fix(session): restore thread and legacy compatibility

web/backend/api/session.go

@@ -256,11 +256,13 @@ func (h *Handler) findPicoJSONLSessions(dir string) ([]picoJSONLSessionRef, erro
 
 	refs := make([]picoJSONLSessionRef, 0)
 	seen := make(map[string]struct{})
+	metaBackedBases := make(map[string]struct{})
 	for _, entry := range entries {
 		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".meta.json") {
 			continue
 		}
-		metaPath := filepath.Join(dir, entry.Name())
+		name := entry.Name()
+		metaPath := filepath.Join(dir, name)
 		meta, err := h.readSessionMeta(metaPath, "")
 		if err != nil {
 			continue
@@ -269,6 +271,27 @@ func (h *Handler) findPicoJSONLSessions(dir string) ([]picoJSONLSessionRef, erro
 		if !ok || ref.Key == "" || ref.ID == "" {
 			continue
 		}
+		metaBackedBases[strings.TrimSuffix(name, ".meta.json")] = struct{}{}
+		if _, exists := seen[ref.ID]; exists {
+			continue
+		}
+		seen[ref.ID] = struct{}{}
+		refs = append(refs, ref)
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".jsonl") {
+			continue
+		}
+		name := entry.Name()
+		base := strings.TrimSuffix(name, ".jsonl")
+		if _, ok := metaBackedBases[base]; ok {
+			continue
+		}
+		ref, ok := jsonlSessionRefFromFilename(name)
+		if !ok || ref.Key == "" || ref.ID == "" {
+			continue
+		}
 		if _, exists := seen[ref.ID]; exists {
 			continue
 		}
@@ -300,7 +323,8 @@ func (h *Handler) findLegacyPicoSessions(dir string) ([]picoLegacySessionRef, er
 	refs := make([]picoLegacySessionRef, 0)
 	seen := make(map[string]struct{})
 	for _, entry := range entries {
-		if entry.IsDir() || filepath.Ext(entry.Name()) != ".json" {
+		name := entry.Name()
+		if entry.IsDir() || filepath.Ext(name) != ".json" || strings.HasSuffix(name, ".meta.json") {
 			continue
 		}
 
@@ -323,6 +347,37 @@ func (h *Handler) findLegacyPicoSessions(dir string) ([]picoLegacySessionRef, er
 	return refs, nil
 }
 
+func jsonlSessionRefFromFilename(name string) (picoJSONLSessionRef, bool) {
+	if !strings.HasSuffix(name, ".jsonl") {
+		return picoJSONLSessionRef{}, false
+	}
+	base := strings.TrimSuffix(name, ".jsonl")
+	if base == "" {
+		return picoJSONLSessionRef{}, false
+	}
+
+	legacyPrefix := sanitizeSessionKey(legacyPicoSessionPrefix)
+	if strings.HasPrefix(base, legacyPrefix) {
+		sessionID := strings.TrimPrefix(base, legacyPrefix)
+		if sessionID == "" {
+			return picoJSONLSessionRef{}, false
+		}
+		return picoJSONLSessionRef{
+			ID:  sessionID,
+			Key: legacyPicoSessionPrefix + sessionID,
+		}, true
+	}
+
+	if session.IsOpaqueSessionKey(base) {
+		return picoJSONLSessionRef{
+			ID:  base,
+			Key: base,
+		}, true
+	}
+
+	return picoJSONLSessionRef{}, false
+}
+
 func (h *Handler) findLegacyPicoSession(dir, sessionID string) (picoLegacySessionRef, error) {
 	refs, err := h.findLegacyPicoSessions(dir)
 	if err != nil {

web/backend/api/session_test.go

@@ -750,3 +750,82 @@ func TestHandleSessions_FiltersEmptyJSONLFiles(t *testing.T) {
 		t.Fatalf("detail status = %d, want %d, body=%s", detailRec.Code, http.StatusNotFound, detailRec.Body.String())
 	}
 }
+
+func TestHandleSessions_ListsLegacyJSONLWithoutMeta(t *testing.T) {
+	configPath, cleanup := setupOAuthTestEnv(t)
+	defer cleanup()
+
+	dir := sessionsTestDir(t, configPath)
+	sessionKey := legacyPicoSessionPrefix + "missing-meta"
+	base := filepath.Join(dir, sanitizeSessionKey(sessionKey))
+	line, err := json.Marshal(providers.Message{Role: "user", Content: "recover me"})
+	if err != nil {
+		t.Fatalf("Marshal(message) error = %v", err)
+	}
+	if err := os.WriteFile(base+".jsonl", append(line, '\n'), 0o644); err != nil {
+		t.Fatalf("WriteFile(jsonl) error = %v", err)
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	listRec := httptest.NewRecorder()
+	listReq := httptest.NewRequest(http.MethodGet, "/api/sessions", nil)
+	mux.ServeHTTP(listRec, listReq)
+
+	if listRec.Code != http.StatusOK {
+		t.Fatalf("list status = %d, want %d, body=%s", listRec.Code, http.StatusOK, listRec.Body.String())
+	}
+
+	var items []sessionListItem
+	if err := json.Unmarshal(listRec.Body.Bytes(), &items); err != nil {
+		t.Fatalf("Unmarshal(list) error = %v", err)
+	}
+	if len(items) != 1 {
+		t.Fatalf("len(items) = %d, want 1", len(items))
+	}
+	if items[0].ID != "missing-meta" {
+		t.Fatalf("items[0].ID = %q, want %q", items[0].ID, "missing-meta")
+	}
+
+	detailRec := httptest.NewRecorder()
+	detailReq := httptest.NewRequest(http.MethodGet, "/api/sessions/missing-meta", nil)
+	mux.ServeHTTP(detailRec, detailReq)
+
+	if detailRec.Code != http.StatusOK {
+		t.Fatalf("detail status = %d, want %d, body=%s", detailRec.Code, http.StatusOK, detailRec.Body.String())
+	}
+}
+
+func TestHandleSessions_IgnoresMetaJSONInLegacyFallback(t *testing.T) {
+	configPath, cleanup := setupOAuthTestEnv(t)
+	defer cleanup()
+
+	dir := sessionsTestDir(t, configPath)
+	metaOnly := filepath.Join(dir, "agent_main_pico_direct_pico_meta-only.meta.json")
+	metaOnlyContent := []byte(`{"key":"agent:main:pico:direct:pico:meta-only","summary":"meta only"}`)
+	if err := os.WriteFile(metaOnly, metaOnlyContent, 0o644); err != nil {
+		t.Fatalf("WriteFile(meta) error = %v", err)
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	listRec := httptest.NewRecorder()
+	listReq := httptest.NewRequest(http.MethodGet, "/api/sessions", nil)
+	mux.ServeHTTP(listRec, listReq)
+
+	if listRec.Code != http.StatusOK {
+		t.Fatalf("list status = %d, want %d, body=%s", listRec.Code, http.StatusOK, listRec.Body.String())
+	}
+
+	var items []sessionListItem
+	if err := json.Unmarshal(listRec.Body.Bytes(), &items); err != nil {
+		t.Fatalf("Unmarshal(list) error = %v", err)
+	}
+	if len(items) != 0 {
+		t.Fatalf("len(items) = %d, want 0", len(items))
+	}
+}