diff --git a/apps/server/src/modules/ai/analysis/metric-engine.spec.ts b/apps/server/src/modules/ai/analysis/metric-engine.spec.ts
new file mode 100644
index 0000000..3a52fe2
--- /dev/null
+++ b/apps/server/src/modules/ai/analysis/metric-engine.spec.ts
@@ -0,0 +1,93 @@
+import { MetricEngine } from './metric-engine';
+
+describe('MetricEngine', () => {
+  function makeEngine() {
+    const prisma = {
+      xiaobaoRiskSummary: { findMany: jest.fn() },
+      version: { findMany: jest.fn() },
+      versionPlan: { findMany: jest.fn() },
+      devTask: { findMany: jest.fn() },
+      testCase: { findMany: jest.fn() },
+      bug: { findMany: jest.fn() },
+      requirement: { findMany: jest.fn() },
+      taskWorklog: { findMany: jest.fn() },
+      overtimeRecord: { findMany: jest.fn() },
+      user: { findMany: jest.fn() },
+    };
+    return { prisma, engine: new MetricEngine(prisma as any) };
+  }
+
+  it('returns version risk ranking from Xiaobao summaries', async () => {
+    const { prisma, engine } = makeEngine();
+    prisma.xiaobaoRiskSummary.findMany.mockResolvedValue([
+      { versionId: 'ver-1', riskLevel: 'blocked', riskScore: 92, updatedAt: new Date('2026-07-08T00:00:00.000Z') },
+      { versionId: 'ver-2', riskLevel: 'at_risk', riskScore: 71, updatedAt: new Date('2026-07-08T00:00:00.000Z') },
+    ]);
+    prisma.version.findMany.mockResolvedValue([
+      { id: 'ver-1', name: 'V1', projectId: 'project-1', productId: 'product-1' },
+      { id: 'ver-2', name: 'V2', projectId: 'project-1', productId: 'product-1' },
+    ]);
+
+    const result = await engine.executeMetric({
+      metricRef: { metricId: 'version_risk_score', version: 1 },
+      analysisType: 'ranking',
+      dimensions: ['version'],
+      filters: {},
+      scope: { type: 'project', projectId: 'project-1' },
+      limit: 10,
+    }, new Date('2026-07-08T12:00:00.000Z'));
+
+    expect(result.rows).toEqual([
+      { versionId: 'ver-1', label: 'V1', value: 92, riskLevel: 'blocked' },
+      { versionId: 'ver-2', label: 'V2', value: 71, riskLevel: 'at_risk' },
+    ]);
+    expect(result.evidence[0]).toMatchObject({ label: '风险版本', value: 2, sourceDomain: 'xiaobao' });
+  });
+
+  it('groups member pending work across plans, tasks, cases, and bugs', async () => {
+    const { prisma, engine } = makeEngine();
+    prisma.versionPlan.findMany.mockResolvedValue([{ id: 'p1', ownerId: 'm-1', title: '产品方案', versionId: 'ver-1' }]);
+    prisma.devTask.findMany.mockResolvedValue([{ id: 'd1', assigneeId: 'm-1', title: '接口', versionId: 'ver-1' }]);
+    prisma.testCase.findMany.mockResolvedValue([{ id: 't1', assigneeId: 'm-2', title: '测试', versionId: 'ver-1' }]);
+    prisma.bug.findMany.mockResolvedValue([{ id: 'b1', assigneeId: 'm-1', title: '缺陷', versionId: 'ver-1' }]);
+    prisma.user.findMany.mockResolvedValue([
+      { id: 'm-1', name: '张三', departmentId: '研发' },
+      { id: 'm-2', name: '李四', departmentId: '测试' },
+    ]);
+
+    const result = await engine.executeMetric({
+      metricRef: { metricId: 'member_pending_work', version: 1 },
+      analysisType: 'ranking',
+      dimensions: ['member'],
+      filters: {},
+      scope: { type: 'version', versionId: 'ver-1' },
+      limit: 10,
+    });
+
+    expect(result.rows).toEqual([
+      { memberId: 'm-1', label: '张三', value: 3 },
+      { memberId: 'm-2', label: '李四', value: 1 },
+    ]);
+  });
+
+  it('returns no-data evidence for empty requirement trends', async () => {
+    const { prisma, engine } = makeEngine();
+    prisma.requirement.findMany.mockResolvedValue([]);
+
+    const result = await engine.executeMetric({
+      metricRef: { metricId: 'requirement_completion_count', version: 1 },
+      analysisType: 'trend',
+      dimensions: ['day'],
+      filters: {},
+      scope: { type: 'self', userId: 'm-1' },
+      timeRange: {
+        start: '2026-06-09T00:00:00.000Z',
+        end: '2026-07-08T23:59:59.999Z',
+        policy: 'last_30_days',
+      },
+    });
+
+    expect(result.rows).toEqual([]);
+    expect(result.evidence).toEqual([{ label: '可统计记录', value: 0, sourceDomain: 'requirement' }]);
+  });
+});
diff --git a/apps/server/src/modules/ai/analysis/metric-engine.ts b/apps/server/src/modules/ai/analysis/metric-engine.ts
new file mode 100644
index 0000000..54d98f6
--- /dev/null
+++ b/apps/server/src/modules/ai/analysis/metric-engine.ts
@@ -0,0 +1,461 @@
+import { Injectable } from '@nestjs/common';
+import type { AnalysisPlan, DataScope, EvidenceItem, MetricResult } from '@ftb/shared';
+import { PrismaService } from '../../../prisma/prisma.service';
+import { buildScopedWhere } from './permission-scope-resolver';
+
+type AnalysisDomain =
+  | 'version'
+  | 'versionPlan'
+  | 'devTask'
+  | 'testCase'
+  | 'bug'
+  | 'requirement'
+  | 'taskWorklog'
+  | 'overtimeRecord';
+
+type OpenWorkItem = {
+  id: string;
+  versionId?: string | null;
+  title: string;
+  ownerId?: string | null;
+  assigneeId?: string | null;
+};
+
+type VersionRow = { id: string; name: string; projectId?: string | null; productId?: string | null };
+type RiskSummaryRow = { versionId: string; riskLevel: string; riskScore: number; updatedAt: Date };
+type UserRow = { id: string; name: string; departmentId?: string | null };
+type UserDepartmentRow = { id: string; departmentId?: string | null };
+type StatusRow = { status: string };
+type RequirementSourceRow = { sourceType: string | null; type: string | null };
+type DateRow = { updatedAt: Date };
+type WorkHoursRow = { userId: string | null; hours: number };
+type BugSeverityRow = { severity: string };
+type TestStatusRow = { status: string; updatedAt: Date };
+type OvertimeReasonRow = { reason: string; hours: number };
+
+@Injectable()
+export class MetricEngine {
+  constructor(private readonly prisma: PrismaService) {}
+
+  async executeMetric(plan: AnalysisPlan, now = new Date()): Promise<MetricResult> {
+    if (plan.metricRef.metricId === 'version_risk_score') return this.versionRiskRanking(plan, now);
+    if (plan.metricRef.metricId === 'member_pending_work') return this.memberPendingWork(plan, now);
+    if (plan.metricRef.metricId === 'department_workload') return this.departmentWorkload(plan, now);
+    if (plan.metricRef.metricId === 'overdue_item_count') return this.overdueItemCount(plan, now);
+    if (plan.metricRef.metricId === 'requirement_status_count') return this.requirementStatusCount(plan, now);
+    if (plan.metricRef.metricId === 'requirement_completion_count') return this.requirementCompletionTrend(plan, now);
+    if (plan.metricRef.metricId === 'requirement_source_count') return this.requirementSourceCount(plan, now);
+    if (plan.metricRef.metricId === 'member_effort_hours') return this.memberEffortHours(plan, now);
+    if (plan.metricRef.metricId === 'bug_severity_count') return this.bugSeverityCount(plan, now);
+    if (plan.metricRef.metricId === 'test_pass_rate') return this.testPassRate(plan, now);
+    if (plan.metricRef.metricId === 'overtime_reason_hours') return this.overtimeReasonHours(plan, now);
+    if (plan.metricRef.metricId === 'completion_trend') return this.completionTrend(plan, now);
+    if (plan.metricRef.metricId === 'delay_rate') return this.delayRate(plan, now);
+    if (plan.metricRef.metricId === 'delay_reason_count') return this.delayReasonCount(plan, now);
+
+    return emptyResult(plan, now, [{ label: '可统计记录', value: 0, sourceDomain: 'project' }]);
+  }
+
+  private async versionRiskRanking(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const versions = await this.prisma.version.findMany({
+      where: domainWhere(plan.scope, 'version'),
+      select: { id: true, name: true, projectId: true, productId: true },
+    }) as VersionRow[];
+    const versionById = new Map(versions.map((version) => [version.id, version]));
+    const versionIds = versions.map((version) => version.id);
+    const rows: RiskSummaryRow[] = versionIds.length === 0
+      ? []
+      : await this.prisma.xiaobaoRiskSummary.findMany({
+        where: { versionId: { in: versionIds } },
+        orderBy: [{ riskScore: 'desc' }, { updatedAt: 'desc' }],
+        take: plan.limit ?? 10,
+      }) as RiskSummaryRow[];
+
+    return {
+      metricRef: plan.metricRef,
+      analysisType: plan.analysisType,
+      columns: [
+        { id: 'label', label: '版本', type: 'string' },
+        { id: 'value', label: '风险分', type: 'number' },
+        { id: 'riskLevel', label: '风险等级', type: 'string' },
+      ],
+      rows: rows.map((row) => ({
+        versionId: row.versionId,
+        label: versionById.get(row.versionId)?.name ?? row.versionId,
+        value: row.riskScore,
+        riskLevel: row.riskLevel,
+      })),
+      evidence: [{ label: '风险版本', value: rows.length, sourceDomain: 'xiaobao' }],
+      dataScope: plan.scope,
+      generatedAt: now.toISOString(),
+    };
+  }
+
+  private async memberPendingWork(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const [plans, devTasks, testCases, bugs] = await Promise.all([
+      this.prisma.versionPlan.findMany({
+        where: { ...domainWhere(plan.scope, 'versionPlan'), status: { not: 'completed' } },
+      }),
+      this.prisma.devTask.findMany({
+        where: { ...domainWhere(plan.scope, 'devTask'), status: { not: 'submitted' } },
+      }),
+      this.prisma.testCase.findMany({
+        where: { ...domainWhere(plan.scope, 'testCase'), status: { notIn: ['passed', 'failed', 'blocked'] } },
+      }),
+      this.prisma.bug.findMany({
+        where: { ...domainWhere(plan.scope, 'bug'), status: { in: ['open', 'fixing', 'fixed', 'verifying'] } },
+      }),
+    ]) as [OpenWorkItem[], OpenWorkItem[], OpenWorkItem[], OpenWorkItem[]];
+    const openItems: OpenWorkItem[] = [
+      ...plans.map((planItem) => ({ ...planItem, assigneeId: planItem.ownerId })),
+      ...devTasks,
+      ...testCases,
+      ...bugs,
+    ];
+    const counts = countByMember(openItems);
+    const users = await this.prisma.user.findMany({
+      where: { id: { in: Array.from(counts.keys()) } },
+      select: { id: true, name: true, departmentId: true },
+    }) as UserRow[];
+    const userById = new Map(users.map((user) => [user.id, user]));
+    const rows = Array.from(counts.entries())
+      .map(([memberId, value]) => ({ memberId, label: userById.get(memberId)?.name ?? memberId, value }))
+      .sort((a, b) => b.value - a.value || a.label.localeCompare(b.label))
+      .slice(0, plan.limit ?? 10);
+
+    return {
+      metricRef: plan.metricRef,
+      analysisType: plan.analysisType,
+      columns: [
+        { id: 'label', label: '成员', type: 'string' },
+        { id: 'value', label: '待办数', type: 'number' },
+      ],
+      rows,
+      evidence: [{ label: '未完成事项', value: sumCounts(counts), sourceDomain: 'dev_task' }],
+      dataScope: plan.scope,
+      generatedAt: now.toISOString(),
+    };
+  }
+
+  private async departmentWorkload(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const memberResult = await this.memberPendingWork({
+      ...plan,
+      metricRef: { metricId: 'member_pending_work', version: 1 },
+      dimensions: ['member'],
+    }, now);
+    const memberIds = memberResult.rows.map((row) => String(row.memberId ?? '')).filter(Boolean);
+    const users = await this.prisma.user.findMany({
+      where: { id: { in: memberIds } },
+      select: { id: true, departmentId: true },
+    }) as UserDepartmentRow[];
+    const departmentByMember = new Map(users.map((user) => [user.id, user.departmentId || '未分部门']));
+    const counts = new Map<string, number>();
+    for (const row of memberResult.rows) {
+      const department = departmentByMember.get(String(row.memberId)) ?? '未分部门';
+      counts.set(department, (counts.get(department) ?? 0) + Number(row.value ?? 0));
+    }
+    return rowsResult(
+      plan,
+      now,
+      '部门',
+      '待办数',
+      Array.from(counts.entries()).map(([label, value]) => ({ label, value })),
+      'dev_task',
+    );
+  }
+
+  private async overdueItemCount(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const [plans, devTasks, testCases, bugs] = await Promise.all([
+      this.prisma.versionPlan.findMany({
+        where: { ...domainWhere(plan.scope, 'versionPlan'), status: { not: 'completed' }, expectedEndAt: { lt: now } },
+      }),
+      this.prisma.devTask.findMany({
+        where: { ...domainWhere(plan.scope, 'devTask'), status: { not: 'submitted' }, expectedEndAt: { lt: now } },
+      }),
+      this.prisma.testCase.findMany({
+        where: {
+          ...domainWhere(plan.scope, 'testCase'),
+          status: { notIn: ['passed', 'failed', 'blocked'] },
+          plannedEndAt: { lt: now },
+        },
+      }),
+      this.prisma.bug.findMany({
+        where: { ...domainWhere(plan.scope, 'bug'), status: { in: ['open', 'fixing', 'fixed', 'verifying'] }, plannedFixAt: { lt: now } },
+      }),
+    ]) as [OpenWorkItem[], OpenWorkItem[], OpenWorkItem[], OpenWorkItem[]];
+    const byVersion = new Map<string, number>();
+    for (const item of [...plans, ...devTasks, ...testCases, ...bugs]) {
+      if (!item.versionId) continue;
+      byVersion.set(item.versionId, (byVersion.get(item.versionId) ?? 0) + 1);
+    }
+    return rowsResult(
+      plan,
+      now,
+      '版本',
+      '逾期数',
+      Array.from(byVersion.entries()).map(([label, value]) => ({ label, value })),
+      'version',
+    );
+  }
+
+  private async requirementStatusCount(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const rows = await this.prisma.requirement.findMany({
+      where: domainWhere(plan.scope, 'requirement'),
+      select: { status: true },
+    }) as StatusRow[];
+    return countRows(plan, now, rows.map((row) => row.status || 'unknown'), '状态', '数量', 'requirement');
+  }
+
+  private async requirementCompletionTrend(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const where = {
+      ...domainWhere(plan.scope, 'requirement'),
+      status: { in: ['released', 'closed'] },
+      ...timeFilter(plan, 'updatedAt'),
+    };
+    const rows = await this.prisma.requirement.findMany({ where, select: { updatedAt: true } }) as DateRow[];
+    return trendRows(plan, now, rows.map((row) => row.updatedAt), '完成需求', 'requirement');
+  }
+
+  private async requirementSourceCount(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const where = { ...domainWhere(plan.scope, 'requirement'), ...timeFilter(plan, 'createdAt') };
+    const rows = await this.prisma.requirement.findMany({ where, select: { sourceType: true, type: true } }) as RequirementSourceRow[];
+    const dimension = plan.dimensions.includes('requirement_type') ? 'type' : 'sourceType';
+    return countRows(plan, now, rows.map((row) => row[dimension] || '未填写'), '类别', '数量', 'requirement');
+  }
+
+  private async memberEffortHours(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const [worklogs, overtime] = await Promise.all([
+      this.prisma.taskWorklog.findMany({
+        where: { ...domainWhere(plan.scope, 'taskWorklog'), ...timeFilter(plan, 'createdAt') },
+        select: { userId: true, hours: true },
+      }),
+      this.prisma.overtimeRecord.findMany({
+        where: { ...domainWhere(plan.scope, 'overtimeRecord'), ...timeFilter(plan, 'createdAt') },
+        select: { userId: true, hours: true },
+      }),
+    ]) as [WorkHoursRow[], WorkHoursRow[]];
+    const hours = new Map<string, number>();
+    for (const row of [...worklogs, ...overtime]) {
+      if (!row.userId) continue;
+      hours.set(row.userId, (hours.get(row.userId) ?? 0) + Number(row.hours ?? 0));
+    }
+    const users = await this.prisma.user.findMany({
+      where: { id: { in: Array.from(hours.keys()) } },
+      select: { id: true, name: true },
+    }) as Array<Pick<UserRow, 'id' | 'name'>>;
+    const userById = new Map(users.map((user) => [user.id, user.name]));
+    return rowsResult(
+      plan,
+      now,
+      '成员',
+      '小时',
+      Array.from(hours.entries()).map(([memberId, value]) => ({
+        memberId,
+        label: userById.get(memberId) ?? memberId,
+        value,
+      })),
+      'task_worklog',
+    );
+  }
+
+  private async bugSeverityCount(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const rows = await this.prisma.bug.findMany({
+      where: { ...domainWhere(plan.scope, 'bug'), status: { notIn: ['closed', 'rejected'] } },
+      select: { severity: true },
+    }) as BugSeverityRow[];
+    return countRows(plan, now, rows.map((row) => row.severity || 'normal'), '严重度', 'Bug 数', 'bug');
+  }
+
+  private async testPassRate(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const rows = await this.prisma.testCase.findMany({
+      where: {
+        ...domainWhere(plan.scope, 'testCase'),
+        status: { in: ['passed', 'failed', 'blocked'] },
+        ...timeFilter(plan, 'updatedAt'),
+      },
+      select: { status: true, updatedAt: true },
+    }) as TestStatusRow[];
+    const buckets = bucketDates(rows.map((row) => row.updatedAt));
+    const source = Array.from(buckets.keys()).map((label) => {
+      const sameDay = rows.filter((row) => dayKey(row.updatedAt) === label);
+      const passed = sameDay.filter((row) => row.status === 'passed').length;
+      return { label, value: sameDay.length === 0 ? 0 : Math.round((passed / sameDay.length) * 100) };
+    });
+    return rowsResult(plan, now, '日期', '通过率', source, 'test_case');
+  }
+
+  private async overtimeReasonHours(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const rows = await this.prisma.overtimeRecord.findMany({
+      where: { ...domainWhere(plan.scope, 'overtimeRecord'), ...timeFilter(plan, 'createdAt') },
+      select: { reason: true, hours: true },
+    }) as OvertimeReasonRow[];
+    const hours = new Map<string, number>();
+    for (const row of rows) {
+      const reason = row.reason || '未填写';
+      hours.set(reason, (hours.get(reason) ?? 0) + Number(row.hours ?? 0));
+    }
+    return rowsResult(
+      plan,
+      now,
+      '原因',
+      '小时',
+      Array.from(hours.entries()).map(([label, value]) => ({ label, value })),
+      'overtime',
+    );
+  }
+
+  private async completionTrend(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    return this.requirementCompletionTrend({
+      ...plan,
+      metricRef: { metricId: 'requirement_completion_count', version: 1 },
+      dimensions: ['day'],
+    }, now);
+  }
+
+  private async delayRate(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    const overdue = await this.overdueItemCount({
+      ...plan,
+      metricRef: { metricId: 'overdue_item_count', version: 1 },
+      dimensions: ['version'],
+      analysisType: 'ranking',
+    }, now);
+    const total = overdue.rows.reduce((sum, row) => sum + Number(row.value ?? 0), 0);
+    return {
+      ...overdue,
+      metricRef: plan.metricRef,
+      rows: overdue.rows.map((row) => ({ ...row, value: total === 0 ? 0 : Number(row.value ?? 0) / total })),
+    };
+  }
+
+  private async delayReasonCount(plan: AnalysisPlan, now: Date): Promise<MetricResult> {
+    return this.overtimeReasonHours({
+      ...plan,
+      metricRef: { metricId: 'overtime_reason_hours', version: 1 },
+      dimensions: ['delay_reason'],
+    }, now);
+  }
+}
+
+function domainWhere(scope: DataScope, domain: AnalysisDomain): Record<string, unknown> {
+  const scopedWhere = buildScopedWhere(scope);
+  const base = domain === 'version' && 'versionId' in scopedWhere
+    ? { id: scopedWhere.versionId }
+    : scopedWhere;
+
+  if (scope.type !== 'self') return base;
+
+  if (domain === 'version') return { id: { in: [] } };
+  if (domain === 'versionPlan') return { ...base, ownerId: scope.userId };
+  if (domain === 'devTask' || domain === 'testCase' || domain === 'bug') return { ...base, assigneeId: scope.userId };
+  if (domain === 'requirement') return { ...base, creatorId: scope.userId };
+  if (domain === 'taskWorklog' || domain === 'overtimeRecord') return { ...base, userId: scope.userId };
+  return base;
+}
+
+function timeFilter(plan: AnalysisPlan, field: string): Record<string, unknown> {
+  if (!plan.timeRange) return {};
+  return { [field]: { gte: new Date(plan.timeRange.start), lte: new Date(plan.timeRange.end) } };
+}
+
+function countByMember(items: OpenWorkItem[]): Map<string, number> {
+  const counts = new Map<string, number>();
+  for (const item of items) {
+    const memberId = item.assigneeId ?? item.ownerId;
+    if (!memberId) continue;
+    counts.set(memberId, (counts.get(memberId) ?? 0) + 1);
+  }
+  return counts;
+}
+
+function sumCounts(counts: Map<string, number>): number {
+  return Array.from(counts.values()).reduce((sum, count) => sum + count, 0);
+}
+
+function rowsResult(
+  plan: AnalysisPlan,
+  now: Date,
+  labelName: string,
+  valueName: string,
+  rows: Array<Record<string, string | number | null>>,
+  sourceDomain: EvidenceItem['sourceDomain'],
+): MetricResult {
+  const sorted = rows
+    .sort((a, b) => Number(b.value ?? 0) - Number(a.value ?? 0))
+    .slice(0, plan.limit ?? rows.length);
+
+  return {
+    metricRef: plan.metricRef,
+    analysisType: plan.analysisType,
+    columns: [
+      { id: 'label', label: labelName, type: 'string' },
+      { id: 'value', label: valueName, type: 'number' },
+    ],
+    rows: sorted,
+    evidence: [{ label: '可统计记录', value: rows.length, sourceDomain }],
+    dataScope: plan.scope,
+    generatedAt: now.toISOString(),
+  };
+}
+
+function countRows(
+  plan: AnalysisPlan,
+  now: Date,
+  labels: string[],
+  labelName: string,
+  valueName: string,
+  sourceDomain: EvidenceItem['sourceDomain'],
+): MetricResult {
+  const counts = new Map<string, number>();
+  for (const label of labels) counts.set(label, (counts.get(label) ?? 0) + 1);
+  return rowsResult(
+    plan,
+    now,
+    labelName,
+    valueName,
+    Array.from(counts.entries()).map(([label, value]) => ({ label, value })),
+    sourceDomain,
+  );
+}
+
+function trendRows(
+  plan: AnalysisPlan,
+  now: Date,
+  dates: Date[],
+  valueLabel: string,
+  sourceDomain: EvidenceItem['sourceDomain'],
+): MetricResult {
+  const buckets = bucketDates(dates);
+  return rowsResult(
+    plan,
+    now,
+    '日期',
+    valueLabel,
+    Array.from(buckets.entries()).map(([label, value]) => ({ label, value })),
+    sourceDomain,
+  );
+}
+
+function bucketDates(dates: Date[]): Map<string, number> {
+  const buckets = new Map<string, number>();
+  for (const date of dates) {
+    const key = dayKey(date);
+    buckets.set(key, (buckets.get(key) ?? 0) + 1);
+  }
+  return buckets;
+}
+
+function dayKey(value: Date | string): string {
+  return new Date(value).toISOString().slice(0, 10);
+}
+
+function emptyResult(plan: AnalysisPlan, now: Date, evidence: EvidenceItem[]): MetricResult {
+  return {
+    metricRef: plan.metricRef,
+    analysisType: plan.analysisType,
+    columns: [],
+    rows: [],
+    evidence,
+    dataScope: plan.scope,
+    generatedAt: now.toISOString(),
+  };
+}