diff --git a/server/src/__tests__/costs-service.test.ts b/server/src/__tests__/costs-service.test.ts
index f642e566..517ada52 100644
--- a/server/src/__tests__/costs-service.test.ts
+++ b/server/src/__tests__/costs-service.test.ts
@@ -32,6 +32,7 @@ function makeDb(overrides: Record<string, unknown> = {}) {
 
 const mockCompanyService = vi.hoisted(() => ({
   getById: vi.fn(),
+  update: vi.fn(),
 }));
 const mockAgentService = vi.hoisted(() => ({
   getById: vi.fn(),
@@ -98,8 +99,34 @@ function createApp() {
   return app;
 }
 
+function createAppWithActor(actor: any) {
+  const app = express();
+  app.use(express.json());
+  app.use((req, _res, next) => {
+    req.actor = actor;
+    next();
+  });
+  app.use("/api", costRoutes(makeDb() as any));
+  app.use(errorHandler);
+  return app;
+}
+
 beforeEach(() => {
   vi.clearAllMocks();
+  mockCompanyService.update.mockResolvedValue({
+    id: "company-1",
+    name: "Paperclip",
+    budgetMonthlyCents: 100,
+    spentMonthlyCents: 0,
+  });
+  mockAgentService.update.mockResolvedValue({
+    id: "agent-1",
+    companyId: "company-1",
+    name: "Budget Agent",
+    budgetMonthlyCents: 100,
+    spentMonthlyCents: 0,
+  });
+  mockBudgetService.upsertPolicy.mockResolvedValue(undefined);
 });
 
 describe("cost routes", () => {
@@ -155,4 +182,45 @@ describe("cost routes", () => {
     expect(res.status).toBe(200);
     expect(mockFinanceService.list).toHaveBeenCalledWith("company-1", undefined, 25);
   });
+
+  it("rejects company budget updates for board users outside the company", async () => {
+    const app = createAppWithActor({
+      type: "board",
+      userId: "board-user",
+      source: "session",
+      isInstanceAdmin: false,
+      companyIds: ["company-2"],
+    });
+
+    const res = await request(app)
+      .patch("/api/companies/company-1/budgets")
+      .send({ budgetMonthlyCents: 2500 });
+
+    expect(res.status).toBe(403);
+    expect(mockCompanyService.update).not.toHaveBeenCalled();
+  });
+
+  it("rejects agent budget updates for board users outside the agent company", async () => {
+    mockAgentService.getById.mockResolvedValue({
+      id: "agent-1",
+      companyId: "company-1",
+      name: "Budget Agent",
+      budgetMonthlyCents: 100,
+      spentMonthlyCents: 0,
+    });
+    const app = createAppWithActor({
+      type: "board",
+      userId: "board-user",
+      source: "session",
+      isInstanceAdmin: false,
+      companyIds: ["company-2"],
+    });
+
+    const res = await request(app)
+      .patch("/api/agents/agent-1/budgets")
+      .send({ budgetMonthlyCents: 2500 });
+
+    expect(res.status).toBe(403);
+    expect(mockAgentService.update).not.toHaveBeenCalled();
+  });
 });
diff --git a/server/src/__tests__/monthly-spend-service.test.ts b/server/src/__tests__/monthly-spend-service.test.ts
new file mode 100644
index 00000000..97b213af
--- /dev/null
+++ b/server/src/__tests__/monthly-spend-service.test.ts
@@ -0,0 +1,90 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { companyService } from "../services/companies.ts";
+import { agentService } from "../services/agents.ts";
+
+function createSelectSequenceDb(results: unknown[]) {
+  const pending = [...results];
+  const chain = {
+    from: vi.fn(() => chain),
+    where: vi.fn(() => chain),
+    leftJoin: vi.fn(() => chain),
+    groupBy: vi.fn(() => chain),
+    then: vi.fn((resolve: (value: unknown[]) => unknown) => Promise.resolve(resolve(pending.shift() ?? []))),
+  };
+
+  return {
+    db: {
+      select: vi.fn(() => chain),
+    },
+  };
+}
+
+describe("monthly spend hydration", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("recomputes company spentMonthlyCents from the current utc month instead of returning stale stored values", async () => {
+    const dbStub = createSelectSequenceDb([
+      [{
+        id: "company-1",
+        name: "Paperclip",
+        description: null,
+        status: "active",
+        issuePrefix: "PAP",
+        issueCounter: 1,
+        budgetMonthlyCents: 5000,
+        spentMonthlyCents: 999999,
+        requireBoardApprovalForNewAgents: false,
+        brandColor: null,
+        logoAssetId: null,
+        createdAt: new Date(),
+        updatedAt: new Date(),
+      }],
+      [{
+        companyId: "company-1",
+        spentMonthlyCents: 420,
+      }],
+    ]);
+
+    const companies = companyService(dbStub.db as any);
+    const [company] = await companies.list();
+
+    expect(company.spentMonthlyCents).toBe(420);
+  });
+
+  it("recomputes agent spentMonthlyCents from the current utc month instead of returning stale stored values", async () => {
+    const dbStub = createSelectSequenceDb([
+      [{
+        id: "agent-1",
+        companyId: "company-1",
+        name: "Budget Agent",
+        role: "general",
+        title: null,
+        reportsTo: null,
+        capabilities: null,
+        adapterType: "claude-local",
+        adapterConfig: {},
+        runtimeConfig: {},
+        budgetMonthlyCents: 5000,
+        spentMonthlyCents: 999999,
+        metadata: null,
+        permissions: null,
+        status: "idle",
+        pauseReason: null,
+        pausedAt: null,
+        createdAt: new Date(),
+        updatedAt: new Date(),
+      }],
+      [{
+        agentId: "agent-1",
+        spentMonthlyCents: 175,
+      }],
+    ]);
+
+    const agents = agentService(dbStub.db as any);
+    const agent = await agents.getById("agent-1");
+
+    expect(agent?.spentMonthlyCents).toBe(175);
+  });
+});
diff --git a/server/src/routes/costs.ts b/server/src/routes/costs.ts
index 59374884..82925bd7 100644
--- a/server/src/routes/costs.ts
+++ b/server/src/routes/costs.ts
@@ -250,6 +250,7 @@ export function costRoutes(db: Db) {
   router.patch("/companies/:companyId/budgets", validate(updateBudgetSchema), async (req, res) => {
     assertBoard(req);
     const companyId = req.params.companyId as string;
+    assertCompanyAccess(req, companyId);
     const company = await companies.update(companyId, { budgetMonthlyCents: req.body.budgetMonthlyCents });
     if (!company) {
       res.status(404).json({ error: "Company not found" });
@@ -288,6 +289,8 @@ export function costRoutes(db: Db) {
       return;
     }
 
+    assertCompanyAccess(req, agent.companyId);
+
     if (req.actor.type === "agent") {
       if (req.actor.agentId !== agentId) {
         res.status(403).json({ error: "Agent can only change its own budget" });
diff --git a/server/src/services/agents.ts b/server/src/services/agents.ts
index 4daa1dd9..17d2e46d 100644
--- a/server/src/services/agents.ts
+++ b/server/src/services/agents.ts
@@ -1,5 +1,5 @@
 import { createHash, randomBytes } from "node:crypto";
-import { and, desc, eq, inArray, ne } from "drizzle-orm";
+import { and, desc, eq, gte, inArray, lt, ne, sql } from "drizzle-orm";
 import type { Db } from "@paperclipai/db";
 import {
   agents,
@@ -8,6 +8,7 @@ import {
   agentRuntimeState,
   agentTaskSessions,
   agentWakeupRequests,
+  costEvents,
   heartbeatRunEvents,
   heartbeatRuns,
 } from "@paperclipai/db";
@@ -182,6 +183,15 @@ export function deduplicateAgentName(
 }
 
 export function agentService(db: Db) {
+  function currentUtcMonthWindow(now = new Date()) {
+    const year = now.getUTCFullYear();
+    const month = now.getUTCMonth();
+    return {
+      start: new Date(Date.UTC(year, month, 1, 0, 0, 0, 0)),
+      end: new Date(Date.UTC(year, month + 1, 1, 0, 0, 0, 0)),
+    };
+  }
+
   function withUrlKey<T extends { id: string; name: string }>(row: T) {
     return {
       ...row,
@@ -196,13 +206,47 @@ export function agentService(db: Db) {
     });
   }
 
+  async function getMonthlySpendByAgentIds(companyId: string, agentIds: string[]) {
+    if (agentIds.length === 0) return new Map<string, number>();
+    const { start, end } = currentUtcMonthWindow();
+    const rows = await db
+      .select({
+        agentId: costEvents.agentId,
+        spentMonthlyCents: sql<number>`coalesce(sum(${costEvents.costCents}), 0)::int`,
+      })
+      .from(costEvents)
+      .where(
+        and(
+          eq(costEvents.companyId, companyId),
+          inArray(costEvents.agentId, agentIds),
+          gte(costEvents.occurredAt, start),
+          lt(costEvents.occurredAt, end),
+        ),
+      )
+      .groupBy(costEvents.agentId);
+    return new Map(rows.map((row) => [row.agentId, Number(row.spentMonthlyCents ?? 0)]));
+  }
+
+  async function hydrateAgentSpend<T extends { id: string; companyId: string; spentMonthlyCents: number }>(rows: T[]) {
+    const agentIds = rows.map((row) => row.id);
+    const companyId = rows[0]?.companyId;
+    if (!companyId || agentIds.length === 0) return rows;
+    const spendByAgentId = await getMonthlySpendByAgentIds(companyId, agentIds);
+    return rows.map((row) => ({
+      ...row,
+      spentMonthlyCents: spendByAgentId.get(row.id) ?? 0,
+    }));
+  }
+
   async function getById(id: string) {
     const row = await db
       .select()
       .from(agents)
       .where(eq(agents.id, id))
       .then((rows) => rows[0] ?? null);
-    return row ? normalizeAgentRow(row) : null;
+    if (!row) return null;
+    const [hydrated] = await hydrateAgentSpend([row]);
+    return normalizeAgentRow(hydrated);
   }
 
   async function ensureManager(companyId: string, managerId: string) {
@@ -331,7 +375,8 @@ export function agentService(db: Db) {
         conditions.push(ne(agents.status, "terminated"));
       }
       const rows = await db.select().from(agents).where(and(...conditions));
-      return rows.map(normalizeAgentRow);
+      const hydrated = await hydrateAgentSpend(rows);
+      return hydrated.map(normalizeAgentRow);
     },
 
     getById,
diff --git a/server/src/services/budgets.ts b/server/src/services/budgets.ts
index bc09673e..577635a3 100644
--- a/server/src/services/budgets.ts
+++ b/server/src/services/budgets.ts
@@ -1,4 +1,4 @@
-import { and, desc, eq, gte, inArray, lt, sql } from "drizzle-orm";
+import { and, desc, eq, gte, inArray, lt, ne, sql } from "drizzle-orm";
 import type { Db } from "@paperclipai/db";
 import {
   agents,
@@ -360,6 +360,7 @@ export function budgetService(db: Db, hooks: BudgetServiceHooks = {}) {
           eq(budgetIncidents.policyId, policy.id),
           eq(budgetIncidents.windowStart, start),
           eq(budgetIncidents.thresholdType, thresholdType),
+          ne(budgetIncidents.status, "dismissed"),
         ),
       )
       .then((rows) => rows[0] ?? null);
diff --git a/server/src/services/companies.ts b/server/src/services/companies.ts
index 7fafb093..893bea9e 100644
--- a/server/src/services/companies.ts
+++ b/server/src/services/companies.ts
@@ -1,4 +1,4 @@
-import { eq, count } from "drizzle-orm";
+import { and, count, eq, gte, inArray, lt, sql } from "drizzle-orm";
 import type { Db } from "@paperclipai/db";
 import {
   companies,
@@ -54,6 +54,49 @@ export function companyService(db: Db) {
     };
   }
 
+  function currentUtcMonthWindow(now = new Date()) {
+    const year = now.getUTCFullYear();
+    const month = now.getUTCMonth();
+    return {
+      start: new Date(Date.UTC(year, month, 1, 0, 0, 0, 0)),
+      end: new Date(Date.UTC(year, month + 1, 1, 0, 0, 0, 0)),
+    };
+  }
+
+  async function getMonthlySpendByCompanyIds(
+    companyIds: string[],
+    database: Pick<Db, "select"> = db,
+  ) {
+    if (companyIds.length === 0) return new Map<string, number>();
+    const { start, end } = currentUtcMonthWindow();
+    const rows = await database
+      .select({
+        companyId: costEvents.companyId,
+        spentMonthlyCents: sql<number>`coalesce(sum(${costEvents.costCents}), 0)::int`,
+      })
+      .from(costEvents)
+      .where(
+        and(
+          inArray(costEvents.companyId, companyIds),
+          gte(costEvents.occurredAt, start),
+          lt(costEvents.occurredAt, end),
+        ),
+      )
+      .groupBy(costEvents.companyId);
+    return new Map(rows.map((row) => [row.companyId, Number(row.spentMonthlyCents ?? 0)]));
+  }
+
+  async function hydrateCompanySpend<T extends { id: string; spentMonthlyCents: number }>(
+    rows: T[],
+    database: Pick<Db, "select"> = db,
+  ) {
+    const spendByCompanyId = await getMonthlySpendByCompanyIds(rows.map((row) => row.id), database);
+    return rows.map((row) => ({
+      ...row,
+      spentMonthlyCents: spendByCompanyId.get(row.id) ?? 0,
+    }));
+  }
+
   function getCompanyQuery(database: Pick<Db, "select">) {
     return database
       .select(companySelection)
@@ -104,13 +147,20 @@ export function companyService(db: Db) {
   }
 
   return {
-    list: () =>
-      getCompanyQuery(db).then((rows) => rows.map((row) => enrichCompany(row))),
+    list: async () => {
+      const rows = await getCompanyQuery(db);
+      const hydrated = await hydrateCompanySpend(rows);
+      return hydrated.map((row) => enrichCompany(row));
+    },
 
-    getById: (id: string) =>
-      getCompanyQuery(db)
+    getById: async (id: string) => {
+      const row = await getCompanyQuery(db)
         .where(eq(companies.id, id))
-        .then((rows) => (rows[0] ? enrichCompany(rows[0]) : null)),
+        .then((rows) => rows[0] ?? null);
+      if (!row) return null;
+      const [hydrated] = await hydrateCompanySpend([row], db);
+      return enrichCompany(hydrated);
+    },
 
     create: async (data: typeof companies.$inferInsert) => {
       const created = await createCompanyWithUniquePrefix(data);
@@ -118,7 +168,8 @@ export function companyService(db: Db) {
         .where(eq(companies.id, created.id))
         .then((rows) => rows[0] ?? null);
       if (!row) throw notFound("Company not found after creation");
-      return enrichCompany(row);
+      const [hydrated] = await hydrateCompanySpend([row], db);
+      return enrichCompany(hydrated);
     },
 
     update: (
@@ -175,10 +226,12 @@ export function companyService(db: Db) {
           await tx.delete(assets).where(eq(assets.id, existing.logoAssetId));
         }
 
-        return enrichCompany({
+        const [hydrated] = await hydrateCompanySpend([{
           ...updated,
           logoAssetId: logoAssetId === undefined ? existing.logoAssetId : logoAssetId,
-        });
+        }], tx);
+
+        return enrichCompany(hydrated);
       }),
 
     archive: (id: string) =>
@@ -193,7 +246,9 @@ export function companyService(db: Db) {
         const row = await getCompanyQuery(tx)
           .where(eq(companies.id, id))
           .then((rows) => rows[0] ?? null);
-        return row ? enrichCompany(row) : null;
+        if (!row) return null;
+        const [hydrated] = await hydrateCompanySpend([row], tx);
+        return enrichCompany(hydrated);
       }),
 
     remove: (id: string) =>
diff --git a/server/src/services/costs.ts b/server/src/services/costs.ts
index aa80e3a8..76a90f2d 100644
--- a/server/src/services/costs.ts
+++ b/server/src/services/costs.ts
@@ -1,4 +1,4 @@
-import { and, desc, eq, gte, isNotNull, lte, sql } from "drizzle-orm";
+import { and, desc, eq, gte, isNotNull, lt, lte, sql } from "drizzle-orm";
 import type { Db } from "@paperclipai/db";
 import { activityLog, agents, companies, costEvents, issues, projects } from "@paperclipai/db";
 import { notFound, unprocessable } from "../errors.js";
@@ -12,6 +12,37 @@ export interface CostDateRange {
 const METERED_BILLING_TYPE = "metered_api";
 const SUBSCRIPTION_BILLING_TYPES = ["subscription_included", "subscription_overage"] as const;
 
+function currentUtcMonthWindow(now = new Date()) {
+  const year = now.getUTCFullYear();
+  const month = now.getUTCMonth();
+  return {
+    start: new Date(Date.UTC(year, month, 1, 0, 0, 0, 0)),
+    end: new Date(Date.UTC(year, month + 1, 1, 0, 0, 0, 0)),
+  };
+}
+
+async function getMonthlySpendTotal(
+  db: Db,
+  scope: { companyId: string; agentId?: string | null },
+) {
+  const { start, end } = currentUtcMonthWindow();
+  const conditions = [
+    eq(costEvents.companyId, scope.companyId),
+    gte(costEvents.occurredAt, start),
+    lt(costEvents.occurredAt, end),
+  ];
+  if (scope.agentId) {
+    conditions.push(eq(costEvents.agentId, scope.agentId));
+  }
+  const [row] = await db
+    .select({
+      total: sql<number>`coalesce(sum(${costEvents.costCents}), 0)::int`,
+    })
+    .from(costEvents)
+    .where(and(...conditions));
+  return Number(row?.total ?? 0);
+}
+
 export function costService(db: Db, budgetHooks: BudgetServiceHooks = {}) {
   const budgets = budgetService(db, budgetHooks);
   return {
@@ -39,10 +70,15 @@ export function costService(db: Db, budgetHooks: BudgetServiceHooks = {}) {
         .returning()
         .then((rows) => rows[0]);
 
+      const [agentMonthSpend, companyMonthSpend] = await Promise.all([
+        getMonthlySpendTotal(db, { companyId, agentId: event.agentId }),
+        getMonthlySpendTotal(db, { companyId }),
+      ]);
+
       await db
         .update(agents)
         .set({
-          spentMonthlyCents: sql`${agents.spentMonthlyCents} + ${event.costCents}`,
+          spentMonthlyCents: agentMonthSpend,
           updatedAt: new Date(),
         })
         .where(eq(agents.id, event.agentId));
@@ -50,7 +86,7 @@ export function costService(db: Db, budgetHooks: BudgetServiceHooks = {}) {
       await db
         .update(companies)
         .set({
-          spentMonthlyCents: sql`${companies.spentMonthlyCents} + ${event.costCents}`,
+          spentMonthlyCents: companyMonthSpend,
           updatedAt: new Date(),
         })
         .where(eq(companies.id, companyId));