feat(admin): Agent 并发 - 后台可调同时对话上限并展示 Agent 服务状态

新增运行策略 agentMaxSessions（默认 30，范围 1-64），保存后同时下发到内嵌进程闸门与独立 yingce-agent 的 /v1/limit，降低上限不会中断已开始的对话。系统性能页展示 Agent 服务健康、进行中/排队数量，并可直接修改上限。

backend/internal/agent/runtime/runtime.go

@@ -222,27 +222,83 @@ func RuntimeDir() (string, error) {
 	return "", errors.New("Agent runtime files are missing; set CANVAS_PI_RUNTIME_DIR")
 }
 
-var (
-	agentSlotsOnce sync.Once
-	agentSlots     chan struct{}
+const (
+	defaultAgentProcessLimit = 30
+	maxAgentProcessLimit     = 64
 )
 
-func acquireAgentProcess(ctx context.Context) (func(), error) {
-	agentSlotsOnce.Do(func() {
-		limit := 8
-		if raw := strings.TrimSpace(os.Getenv("CANVAS_AGENT_MAX_PROCESSES")); raw != "" {
-			if parsed, err := strconv.Atoi(raw); err == nil && parsed > 0 && parsed <= 1000 {
-				limit = parsed
-			}
+type agentProcessGate struct {
+	mu     sync.Mutex
+	limit  int
+	active int
+	wake   chan struct{}
+}
+
+var processGate = newAgentProcessGate()
+
+func newAgentProcessGate() *agentProcessGate {
+	limit := defaultAgentProcessLimit
+	if raw := strings.TrimSpace(os.Getenv("CANVAS_AGENT_MAX_PROCESSES")); raw != "" {
+		if parsed, err := strconv.Atoi(raw); err == nil {
+			limit = clampAgentProcessLimit(parsed)
 		}
-		agentSlots = make(chan struct{}, limit)
-	})
-	select {
-	case agentSlots <- struct{}{}:
-		return func() { <-agentSlots }, nil
-	case <-ctx.Done():
-		return nil, ctx.Err()
 	}
+	return &agentProcessGate{limit: limit, wake: make(chan struct{})}
+}
+
+func clampAgentProcessLimit(value int) int {
+	if value < 1 {
+		return defaultAgentProcessLimit
+	}
+	if value > maxAgentProcessLimit {
+		return maxAgentProcessLimit
+	}
+	return value
+}
+
+// SetProcessLimit changes how many embedded Agent processes may run at once.
+// Lowering the limit does not stop a process that has already started.
+func SetProcessLimit(value int) (active int, limit int) {
+	processGate.mu.Lock()
+	defer processGate.mu.Unlock()
+	processGate.limit = clampAgentProcessLimit(value)
+	close(processGate.wake)
+	processGate.wake = make(chan struct{})
+	return processGate.active, processGate.limit
+}
+
+func ProcessUsage() (active int, limit int) {
+	processGate.mu.Lock()
+	defer processGate.mu.Unlock()
+	return processGate.active, processGate.limit
+}
+
+func acquireAgentProcess(ctx context.Context) (func(), error) {
+	for {
+		processGate.mu.Lock()
+		if processGate.active < processGate.limit {
+			processGate.active++
+			processGate.mu.Unlock()
+			return releaseAgentProcess, nil
+		}
+		wake := processGate.wake
+		processGate.mu.Unlock()
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case <-wake:
+		}
+	}
+}
+
+func releaseAgentProcess() {
+	processGate.mu.Lock()
+	if processGate.active > 0 {
+		processGate.active--
+	}
+	close(processGate.wake)
+	processGate.wake = make(chan struct{})
+	processGate.mu.Unlock()
 }
 
 func nodeMemoryMB() string {

backend/internal/agent/runtime/runtime_test.go

@@ -24,6 +24,25 @@ func fakeRuntime(t *testing.T, script string) {
 	t.Setenv("CANVAS_PI_RUNTIME_DIR", dir)
 }
 
+func TestSetProcessLimitDoesNotStopActiveWork(t *testing.T) {
+	t.Cleanup(func() { SetProcessLimit(defaultAgentProcessLimit) })
+	release, err := acquireAgentProcess(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	active, limit := SetProcessLimit(1)
+	if active != 1 || limit != 1 {
+		t.Fatalf("active=%d limit=%d, want active 1 and limit 1", active, limit)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Millisecond)
+	defer cancel()
+	if _, err := acquireAgentProcess(ctx); err == nil {
+		t.Fatal("lowered limit still admitted another process")
+	}
+	release()
+	SetProcessLimit(defaultAgentProcessLimit)
+}
+
 func noopBridge() Bridge {
 	handler := func(context.Context, map[string]json.RawMessage) (any, error) { return map[string]any{"ok": true}, nil }
 	return Bridge{Model: handler, Tool: handler, Event: handler}

backend/internal/agent/yingceagent/client.go

@@ -14,6 +14,68 @@ import (
 	agentruntime "infinite-canvas/backend/internal/agent/runtime"
 )
 
+type Status struct {
+	OK     bool `json:"ok"`
+	Active int  `json:"active"`
+	Limit  int  `json:"limit"`
+	Queued int  `json:"queued"`
+}
+
+func Inspect(ctx context.Context, endpoint string) (Status, error) {
+	endpoint = strings.TrimRight(strings.TrimSpace(endpoint), "/")
+	if endpoint == "" {
+		return Status{}, fmt.Errorf("YINGCE_AGENT_URL is empty")
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint+"/healthz", nil)
+	if err != nil {
+		return Status{}, err
+	}
+	response, err := remoteClient.Do(request)
+	if err != nil {
+		return Status{}, err
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		return Status{}, fmt.Errorf("yingce-agent health returned HTTP %d", response.StatusCode)
+	}
+	var status Status
+	if err := json.NewDecoder(io.LimitReader(response.Body, 4096)).Decode(&status); err != nil {
+		return Status{}, err
+	}
+	return status, nil
+}
+
+func SetLimit(ctx context.Context, endpoint, serviceToken string, limit int) error {
+	endpoint = strings.TrimRight(strings.TrimSpace(endpoint), "/")
+	serviceToken = strings.TrimSpace(serviceToken)
+	if endpoint == "" {
+		return fmt.Errorf("YINGCE_AGENT_URL is empty")
+	}
+	if len(serviceToken) < 32 {
+		return fmt.Errorf("YINGCE_AGENT_TOKEN must contain at least 32 characters")
+	}
+	payload, err := json.Marshal(map[string]int{"maxSessions": limit})
+	if err != nil {
+		return err
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodPut, endpoint+"/v1/limit", bytes.NewReader(payload))
+	if err != nil {
+		return err
+	}
+	request.Header.Set("Authorization", "Bearer "+serviceToken)
+	request.Header.Set("Content-Type", "application/json")
+	response, err := remoteClient.Do(request)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		detail, _ := io.ReadAll(io.LimitReader(response.Body, 1024))
+		return fmt.Errorf("yingce-agent limit returned HTTP %d: %s", response.StatusCode, strings.TrimSpace(string(detail)))
+	}
+	return nil
+}
+
 // Run executes one Agent session on the independent yingce-agent service.
 // The Go process keeps the bridge, billing, and tool execution. A configured
 // remote endpoint never falls back to an embedded Node process: doing so can

backend/internal/agent/yingceagent/client_test.go

@@ -116,4 +116,14 @@ if (!response.ok) {
 	if !called {
 		t.Fatal("remote runtime did not call the Go tool bridge")
 	}
+	if err := SetLimit(ctx, endpoint, token, 16); err != nil {
+		t.Fatal(err)
+	}
+	status, err := Inspect(ctx, endpoint)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if status.Limit != 16 {
+		t.Fatalf("limit = %d, want 16", status.Limit)
+	}
 }

backend/internal/app/admin_system_performance.go

@@ -3,14 +3,18 @@ package app
 import (
 	"context"
 	"errors"
+	"fmt"
 	"os"
 	"runtime"
 	"strconv"
 	"strings"
 	"time"
 
+	agentruntime "infinite-canvas/backend/internal/agent/runtime"
+	"infinite-canvas/backend/internal/agent/yingceagent"
 	"infinite-canvas/backend/internal/buildinfo"
 	"infinite-canvas/backend/internal/model"
+	"infinite-canvas/backend/internal/platform"
 	"infinite-canvas/backend/internal/repository"
 
 	"github.com/redis/go-redis/v9"
@@ -28,9 +32,23 @@ type AdminSystemPerformance struct {
 	Disk        SystemPerformanceDisk           `json:"disk"`
 	Database    repository.DatabaseRuntimeStats `json:"database"`
 	Redis       SystemPerformanceRedis          `json:"redis"`
+	Agents      []SystemPerformanceAgent        `json:"agents"`
 	Build       buildinfo.Info                  `json:"build"`
 }
 
+type SystemPerformanceAgent struct {
+	ID              string `json:"id"`
+	Name            string `json:"name"`
+	Mode            string `json:"mode"`
+	Endpoint        string `json:"endpoint"`
+	Healthy         bool   `json:"healthy"`
+	Active          int    `json:"active"`
+	Limit           int    `json:"limit"`
+	Queued          int    `json:"queued"`
+	ConfiguredLimit int    `json:"configuredLimit"`
+	StatusMessage   string `json:"statusMessage,omitempty"`
+}
+
 type SystemPerformanceHost struct {
 	Hostname             string     `json:"hostname"`
 	OS                   string     `json:"os"`
@@ -149,17 +167,98 @@ func (s *Service) AdminSystemPerformance(ctx context.Context, actor *model.User)
 	disk := collectSystemDisk(s.dataDir)
 	databaseStats, databaseErr := s.repo.DatabaseRuntimeStats(ctx)
 	redisStats := s.collectRedisPerformance(ctx)
+	agents := s.collectAgentServices(ctx)
 	status := "healthy"
-	if databaseErr != nil || !databaseStats.Connected || !disk.Available || !disk.Writable || s.ValidateRuntime() != nil || (redisStats.Configured && !redisStats.Connected) {
+	if databaseErr != nil || !databaseStats.Connected || !disk.Available || !disk.Writable || s.ValidateRuntime() != nil || (redisStats.Configured && !redisStats.Connected) || agentServicesDegraded(agents) {
 		status = "degraded"
 	}
 	return &AdminSystemPerformance{
 		CollectedAt: time.Now(), Status: status,
 		Host:   SystemPerformanceHost{Hostname: hostname, OS: runtime.GOOS, Arch: runtime.GOARCH, CPUCores: runtime.NumCPU(), GOMAXPROCS: runtime.GOMAXPROCS(0), ProcessID: os.Getpid(), UptimeSeconds: int64(time.Since(systemProcessStartedAt).Seconds()), Goroutines: runtime.NumGoroutine(), ActiveWorkerTasks: s.ActiveWorkerTasks(), LoadAverage: load, LoadAverageAvailable: loadAvailable},
-		Memory: memory, Disk: disk, Database: databaseStats, Redis: redisStats, Build: buildinfo.Current(),
+		Memory: memory, Disk: disk, Database: databaseStats, Redis: redisStats, Agents: agents, Build: buildinfo.Current(),
 	}, nil
 }
 
+type AgentSessionLimitRequest struct {
+	MaxSessions int `json:"maxSessions"`
+}
+
+func (s *Service) UpdateAgentSessionLimit(ctx context.Context, actor *model.User, maxSessions int) (*SystemPerformanceAgent, error) {
+	if err := s.RequireAdmin(actor); err != nil {
+		return nil, err
+	}
+	if maxSessions < platform.MinRuntimeAgentSessions || maxSessions > platform.MaxRuntimeAgentSessions {
+		return nil, BadAuthRequest(fmt.Sprintf("Agent 同时对话上限必须是 %d-%d 的整数", platform.MinRuntimeAgentSessions, platform.MaxRuntimeAgentSessions))
+	}
+	policy, err := s.RuntimePolicy()
+	if err != nil {
+		return nil, err
+	}
+	policy.Task.AgentMaxSessions = maxSessions
+	if _, err := s.UpdateRuntimePolicySetting(actor, policy); err != nil {
+		return nil, err
+	}
+	if err := s.applyAgentSessionLimit(ctx, maxSessions); err != nil {
+		return nil, err
+	}
+	agents := s.collectAgentServices(ctx)
+	if len(agents) == 0 {
+		return nil, fmt.Errorf("Agent 服务状态不可用")
+	}
+	return &agents[0], nil
+}
+
+func (s *Service) applyAgentSessionLimit(ctx context.Context, maxSessions int) error {
+	agentruntime.SetProcessLimit(maxSessions)
+	endpoint := strings.TrimSpace(os.Getenv("YINGCE_AGENT_URL"))
+	if endpoint == "" {
+		return nil
+	}
+	return yingceagent.SetLimit(ctx, endpoint, os.Getenv("YINGCE_AGENT_TOKEN"), maxSessions)
+}
+
+func (s *Service) collectAgentServices(ctx context.Context) []SystemPerformanceAgent {
+	configured := platform.DefaultRuntimeAgentSessions
+	if policy, err := s.RuntimePolicy(); err == nil && policy.Task.AgentMaxSessions > 0 {
+		configured = policy.Task.AgentMaxSessions
+	}
+	endpoint := strings.TrimSpace(os.Getenv("YINGCE_AGENT_URL"))
+	if endpoint == "" {
+		active, limit := agentruntime.ProcessUsage()
+		return []SystemPerformanceAgent{{
+			ID: "embedded", Name: "画布 Agent", Mode: "embedded", Endpoint: "本进程",
+			Healthy: true, Active: active, Limit: limit, ConfiguredLimit: configured,
+			StatusMessage: "本地开发由后端进程直接启动，不单独占用容器。",
+		}}
+	}
+	service := SystemPerformanceAgent{
+		ID: "yingce-agent", Name: "画布 Agent", Mode: "remote", Endpoint: endpoint,
+		ConfiguredLimit: configured,
+	}
+	status, err := yingceagent.Inspect(ctx, endpoint)
+	if err != nil {
+		service.StatusMessage = "独立 Agent 服务不可达。正在进行的对话会失败，不会自动改回本进程执行。"
+		return []SystemPerformanceAgent{service}
+	}
+	service.Healthy = status.OK
+	service.Active = status.Active
+	service.Limit = status.Limit
+	service.Queued = status.Queued
+	if status.Limit != configured {
+		service.StatusMessage = "运行中的上限与已保存配置不一致，重新保存一次即可应用。"
+	}
+	return []SystemPerformanceAgent{service}
+}
+
+func agentServicesDegraded(agents []SystemPerformanceAgent) bool {
+	for _, agent := range agents {
+		if !agent.Healthy {
+			return true
+		}
+	}
+	return false
+}
+
 func collectSystemMemory() SystemPerformanceMemory {
 	var stats runtime.MemStats
 	runtime.ReadMemStats(&stats)

backend/internal/app/cloud_agent_step_timeout_test.go

@@ -161,6 +161,7 @@ func TestRuntimePolicyBackfillsAgentStepLimitsForLegacyJSON(t *testing.T) {
 	task := value["task"].(map[string]any)
 	delete(task, "agentStepMaxOutputTokens")
 	delete(task, "agentStepTimeoutSeconds")
+	delete(task, "agentMaxSessions")
 	trimmed, err := json.Marshal(value)
 	if err != nil {
 		t.Fatal(err)
@@ -176,6 +177,9 @@ func TestRuntimePolicyBackfillsAgentStepLimitsForLegacyJSON(t *testing.T) {
 	if effective.Task.AgentStepMaxOutputTokens != platform.DefaultRuntimeAgentStepOutputTokens {
 		t.Fatalf("legacy json 未回填单步输出上限: %d", effective.Task.AgentStepMaxOutputTokens)
 	}
+	if effective.Task.AgentMaxSessions != platform.DefaultRuntimeAgentSessions {
+		t.Fatalf("legacy json 未回填同时对话上限: %d", effective.Task.AgentMaxSessions)
+	}
 	if effective.Task.AgentStepTimeoutSeconds != platform.DefaultRuntimeAgentStepTimeout {
 		t.Fatalf("legacy json 未回填单步超时: %d", effective.Task.AgentStepTimeoutSeconds)
 	}

backend/internal/app/service.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log/slog"
 	"strings"
 	"sync"
 	"time"
@@ -166,6 +167,7 @@ func (s *Service) StartWorker() {
 	s.startResourceDeletionWorker(ctx)
 	s.startSkillSyncWorker(ctx)
 	s.startPaymentWorker(ctx)
+	go s.syncAgentSessionLimit()
 	s.runWorkerLoop(func(ctx context.Context) {
 		ticker := time.NewTicker(3 * time.Second)
 		defer ticker.Stop()
@@ -180,6 +182,19 @@ func (s *Service) StartWorker() {
 	})
 }
 
+func (s *Service) syncAgentSessionLimit() {
+	policy, err := s.RuntimePolicy()
+	if err != nil {
+		slog.Warn("agent session limit load failed", "error", err)
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	if err := s.applyAgentSessionLimit(ctx, policy.Task.AgentMaxSessions); err != nil {
+		slog.Warn("agent session limit apply failed", "error", err)
+	}
+}
+
 func (s *Service) BeginDrain() { s.backgroundWorkers().BeginDrain() }
 
 func (s *Service) StopWorker(ctx context.Context) error { return s.backgroundWorkers().Stop(ctx) }

backend/internal/handler/admin_system_performance.go

@@ -23,6 +23,26 @@ func RegisterAdminSystemPerformanceRoutes(r *gin.RouterGroup, svc *service.Servi
 		ok(c, result)
 	})
 
+	r.PUT("/admin/system-performance/agent-limit", func(c *gin.Context) {
+		actor, err := currentUser(c, svc)
+		if err != nil {
+			failService(c, err)
+			return
+		}
+		c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 4<<10)
+		var request service.AgentSessionLimitRequest
+		if err := c.ShouldBindJSON(&request); err != nil {
+			failService(c, service.BadAuthRequest("Agent 并发请求无效"))
+			return
+		}
+		result, err := svc.UpdateAgentSessionLimit(c.Request.Context(), actor, request.MaxSessions)
+		if err != nil {
+			failService(c, err)
+			return
+		}
+		ok(c, result)
+	})
+
 	r.POST("/admin/system-performance/cache/clear", func(c *gin.Context) {
 		actor, err := currentUser(c, svc)
 		if err != nil {

backend/internal/handler/admin_system_performance_test.go

@@ -14,6 +14,7 @@ func TestAdminSystemPerformanceRoutesAreRegistered(t *testing.T) {
 	RegisterAdminSystemPerformanceRoutes(router.Group("/api"), &service.Service{})
 	wanted := map[string]bool{
 		"GET /api/admin/system-performance":              false,
+		"PUT /api/admin/system-performance/agent-limit":  false,
 		"POST /api/admin/system-performance/cache/clear": false,
 	}
 	for _, route := range router.Routes() {

backend/internal/platform/runtime_policy.go

@@ -36,6 +36,9 @@ const (
 	MinRuntimeAgentStepTimeoutSeconds   = 30
 	MaxRuntimeAgentStepTimeoutSeconds   = 3_600
 	DefaultRuntimeAgentStepTimeout      = 0
+	MinRuntimeAgentSessions             = 1
+	MaxRuntimeAgentSessions             = 64
+	DefaultRuntimeAgentSessions         = 30
 )
 
 // agentStepMaxOutputTokensDefault 读取部署级覆盖并按同一套范围夹取；环境变量无法表达"不限制"（0），
@@ -90,6 +93,8 @@ type RuntimeTaskPolicy struct {
 	AgentStepMaxOutputTokens int `json:"agentStepMaxOutputTokens"`
 	// AgentStepTimeoutSeconds 是画布 Agent 单步模型调用的秒级墙钟；0 表示沿用文本任务超时。
 	AgentStepTimeoutSeconds int `json:"agentStepTimeoutSeconds"`
+	// AgentMaxSessions 是同时进行中的画布 Agent 轮次上限。审批等待不占用名额。
+	AgentMaxSessions int `json:"agentMaxSessions"`
 }
 
 type RuntimeRequestPolicy struct {
@@ -173,6 +178,7 @@ func DefaultRuntimePolicy() RuntimePolicySetting {
 			DefaultTimeoutMinutes:    10,
 			AgentStepMaxOutputTokens: agentStepMaxOutputTokensDefault(),
 			AgentStepTimeoutSeconds:  agentStepTimeoutSecondsDefault(),
+			AgentMaxSessions:         DefaultRuntimeAgentSessions,
 		},
 		Request: RuntimeRequestPolicy{
 			TaskCreatePerMinute:        30,
@@ -213,6 +219,7 @@ func selfUseRuntimePolicy() RuntimePolicySetting {
 		AudioTimeoutMinutes: maxRuntimeTimeoutMinutes, VideoTimeoutMinutes: maxRuntimeTimeoutMinutes,
 		StoryboardTimeoutMinutes: maxRuntimeTimeoutMinutes, DefaultTimeoutMinutes: maxRuntimeTimeoutMinutes,
 		AgentStepMaxOutputTokens: MaxRuntimeAgentStepOutputTokens, AgentStepTimeoutSeconds: MaxRuntimeAgentStepTimeoutSeconds,
+		AgentMaxSessions: MaxRuntimeAgentSessions,
 	}
 	value.Request = RuntimeRequestPolicy{
 		TaskCreatePerMinute:     maxRuntimeRate,
@@ -437,6 +444,9 @@ func validateRuntimePolicy(value RuntimePolicySetting) error {
 	if task.AgentStepTimeoutSeconds != 0 && (task.AgentStepTimeoutSeconds < MinRuntimeAgentStepTimeoutSeconds || task.AgentStepTimeoutSeconds > MaxRuntimeAgentStepTimeoutSeconds) {
 		return kernel.BadAuthRequest(fmt.Sprintf("Agent 单步超时必须是 0 或 %d-%d 秒的整数 (0 表示沿用文本任务超时)", MinRuntimeAgentStepTimeoutSeconds, MaxRuntimeAgentStepTimeoutSeconds))
 	}
+	if task.AgentMaxSessions < MinRuntimeAgentSessions || task.AgentMaxSessions > MaxRuntimeAgentSessions {
+		return kernel.BadAuthRequest(fmt.Sprintf("Agent 同时对话上限必须是 %d-%d 的整数", MinRuntimeAgentSessions, MaxRuntimeAgentSessions))
+	}
 	request := value.Request
 	for label, item := range map[string]int{
 		"任务创建频控": request.TaskCreatePerMinute,

backend/internal/service/aliases_types.go

@@ -27,6 +27,7 @@ type (
 	AdminAuditPage                         = app.AdminAuditPage
 	AdminCacheClearGroupResult             = app.AdminCacheClearGroupResult
 	AdminCacheClearRequest                 = app.AdminCacheClearRequest
+	AgentSessionLimitRequest               = app.AgentSessionLimitRequest
 	AdminCacheClearResult                  = app.AdminCacheClearResult
 	AdminChannelModelFetchResult           = app.AdminChannelModelFetchResult
 	AdminChannelModelImportRequest         = app.AdminChannelModelImportRequest