diff --git a/services/platform-service/src/modules/ai-budgets/repository.ts b/services/platform-service/src/modules/ai-budgets/repository.ts
index 5e44f955..61b113ee 100644
--- a/services/platform-service/src/modules/ai-budgets/repository.ts
+++ b/services/platform-service/src/modules/ai-budgets/repository.ts
@@ -3,6 +3,7 @@ import { getCollection } from '../../lib/datastore.js';
 import type {
   BudgetAlertDoc,
   BudgetPolicyDoc,
+  BudgetRolloverDoc,
   BudgetSpendEntryDoc,
   ListBudgetAlertsQuery,
   ListBudgetPoliciesQuery,
@@ -98,3 +99,54 @@ export async function listAlerts(
     limit: query.limit,
   });
 }
+
+// ── Budget Rollover ─────────────────────────────────────────
+
+function rolloverCollection() {
+  return getCollection<BudgetRolloverDoc>('ai_budget_rollovers', '/productId');
+}
+
+export async function createRollover(doc: BudgetRolloverDoc): Promise<BudgetRolloverDoc> {
+  return rolloverCollection().create(doc);
+}
+
+export async function listRollovers(
+  productId: string,
+  policyId: string
+): Promise<BudgetRolloverDoc[]> {
+  return rolloverCollection().findMany({
+    filter: { productId, policyId },
+    sort: { createdAt: -1 },
+    limit: 50,
+  });
+}
+
+// ── Cost Dashboard ──────────────────────────────────────────
+
+export async function listAllSpendEntries(
+  productId: string,
+  options: {
+    scopeType?: string;
+    scopeId?: string;
+    since?: string;
+    until?: string;
+    limit?: number;
+  } = {}
+): Promise<BudgetSpendEntryDoc[]> {
+  const entries = await spendCollection().findMany({
+    filter: {
+      productId,
+      ...(options.scopeType ? { scopeType: options.scopeType } : {}),
+      ...(options.scopeId ? { scopeId: options.scopeId } : {}),
+    },
+    sort: { recordedAt: -1 },
+    limit: options.limit ?? 500,
+  });
+
+  // Filter by time range in-memory
+  return entries.filter(e => {
+    if (options.since && e.recordedAt < options.since) return false;
+    if (options.until && e.recordedAt > options.until) return false;
+    return true;
+  });
+}
diff --git a/services/platform-service/src/modules/ai-budgets/routes.test.ts b/services/platform-service/src/modules/ai-budgets/routes.test.ts
index 8b1c0720..03bb370b 100644
--- a/services/platform-service/src/modules/ai-budgets/routes.test.ts
+++ b/services/platform-service/src/modules/ai-budgets/routes.test.ts
@@ -10,6 +10,9 @@ const repoMock = {
   listSpendEntries: vi.fn(),
   createAlerts: vi.fn(),
   listAlerts: vi.fn(),
+  listAllSpendEntries: vi.fn(),
+  createRollover: vi.fn(),
+  listRollovers: vi.fn(),
 };
 
 vi.mock('./repository.js', () => repoMock);
@@ -130,4 +133,198 @@ describe('aiBudgetRoutes', () => {
       })
     );
   });
+
+  // ── Scope expansion ─────────────────────────────────────
+
+  it('POST /ai-budgets/policies supports org scope', async () => {
+    repoMock.createPolicy.mockResolvedValue({ id: 'aibudget_2', scopeType: 'org' });
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/ai-budgets/policies',
+      payload: { scopeType: 'org', scopeId: 'org_1', name: 'Org Budget', budgetUsd: 500 },
+    });
+
+    expect(res.statusCode).toBe(200);
+    expect(repoMock.createPolicy).toHaveBeenCalledWith(
+      expect.objectContaining({ scopeType: 'org', scopeId: 'org_1' })
+    );
+  });
+
+  it('POST /ai-budgets/policies supports workspace scope', async () => {
+    repoMock.createPolicy.mockResolvedValue({ id: 'aibudget_3', scopeType: 'workspace' });
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/ai-budgets/policies',
+      payload: { scopeType: 'workspace', scopeId: 'ws_1', name: 'WS Budget', budgetUsd: 100 },
+    });
+
+    expect(res.statusCode).toBe(200);
+    expect(repoMock.createPolicy).toHaveBeenCalledWith(
+      expect.objectContaining({ scopeType: 'workspace' })
+    );
+  });
+
+  // ── Cost Dashboard ──────────────────────────────────────
+
+  it('GET /ai-budgets/costs returns grouped cost breakdown', async () => {
+    repoMock.listAllSpendEntries.mockResolvedValue([
+      { costUsd: 5, tokensUsed: 100, model: 'gpt-4o', recordedAt: '2026-03-15T00:00:00Z' },
+      { costUsd: 3, tokensUsed: 80, model: 'gpt-4o', recordedAt: '2026-03-15T01:00:00Z' },
+      { costUsd: 1, tokensUsed: 50, model: 'gpt-4o-mini', recordedAt: '2026-03-15T02:00:00Z' },
+    ]);
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+
+    const res = await app.inject({ method: 'GET', url: '/api/ai-budgets/costs?groupBy=model' });
+    expect(res.statusCode).toBe(200);
+    const body = res.json();
+    expect(body.totalCostUsd).toBe(9);
+    expect(body.totalTokens).toBe(230);
+    expect(body.breakdown).toHaveLength(2);
+    expect(body.breakdown[0].key).toBe('gpt-4o');
+  });
+
+  it('GET /ai-budgets/costs groups by day', async () => {
+    repoMock.listAllSpendEntries.mockResolvedValue([
+      { costUsd: 5, tokensUsed: 100, recordedAt: '2026-03-15T00:00:00Z' },
+      { costUsd: 3, tokensUsed: 80, recordedAt: '2026-03-16T01:00:00Z' },
+    ]);
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+
+    const res = await app.inject({ method: 'GET', url: '/api/ai-budgets/costs?groupBy=day' });
+    expect(res.statusCode).toBe(200);
+    expect(res.json().breakdown).toHaveLength(2);
+  });
+
+  // ── Budget Rollover ─────────────────────────────────────
+
+  it('POST /ai-budgets/policies/:id/rollover creates rollover and adjusts budget', async () => {
+    repoMock.getPolicy.mockResolvedValue({
+      id: 'aibudget_1',
+      productId: 'lysnrai',
+      period: 'monthly',
+      budgetUsd: 100,
+      metadata: {},
+    });
+    repoMock.listSpendEntries.mockResolvedValue([
+      { costUsd: 60, recordedAt: '2026-02-10T00:00:00Z' },
+    ]);
+    repoMock.createRollover.mockImplementation(async (doc: Record<string, unknown>) => doc);
+    repoMock.updatePolicy.mockResolvedValue({ budgetUsd: 140 });
+
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/ai-budgets/policies/aibudget_1/rollover',
+    });
+
+    expect(res.statusCode).toBe(200);
+    expect(repoMock.createRollover).toHaveBeenCalled();
+    expect(repoMock.updatePolicy).toHaveBeenCalledWith(
+      'aibudget_1',
+      'lysnrai',
+      expect.objectContaining({ budgetUsd: expect.any(Number) })
+    );
+  });
+
+  it('GET /ai-budgets/policies/:id/rollovers returns rollover history', async () => {
+    repoMock.listRollovers.mockResolvedValue([
+      { id: 'airollover_1', policyId: 'aibudget_1', rolledOverUsd: 40 },
+    ]);
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+
+    const res = await app.inject({
+      method: 'GET',
+      url: '/api/ai-budgets/policies/aibudget_1/rollovers',
+    });
+    expect(res.statusCode).toBe(200);
+    expect(res.json()).toHaveLength(1);
+  });
+
+  // ── Enforcement Check ───────────────────────────────────
+
+  it('POST /ai-budgets/check returns allow when under budget', async () => {
+    repoMock.listPolicies.mockResolvedValue([
+      {
+        id: 'aibudget_1',
+        status: 'active',
+        period: 'monthly',
+        budgetUsd: 100,
+        softThreshold: 0.8,
+        hardThreshold: 1,
+        modelAllowlist: [],
+        name: 'Test',
+      },
+    ]);
+    repoMock.listSpendEntries.mockResolvedValue([
+      { costUsd: 20, recordedAt: '2026-03-15T00:00:00Z' },
+    ]);
+
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/ai-budgets/check',
+      payload: { scopeType: 'agent', scopeId: 'agt_1', estimatedCostUsd: 5 },
+    });
+
+    expect(res.statusCode).toBe(200);
+    expect(res.json().verdict).toBe('allow');
+  });
+
+  it('POST /ai-budgets/check returns block when model not allowed', async () => {
+    repoMock.listPolicies.mockResolvedValue([
+      {
+        id: 'aibudget_1',
+        status: 'active',
+        period: 'monthly',
+        budgetUsd: 100,
+        softThreshold: 0.8,
+        hardThreshold: 1,
+        modelAllowlist: ['gpt-4o-mini'],
+        name: 'Test',
+      },
+    ]);
+
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/ai-budgets/check',
+      payload: { scopeType: 'agent', scopeId: 'agt_1', estimatedCostUsd: 5, model: 'gpt-4.1' },
+    });
+
+    expect(res.statusCode).toBe(200);
+    expect(res.json().verdict).toBe('block');
+    expect(res.json().reasons[0]).toContain('not in allowlist');
+  });
+
+  it('POST /ai-budgets/check returns warn when approaching soft threshold', async () => {
+    repoMock.listPolicies.mockResolvedValue([
+      {
+        id: 'aibudget_1',
+        status: 'active',
+        period: 'monthly',
+        budgetUsd: 100,
+        softThreshold: 0.8,
+        hardThreshold: 1,
+        modelAllowlist: [],
+        name: 'Test',
+      },
+    ]);
+    repoMock.listSpendEntries.mockResolvedValue([
+      { costUsd: 75, recordedAt: '2026-03-15T00:00:00Z' },
+    ]);
+
+    const app = await buildApp({ sub: 'admin_1', productId: 'lysnrai', role: 'admin' });
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/ai-budgets/check',
+      payload: { scopeType: 'agent', scopeId: 'agt_1', estimatedCostUsd: 10 },
+    });
+
+    expect(res.statusCode).toBe(200);
+    expect(res.json().verdict).toBe('warn');
+  });
 });
diff --git a/services/platform-service/src/modules/ai-budgets/routes.ts b/services/platform-service/src/modules/ai-budgets/routes.ts
index 439e9c09..eeeffd83 100644
--- a/services/platform-service/src/modules/ai-budgets/routes.ts
+++ b/services/platform-service/src/modules/ai-budgets/routes.ts
@@ -4,7 +4,9 @@ import { BadRequestError, ForbiddenError } from '../../lib/errors.js';
 import {
   BudgetAlertDoc,
   BudgetPolicyDoc,
+  BudgetRolloverDoc,
   BudgetSpendEntryDoc,
+  CostDashboardQuerySchema,
   CreateBudgetPolicySchema,
   ListBudgetAlertsQuerySchema,
   ListBudgetPoliciesQuerySchema,
@@ -248,4 +250,197 @@ export async function aiBudgetRoutes(app: FastifyInstance) {
       alerts,
     };
   });
+
+  // ── Cost Dashboard ──────────────────────────────────────
+
+  app.get('/ai-budgets/costs', async req => {
+    const access = requireAdmin(req);
+    const parsed = CostDashboardQuerySchema.safeParse(req.query);
+    if (!parsed.success) {
+      validationError(parsed.error.issues.map(issue => issue.message).join('; '));
+    }
+
+    const entries = await repo.listAllSpendEntries(access.productId, {
+      scopeType: parsed.data.scopeType,
+      scopeId: parsed.data.scopeId,
+      since: parsed.data.since,
+      until: parsed.data.until,
+      limit: parsed.data.limit,
+    });
+
+    const totalCostUsd = entries.reduce((sum, e) => sum + e.costUsd, 0);
+    const totalTokens = entries.reduce((sum, e) => sum + e.tokensUsed, 0);
+
+    // Group by requested dimension
+    const groups = new Map<string, { costUsd: number; tokensUsed: number; count: number }>();
+    for (const entry of entries) {
+      let key: string;
+      switch (parsed.data.groupBy) {
+        case 'model':
+          key = entry.model ?? 'unknown';
+          break;
+        case 'agent':
+          key = entry.agentId ?? 'unknown';
+          break;
+        case 'day':
+          key = entry.recordedAt.slice(0, 10);
+          break;
+        case 'scope':
+          key = `${entry.scopeType}:${entry.scopeId}`;
+          break;
+        default:
+          key = 'all';
+      }
+      const existing = groups.get(key) ?? { costUsd: 0, tokensUsed: 0, count: 0 };
+      existing.costUsd += entry.costUsd;
+      existing.tokensUsed += entry.tokensUsed;
+      existing.count++;
+      groups.set(key, existing);
+    }
+
+    const breakdown = Array.from(groups.entries())
+      .map(([key, data]) => ({ key, ...data }))
+      .sort((a, b) => b.costUsd - a.costUsd);
+
+    return {
+      totalCostUsd: Math.round(totalCostUsd * 10000) / 10000,
+      totalTokens,
+      entryCount: entries.length,
+      groupBy: parsed.data.groupBy,
+      breakdown,
+    };
+  });
+
+  // ── Budget Rollover ─────────────────────────────────────
+
+  app.post('/ai-budgets/policies/:id/rollover', async req => {
+    const access = requireAdmin(req);
+    const { id } = req.params as { id: string };
+    const policy = await repo.getPolicy(id, access.productId);
+
+    const now = new Date();
+    const currentPeriodStart = toIsoDayBoundary(periodStart(now, policy.period));
+
+    // Calculate previous period
+    const prev = new Date(now);
+    if (policy.period === 'monthly') {
+      prev.setUTCMonth(prev.getUTCMonth() - 1);
+    } else {
+      prev.setUTCDate(prev.getUTCDate() - 1);
+    }
+    const prevPeriodStart = toIsoDayBoundary(periodStart(prev, policy.period));
+
+    // Get spend from previous period
+    const prevEntries = await repo.listSpendEntries(access.productId, {
+      policyId: id,
+      since: prevPeriodStart,
+    });
+    // Only count entries in previous period (before current period)
+    const prevPeriodEntries = prevEntries.filter(e => e.recordedAt < currentPeriodStart);
+    const spentUsd = prevPeriodEntries.reduce((sum, e) => sum + e.costUsd, 0);
+    const remainingUsd = Math.max(0, policy.budgetUsd - spentUsd);
+    const rolledOverUsd = remainingUsd; // Full rollover — could add a cap later
+
+    const rollover: BudgetRolloverDoc = {
+      id: `airollover_${randomUUID()}`,
+      productId: access.productId,
+      policyId: id,
+      fromPeriod: prevPeriodStart,
+      toPeriod: currentPeriodStart,
+      spentUsd,
+      budgetUsd: policy.budgetUsd,
+      remainingUsd,
+      rolledOverUsd,
+      createdAt: now.toISOString(),
+    };
+
+    const saved = await repo.createRollover(rollover);
+
+    // Temporarily increase budget for current period
+    await repo.updatePolicy(id, access.productId, {
+      budgetUsd: policy.budgetUsd + rolledOverUsd,
+      metadata: {
+        ...(policy.metadata ?? {}),
+        lastRollover: saved.id,
+        originalBudgetUsd: policy.budgetUsd,
+      },
+    });
+
+    return {
+      rollover: saved,
+      newBudgetUsd: policy.budgetUsd + rolledOverUsd,
+    };
+  });
+
+  app.get('/ai-budgets/policies/:id/rollovers', async req => {
+    const access = requireAdmin(req);
+    const { id } = req.params as { id: string };
+    return repo.listRollovers(access.productId, id);
+  });
+
+  // ── Budget Enforcement Check ────────────────────────────
+  // Lightweight endpoint for pre-flight budget checks (no spend recorded)
+
+  app.post('/ai-budgets/check', async req => {
+    const access = requireAdmin(req);
+    const body = req.body as {
+      scopeType: string;
+      scopeId: string;
+      model?: string;
+      estimatedCostUsd: number;
+    };
+
+    if (!body.scopeType || !body.scopeId || body.estimatedCostUsd === undefined) {
+      validationError('scopeType, scopeId, and estimatedCostUsd are required');
+    }
+
+    const policies = await repo.listPolicies(access.productId, {
+      scopeType: body.scopeType as 'product' | 'agent' | 'org' | 'workspace',
+      scopeId: body.scopeId,
+      status: 'active',
+      limit: 100,
+    });
+
+    const now = new Date();
+    let verdict: 'allow' | 'warn' | 'block' = 'allow';
+    const reasons: string[] = [];
+
+    for (const policy of policies) {
+      // Model allowlist check
+      if (body.model && policy.modelAllowlist.length > 0) {
+        if (!policy.modelAllowlist.includes(body.model)) {
+          verdict = 'block';
+          reasons.push(`Model '${body.model}' not in allowlist for '${policy.name}'`);
+          continue;
+        }
+      }
+
+      const since = toIsoDayBoundary(periodStart(now, policy.period));
+      const entries = await repo.listSpendEntries(access.productId, {
+        policyId: policy.id,
+        since,
+      });
+      const currentSpend = entries.reduce((sum, e) => sum + e.costUsd, 0);
+      const projectedSpend = currentSpend + body.estimatedCostUsd;
+      const percentUsed = policy.budgetUsd > 0 ? projectedSpend / policy.budgetUsd : 0;
+
+      if (percentUsed >= policy.hardThreshold) {
+        verdict = 'block';
+        reasons.push(
+          `Would exceed hard threshold (${Math.round(percentUsed * 100)}%) for '${policy.name}'`
+        );
+      } else if (percentUsed >= policy.softThreshold && verdict !== 'block') {
+        verdict = 'warn';
+        reasons.push(
+          `Would exceed soft threshold (${Math.round(percentUsed * 100)}%) for '${policy.name}'`
+        );
+      }
+    }
+
+    return {
+      verdict,
+      reasons,
+      policiesEvaluated: policies.length,
+    };
+  });
 }
diff --git a/services/platform-service/src/modules/ai-budgets/types.ts b/services/platform-service/src/modules/ai-budgets/types.ts
index 6fa77478..c0490ee6 100644
--- a/services/platform-service/src/modules/ai-budgets/types.ts
+++ b/services/platform-service/src/modules/ai-budgets/types.ts
@@ -1,6 +1,6 @@
 import { z } from 'zod';
 
-export const BudgetScopeTypeSchema = z.enum(['product', 'agent']);
+export const BudgetScopeTypeSchema = z.enum(['product', 'agent', 'org', 'workspace']);
 export const BudgetPolicyStatusSchema = z.enum(['active', 'paused', 'archived']);
 export const BudgetPeriodSchema = z.enum(['daily', 'monthly']);
 export const BudgetAlertSeveritySchema = z.enum(['warn', 'block']);
@@ -122,3 +122,36 @@ export const ListBudgetAlertsQuerySchema = z.object({
 
 export type ListBudgetPoliciesQuery = z.infer<typeof ListBudgetPoliciesQuerySchema>;
 export type ListBudgetAlertsQuery = z.infer<typeof ListBudgetAlertsQuerySchema>;
+
+// ── Cost Dashboard ──────────────────────────────────────────
+
+export const CostDashboardQuerySchema = z.object({
+  scopeType: BudgetScopeTypeSchema.optional(),
+  scopeId: z.string().optional(),
+  since: z.string().optional(),
+  until: z.string().optional(),
+  groupBy: z.enum(['model', 'agent', 'day', 'scope']).default('model'),
+  limit: z.coerce.number().min(1).max(500).default(100),
+});
+
+export type CostDashboardQuery = z.infer<typeof CostDashboardQuerySchema>;
+
+// ── Budget Rollover ─────────────────────────────────────────
+
+export const BudgetRolloverSchema = z.object({
+  id: z.string().min(1),
+  productId: z.string().min(1),
+  policyId: z.string().min(1),
+  fromPeriod: z.string().min(1),
+  toPeriod: z.string().min(1),
+  spentUsd: z.number().min(0),
+  budgetUsd: z.number().min(0),
+  remainingUsd: z.number(),
+  rolledOverUsd: z.number().min(0),
+  createdAt: z.string(),
+});
+
+export type BudgetRolloverDoc = z.infer<typeof BudgetRolloverSchema> & {
+  _ts?: number;
+  _etag?: string;
+};