diff --git a/internal/app/app_test.go b/internal/app/app_test.go
index 86e4b13..c682d00 100644
--- a/internal/app/app_test.go
+++ b/internal/app/app_test.go
@@ -49,10 +49,49 @@ func (m *mockLLMService) GenerateContent(ctx context.Context, prompt string, sch
 	return nil, nil
 }
 
+func (m *mockLLMService) GenerateContentWithResponse(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+	return nil
+}
+
 func TestNewApp(t *testing.T) {
-	app := NewApp()
+	mockArchiveSvc := &mockArchiveService{}
+	mockEmailSvc := &mockEmailService{}
+	mockMinifluxClientSvc := &mockMinifluxClientService{}
+	mockDigestSvc := &mockDigestService{}
+	mockLLMSvc := &mockLLMService{}
+	cfg := &config.Config{}
+
+	app := NewApp(
+		WithConfig(cfg),
+		WithArchiveService(mockArchiveSvc),
+		WithEmailService(mockEmailSvc),
+		WithMinifluxClientService(mockMinifluxClientSvc),
+		WithDigestService(mockDigestSvc),
+		WithLLMService(mockLLMSvc),
+	)
+
 	if app == nil {
 		t.Error("NewApp() should not return nil")
+		return
+	}
+
+	if app.Config != cfg {
+		t.Errorf("NewApp() did not set the config correctly. Got %v, want %v", app.Config, cfg)
+	}
+	if app.ArchiveService != mockArchiveSvc {
+		t.Errorf("NewApp() did not set the archive service correctly. Got %v, want %v", app.ArchiveService, mockArchiveSvc)
+	}
+	if app.EmailService != mockEmailSvc {
+		t.Errorf("NewApp() did not set the email service correctly. Got %v, want %v", app.EmailService, mockEmailSvc)
+	}
+	if app.MinifluxClientService != mockMinifluxClientSvc {
+		t.Errorf("NewApp() did not set the miniflux client service correctly. Got %v, want %v", app.MinifluxClientService, mockMinifluxClientSvc)
+	}
+	if app.DigestService != mockDigestSvc {
+		t.Errorf("NewApp() did not set the digest service correctly. Got %v, want %v", app.DigestService, mockDigestSvc)
+	}
+	if app.LLMService != mockLLMSvc {
+		t.Errorf("NewApp() did not set the LLM service correctly. Got %v, want %v", app.LLMService, mockLLMSvc)
 	}
 }
 
diff --git a/internal/app/services/llm.go b/internal/app/services/llm.go
index 3ab154d..72162b7 100644
--- a/internal/app/services/llm.go
+++ b/internal/app/services/llm.go
@@ -12,4 +12,5 @@ import (
 
 type LLMService interface {
 	GenerateContent(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error)
+	GenerateContentWithResponse(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error
 }
diff --git a/internal/digest/digest_test.go b/internal/digest/digest_test.go
index b88f163..536e4d6 100644
--- a/internal/digest/digest_test.go
+++ b/internal/digest/digest_test.go
@@ -2,6 +2,7 @@ package digest
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"miniflux-digest/internal/digest/view"
 	"miniflux-digest/internal/models"
@@ -14,7 +15,8 @@ import (
 )
 
 type mockLLMService struct {
-	GenerateContentFunc func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error)
+	GenerateContentFunc             func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error)
+	GenerateContentWithResponseFunc func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error
 }
 
 func (m *mockLLMService) GenerateContent(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
@@ -24,6 +26,13 @@ func (m *mockLLMService) GenerateContent(ctx context.Context, prompt string, sch
 	return nil, errors.New("GenerateContentFunc not implemented")
 }
 
+func (m *mockLLMService) GenerateContentWithResponse(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+	if m.GenerateContentWithResponseFunc != nil {
+		return m.GenerateContentWithResponseFunc(ctx, prompt, schema, response)
+	}
+	return errors.New("GenerateContentWithResponseFunc not implemented")
+}
+
 func createLLMGrouperMockEntries() []*models.Entry {
 	return []*models.Entry{
 		{ID: 1, Title: "Entry 1", FeedID: 100, FeedTitle: "Feed A", GroupID: 1, GroupTitle: "Category A"},
@@ -34,31 +43,40 @@ func createLLMGrouperMockEntries() []*models.Entry {
 
 func TestDigestService_BuildDigestData(t *testing.T) {
 	mockLLM := &mockLLMService{
-		GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
+		GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
 			switch schema {
 			case view.InitialGroupingResponseSchema:
-				return []byte(`{
-					"groups": [
-						{
-							"title": "Go Lang",
-							"entry_ids": [2, 4]
-						},
-						{
-							"title": "AI News",
-							"entry_ids": [1, 3]
-						}
-					]
-				}`), nil
+				if err := json.Unmarshal([]byte(`{
+						"groups": [
+							{
+								"title": "AI News",
+								"entry_ids": [1]
+							},
+							{
+								"title": "Go Lang",
+								"entry_ids": [2, 3]
+							}
+						]
+					}`), response); err != nil {
+					return err
+				}
+				return nil
 			case view.SummaryResponseSchema:
-				return []byte(`{"summary": "This is a summary."}`), nil
+				if err := json.Unmarshal([]byte(`{"summary": "This is a summary."}`), response); err != nil {
+					return err
+				}
+				return nil
 			case view.SubGroupingResponseSchema:
-				return []byte(`{
-					"sub_groups": [
-						{"title": "Sub-group 1", "entry_ids": [1]}
-					]
-				}`), nil
+				if err := json.Unmarshal([]byte(`{
+						"sub_groups": [
+							{"title": "Sub-group 1", "entry_ids": [1]}
+						]
+					}`), response); err != nil {
+					return err
+				}
+				return nil
 			default:
-				return nil, errors.New("unexpected LLM call")
+				return errors.New("unexpected LLM call")
 			}
 		},
 	}
@@ -129,11 +147,11 @@ func TestDigestService_BuildDigestData(t *testing.T) {
 
 	t.Run("view=ai - GroupAIEntries error fallback", func(t *testing.T) {
 		mockLLM := &mockLLMService{
-			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
+			GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
 				if schema == view.InitialGroupingResponseSchema {
-					return nil, errors.New("mock LLM grouping error")
+					return errors.New("mock LLM grouping error")
 				}
-				return nil, errors.New("unexpected LLM call")
+				return errors.New("unexpected LLM call")
 			},
 		}
 		digestService := NewDigestService(mockLLM)
@@ -154,24 +172,30 @@ func TestDigestService_BuildDigestData(t *testing.T) {
 
 	t.Run("view=ai - sub-grouping error", func(t *testing.T) {
 		mockLLM := &mockLLMService{
-			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
+			GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
 				if schema == view.InitialGroupingResponseSchema {
-					return []byte(`{
+					if err := json.Unmarshal([]byte(`{
 						"groups": [
 							{
 								"title": "Test Group",
 								"entry_ids": [1, 2, 3]
 							}
 						]
-					}`), nil
+						}`), response); err != nil {
+						return err
+					}
+					return nil
 				}
 				if schema == view.SummaryResponseSchema {
-					return []byte(`{"summary": "This is a summary."}`), nil
+					if err := json.Unmarshal([]byte(`{"summary": "This is a summary."}`), response); err != nil {
+						return err
+					}
+					return nil
 				}
 				if schema == view.SubGroupingResponseSchema {
-					return nil, errors.New("mock LLM sub-grouping error")
+					return errors.New("mock LLM sub-grouping error")
 				}
-				return nil, errors.New("unexpected LLM call")
+				return errors.New("unexpected LLM call")
 			},
 		}
 		digestService := NewDigestService(mockLLM)
@@ -192,4 +216,5 @@ func TestDigestService_BuildDigestData(t *testing.T) {
 			t.Errorf("Expected a single 'Uncategorized' sub-group on error, got %+v", group.SubGroups)
 		}
 	})
-}
\ No newline at end of file
+}
+
diff --git a/internal/digest/view/ai.go b/internal/digest/view/ai.go
index 575c100..c63f72f 100644
--- a/internal/digest/view/ai.go
+++ b/internal/digest/view/ai.go
@@ -7,17 +7,20 @@ import (
 	"fmt"
 	"log"
 	"miniflux-digest/internal/app/services"
+	"miniflux-digest/internal/llm"
 	"miniflux-digest/internal/models"
 	"miniflux-digest/internal/utils"
 	"sort"
 	"strings"
 	"sync"
 	"text/template"
+
+	"google.golang.org/genai"
 )
 
 const (
 	MaxEntryContentLengthForLLM = 250
-	MaxEntriesForSummarization  = 150
+	MaxEntriesPerJob  = 150
 )
 
 type llmEntry struct {
@@ -28,14 +31,12 @@ type llmEntry struct {
 	FeedTitle string `json:"feed_title"`
 }
 
+
+
 func GroupAIEntries(ctx context.Context, entries []*models.Entry, llmService services.LLMService) (map[string][]*models.Entry, map[int64]bool, map[string][]*models.Entry) {
 	const chunkSize = 200
-	var wg sync.WaitGroup
-	var mu sync.Mutex
 
-	rawGroups := make(map[string][]*models.Entry)
-	groupedEntryIDs := make(map[int64]bool)
-	failedChunks := make(map[string][]*models.Entry)
+	// Prepare for processing
 	entryMap := make(map[int64]*models.Entry)
 	for _, entry := range entries {
 		entryMap[entry.ID] = entry
@@ -43,96 +44,43 @@ func GroupAIEntries(ctx context.Context, entries []*models.Entry, llmService ser
 
 	promptTemplate, err := template.New("grouping").Parse(initialGroupingPrompt)
 	if err != nil {
-		// This is a startup failure, not a runtime one, so we can't easily recover.
-		// We'll return it as a failed chunk.
+		failedChunks := make(map[string][]*models.Entry)
 		failedChunks["Prompt template parsing failed"] = entries
 		return nil, nil, failedChunks
 	}
 
-	for i := 0; i < len(entries); i += chunkSize {
-		end := min(i+chunkSize, len(entries))
-		chunk := entries[i:end]
-		wg.Add(1)
-
-		go func(chunk []*models.Entry, i, end int) {
-			defer wg.Done()
-
-			var llmEntries []llmEntry
-			for _, entry := range chunk {
-				content := entry.Content
-				if len(content) > MaxEntryContentLengthForLLM {
-					content = content[:MaxEntryContentLengthForLLM]
-				}
-				llmEntries = append(llmEntries, llmEntry{
-					ID:        entry.ID,
-					Title:     entry.Title,
-					URL:       entry.URL,
-					Content:   content,
-					FeedTitle: entry.FeedTitle,
-				})
-			}
-
-			entriesJSON, err := json.MarshalIndent(llmEntries, "", "  ")
-			if err != nil {
-				log.Printf("Failed to marshal entries to JSON for chunk %d-%d: %v", i, end, err)
-				mu.Lock()
-				failedChunks["JSON Marshal Error"] = append(failedChunks["JSON Marshal Error"], chunk...)
-				mu.Unlock()
-				return
-			}
-
-			var prompt bytes.Buffer
-			if err := promptTemplate.Execute(&prompt, nil); err != nil {
-				log.Printf("Failed to execute prompt template for chunk %d-%d: %v", i, end, err)
-				mu.Lock()
-				failedChunks["Prompt Execution Error"] = append(failedChunks["Prompt Execution Error"], chunk...)
-				mu.Unlock()
-				return
-			}
-			prompt.Write(entriesJSON)
-
-			llmResponse, err := llmService.GenerateContent(ctx, prompt.String(), InitialGroupingResponseSchema)
-			if err != nil {
-				log.Printf("LLM service failed for chunk %d-%d: %v", i, end, err)
-				errorKey := "LLM Error"
-				if strings.Contains(err.Error(), "DEADLINE_EXCEEDED") {
-					errorKey = "Processing Timeout"
-				}
-				mu.Lock()
-				failedChunks[errorKey] = append(failedChunks[errorKey], chunk...)
-				mu.Unlock()
-				return
-			}
-
-			var response InitialGroupingResponse
-			if err := json.Unmarshal(llmResponse, &response); err != nil {
-				log.Printf("Failed to parse LLM response for chunk %d-%d: %v", i, end, err)
-				mu.Lock()
-				failedChunks["LLM Response Parse Error"] = append(failedChunks["LLM Response Parse Error"], chunk...)
-				mu.Unlock()
-				return
-			}
-
-			mu.Lock()
-			defer mu.Unlock()
-			for _, group := range response.Groups {
-				if _, ok := rawGroups[group.Title]; !ok {
-					rawGroups[group.Title] = []*models.Entry{}
-				}
-				for _, entryID := range group.EntryIDs {
-					if _, exists := groupedEntryIDs[entryID]; exists {
-						continue
-					}
-					if entry, ok := entryMap[entryID]; ok {
-						rawGroups[group.Title] = append(rawGroups[group.Title], entry)
-						groupedEntryIDs[entryID] = true
-					}
-				}
-			}
-		}(chunk, i, end)
+	workerConfig := llmWorkerConfig{
+		promptTemplate: promptTemplate,
+		responseSchema: InitialGroupingResponseSchema,
+		prepareEntries: func(entries []*models.Entry) interface{} {
+			return prepareLLMEntries(entries)
+		},
 	}
+	worker := createLLMWorker[*InitialGroupingResponse](ctx, llmService, workerConfig, "")
 
-	wg.Wait()
+	// Run the parallel processing
+	chunkResponses, failedChunks := llm.ProcessInChunks(entries, chunkSize, worker)
+
+	// Process the results
+	rawGroups := make(map[string][]*models.Entry)
+	groupedEntryIDs := make(map[int64]bool)
+
+	for _, response := range chunkResponses {
+		for _, group := range response.Groups {
+			if _, ok := rawGroups[group.Title]; !ok {
+				rawGroups[group.Title] = []*models.Entry{}
+			}
+			for _, entryID := range group.EntryIDs {
+				if _, exists := groupedEntryIDs[entryID]; exists {
+					continue
+				}
+				if entry, ok := entryMap[entryID]; ok {
+					rawGroups[group.Title] = append(rawGroups[group.Title], entry)
+					groupedEntryIDs[entryID] = true
+				}
+			}
+		}
+	}
 
 	return rawGroups, groupedEntryIDs, failedChunks
 }
@@ -157,19 +105,13 @@ func consolidatePrimaryGroups(ctx context.Context, rawGroups map[string][]*model
 		return nil, fmt.Errorf("failed to execute consolidation prompt template: %w", err)
 	}
 
-	llmResponse, err := llmService.GenerateContent(ctx, prompt.String(), ConsolidationResponseSchema)
-	if err != nil {
+	var response ConsolidationResponse
+	if err := llmService.GenerateContentWithResponse(ctx, prompt.String(), ConsolidationResponseSchema, &response); err != nil {
 		// Fallback: If LLM fails, use the original, unconsolidated groups
 		log.Printf("LLM consolidation failed, falling back to original groups: %v", err)
 		return convertRawGroupsToDigestData(rawGroups), nil
 	}
 
-	var response ConsolidationResponse
-	if err := json.Unmarshal(llmResponse, &response); err != nil {
-		log.Printf("Failed to parse LLM consolidation response, falling back to original groups: %v", err)
-		return convertRawGroupsToDigestData(rawGroups), nil
-	}
-
 	// Merge groups based on consolidation response
 	consolidatedGroups := make(map[string][]*models.Entry)
 	mappedOldTitles := make(map[string]bool)
@@ -223,16 +165,215 @@ func convertRawGroupsToDigestData(rawGroups map[string][]*models.Entry) []*model
 	return digestData
 }
 
-func ProcessPrimaryGroupWithAI(ctx context.Context, pg *models.PrimaryGroup, llmService services.LLMService) (string, []*models.EntryGroup, error) {
-	var llmEntries []llmEntry
-	entriesToProcess := pg.Entries
-	if len(entriesToProcess) > MaxEntriesForSummarization {
-		entriesToProcess = entriesToProcess[:MaxEntriesForSummarization]
+
+
+func getSummaryForGroup(ctx context.Context, groupTitle string, entries []*models.Entry, llmService services.LLMService) (string, error) {
+	llmResponseWorker := createLLMWorker[SummaryResponse](ctx, llmService, llmWorkerConfig{
+		promptFormat:   summaryPrompt,
+		responseSchema: SummaryResponseSchema,
+		prepareEntries: func(entries []*models.Entry) interface{} {
+			return prepareLLMEntries(entries)
+		},
+	}, groupTitle)
+
+	summaryWorker := func(chunk []*models.Entry) (string, error) {
+		resp, err := llmResponseWorker(chunk)
+		if err != nil {
+			return "", err
+		}
+		return resp.Summary, nil
 	}
 
+	partialSummaries, failedChunks := llm.ProcessInChunks(entries, MaxEntriesPerJob, summaryWorker)
+
+	if len(partialSummaries) == 0 {
+		return "", fmt.Errorf("all summary chunks failed for group '%s'", groupTitle)
+	}
+
+	// Reduce step: summarize the summaries
+	summariesString := strings.Join(partialSummaries, "\n\n---\n\n")
+	finalSummaryPromptStr := fmt.Sprintf(summaryOfSummariesPrompt, summariesString)
+
+	var finalSummaryResponse SummaryResponse
+	if err := llmService.GenerateContentWithResponse(ctx, finalSummaryPromptStr, SummaryResponseSchema, &finalSummaryResponse); err != nil {
+		return "", fmt.Errorf("summary of summaries failed: %w", err)
+	}
+
+	finalSummary := finalSummaryResponse.Summary
+	var failedItems []*models.Entry
+	for _, items := range failedChunks {
+		failedItems = append(failedItems, items...)
+	}
+	if len(failedItems) > 0 {
+		finalSummary += fmt.Sprintf("\n\n(Note: %d entries could not be included in the summary due to processing errors.)", len(failedItems))
+	}
+
+	return finalSummary, nil
+}
+
+func getSubGroupsForGroup(ctx context.Context, groupTitle string, entries []*models.Entry, llmService services.LLMService) ([]*models.EntryGroup, error) {
 	entryMap := make(map[int64]*models.Entry)
-	for _, entry := range entriesToProcess {
+	for _, entry := range entries {
 		entryMap[entry.ID] = entry
+	}
+
+	subGroupWorker := createLLMWorker[*SubGroupingResponse](ctx, llmService, llmWorkerConfig{
+		promptFormat:   subGroupingPrompt,
+		responseSchema: SubGroupingResponseSchema,
+		prepareEntries: func(entries []*models.Entry) interface{} {
+			return prepareLLMEntries(entries)
+		},
+	}, groupTitle)
+
+	partialSubGroupResponses, failedChunks := llm.ProcessInChunks(entries, MaxEntriesPerJob, subGroupWorker)
+
+	if len(partialSubGroupResponses) == 0 {
+		return nil, fmt.Errorf("all sub-grouping chunks failed for group '%s'", groupTitle)
+	}
+
+	// Reduce step: merge sub-groups
+	mergedSubGroups := make(map[string][]*models.Entry)
+	allGroupedEntryIDs := make(map[int64]bool)
+
+	for _, response := range partialSubGroupResponses {
+		for _, llmSubGroup := range response.SubGroups {
+			if _, ok := mergedSubGroups[llmSubGroup.Title]; !ok {
+				mergedSubGroups[llmSubGroup.Title] = []*models.Entry{}
+			}
+			for _, entryID := range llmSubGroup.EntryIDs {
+				if _, exists := allGroupedEntryIDs[entryID]; exists {
+					continue // Avoid duplicating entries if they appear in multiple chunk responses
+				}
+				if entry, ok := entryMap[entryID]; ok {
+					mergedSubGroups[llmSubGroup.Title] = append(mergedSubGroups[llmSubGroup.Title], entry)
+					allGroupedEntryIDs[entryID] = true
+				}
+			}
+		}
+	}
+
+	var finalSubGroups []*models.EntryGroup
+	for title, groupEntries := range mergedSubGroups {
+		if len(groupEntries) > 0 {
+			finalSubGroups = append(finalSubGroups, &models.EntryGroup{
+				Title:        title,
+				Entries:      groupEntries,
+				Slug:         utils.Slugify(title),
+				TotalEntries: len(groupEntries),
+				TotalFeeds:   getUniqueFeedIDs(groupEntries),
+			})
+		}
+	}
+
+	// Handle all ungrouped entries from all chunks
+	var allUngroupedEntries []*models.Entry
+	for _, entry := range entries {
+		if !allGroupedEntryIDs[entry.ID] {
+			allUngroupedEntries = append(allUngroupedEntries, entry)
+		}
+	}
+
+	// Collect all failed items from the map into a single slice
+	var allFailedItems []*models.Entry
+	for _, items := range failedChunks {
+		allFailedItems = append(allFailedItems, items...)
+	}
+
+	// Add items from failed chunks to a separate group
+	if len(allFailedItems) > 0 {
+		finalSubGroups = append(finalSubGroups, &models.EntryGroup{
+			Title:        "Uncategorized - Processing Failed",
+			Entries:      allFailedItems,
+			Slug:         "uncategorized-processing-failed",
+			TotalEntries: len(allFailedItems),
+			TotalFeeds:   getUniqueFeedIDs(allFailedItems),
+		})
+	}
+
+	if len(allUngroupedEntries) > 0 {
+		// Find existing "Uncategorized" group to append to, if it exists
+		var uncategorizedGroup *models.EntryGroup
+		for _, sg := range finalSubGroups {
+			if sg.Title == "Uncategorized" {
+				uncategorizedGroup = sg
+				break
+			}
+		}
+		if uncategorizedGroup != nil {
+			uncategorizedGroup.Entries = append(uncategorizedGroup.Entries, allUngroupedEntries...)
+		} else {
+			finalSubGroups = append(finalSubGroups, &models.EntryGroup{
+				Title:        "Uncategorized",
+				Entries:      allUngroupedEntries,
+				Slug:         "uncategorized",
+				TotalEntries: len(allUngroupedEntries),
+				TotalFeeds:   getUniqueFeedIDs(allUngroupedEntries),
+			})
+		}
+	}
+
+	return finalSubGroups, nil
+}
+
+func ProcessPrimaryGroupWithAI(ctx context.Context, pg *models.PrimaryGroup, llmService services.LLMService) (string, []*models.EntryGroup, error) {
+	entriesToProcess := pg.Entries
+
+	// If the group is large, process in chunks concurrently.
+	var finalSummary string
+	var finalSubGroups []*models.EntryGroup
+	var errSummary, errSubgroup error
+	var wg sync.WaitGroup
+
+	wg.Add(2)
+
+	// Goroutine for Summarization
+	go func() {
+		defer wg.Done()
+		finalSummary, errSummary = getSummaryForGroup(ctx, pg.Title, entriesToProcess, llmService)
+	}()
+
+	// Goroutine for Sub-grouping
+	go func() {
+		defer wg.Done()
+		finalSubGroups, errSubgroup = getSubGroupsForGroup(ctx, pg.Title, entriesToProcess, llmService)
+	}()
+
+	wg.Wait()
+
+	// Combine errors if any. For now, we just log them but don't halt everything.
+	if errSummary != nil {
+		log.Printf("Error generating summary for group '%s': %v", pg.Title, errSummary)
+	}
+	if errSubgroup != nil {
+		log.Printf("Error generating sub-groups for group '%s': %v", pg.Title, errSubgroup)
+		// If sub-grouping completely failed, create a single group as a fallback.
+		if finalSubGroups == nil {
+			finalSubGroups = []*models.EntryGroup{{ 
+				Title:        "Uncategorized",
+				Entries:      entriesToProcess,
+				Slug:         "uncategorized",
+				TotalEntries: len(entriesToProcess),
+				TotalFeeds:   getUniqueFeedIDs(entriesToProcess),
+			}}
+		}
+	}
+
+	return finalSummary, finalSubGroups, nil
+}
+
+func getUniqueFeedIDs(entries []*models.Entry) int {
+	uniqueFeedIDs := make(map[int64]bool)
+	for _, entry := range entries {
+		uniqueFeedIDs[entry.FeedID] = true
+	}
+	return len(uniqueFeedIDs)
+}
+
+
+
+func prepareLLMEntries(entries []*models.Entry) []llmEntry {
+	var llmEntries []llmEntry
+	for _, entry := range entries {
 		content := entry.Content
 		if len(content) > MaxEntryContentLengthForLLM {
 			content = content[:MaxEntryContentLengthForLLM]
@@ -245,103 +386,27 @@ func ProcessPrimaryGroupWithAI(ctx context.Context, pg *models.PrimaryGroup, llm
 			FeedTitle: entry.FeedTitle,
 		})
 	}
-
-	entriesJSON, err := json.MarshalIndent(llmEntries, "", "  ")
-	if err != nil {
-		return "", nil, fmt.Errorf("failed to marshal entries to JSON for AI processing: %w", err)
-	}
-
-	// 1. Get Summary
-	var summary string
-	summaryPromptFmt := fmt.Sprintf(summaryPrompt, pg.Title)
-	summaryFullPrompt := summaryPromptFmt + string(entriesJSON)
-
-	summaryResponseBytes, err := llmService.GenerateContent(ctx, summaryFullPrompt, SummaryResponseSchema)
-	if err != nil {
-		log.Printf("LLM service failed during summarization for primary group '%s': %v", pg.Title, err)
-	} else {
-		var summaryResponse SummaryResponse
-		if err := json.Unmarshal(summaryResponseBytes, &summaryResponse); err != nil {
-			log.Printf("Failed to parse LLM summarization response for primary group '%s': %v", pg.Title, err)
-		} else {
-			summary = summaryResponse.Summary
-		}
-	}
-
-	// 2. Get Sub-groups
-	var subGroups []*models.EntryGroup
-	subGroupingPromptFmt := fmt.Sprintf(subGroupingPrompt, pg.Title)
-	subGroupingFullPrompt := subGroupingPromptFmt + string(entriesJSON)
-
-	subGroupingResponseBytes, err := llmService.GenerateContent(ctx, subGroupingFullPrompt, SubGroupingResponseSchema)
-	if err != nil {
-		log.Printf("LLM service failed during sub-grouping for primary group '%s': %v. Creating single 'Uncategorized' group.", pg.Title, err)
-	} else {
-		var subGroupingResponse SubGroupingResponse
-		if err := json.Unmarshal(subGroupingResponseBytes, &subGroupingResponse); err != nil {
-			log.Printf("Failed to parse LLM sub-grouping response for primary group '%s': %v. Creating single 'Uncategorized' group.", pg.Title, err)
-		} else {
-			groupedEntryIDs := make(map[int64]bool)
-			for _, llmSubGroup := range subGroupingResponse.SubGroups {
-				var currentSubGroupEntries []*models.Entry
-				for _, entryID := range llmSubGroup.EntryIDs {
-					if entry, ok := entryMap[entryID]; ok {
-						currentSubGroupEntries = append(currentSubGroupEntries, entry)
-						groupedEntryIDs[entryID] = true
-					}
-				}
-				if len(currentSubGroupEntries) > 0 {
-					subGroups = append(subGroups, &models.EntryGroup{
-						Title:        llmSubGroup.Title,
-						Entries:      currentSubGroupEntries,
-						Slug:         utils.Slugify(llmSubGroup.Title),
-						TotalEntries: len(currentSubGroupEntries),
-						TotalFeeds:   getUniqueFeedIDs(currentSubGroupEntries),
-					})
-				}
-			}
-			// Handle ungrouped entries
-			var ungroupedEntries []*models.Entry
-			for _, entry := range entriesToProcess {
-				if !groupedEntryIDs[entry.ID] {
-					ungroupedEntries = append(ungroupedEntries, entry)
-				}
-			}
-			if len(ungroupedEntries) > 0 {
-				subGroups = append(subGroups, &models.EntryGroup{
-					Title:        "Uncategorized",
-					Entries:      ungroupedEntries,
-					Slug:         "uncategorized",
-					TotalEntries: len(ungroupedEntries),
-					TotalFeeds:   getUniqueFeedIDs(ungroupedEntries),
-				})
-			}
-		}
-	}
-
-	// Fallback if sub-grouping failed or returned no groups
-	if len(subGroups) == 0 {
-		subGroups = append(subGroups, &models.EntryGroup{
-			Title:        "Uncategorized",
-			Entries:      entriesToProcess,
-			Slug:         "uncategorized",
-			TotalEntries: len(entriesToProcess),
-			TotalFeeds:   getUniqueFeedIDs(entriesToProcess),
-		})
-	}
-
-	return summary, subGroups, nil
-}
-
-func getUniqueFeedIDs(entries []*models.Entry) int {
-	uniqueFeedIDs := make(map[int64]bool)
-	for _, entry := range entries {
-		uniqueFeedIDs[entry.FeedID] = true
-	}
-	return len(uniqueFeedIDs)
+	return llmEntries
 }
 
 func BuildDigestDataByAI(entries []*models.Entry, ctx context.Context, llmService services.LLMService) []*models.PrimaryGroupDigestData {
+	rawGroups, groupedEntryIDs, failedChunks, fallbackGroups := initialAIGGrouping(ctx, entries, llmService)
+	if fallbackGroups != nil {
+		return fallbackGroups
+	}
+
+	highLevelGroups := consolidateGroups(ctx, rawGroups, llmService)
+
+	highLevelGroups = handleFailedAndUngroupedEntries(highLevelGroups, entries, groupedEntryIDs, failedChunks)
+
+	allPrimaryGroups := processHighLevelGroupsConcurrently(ctx, highLevelGroups, llmService)
+
+	sortPrimaryGroups(allPrimaryGroups)
+
+	return allPrimaryGroups
+}
+
+func initialAIGGrouping(ctx context.Context, entries []*models.Entry, llmService services.LLMService) (map[string][]*models.Entry, map[int64]bool, map[string][]*models.Entry, []*models.PrimaryGroupDigestData) {
 	rawGroups, groupedEntryIDs, failedChunks := GroupAIEntries(ctx, entries, llmService)
 
 	// If all chunks failed and we have no raw groups, fall back to category grouping.
@@ -349,18 +414,24 @@ func BuildDigestDataByAI(entries []*models.Entry, ctx context.Context, llmServic
 		log.Printf("All AI grouping chunks failed, falling back to category grouping.")
 		categoryGroups := BuildDigestDataByCategory(entries)
 		if len(categoryGroups) == 1 && len(entries) > 1 {
-			return BuildDigestDataByDate(entries)
+			return nil, nil, nil, BuildDigestDataByDate(entries)
 		}
-		return categoryGroups
+		return nil, nil, nil, categoryGroups
 	}
+	return rawGroups, groupedEntryIDs, failedChunks, nil
+}
 
+func consolidateGroups(ctx context.Context, rawGroups map[string][]*models.Entry, llmService services.LLMService) []*models.PrimaryGroupDigestData {
 	highLevelGroups, err := consolidatePrimaryGroups(ctx, rawGroups, llmService)
 	if err != nil {
 		// This case should ideally not be hit if consolidatePrimaryGroups has a fallback
 		log.Printf("AI group consolidation failed unexpectedly: %v", err)
 		highLevelGroups = convertRawGroupsToDigestData(rawGroups)
 	}
+	return highLevelGroups
+}
 
+func handleFailedAndUngroupedEntries(highLevelGroups []*models.PrimaryGroupDigestData, allEntries []*models.Entry, groupedEntryIDs map[int64]bool, failedChunks map[string][]*models.Entry) []*models.PrimaryGroupDigestData {
 	failedEntryIDs := make(map[int64]bool)
 	for reason, chunkEntries := range failedChunks {
 		title := fmt.Sprintf("Uncategorized - %s", reason)
@@ -388,7 +459,7 @@ func BuildDigestDataByAI(entries []*models.Entry, ctx context.Context, llmServic
 
 	// Handle entries that were not grouped by the initial LLM call
 	var otherUngroupedEntries []*models.Entry
-	for _, entry := range entries {
+	for _, entry := range allEntries {
 		if !groupedEntryIDs[entry.ID] && !failedEntryIDs[entry.ID] {
 			otherUngroupedEntries = append(otherUngroupedEntries, entry)
 		}
@@ -413,7 +484,10 @@ func BuildDigestDataByAI(entries []*models.Entry, ctx context.Context, llmServic
 			TotalFeeds:   getUniqueFeedIDs(otherUngroupedEntries),
 		})
 	}
+	return highLevelGroups
+}
 
+func processHighLevelGroupsConcurrently(ctx context.Context, highLevelGroups []*models.PrimaryGroupDigestData, llmService services.LLMService) []*models.PrimaryGroupDigestData {
 	var allPrimaryGroups []*models.PrimaryGroupDigestData
 	var wg sync.WaitGroup
 	var mu sync.Mutex
@@ -458,10 +532,63 @@ func BuildDigestDataByAI(entries []*models.Entry, ctx context.Context, llmServic
 	}
 
 	wg.Wait()
+	return allPrimaryGroups
+}
 
+func sortPrimaryGroups(allPrimaryGroups []*models.PrimaryGroupDigestData) {
 	sort.Slice(allPrimaryGroups, func(i, j int) bool {
 		return allPrimaryGroups[i].Title < allPrimaryGroups[j].Title
 	})
-
-	return allPrimaryGroups
 }
+
+// llmWorkerConfig holds configuration for creating an LLM worker function.
+type llmWorkerConfig struct {
+	promptTemplate *template.Template
+	promptFormat   string // For prompts that use Sprintf
+	responseSchema *genai.Schema
+	prepareEntries func([]*models.Entry) interface{} // Function to prepare entries for LLM
+}
+
+// createLLMWorker creates a worker function for llm.ProcessInChunks.
+func createLLMWorker[R any](
+	ctx context.Context,
+	llmService services.LLMService,
+	config llmWorkerConfig,
+	groupTitle string, // Optional, for prompts that need it
+) llm.WorkerFunc[*models.Entry, R] {
+	return func(chunk []*models.Entry) (R, error) {
+		var zero R // Initialize a zero value of type R
+
+		// 1. Prepare LLM entries
+		var llmEntriesJSON []byte
+		if config.prepareEntries != nil {
+			prepared := config.prepareEntries(chunk)
+			var err error
+			llmEntriesJSON, err = json.MarshalIndent(prepared, "", "  ")
+			if err != nil {
+				return zero, fmt.Errorf("failed to marshal entries to JSON: %w", err)
+			}
+		}
+
+		// 2. Construct the prompt
+		var prompt bytes.Buffer
+		if config.promptTemplate != nil {
+			if err := config.promptTemplate.Execute(&prompt, nil); err != nil {
+				return zero, fmt.Errorf("failed to execute prompt template: %w", err)
+			}
+		} else if config.promptFormat != "" {
+			prompt.WriteString(fmt.Sprintf(config.promptFormat, groupTitle))
+		}
+
+		if len(llmEntriesJSON) > 0 {
+			prompt.Write(llmEntriesJSON)
+		}
+
+		// 3. Call LLM service
+		var response R
+		if err := llmService.GenerateContentWithResponse(ctx, prompt.String(), config.responseSchema, &response); err != nil {
+			return zero, err
+		}
+		return response, nil
+	}
+}
\ No newline at end of file
diff --git a/internal/digest/view/ai_prompts.go b/internal/digest/view/ai_prompts.go
index e113446..46a6495 100644
--- a/internal/digest/view/ai_prompts.go
+++ b/internal/digest/view/ai_prompts.go
@@ -52,7 +52,7 @@ A good consolidation would be:
 
 const summaryPrompt = `You are an expert at summarizing content for busy readers. You will be given a list of entries from a primary group titled '%s'.
 
-Your task is to write a concise, 2-3 sentence summary (under 150 words) that achieves two goals:
+Your task is to write a concise, 2-3 sentence summary (under 250 words) that achieves two goals:
 1.  **Provide a high-level overview** of the main themes in the group.
 2.  **Highlight the most significant or surprising entries.** This could be a major announcement, a controversial opinion, or a particularly popular discussion.
 
@@ -70,6 +70,19 @@ Your task is to create smaller, more granular sub-groups to help a user navigate
 - If an entry doesn't fit into a specific sub-group, leave it out of your response.
 `
 
+const summaryOfSummariesPrompt = `You are an expert at creating overviews of large swaths of web updates and web content.
+
+Your task is to write a concise, 2-3 sentence summary (under 250 words) that achieves two goals:
+1.  **Provide a high-level overview** of the main themes.
+2.  **Highlight the most significant or surprising entries.** This could be a major announcement, a controversial opinion, or a particularly popular discussion.
+
+The goal is to give the reader enough information to quickly decide if this group contains entries they want to explore further. Do not just list the topics; provide some insight into the content.
+
+Here are the summaries to combine:
+----------------------------
+%s
+`
+
 // --- Prompt Response Types ---
 
 type InitialGroupingResponse struct {
@@ -173,4 +186,4 @@ var SubGroupingResponseSchema = &genai.Schema{
 			},
 		},
 	},
-}
\ No newline at end of file
+}
diff --git a/internal/digest/view/ai_test.go b/internal/digest/view/ai_test.go
index c9d5edd..ca0711b 100644
--- a/internal/digest/view/ai_test.go
+++ b/internal/digest/view/ai_test.go
@@ -4,8 +4,10 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"miniflux-digest/internal/models"
 	"miniflux-digest/internal/testutil"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -17,7 +19,8 @@ import (
 
 // mockLLMService is a mock implementation of the LLMService for testing.
 type mockLLMService struct {
-	GenerateContentFunc func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error)
+	GenerateContentFunc             func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error)
+	GenerateContentWithResponseFunc func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error
 }
 
 func (m *mockLLMService) GenerateContent(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
@@ -27,6 +30,22 @@ func (m *mockLLMService) GenerateContent(ctx context.Context, prompt string, sch
 	return nil, errors.New("mockLLMService.GenerateContentFunc is not implemented")
 }
 
+func (m *mockLLMService) GenerateContentWithResponse(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+	if m.GenerateContentWithResponseFunc != nil {
+		return m.GenerateContentWithResponseFunc(ctx, prompt, schema, response)
+	}
+	// Default implementation for GenerateContentWithResponse
+	// This will call GenerateContentFunc and then unmarshal the result
+	bytes, err := m.GenerateContent(ctx, prompt, schema)
+	if err != nil {
+		return err
+	}
+	if err := json.Unmarshal(bytes, &response); err != nil {
+		return fmt.Errorf("failed to parse LLM response in mock: %w", err)
+	}
+	return nil
+}
+
 func TestGroupAIEntries(t *testing.T) {
 	entries := []*models.Entry{
 		{ID: 1, Title: "Entry 1", Content: "Content 1", FeedTitle: "Feed 1"},
@@ -48,8 +67,8 @@ func TestGroupAIEntries(t *testing.T) {
 		mockJSON, _ := json.Marshal(mockResp)
 
 		llmService := &mockLLMService{
-			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
-				return mockJSON, nil
+			GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+				return json.Unmarshal(mockJSON, response)
 			},
 		}
 
@@ -72,8 +91,8 @@ func TestGroupAIEntries(t *testing.T) {
 
 	t.Run("llm service error", func(t *testing.T) {
 		llmService := &mockLLMService{
-			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
-				return nil, errors.New("llm error")
+			GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+				return errors.New("llm error")
 			},
 		}
 
@@ -83,8 +102,8 @@ func TestGroupAIEntries(t *testing.T) {
 
 	t.Run("llm returns invalid json", func(t *testing.T) {
 		llmService := &mockLLMService{
-			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
-				return []byte("invalid json"), nil
+			GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+				return json.Unmarshal([]byte(`invalid json`), response)
 			},
 		}
 
@@ -102,7 +121,7 @@ func TestGroupAIEntries(t *testing.T) {
 		var mu sync.Mutex
 
 		llmService := &mockLLMService{
-			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
+			GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
 				mu.Lock()
 				callCount++
 				mu.Unlock()
@@ -123,8 +142,10 @@ func TestGroupAIEntries(t *testing.T) {
 						{Title: "Chunk 2 Group", EntryIDs: []int64{200, 201}},
 					}
 				}
-				mockJSON, _ := json.Marshal(resp)
-				return mockJSON, nil
+				return json.Unmarshal([]byte(func() []byte {
+					b, _ := json.Marshal(resp)
+					return b
+				}()), response)
 			},
 		}
 
@@ -226,58 +247,138 @@ func TestConsolidatePrimaryGroups(t *testing.T) {
 }
 
 func TestProcessPrimaryGroupWithAI(t *testing.T) {
-	pg := &models.PrimaryGroup{
-		ID:    1,
-		Title: "Test Primary Group",
-		Entries: []*models.Entry{
-			{ID: 1, Title: "Entry 1", Content: "Content 1"},
-			{ID: 2, Title: "Entry 2", Content: "Content 2"},
-			{ID: 3, Title: "Entry 3", Content: "Content 3"},
-		},
-	}
-
-	t.Run("happy path", func(t *testing.T) {
-		summaryResp := SummaryResponse{Summary: "This is a summary."}
-		summaryJSON, _ := json.Marshal(summaryResp)
-
-		subGroupingResp := SubGroupingResponse{
-			SubGroups: []struct {
-				Title    string  `json:"title"`
-				EntryIDs []int64 `json:"entry_ids"`
-			}{
-				{Title: "Sub-group 1", EntryIDs: []int64{1, 2}},
+	// --- Test Case 1: Small group (no chunking) ---
+	t.Run("small group - no chunking", func(t *testing.T) {
+		pg := &models.PrimaryGroup{
+			ID:    1,
+			Title: "Small Group",
+			Entries: []*models.Entry{
+				{ID: 1, Title: "E1"},
+				{ID: 2, Title: "E2"},
 			},
 		}
-		subGroupingJSON, _ := json.Marshal(subGroupingResp)
 
 		llmService := &mockLLMService{
 			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
 				if schema == SummaryResponseSchema {
-					return summaryJSON, nil
+					return json.Marshal(SummaryResponse{Summary: "Small group summary"})
 				}
 				if schema == SubGroupingResponseSchema {
-					return subGroupingJSON, nil
+					return json.Marshal(SubGroupingResponse{SubGroups: []struct {
+						Title    string  `json:"title"`
+						EntryIDs []int64 `json:"entry_ids"`
+					}{{Title: "Sub 1", EntryIDs: []int64{1, 2}}}})
 				}
-				return nil, errors.New("unexpected schema in happy path test")
+				return nil, errors.New("unexpected schema")
 			},
 		}
 
 		summary, subGroups, err := ProcessPrimaryGroupWithAI(context.Background(), pg, llmService)
 		assert.NoError(t, err)
-		assert.Equal(t, "This is a summary.", summary)
-		assert.Len(t, subGroups, 2, "Expected 1 sub-group and 1 uncategorized")
-
-		sg1 := subGroups[0]
-		assert.Equal(t, "Sub-group 1", sg1.Title)
-		assert.Len(t, sg1.Entries, 2)
-
-		uncategorized := subGroups[1]
-		assert.Equal(t, "Uncategorized", uncategorized.Title)
-		assert.Len(t, uncategorized.Entries, 1)
-		assert.Equal(t, int64(3), uncategorized.Entries[0].ID)
+		assert.Equal(t, "Small group summary", summary)
+		require.Len(t, subGroups, 1)
+		assert.Equal(t, "Sub 1", subGroups[0].Title)
 	})
 
-	// ... other tests for ProcessPrimaryGroupWithAI are unchanged ...
+	// --- Test Case 2: Large group (with chunking) ---
+	t.Run("large group - with chunking", func(t *testing.T) {
+		var entries []*models.Entry
+		for i := 0; i < 200; i++ { // Will create 2 chunks of 150
+			entries = append(entries, &models.Entry{ID: int64(i)})
+		}
+		pg := &models.PrimaryGroup{ID: 2, Title: "Large Group", Entries: entries}
+
+		llmService := &mockLLMService{
+			GenerateContentWithResponseFunc: func(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+				isLargeChunk := len(prompt) > 10000 // Heuristic to differentiate chunks
+
+				// Summarization
+				if strings.Contains(prompt, "You are an expert at summarizing content") && !strings.Contains(prompt, "overviews of large swaths") { // Partial summary call
+					return json.Unmarshal([]byte(`{"summary": "Partial summary."}`), response)
+				}
+				// Summary of summaries call
+				if strings.Contains(prompt, "You are an expert at creating overviews of large swaths of web updates and web content.") {
+					return json.Unmarshal([]byte(`{"summary": "Final synthesized summary."}`), response)
+				}
+				// Sub-grouping
+				if strings.Contains(prompt, "You are an expert at organizing content") {
+					if isLargeChunk {
+						return json.Unmarshal([]byte(`{"sub_groups": [{"title": "Chunk 1 Sub-Group", "entry_ids": [0, 1]}]}`), response)
+					} else {
+						return json.Unmarshal([]byte(`{"sub_groups": [{"title": "Chunk 2 Sub-Group", "entry_ids": [150, 151]}]}`), response)
+					}
+				}
+				return fmt.Errorf("unexpected prompt: %s", prompt)
+			},
+		}
+
+		summary, subGroups, err := ProcessPrimaryGroupWithAI(context.Background(), pg, llmService)
+		assert.NoError(t, err)
+		assert.Equal(t, "Final synthesized summary.", summary)
+		require.Len(t, subGroups, 3, "Expected 3 sub-groups: 2 from chunks + 1 for ungrouped")
+
+		sg1 := testutil.FindSubGroup(subGroups, "Chunk 1 Sub-Group")
+		require.NotNil(t, sg1)
+		sg2 := testutil.FindSubGroup(subGroups, "Chunk 2 Sub-Group")
+		require.NotNil(t, sg2)
+		uncat := testutil.FindSubGroup(subGroups, "Uncategorized")
+		require.NotNil(t, uncat)
+
+		assert.Len(t, sg1.Entries, 2)
+		assert.Len(t, sg2.Entries, 2)
+		assert.Equal(t, 196, uncat.TotalEntries) // 200 total - 4 grouped
+	})
+
+	// --- Test Case 3: Failure case ---
+	t.Run("large group - with failures", func(t *testing.T) {
+		var entries []*models.Entry
+		for i := 0; i < 200; i++ {
+			entries = append(entries, &models.Entry{ID: int64(i)})
+		}
+		pg := &models.PrimaryGroup{ID: 3, Title: "Failure Group", Entries: entries}
+
+		llmService := &mockLLMService{
+			GenerateContentFunc: func(ctx context.Context, prompt string, schema *genai.Schema) ([]byte, error) {
+				isLargeChunk := len(prompt) > 10000
+
+				// Summarization: one chunk fails
+				if strings.Contains(prompt, "You are an expert at summarizing content") && !strings.Contains(prompt, "overviews of large swaths") { // Partial summary call
+					if isLargeChunk { // First chunk succeeds
+						return json.Marshal(SummaryResponse{Summary: "Partial summary."})
+					}
+					return nil, errors.New("summary failed") // Second chunk fails
+				}
+				// This handles the summary of summaries prompt
+				if strings.Contains(prompt, "You are an expert at creating overviews of large swaths of web updates and web content.") {
+					return json.Marshal(SummaryResponse{Summary: "Final summary from one chunk."})
+				}
+				// Sub-grouping: one chunk fails
+				if strings.Contains(prompt, "You are an expert at organizing content") {
+					if isLargeChunk { // First chunk succeeds
+						return json.Marshal(SubGroupingResponse{SubGroups: []struct {
+							Title    string  `json:"title"`
+							EntryIDs []int64 `json:"entry_ids"`
+						}{{Title: "Good Sub-Group", EntryIDs: []int64{0}}}})}
+					return nil, errors.New("sub-grouping failed") // Second chunk fails
+				}
+				return nil, fmt.Errorf("unexpected prompt: %s", prompt)
+			},
+		}
+
+		summary, subGroups, err := ProcessPrimaryGroupWithAI(context.Background(), pg, llmService)
+		assert.NoError(t, err) // The function itself shouldn't error
+
+		assert.Contains(t, summary, "Final summary from one chunk.")
+		assert.Contains(t, summary, "(Note: 50 entries could not be included") // 200 total - 150 in first chunk = 50 in second
+
+		failedSg := testutil.FindSubGroup(subGroups, "Uncategorized - Processing Failed")
+		require.NotNil(t, failedSg)
+		assert.Len(t, failedSg.Entries, 50)
+
+		goodSg := testutil.FindSubGroup(subGroups, "Good Sub-Group")
+		require.NotNil(t, goodSg)
+		assert.Len(t, goodSg.Entries, 1)
+	})
 }
 
 func TestBuildDigestDataByAI(t *testing.T) {
@@ -377,4 +478,5 @@ func TestBuildDigestDataByAI(t *testing.T) {
 	})
 
 	// ... other fallback tests are similar and should still pass ...
-}
\ No newline at end of file
+}
+
diff --git a/internal/digest/view/date_test.go b/internal/digest/view/date_test.go
index 6f5cc75..a41cd0d 100644
--- a/internal/digest/view/date_test.go
+++ b/internal/digest/view/date_test.go
@@ -41,7 +41,7 @@ func TestDayGrouper_GroupEntries(t *testing.T) {
 		t.Fatalf("Incorrect sub-groups for Category A: %+v", catAGroup)
 	}
 
-	subGroup := testutil.FindSubGroup(catAGroup, "Jan 2, 2024")
+	subGroup := testutil.FindSubGroup(catAGroup.SubGroups, "Jan 2, 2024")
 	if subGroup == nil || len(subGroup.Entries) != 4 {
 		t.Fatalf("Incorrect entries for sub-group: %+v", subGroup)
 	}
diff --git a/internal/llm/gemini.go b/internal/llm/gemini.go
index 582c388..82c6b04 100644
--- a/internal/llm/gemini.go
+++ b/internal/llm/gemini.go
@@ -2,7 +2,9 @@ package llm
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
+	"fmt"
 	"log"
 	"time"
 
@@ -103,4 +105,15 @@ func (s *GeminiService) GenerateContent(ctx context.Context, prompt string, sche
 	}
 
 	return jsonData, nil
+}
+
+func (s *GeminiService) GenerateContentWithResponse(ctx context.Context, prompt string, schema *genai.Schema, response interface{}) error {
+	llmResponseBytes, err := s.GenerateContent(ctx, prompt, schema)
+	if err != nil {
+		return err
+	}
+	if err := json.Unmarshal(llmResponseBytes, &response); err != nil {
+		return fmt.Errorf("failed to parse LLM response: %w", err)
+	}
+	return nil
 }
\ No newline at end of file
diff --git a/internal/llm/util.go b/internal/llm/util.go
new file mode 100644
index 0000000..d349d19
--- /dev/null
+++ b/internal/llm/util.go
@@ -0,0 +1,68 @@
+package llm
+
+import (
+	"log"
+	"strings"
+	"sync"
+)
+
+// WorkerFunc is a generic function type for processing a chunk of items.
+type WorkerFunc[T any, R any] func(chunk []T) (R, error)
+
+// ProcessInChunks is a generic function that processes a slice of items in parallel chunks.
+// It takes a slice of items, a chunk size, and a worker function to process each chunk.
+// It returns a slice of results from the successful chunks and a map of failed items, keyed by the error reason.
+func ProcessInChunks[T any, R any](
+	items []T,
+	chunkSize int,
+	worker func(chunk []T) (R, error),
+) ([]R, map[string][]T) {
+	var wg sync.WaitGroup
+	var mu sync.Mutex
+
+	results := make([]R, 0)
+	failedChunks := make(map[string][]T)
+
+	for i := 0; i < len(items); i += chunkSize {
+		end := min(i+chunkSize, len(items))
+		chunk := items[i:end]
+		wg.Add(1)
+
+		go func(chunk []T) {
+			defer wg.Done()
+
+			result, err := worker(chunk)
+			if err != nil {
+				log.Printf("A chunk failed during parallel processing: %v", err)
+
+				// Determine a simple error key for bucketing failed chunks.
+				errorKey := "Processing Error"
+				if strings.Contains(err.Error(), "DEADLINE_EXCEEDED") {
+					errorKey = "Processing Timeout"
+				} else if strings.Contains(strings.ToLower(err.Error()), "json") {
+					errorKey = "Invalid Response"
+				}
+
+				mu.Lock()
+				failedChunks[errorKey] = append(failedChunks[errorKey], chunk...)
+				mu.Unlock()
+				return
+			}
+
+			mu.Lock()
+			results = append(results, result)
+			mu.Unlock()
+		}(chunk)
+	}
+
+	wg.Wait()
+
+	return results, failedChunks
+}
+
+func min(a, b int) int {
+	if a < b {
+			return a
+		}
+	return b
+}
\ No newline at end of file
diff --git a/internal/llm/util_test.go b/internal/llm/util_test.go
new file mode 100644
index 0000000..4c64563
--- /dev/null
+++ b/internal/llm/util_test.go
@@ -0,0 +1,145 @@
+package llm
+
+import (
+	"errors"
+	"fmt"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestProcessInChunks(t *testing.T) {
+	t.Run("happy path - processes all items", func(t *testing.T) {
+		items := []int{1, 2, 3, 4, 5, 6, 7}
+		chunkSize := 3
+
+		worker := func(chunk []int) (string, error) {
+			var sum int
+			for _, item := range chunk {
+				sum += item
+			}
+			return fmt.Sprintf("sum-%d", sum), nil
+		}
+
+		results, failedItems := ProcessInChunks(items, chunkSize, worker)
+
+		assert.Empty(t, failedItems)
+		assert.Len(t, results, 3) // 3 chunks: (1,2,3), (4,5,6), (7)
+		assert.Contains(t, results, "sum-6")
+		assert.Contains(t, results, "sum-15")
+		assert.Contains(t, results, "sum-7")
+	})
+
+	t.Run("one chunk fails", func(t *testing.T) {
+		items := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+		chunkSize := 4
+
+		worker := func(chunk []int) (string, error) {
+			// Fail the second chunk
+			if chunk[0] == 5 {
+				return "", errors.New("processing error")
+			}
+			return "success", nil
+		}
+
+		results, failedChunks := ProcessInChunks(items, chunkSize, worker)
+
+		assert.Len(t, results, 2) // Chunks 1 and 3 should succeed
+		assert.Len(t, failedChunks, 1) // One failure reason
+		assert.Contains(t, failedChunks, "Processing Error")
+		assert.Len(t, failedChunks["Processing Error"], 4) // Chunk 2 (items 5,6,7,8) should fail
+		assert.Equal(t, 5, failedChunks["Processing Error"][0])
+	})
+
+	t.Run("all chunks fail", func(t *testing.T) {
+		items := []int{1, 2, 3, 4}
+		chunkSize := 2
+
+		worker := func(chunk []int) (string, error) {
+			return "", errors.New("always fail")
+		}
+
+		results, failedChunks := ProcessInChunks(items, chunkSize, worker)
+
+		assert.Empty(t, results)
+		assert.Len(t, failedChunks, 1)
+		assert.Len(t, failedChunks["Processing Error"], 4)
+	})
+
+	t.Run("items less than chunk size", func(t *testing.T) {
+		items := []int{1, 2}
+		chunkSize := 5
+
+		worker := func(chunk []int) (string, error) {
+			return "success", nil
+		}
+
+		results, failedItems := ProcessInChunks(items, chunkSize, worker)
+
+		assert.Empty(t, failedItems)
+		assert.Len(t, results, 1)
+	})
+
+	t.Run("zero items", func(t *testing.T) {
+		items := []int{}
+		chunkSize := 5
+
+		worker := func(chunk []int) (string, error) {
+			t.Fatal("worker should not be called for zero items")
+			return "", nil
+		}
+
+		results, failedItems := ProcessInChunks(items, chunkSize, worker)
+
+		assert.Empty(t, failedItems)
+		assert.Empty(t, results)
+	})
+
+	t.Run("exact multiple of chunk size", func(t *testing.T) {
+		items := []int{1, 2, 3, 4, 5, 6}
+		chunkSize := 3
+
+		worker := func(chunk []int) (string, error) {
+			return "success", nil
+		}
+
+		results, failedItems := ProcessInChunks(items, chunkSize, worker)
+
+		assert.Empty(t, failedItems)
+		assert.Len(t, results, 2)
+	})
+
+	t.Run("thread safety", func(t *testing.T) {
+		numItems := 1000
+		items := make([]int, numItems)
+		for i := 0; i < numItems; i++ {
+			items[i] = i
+		}
+		chunkSize := 10
+
+		var mu sync.Mutex
+		var callCount int
+
+		worker := func(chunk []int) (int, error) {
+			mu.Lock()
+			callCount++
+			// Fail every 10th chunk
+			if callCount%10 == 0 {
+				mu.Unlock()
+				return 0, errors.New("failed")
+			}
+			mu.Unlock()
+			return len(chunk), nil
+		}
+
+		results, failedChunks := ProcessInChunks(items, chunkSize, worker)
+
+		numChunks := numItems / chunkSize
+		numFailedChunks := numChunks / 10
+		numSuccessfulChunks := numChunks - numFailedChunks
+
+		assert.Len(t, results, numSuccessfulChunks)
+		assert.Len(t, failedChunks["Processing Error"], numFailedChunks*chunkSize)
+	})
+}
\ No newline at end of file
diff --git a/internal/testutil/mocks.go b/internal/testutil/mocks.go
index 3467544..a80d2e2 100644
--- a/internal/testutil/mocks.go
+++ b/internal/testutil/mocks.go
@@ -79,18 +79,18 @@ func (m *MockDigestService) BuildDigestData(category *miniflux.Category, entries
 
 // Helper functions for tests
 func FindPrimaryGroup(groups []*models.PrimaryGroupDigestData, title string) *models.PrimaryGroupDigestData {
-	for _, group := range groups {
-		if group.Title == title {
-			return group
+	for _, g := range groups {
+		if g.Title == title {
+			return g
 		}
 	}
 	return nil
 }
 
-func FindSubGroup(primaryGroup *models.PrimaryGroupDigestData, title string) *models.EntryGroup {
-	for _, group := range primaryGroup.SubGroups {
-		if group.Title == title {
-			return group
+func FindSubGroup(groups []*models.EntryGroup, title string) *models.EntryGroup {
+	for _, g := range groups {
+		if g.Title == title {
+			return g
 		}
 	}
 	return nil