From da313f88ed1c09a717a99a11ccc52972245955be Mon Sep 17 00:00:00 2001
From: Nelson <1475262689@qq.com>
Date: Fri, 31 Jul 2026 17:25:16 +0800
Subject: [PATCH] feat: route background ai workloads by model

---
 .../apps/admin-web/src/App.vue                |  68 +++++++-
 .../apps/admin-web/src/services/api.ts        |   6 +-
 .../apps/admin-web/src/styles.css             |   3 +
 .../apps/admin-web/src/types/api.ts           |  11 ++
 .../alembic/versions/0022_model_routing.py    |  52 ++++++
 .../apps/backend/app/api/admin_settings.py    |  58 ++++++-
 .../apps/backend/app/models/ai_config.py      |   1 +
 .../apps/backend/app/schemas/admin.py         |  17 ++
 .../backend/app/services/admin_service.py     |  68 ++++++--
 .../app/services/ai_request_log_service.py    |   8 +-
 .../app/services/growth_profile_service.py    |  26 ++-
 .../app/services/knowledge_agent_service.py   |   8 +-
 .../app/services/model_routing_service.py     |  89 ++++++++++
 .../backend/app/services/model_service.py     |  44 ++++-
 .../app/services/model_stream_service.py      |   9 +-
 .../app/services/periodic_report_service.py   |  13 +-
 .../services/tracked_generation_service.py    |  64 ++++++++
 .../backend/tests/test_ai_cost_tracking.py    |  50 ++++++
 .../apps/backend/tests/test_model_routing.py  | 154 ++++++++++++++++++
 .../backend/tests/test_periodic_reports.py    |   8 +-
 .../deployment/DEPLOYMENT_GUIDE.md            |  19 +++
 .../docs/qianwen_product_todo.md              |   1 +
 22 files changed, 714 insertions(+), 63 deletions(-)
 create mode 100644 ai_knowledge_base_v2/apps/backend/alembic/versions/0022_model_routing.py
 create mode 100644 ai_knowledge_base_v2/apps/backend/app/services/model_routing_service.py
 create mode 100644 ai_knowledge_base_v2/apps/backend/app/services/tracked_generation_service.py
 create mode 100644 ai_knowledge_base_v2/apps/backend/tests/test_model_routing.py

diff --git a/ai_knowledge_base_v2/apps/admin-web/src/App.vue b/ai_knowledge_base_v2/apps/admin-web/src/App.vue
index 795fcc1..e39e234 100644
--- a/ai_knowledge_base_v2/apps/admin-web/src/App.vue
+++ b/ai_knowledge_base_v2/apps/admin-web/src/App.vue
@@ -305,7 +305,15 @@ async function loadDashboard() {
 
 async function refreshStorage() { storageLoading.value = true; try { storageStats.value = await api.storageStats(true); ElMessage.success("存储统计已刷新"); } finally { storageLoading.value = false; } }
 function formatBytes(value: unknown) { if (typeof value !== "number") return "无法统计"; const units = ["B", "KB", "MB", "GB", "TB"]; let size = value, i = 0; while (size >= 1024 && i < units.length - 1) { size /= 1024; i += 1; } return `${size.toFixed(i ? 2 : 0)} ${units[i]}`; }
-function formatMoney(value?: number | null, currency = "CNY") { if (typeof value !== "number") return "-"; return `${currency || "CNY"} ${value.toFixed(6)}`; }
+function formatMoney(value?: number | null, currency = "CNY") { if (typeof value !== "number") return "-"; if (currency === "MIXED") return "多币种，见明细"; return `${currency || "CNY"} ${value.toFixed(6)}`; }
+function modelSceneLabel(scene: string) {
+  return ({
+    background_report: "周期报告",
+    background_summary: "摘要沉淀",
+    knowledge_grounded: "知识问答",
+    general_chat: "通用对话",
+  } as Record<string, string>)[scene] || scene || "未分类";
+}
 async function cleanupRetrievalLogs() { if (!cleanupBefore.value) return ElMessage.warning("请选择清理日期"); const estimate = await api.estimateRetrievalCleanup(cleanupBefore.value); await ElMessageBox.confirm(`预计清理 ${estimate.estimatedCount} 条检索日志及关联明细，操作日志不会被删除。`, "确认清理", { type: "warning" }); const result = await api.cleanupRetrievalLogs(cleanupBefore.value); ElMessage.success(`已清理 ${result.deleted} 条日志`); await loadCurrentMenu(); }
 async function saveRetention() { await api.saveRetrievalRetention(retentionDays.value); ElMessage.success(retentionDays.value == null ? "已设为永久保留" : `已设为保留 ${retentionDays.value} 天`); await loadCurrentMenu(); }
 
@@ -711,12 +719,25 @@ function applyQuickProvider(provider: string) {
   quickModelForm.modelName = target.models[0]?.value ?? "";
 }
 
-async function enableModel(id: number) {
-  await api.enableModel(id);
-  ElMessage.success("模型已启用");
+async function setModelAvailability(row: ModelItem, enabled: number) {
+  await api.setModelAvailability(row.id, enabled);
+  ElMessage.success(enabled === 1 ? "模型已加入可用池" : "模型已停用");
   await loadCurrentMenu();
 }
 
+async function setDefaultModel(row: ModelItem) {
+  await api.setDefaultModel(row.id);
+  ElMessage.success("默认主模型已更新");
+  await loadCurrentMenu();
+}
+
+async function handleModelCommand(command: string, row: ModelItem) {
+  if (command === "enable") return setModelAvailability(row, 1);
+  if (command === "disable") return setModelAvailability(row, 0);
+  if (command === "default") return setDefaultModel(row);
+  return deleteModel(row.id);
+}
+
 async function deleteModel(id: number) {
   try {
     await ElMessageBox.confirm("确认删除该模型？删除后不可恢复。", "删除模型", {
@@ -1108,6 +1129,23 @@ function formatRecordDateTime(value: string, boundary: "start" | "end") {
             <div class="stat"><span>总 Token</span><strong>{{ stats?.totalToken ?? 0 }}</strong></div>
             <div class="stat"><span>估算成本</span><strong>{{ formatMoney(stats?.estimatedCost, stats?.costCurrency || 'CNY') }}</strong></div>
           </div>
+          <section class="cost-breakdown-panel">
+            <div class="storage-panel-head">
+              <div><h3>模型使用与成本</h3><p>按实际调用场景和模型统计；报告、摘要分流是否生效可在这里核对。</p></div>
+            </div>
+            <el-table :data="stats?.costBreakdown || []" empty-text="当前日期范围内暂无模型调用">
+              <el-table-column label="调用场景" min-width="130">
+                <template #default="{ row }">{{ modelSceneLabel(row.scene) }}</template>
+              </el-table-column>
+              <el-table-column prop="modelName" label="实际模型" min-width="180" show-overflow-tooltip />
+              <el-table-column prop="requestCount" label="请求数" width="100" />
+              <el-table-column prop="inputToken" label="输入 Token" width="130" />
+              <el-table-column prop="outputToken" label="输出 Token" width="130" />
+              <el-table-column label="估算成本" width="170">
+                <template #default="{ row }">{{ formatMoney(row.estimatedCost, row.currency || 'CNY') }}</template>
+              </el-table-column>
+            </el-table>
+          </section>
           <section class="storage-panel" v-loading="storageLoading"><div class="storage-panel-head"><div><h3>项目存储占用</h3><p>数据库、Redis 与附件分别统计；无权限或不支持时显示“无法统计”。</p></div><el-button :loading="storageLoading" @click="refreshStorage">手动刷新</el-button></div><div class="storage-grid"><div><span>项目总量</span><strong>{{ formatBytes(storageStats?.totalBytes) }}</strong></div><div><span>数据库</span><strong>{{ formatBytes(storageStats?.detail?.database?.bytes) }}</strong></div><div><span>Redis</span><strong>{{ formatBytes(storageStats?.detail?.redis?.bytes) }}</strong></div><div><span>附件/文件</span><strong>{{ formatBytes(storageStats?.detail?.files?.bytes) }}</strong></div><div><span>近7天增长</span><strong>{{ formatBytes(storageStats?.growth7DaysBytes) }}</strong></div><div><span>近30天增长</span><strong>{{ formatBytes(storageStats?.growth30DaysBytes) }}</strong></div></div><small>最后统计：{{ storageStats?.createdAt || '尚未统计' }}</small></section>
         </template>
 
@@ -1322,7 +1360,7 @@ function formatRecordDateTime(value: string, boundary: "start" | "end") {
 
         <template v-if="activeMenu === 'models'">
           <div class="page-head inline">
-            <div><h2>模型管理</h2><p>DeepSeek、MiniMax 可快速添加；其他供应商按 OpenAI 兼容或 Anthropic Messages 协议添加。</p></div>
+            <div><h2>模型管理</h2><p>可同时启用多个模型，但只保留一个默认主模型；正式聊天始终使用主模型，报告和摘要按能力标签分流并自动回退主模型。</p></div>
             <el-button @click="resetModelForm">清空表单</el-button>
           </div>
 
@@ -1444,13 +1482,27 @@ function formatRecordDateTime(value: string, boundary: "start" | "end") {
             <el-table-column label="估算单价" width="180">
               <template #default="{ row }">{{ row.currency || 'CNY' }} {{ row.inputPricePer1k ?? '-' }}/{{ row.outputPricePer1k ?? '-' }}</template>
             </el-table-column>
-            <el-table-column prop="usageScenarios" label="适用场景" min-width="160" show-overflow-tooltip />
+            <el-table-column label="分流能力" min-width="220">
+              <template #default="{ row }">
+                <div class="model-capability-tags">
+                  <el-tag v-if="row.allowDeepChat === 1" size="small">深度对话</el-tag>
+                  <el-tag v-if="row.allowFixedInfo === 1" size="small">固定信息</el-tag>
+                  <el-tag v-if="row.allowSummary === 1" size="small" type="success">摘要</el-tag>
+                  <el-tag v-if="row.allowReport === 1" size="small" type="warning">报告</el-tag>
+                </div>
+              </template>
+            </el-table-column>
             <el-table-column prop="baseUrl" label="Base URL" min-width="220" show-overflow-tooltip />
             <el-table-column prop="authType" label="鉴权" width="110" />
-            <el-table-column prop="enabled" label="启用" width="90" />
+            <el-table-column label="运行状态" width="150">
+              <template #default="{ row }">
+                <el-tag :type="row.enabled === 1 ? 'success' : 'info'">{{ row.enabled === 1 ? '可用' : '停用' }}</el-tag>
+                <el-tag v-if="row.isDefault === 1" class="model-default-tag">主模型</el-tag>
+              </template>
+            </el-table-column>
             <el-table-column label="操作" width="190" fixed="right" align="center">
               <template #default="{ row }">
-                <TableRowActions><el-button size="small" @click="editModel(row)">编辑</el-button><el-button size="small" @click="testModel(row.id)">测试</el-button><el-dropdown trigger="click" teleported @command="(command: string) => command === 'enable' ? enableModel(row.id) : deleteModel(row.id)"><el-button size="small">更多</el-button><template #dropdown><el-dropdown-menu><el-dropdown-item command="enable">启用</el-dropdown-item><el-dropdown-item command="delete" divided>删除</el-dropdown-item></el-dropdown-menu></template></el-dropdown></TableRowActions>
+                <TableRowActions><el-button size="small" @click="editModel(row)">编辑</el-button><el-button size="small" @click="testModel(row.id)">测试</el-button><el-dropdown trigger="click" teleported @command="(command: string) => handleModelCommand(command, row)"><el-button size="small">更多</el-button><template #dropdown><el-dropdown-menu><el-dropdown-item v-if="row.enabled !== 1" command="enable">加入可用池</el-dropdown-item><el-dropdown-item v-if="row.enabled === 1 && row.isDefault !== 1" command="default">设为主模型</el-dropdown-item><el-dropdown-item v-if="row.enabled === 1 && row.isDefault !== 1" command="disable">停用</el-dropdown-item><el-dropdown-item v-if="row.isDefault !== 1" command="delete" divided>删除</el-dropdown-item></el-dropdown-menu></template></el-dropdown></TableRowActions>
               </template>
             </el-table-column>
           </el-table>
diff --git a/ai_knowledge_base_v2/apps/admin-web/src/services/api.ts b/ai_knowledge_base_v2/apps/admin-web/src/services/api.ts
index a8c6f10..e5883a7 100644
--- a/ai_knowledge_base_v2/apps/admin-web/src/services/api.ts
+++ b/ai_knowledge_base_v2/apps/admin-web/src/services/api.ts
@@ -207,8 +207,10 @@ export const api = {
     request<ModelItem>("/admin/model", { method: "POST", body: JSON.stringify(payload) }),
   updateModel: (id: number, payload: Record<string, unknown>) =>
     request<ModelItem>(`/admin/model/${id}`, { method: "PUT", body: JSON.stringify(payload) }),
-  enableModel: (modelId: number) =>
-    request<null>("/admin/model/enable", { method: "POST", body: JSON.stringify({ modelId }) }),
+  setModelAvailability: (modelId: number, enabled: number) =>
+    request<null>("/admin/model/enable", { method: "POST", body: JSON.stringify({ modelId, enabled }) }),
+  setDefaultModel: (modelId: number) =>
+    request<null>("/admin/model/default", { method: "POST", body: JSON.stringify({ modelId }) }),
   deleteModel: (modelId: number) =>
     request<null>(`/admin/model/${modelId}`, { method: "DELETE" }),
   testModel: (modelId: number) =>
diff --git a/ai_knowledge_base_v2/apps/admin-web/src/styles.css b/ai_knowledge_base_v2/apps/admin-web/src/styles.css
index 99c1c2f..fbc5744 100644
--- a/ai_knowledge_base_v2/apps/admin-web/src/styles.css
+++ b/ai_knowledge_base_v2/apps/admin-web/src/styles.css
@@ -525,12 +525,15 @@ textarea {
   gap: 14px;
 }
 .storage-panel { margin-top: 18px; padding: 18px; border: 1px solid #dfe8e5; border-radius: 8px; background: #fff; }
+.cost-breakdown-panel { margin-top: 18px; padding: 18px; border: 1px solid #dfe8e5; border-radius: 8px; background: #fff; }
 .storage-panel-head { display: flex; justify-content: space-between; align-items: start; gap: 16px; }
 .storage-panel-head h3, .storage-panel-head p { margin: 0 0 6px; }
 .storage-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; margin: 14px 0; }
 .storage-grid > div { padding: 14px; background: #f6f8f7; border-radius: 8px; }
 .storage-grid span, .storage-grid strong { display: block; }
 .storage-grid strong { margin-top: 8px; font-size: 20px; }
+.model-capability-tags { display: flex; flex-wrap: wrap; gap: 6px; }
+.model-default-tag { margin-left: 6px; }
 .cleanup-controls { display: flex; align-items: center; gap: 8px; white-space: nowrap; }
 .retention-panel { display: grid; grid-template-columns: minmax(260px, 1fr) 180px auto auto; align-items: center; gap: 12px; padding: 14px 16px; margin-bottom: 14px; border: 1px solid #dfe8e5; border-radius: 8px; background: #fff; }
 .retention-panel div span { display: block; margin-top: 4px; color: #667a73; font-size: 12px; }
diff --git a/ai_knowledge_base_v2/apps/admin-web/src/types/api.ts b/ai_knowledge_base_v2/apps/admin-web/src/types/api.ts
index 2e84e29..92b48fb 100644
--- a/ai_knowledge_base_v2/apps/admin-web/src/types/api.ts
+++ b/ai_knowledge_base_v2/apps/admin-web/src/types/api.ts
@@ -29,6 +29,16 @@ export interface DashboardStats {
   totalToken: number;
   estimatedCost?: number | null;
   costCurrency?: string | null;
+  costBreakdown: Array<{
+    scene: string;
+    modelName: string;
+    requestCount: number;
+    inputToken: number;
+    outputToken: number;
+    totalToken: number;
+    estimatedCost: number;
+    currency?: string | null;
+  }>;
 }
 
 export interface PromptDetail {
@@ -195,6 +205,7 @@ export interface ModelItem {
   remark?: string | null;
   timeoutSecond: number;
   enabled: number;
+  isDefault: number;
   inputPricePer1k?: number | null;
   outputPricePer1k?: number | null;
   currency: string;
diff --git a/ai_knowledge_base_v2/apps/backend/alembic/versions/0022_model_routing.py b/ai_knowledge_base_v2/apps/backend/alembic/versions/0022_model_routing.py
new file mode 100644
index 0000000..3c3d034
--- /dev/null
+++ b/ai_knowledge_base_v2/apps/backend/alembic/versions/0022_model_routing.py
@@ -0,0 +1,52 @@
+"""add multi-model routing support
+
+Revision ID: 0022_model_routing
+Revises: 0021_periodic_report_async_jobs
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "0022_model_routing"
+down_revision = "0021_periodic_report_async_jobs"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "sys_model",
+        sa.Column("is_default", sa.Integer(), nullable=False, server_default="0"),
+    )
+    op.create_index(
+        "ix_sys_model_available_default",
+        "sys_model",
+        ["enabled", "is_default", "id"],
+        unique=False,
+    )
+    # 兼容旧数据：原来唯一启用的模型直接成为默认主模型。
+    op.execute(
+        """
+        UPDATE sys_model
+        SET is_default = 1
+        WHERE enabled = 1
+          AND id = (
+              SELECT selected.id
+              FROM (
+                  SELECT id
+                  FROM sys_model
+                  WHERE enabled = 1
+                  ORDER BY id DESC
+                  LIMIT 1
+              ) AS selected
+          )
+        """
+    )
+
+
+def downgrade() -> None:
+    # 回滚到旧语义前只保留默认模型为启用，避免旧代码随机选到分流模型。
+    op.execute("UPDATE sys_model SET enabled = CASE WHEN is_default = 1 THEN 1 ELSE 0 END")
+    op.drop_index("ix_sys_model_available_default", table_name="sys_model")
+    op.drop_column("sys_model", "is_default")
diff --git a/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py b/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py
index a84c62f..558fe40 100644
--- a/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py
+++ b/ai_knowledge_base_v2/apps/backend/app/api/admin_settings.py
@@ -19,6 +19,7 @@ from app.models.knowledge import Knowledge
 from app.schemas.admin import (
     AgentDebugRequest,
     AgentRuntimeConfigSaveRequest,
+    DefaultModelRequest,
     EnableModelRequest,
     ModelSaveRequest,
     PromptSaveRequest,
@@ -246,7 +247,13 @@ def save_agent_runtime_config(
 
 @router.get("/model/list")
 def list_models(db: Session = Depends(get_db), current_admin: Admin = Depends(get_current_admin)) -> dict:
-    models = db.scalars(select(ModelConfig).order_by(ModelConfig.id.desc())).all()
+    models = db.scalars(
+        select(ModelConfig).order_by(
+            ModelConfig.is_default.desc(),
+            ModelConfig.enabled.desc(),
+            ModelConfig.id.desc(),
+        )
+    ).all()
     return api_success([_model_dict(model) for model in models])
 
 
@@ -289,6 +296,7 @@ def create_model(
         allow_fixed_info=payload.allowFixedInfo,
         allow_deep_chat=payload.allowDeepChat,
         enabled=0,
+        is_default=0,
     )
     db.add(model)
     db.flush()
@@ -351,14 +359,46 @@ def enable_model(
     payload: EnableModelRequest,
     db: Session = Depends(get_db),
     current_admin: Admin = Depends(get_current_admin),
+) -> dict:
+    target = db.get(ModelConfig, payload.modelId)
+    if target is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="模型不存在")
+    if payload.enabled == 0 and target.is_default == 1:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="默认主模型不能直接停用，请先设置另一个默认主模型",
+        )
+    target.enabled = payload.enabled
+    if payload.enabled == 1 and _explicit_default_model(db) is None:
+        target.is_default = 1
+    db.add(target)
+    action = "enable" if payload.enabled == 1 else "disable"
+    OperationLogService.write(db, admin_id=current_admin.id, module="model", action=action, target_id=target.id)
+    db.commit()
+    return api_success()
+
+
+@router.post("/model/default")
+def set_default_model(
+    payload: DefaultModelRequest,
+    db: Session = Depends(get_db),
+    current_admin: Admin = Depends(get_current_admin),
 ) -> dict:
     target = db.get(ModelConfig, payload.modelId)
     if target is None:
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="模型不存在")
     for model in db.scalars(select(ModelConfig)).all():
-        model.enabled = 1 if model.id == target.id else 0
+        model.is_default = 1 if model.id == target.id else 0
+        if model.id == target.id:
+            model.enabled = 1
         db.add(model)
-    OperationLogService.write(db, admin_id=current_admin.id, module="model", action="enable", target_id=target.id)
+    OperationLogService.write(
+        db,
+        admin_id=current_admin.id,
+        module="model",
+        action="set_default",
+        target_id=target.id,
+    )
     db.commit()
     return api_success()
 
@@ -372,6 +412,11 @@ def delete_model(
     model = db.get(ModelConfig, model_id)
     if model is None:
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="模型不存在")
+    if model.is_default == 1:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="不能删除默认主模型，请先设置另一个默认主模型",
+        )
     db.delete(model)
     OperationLogService.write(db, admin_id=current_admin.id, module="model", action="delete", target_id=model.id)
     db.commit()
@@ -449,6 +494,7 @@ def _model_dict(model: ModelConfig) -> dict:
         "remark": model.remark,
         "timeoutSecond": model.timeout_second,
         "enabled": model.enabled,
+        "isDefault": model.is_default,
         "inputPricePer1k": float(model.input_price_per_1k) if model.input_price_per_1k is not None else None,
         "outputPricePer1k": float(model.output_price_per_1k) if model.output_price_per_1k is not None else None,
         "currency": model.currency,
@@ -461,9 +507,13 @@ def _model_dict(model: ModelConfig) -> dict:
 
 
 def _enabled_model(db: Session) -> ModelConfig | None:
+    return ModelClientService._get_enabled_model(db)
+
+
+def _explicit_default_model(db: Session) -> ModelConfig | None:
     return db.scalar(
         select(ModelConfig)
-        .where(ModelConfig.enabled == 1)
+        .where(ModelConfig.enabled == 1, ModelConfig.is_default == 1)
         .order_by(ModelConfig.id.desc())
         .limit(1)
     )
diff --git a/ai_knowledge_base_v2/apps/backend/app/models/ai_config.py b/ai_knowledge_base_v2/apps/backend/app/models/ai_config.py
index 95ab416..66479e7 100644
--- a/ai_knowledge_base_v2/apps/backend/app/models/ai_config.py
+++ b/ai_knowledge_base_v2/apps/backend/app/models/ai_config.py
@@ -49,6 +49,7 @@ class ModelConfig(Base):
     remark: Mapped[str | None] = mapped_column(String(255), nullable=True)
     timeout_second: Mapped[int] = mapped_column(Integer, default=30, nullable=False)
     enabled: Mapped[int] = mapped_column(default=0, nullable=False)
+    is_default: Mapped[int] = mapped_column(default=0, nullable=False)
     input_price_per_1k: Mapped[Decimal | None] = mapped_column(Numeric(12, 6), nullable=True)
     output_price_per_1k: Mapped[Decimal | None] = mapped_column(Numeric(12, 6), nullable=True)
     currency: Mapped[str] = mapped_column(String(10), default="CNY", nullable=False)
diff --git a/ai_knowledge_base_v2/apps/backend/app/schemas/admin.py b/ai_knowledge_base_v2/apps/backend/app/schemas/admin.py
index 70001b9..76b9863 100644
--- a/ai_knowledge_base_v2/apps/backend/app/schemas/admin.py
+++ b/ai_knowledge_base_v2/apps/backend/app/schemas/admin.py
@@ -26,6 +26,17 @@ class AdminRead(ORMModel):
     status: int
 
 
+class CostBreakdownItem(BaseModel):
+    scene: str
+    modelName: str
+    requestCount: int
+    inputToken: int
+    outputToken: int
+    totalToken: int
+    estimatedCost: float
+    currency: str | None = None
+
+
 class DashboardStats(BaseModel):
     userCount: int
     sessionCount: int
@@ -37,6 +48,7 @@ class DashboardStats(BaseModel):
     totalToken: int
     estimatedCost: float | None = None
     costCurrency: str | None = None
+    costBreakdown: list[CostBreakdownItem] = Field(default_factory=list)
 
 
 class AdminUserUpdateRequest(BaseModel):
@@ -175,6 +187,11 @@ class ModelSaveRequest(BaseModel):
 
 class EnableModelRequest(BaseModel):
     modelId: int
+    enabled: int = Field(default=1, ge=0, le=1)
+
+
+class DefaultModelRequest(BaseModel):
+    modelId: int
 
 
 class SystemConfigSaveRequest(BaseModel):
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/admin_service.py b/ai_knowledge_base_v2/apps/backend/app/services/admin_service.py
index 4c1e667..dca30a5 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/admin_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/admin_service.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 from datetime import UTC, datetime
 
 from fastapi import HTTPException, status
-from sqlalchemy import func, select
+from sqlalchemy import func, select, true
 from sqlalchemy.orm import Session
 
 from app.core.config import get_settings
@@ -133,23 +133,71 @@ class AdminDashboardService:
             msg_filter.append(ChatMessage.created_at <= end)
             ai_filter.append(AiRequestLog.created_at <= end)
 
+        user_where = and_(true(), *user_filter)
+        session_where = and_(true(), *session_filter)
+        message_where = and_(true(), *msg_filter)
+        ai_where = and_(true(), *ai_filter)
         cost_currency = db.scalar(
             select(AiRequestLog.currency)
-            .where(and_(*ai_filter), AiRequestLog.currency.is_not(None))
+            .where(ai_where, AiRequestLog.currency.is_not(None))
             .order_by(AiRequestLog.id.desc())
             .limit(1)
         )
+        cost_breakdown = [
+            {
+                "scene": question_type or "unknown",
+                "modelName": model_name or "未知模型",
+                "requestCount": int(request_count or 0),
+                "inputToken": int(input_token or 0),
+                "outputToken": int(output_token or 0),
+                "totalToken": int(total_token or 0),
+                "estimatedCost": float(estimated_cost or 0),
+                "currency": currency,
+            }
+            for (
+                question_type,
+                model_name,
+                currency,
+                request_count,
+                input_token,
+                output_token,
+                total_token,
+                estimated_cost,
+            ) in db.execute(
+                select(
+                    AiRequestLog.question_type,
+                    AiRequestLog.model_name,
+                    AiRequestLog.currency,
+                    func.count(AiRequestLog.id),
+                    func.coalesce(func.sum(AiRequestLog.input_token), 0),
+                    func.coalesce(func.sum(AiRequestLog.output_token), 0),
+                    func.coalesce(func.sum(AiRequestLog.total_token), 0),
+                    func.coalesce(func.sum(AiRequestLog.estimated_cost), 0),
+                )
+                .where(ai_where)
+                .group_by(
+                    AiRequestLog.question_type,
+                    AiRequestLog.model_name,
+                    AiRequestLog.currency,
+                )
+                .order_by(func.count(AiRequestLog.id).desc())
+            ).all()
+        ]
+        currencies = {item["currency"] for item in cost_breakdown if item["currency"]}
+        if len(currencies) > 1:
+            cost_currency = "MIXED"
         return {
-            "userCount": db.scalar(select(func.count(User.id)).where(and_(*user_filter))) or 0,
-            "sessionCount": db.scalar(select(func.count(ChatSession.id)).where(and_(*session_filter))) or 0,
-            "messageCount": db.scalar(select(func.count(ChatMessage.id)).where(and_(*msg_filter))) or 0,
-            "aiRequestCount": db.scalar(select(func.count(AiRequestLog.id)).where(and_(*ai_filter))) or 0,
+            "userCount": db.scalar(select(func.count(User.id)).where(user_where)) or 0,
+            "sessionCount": db.scalar(select(func.count(ChatSession.id)).where(session_where)) or 0,
+            "messageCount": db.scalar(select(func.count(ChatMessage.id)).where(message_where)) or 0,
+            "aiRequestCount": db.scalar(select(func.count(AiRequestLog.id)).where(ai_where)) or 0,
             "knowledgeCount": db.scalar(select(func.count(Knowledge.id))) or 0,
-            "inputToken": db.scalar(select(func.coalesce(func.sum(AiRequestLog.input_token), 0)).where(and_(*ai_filter))) or 0,
-            "outputToken": db.scalar(select(func.coalesce(func.sum(AiRequestLog.output_token), 0)).where(and_(*ai_filter))) or 0,
-            "totalToken": db.scalar(select(func.coalesce(func.sum(AiRequestLog.total_token), 0)).where(and_(*ai_filter))) or 0,
-            "estimatedCost": float(db.scalar(select(func.coalesce(func.sum(AiRequestLog.estimated_cost), 0)).where(and_(*ai_filter))) or 0),
+            "inputToken": db.scalar(select(func.coalesce(func.sum(AiRequestLog.input_token), 0)).where(ai_where)) or 0,
+            "outputToken": db.scalar(select(func.coalesce(func.sum(AiRequestLog.output_token), 0)).where(ai_where)) or 0,
+            "totalToken": db.scalar(select(func.coalesce(func.sum(AiRequestLog.total_token), 0)).where(ai_where)) or 0,
+            "estimatedCost": float(db.scalar(select(func.coalesce(func.sum(AiRequestLog.estimated_cost), 0)).where(ai_where)) or 0),
             "costCurrency": cost_currency,
+            "costBreakdown": cost_breakdown,
         }
 
 
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/ai_request_log_service.py b/ai_knowledge_base_v2/apps/backend/app/services/ai_request_log_service.py
index 8d0731f..96b1574 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/ai_request_log_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/ai_request_log_service.py
@@ -16,9 +16,9 @@ class AiRequestLogService:
     def write_success(
         db: Session,
         *,
-        session_id: int,
+        session_id: int | None,
         message_id: int | None,
-        user_id: int,
+        user_id: int | None,
         model_name: str,
         prompt: str,
         knowledge_ids: str,
@@ -61,9 +61,9 @@ class AiRequestLogService:
     def write_failed(
         db: Session,
         *,
-        session_id: int,
+        session_id: int | None,
         message_id: int | None,
-        user_id: int,
+        user_id: int | None,
         model_name: str | None,
         prompt: str | None,
         knowledge_ids: str | None,
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/growth_profile_service.py b/ai_knowledge_base_v2/apps/backend/app/services/growth_profile_service.py
index d6296a2..818b401 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/growth_profile_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/growth_profile_service.py
@@ -14,7 +14,7 @@ from app.models.growth import GrowthProfileRevision, TopicSummary, UserGrowthPro
 from app.models.user import User
 from app.services.entitlement_service import EntitlementService
 from app.services.external_errors import ExternalServiceError
-from app.services.model_service import ModelClientService
+from app.services.tracked_generation_service import TrackedGenerationService
 from app.services.topic_session_service import TopicSessionService
 
 
@@ -62,9 +62,16 @@ class GrowthProfileService:
             raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="当前主题还没有可沉淀的对话内容")
         conversation = _messages_text(messages)
         prompt = _topic_summary_prompt(topic, conversation)
-        model_name = _enabled_model_name(db)
+        model_name = None
         try:
-            raw = ModelClientService.generate_text_or_raise(db, prompt)
+            completion = TrackedGenerationService.generate(
+                db,
+                prompt=prompt,
+                scenario="summary",
+                user_id=user.id,
+            )
+            raw = completion.answer
+            model_name = completion.model_name
             parsed = _parse_summary_json(raw)
             data = parsed if parsed and "summary" in parsed else _fallback_summary(topic, conversation, raw)
             status_value = "success"
@@ -96,7 +103,13 @@ class GrowthProfileService:
 
         prompt = _growth_profile_prompt(profile, topic_summary)
         try:
-            raw = ModelClientService.generate_text_or_raise(db, prompt)
+            completion = TrackedGenerationService.generate(
+                db,
+                prompt=prompt,
+                scenario="summary",
+                user_id=user.id,
+            )
+            raw = completion.answer
             parsed = _parse_summary_json(raw)
             data = parsed if parsed and "profileText" in parsed else _fallback_profile(profile, topic_summary, raw)
         except ExternalServiceError:
@@ -326,10 +339,5 @@ def _limit(text: str, max_len: int) -> str:
     return text[:max_len].strip()
 
 
-def _enabled_model_name(db: Session) -> str | None:
-    model = ModelClientService._get_enabled_model(db)
-    return model.model_name if model is not None else None
-
-
 def _now() -> datetime:
     return datetime.now(UTC).replace(tzinfo=None)
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/knowledge_agent_service.py b/ai_knowledge_base_v2/apps/backend/app/services/knowledge_agent_service.py
index 7c0a55b..9fe9e02 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/knowledge_agent_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/knowledge_agent_service.py
@@ -12,7 +12,6 @@ from sqlalchemy import or_, select
 from sqlalchemy.orm import Session
 
 from app.core.config import get_settings
-from app.models.ai_config import ModelConfig
 from app.services.chat_context_service import ChatContextService
 from app.models.knowledge import (
     Knowledge,
@@ -33,6 +32,7 @@ from app.services.knowledge_pipeline_service import (
 from app.services.knowledge_catalog_cache_service import KnowledgeCatalogCacheService
 from app.services.knowledge_service import KnowledgeScope
 from app.services.model_service import _call_configured_model, _system_config_bool
+from app.services.model_routing_service import ModelRoutingService
 from app.services.rag_service import PromptService, RagResult, RetrievedChunk
 
 SAFETY_RULE_VERSION = "minimum-safety-v1"
@@ -264,9 +264,7 @@ class KnowledgeAgentService:
             "recentHistory": history_text,
         }
         fallback = cls._fallback_rewrite(question, recent)
-        model = db.scalar(
-            select(ModelConfig).where(ModelConfig.enabled == 1).order_by(ModelConfig.id.desc()).limit(1)
-        )
+        model = ModelRoutingService.default_model(db)
         if model is None or _system_config_bool(db, "mock_model_enabled", get_settings().mock_model_enabled):
             return fallback, cls._trace(
                 "rewrite_contextual_question",
@@ -444,7 +442,7 @@ class KnowledgeAgentService:
     async def _rerank(cls, db: Session, question: str, candidates: list[Candidate], trace: list[dict], started: float) -> None:
         if not candidates:
             return
-        model = db.scalar(select(ModelConfig).where(ModelConfig.enabled == 1).order_by(ModelConfig.id.desc()).limit(1))
+        model = ModelRoutingService.default_model(db)
         if model is None or _system_config_bool(db, "mock_model_enabled", get_settings().mock_model_enabled):
             trace.append(cls._trace("Rerank", len(trace) + 1, {"candidateCount": len(candidates)}, {"count": len(candidates), "mode": "lexical_fallback", "candidates": [cls._candidate_trace(x) for x in candidates]}, started))
             return
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/model_routing_service.py b/ai_knowledge_base_v2/apps/backend/app/services/model_routing_service.py
new file mode 100644
index 0000000..b0d5e9e
--- /dev/null
+++ b/ai_knowledge_base_v2/apps/backend/app/services/model_routing_service.py
@@ -0,0 +1,89 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Literal
+
+from sqlalchemy import desc, select
+from sqlalchemy.orm import Session
+
+from app.models.ai_config import ModelConfig
+
+ModelScenario = Literal["report", "summary", "fixed_info", "deep_chat"]
+
+SCENARIO_LABELS: dict[ModelScenario, str] = {
+    "report": "周期报告",
+    "summary": "摘要沉淀",
+    "fixed_info": "固定信息",
+    "deep_chat": "深度对话",
+}
+
+_SCENARIO_FIELDS = {
+    "report": ModelConfig.allow_report,
+    "summary": ModelConfig.allow_summary,
+    "fixed_info": ModelConfig.allow_fixed_info,
+    "deep_chat": ModelConfig.allow_deep_chat,
+}
+
+
+@dataclass(frozen=True)
+class ModelRoute:
+    model: ModelConfig | None
+    scenario: ModelScenario
+    reason: str
+    fallback_used: bool
+
+
+class ModelRoutingService:
+    """Centralizes deterministic model selection without changing live-chat routing."""
+
+    @staticmethod
+    def default_model(db: Session) -> ModelConfig | None:
+        model = db.scalar(
+            select(ModelConfig)
+            .where(ModelConfig.enabled == 1, ModelConfig.is_default == 1)
+            .order_by(ModelConfig.id.desc())
+            .limit(1)
+        )
+        if model is not None:
+            return model
+        # Migration/partial rollout safety: old databases may have an available
+        # model before one has been explicitly marked as default.
+        return db.scalar(
+            select(ModelConfig)
+            .where(ModelConfig.enabled == 1)
+            .order_by(ModelConfig.id.desc())
+            .limit(1)
+        )
+
+    @classmethod
+    def resolve(cls, db: Session, scenario: ModelScenario) -> ModelRoute:
+        default = cls.default_model(db)
+        capability = _SCENARIO_FIELDS[scenario]
+        candidate = db.scalar(
+            select(ModelConfig)
+            .where(ModelConfig.enabled == 1, capability == 1)
+            .order_by(desc(ModelConfig.is_default), ModelConfig.id.desc())
+            .limit(1)
+        )
+        label = SCENARIO_LABELS[scenario]
+        if candidate is not None:
+            source = "默认主模型" if candidate.is_default == 1 else "场景可用模型"
+            return ModelRoute(
+                model=candidate,
+                scenario=scenario,
+                reason=f"场景分流：{label}；选择{source}",
+                fallback_used=False,
+            )
+        if default is not None:
+            return ModelRoute(
+                model=default,
+                scenario=scenario,
+                reason=f"场景分流：{label}无匹配模型；回退默认主模型",
+                fallback_used=True,
+            )
+        return ModelRoute(
+            model=None,
+            scenario=scenario,
+            reason=f"场景分流：{label}无可用模型",
+            fallback_used=True,
+        )
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/model_service.py b/ai_knowledge_base_v2/apps/backend/app/services/model_service.py
index 5658dbd..f30dc2c 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/model_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/model_service.py
@@ -13,6 +13,7 @@ from sqlalchemy.orm import Session
 from app.core.config import get_settings
 from app.models.ai_config import ModelConfig, SystemConfig
 from app.services.external_errors import ExternalServiceError
+from app.services.model_routing_service import ModelRoutingService, ModelScenario
 from app.services.rag_service import NO_HIT_ANSWER, RagResult
 from app.services.secret_service import SecretService
 
@@ -24,6 +25,7 @@ class ModelCompletion:
     model_name: str
     input_token: int
     output_token: int
+    route_reason: str | None = None
 
 
 class ModelClientService:
@@ -83,6 +85,41 @@ class ModelClientService:
         rag_result = RagResult(question=prompt, knowledge_scopes=[], chunks=[], prompt=prompt, allow_general_knowledge=True)
         return _call_configured_model(model, rag_result, allow_no_hit=True)
 
+    @staticmethod
+    def generate_text_for_scenario(
+        db: Session,
+        prompt: str,
+        scenario: ModelScenario,
+    ) -> ModelCompletion:
+        route = ModelRoutingService.resolve(db, scenario)
+        model = route.model
+        if _system_config_bool(db, "mock_model_enabled", get_settings().mock_model_enabled):
+            answer = prompt.strip()[-1200:]
+            model_name = model.model_name if model is not None else "mock-model"
+        else:
+            if model is None:
+                raise ExternalServiceError(
+                    f"未启用可用于{scenario}场景的模型",
+                    provider="model",
+                )
+            rag_result = RagResult(
+                question=prompt,
+                knowledge_scopes=[],
+                chunks=[],
+                prompt=prompt,
+                allow_general_knowledge=True,
+            )
+            answer = _call_configured_model(model, rag_result, allow_no_hit=True)
+            model_name = model.model_name
+        return ModelCompletion(
+            answer=answer,
+            model_id=model.id if model is not None else None,
+            model_name=model_name,
+            input_token=_rough_token_count(prompt),
+            output_token=_rough_token_count(answer),
+            route_reason=route.reason,
+        )
+
     @staticmethod
     async def summarize_or_raise_async(
         db: Session,
@@ -99,12 +136,7 @@ class ModelClientService:
 
     @staticmethod
     def _get_enabled_model(db: Session) -> ModelConfig | None:
-        return db.scalar(
-            select(ModelConfig)
-            .where(ModelConfig.enabled == 1)
-            .order_by(ModelConfig.id.desc())
-            .limit(1)
-        )
+        return ModelRoutingService.default_model(db)
 
     @staticmethod
     def test_model(model: ModelConfig) -> dict[str, Any]:
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/model_stream_service.py b/ai_knowledge_base_v2/apps/backend/app/services/model_stream_service.py
index 4f3c18d..f9f9e3e 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/model_stream_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/model_stream_service.py
@@ -7,7 +7,6 @@ from dataclasses import dataclass
 from typing import Any
 
 import httpx
-from sqlalchemy import select
 from sqlalchemy.orm import Session
 
 from app.core.config import get_settings
@@ -30,6 +29,7 @@ from app.services.model_service import (
     _system_and_turn_messages,
     _system_config_bool,
 )
+from app.services.model_routing_service import ModelRoutingService
 from app.services.rag_service import RagResult
 
 
@@ -120,12 +120,7 @@ class ModelStreamService:
 
 
 def _get_enabled_model(db: Session) -> ModelConfig | None:
-    return db.scalar(
-        select(ModelConfig)
-        .where(ModelConfig.enabled == 1)
-        .order_by(ModelConfig.id.desc())
-        .limit(1)
-    )
+    return ModelRoutingService.default_model(db)
 
 
 def _stream_configured_model(model: ModelConfig, rag_result: RagResult) -> Iterator[str]:
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/periodic_report_service.py b/ai_knowledge_base_v2/apps/backend/app/services/periodic_report_service.py
index 794491b..253a749 100644
--- a/ai_knowledge_base_v2/apps/backend/app/services/periodic_report_service.py
+++ b/ai_knowledge_base_v2/apps/backend/app/services/periodic_report_service.py
@@ -12,7 +12,7 @@ from sqlalchemy.orm import Session
 from app.core.config import get_settings
 from app.models.growth import PeriodicReport, TopicSummary, UserGrowthProfile
 from app.models.user import User
-from app.services.model_service import ModelClientService
+from app.services.tracked_generation_service import TrackedGenerationService
 
 ReportType = Literal["weekly", "monthly", "stage"]
 
@@ -177,9 +177,14 @@ class PeriodicReportService:
 
         try:
             prompt = _report_prompt(user=user, report_type=report_type, period_start=period_start, period_end=period_end, summaries=summaries, profile=profile)
-            report.content = ModelClientService.generate_text_or_raise(db, prompt).strip() or _fallback_report(summaries)
-            model = ModelClientService._get_enabled_model(db)
-            report.model_name = model.model_name if model else None
+            completion = TrackedGenerationService.generate(
+                db,
+                prompt=prompt,
+                scenario="report",
+                user_id=user.id,
+            )
+            report.content = completion.answer.strip() or _fallback_report(summaries)
+            report.model_name = completion.model_name
             report.status = "success"
             report.error_message = None
         except Exception as exc:
diff --git a/ai_knowledge_base_v2/apps/backend/app/services/tracked_generation_service.py b/ai_knowledge_base_v2/apps/backend/app/services/tracked_generation_service.py
new file mode 100644
index 0000000..751d7b0
--- /dev/null
+++ b/ai_knowledge_base_v2/apps/backend/app/services/tracked_generation_service.py
@@ -0,0 +1,64 @@
+from __future__ import annotations
+
+from time import perf_counter
+
+from sqlalchemy.orm import Session
+
+from app.services.ai_request_log_service import AiRequestLogService
+from app.services.model_routing_service import ModelRoutingService, ModelScenario
+from app.services.model_service import ModelClientService, ModelCompletion
+
+
+class TrackedGenerationService:
+    """Runs non-chat generation and records its actual model, tokens and cost."""
+
+    @staticmethod
+    def generate(
+        db: Session,
+        *,
+        prompt: str,
+        scenario: ModelScenario,
+        user_id: int | None,
+    ) -> ModelCompletion:
+        started = perf_counter()
+        try:
+            completion = ModelClientService.generate_text_for_scenario(db, prompt, scenario)
+            AiRequestLogService.write_success(
+                db,
+                session_id=None,
+                message_id=None,
+                user_id=user_id,
+                model_id=completion.model_id,
+                model_name=completion.model_name,
+                prompt=prompt,
+                knowledge_ids="",
+                retrieve_count=0,
+                input_token=completion.input_token,
+                output_token=completion.output_token,
+                cost_ms=_elapsed_ms(started),
+                route_reason=completion.route_reason,
+                question_type=f"background_{scenario}",
+            )
+            return completion
+        except Exception as exc:
+            route = ModelRoutingService.resolve(db, scenario)
+            AiRequestLogService.write_failed(
+                db,
+                session_id=None,
+                message_id=None,
+                user_id=user_id,
+                model_id=route.model.id if route.model is not None else None,
+                model_name=route.model.model_name if route.model is not None else None,
+                prompt=prompt,
+                knowledge_ids="",
+                retrieve_count=0,
+                cost_ms=_elapsed_ms(started),
+                route_reason=route.reason,
+                question_type=f"background_{scenario}",
+                error_message=str(exc)[:2000],
+            )
+            raise
+
+
+def _elapsed_ms(started: float) -> int:
+    return max(0, int((perf_counter() - started) * 1000))
diff --git a/ai_knowledge_base_v2/apps/backend/tests/test_ai_cost_tracking.py b/ai_knowledge_base_v2/apps/backend/tests/test_ai_cost_tracking.py
index 00dd9ae..b1df3dd 100644
--- a/ai_knowledge_base_v2/apps/backend/tests/test_ai_cost_tracking.py
+++ b/ai_knowledge_base_v2/apps/backend/tests/test_ai_cost_tracking.py
@@ -9,6 +9,7 @@ from sqlalchemy.pool import StaticPool
 from app.models import Base
 from app.models.ai_config import ModelConfig
 from app.models.logs import AiRequestLog
+from app.services.admin_service import AdminDashboardService
 from app.services.ai_request_log_service import AiRequestLogService
 
 
@@ -58,3 +59,52 @@ def test_ai_request_log_estimates_cost_from_model_price():
         assert log.question_type == "knowledge_grounded"
         assert "命中知识库" in (log.route_reason or "")
 
+
+def test_dashboard_breaks_cost_down_by_actual_scene_and_model():
+    with _db() as db:
+        model = ModelConfig(
+            id=1,
+            provider="test",
+            api_type="openai_compatible",
+            model_name="report-model",
+            api_url="https://example.com",
+            api_key="secret",
+            input_price_per_1k=Decimal("0.002"),
+            output_price_per_1k=Decimal("0.006"),
+            currency="CNY",
+            timeout_second=30,
+        )
+        db.add(model)
+        db.commit()
+        AiRequestLogService.write_success(
+            db,
+            session_id=None,
+            message_id=None,
+            user_id=3,
+            model_id=1,
+            model_name="report-model",
+            prompt="weekly report",
+            knowledge_ids="",
+            retrieve_count=0,
+            input_token=1000,
+            output_token=500,
+            cost_ms=120,
+            question_type="background_report",
+            route_reason="场景分流：周期报告",
+        )
+        db.commit()
+
+        stats = AdminDashboardService.stats(db)
+
+        assert stats["costBreakdown"] == [
+            {
+                "scene": "background_report",
+                "modelName": "report-model",
+                "requestCount": 1,
+                "inputToken": 1000,
+                "outputToken": 500,
+                "totalToken": 1500,
+                "estimatedCost": 0.005,
+                "currency": "CNY",
+            }
+        ]
diff --git a/ai_knowledge_base_v2/apps/backend/tests/test_model_routing.py b/ai_knowledge_base_v2/apps/backend/tests/test_model_routing.py
new file mode 100644
index 0000000..c4018fe
--- /dev/null
+++ b/ai_knowledge_base_v2/apps/backend/tests/test_model_routing.py
@@ -0,0 +1,154 @@
+from __future__ import annotations
+
+from decimal import Decimal
+
+import pytest
+from fastapi import HTTPException
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session
+from sqlalchemy.pool import StaticPool
+
+from app.models import Base
+from app.api.admin_settings import enable_model, set_default_model
+from app.models.admin import Admin
+from app.models.ai_config import ModelConfig, SystemConfig
+from app.models.logs import AiRequestLog
+from app.schemas.admin import DefaultModelRequest, EnableModelRequest
+from app.services.model_routing_service import ModelRoutingService
+from app.services.model_service import ModelClientService
+from app.services.tracked_generation_service import TrackedGenerationService
+
+
+def _db() -> Session:
+    engine = create_engine(
+        "sqlite:///:memory:",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    Base.metadata.create_all(engine)
+    return Session(engine)
+
+
+def _model(
+    model_id: int,
+    name: str,
+    *,
+    is_default: int,
+    allow_report: int,
+    allow_summary: int,
+) -> ModelConfig:
+    return ModelConfig(
+        id=model_id,
+        provider="test",
+        api_type="openai_compatible",
+        model_name=name,
+        api_url="https://example.com",
+        api_key="secret",
+        enabled=1,
+        is_default=is_default,
+        allow_report=allow_report,
+        allow_summary=allow_summary,
+        allow_fixed_info=1,
+        allow_deep_chat=1,
+        input_price_per_1k=Decimal("0.002"),
+        output_price_per_1k=Decimal("0.006"),
+        currency="CNY",
+        timeout_second=30,
+    )
+
+
+def test_background_scenario_routes_without_changing_live_default_model():
+    with _db() as db:
+        main = _model(1, "main-model", is_default=1, allow_report=0, allow_summary=1)
+        report = _model(2, "report-model", is_default=0, allow_report=1, allow_summary=0)
+        db.add_all([main, report])
+        db.commit()
+
+        report_route = ModelRoutingService.resolve(db, "report")
+        summary_route = ModelRoutingService.resolve(db, "summary")
+
+        assert report_route.model is report
+        assert report_route.fallback_used is False
+        assert summary_route.model is main
+        assert ModelClientService._get_enabled_model(db) is main
+
+
+def test_background_scenario_falls_back_to_default_model():
+    with _db() as db:
+        main = _model(1, "main-model", is_default=1, allow_report=0, allow_summary=0)
+        db.add(main)
+        db.commit()
+
+        route = ModelRoutingService.resolve(db, "report")
+
+        assert route.model is main
+        assert route.fallback_used is True
+        assert "回退默认主模型" in route.reason
+
+
+def test_tracked_background_generation_records_actual_route_tokens_and_cost():
+    with _db() as db:
+        db.add(SystemConfig(config_key="mock_model_enabled", config_value="true"))
+        report = _model(2, "report-model", is_default=0, allow_report=1, allow_summary=0)
+        db.add(report)
+        db.commit()
+
+        completion = TrackedGenerationService.generate(
+            db,
+            prompt="生成本周报告",
+            scenario="report",
+            user_id=7,
+        )
+        db.commit()
+
+        log = db.query(AiRequestLog).one()
+        assert completion.model_name == "report-model"
+        assert log.model_id == report.id
+        assert log.user_id == 7
+        assert log.question_type == "background_report"
+        assert log.total_token == completion.input_token + completion.output_token
+        assert log.estimated_cost is not None
+        assert "周期报告" in (log.route_reason or "")
+
+
+def test_model_pool_keeps_one_default_and_rejects_disabling_last_default():
+    with _db() as db:
+        admin = Admin(id=1, username="admin", password="hash", name="管理员", status=1)
+        main = _model(1, "main-model", is_default=1, allow_report=1, allow_summary=1)
+        alternate = _model(2, "alternate-model", is_default=0, allow_report=1, allow_summary=1)
+        alternate.enabled = 0
+        db.add_all([admin, main, alternate])
+        db.commit()
+
+        enable_model(
+            EnableModelRequest(modelId=alternate.id, enabled=1),
+            db=db,
+            current_admin=admin,
+        )
+        db.refresh(main)
+        db.refresh(alternate)
+        assert main.is_default == 1
+        assert alternate.enabled == 1
+
+        set_default_model(
+            DefaultModelRequest(modelId=alternate.id),
+            db=db,
+            current_admin=admin,
+        )
+        db.refresh(main)
+        db.refresh(alternate)
+        assert main.is_default == 0
+        assert alternate.is_default == 1
+
+        enable_model(
+            EnableModelRequest(modelId=main.id, enabled=0),
+            db=db,
+            current_admin=admin,
+        )
+        with pytest.raises(HTTPException) as exc_info:
+            enable_model(
+                EnableModelRequest(modelId=alternate.id, enabled=0),
+                db=db,
+                current_admin=admin,
+            )
+        assert exc_info.value.status_code == 400
diff --git a/ai_knowledge_base_v2/apps/backend/tests/test_periodic_reports.py b/ai_knowledge_base_v2/apps/backend/tests/test_periodic_reports.py
index c77986c..0c5e8bf 100644
--- a/ai_knowledge_base_v2/apps/backend/tests/test_periodic_reports.py
+++ b/ai_knowledge_base_v2/apps/backend/tests/test_periodic_reports.py
@@ -12,9 +12,9 @@ from app.models.chat import ChatSession, TopicSession
 from app.models.entitlement import EntitlementPlan, UserEntitlement
 from app.models.growth import PeriodicReport, TopicSummary, UserGrowthProfile
 from app.models.user import User
-from app.services.model_service import ModelClientService
 from app.services.periodic_report_service import PeriodicReportService, periodic_report_dict
 from app.services.periodic_report_worker import PeriodicReportWorker, scheduled_period
+from app.services.tracked_generation_service import TrackedGenerationService
 
 
 def _db() -> Session:
@@ -150,9 +150,9 @@ def test_failed_async_report_is_retried(monkeypatch):
         )
         db.commit()
         monkeypatch.setattr(
-            ModelClientService,
-            "generate_text_or_raise",
-            staticmethod(lambda _db, _prompt: (_ for _ in ()).throw(RuntimeError("模型暂时不可用"))),
+            TrackedGenerationService,
+            "generate",
+            staticmethod(lambda *_args, **_kwargs: (_ for _ in ()).throw(RuntimeError("模型暂时不可用"))),
         )
 
         report_id = PeriodicReportWorker.claim_next(db, worker_id="retry-worker", now=_now() + timedelta(seconds=1))
diff --git a/ai_knowledge_base_v2/deployment/DEPLOYMENT_GUIDE.md b/ai_knowledge_base_v2/deployment/DEPLOYMENT_GUIDE.md
index 910f8a5..adfd100 100644
--- a/ai_knowledge_base_v2/deployment/DEPLOYMENT_GUIDE.md
+++ b/ai_knowledge_base_v2/deployment/DEPLOYMENT_GUIDE.md
@@ -163,6 +163,25 @@ PERIODIC_REPORT_STALE_MINUTES=30
 PERIODIC_REPORT_MAX_ATTEMPTS=3
 ```
 
+## 多模型分流
+
+模型管理现在区分两个概念：
+
+- 可用模型：允许后台任务选择，可同时启用多个；
+- 默认主模型：只能有一个，正式用户聊天、追问改写和检索重排始终使用它。
+
+周期报告会选择“周期报告”能力已开启的可用模型，主题摘要和成长档案会选择“摘要沉淀”能力已开启的可用模型。若找不到匹配模型，会自动回退默认主模型，不会因为分流配置缺失直接中断任务。
+
+部署迁移后，旧版本原来启用的模型会自动成为默认主模型。新增其他模型时建议按以下顺序操作：
+
+1. 保存模型并执行“测试”；
+2. 加入可用池；
+3. 只勾选它实际承担的能力；
+4. 如需让低成本模型承担报告，应取消默认主模型的“周期报告”能力，避免默认模型优先命中；
+5. 在数据看板“模型使用与成本”中核对实际模型和成本。
+
+停用或删除唯一默认主模型会被后端拒绝，必须先启用并设置替代主模型。该限制用于避免生产聊天突然变成无模型可用。
+
 ## 回滚原则
 
 1. 先停止新版本服务。
diff --git a/ai_knowledge_base_v2/docs/qianwen_product_todo.md b/ai_knowledge_base_v2/docs/qianwen_product_todo.md
index 1ba289e..7d0fca9 100644
--- a/ai_knowledge_base_v2/docs/qianwen_product_todo.md
+++ b/ai_knowledge_base_v2/docs/qianwen_product_todo.md
@@ -650,6 +650,7 @@ AI 日志增加：
 #### 开发进度
 
 - 2026-07-31：一期已新增模型输入/输出千 Token 单价、币种、适用场景和可用能力字段；AI 请求日志记录模型 ID、估算成本、币种、问题类型、知识命中和路由原因；数据看板展示筛选范围内估算成本。暂未自动切换模型，避免影响正式回答稳定性，后续再基于这些字段做模型分流。
+- 2026-07-31：二期先完成低风险后台任务分流。模型管理支持“多个可用模型 + 一个默认主模型”；周期报告和主题摘要按能力标签选模型，无匹配时回退默认主模型；正式聊天、追问改写和检索重排仍固定使用默认主模型。后台生成会记录实际模型、分流原因、Token、耗时和估算成本，数据看板增加按调用场景、模型和币种拆分的成本明细。固定信息和正式聊天的自动分流暂不启用，待后台任务运行稳定并核对成本后再做。
 
 ---