bugfix

internal/chat/service_message.go

@@ -26,18 +26,20 @@ type MessageServiceConfig struct {
 }
 
 type messageService struct {
-	repo      Repository
-	storage   storage.Storage
-	hub       StreamerHub
-	auditor   audit.Recorder
-	log       *slog.Logger
-	mimeWhite map[string]bool
-	maxFile   int64
-	maxMsg    int64
-	safetyPct float64
+	repo        Repository
+	storage     storage.Storage
+	hub         StreamerHub
+	auditor     audit.Recorder
+	log         *slog.Logger
+	mimeWhite   map[string]bool
+	maxFile     int64
+	maxMsg      int64
+	safetyPct   float64
+	briefReader ContextReader // 可为 nil；非 nil 时 composeHistory 注入 FK 上下文
 }
 
-// NewMessageService constructs a MessageService.
+// NewMessageService constructs a MessageService. briefReader 可为 nil：nil 时
+// composeHistory 完全保留旧行为（仅用 conv.SystemPrompt），不做 FK 上下文注入。
 func NewMessageService(
 	repo Repository,
 	st storage.Storage,
@@ -45,21 +47,23 @@ func NewMessageService(
 	auditor audit.Recorder,
 	log *slog.Logger,
 	cfg MessageServiceConfig,
+	briefReader ContextReader,
 ) MessageService {
 	mimeWhite := make(map[string]bool, len(cfg.MimeWhitelist))
 	for _, m := range cfg.MimeWhitelist {
 		mimeWhite[m] = true
 	}
 	return &messageService{
-		repo:      repo,
-		storage:   st,
-		hub:       hub,
-		auditor:   auditor,
-		log:       log,
-		mimeWhite: mimeWhite,
-		maxFile:   cfg.MaxFileBytes,
-		maxMsg:    cfg.MaxMsgBytes,
-		safetyPct: cfg.SafetyPct,
+		repo:        repo,
+		storage:     st,
+		hub:         hub,
+		auditor:     auditor,
+		log:         log,
+		mimeWhite:   mimeWhite,
+		maxFile:     cfg.MaxFileBytes,
+		maxMsg:      cfg.MaxMsgBytes,
+		safetyPct:   cfg.SafetyPct,
+		briefReader: briefReader,
 	}
 }
 
@@ -483,20 +487,52 @@ func (s *messageService) composeHistory(ctx context.Context, conv *Conversation,
 		}
 	}
 
+	// Resolve the effective system prompt by merging conv.SystemPrompt with the
+	// FK-derived context brief (requirement/issue/project mounts). The brief is
+	// pre-bounded by the composer, so it cannot starve message history to zero
+	// (truncateByTokens still reserves the remaining budget for messages).
+	effectiveSystemPrompt := s.effectiveSystemPrompt(ctx, conv)
+
 	// Compute token budget: context window minus max output tokens, then apply safety margin.
 	budget := model.ContextWindow - model.MaxOutputTokens
 	budget = int(float64(budget) * (1 - s.safetyPct))
 
-	msgs = truncateByTokens(msgs, conv.SystemPrompt, budget)
+	msgs = truncateByTokens(msgs, effectiveSystemPrompt, budget)
 
 	return llm.Request{
-		SystemPrompt:    conv.SystemPrompt,
+		SystemPrompt:    effectiveSystemPrompt,
 		Messages:        msgs,
 		MaxOutputTokens: model.MaxOutputTokens,
 		Reasoning:       model.Capabilities.Reasoning,
 	}, nil
 }
 
+// effectiveSystemPrompt 把会话静态 system prompt 与 FK 派生上下文简报合并。
+// briefReader 为 nil、会话无任何 FK 挂载、或简报为空时，直接返回 conv.SystemPrompt
+// （与旧行为完全一致）。合并是追加式的（FK 简报置于静态 prompt 之后），便于
+// 让旧会话（曾把角色 prompt 烘焙进 SystemPrompt）与新会话都能正常工作。
+func (s *messageService) effectiveSystemPrompt(ctx context.Context, conv *Conversation) string {
+	if s.briefReader == nil || !conv.HasFKMount() {
+		return conv.SystemPrompt
+	}
+	fkBrief, err := s.briefReader.BriefForConversation(ctx, conv)
+	if err != nil {
+		if s.log != nil {
+			s.log.Warn("chat.compose_history.brief_failed",
+				"conversation_id", conv.ID, "err", err.Error())
+		}
+		return conv.SystemPrompt
+	}
+	fkBrief = strings.TrimSpace(fkBrief)
+	if fkBrief == "" {
+		return conv.SystemPrompt
+	}
+	if strings.TrimSpace(conv.SystemPrompt) == "" {
+		return fkBrief
+	}
+	return conv.SystemPrompt + "\n\n" + fkBrief
+}
+
 // truncateByTokens walks messages backwards and drops oldest messages until the
 // estimated token count (system prompt + messages) fits within budget.
 func truncateByTokens(msgs []llm.Message, systemPrompt string, budget int) []llm.Message {