fix(agent): 修复流式推理与工具参数重试

backend/internal/app/cloud_agent_stream.go

@@ -0,0 +1,66 @@
+package app
+
+import (
+	"errors"
+	"unicode/utf8"
+
+	"gorm.io/gorm"
+	"infinite-canvas/backend/internal/model"
+	"infinite-canvas/backend/internal/repository"
+)
+
+// Publish upstream deltas to the same durable, revisioned transcript used by
+// Agent SSE/replay. Each flush re-reads state; never overwrite a scheduler's
+// checkpoint with the snapshot from when the model request started.
+func newCloudAgentStreamPublisher(s *Service, userID, taskID, kind string) *taskTextStreamPublisher {
+	p := newTaskTextStreamPublisher(s, userID, taskID)
+	written := 0
+	p.sink = func(delta string) error {
+		remaining := 32000 - written
+		if remaining <= 0 {
+			return nil
+		}
+		if len(delta) > remaining {
+			delta = delta[:remaining]
+			for !utf8.ValidString(delta) {
+				delta = delta[:len(delta)-1]
+			}
+		}
+		if delta == "" {
+			return nil
+		}
+		for attempt := 0; attempt < 3; attempt++ {
+			run, err := s.repo.CloudAgentForActiveTask(userID, taskID)
+			if errors.Is(err, gorm.ErrRecordNotFound) {
+				return nil
+			}
+			if err != nil {
+				return err
+			}
+			err = s.repo.MutateCloudAgent(userID, run.ID, run.Revision, func(current *model.CloudAgentExecution, _ *repository.Repository) error {
+				state, err := cloudAgentDecode(current)
+				if err != nil {
+					return err
+				}
+				if state.ActiveTaskID != taskID || (current.Status != "running" && current.Status != "queued") {
+					return nil
+				}
+				messageID := taskID
+				if kind == "reasoning_delta" {
+					messageID += ":reasoning"
+				}
+				state.event(run.ID, kind, map[string]any{"messageId": messageID, "text": delta})
+				return cloudAgentSave(current, &state)
+			})
+			if errors.Is(err, repository.ErrCreationConflict) {
+				continue
+			}
+			if err == nil {
+				written += len(delta)
+			}
+			return err
+		}
+		return repository.ErrCreationConflict
+	}
+	return p
+}