Merge branch 'CJackHwang:main' into main

internal/deepseek/client/client_upload.go

@@ -23,6 +23,7 @@ type UploadFileRequest struct {
 	Filename    string
 	ContentType string
 	Purpose     string
+	ModelType   string
 	Data        []byte
 }
 
@@ -54,6 +55,7 @@ func (c *Client) UploadFile(ctx context.Context, a *auth.RequestAuth, req Upload
 		contentType = "application/octet-stream"
 	}
 	purpose := strings.TrimSpace(req.Purpose)
+	modelType := strings.ToLower(strings.TrimSpace(req.ModelType))
 	body, contentTypeHeader, err := buildUploadMultipartBody(filename, contentType, req.Data)
 	if err != nil {
 		return nil, err
@@ -64,6 +66,9 @@ func (c *Client) UploadFile(ctx context.Context, a *auth.RequestAuth, req Upload
 		"purpose":      purpose,
 		"bytes":        len(req.Data),
 	}
+	if modelType != "" {
+		capturePayload["model_type"] = modelType
+	}
 	captureSession := c.capture.Start("deepseek_upload_file", dsprotocol.DeepSeekUploadFileURL, a.AccountID, capturePayload)
 	attempts := 0
 	refreshed := false
@@ -81,6 +86,9 @@ func (c *Client) UploadFile(ctx context.Context, a *auth.RequestAuth, req Upload
 		}
 		headers := c.authHeaders(a.DeepSeekToken)
 		headers["Content-Type"] = contentTypeHeader
+		if modelType != "" {
+			headers["x-model-type"] = modelType
+		}
 		headers["x-ds-pow-response"] = powHeader
 		headers["x-file-size"] = strconv.Itoa(len(req.Data))
 		headers["x-thinking-enabled"] = "1"

internal/deepseek/client/client_upload_test.go

@@ -82,6 +82,7 @@ func TestUploadFileUsesUploadTargetPowAndMultipartHeaders(t *testing.T) {
 	var seenTargetPath string
 	var seenContentType string
 	var seenFileSize string
+	var seenModelType string
 	var seenBody string
 	call := 0
 	client := &Client{
@@ -96,6 +97,7 @@ func TestUploadFileUsesUploadTargetPowAndMultipartHeaders(t *testing.T) {
 				seenPow = req.Header.Get("x-ds-pow-response")
 				seenContentType = req.Header.Get("Content-Type")
 				seenFileSize = req.Header.Get("x-file-size")
+				seenModelType = req.Header.Get("x-model-type")
 				seenBody = string(bodyBytes)
 				return &http.Response{StatusCode: http.StatusOK, Header: make(http.Header), Body: io.NopCloser(strings.NewReader(uploadResponse)), Request: req}, nil
 			default:
@@ -112,6 +114,7 @@ func TestUploadFileUsesUploadTargetPowAndMultipartHeaders(t *testing.T) {
 		Filename:    "demo.txt",
 		ContentType: "text/plain",
 		Purpose:     "assistants",
+		ModelType:   "vision",
 		Data:        []byte("hello"),
 	}, 1)
 	if err != nil {
@@ -140,6 +143,9 @@ func TestUploadFileUsesUploadTargetPowAndMultipartHeaders(t *testing.T) {
 	if seenFileSize != "5" {
 		t.Fatalf("expected x-file-size=5, got %q", seenFileSize)
 	}
+	if seenModelType != "vision" {
+		t.Fatalf("expected x-model-type=vision, got %q", seenModelType)
+	}
 	if !strings.HasPrefix(seenContentType, "multipart/form-data; boundary=") {
 		t.Fatalf("expected multipart content type, got %q", seenContentType)
 	}

internal/deepseek/protocol/constants.go

@@ -159,6 +159,6 @@ func toStringSet(in []string) map[string]struct{} {
 
 const (
 	KeepAliveTimeout  = 5
-	StreamIdleTimeout = 90
-	MaxKeepaliveCount = 10
+	StreamIdleTimeout = 300
+	MaxKeepaliveCount = 40
 )

internal/httpapi/claude/handler_messages.go

@@ -3,12 +3,14 @@ package claude
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"io"
 	"net/http"
 	"net/http/httptest"
 	"strings"
 
 	"ds2api/internal/config"
+	"ds2api/internal/httpapi/requestbody"
 	streamengine "ds2api/internal/stream"
 	"ds2api/internal/translatorcliproxy"
 	"ds2api/internal/util"
@@ -33,7 +35,11 @@ func (h *Handler) Messages(w http.ResponseWriter, r *http.Request) {
 func (h *Handler) proxyViaOpenAI(w http.ResponseWriter, r *http.Request, store ConfigReader) bool {
 	raw, err := io.ReadAll(r.Body)
 	if err != nil {
-		writeClaudeError(w, http.StatusBadRequest, "invalid body")
+		if errors.Is(err, requestbody.ErrInvalidUTF8Body) {
+			writeClaudeError(w, http.StatusBadRequest, "invalid json")
+		} else {
+			writeClaudeError(w, http.StatusBadRequest, "invalid body")
+		}
 		return true
 	}
 	var req map[string]any

internal/httpapi/gemini/handler_generate.go

@@ -2,8 +2,8 @@ package gemini
 
 import (
 	"bytes"
-	"ds2api/internal/toolcall"
 	"encoding/json"
+	"errors"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -11,7 +11,9 @@ import (
 
 	"github.com/go-chi/chi/v5"
 
+	"ds2api/internal/httpapi/requestbody"
 	"ds2api/internal/sse"
+	"ds2api/internal/toolcall"
 	"ds2api/internal/translatorcliproxy"
 	"ds2api/internal/util"
 
@@ -32,7 +34,11 @@ func (h *Handler) handleGenerateContent(w http.ResponseWriter, r *http.Request,
 func (h *Handler) proxyViaOpenAI(w http.ResponseWriter, r *http.Request, stream bool) bool {
 	raw, err := io.ReadAll(r.Body)
 	if err != nil {
-		writeGeminiError(w, http.StatusBadRequest, "invalid body")
+		if errors.Is(err, requestbody.ErrInvalidUTF8Body) {
+			writeGeminiError(w, http.StatusBadRequest, "invalid json")
+		} else {
+			writeGeminiError(w, http.StatusBadRequest, "invalid body")
+		}
 		return true
 	}
 	routeModel := strings.TrimSpace(chi.URLParam(r, "model"))

internal/httpapi/openai/chat/chat_history_test.go

@@ -311,16 +311,16 @@ func TestChatCompletionsCurrentInputFilePersistsNeutralPrompt(t *testing.T) {
 	if len(ds.uploadCalls) != 1 {
 		t.Fatalf("expected current input upload to happen, got %d", len(ds.uploadCalls))
 	}
-	if ds.uploadCalls[0].Filename != "history.txt" {
-		t.Fatalf("expected history.txt upload, got %q", ds.uploadCalls[0].Filename)
+	if ds.uploadCalls[0].Filename != "DS2API_HISTORY.txt" {
+		t.Fatalf("expected DS2API_HISTORY.txt upload, got %q", ds.uploadCalls[0].Filename)
 	}
 	if full.HistoryText != string(ds.uploadCalls[0].Data) {
 		t.Fatalf("expected uploaded current input file to be persisted in history text")
 	}
 	if len(full.Messages) != 1 {
-		t.Fatalf("expected neutral prompt to be the only persisted message, got %#v", full.Messages)
+		t.Fatalf("expected continuation prompt to be the only persisted message, got %#v", full.Messages)
 	}
-	if !strings.Contains(full.Messages[0].Content, "Answer the latest user request directly.") {
-		t.Fatalf("expected neutral prompt to be persisted, got %#v", full.Messages[0])
+	if !strings.Contains(full.Messages[0].Content, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") {
+		t.Fatalf("expected continuation prompt to be persisted, got %#v", full.Messages[0])
 	}
 }

internal/httpapi/openai/chat/chat_stream_runtime.go

@@ -173,6 +173,15 @@ func (s *chatStreamRuntime) sendFailedChunk(status int, message, code string) {
 	s.sendDone()
 }
 
+func (s *chatStreamRuntime) markContextCancelled() {
+	s.finalErrorStatus = 499
+	s.finalErrorMessage = "request context cancelled"
+	s.finalErrorCode = string(streamengine.StopReasonContextCancelled)
+	s.finalThinking = s.thinking.String()
+	s.finalText = cleanVisibleOutput(s.text.String(), s.stripReferenceMarkers)
+	s.finalFinishReason = string(streamengine.StopReasonContextCancelled)
+}
+
 func (s *chatStreamRuntime) resetStreamToolCallState() {
 	s.streamToolCallIDs = map[int]string{}
 	s.streamToolNames = map[int]string{}

internal/httpapi/openai/chat/empty_retry_runtime.go

@@ -247,11 +247,15 @@ func (h *Handler) consumeChatStreamAttempt(r *http.Request, resp *http.Response,
 			}
 		},
 		OnContextDone: func() {
+			streamRuntime.markContextCancelled()
 			if historySession != nil {
 				historySession.stopped(streamRuntime.thinking.String(), streamRuntime.text.String(), string(streamengine.StopReasonContextCancelled))
 			}
 		},
 	})
+	if streamRuntime.finalErrorCode == string(streamengine.StopReasonContextCancelled) {
+		return true, false
+	}
 	terminalWritten := streamRuntime.finalize(finalReason, allowDeferEmpty && finalReason != "content_filter")
 	if terminalWritten {
 		recordChatStreamHistory(streamRuntime, historySession)
@@ -283,6 +287,10 @@ func logChatStreamTerminal(streamRuntime *chatStreamRuntime, attempts int) {
 	if attempts > 0 {
 		source = "synthetic_retry"
 	}
+	if streamRuntime.finalErrorCode == string(streamengine.StopReasonContextCancelled) {
+		config.Logger.Info("[openai_empty_retry] terminal cancelled", "surface", "chat.completions", "stream", true, "retry_attempts", attempts, "error_code", streamRuntime.finalErrorCode)
+		return
+	}
 	if streamRuntime.finalErrorMessage != "" {
 		config.Logger.Info("[openai_empty_retry] terminal empty output", "surface", "chat.completions", "stream", true, "retry_attempts", attempts, "success_source", "none", "error_code", streamRuntime.finalErrorCode)
 		return

internal/httpapi/openai/chat/empty_retry_runtime_test.go

@@ -0,0 +1,85 @@
+package chat
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"ds2api/internal/chathistory"
+	"ds2api/internal/stream"
+)
+
+func TestConsumeChatStreamAttemptMarksContextCancelledState(t *testing.T) {
+	historyStore := newTestChatHistoryStore(t)
+	entry, err := historyStore.Start(chathistory.StartParams{
+		CallerID:  "caller:test",
+		Model:     "deepseek-v4-flash",
+		Stream:    true,
+		UserInput: "hello",
+	})
+	if err != nil {
+		t.Fatalf("start history failed: %v", err)
+	}
+	session := &chatHistorySession{
+		store:       historyStore,
+		entryID:     entry.ID,
+		startedAt:   time.Now(),
+		lastPersist: time.Now(),
+		finalPrompt: "prompt",
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", nil).WithContext(ctx)
+	rec := httptest.NewRecorder()
+	streamRuntime := newChatStreamRuntime(
+		rec,
+		http.NewResponseController(rec),
+		true,
+		"cid-cancelled",
+		time.Now().Unix(),
+		"deepseek-v4-flash",
+		"prompt",
+		false,
+		false,
+		true,
+		nil,
+		nil,
+		false,
+		false,
+	)
+	resp := makeOpenAISSEHTTPResponse(
+		`data: {"p":"response/content","v":"hello"}`,
+		`data: [DONE]`,
+	)
+
+	h := &Handler{}
+	terminalWritten, retryable := h.consumeChatStreamAttempt(req, resp, streamRuntime, "text", false, session, true)
+	if !terminalWritten || retryable {
+		t.Fatalf("expected cancelled attempt to terminate without retry, got terminalWritten=%v retryable=%v", terminalWritten, retryable)
+	}
+	if got, want := streamRuntime.finalErrorCode, string(stream.StopReasonContextCancelled); got != want {
+		t.Fatalf("expected cancelled final error code %q, got %q", want, got)
+	}
+	if streamRuntime.finalErrorMessage == "" {
+		t.Fatalf("expected cancelled final error message to be preserved")
+	}
+
+	snapshot, err := historyStore.Snapshot()
+	if err != nil {
+		t.Fatalf("snapshot failed: %v", err)
+	}
+	if len(snapshot.Items) != 1 {
+		t.Fatalf("expected one history item, got %d", len(snapshot.Items))
+	}
+	full, err := historyStore.Get(snapshot.Items[0].ID)
+	if err != nil {
+		t.Fatalf("get detail failed: %v", err)
+	}
+	if full.Status != "stopped" {
+		t.Fatalf("expected stopped status, got %#v", full)
+	}
+}

internal/httpapi/openai/chat/vercel_prepare_test.go

@@ -130,8 +130,8 @@ func TestHandleVercelStreamPrepareAppliesCurrentInputFile(t *testing.T) {
 		t.Fatalf("expected payload object, got %#v", body["payload"])
 	}
 	promptText, _ := payload["prompt"].(string)
-	if !strings.Contains(promptText, "Answer the latest user request directly.") {
-		t.Fatalf("expected neutral prompt, got %s", promptText)
+	if !strings.Contains(promptText, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") {
+		t.Fatalf("expected continuation prompt, got %s", promptText)
 	}
 	if strings.Contains(promptText, "first user turn") || strings.Contains(promptText, "latest user turn") {
 		t.Fatalf("expected original turns hidden from prompt, got %s", promptText)

internal/httpapi/openai/file_inline_upload_test.go

@@ -94,6 +94,9 @@ func TestPreprocessInlineFileInputsReplacesDataURLAndCollectsRefFileIDs(t *testi
 	if len(ds.uploadCalls) != 1 {
 		t.Fatalf("expected 1 upload, got %d", len(ds.uploadCalls))
 	}
+	if ds.uploadCalls[0].ModelType != "default" {
+		t.Fatalf("expected default model type when request omits model, got %q", ds.uploadCalls[0].ModelType)
+	}
 	if ds.lastCtx != ctx {
 		t.Fatalf("expected upload to use request context")
 	}
@@ -149,7 +152,7 @@ func TestPreprocessInlineFileInputsDeduplicatesIdenticalPayloads(t *testing.T) {
 func TestChatCompletionsUploadsInlineFilesBeforeCompletion(t *testing.T) {
 	ds := &inlineUploadDSStub{}
 	h := &openAITestSurface{Store: mockOpenAIConfig{wideInput: true}, Auth: streamStatusAuthStub{}, DS: ds}
-	reqBody := `{"model":"deepseek-v4-flash","messages":[{"role":"user","content":[{"type":"input_text","text":"hi"},{"type":"image_url","image_url":{"url":"data:image/png;base64,QUJDRA=="}}]}],"stream":false}`
+	reqBody := `{"model":"deepseek-v4-vision","messages":[{"role":"user","content":[{"type":"input_text","text":"hi"},{"type":"image_url","image_url":{"url":"data:image/png;base64,QUJDRA=="}}]}],"stream":false}`
 	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", strings.NewReader(reqBody))
 	req.Header.Set("Authorization", "Bearer direct-token")
 	req.Header.Set("Content-Type", "application/json")
@@ -163,6 +166,9 @@ func TestChatCompletionsUploadsInlineFilesBeforeCompletion(t *testing.T) {
 	if len(ds.uploadCalls) != 1 {
 		t.Fatalf("expected 1 upload call, got %d", len(ds.uploadCalls))
 	}
+	if ds.uploadCalls[0].ModelType != "vision" {
+		t.Fatalf("expected vision model type for vision request, got %q", ds.uploadCalls[0].ModelType)
+	}
 	if ds.completionReq == nil {
 		t.Fatal("expected completion payload to be captured")
 	}
@@ -177,7 +183,7 @@ func TestResponsesUploadsInlineFilesBeforeCompletion(t *testing.T) {
 	h := &openAITestSurface{Store: mockOpenAIConfig{wideInput: true}, Auth: streamStatusAuthStub{}, DS: ds}
 	r := chi.NewRouter()
 	registerOpenAITestRoutes(r, h)
-	reqBody := `{"model":"deepseek-v4-flash","input":[{"role":"user","content":[{"type":"input_text","text":"hi"},{"type":"input_image","image_url":{"url":"data:image/png;base64,QUJDRA=="}}]}],"stream":false}`
+	reqBody := `{"model":"deepseek-v4-pro","input":[{"role":"user","content":[{"type":"input_text","text":"hi"},{"type":"input_image","image_url":{"url":"data:image/png;base64,QUJDRA=="}}]}],"stream":false}`
 	req := httptest.NewRequest(http.MethodPost, "/v1/responses", strings.NewReader(reqBody))
 	req.Header.Set("Authorization", "Bearer direct-token")
 	req.Header.Set("Content-Type", "application/json")
@@ -191,6 +197,9 @@ func TestResponsesUploadsInlineFilesBeforeCompletion(t *testing.T) {
 	if len(ds.uploadCalls) != 1 {
 		t.Fatalf("expected 1 upload call, got %d", len(ds.uploadCalls))
 	}
+	if ds.uploadCalls[0].ModelType != "expert" {
+		t.Fatalf("expected expert model type for pro request, got %q", ds.uploadCalls[0].ModelType)
+	}
 	refIDs, _ := ds.completionReq["ref_file_ids"].([]any)
 	if len(refIDs) != 1 || refIDs[0] != "file-inline-1" {
 		t.Fatalf("unexpected completion ref_file_ids: %#v", ds.completionReq["ref_file_ids"])

internal/httpapi/openai/files/file_inline_upload.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 
 	"ds2api/internal/auth"
+	"ds2api/internal/config"
 	dsclient "ds2api/internal/deepseek/client"
 	"ds2api/internal/httpapi/openai/shared"
 	"ds2api/internal/promptcompat"
@@ -42,6 +43,7 @@ type inlineUploadState struct {
 	ctx             context.Context
 	handler         *Handler
 	auth            *auth.RequestAuth
+	modelType       string
 	uploadedByID    map[string]string
 	uploadCount     int
 	inlineFileBytes int
@@ -58,10 +60,19 @@ func (h *Handler) PreprocessInlineFileInputs(ctx context.Context, a *auth.Reques
 	if h == nil || h.DS == nil || len(req) == 0 {
 		return nil
 	}
+	modelType := "default"
+	if requestedModel, ok := req["model"].(string); ok {
+		if resolvedModel, ok := config.ResolveModel(h.Store, requestedModel); ok {
+			if resolvedType, ok := config.GetModelType(resolvedModel); ok {
+				modelType = resolvedType
+			}
+		}
+	}
 	state := &inlineUploadState{
 		ctx:          ctx,
 		handler:      h,
 		auth:         a,
+		modelType:    modelType,
 		uploadedByID: map[string]string{},
 	}
 	for _, key := range []string{"messages", "input", "attachments"} {
@@ -174,6 +185,7 @@ func (s *inlineUploadState) uploadInlineFile(file inlineDecodedFile) (string, er
 	result, err := s.handler.DS.UploadFile(s.ctx, s.auth, dsclient.UploadFileRequest{
 		Filename:    file.Filename,
 		ContentType: contentType,
+		ModelType:   s.modelType,
 		Data:        file.Data,
 	}, 3)
 	if err != nil {

internal/httpapi/openai/files/handler_files.go

@@ -8,6 +8,7 @@ import (
 
 	"ds2api/internal/auth"
 	"ds2api/internal/chathistory"
+	"ds2api/internal/config"
 	dsclient "ds2api/internal/deepseek/client"
 	"ds2api/internal/httpapi/openai/shared"
 )
@@ -66,10 +67,12 @@ func (h *Handler) UploadFile(w http.ResponseWriter, r *http.Request) {
 	if contentType == "" && len(data) > 0 {
 		contentType = http.DetectContentType(data)
 	}
+	modelType := resolveUploadModelType(h.Store, r)
 	result, err := h.DS.UploadFile(r.Context(), a, dsclient.UploadFileRequest{
 		Filename:    header.Filename,
 		ContentType: contentType,
 		Purpose:     strings.TrimSpace(r.FormValue("purpose")),
+		ModelType:   modelType,
 		Data:        data,
 	}, 3)
 	if err != nil {
@@ -82,6 +85,32 @@ func (h *Handler) UploadFile(w http.ResponseWriter, r *http.Request) {
 	shared.WriteJSON(w, http.StatusOK, buildOpenAIFileObject(result))
 }
 
+func resolveUploadModelType(store shared.ConfigReader, r *http.Request) string {
+	for _, candidate := range []string{r.FormValue("model_type"), r.Header.Get("X-Model-Type")} {
+		if modelType := normalizeUploadModelType(candidate); modelType != "" {
+			return modelType
+		}
+	}
+	requestedModel := strings.TrimSpace(r.FormValue("model"))
+	if requestedModel != "" {
+		if resolvedModel, ok := config.ResolveModel(store, requestedModel); ok {
+			if modelType, ok := config.GetModelType(resolvedModel); ok {
+				return modelType
+			}
+		}
+	}
+	return "default"
+}
+
+func normalizeUploadModelType(raw string) string {
+	switch strings.ToLower(strings.TrimSpace(raw)) {
+	case "default", "expert", "vision":
+		return strings.ToLower(strings.TrimSpace(raw))
+	default:
+		return ""
+	}
+}
+
 func buildOpenAIFileObject(result *dsclient.UploadFileResult) map[string]any {
 	if result == nil {
 		obj := map[string]any{

internal/httpapi/openai/files_route_test.go

@@ -77,7 +77,7 @@ func (m *filesRouteDSStub) DeleteAllSessionsForToken(_ context.Context, _ string
 	return nil
 }
 
-func newMultipartUploadRequest(t *testing.T, purpose string, filename string, data []byte) *http.Request {
+func newMultipartUploadRequest(t *testing.T, purpose string, filename string, data []byte, model string) *http.Request {
 	t.Helper()
 	var body bytes.Buffer
 	writer := multipart.NewWriter(&body)
@@ -86,6 +86,11 @@ func newMultipartUploadRequest(t *testing.T, purpose string, filename string, da
 			t.Fatalf("write purpose failed: %v", err)
 		}
 	}
+	if model != "" {
+		if err := writer.WriteField("model", model); err != nil {
+			t.Fatalf("write model failed: %v", err)
+		}
+	}
 	part, err := writer.CreateFormFile("file", filename)
 	if err != nil {
 		t.Fatalf("create form file failed: %v", err)
@@ -108,7 +113,7 @@ func TestFilesRouteUploadSuccess(t *testing.T) {
 	r := chi.NewRouter()
 	registerOpenAITestRoutes(r, h)
 
-	req := newMultipartUploadRequest(t, "assistants", "notes.txt", []byte("hello world"))
+	req := newMultipartUploadRequest(t, "assistants", "notes.txt", []byte("hello world"), "deepseek-v4-vision")
 	rec := httptest.NewRecorder()
 	r.ServeHTTP(rec, req)
 
@@ -121,6 +126,9 @@ func TestFilesRouteUploadSuccess(t *testing.T) {
 	if ds.lastReq.Purpose != "assistants" {
 		t.Fatalf("expected purpose assistants, got %q", ds.lastReq.Purpose)
 	}
+	if ds.lastReq.ModelType != "vision" {
+		t.Fatalf("expected vision model type, got %q", ds.lastReq.ModelType)
+	}
 	if string(ds.lastReq.Data) != "hello world" {
 		t.Fatalf("unexpected uploaded data: %q", string(ds.lastReq.Data))
 	}
@@ -145,7 +153,7 @@ func TestFilesRouteUploadIncludesAccountIDForManagedAccount(t *testing.T) {
 	r := chi.NewRouter()
 	registerOpenAITestRoutes(r, h)
 
-	req := newMultipartUploadRequest(t, "assistants", "notes.txt", []byte("hello world"))
+	req := newMultipartUploadRequest(t, "assistants", "notes.txt", []byte("hello world"), "deepseek-v4-vision")
 	rec := httptest.NewRecorder()
 	r.ServeHTTP(rec, req)
 

internal/httpapi/openai/history/current_input_file.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"ds2api/internal/auth"
+	"ds2api/internal/config"
 	dsclient "ds2api/internal/deepseek/client"
 	"ds2api/internal/httpapi/openai/shared"
 	"ds2api/internal/promptcompat"
@@ -35,10 +36,15 @@ func (s Service) ApplyCurrentInputFile(ctx context.Context, a *auth.RequestAuth,
 	if strings.TrimSpace(fileText) == "" {
 		return stdReq, errors.New("current user input file produced empty transcript")
 	}
+	modelType := "default"
+	if resolvedType, ok := config.GetModelType(stdReq.ResolvedModel); ok {
+		modelType = resolvedType
+	}
 	result, err := s.DS.UploadFile(ctx, a, dsclient.UploadFileRequest{
 		Filename:    currentInputFilename,
 		ContentType: currentInputContentType,
 		Purpose:     currentInputPurpose,
+		ModelType:   modelType,
 		Data:        []byte(fileText),
 	}, 3)
 	if err != nil {
@@ -62,7 +68,7 @@ func (s Service) ApplyCurrentInputFile(ctx context.Context, a *auth.RequestAuth,
 	stdReq.RefFileIDs = prependUniqueRefFileID(stdReq.RefFileIDs, fileID)
 	stdReq.FinalPrompt, stdReq.ToolNames = promptcompat.BuildOpenAIPrompt(messages, stdReq.ToolsRaw, "", stdReq.ToolChoice, stdReq.Thinking)
 	// Token accounting must reflect the actual downstream context:
-	// the uploaded history.txt file content + the neutral live prompt.
+	// the uploaded DS2API_HISTORY.txt file content + the continuation live prompt.
 	stdReq.PromptTokenText = fileText + "\n" + stdReq.FinalPrompt
 	return stdReq, nil
 }
@@ -87,5 +93,5 @@ func latestUserInputForFile(messages []any) (int, string) {
 }
 
 func currentInputFilePrompt() string {
-	return "The current request and prior conversation context have already been provided. Answer the latest user request directly."
+	return "Continue from the latest state in the attached DS2API_HISTORY.txt context. Treat it as the current working state and answer the latest user request directly."
 }

internal/httpapi/openai/history_split_test.go

@@ -61,26 +61,33 @@ func (streamStatusManagedAuthStub) DetermineCaller(_ *http.Request) (*auth.Reque
 
 func (streamStatusManagedAuthStub) Release(_ *auth.RequestAuth) {}
 
-func TestBuildOpenAICurrentInputContextTranscriptUsesInjectedFileWrapper(t *testing.T) {
+func TestBuildOpenAICurrentInputContextTranscriptUsesNumberedHistorySections(t *testing.T) {
 	_, historyMessages := splitOpenAIHistoryMessages(historySplitTestMessages(), 1)
 	transcript := buildOpenAICurrentInputContextTranscript(historyMessages)
 
 	if strings.Contains(transcript, "[file content end]") || strings.Contains(transcript, "[file content begin]") || strings.Contains(transcript, "[file name]:") {
-		t.Fatalf("expected plain transcript without file wrapper tags, got %q", transcript)
+		t.Fatalf("expected transcript without file wrapper tags, got %q", transcript)
 	}
-	if !strings.Contains(transcript, "<｜begin▁of▁sentence｜>") {
-		t.Fatalf("expected serialized conversation markers, got %q", transcript)
+	if !strings.Contains(transcript, "# DS2API_HISTORY.txt") {
+		t.Fatalf("expected history transcript header, got %q", transcript)
 	}
-	if !strings.Contains(transcript, "first user turn") || !strings.Contains(transcript, "tool result") {
-		t.Fatalf("expected historical turns preserved, got %q", transcript)
+	if !strings.Contains(transcript, "Prior conversation history and tool progress.") {
+		t.Fatalf("expected history transcript description, got %q", transcript)
 	}
-	if !strings.Contains(transcript, "[reasoning_content]") || !strings.Contains(transcript, "hidden reasoning") {
-		t.Fatalf("expected reasoning block preserved, got %q", transcript)
+	for _, want := range []string{
+		"=== 1. USER ===",
+		"=== 2. ASSISTANT ===",
+		"=== 3. TOOL ===",
+		"first user turn",
+		"tool result",
+		"[reasoning_content]",
+		"hidden reasoning",
+		"<|DSML|tool_calls>",
+	} {
+		if !strings.Contains(transcript, want) {
+			t.Fatalf("expected transcript to contain %q, got %q", want, transcript)
+		}
 	}
-	if !strings.Contains(transcript, "<|DSML|tool_calls>") {
-		t.Fatalf("expected tool calls preserved, got %q", transcript)
-	}
-
 }
 
 func TestSplitOpenAIHistoryMessagesUsesLatestUserTurn(t *testing.T) {
@@ -220,7 +227,7 @@ func TestApplyCurrentInputFileDisabledPassThrough(t *testing.T) {
 		DS: ds,
 	}
 	req := map[string]any{
-		"model":    "deepseek-v4-flash",
+		"model":    "deepseek-v4-vision",
 		"messages": historySplitTestMessages(),
 	}
 	stdReq, err := promptcompat.NormalizeOpenAIChatRequest(h.Store, req, "")
@@ -243,7 +250,7 @@ func TestApplyCurrentInputFileDisabledPassThrough(t *testing.T) {
 	}
 }
 
-func TestApplyCurrentInputFileUploadsFirstTurnWithInjectedWrapper(t *testing.T) {
+func TestApplyCurrentInputFileUploadsFirstTurnWithNumberedHistoryTranscript(t *testing.T) {
 	ds := &inlineUploadDSStub{}
 	h := &openAITestSurface{
 		Store: mockOpenAIConfig{
@@ -273,15 +280,21 @@ func TestApplyCurrentInputFileUploadsFirstTurnWithInjectedWrapper(t *testing.T)
 		t.Fatalf("expected 1 current input upload, got %d", len(ds.uploadCalls))
 	}
 	upload := ds.uploadCalls[0]
-	if upload.Filename != "history.txt" {
+	if upload.Filename != "DS2API_HISTORY.txt" {
 		t.Fatalf("unexpected upload filename: %q", upload.Filename)
 	}
 	uploadedText := string(upload.Data)
 	if strings.Contains(uploadedText, "[file content end]") || strings.Contains(uploadedText, "[file content begin]") || strings.Contains(uploadedText, "[file name]:") {
 		t.Fatalf("expected uploaded transcript without file wrapper tags, got %q", uploadedText)
 	}
-	if !strings.Contains(uploadedText, "<｜begin▁of▁sentence｜><｜User｜>first turn content that is long enough") {
-		t.Fatalf("expected serialized current user turn markers, got %q", uploadedText)
+	for _, want := range []string{
+		"# DS2API_HISTORY.txt",
+		"=== 1. USER ===",
+		"first turn content that is long enough",
+	} {
+		if !strings.Contains(uploadedText, want) {
+			t.Fatalf("expected uploaded transcript to contain %q, got %q", want, uploadedText)
+		}
 	}
 	if !strings.Contains(uploadedText, promptcompat.ThinkingInjectionMarker) {
 		t.Fatalf("expected thinking injection in current input file, got %q", uploadedText)
@@ -290,11 +303,11 @@ func TestApplyCurrentInputFileUploadsFirstTurnWithInjectedWrapper(t *testing.T)
 	if strings.Contains(out.FinalPrompt, "first turn content that is long enough") {
 		t.Fatalf("expected current input text to be replaced in live prompt, got %s", out.FinalPrompt)
 	}
-	if strings.Contains(out.FinalPrompt, "CURRENT_USER_INPUT.txt") || strings.Contains(out.FinalPrompt, "history.txt") || strings.Contains(out.FinalPrompt, "Read that file") {
+	if strings.Contains(out.FinalPrompt, "CURRENT_USER_INPUT.txt") || strings.Contains(out.FinalPrompt, "Read that file") {
 		t.Fatalf("expected live prompt not to instruct file reads, got %s", out.FinalPrompt)
 	}
-	if !strings.Contains(out.FinalPrompt, "Answer the latest user request directly.") {
-		t.Fatalf("expected neutral continuation instruction in live prompt, got %s", out.FinalPrompt)
+	if !strings.Contains(out.FinalPrompt, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") {
+		t.Fatalf("expected continuation-oriented prompt in live prompt, got %s", out.FinalPrompt)
 	}
 	if len(out.RefFileIDs) != 1 || out.RefFileIDs[0] != "file-inline-1" {
 		t.Fatalf("expected current input file id in ref_file_ids, got %#v", out.RefFileIDs)
@@ -302,6 +315,9 @@ func TestApplyCurrentInputFileUploadsFirstTurnWithInjectedWrapper(t *testing.T)
 	if !strings.Contains(out.PromptTokenText, "first turn content that is long enough") {
 		t.Fatalf("expected prompt token text to preserve original full context, got %q", out.PromptTokenText)
 	}
+	if !strings.Contains(out.PromptTokenText, "# DS2API_HISTORY.txt") || !strings.Contains(out.PromptTokenText, "=== 1. USER ===") {
+		t.Fatalf("expected prompt token text to include numbered history transcript, got %q", out.PromptTokenText)
+	}
 }
 
 func TestApplyCurrentInputFilePreservesFullContextPromptForTokenCounting(t *testing.T) {
@@ -316,7 +332,7 @@ func TestApplyCurrentInputFilePreservesFullContextPromptForTokenCounting(t *test
 		DS: ds,
 	}
 	req := map[string]any{
-		"model":    "deepseek-v4-flash",
+		"model":    "deepseek-v4-vision",
 		"messages": historySplitTestMessages(),
 	}
 	stdReq, err := promptcompat.NormalizeOpenAIChatRequest(h.Store, req, "")
@@ -337,10 +353,13 @@ func TestApplyCurrentInputFilePreservesFullContextPromptForTokenCounting(t *test
 		t.Fatalf("expected prompt token text to contain file context with full conversation, got %q", out.PromptTokenText)
 	}
 	if strings.Contains(out.PromptTokenText, "[file content end]") || strings.Contains(out.PromptTokenText, "[file name]:") {
-		t.Fatalf("expected prompt token text to use raw transcript without wrapper tags, got %q", out.PromptTokenText)
+		t.Fatalf("expected prompt token text to omit file wrapper tags, got %q", out.PromptTokenText)
 	}
-	if !strings.Contains(out.PromptTokenText, "Answer the latest user request directly.") {
-		t.Fatalf("expected prompt token text to also include neutral live prompt, got %q", out.PromptTokenText)
+	if !strings.Contains(out.PromptTokenText, "# DS2API_HISTORY.txt") || !strings.Contains(out.PromptTokenText, "=== 1. SYSTEM ===") {
+		t.Fatalf("expected prompt token text to include numbered history transcript, got %q", out.PromptTokenText)
+	}
+	if !strings.Contains(out.PromptTokenText, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") {
+		t.Fatalf("expected prompt token text to also include continuation prompt, got %q", out.PromptTokenText)
 	}
 	if strings.Contains(out.FinalPrompt, "first user turn") || strings.Contains(out.FinalPrompt, "latest user turn") {
 		t.Fatalf("expected live prompt to hide original turns, got %q", out.FinalPrompt)
@@ -359,7 +378,7 @@ func TestApplyCurrentInputFileUploadsFullContextFile(t *testing.T) {
 		DS: ds,
 	}
 	req := map[string]any{
-		"model":    "deepseek-v4-flash",
+		"model":    "deepseek-v4-vision",
 		"messages": historySplitTestMessages(),
 	}
 	stdReq, err := promptcompat.NormalizeOpenAIChatRequest(h.Store, req, "")
@@ -378,20 +397,23 @@ func TestApplyCurrentInputFileUploadsFullContextFile(t *testing.T) {
 		t.Fatalf("expected one current input upload, got %d", len(ds.uploadCalls))
 	}
 	upload := ds.uploadCalls[0]
-	if upload.Filename != "history.txt" {
-		t.Fatalf("expected history.txt upload, got %q", upload.Filename)
+	if upload.Filename != "DS2API_HISTORY.txt" {
+		t.Fatalf("expected DS2API_HISTORY.txt upload, got %q", upload.Filename)
+	}
+	if upload.ModelType != "vision" {
+		t.Fatalf("expected vision model type for vision request, got %q", upload.ModelType)
 	}
 	uploadedText := string(upload.Data)
-	for _, want := range []string{"system instructions", "first user turn", "hidden reasoning", "tool result", "latest user turn", promptcompat.ThinkingInjectionMarker} {
+	for _, want := range []string{"# DS2API_HISTORY.txt", "=== 1. SYSTEM ===", "=== 2. USER ===", "=== 3. ASSISTANT ===", "=== 4. TOOL ===", "=== 5. USER ===", "system instructions", "first user turn", "hidden reasoning", "tool result", "latest user turn", promptcompat.ThinkingInjectionMarker} {
 		if !strings.Contains(uploadedText, want) {
 			t.Fatalf("expected full context file to contain %q, got %q", want, uploadedText)
 		}
 	}
-	if strings.Contains(out.FinalPrompt, "first user turn") || strings.Contains(out.FinalPrompt, "latest user turn") || strings.Contains(out.FinalPrompt, "CURRENT_USER_INPUT.txt") || strings.Contains(out.FinalPrompt, "history.txt") || strings.Contains(out.FinalPrompt, "Read that file") {
-		t.Fatalf("expected live prompt to use only a neutral continuation instruction, got %s", out.FinalPrompt)
+	if strings.Contains(out.FinalPrompt, "first user turn") || strings.Contains(out.FinalPrompt, "latest user turn") || strings.Contains(out.FinalPrompt, "CURRENT_USER_INPUT.txt") || strings.Contains(out.FinalPrompt, "Read that file") {
+		t.Fatalf("expected live prompt to use only a continuation instruction, got %s", out.FinalPrompt)
 	}
-	if !strings.Contains(out.FinalPrompt, "Answer the latest user request directly.") {
-		t.Fatalf("expected neutral continuation instruction in live prompt, got %s", out.FinalPrompt)
+	if !strings.Contains(out.FinalPrompt, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") {
+		t.Fatalf("expected continuation-oriented prompt in live prompt, got %s", out.FinalPrompt)
 	}
 }
 
@@ -423,6 +445,9 @@ func TestApplyCurrentInputFileCarriesHistoryText(t *testing.T) {
 	if out.HistoryText != string(ds.uploadCalls[0].Data) {
 		t.Fatalf("expected current input file flow to preserve uploaded text in history, got %q", out.HistoryText)
 	}
+	if !strings.Contains(out.HistoryText, "# DS2API_HISTORY.txt") || !strings.Contains(out.HistoryText, "=== 1. SYSTEM ===") {
+		t.Fatalf("expected history text to use numbered transcript format, got %q", out.HistoryText)
+	}
 }
 
 func TestChatCompletionsCurrentInputFileUploadsContextAndKeepsNeutralPrompt(t *testing.T) {
@@ -454,7 +479,7 @@ func TestChatCompletionsCurrentInputFileUploadsContextAndKeepsNeutralPrompt(t *t
 		t.Fatalf("expected 1 upload call, got %d", len(ds.uploadCalls))
 	}
 	upload := ds.uploadCalls[0]
-	if upload.Filename != "history.txt" {
+	if upload.Filename != "DS2API_HISTORY.txt" {
 		t.Fatalf("unexpected upload filename: %q", upload.Filename)
 	}
 	if upload.Purpose != "assistants" {
@@ -462,7 +487,10 @@ func TestChatCompletionsCurrentInputFileUploadsContextAndKeepsNeutralPrompt(t *t
 	}
 	historyText := string(upload.Data)
 	if strings.Contains(historyText, "[file content end]") || strings.Contains(historyText, "[file content begin]") || strings.Contains(historyText, "[file name]:") {
-		t.Fatalf("expected plain history transcript without wrapper tags, got %s", historyText)
+		t.Fatalf("expected history transcript without file wrapper tags, got %s", historyText)
+	}
+	if !strings.Contains(historyText, "# DS2API_HISTORY.txt") || !strings.Contains(historyText, "=== 1. SYSTEM ===") {
+		t.Fatalf("expected history transcript to use numbered sections, got %s", historyText)
 	}
 	if !strings.Contains(historyText, "latest user turn") {
 		t.Fatalf("expected full context to include latest turn, got %s", historyText)
@@ -471,8 +499,8 @@ func TestChatCompletionsCurrentInputFileUploadsContextAndKeepsNeutralPrompt(t *t
 		t.Fatal("expected completion payload to be captured")
 	}
 	promptText, _ := ds.completionReq["prompt"].(string)
-	if !strings.Contains(promptText, "Answer the latest user request directly.") {
-		t.Fatalf("expected neutral completion prompt, got %s", promptText)
+	if !strings.Contains(promptText, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") {
+		t.Fatalf("expected continuation-oriented prompt, got %s", promptText)
 	}
 	if strings.Contains(promptText, "first user turn") || strings.Contains(promptText, "latest user turn") {
 		t.Fatalf("expected prompt to hide original turns, got %s", promptText)
@@ -523,12 +551,16 @@ func TestResponsesCurrentInputFileUploadsContextAndKeepsNeutralPrompt(t *testing
 	if len(ds.uploadCalls) != 1 {
 		t.Fatalf("expected 1 upload call, got %d", len(ds.uploadCalls))
 	}
+	historyText := string(ds.uploadCalls[0].Data)
+	if !strings.Contains(historyText, "# DS2API_HISTORY.txt") || !strings.Contains(historyText, "=== 1. SYSTEM ===") {
+		t.Fatalf("expected uploaded history text to use numbered transcript format, got %s", historyText)
+	}
 	if ds.completionReq == nil {
 		t.Fatal("expected completion payload to be captured")
 	}
 	promptText, _ := ds.completionReq["prompt"].(string)
-	if !strings.Contains(promptText, "Answer the latest user request directly.") {
-		t.Fatalf("expected neutral completion prompt, got %s", promptText)
+	if !strings.Contains(promptText, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") {
+		t.Fatalf("expected continuation-oriented prompt, got %s", promptText)
 	}
 	if strings.Contains(promptText, "first user turn") || strings.Contains(promptText, "latest user turn") {
 		t.Fatalf("expected prompt to hide original turns, got %s", promptText)
@@ -669,11 +701,15 @@ func TestCurrentInputFileWorksAcrossAutoDeleteModes(t *testing.T) {
 			if len(ds.uploadCalls) != 1 {
 				t.Fatalf("expected current input upload for mode=%s, got %d", mode, len(ds.uploadCalls))
 			}
+			historyText := string(ds.uploadCalls[0].Data)
+			if !strings.Contains(historyText, "# DS2API_HISTORY.txt") || !strings.Contains(historyText, "=== 1. SYSTEM ===") {
+				t.Fatalf("expected uploaded history text to use numbered transcript format, got %s", historyText)
+			}
 			if ds.completionReq == nil {
 				t.Fatalf("expected completion payload for mode=%s", mode)
 			}
 			promptText, _ := ds.completionReq["prompt"].(string)
-			if !strings.Contains(promptText, "Answer the latest user request directly.") || strings.Contains(promptText, "first user turn") || strings.Contains(promptText, "latest user turn") {
+			if !strings.Contains(promptText, "Continue from the latest state in the attached DS2API_HISTORY.txt context.") || strings.Contains(promptText, "first user turn") || strings.Contains(promptText, "latest user turn") {
 				t.Fatalf("unexpected prompt for mode=%s: %s", mode, promptText)
 			}
 		})

internal/httpapi/openai/responses/empty_retry_runtime.go

@@ -222,7 +222,13 @@ func (h *Handler) consumeResponsesStreamAttempt(r *http.Request, resp *http.Resp
 				finalReason = "content_filter"
 			}
 		},
+		OnContextDone: func() {
+			streamRuntime.markContextCancelled()
+		},
 	})
+	if streamRuntime.finalErrorCode == string(streamengine.StopReasonContextCancelled) {
+		return true, false
+	}
 	terminalWritten := streamRuntime.finalize(finalReason, allowDeferEmpty && finalReason != "content_filter")
 	if terminalWritten {
 		return true, false
@@ -235,6 +241,10 @@ func logResponsesStreamTerminal(streamRuntime *responsesStreamRuntime, attempts
 	if attempts > 0 {
 		source = "synthetic_retry"
 	}
+	if streamRuntime.finalErrorCode == string(streamengine.StopReasonContextCancelled) {
+		config.Logger.Info("[openai_empty_retry] terminal cancelled", "surface", "responses", "stream", true, "retry_attempts", attempts, "error_code", streamRuntime.finalErrorCode)
+		return
+	}
 	if streamRuntime.failed {
 		config.Logger.Info("[openai_empty_retry] terminal empty output", "surface", "responses", "stream", true, "retry_attempts", attempts, "success_source", "none", "error_code", streamRuntime.finalErrorCode)
 		return

internal/httpapi/openai/responses/empty_retry_runtime_test.go

@@ -0,0 +1,70 @@
+package responses
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"ds2api/internal/promptcompat"
+	"ds2api/internal/stream"
+)
+
+func makeResponsesOpenAISSEHTTPResponse(lines ...string) *http.Response {
+	body := strings.Join(lines, "\n")
+	if !strings.HasSuffix(body, "\n") {
+		body += "\n"
+	}
+	return &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     make(http.Header),
+		Body:       io.NopCloser(strings.NewReader(body)),
+	}
+}
+
+func TestConsumeResponsesStreamAttemptMarksContextCancelledState(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/responses", nil).WithContext(ctx)
+	rec := httptest.NewRecorder()
+	streamRuntime := newResponsesStreamRuntime(
+		rec,
+		http.NewResponseController(rec),
+		true,
+		"resp-cancelled",
+		"deepseek-v4-flash",
+		"prompt",
+		false,
+		false,
+		true,
+		nil,
+		nil,
+		false,
+		false,
+		promptcompat.DefaultToolChoicePolicy(),
+		"",
+		nil,
+	)
+	resp := makeResponsesOpenAISSEHTTPResponse(
+		`data: {"p":"response/content","v":"hello"}`,
+		`data: [DONE]`,
+	)
+
+	h := &Handler{}
+	terminalWritten, retryable := h.consumeResponsesStreamAttempt(req, resp, streamRuntime, "text", false, true)
+	if !terminalWritten || retryable {
+		t.Fatalf("expected cancelled attempt to terminate without retry, got terminalWritten=%v retryable=%v", terminalWritten, retryable)
+	}
+	if !streamRuntime.failed {
+		t.Fatalf("expected cancelled response stream to be marked failed")
+	}
+	if got, want := streamRuntime.finalErrorCode, string(stream.StopReasonContextCancelled); got != want {
+		t.Fatalf("expected cancelled final error code %q, got %q", want, got)
+	}
+	if streamRuntime.finalErrorMessage == "" {
+		t.Fatalf("expected cancelled final error message to be preserved")
+	}
+}

internal/httpapi/openai/responses/responses_stream_runtime_core.go

@@ -139,6 +139,13 @@ func (s *responsesStreamRuntime) failResponse(status int, message, code string)
 	s.sendDone()
 }
 
+func (s *responsesStreamRuntime) markContextCancelled() {
+	s.failed = true
+	s.finalErrorStatus = 499
+	s.finalErrorMessage = "request context cancelled"
+	s.finalErrorCode = string(streamengine.StopReasonContextCancelled)
+}
+
 func (s *responsesStreamRuntime) finalize(finishReason string, deferEmptyOutput bool) bool {
 	s.failed = false
 	s.finalErrorStatus = 0

internal/httpapi/requestbody/json_utf8.go

@@ -0,0 +1,134 @@
+package requestbody
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"mime"
+	"net/http"
+	"strings"
+	"unicode/utf8"
+)
+
+var (
+	ErrInvalidUTF8Body     = errors.New("invalid utf-8 request body")
+	errRequestBodyTooLarge = errors.New("request body too large")
+)
+
+const maxJSONUTF8ValidationSize = 100 << 20
+
+// ValidateJSONUTF8 validates complete JSON request bodies before downstream
+// decoders can silently replace malformed UTF-8 or stop before trailing bytes.
+func ValidateJSONUTF8(next http.Handler) http.Handler {
+	if next == nil {
+		return http.HandlerFunc(func(http.ResponseWriter, *http.Request) {})
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if shouldValidateJSONBody(r) {
+			r.Body = validateAndReplayBody(r.Body)
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+func shouldValidateJSONBody(r *http.Request) bool {
+	if r == nil || r.Body == nil {
+		return false
+	}
+	path := ""
+	if r.URL != nil {
+		path = r.URL.Path
+	}
+	return isJSONContentType(r.Header.Get("Content-Type")) || isKnownJSONRequestPath(r.Method, path)
+}
+
+func isJSONContentType(raw string) bool {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return false
+	}
+	mediaType, _, err := mime.ParseMediaType(raw)
+	if err != nil {
+		mediaType = raw
+	}
+	mediaType = strings.ToLower(strings.TrimSpace(mediaType))
+	return strings.Contains(mediaType, "json")
+}
+
+func isKnownJSONRequestPath(method, path string) bool {
+	switch strings.ToUpper(strings.TrimSpace(method)) {
+	case http.MethodPost, http.MethodPut, http.MethodPatch, http.MethodDelete:
+	default:
+		return false
+	}
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return false
+	}
+	switch {
+	case path == "/v1/chat/completions" || path == "/chat/completions":
+		return true
+	case path == "/v1/responses" || path == "/responses":
+		return true
+	case path == "/v1/embeddings" || path == "/embeddings":
+		return true
+	case path == "/anthropic/v1/messages" || path == "/v1/messages" || path == "/messages":
+		return true
+	case path == "/anthropic/v1/messages/count_tokens" || path == "/v1/messages/count_tokens" || path == "/messages/count_tokens":
+		return true
+	case strings.HasPrefix(path, "/v1beta/models/") || strings.HasPrefix(path, "/v1/models/"):
+		return strings.Contains(path, ":generateContent") || strings.Contains(path, ":streamGenerateContent")
+	case strings.HasPrefix(path, "/admin/"):
+		return true
+	default:
+		return false
+	}
+}
+
+func validateAndReplayBody(body io.ReadCloser) io.ReadCloser {
+	if body == nil {
+		return body
+	}
+	raw, err := io.ReadAll(io.LimitReader(body, maxJSONUTF8ValidationSize+1))
+	if err != nil {
+		return &errorReadCloser{err: err, closer: body}
+	}
+	if len(raw) > maxJSONUTF8ValidationSize {
+		return &errorReadCloser{err: errRequestBodyTooLarge, closer: body}
+	}
+	if !utf8.Valid(raw) {
+		return &errorReadCloser{err: ErrInvalidUTF8Body, closer: body}
+	}
+	return &replayReadCloser{Reader: bytes.NewReader(raw), closer: body}
+}
+
+type replayReadCloser struct {
+	*bytes.Reader
+	closer io.Closer
+}
+
+func (r *replayReadCloser) Close() error {
+	if r == nil || r.closer == nil {
+		return nil
+	}
+	return r.closer.Close()
+}
+
+type errorReadCloser struct {
+	err    error
+	closer io.Closer
+}
+
+func (r *errorReadCloser) Read([]byte) (int, error) {
+	if r == nil || r.err == nil {
+		return 0, io.EOF
+	}
+	return 0, r.err
+}
+
+func (r *errorReadCloser) Close() error {
+	if r == nil || r.closer == nil {
+		return nil
+	}
+	return r.closer.Close()
+}

internal/httpapi/requestbody/json_utf8_test.go

@@ -0,0 +1,158 @@
+package requestbody
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+type singleByteReadCloser struct {
+	data []byte
+	pos  int
+}
+
+func (r *singleByteReadCloser) Read(p []byte) (int, error) {
+	if r.pos >= len(r.data) {
+		return 0, io.EOF
+	}
+	p[0] = r.data[r.pos]
+	r.pos++
+	return 1, nil
+}
+
+func (r *singleByteReadCloser) Close() error {
+	return nil
+}
+
+func TestValidateJSONUTF8AllowsSplitMultibyteRunes(t *testing.T) {
+	body := []byte(`{"text":"你好"}`)
+	handler := ValidateJSONUTF8(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req map[string]any
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			t.Fatalf("unexpected decode error: %v", err)
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}))
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", &singleByteReadCloser{data: body})
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusNoContent {
+		t.Fatalf("expected 204 for valid utf-8 json, got %d body=%q", rec.Code, rec.Body.String())
+	}
+}
+
+func TestValidateJSONUTF8RejectsInvalidBytesBeforeJSONDecode(t *testing.T) {
+	body := append([]byte(`{"text":"`), 0xff)
+	body = append(body, []byte(`"}`)...)
+	handler := ValidateJSONUTF8(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req map[string]any
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			_, _ = w.Write([]byte(err.Error()))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "application/json; charset=utf-8")
+	rec := httptest.NewRecorder()
+
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 for invalid utf-8 json, got %d body=%q", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(strings.ToLower(rec.Body.String()), "invalid utf-8") {
+		t.Fatalf("expected utf-8 validation error, got %q", rec.Body.String())
+	}
+}
+
+func TestValidateJSONUTF8RejectsInvalidBytesWithoutJSONContentTypeOnKnownPath(t *testing.T) {
+	body := append([]byte(`{"text":"`), 0xff)
+	body = append(body, []byte(`"}`)...)
+	handler := ValidateJSONUTF8(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req map[string]any
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			_, _ = w.Write([]byte(err.Error()))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "text/plain")
+	rec := httptest.NewRecorder()
+
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 for invalid utf-8 json, got %d body=%q", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(strings.ToLower(rec.Body.String()), "invalid utf-8") {
+		t.Fatalf("expected utf-8 validation error, got %q", rec.Body.String())
+	}
+}
+
+func TestValidateJSONUTF8RejectsTrailingInvalidBytesAfterJSONValue(t *testing.T) {
+	body := append([]byte(`{"text":"ok"}`), 0xff)
+	handler := ValidateJSONUTF8(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req map[string]any
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			_, _ = w.Write([]byte(err.Error()))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 for trailing invalid utf-8, got %d body=%q", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(strings.ToLower(rec.Body.String()), "invalid utf-8") {
+		t.Fatalf("expected utf-8 validation error, got %q", rec.Body.String())
+	}
+}
+
+func TestIsJSONContentType(t *testing.T) {
+	for _, raw := range []string{
+		"application/json",
+		"application/json; charset=utf-8",
+		"application/problem+json",
+		"application/vnd.api+json",
+	} {
+		if !isJSONContentType(raw) {
+			t.Fatalf("expected %q to be recognized as json", raw)
+		}
+	}
+	for _, raw := range []string{
+		"multipart/form-data; boundary=abc",
+		"text/plain",
+		"application/octet-stream",
+	} {
+		if isJSONContentType(raw) {
+			t.Fatalf("expected %q not to be recognized as json", raw)
+		}
+	}
+}
+
+func TestIsKnownJSONRequestPathIncludesGeminiStream(t *testing.T) {
+	if !isKnownJSONRequestPath(http.MethodPost, "/v1beta/models/gemini-pro:streamGenerateContent") {
+		t.Fatal("expected Gemini stream generate path to be recognized as json")
+	}
+}

internal/js/helpers/stream-tool-sieve/parse_payload.js

@@ -846,10 +846,18 @@ function parseMarkupValue(raw, paramName = '') {
   if (cdata.ok) {
     const literal = parseJSONLiteralValue(cdata.value);
     if (literal.ok) {
+      const literalArray = coerceArrayValue(literal.value, paramName);
+      if (literalArray.ok) {
+        return literalArray.value;
+      }
       return literal.value;
     }
     const structured = parseStructuredCDATAParameterValue(paramName, cdata.value);
-    return structured.ok ? structured.value : cdata.value;
+    if (structured.ok) {
+      return structured.value;
+    }
+    const looseArray = parseLooseJSONArrayValue(cdata.value, paramName);
+    return looseArray.ok ? looseArray.value : cdata.value;
   }
   const s = toStringSafe(extractRawTagValue(raw)).trim();
   if (!s) {
@@ -862,8 +870,14 @@ function parseMarkupValue(raw, paramName = '') {
       return nested;
     }
     if (nested && typeof nested === 'object') {
+      const nestedArray = coerceArrayValue(nested, paramName);
+      if (nestedArray.ok) {
+        return nestedArray.value;
+      }
       if (isOnlyRawValue(nested)) {
-        return toStringSafe(nested._raw);
+        const rawValue = toStringSafe(nested._raw);
+        const looseArray = parseLooseJSONArrayValue(rawValue, paramName);
+        return looseArray.ok ? looseArray.value : rawValue;
       }
       return nested;
     }
@@ -871,8 +885,16 @@ function parseMarkupValue(raw, paramName = '') {
 
   const literal = parseJSONLiteralValue(s);
   if (literal.ok) {
+    const literalArray = coerceArrayValue(literal.value, paramName);
+    if (literalArray.ok) {
+      return literalArray.value;
+    }
     return literal.value;
   }
+  const looseArray = parseLooseJSONArrayValue(s, paramName);
+  if (looseArray.ok) {
+    return looseArray.value;
+  }
   return s;
 }
 
@@ -1008,6 +1030,226 @@ function parseJSONLiteralValue(raw) {
   }
 }
 
+function parseLooseJSONArrayValue(raw, paramName = '') {
+  if (preservesCDATAStringParameter(paramName)) {
+    return { ok: false, value: null };
+  }
+  const s = toStringSafe(raw).trim();
+  if (!s) {
+    return { ok: false, value: null };
+  }
+  const candidate = parseLooseJSONArrayCandidate(s, paramName);
+  if (candidate.ok) {
+    return candidate;
+  }
+
+  const segments = splitTopLevelJSONValues(s);
+  if (segments.length < 2) {
+    return { ok: false, value: null };
+  }
+
+  const out = [];
+  for (const segment of segments) {
+    const parsed = parseLooseArrayElementValue(segment);
+    if (!parsed.ok) {
+      return { ok: false, value: null };
+    }
+    out.push(parsed.value);
+  }
+  return { ok: true, value: out };
+}
+
+function parseLooseJSONArrayCandidate(raw, paramName = '') {
+  const parsed = parseLooseArrayElementValue(raw);
+  if (!parsed.ok) {
+    return { ok: false, value: null };
+  }
+  return coerceArrayValue(parsed.value, paramName);
+}
+
+function parseLooseArrayElementValue(raw) {
+  const s = toStringSafe(raw).trim();
+  if (!s) {
+    return { ok: false, value: null };
+  }
+
+  const literal = parseJSONLiteralValue(s);
+  if (literal.ok) {
+    return literal;
+  }
+
+  const repairedBackslashes = repairInvalidJSONBackslashes(s);
+  if (repairedBackslashes !== s) {
+    try {
+      const parsed = JSON.parse(repairedBackslashes);
+      return { ok: true, value: parsed };
+    } catch (_err) {
+      // Fall through.
+    }
+  }
+
+  const repairedLoose = repairLooseJSON(s);
+  if (repairedLoose !== s) {
+    try {
+      const parsed = JSON.parse(repairedLoose);
+      return { ok: true, value: parsed };
+    } catch (_err) {
+      // Fall through.
+    }
+  }
+
+  if (s.includes('<') && s.includes('>')) {
+    const parsed = parseMarkupInput(s);
+    if (Array.isArray(parsed)) {
+      return { ok: true, value: parsed };
+    }
+    if (parsed && typeof parsed === 'object') {
+      return { ok: true, value: parsed };
+    }
+  }
+
+  return { ok: false, value: null };
+}
+
+function coerceArrayValue(value, paramName = '') {
+  if (Array.isArray(value)) {
+    return { ok: true, value };
+  }
+  if (!value || typeof value !== 'object') {
+    return { ok: false, value: null };
+  }
+
+  const keys = Object.keys(value);
+  if (keys.length !== 1) {
+    return { ok: false, value: null };
+  }
+
+  if (Object.prototype.hasOwnProperty.call(value, 'item')) {
+    const items = value.item;
+    const nested = coerceArrayValue(items, '');
+    return nested.ok ? nested : { ok: true, value: [items] };
+  }
+
+  if (paramName && Object.prototype.hasOwnProperty.call(value, paramName)) {
+    const nested = coerceArrayValue(value[paramName], '');
+    if (nested.ok) {
+      return nested;
+    }
+  }
+
+  return { ok: false, value: null };
+}
+
+function splitTopLevelJSONValues(raw) {
+  const s = toStringSafe(raw).trim();
+  if (!s) {
+    return [];
+  }
+
+  const values = [];
+  let start = 0;
+  let depth = 0;
+  let inString = false;
+  let escaped = false;
+
+  for (let i = 0; i < s.length; i += 1) {
+    const ch = s[i];
+    if (inString) {
+      if (escaped) {
+        escaped = false;
+        continue;
+      }
+      if (ch === '\\') {
+        escaped = true;
+        continue;
+      }
+      if (ch === '"') {
+        inString = false;
+      }
+      continue;
+    }
+    if (ch === '"') {
+      inString = true;
+      continue;
+    }
+    if (ch === '{' || ch === '[') {
+      depth += 1;
+      continue;
+    }
+    if (ch === '}' || ch === ']') {
+      if (depth > 0) {
+        depth -= 1;
+      }
+      continue;
+    }
+    if (ch === ',' && depth === 0) {
+      const segment = s.slice(start, i).trim();
+      if (!segment) {
+        return [];
+      }
+      values.push(segment);
+      start = i + 1;
+    }
+  }
+
+  const last = s.slice(start).trim();
+  if (!last) {
+    return [];
+  }
+  values.push(last);
+  return values.length > 1 ? values : [];
+}
+
+function repairInvalidJSONBackslashes(s) {
+  if (!s || !s.includes('\\')) {
+    return s;
+  }
+
+  let out = '';
+  for (let i = 0; i < s.length; i += 1) {
+    const ch = s[i];
+    if (ch !== '\\') {
+      out += ch;
+      continue;
+    }
+    if (i + 1 < s.length) {
+      const next = s[i + 1];
+      if ('"\\/bfnrt'.includes(next)) {
+        out += `\\${next}`;
+        i += 1;
+        continue;
+      }
+      if (next === 'u' && i + 5 < s.length) {
+        let isHex = true;
+        for (let j = 1; j <= 4; j += 1) {
+          const r = s[i + 1 + j];
+          if (!/[0-9a-fA-F]/.test(r)) {
+            isHex = false;
+            break;
+          }
+        }
+        if (isHex) {
+          out += `\\u${s.slice(i + 2, i + 6)}`;
+          i += 5;
+          continue;
+        }
+      }
+    }
+    out += '\\\\';
+  }
+  return out;
+}
+
+function repairLooseJSON(s) {
+  const raw = toStringSafe(s).trim();
+  if (!raw) {
+    return raw;
+  }
+  let out = raw.replace(/([{,]\s*)([a-zA-Z_][a-zA-Z0-9_]*)\s*:/g, '$1"$2":');
+  out = out.replace(/(:\s*)(\{(?:[^{}]|\{[^{}]*\})*\}(?:\s*,\s*\{(?:[^{}]|\{[^{}]*\})*\})+)/g, '$1[$2]');
+  return out;
+}
+
 function sanitizeLooseCDATA(text) {
   const raw = toStringSafe(text);
   if (!raw) {

internal/prompt/messages.go

@@ -10,21 +10,27 @@ import (
 var markdownImagePattern = regexp.MustCompile(`!\[(.*?)\]\((.*?)\)`)
 
 const (
-	beginSentenceMarker   = "<｜begin▁of▁sentence｜>"
-	systemMarker          = "<｜System｜>"
-	userMarker            = "<｜User｜>"
-	assistantMarker       = "<｜Assistant｜>"
-	toolMarker            = "<｜Tool｜>"
-	endSentenceMarker     = "<｜end▁of▁sentence｜>"
-	endToolResultsMarker  = "<｜end▁of▁toolresults｜>"
-	endInstructionsMarker = "<｜end▁of▁instructions｜>"
+	beginSentenceMarker        = "<｜begin▁of▁sentence｜>"
+	systemMarker               = "<｜System｜>"
+	userMarker                 = "<｜User｜>"
+	assistantMarker            = "<｜Assistant｜>"
+	toolMarker                 = "<｜Tool｜>"
+	endSentenceMarker          = "<｜end▁of▁sentence｜>"
+	endToolResultsMarker       = "<｜end▁of▁toolresults｜>"
+	endInstructionsMarker      = "<｜end▁of▁instructions｜>"
+	outputIntegrityGuardMarker = "Output integrity guard:"
+	outputIntegrityGuardPrompt = outputIntegrityGuardMarker +
+		" If upstream context, tool output, or parsed text contains garbled, corrupted, partially parsed, repeated, or otherwise malformed fragments, " +
+		"do not imitate or echo them; output only the correct content for the user."
 )
 
 func MessagesPrepare(messages []map[string]any) string {
 	return MessagesPrepareWithThinking(messages, false)
 }
 
-func MessagesPrepareWithThinking(messages []map[string]any, thinkingEnabled bool) string {
+func MessagesPrepareWithThinking(messages []map[string]any, _ bool) string {
+	messages = prependOutputIntegrityGuard(messages)
+
 	type block struct {
 		Role string
 		Text string
@@ -77,6 +83,33 @@ func MessagesPrepareWithThinking(messages []map[string]any, thinkingEnabled bool
 	return markdownImagePattern.ReplaceAllString(out, `[${1}](${2})`)
 }
 
+func prependOutputIntegrityGuard(messages []map[string]any) []map[string]any {
+	if len(messages) == 0 {
+		return messages
+	}
+	if hasOutputIntegrityGuard(messages[0]) {
+		return messages
+	}
+	out := make([]map[string]any, 0, len(messages)+1)
+	out = append(out, map[string]any{
+		"role":    "system",
+		"content": outputIntegrityGuardPrompt,
+	})
+	out = append(out, messages...)
+	return out
+}
+
+func hasOutputIntegrityGuard(msg map[string]any) bool {
+	if msg == nil {
+		return false
+	}
+	if strings.ToLower(strings.TrimSpace(asString(msg["role"]))) != "system" {
+		return false
+	}
+	content := strings.TrimSpace(NormalizeContent(msg["content"]))
+	return strings.Contains(content, outputIntegrityGuardMarker)
+}
+
 // formatRoleBlock produces a single concatenated block: marker + text + endMarker.
 // No whitespace is inserted between marker and text so role boundaries stay
 // compact and predictable for downstream parsers.

internal/prompt/messages_test.go

@@ -35,8 +35,8 @@ func TestMessagesPrepareUsesTurnSuffixes(t *testing.T) {
 	if !strings.HasPrefix(got, "<｜begin▁of▁sentence｜>") {
 		t.Fatalf("expected begin-of-sentence marker, got %q", got)
 	}
-	if !strings.Contains(got, "<｜System｜>System rule<｜end▁of▁instructions｜>") {
-		t.Fatalf("expected system instructions suffix, got %q", got)
+	if !strings.Contains(got, "<｜System｜>") || !strings.Contains(got, "<｜end▁of▁instructions｜>") || !strings.Contains(got, "System rule") {
+		t.Fatalf("expected system instructions to remain present, got %q", got)
 	}
 	if !strings.Contains(got, "<｜User｜>Question") {
 		t.Fatalf("expected user question, got %q", got)
@@ -49,6 +49,23 @@ func TestMessagesPrepareUsesTurnSuffixes(t *testing.T) {
 	}
 }
 
+func TestMessagesPreparePrependsOutputIntegrityGuard(t *testing.T) {
+	messages := []map[string]any{
+		{"role": "system", "content": "System rule"},
+		{"role": "user", "content": "Question"},
+	}
+	got := MessagesPrepare(messages)
+	if !strings.HasPrefix(got, beginSentenceMarker+systemMarker+outputIntegrityGuardPrompt) {
+		t.Fatalf("expected output integrity guard to be prepended, got %q", got)
+	}
+	if !strings.Contains(got, outputIntegrityGuardPrompt+"\n\nSystem rule") {
+		t.Fatalf("expected output integrity guard to precede system prompt content, got %q", got)
+	}
+	if !strings.Contains(got, "<｜User｜>Question") {
+		t.Fatalf("expected user question after guard, got %q", got)
+	}
+}
+
 func TestNormalizeContentArrayFallsBackToContentWhenTextEmpty(t *testing.T) {
 	got := NormalizeContent([]any{
 		map[string]any{"type": "text", "text": "", "content": "from-content"},

internal/promptcompat/history_transcript.go

@@ -1,35 +1,108 @@
 package promptcompat
 
 import (
+	"fmt"
 	"strings"
-
-	"ds2api/internal/prompt"
 )
 
-const CurrentInputContextFilename = "history.txt"
+const CurrentInputContextFilename = "DS2API_HISTORY.txt"
+
+const historyTranscriptTitle = "# DS2API_HISTORY.txt"
+const historyTranscriptSummary = "Prior conversation history and tool progress."
 
 func BuildOpenAIHistoryTranscript(messages []any) string {
-	return buildOpenAIInjectedFileTranscript(messages)
+	return buildOpenAIHistoryTranscript(messages)
 }
 
 func BuildOpenAICurrentUserInputTranscript(text string) string {
 	if strings.TrimSpace(text) == "" {
 		return ""
 	}
-	return BuildOpenAICurrentInputContextTranscript([]any{
+	return buildOpenAIHistoryTranscript([]any{
 		map[string]any{"role": "user", "content": text},
 	})
 }
 
 func BuildOpenAICurrentInputContextTranscript(messages []any) string {
-	return buildOpenAIInjectedFileTranscript(messages)
+	return buildOpenAIHistoryTranscript(messages)
 }
 
-func buildOpenAIInjectedFileTranscript(messages []any) string {
-	normalized := NormalizeOpenAIMessagesForPrompt(messages, "")
-	transcript := strings.TrimSpace(prompt.MessagesPrepare(normalized))
+func buildOpenAIHistoryTranscript(messages []any) string {
+	if len(messages) == 0 {
+		return ""
+	}
+	var b strings.Builder
+	b.WriteString(historyTranscriptTitle)
+	b.WriteString("\n")
+	b.WriteString(historyTranscriptSummary)
+	b.WriteString("\n\n")
+
+	entry := 0
+	for _, raw := range messages {
+		msg, ok := raw.(map[string]any)
+		if !ok {
+			continue
+		}
+		role := normalizeOpenAIRoleForPrompt(strings.ToLower(strings.TrimSpace(asString(msg["role"]))))
+		content := strings.TrimSpace(buildOpenAIHistoryEntry(role, msg))
+		if content == "" {
+			continue
+		}
+		entry++
+		fmt.Fprintf(&b, "=== %d. %s ===\n%s\n\n", entry, strings.ToUpper(roleLabelForHistory(role)), content)
+	}
+
+	transcript := strings.TrimSpace(b.String())
 	if transcript == "" {
 		return ""
 	}
-	return transcript
+	return transcript + "\n"
+}
+
+func buildOpenAIHistoryEntry(role string, msg map[string]any) string {
+	switch role {
+	case "assistant":
+		return strings.TrimSpace(buildAssistantContentForPrompt(msg))
+	case "tool", "function":
+		return strings.TrimSpace(buildToolHistoryContent(msg))
+	case "system", "user":
+		return strings.TrimSpace(NormalizeOpenAIContentForPrompt(msg["content"]))
+	default:
+		return strings.TrimSpace(NormalizeOpenAIContentForPrompt(msg["content"]))
+	}
+}
+
+func buildToolHistoryContent(msg map[string]any) string {
+	content := strings.TrimSpace(NormalizeOpenAIContentForPrompt(msg["content"]))
+	parts := make([]string, 0, 2)
+	if name := strings.TrimSpace(asString(msg["name"])); name != "" {
+		parts = append(parts, "name="+name)
+	}
+	if callID := strings.TrimSpace(asString(msg["tool_call_id"])); callID != "" {
+		parts = append(parts, "tool_call_id="+callID)
+	}
+	header := ""
+	if len(parts) > 0 {
+		header = "[" + strings.Join(parts, " ") + "]"
+	}
+	switch {
+	case header != "" && content != "":
+		return header + "\n" + content
+	case header != "":
+		return header
+	default:
+		return content
+	}
+}
+
+func roleLabelForHistory(role string) string {
+	role = strings.ToLower(strings.TrimSpace(role))
+	switch role {
+	case "function":
+		return "tool"
+	case "":
+		return "unknown"
+	default:
+		return role
+	}
 }

internal/promptcompat/prompt_build_test.go

@@ -88,6 +88,38 @@ func TestBuildOpenAIFinalPrompt_VercelPreparePathKeepsFinalAnswerInstruction(t *
 	}
 }
 
+func TestBuildOpenAIFinalPromptPrependsOutputIntegrityGuard(t *testing.T) {
+	messages := []any{
+		map[string]any{"role": "system", "content": "You are helpful"},
+		map[string]any{"role": "user", "content": "请调用工具"},
+	}
+	tools := []any{
+		map[string]any{
+			"type": "function",
+			"function": map[string]any{
+				"name":        "search",
+				"description": "search docs",
+				"parameters": map[string]any{
+					"type": "object",
+				},
+			},
+		},
+	}
+
+	finalPrompt, _ := buildOpenAIFinalPrompt(messages, tools, "", false)
+	guardIdx := strings.Index(finalPrompt, "Output integrity guard")
+	toolIdx := strings.Index(finalPrompt, "TOOL CALL FORMAT")
+	if guardIdx < 0 {
+		t.Fatalf("expected output integrity guard in final prompt, got: %q", finalPrompt)
+	}
+	if toolIdx < 0 {
+		t.Fatalf("expected tool instructions in final prompt, got: %q", finalPrompt)
+	}
+	if guardIdx > toolIdx {
+		t.Fatalf("expected output integrity guard to precede tool instructions, got: %q", finalPrompt)
+	}
+}
+
 func TestBuildOpenAIFinalPromptReadLikeToolIncludesCacheGuard(t *testing.T) {
 	messages := []any{
 		map[string]any{"role": "user", "content": "请读取文件"},

internal/server/router.go

@@ -27,6 +27,7 @@ import (
 	"ds2api/internal/httpapi/openai/files"
 	"ds2api/internal/httpapi/openai/responses"
 	"ds2api/internal/httpapi/openai/shared"
+	"ds2api/internal/httpapi/requestbody"
 	"ds2api/internal/webui"
 )
 
@@ -75,6 +76,7 @@ func NewApp() (*App, error) {
 	r.Use(filteredLogger())
 	r.Use(middleware.Recoverer)
 	r.Use(cors)
+	r.Use(requestbody.ValidateJSONUTF8)
 	r.Use(timeout(0))
 
 	healthzHandler := func(w http.ResponseWriter, _ *http.Request) {

internal/server/router_utf8_test.go

@@ -0,0 +1,89 @@
+package server
+
+import (
+	"bytes"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestJSONRequestsRejectInvalidUTF8BeforeDecode(t *testing.T) {
+	t.Setenv("DS2API_CONFIG_JSON", `{"keys":["managed-key"],"accounts":[{"email":"u@example.com","password":"p"}]}`)
+	t.Setenv("DS2API_ENV_WRITEBACK", "0")
+
+	app, err := NewApp()
+	if err != nil {
+		t.Fatalf("NewApp() error: %v", err)
+	}
+
+	body := append([]byte(`{"model":"deepseek-v4-flash","messages":[{"role":"user","content":"`), 0xff)
+	body = append(body, []byte(`"}]}`)...)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "application/json; charset=utf-8")
+	req.Header.Set("x-api-key", "direct-token")
+
+	rec := httptest.NewRecorder()
+	app.Router.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 for invalid utf-8 request body, got %d body=%q", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(strings.ToLower(rec.Body.String()), "invalid json") {
+		t.Fatalf("expected invalid json error, got %q", rec.Body.String())
+	}
+}
+
+func TestKnownJSONRequestsRejectInvalidUTF8WithoutJSONContentType(t *testing.T) {
+	t.Setenv("DS2API_CONFIG_JSON", `{"keys":["managed-key"],"accounts":[{"email":"u@example.com","password":"p"}]}`)
+	t.Setenv("DS2API_ENV_WRITEBACK", "0")
+
+	app, err := NewApp()
+	if err != nil {
+		t.Fatalf("NewApp() error: %v", err)
+	}
+
+	body := append([]byte(`{"model":"deepseek-v4-flash","messages":[{"role":"user","content":"`), 0xff)
+	body = append(body, []byte(`"}]}`)...)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "text/plain")
+	req.Header.Set("x-api-key", "direct-token")
+
+	rec := httptest.NewRecorder()
+	app.Router.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 for invalid utf-8 request body, got %d body=%q", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(strings.ToLower(rec.Body.String()), "invalid json") {
+		t.Fatalf("expected invalid json error, got %q", rec.Body.String())
+	}
+}
+
+func TestJSONRequestsRejectTrailingInvalidUTF8AfterCompleteJSON(t *testing.T) {
+	t.Setenv("DS2API_CONFIG_JSON", `{"keys":["managed-key"],"accounts":[{"email":"u@example.com","password":"p"}]}`)
+	t.Setenv("DS2API_ENV_WRITEBACK", "0")
+
+	app, err := NewApp()
+	if err != nil {
+		t.Fatalf("NewApp() error: %v", err)
+	}
+
+	body := append([]byte(`{"model":"deepseek-v4-flash","messages":[{"role":"user","content":"ok"}]}`), 0xff)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("x-api-key", "direct-token")
+
+	rec := httptest.NewRecorder()
+	app.Router.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400 for trailing invalid utf-8, got %d body=%q", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(strings.ToLower(rec.Body.String()), "invalid json") {
+		t.Fatalf("expected invalid json error, got %q", rec.Body.String())
+	}
+}

internal/toolcall/toolcalls_array_parse.go

@@ -0,0 +1,164 @@
+package toolcall
+
+import (
+	"encoding/json"
+	"html"
+	"strings"
+)
+
+func parseLooseJSONArrayValue(raw, paramName string) ([]any, bool) {
+	if preservesCDATAStringParameter(paramName) {
+		return nil, false
+	}
+	trimmed := strings.TrimSpace(html.UnescapeString(raw))
+	if trimmed == "" {
+		return nil, false
+	}
+
+	if parsed, ok := parseLooseJSONArrayCandidate(trimmed, paramName); ok {
+		return parsed, true
+	}
+
+	segments, ok := splitTopLevelJSONValues(trimmed)
+	if !ok {
+		return nil, false
+	}
+
+	out := make([]any, 0, len(segments))
+	for _, segment := range segments {
+		parsed, ok := parseLooseArrayElementValue(segment)
+		if !ok {
+			return nil, false
+		}
+		out = append(out, parsed)
+	}
+	return out, true
+}
+
+func parseLooseJSONArrayCandidate(raw, paramName string) ([]any, bool) {
+	parsed, ok := parseLooseArrayElementValue(raw)
+	if !ok {
+		return nil, false
+	}
+	return coerceArrayValue(parsed, paramName)
+}
+
+func parseLooseArrayElementValue(raw string) (any, bool) {
+	trimmed := strings.TrimSpace(html.UnescapeString(raw))
+	if trimmed == "" {
+		return nil, false
+	}
+
+	var parsed any
+	if err := json.Unmarshal([]byte(trimmed), &parsed); err == nil {
+		return parsed, true
+	}
+
+	repairedBackslashes := repairInvalidJSONBackslashes(trimmed)
+	if repairedBackslashes != trimmed {
+		if err := json.Unmarshal([]byte(repairedBackslashes), &parsed); err == nil {
+			return parsed, true
+		}
+	}
+
+	repairedLoose := RepairLooseJSON(trimmed)
+	if repairedLoose != trimmed {
+		if err := json.Unmarshal([]byte(repairedLoose), &parsed); err == nil {
+			return parsed, true
+		}
+	}
+
+	if strings.Contains(trimmed, "<") && strings.Contains(trimmed, ">") {
+		if parsedXML, ok := parseXMLFragmentValue(trimmed); ok {
+			return parsedXML, true
+		}
+	}
+
+	return nil, false
+}
+
+func coerceArrayValue(value any, paramName string) ([]any, bool) {
+	switch x := value.(type) {
+	case []any:
+		return x, true
+	case map[string]any:
+		if len(x) != 1 {
+			return nil, false
+		}
+
+		if items, ok := x["item"]; ok {
+			if arr, ok := coerceArrayValue(items, ""); ok {
+				return arr, true
+			}
+			return []any{items}, true
+		}
+
+		if paramName != "" {
+			if wrapped, ok := x[paramName]; ok {
+				if arr, ok := coerceArrayValue(wrapped, ""); ok {
+					return arr, true
+				}
+			}
+		}
+	}
+	return nil, false
+}
+
+func splitTopLevelJSONValues(raw string) ([]string, bool) {
+	trimmed := strings.TrimSpace(raw)
+	if trimmed == "" {
+		return nil, false
+	}
+
+	values := make([]string, 0, 2)
+	start := 0
+	depth := 0
+	inString := false
+	escaped := false
+
+	for i, r := range trimmed {
+		if inString {
+			if escaped {
+				escaped = false
+				continue
+			}
+			switch r {
+			case '\\':
+				escaped = true
+			case '"':
+				inString = false
+			}
+			continue
+		}
+
+		switch r {
+		case '"':
+			inString = true
+		case '{', '[':
+			depth++
+		case '}', ']':
+			if depth > 0 {
+				depth--
+			}
+		case ',':
+			if depth == 0 {
+				segment := strings.TrimSpace(trimmed[start:i])
+				if segment == "" {
+					return nil, false
+				}
+				values = append(values, segment)
+				start = i + 1
+			}
+		}
+	}
+
+	last := strings.TrimSpace(trimmed[start:])
+	if last == "" {
+		return nil, false
+	}
+	values = append(values, last)
+	if len(values) < 2 {
+		return nil, false
+	}
+	return values, true
+}

internal/toolcall/toolcalls_parse_markup.go

@@ -298,11 +298,17 @@ func parseInvokeParameterValue(paramName, raw string) any {
 	}
 	if value, ok := extractStandaloneCDATA(trimmed); ok {
 		if parsed, ok := parseJSONLiteralValue(value); ok {
+			if parsedArray, ok := coerceArrayValue(parsed, paramName); ok {
+				return parsedArray
+			}
 			return parsed
 		}
 		if parsed, ok := parseStructuredCDATAParameterValue(paramName, value); ok {
 			return parsed
 		}
+		if parsed, ok := parseLooseJSONArrayValue(value, paramName); ok {
+			return parsed
+		}
 		return value
 	}
 	decoded := html.UnescapeString(extractRawTagValue(trimmed))
@@ -311,6 +317,9 @@ func parseInvokeParameterValue(paramName, raw string) any {
 			switch v := parsedValue.(type) {
 			case map[string]any:
 				if len(v) > 0 {
+					if parsedArray, ok := coerceArrayValue(v, paramName); ok {
+						return parsedArray
+					}
 					return v
 				}
 			case []any:
@@ -321,6 +330,12 @@ func parseInvokeParameterValue(paramName, raw string) any {
 					return ""
 				}
 				if parsedText, ok := parseJSONLiteralValue(text); ok {
+					if parsedArray, ok := coerceArrayValue(parsedText, paramName); ok {
+						return parsedArray
+					}
+					return parsedText
+				}
+				if parsedText, ok := parseLooseJSONArrayValue(text, paramName); ok {
 					return parsedText
 				}
 				return v
@@ -331,13 +346,25 @@ func parseInvokeParameterValue(paramName, raw string) any {
 		if parsed := parseStructuredToolCallInput(decoded); len(parsed) > 0 {
 			if len(parsed) == 1 {
 				if rawValue, ok := parsed["_raw"].(string); ok {
+					if parsedText, ok := parseLooseJSONArrayValue(rawValue, paramName); ok {
+						return parsedText
+					}
 					return rawValue
 				}
 			}
+			if parsedArray, ok := coerceArrayValue(parsed, paramName); ok {
+				return parsedArray
+			}
 			return parsed
 		}
 	}
 	if parsed, ok := parseJSONLiteralValue(decoded); ok {
+		if parsedArray, ok := coerceArrayValue(parsed, paramName); ok {
+			return parsedArray
+		}
+		return parsed
+	}
+	if parsed, ok := parseLooseJSONArrayValue(decoded, paramName); ok {
 		return parsed
 	}
 	return decoded

internal/toolcall/toolcalls_test.go

@@ -294,6 +294,59 @@ func TestParseToolCallsTreatsSingleItemCDATAAsArray(t *testing.T) {
 	}
 }
 
+func TestParseToolCallsTreatsLooseJSONListAsArray(t *testing.T) {
+	tests := []struct {
+		name string
+		body string
+	}{
+		{
+			name: "plain text",
+			body: `{"content":"Test TodoWrite tool","status":"completed"}, {"content":"Another task","status":"pending"}`,
+		},
+		{
+			name: "cdata",
+			body: `<![CDATA[{"content":"Test TodoWrite tool","status":"completed"}, {"content":"Another task","status":"pending"}]]>`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			text := `<tool_calls><invoke name="TodoWrite"><parameter name="todos">` + tt.body + `</parameter></invoke></tool_calls>`
+			calls := ParseToolCalls(text, []string{"TodoWrite"})
+			if len(calls) != 1 {
+				t.Fatalf("expected one TodoWrite call, got %#v", calls)
+			}
+			items, ok := calls[0].Input["todos"].([]any)
+			if !ok || len(items) != 2 {
+				t.Fatalf("expected loose JSON list to parse as array, got %#v", calls[0].Input["todos"])
+			}
+			first, ok := items[0].(map[string]any)
+			if !ok {
+				t.Fatalf("expected first todo object, got %#v", items[0])
+			}
+			if first["content"] != "Test TodoWrite tool" || first["status"] != "completed" {
+				t.Fatalf("unexpected first todo: %#v", first)
+			}
+		})
+	}
+}
+
+func TestParseToolCallsKeepsPreservedTextParametersAsText(t *testing.T) {
+	text := `<tool_calls><invoke name="Write"><parameter name="content"><![CDATA[{"content":"Test TodoWrite tool","status":"completed"}, {"content":"Another task","status":"pending"}]]></parameter></invoke></tool_calls>`
+	calls := ParseToolCalls(text, []string{"Write"})
+	if len(calls) != 1 {
+		t.Fatalf("expected one Write call, got %#v", calls)
+	}
+	got, ok := calls[0].Input["content"].(string)
+	if !ok {
+		t.Fatalf("expected content to stay a string, got %#v", calls[0].Input["content"])
+	}
+	want := `{"content":"Test TodoWrite tool","status":"completed"}, {"content":"Another task","status":"pending"}`
+	if got != want {
+		t.Fatalf("expected content to stay raw, got %q", got)
+	}
+}
+
 func TestParseToolCallsTreatsCDATAObjectFragmentAsObject(t *testing.T) {
 	payload := `<question><![CDATA[Pick one]]></question><options><item><label><![CDATA[A]]></label></item><item><label><![CDATA[B]]></label></item></options>`
 	text := `<tool_calls><invoke name="AskUserQuestion"><parameter name="questions"><![CDATA[` + payload + `]]></parameter></invoke></tool_calls>`

internal/util/messages_test.go

@@ -1,6 +1,7 @@
 package util
 
 import (
+	"strings"
 	"testing"
 
 	"ds2api/internal/config"
@@ -12,7 +13,10 @@ func TestMessagesPrepareBasic(t *testing.T) {
 	if got == "" {
 		t.Fatal("expected non-empty prompt")
 	}
-	if got != "<｜begin▁of▁sentence｜><｜User｜>Hello<｜Assistant｜>" {
+	if !strings.HasPrefix(got, "<｜begin▁of▁sentence｜><｜System｜>") {
+		t.Fatalf("expected output integrity guard at the start, got %q", got)
+	}
+	if !strings.Contains(got, "Hello") || !strings.HasSuffix(got, "<｜Assistant｜>") {
 		t.Fatalf("unexpected prompt: %q", got)
 	}
 }
@@ -26,8 +30,11 @@ func TestMessagesPrepareRoles(t *testing.T) {
 		{"role": "user", "content": "How are you"},
 	}
 	got := MessagesPrepare(messages)
-	if !contains(got, "<｜System｜>You are helper<｜end▁of▁instructions｜><｜User｜>Hi") {
-		t.Fatalf("expected system/user separation in %q", got)
+	if !contains(got, "Output integrity guard") {
+		t.Fatalf("expected output integrity guard in %q", got)
+	}
+	if !contains(got, "You are helper") || !contains(got, "<｜User｜>Hi") {
+		t.Fatalf("expected system/user content in %q", got)
 	}
 	if !contains(got, "<｜begin▁of▁sentence｜>") {
 		t.Fatalf("expected begin marker in %q", got)
@@ -77,9 +84,12 @@ func TestMessagesPrepareArrayTextVariants(t *testing.T) {
 		},
 	}
 	got := MessagesPrepare(messages)
-	if got != "<｜begin▁of▁sentence｜><｜User｜>line1\nline2<｜Assistant｜>" {
+	if !contains(got, "line1\nline2") {
 		t.Fatalf("unexpected content from text variants: %q", got)
 	}
+	if !strings.Contains(got, "Output integrity guard") {
+		t.Fatalf("expected output integrity guard in %q", got)
+	}
 }
 
 func TestConvertClaudeToDeepSeek(t *testing.T) {

internal/util/token_count_tiktoken.go

@@ -4,19 +4,26 @@ package util
 
 import (
 	"strings"
+	"sync"
 
 	tiktoken "github.com/hupe1980/go-tiktoken"
 )
 
+var (
+	tokenEncodingPools       sync.Map
+	tokenEncodingUnsupported sync.Map
+)
+
 func countWithTokenizer(text, model string) int {
 	text = strings.TrimSpace(text)
 	if text == "" {
 		return 0
 	}
-	encoding, err := tiktoken.NewEncodingForModel(tokenizerModelForCount(model))
-	if err != nil {
+	encoding, release := tokenizerEncodingForCount(tokenizerModelForCount(model))
+	if encoding == nil {
 		return 0
 	}
+	defer release()
 	ids, _, err := encoding.Encode(text, nil, nil)
 	if err != nil {
 		return 0
@@ -24,6 +31,53 @@ func countWithTokenizer(text, model string) int {
 	return len(ids)
 }
 
+func tokenizerEncodingForCount(model string) (*tiktoken.Encoding, func()) {
+	model = strings.TrimSpace(model)
+	if model == "" {
+		model = defaultTokenizerModel
+	}
+	if _, ok := tokenEncodingUnsupported.Load(model); ok {
+		return nil, func() {}
+	}
+	if rawPool, ok := tokenEncodingPools.Load(model); ok {
+		pool, _ := rawPool.(*sync.Pool)
+		return getEncodingFromPool(pool)
+	}
+
+	encoding, err := tiktoken.NewEncodingForModel(model)
+	if err != nil {
+		tokenEncodingUnsupported.Store(model, struct{}{})
+		return nil, func() {}
+	}
+	pool := &sync.Pool{
+		New: func() any {
+			encoding, err := tiktoken.NewEncodingForModel(model)
+			if err != nil {
+				return nil
+			}
+			return encoding
+		},
+	}
+	actualPool, _ := tokenEncodingPools.LoadOrStore(model, pool)
+	pool, _ = actualPool.(*sync.Pool)
+	return encoding, func() {
+		pool.Put(encoding)
+	}
+}
+
+func getEncodingFromPool(pool *sync.Pool) (*tiktoken.Encoding, func()) {
+	if pool == nil {
+		return nil, func() {}
+	}
+	encoding, _ := pool.Get().(*tiktoken.Encoding)
+	if encoding == nil {
+		return nil, func() {}
+	}
+	return encoding, func() {
+		pool.Put(encoding)
+	}
+}
+
 func tokenizerModelForCount(model string) string {
 	model = strings.ToLower(strings.TrimSpace(model))
 	if model == "" {

internal/util/token_count_tiktoken_test.go

@@ -0,0 +1,35 @@
+//go:build !386 && !arm && !mips && !mipsle && !wasm
+
+package util
+
+import "testing"
+
+func TestTokenizerEncodingForCountCachesSupportedModel(t *testing.T) {
+	encoding, release := tokenizerEncodingForCount(defaultTokenizerModel)
+	if encoding == nil {
+		t.Fatalf("expected tokenizer encoding for %q", defaultTokenizerModel)
+	}
+	release()
+
+	if _, ok := tokenEncodingPools.Load(defaultTokenizerModel); !ok {
+		t.Fatalf("expected tokenizer encoding pool for %q", defaultTokenizerModel)
+	}
+
+	encoding, release = tokenizerEncodingForCount(defaultTokenizerModel)
+	if encoding == nil {
+		t.Fatalf("expected cached tokenizer encoding for %q", defaultTokenizerModel)
+	}
+	release()
+}
+
+func TestTokenizerEncodingForCountCachesUnsupportedModel(t *testing.T) {
+	const model = "__ds2api_unsupported_tokenizer_model__"
+	encoding, release := tokenizerEncodingForCount(model)
+	release()
+	if encoding != nil {
+		t.Fatalf("expected nil encoding for unsupported model %q", model)
+	}
+	if _, ok := tokenEncodingUnsupported.Load(model); !ok {
+		t.Fatalf("expected unsupported tokenizer model to be cached")
+	}
+}