHandleGetSession_JSONLStorage_IncludesArchivedMessagesAfterTruncate(t *testing.T) {
+	configPath, cleanup := setupOAuthTestEnv(t)
+	defer cleanup()
+
+	dir := sessionsTestDir(t, configPath)
+	store, err := memory.NewJSONLStore(dir)
+	if err != nil {
+		t.Fatalf("NewJSONLStore() error = %v", err)
+	}
+
+	sessionKey := picoSessionPrefix + "detail-jsonl-archived"
+	for _, msg := range []providers.Message{
+		{Role: "user", Content: "u1"},
+		{Role: "assistant", Content: "a1"},
+		{Role: "user", Content: "u2"},
+		{Role: "assistant", Content: "a2"},
+		{Role: "user", Content: "u3"},
+		{Role: "assistant", Content: "a3"},
+	} {
+		if err := store.AddFullMessage(nil, sessionKey, msg); err != nil {
+			t.Fatalf("AddFullMessage() error = %v", err)
+		}
+	}
+	if err := store.TruncateHistory(nil, sessionKey, 2); err != nil {
+		t.Fatalf("TruncateHistory() error = %v", err)
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	// Runtime history is logically truncated to the tail for context control.
+	runtimeMsgs, err := store.GetHistory(nil, sessionKey)
+	if err != nil {
+		t.Fatalf("GetHistory() error = %v", err)
+	}
+	if len(runtimeMsgs) != 2 {
+		t.Fatalf("len(runtimeMsgs) = %d, want 2", len(runtimeMsgs))
+	}
+
+	// Web API should still expose full archived transcript.
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/sessions/detail-jsonl-archived", nil)
+	mux.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d, body=%s", rec.Code, http.StatusOK, rec.Body.String())
+	}
+
+	var resp struct {
+		Messages []struct {
+			Role    string `json:"role"`
+			Content string `json:"content"`
+		} `json:"messages"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+	if len(resp.Messages) != 6 {
+		t.Fatalf("len(resp.Messages) = %d, want 6", len(resp.Messages))
+	}
+	if resp.Messages[0].Content != "u1" || resp.Messages[5].Content != "a3" {
+		t.Fatalf("unexpected transcript boundary: first=%q last=%q", resp.Messages[0].Content, resp.Messages[5].Content)
+	}
+}
+
 func TestHandleGetSession_ReconstructsVisibleMessageToolOutput(t *testing.T) {
 	configPath, cleanup := setupOAuthTestEnv(t)
 	defer cleanup()