chore(cursor-proxy-debugger): enhance traffic capture for Fork Chat and update README

- Added support for capturing and decoding Fork Chat traffic, including `ForkBackgroundComposer`, `NotifyConversationClone`, and `UploadConversationBlobs`.
- Updated the README to reflect new features and usage instructions for Fork Chat traffic.
- Modified `.gitignore` to include `proto/extensions-cursor-app/`.
- Refactored `Taskfile.yml` to improve error messages related to Cursor extensions.
- Introduced new tests for decoding functionality in `cursor-proxy-debugger`.

cursor-proxy-debugger/README.en.md

@@ -2,7 +2,7 @@
 
 [中文](README.md) | [English](README.en.md)
 
-This standalone local HTTPS debugging proxy captures Cursor's `BidiAppend` and `RunSSE` traffic. It does not modify Cursor, the system proxy, or the installed client.
+This standalone local HTTPS debugging proxy captures Cursor's `BidiAppend`, `RunSSE`, and Fork Chat traffic. It does not modify Cursor, the system proxy, or the installed client.
 
 ## Start
 
@@ -51,6 +51,8 @@ go build -o bin/cursor-proxy-debugger ./cmd/cursor-proxy-debugger
 - HTTPS MITM is applied only to `target-host`; other CONNECT traffic passes through unchanged.
 - `RunSSE` is decoded incrementally using the 5-byte Connect frame header and supports per-frame gzip decompression.
 - `BidiAppendRequest.data` is further decoded as `agent.v1.AgentClientMessage`.
+- Fork Chat's `ForkBackgroundComposer`, `NotifyConversationClone`, and `UploadConversationBlobs` traffic is decoded bidirectionally as protobuf JSON.
+- Local Fork Chat is primarily client-side and only emits `NotifyConversationClone` and `UploadConversationBlobs` when clone blob synchronization is enabled and privacy settings allow it.
 - Requests can be sorted chronologically or in reverse chronological order and filtered by protocol `request_id`.
 - The UI supports Simplified Chinese and English, follows the browser language, and remembers a manual selection.
 - Captured traffic is stored only in process memory and is discarded when the process exits.

cursor-proxy-debugger/README.md

@@ -2,7 +2,7 @@
 
 [中文](README.md) | [English](README.en.md)
 
-这是一个独立运行的本地 HTTPS 调试代理，用于观察 Cursor 的 `BidiAppend` 和 `RunSSE` 通信。它不会修改 Cursor、系统代理或已安装客户端。
+这是一个独立运行的本地 HTTPS 调试代理，用于观察 Cursor 的 `BidiAppend`、`RunSSE` 和 Fork Chat 相关通信。它不会修改 Cursor、系统代理或已安装客户端。
 
 ## 启动
 
@@ -51,6 +51,8 @@ go build -o bin/cursor-proxy-debugger ./cmd/cursor-proxy-debugger
 - 仅对 `target-host` 执行 HTTPS MITM，其他 CONNECT 流量直接透传。
 - `RunSSE` 按 5 字节 Connect 帧头增量拆帧，支持逐帧 gzip 解压。
 - `BidiAppendRequest.data` 会继续解码为 `agent.v1.AgentClientMessage`。
+- Fork Chat 相关的 `ForkBackgroundComposer`、`NotifyConversationClone` 和 `UploadConversationBlobs` 会双向解码为 protobuf JSON。
+- 本地 Fork Chat 主要在客户端完成，只有启用克隆 blob 同步且隐私设置允许时才会产生 `NotifyConversationClone` 和 `UploadConversationBlobs` 流量。
 - 请求列表支持按抓包时间正序/倒序排列，并可按协议中的 `request_id` 过滤。
 - 调试界面支持简体中文和英文，可跟随浏览器语言并记住手动选择。
 - 抓包只保留在当前进程内存中；关闭进程后消失。

cursor-proxy-debugger/decode.go

@@ -20,6 +20,13 @@ import (
 
 const maxConnectFrameBytes = 64 << 20
 
+const (
+	bidiAppendPath              = "/aiserver.v1.BidiService/BidiAppend"
+	forkBackgroundComposerPath  = "/aiserver.v1.BackgroundComposerService/ForkBackgroundComposer"
+	notifyConversationClonePath = "/agent.v1.AgentService/NotifyConversationClone"
+	uploadConversationBlobsPath = "/agent.v1.AgentService/UploadConversationBlobs"
+)
+
 type connectFrameDecoder struct {
 	buffer      []byte
 	messageType string
@@ -140,10 +147,9 @@ func decompressPayload(payload []byte, codec string) ([]byte, error) {
 	return decoded, nil
 }
 
-func decodeUnary(path string, payload []byte) (decodedJSON string, kind string, requestID string, err error) {
-	var message proto.Message
+func decodeUnaryRequest(path string, payload []byte) (decodedJSON string, kind string, requestID string, err error) {
 	switch path {
-	case "/aiserver.v1.BidiService/BidiAppend":
+	case bidiAppendPath:
 		request := &aiserverv1.BidiAppendRequest{}
 		if err := proto.Unmarshal(payload, request); err != nil {
 			return "", "", "", err
@@ -165,13 +171,65 @@ func decodeUnary(path string, payload []byte) (decodedJSON string, kind string,
 		}
 		formatted, marshalErr := json.MarshalIndent(combined, "", "  ")
 		return string(formatted), clientKind, requestID, marshalErr
-	default:
-		message = nil
 	}
+	message, kind := unaryRequestMessage(path)
 	if message == nil {
 		return "", "", "", nil
 	}
-	return marshalProtoJSON(message), activeOneofName(message), "", nil
+	if err := proto.Unmarshal(payload, message); err != nil {
+		return "", "", "", err
+	}
+	return marshalProtoJSON(message), kind, "", nil
+}
+
+func decodeUnaryResponse(path string, payload []byte) (decodedJSON string, kind string, err error) {
+	message, kind := unaryResponseMessage(path)
+	if message == nil {
+		return "", "", nil
+	}
+	if err := proto.Unmarshal(payload, message); err != nil {
+		return "", "", err
+	}
+	return marshalProtoJSON(message), kind, nil
+}
+
+func unaryRequestMessage(path string) (proto.Message, string) {
+	switch path {
+	case forkBackgroundComposerPath:
+		return &aiserverv1.ForkBackgroundComposerRequest{}, "fork_background_composer_request"
+	case notifyConversationClonePath:
+		return &agentv1.NotifyConversationCloneRequest{}, "notify_conversation_clone_request"
+	case uploadConversationBlobsPath:
+		return &agentv1.UploadConversationBlobsRequest{}, "upload_conversation_blobs_request"
+	default:
+		return nil, ""
+	}
+}
+
+func unaryResponseMessage(path string) (proto.Message, string) {
+	switch path {
+	case forkBackgroundComposerPath:
+		return &aiserverv1.ForkBackgroundComposerResponse{}, "fork_background_composer_response"
+	case notifyConversationClonePath:
+		return &agentv1.NotifyConversationCloneResponse{}, "notify_conversation_clone_response"
+	case uploadConversationBlobsPath:
+		return &agentv1.UploadConversationBlobsResponse{}, "upload_conversation_blobs_response"
+	default:
+		return nil, ""
+	}
+}
+
+func decodesUnaryRequest(path string) bool {
+	if path == bidiAppendPath {
+		return true
+	}
+	message, _ := unaryRequestMessage(path)
+	return message != nil
+}
+
+func decodesUnaryResponse(path string) bool {
+	message, _ := unaryResponseMessage(path)
+	return message != nil
 }
 
 func newMessage(messageType string) proto.Message {

cursor-proxy-debugger/decode_test.go

@@ -0,0 +1,242 @@
+package proxydebugger
+
+import (
+	"bytes"
+	"compress/gzip"
+	"encoding/json"
+	"strings"
+	"testing"
+	"time"
+
+	"cursor/gen/agentv1"
+	"cursor/gen/aiserverv1"
+
+	"google.golang.org/protobuf/proto"
+)
+
+func TestDecodeForkTrafficRequests(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		path     string
+		message  proto.Message
+		kind     string
+		contains []string
+	}{
+		{
+			name: "fork background composer",
+			path: forkBackgroundComposerPath,
+			message: &aiserverv1.ForkBackgroundComposerRequest{
+				SourceBcId: "bc-source",
+				Mode:       aiserverv1.ForkBackgroundComposerMode_FORK_BACKGROUND_COMPOSER_MODE_CONVERSATION,
+				Name:       proto.String("forked chat"),
+				TurnCount:  proto.Uint32(4),
+			},
+			kind:     "fork_background_composer_request",
+			contains: []string{`"source_bc_id":"bc-source"`, `"turn_count":4`},
+		},
+		{
+			name: "notify conversation clone",
+			path: notifyConversationClonePath,
+			message: &agentv1.NotifyConversationCloneRequest{
+				ConversationId:       "new-conversation",
+				SourceConversationId: "source-conversation",
+				SourceRequestId:      "source-request",
+			},
+			kind:     "notify_conversation_clone_request",
+			contains: []string{`"conversation_id":"new-conversation"`, `"source_conversation_id":"source-conversation"`},
+		},
+		{
+			name: "upload conversation blobs",
+			path: uploadConversationBlobsPath,
+			message: &agentv1.UploadConversationBlobsRequest{
+				ConversationId: "new-conversation",
+				Blobs: []*agentv1.BlobEntry{{
+					Id:    []byte{1, 2},
+					Value: []byte("blob-value"),
+				}},
+				ChunkIndex:  1,
+				TotalChunks: 2,
+			},
+			kind:     "upload_conversation_blobs_request",
+			contains: []string{`"conversation_id":"new-conversation"`, `"total_chunks":2`, `"value":"YmxvYi12YWx1ZQ=="`},
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+			payload, err := proto.Marshal(test.message)
+			if err != nil {
+				t.Fatal(err)
+			}
+			decoded, kind, requestID, err := decodeUnaryRequest(test.path, payload)
+			if err != nil {
+				t.Fatalf("decode request: %v", err)
+			}
+			if kind != test.kind {
+				t.Fatalf("kind = %q, want %q", kind, test.kind)
+			}
+			if requestID != "" {
+				t.Fatalf("request ID = %q, want empty", requestID)
+			}
+			compact := compactJSON(t, decoded)
+			for _, expected := range test.contains {
+				if !strings.Contains(compact, expected) {
+					t.Errorf("decoded JSON does not contain %q:\n%s", expected, decoded)
+				}
+			}
+		})
+	}
+}
+
+func TestDecodeForkTrafficResponses(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		path     string
+		message  proto.Message
+		kind     string
+		contains string
+	}{
+		{
+			name: "fork background composer",
+			path: forkBackgroundComposerPath,
+			message: &aiserverv1.ForkBackgroundComposerResponse{
+				BcId:       "bc-fork",
+				SourceBcId: "bc-source",
+				Mode:       aiserverv1.ForkBackgroundComposerMode_FORK_BACKGROUND_COMPOSER_MODE_CONVERSATION,
+			},
+			kind:     "fork_background_composer_response",
+			contains: `"bc_id":"bc-fork"`,
+		},
+		{
+			name:     "notify conversation clone",
+			path:     notifyConversationClonePath,
+			message:  &agentv1.NotifyConversationCloneResponse{},
+			kind:     "notify_conversation_clone_response",
+			contains: `{}`,
+		},
+		{
+			name:     "upload conversation blobs",
+			path:     uploadConversationBlobsPath,
+			message:  &agentv1.UploadConversationBlobsResponse{},
+			kind:     "upload_conversation_blobs_response",
+			contains: `{}`,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+			payload, err := proto.Marshal(test.message)
+			if err != nil {
+				t.Fatal(err)
+			}
+			decoded, kind, err := decodeUnaryResponse(test.path, payload)
+			if err != nil {
+				t.Fatalf("decode response: %v", err)
+			}
+			if kind != test.kind {
+				t.Fatalf("kind = %q, want %q", kind, test.kind)
+			}
+			if !strings.Contains(compactJSON(t, decoded), test.contains) {
+				t.Errorf("decoded JSON does not contain %q:\n%s", test.contains, decoded)
+			}
+		})
+	}
+}
+
+func TestFinishResponseBodyDecodesCompressedForkResponse(t *testing.T) {
+	t.Parallel()
+
+	payload, err := proto.Marshal(&aiserverv1.ForkBackgroundComposerResponse{
+		BcId:       "bc-fork",
+		SourceBcId: "bc-source",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var compressed bytes.Buffer
+	writer := gzip.NewWriter(&compressed)
+	if _, err := writer.Write(payload); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	server := &Server{store: newExchangeStore(1)}
+	server.store.create(&Exchange{
+		ExchangeSummary: ExchangeSummary{ID: "1", StartedAt: time.Now()},
+	})
+	server.finishResponseBody("1", forkBackgroundComposerPath, "gzip", compressed.Bytes(), int64(compressed.Len()), false, nil)
+
+	exchange, ok := server.store.get("1")
+	if !ok {
+		t.Fatal("exchange was not stored")
+	}
+	if exchange.ResponseKind != "fork_background_composer_response" {
+		t.Fatalf("response kind = %q", exchange.ResponseKind)
+	}
+	if !strings.Contains(compactJSON(t, exchange.Response.DecodedJSON), `"bc_id":"bc-fork"`) {
+		t.Fatalf("unexpected decoded response:\n%s", exchange.Response.DecodedJSON)
+	}
+	if exchange.Response.DecodeError != "" {
+		t.Fatalf("decode error = %q", exchange.Response.DecodeError)
+	}
+}
+
+func TestFinishRequestBodyDecodesCompressedCloneRequest(t *testing.T) {
+	t.Parallel()
+
+	payload, err := proto.Marshal(&agentv1.NotifyConversationCloneRequest{
+		ConversationId:       "new-conversation",
+		SourceConversationId: "source-conversation",
+		SourceRequestId:      "source-request",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var compressed bytes.Buffer
+	writer := gzip.NewWriter(&compressed)
+	if _, err := writer.Write(payload); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	server := &Server{store: newExchangeStore(1)}
+	server.store.create(&Exchange{
+		ExchangeSummary: ExchangeSummary{ID: "1", StartedAt: time.Now()},
+	})
+	server.finishRequestBody("1", notifyConversationClonePath, "gzip", compressed.Bytes(), int64(compressed.Len()), false, nil)
+
+	exchange, ok := server.store.get("1")
+	if !ok {
+		t.Fatal("exchange was not stored")
+	}
+	if exchange.RequestKind != "notify_conversation_clone_request" {
+		t.Fatalf("request kind = %q", exchange.RequestKind)
+	}
+	if !strings.Contains(compactJSON(t, exchange.Request.DecodedJSON), `"source_conversation_id":"source-conversation"`) {
+		t.Fatalf("unexpected decoded request:\n%s", exchange.Request.DecodedJSON)
+	}
+	if exchange.Request.DecodeError != "" {
+		t.Fatalf("decode error = %q", exchange.Request.DecodeError)
+	}
+}
+
+func compactJSON(t *testing.T, value string) string {
+	t.Helper()
+	var compact bytes.Buffer
+	if err := json.Compact(&compact, []byte(value)); err != nil {
+		t.Fatalf("compact JSON: %v\n%s", err, value)
+	}
+	return compact.String()
+}

cursor-proxy-debugger/proxy.go

@@ -226,28 +226,29 @@ func (server *Server) captureResponse(response *http.Response, context *goproxy.
 	if id == "" || response == nil {
 		return response
 	}
+	path := ""
+	if response.Request != nil && response.Request.URL != nil {
+		path = response.Request.URL.Path
+	}
+	responseCodec := responseContentCodec(path, response.Header)
 	server.store.update(id, func(exchange *Exchange) {
 		exchange.Status = response.StatusCode
 		exchange.State = "streaming"
 		exchange.DurationMS = elapsedMS(exchange.StartedAt)
 		exchange.Response.Headers = sortedHeaders(response.Header)
 		exchange.Response.ContentType = response.Header.Get("Content-Type")
-		exchange.Response.ContentCodec = responseContentCodec(response.Header)
+		exchange.Response.ContentCodec = responseCodec
 	})
 	if response.Body == nil {
-		server.finishResponseBody(id, nil, 0, false, nil)
+		server.finishResponseBody(id, path, responseCodec, nil, 0, false, nil)
 		return response
 	}
 
-	path := ""
-	if response.Request != nil && response.Request.URL != nil {
-		path = response.Request.URL.Path
-	}
 	var frameDecoder *connectFrameDecoder
 	if path == "/agent.v1.AgentService/RunSSE" {
 		frameDecoder = newConnectFrameDecoder(
 			"agent.v1.AgentServerMessage",
-			response.Header.Get("Connect-Content-Encoding"),
+			responseCodec,
 			server.config.MaxFrames,
 			func(frame FrameView) { server.appendResponseFrame(id, frame) },
 		)
@@ -264,7 +265,7 @@ func (server *Server) captureResponse(response *http.Response, context *goproxy.
 			if frameDecoder != nil {
 				frameDecoder.Close()
 			}
-			server.finishResponseBody(id, captured, size, truncated, readErr)
+			server.finishResponseBody(id, path, responseCodec, captured, size, truncated, readErr)
 		},
 	)
 	return response
@@ -273,14 +274,14 @@ func (server *Server) captureResponse(response *http.Response, context *goproxy.
 func (server *Server) finishRequestBody(id, path string, codec string, captured []byte, size int64, truncated bool, readErr error) {
 	decodePayload := captured
 	var contentDecodeErr error
-	if path == "/aiserver.v1.BidiService/BidiAppend" && truncated {
+	if decodesUnaryRequest(path) && truncated {
 		contentDecodeErr = errors.New("请求正文超过抓取上限，无法完整解码")
-	} else if path == "/aiserver.v1.BidiService/BidiAppend" && codec != "" && !strings.EqualFold(codec, "identity") {
+	} else if decodesUnaryRequest(path) && codec != "" && !strings.EqualFold(codec, "identity") {
 		decodePayload, contentDecodeErr = decompressPayload(captured, codec)
 	}
 	decodedJSON, kind, requestID, decodeErr := "", "", "", contentDecodeErr
 	if decodeErr == nil {
-		decodedJSON, kind, requestID, decodeErr = decodeUnary(path, decodePayload)
+		decodedJSON, kind, requestID, decodeErr = decodeUnaryRequest(path, decodePayload)
 	}
 	server.store.update(id, func(exchange *Exchange) {
 		exchange.RequestBytes = size
@@ -312,19 +313,44 @@ func requestContentCodec(path string, headers http.Header) string {
 	return strings.TrimSpace(headers.Get("Content-Encoding"))
 }
 
-func responseContentCodec(headers http.Header) string {
-	if codec := strings.TrimSpace(headers.Get("Connect-Content-Encoding")); codec != "" {
-		return codec
+func responseContentCodec(path string, headers http.Header) string {
+	if path == "/agent.v1.AgentService/RunSSE" {
+		return strings.TrimSpace(headers.Get("Connect-Content-Encoding"))
+	}
+	if !decodesUnaryResponse(path) {
+		if codec := strings.TrimSpace(headers.Get("Connect-Content-Encoding")); codec != "" {
+			return codec
+		}
 	}
 	return strings.TrimSpace(headers.Get("Content-Encoding"))
 }
 
-func (server *Server) finishResponseBody(id string, captured []byte, size int64, truncated bool, readErr error) {
+func (server *Server) finishResponseBody(id, path, codec string, captured []byte, size int64, truncated bool, readErr error) {
+	decodePayload := captured
+	var contentDecodeErr error
+	if decodesUnaryResponse(path) && truncated {
+		contentDecodeErr = errors.New("响应正文超过抓取上限，无法完整解码")
+	} else if decodesUnaryResponse(path) && codec != "" && !strings.EqualFold(codec, "identity") {
+		decodePayload, contentDecodeErr = decompressPayload(captured, codec)
+	}
+	decodedJSON, kind, decodeErr := "", "", contentDecodeErr
+	if decodeErr == nil {
+		decodedJSON, kind, decodeErr = decodeUnaryResponse(path, decodePayload)
+	}
 	server.store.update(id, func(exchange *Exchange) {
 		exchange.ResponseBytes = size
 		exchange.Response.Size = size
 		exchange.Response.RawHex = rawHex(captured)
 		exchange.Response.RawTruncated = truncated
+		if decodedJSON != "" {
+			exchange.Response.DecodedJSON = decodedJSON
+		}
+		if kind != "" {
+			exchange.ResponseKind = kind
+		}
+		if decodeErr != nil {
+			exchange.Response.DecodeError = decodeErr.Error()
+		}
 		exchange.DurationMS = elapsedMS(exchange.StartedAt)
 		exchange.State = "completed"
 		if readErr != nil && !errors.Is(readErr, io.EOF) {

cursor-proxy-debugger/web/app.js

@@ -138,6 +138,7 @@ function filteredExchanges() {
     .filter((item) => {
       if (state.endpoint === "runsse" && !item.path.toLowerCase().includes("runsse")) return false;
       if (state.endpoint === "bidiappend" && !item.path.toLowerCase().includes("bidiappend")) return false;
+      if (state.endpoint === "fork" && !isForkTrafficPath(item.path)) return false;
       if (requestId && !String(item.requestId || "").toLowerCase().includes(requestId)) return false;
       if (!query) return true;
       return [item.url, item.requestId, item.requestKind, item.responseKind, item.state, String(item.status)]
@@ -151,6 +152,13 @@ function filteredExchanges() {
     });
 }
 
+function isForkTrafficPath(path) {
+  const normalized = String(path || "").toLowerCase();
+  return ["forkbackgroundcomposer", "notifyconversationclone", "uploadconversationblobs"].some((endpoint) =>
+    normalized.includes(endpoint),
+  );
+}
+
 function renderList() {
   const exchanges = filteredExchanges();
   elements.requestCount.textContent = t("count.requests", { count: exchanges.length });

cursor-proxy-debugger/web/i18n.js

@@ -22,6 +22,7 @@ const messages = {
     "filters.requestIdPlaceholder": "按 Request ID 过滤",
     "filters.endpoint": "接口过滤",
     "filters.all": "全部",
+    "filters.fork": "Fork",
     "filters.sort": "排序方向",
     "filters.ascending": "正序",
     "filters.descending": "倒序",
@@ -81,6 +82,7 @@ const messages = {
     "filters.requestIdPlaceholder": "Filter by Request ID",
     "filters.endpoint": "Endpoint filter",
     "filters.all": "All",
+    "filters.fork": "Fork",
     "filters.sort": "Sort order",
     "filters.ascending": "Oldest first",
     "filters.descending": "Newest first",

cursor-proxy-debugger/web/index.html

@@ -46,6 +46,7 @@
           <button class="active" type="button" data-value="all" data-i18n="filters.all">全部</button>
           <button type="button" data-value="runsse">RunSSE</button>
           <button type="button" data-value="bidiappend">BidiAppend</button>
+          <button type="button" data-value="fork" data-i18n="filters.fork">Fork</button>
         </div>
         <div id="sort-order" class="segmented-control sort-control" role="group" aria-label="排序方向" data-i18n-aria-label="filters.sort">
           <button type="button" data-value="asc" data-i18n="filters.ascending">正序</button>