diff --git a/apps/orchestrator/src/app.module.ts b/apps/orchestrator/src/app.module.ts
index 20eb134..55b7e24 100644
--- a/apps/orchestrator/src/app.module.ts
+++ b/apps/orchestrator/src/app.module.ts
@@ -4,6 +4,7 @@ import { BullModule } from "@nestjs/bullmq";
 import { HealthModule } from "./api/health/health.module";
 import { AgentsModule } from "./api/agents/agents.module";
 import { CoordinatorModule } from "./coordinator/coordinator.module";
+import { BudgetModule } from "./budget/budget.module";
 import { orchestratorConfig } from "./config/orchestrator.config";
 
 @Module({
@@ -21,6 +22,7 @@ import { orchestratorConfig } from "./config/orchestrator.config";
     HealthModule,
     AgentsModule,
     CoordinatorModule,
+    BudgetModule,
   ],
 })
 export class AppModule {}
diff --git a/apps/orchestrator/src/budget/budget.module.ts b/apps/orchestrator/src/budget/budget.module.ts
new file mode 100644
index 0000000..14190e3
--- /dev/null
+++ b/apps/orchestrator/src/budget/budget.module.ts
@@ -0,0 +1,10 @@
+import { Module } from "@nestjs/common";
+import { ConfigModule } from "@nestjs/config";
+import { BudgetService } from "./budget.service";
+
+@Module({
+  imports: [ConfigModule],
+  providers: [BudgetService],
+  exports: [BudgetService],
+})
+export class BudgetModule {}
diff --git a/apps/orchestrator/src/budget/budget.service.spec.ts b/apps/orchestrator/src/budget/budget.service.spec.ts
new file mode 100644
index 0000000..da742c0
--- /dev/null
+++ b/apps/orchestrator/src/budget/budget.service.spec.ts
@@ -0,0 +1,416 @@
+/**
+ * BudgetService Unit Tests
+ *
+ * Tests usage budget tracking, enforcement, and reporting.
+ * Covers issue #329 (ORCH-135) including security hardening.
+ */
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { BudgetService } from "./budget.service";
+import { ConfigService } from "@nestjs/config";
+
+describe("BudgetService", () => {
+  let service: BudgetService;
+
+  const mockConfigService = {
+    get: vi.fn((_key: string, _defaultValue?: unknown) => undefined),
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    service = new BudgetService(mockConfigService as unknown as ConfigService);
+  });
+
+  describe("initialization", () => {
+    it("should initialize with default budget values", () => {
+      const budget = service.getBudget();
+      expect(budget.dailyTokenLimit).toBe(10_000_000);
+      expect(budget.perAgentTokenLimit).toBe(2_000_000);
+      expect(budget.maxConcurrentAgents).toBe(10);
+      expect(budget.maxTaskDurationMinutes).toBe(120);
+      expect(budget.enforceHardLimits).toBe(false);
+    });
+
+    it("should use config values when provided", () => {
+      const customConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": 5_000_000,
+            "orchestrator.budget.perAgentTokenLimit": 1_000_000,
+            "orchestrator.budget.maxConcurrentAgents": 5,
+            "orchestrator.budget.maxTaskDurationMinutes": 60,
+            "orchestrator.budget.enforceHardLimits": true,
+          };
+          return config[key];
+        }),
+      };
+
+      const customService = new BudgetService(customConfig as unknown as ConfigService);
+      const budget = customService.getBudget();
+
+      expect(budget.dailyTokenLimit).toBe(5_000_000);
+      expect(budget.perAgentTokenLimit).toBe(1_000_000);
+      expect(budget.maxConcurrentAgents).toBe(5);
+      expect(budget.maxTaskDurationMinutes).toBe(60);
+      expect(budget.enforceHardLimits).toBe(true);
+    });
+
+    it("should clamp negative config values to defaults", () => {
+      const badConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": -100,
+            "orchestrator.budget.perAgentTokenLimit": -50,
+            "orchestrator.budget.maxConcurrentAgents": -1,
+            "orchestrator.budget.maxTaskDurationMinutes": 0,
+          };
+          return config[key];
+        }),
+      };
+
+      const badService = new BudgetService(badConfig as unknown as ConfigService);
+      const budget = badService.getBudget();
+
+      expect(budget.dailyTokenLimit).toBe(10_000_000);
+      expect(budget.perAgentTokenLimit).toBe(2_000_000);
+      expect(budget.maxConcurrentAgents).toBe(10);
+      expect(budget.maxTaskDurationMinutes).toBe(120);
+    });
+
+    it("should clamp NaN config values to defaults", () => {
+      const nanConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": NaN,
+            "orchestrator.budget.maxConcurrentAgents": Infinity,
+          };
+          return config[key];
+        }),
+      };
+
+      const nanService = new BudgetService(nanConfig as unknown as ConfigService);
+      const budget = nanService.getBudget();
+
+      expect(budget.dailyTokenLimit).toBe(10_000_000);
+      expect(budget.maxConcurrentAgents).toBe(10);
+    });
+  });
+
+  describe("recordUsage", () => {
+    it("should record token usage", () => {
+      service.recordUsage("agent-1", "task-1", 1000, 500);
+
+      const summary = service.getUsageSummary();
+      expect(summary.dailyTokensUsed).toBe(1500);
+    });
+
+    it("should accumulate usage across multiple records", () => {
+      service.recordUsage("agent-1", "task-1", 1000, 500);
+      service.recordUsage("agent-1", "task-1", 2000, 1000);
+
+      const summary = service.getUsageSummary();
+      expect(summary.dailyTokensUsed).toBe(4500);
+    });
+
+    it("should track usage per agent", () => {
+      service.recordUsage("agent-1", "task-1", 1000, 500);
+      service.recordUsage("agent-2", "task-2", 3000, 1500);
+
+      const summary = service.getUsageSummary();
+      expect(summary.agentUsage).toHaveLength(2);
+
+      const agent1 = summary.agentUsage.find((a) => a.agentId === "agent-1");
+      const agent2 = summary.agentUsage.find((a) => a.agentId === "agent-2");
+
+      expect(agent1?.totalTokens).toBe(1500);
+      expect(agent2?.totalTokens).toBe(4500);
+    });
+
+    it("should clamp negative token values to 0", () => {
+      service.recordUsage("agent-1", "task-1", -500, -200);
+
+      const summary = service.getUsageSummary();
+      expect(summary.dailyTokensUsed).toBe(0);
+    });
+
+    it("should clamp NaN token values to 0", () => {
+      service.recordUsage("agent-1", "task-1", NaN, NaN);
+
+      const summary = service.getUsageSummary();
+      expect(summary.dailyTokensUsed).toBe(0);
+    });
+
+    it("should clamp Infinity token values to 0", () => {
+      service.recordUsage("agent-1", "task-1", Infinity, -Infinity);
+
+      const summary = service.getUsageSummary();
+      expect(summary.dailyTokensUsed).toBe(0);
+    });
+
+    it("should skip recording when agentId is empty", () => {
+      service.recordUsage("", "task-1", 1000, 500);
+
+      const summary = service.getUsageSummary();
+      expect(summary.dailyTokensUsed).toBe(0);
+      expect(summary.agentUsage).toHaveLength(0);
+    });
+
+    it("should skip recording when taskId is empty", () => {
+      service.recordUsage("agent-1", "", 1000, 500);
+
+      const summary = service.getUsageSummary();
+      expect(summary.dailyTokensUsed).toBe(0);
+    });
+  });
+
+  describe("canSpawnAgent", () => {
+    it("should allow spawning when under limits", () => {
+      const result = service.canSpawnAgent();
+      expect(result.allowed).toBe(true);
+    });
+
+    it("should block spawning when at max concurrent agents", () => {
+      for (let i = 0; i < 10; i++) {
+        service.agentStarted(`agent-${String(i)}`);
+      }
+
+      const result = service.canSpawnAgent();
+      expect(result.allowed).toBe(false);
+      expect(result.reason).toContain("Maximum concurrent agents");
+    });
+
+    it("should allow spawning after agent stops", () => {
+      for (let i = 0; i < 10; i++) {
+        service.agentStarted(`agent-${String(i)}`);
+      }
+
+      expect(service.canSpawnAgent().allowed).toBe(false);
+
+      service.agentStopped("agent-0");
+
+      expect(service.canSpawnAgent().allowed).toBe(true);
+    });
+
+    it("should block spawning when daily budget exceeded with hard limits", () => {
+      const strictConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": 1000,
+            "orchestrator.budget.enforceHardLimits": true,
+          };
+          return config[key];
+        }),
+      };
+
+      const strictService = new BudgetService(strictConfig as unknown as ConfigService);
+      strictService.recordUsage("agent-1", "task-1", 800, 300);
+
+      const result = strictService.canSpawnAgent();
+      expect(result.allowed).toBe(false);
+      expect(result.reason).toContain("Daily token budget exceeded");
+    });
+
+    it("should allow spawning when over budget without hard limits", () => {
+      service.recordUsage("agent-1", "task-1", 5_000_000, 5_000_000);
+
+      const result = service.canSpawnAgent();
+      expect(result.allowed).toBe(true);
+    });
+  });
+
+  describe("trySpawnAgent", () => {
+    it("should atomically check and reserve slot", () => {
+      const result = service.trySpawnAgent("agent-1");
+      expect(result.allowed).toBe(true);
+
+      const summary = service.getUsageSummary();
+      expect(summary.activeAgents).toBe(1);
+    });
+
+    it("should block when at max concurrent and not reserve slot", () => {
+      for (let i = 0; i < 10; i++) {
+        service.trySpawnAgent(`agent-${String(i)}`);
+      }
+
+      const result = service.trySpawnAgent("agent-11");
+      expect(result.allowed).toBe(false);
+      expect(result.reason).toContain("Maximum concurrent agents");
+
+      const summary = service.getUsageSummary();
+      expect(summary.activeAgents).toBe(10);
+    });
+
+    it("should reject empty agent ID", () => {
+      const result = service.trySpawnAgent("");
+      expect(result.allowed).toBe(false);
+      expect(result.reason).toContain("Agent ID is required");
+    });
+
+    it("should not double-count same agent ID", () => {
+      service.trySpawnAgent("agent-1");
+      service.trySpawnAgent("agent-1");
+
+      const summary = service.getUsageSummary();
+      expect(summary.activeAgents).toBe(1);
+    });
+  });
+
+  describe("isAgentOverBudget", () => {
+    it("should return false when agent is within budget", () => {
+      service.recordUsage("agent-1", "task-1", 100_000, 50_000);
+
+      const result = service.isAgentOverBudget("agent-1");
+      expect(result.overBudget).toBe(false);
+      expect(result.totalTokens).toBe(150_000);
+    });
+
+    it("should return true when agent exceeds per-agent limit", () => {
+      service.recordUsage("agent-1", "task-1", 1_000_000, 1_000_000);
+
+      const result = service.isAgentOverBudget("agent-1");
+      expect(result.overBudget).toBe(true);
+      expect(result.totalTokens).toBe(2_000_000);
+    });
+
+    it("should return false for unknown agent", () => {
+      const result = service.isAgentOverBudget("non-existent");
+      expect(result.overBudget).toBe(false);
+      expect(result.totalTokens).toBe(0);
+    });
+  });
+
+  describe("agentStarted / agentStopped", () => {
+    it("should track active agent count by ID", () => {
+      service.agentStarted("agent-1");
+      service.agentStarted("agent-2");
+      service.agentStarted("agent-3");
+
+      const summary = service.getUsageSummary();
+      expect(summary.activeAgents).toBe(3);
+    });
+
+    it("should decrement active count on stop", () => {
+      service.agentStarted("agent-1");
+      service.agentStarted("agent-2");
+      service.agentStopped("agent-1");
+
+      const summary = service.getUsageSummary();
+      expect(summary.activeAgents).toBe(1);
+    });
+
+    it("should handle stopping non-existent agent gracefully", () => {
+      service.agentStopped("non-existent");
+
+      const summary = service.getUsageSummary();
+      expect(summary.activeAgents).toBe(0);
+    });
+
+    it("should not double-count same agent ID on start", () => {
+      service.agentStarted("agent-1");
+      service.agentStarted("agent-1");
+
+      const summary = service.getUsageSummary();
+      expect(summary.activeAgents).toBe(1);
+    });
+  });
+
+  describe("getUsageSummary", () => {
+    it("should return complete summary with no usage", () => {
+      const summary = service.getUsageSummary();
+
+      expect(summary.dailyTokensUsed).toBe(0);
+      expect(summary.dailyTokenLimit).toBe(10_000_000);
+      expect(summary.dailyUsagePercent).toBe(0);
+      expect(summary.agentUsage).toHaveLength(0);
+      expect(summary.activeAgents).toBe(0);
+      expect(summary.maxConcurrentAgents).toBe(10);
+      expect(summary.budgetStatus).toBe("within_budget");
+    });
+
+    it("should calculate usage percentage correctly", () => {
+      const customConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": 10_000,
+          };
+          return config[key];
+        }),
+      };
+
+      const customService = new BudgetService(customConfig as unknown as ConfigService);
+      customService.recordUsage("agent-1", "task-1", 5000, 0);
+
+      const summary = customService.getUsageSummary();
+      expect(summary.dailyUsagePercent).toBe(50);
+    });
+
+    it("should report 'approaching_limit' at 80%", () => {
+      const customConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": 10_000,
+          };
+          return config[key];
+        }),
+      };
+
+      const customService = new BudgetService(customConfig as unknown as ConfigService);
+      customService.recordUsage("agent-1", "task-1", 8500, 0);
+
+      const summary = customService.getUsageSummary();
+      expect(summary.budgetStatus).toBe("approaching_limit");
+    });
+
+    it("should report 'at_limit' at 95%", () => {
+      const customConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": 10_000,
+          };
+          return config[key];
+        }),
+      };
+
+      const customService = new BudgetService(customConfig as unknown as ConfigService);
+      customService.recordUsage("agent-1", "task-1", 9600, 0);
+
+      const summary = customService.getUsageSummary();
+      expect(summary.budgetStatus).toBe("at_limit");
+    });
+
+    it("should report 'exceeded' over 100%", () => {
+      const customConfig = {
+        get: vi.fn((key: string) => {
+          const config: Record<string, unknown> = {
+            "orchestrator.budget.dailyTokenLimit": 10_000,
+          };
+          return config[key];
+        }),
+      };
+
+      const customService = new BudgetService(customConfig as unknown as ConfigService);
+      customService.recordUsage("agent-1", "task-1", 11_000, 0);
+
+      const summary = customService.getUsageSummary();
+      expect(summary.budgetStatus).toBe("exceeded");
+    });
+
+    it("should calculate per-agent usage percentage", () => {
+      service.recordUsage("agent-1", "task-1", 500_000, 500_000);
+
+      const summary = service.getUsageSummary();
+      const agent = summary.agentUsage.find((a) => a.agentId === "agent-1");
+
+      expect(agent?.usagePercent).toBe(50);
+    });
+  });
+
+  describe("getBudget", () => {
+    it("should return a copy of the budget", () => {
+      const budget1 = service.getBudget();
+      const budget2 = service.getBudget();
+
+      expect(budget1).toEqual(budget2);
+      expect(budget1).not.toBe(budget2);
+    });
+  });
+});
diff --git a/apps/orchestrator/src/budget/budget.service.ts b/apps/orchestrator/src/budget/budget.service.ts
new file mode 100644
index 0000000..7c8e82e
--- /dev/null
+++ b/apps/orchestrator/src/budget/budget.service.ts
@@ -0,0 +1,311 @@
+/**
+ * Usage Budget Management Service
+ *
+ * Tracks token usage per agent and enforces budget limits.
+ * Provides real-time usage summaries and budget status checks.
+ */
+import { Injectable, Logger } from "@nestjs/common";
+import { ConfigService } from "@nestjs/config";
+import type {
+  UsageBudget,
+  UsageRecord,
+  UsageSummary,
+  AgentUsageSummary,
+  BudgetStatus,
+} from "./budget.types";
+import { DEFAULT_BUDGET } from "./budget.types";
+
+/** Sanitize strings for safe log output */
+function sanitizeForLog(value: string): string {
+  return value.replace(/[\n\r\t]/g, "_").slice(0, 128);
+}
+
+@Injectable()
+export class BudgetService {
+  private readonly logger = new Logger(BudgetService.name);
+  private readonly budget: UsageBudget;
+  private records: UsageRecord[] = [];
+  private readonly activeAgents = new Set<string>();
+  private lastPurgeDate = "";
+
+  constructor(private readonly configService: ConfigService) {
+    this.budget = this.loadAndValidateConfig();
+
+    this.logger.log(
+      `BudgetService initialized: daily=${String(this.budget.dailyTokenLimit)} tokens, ` +
+        `perAgent=${String(this.budget.perAgentTokenLimit)} tokens, ` +
+        `maxConcurrent=${String(this.budget.maxConcurrentAgents)}`
+    );
+  }
+
+  /**
+   * Record token usage for an agent.
+   * Negative and NaN values are clamped to 0.
+   */
+  recordUsage(agentId: string, taskId: string, inputTokens: number, outputTokens: number): void {
+    if (!agentId || !taskId) {
+      this.logger.warn("recordUsage called with empty agentId or taskId — skipping");
+      return;
+    }
+
+    const safeInput = Math.max(0, Number.isFinite(inputTokens) ? inputTokens : 0);
+    const safeOutput = Math.max(0, Number.isFinite(outputTokens) ? outputTokens : 0);
+
+    this.purgeStaleRecords();
+
+    const record: UsageRecord = {
+      agentId,
+      taskId,
+      inputTokens: safeInput,
+      outputTokens: safeOutput,
+      timestamp: new Date(),
+    };
+
+    this.records.push(record);
+
+    this.logger.debug(
+      `Usage recorded: agent=${sanitizeForLog(agentId)} input=${String(safeInput)} output=${String(safeOutput)}`
+    );
+  }
+
+  /**
+   * Check if an agent can be spawned (concurrency and budget check).
+   * When allowed, atomically increments the active agent count.
+   */
+  trySpawnAgent(agentId: string): { allowed: boolean; reason?: string } {
+    if (!agentId) {
+      return { allowed: false, reason: "Agent ID is required" };
+    }
+
+    if (this.activeAgents.size >= this.budget.maxConcurrentAgents) {
+      return {
+        allowed: false,
+        reason: `Maximum concurrent agents reached (${String(this.budget.maxConcurrentAgents)})`,
+      };
+    }
+
+    const dailyUsed = this.getDailyTokensUsed();
+    if (this.budget.enforceHardLimits && dailyUsed >= this.budget.dailyTokenLimit) {
+      return {
+        allowed: false,
+        reason: `Daily token budget exceeded (${String(dailyUsed)}/${String(this.budget.dailyTokenLimit)})`,
+      };
+    }
+
+    this.activeAgents.add(agentId);
+    return { allowed: true };
+  }
+
+  /**
+   * Check if an agent can be spawned without reserving a slot.
+   */
+  canSpawnAgent(): { allowed: boolean; reason?: string } {
+    if (this.activeAgents.size >= this.budget.maxConcurrentAgents) {
+      return {
+        allowed: false,
+        reason: `Maximum concurrent agents reached (${String(this.budget.maxConcurrentAgents)})`,
+      };
+    }
+
+    const dailyUsed = this.getDailyTokensUsed();
+    if (this.budget.enforceHardLimits && dailyUsed >= this.budget.dailyTokenLimit) {
+      return {
+        allowed: false,
+        reason: `Daily token budget exceeded (${String(dailyUsed)}/${String(this.budget.dailyTokenLimit)})`,
+      };
+    }
+
+    return { allowed: true };
+  }
+
+  /**
+   * Check if an agent has exceeded its per-task budget (today only).
+   */
+  isAgentOverBudget(agentId: string): { overBudget: boolean; totalTokens: number } {
+    const todayStart = this.getTodayStart();
+    const agentRecords = this.records.filter(
+      (r) => r.agentId === agentId && r.timestamp >= todayStart
+    );
+    const totalTokens = agentRecords.reduce((sum, r) => sum + r.inputTokens + r.outputTokens, 0);
+
+    return {
+      overBudget: totalTokens >= this.budget.perAgentTokenLimit,
+      totalTokens,
+    };
+  }
+
+  /**
+   * Notify that an agent has started (track by ID).
+   */
+  agentStarted(agentId: string): void {
+    this.activeAgents.add(agentId);
+  }
+
+  /**
+   * Notify that an agent has stopped (remove by ID).
+   */
+  agentStopped(agentId: string): void {
+    this.activeAgents.delete(agentId);
+  }
+
+  /**
+   * Get comprehensive usage summary
+   */
+  getUsageSummary(): UsageSummary {
+    this.purgeStaleRecords();
+    const dailyTokensUsed = this.getDailyTokensUsed();
+    const dailyUsagePercent =
+      this.budget.dailyTokenLimit > 0 ? (dailyTokensUsed / this.budget.dailyTokenLimit) * 100 : 0;
+
+    return {
+      dailyTokensUsed,
+      dailyTokenLimit: this.budget.dailyTokenLimit,
+      dailyUsagePercent: Math.round(dailyUsagePercent * 100) / 100,
+      agentUsage: this.getAgentUsageSummaries(),
+      activeAgents: this.activeAgents.size,
+      maxConcurrentAgents: this.budget.maxConcurrentAgents,
+      budgetStatus: this.getBudgetStatus(dailyUsagePercent),
+    };
+  }
+
+  /**
+   * Get the configured budget
+   */
+  getBudget(): UsageBudget {
+    return { ...this.budget };
+  }
+
+  /**
+   * Load configuration with validation. Clamps invalid values to defaults.
+   */
+  private loadAndValidateConfig(): UsageBudget {
+    const raw = {
+      dailyTokenLimit:
+        this.configService.get<number>("orchestrator.budget.dailyTokenLimit") ??
+        DEFAULT_BUDGET.dailyTokenLimit,
+      perAgentTokenLimit:
+        this.configService.get<number>("orchestrator.budget.perAgentTokenLimit") ??
+        DEFAULT_BUDGET.perAgentTokenLimit,
+      maxConcurrentAgents:
+        this.configService.get<number>("orchestrator.budget.maxConcurrentAgents") ??
+        DEFAULT_BUDGET.maxConcurrentAgents,
+      maxTaskDurationMinutes:
+        this.configService.get<number>("orchestrator.budget.maxTaskDurationMinutes") ??
+        DEFAULT_BUDGET.maxTaskDurationMinutes,
+      enforceHardLimits:
+        this.configService.get<boolean>("orchestrator.budget.enforceHardLimits") ??
+        DEFAULT_BUDGET.enforceHardLimits,
+    };
+
+    return {
+      dailyTokenLimit: this.clampPositive(raw.dailyTokenLimit, DEFAULT_BUDGET.dailyTokenLimit),
+      perAgentTokenLimit: this.clampPositive(
+        raw.perAgentTokenLimit,
+        DEFAULT_BUDGET.perAgentTokenLimit
+      ),
+      maxConcurrentAgents: this.clampPositiveInt(
+        raw.maxConcurrentAgents,
+        DEFAULT_BUDGET.maxConcurrentAgents
+      ),
+      maxTaskDurationMinutes: this.clampPositiveInt(
+        raw.maxTaskDurationMinutes,
+        DEFAULT_BUDGET.maxTaskDurationMinutes
+      ),
+      enforceHardLimits: raw.enforceHardLimits,
+    };
+  }
+
+  private clampPositive(value: number, fallback: number): number {
+    return Number.isFinite(value) && value > 0 ? value : fallback;
+  }
+
+  private clampPositiveInt(value: number, fallback: number): number {
+    return Number.isFinite(value) && value > 0 ? Math.floor(value) : fallback;
+  }
+
+  /**
+   * Purge records from previous days to prevent unbounded memory growth.
+   */
+  private purgeStaleRecords(): void {
+    const todayStr = new Date().toISOString().slice(0, 10);
+    if (this.lastPurgeDate === todayStr) return;
+
+    const todayStart = this.getTodayStart();
+    const before = this.records.length;
+    this.records = this.records.filter((r) => r.timestamp >= todayStart);
+
+    if (before > this.records.length) {
+      this.logger.log(
+        `Purged ${String(before - this.records.length)} stale usage records from previous days`
+      );
+    }
+    this.lastPurgeDate = todayStr;
+  }
+
+  /**
+   * Get total tokens used today using proper Date comparison.
+   */
+  private getDailyTokensUsed(): number {
+    const todayStart = this.getTodayStart();
+
+    return this.records
+      .filter((r) => r.timestamp >= todayStart)
+      .reduce((sum, r) => sum + r.inputTokens + r.outputTokens, 0);
+  }
+
+  private getTodayStart(): Date {
+    const todayStart = new Date();
+    todayStart.setHours(0, 0, 0, 0);
+    return todayStart;
+  }
+
+  /**
+   * Get per-agent usage summaries (today only).
+   */
+  private getAgentUsageSummaries(): AgentUsageSummary[] {
+    const todayStart = this.getTodayStart();
+    const todayRecords = this.records.filter((r) => r.timestamp >= todayStart);
+    const agentMap = new Map<string, { taskId: string; input: number; output: number }>();
+
+    for (const record of todayRecords) {
+      const existing = agentMap.get(record.agentId);
+      if (existing) {
+        existing.input += record.inputTokens;
+        existing.output += record.outputTokens;
+      } else {
+        agentMap.set(record.agentId, {
+          taskId: record.taskId,
+          input: record.inputTokens,
+          output: record.outputTokens,
+        });
+      }
+    }
+
+    return [...agentMap.entries()].map(([agentId, data]) => {
+      const totalTokens = data.input + data.output;
+      const usagePercent =
+        this.budget.perAgentTokenLimit > 0
+          ? Math.round((totalTokens / this.budget.perAgentTokenLimit) * 10000) / 100
+          : 0;
+
+      return {
+        agentId,
+        taskId: data.taskId,
+        inputTokens: data.input,
+        outputTokens: data.output,
+        totalTokens,
+        usagePercent,
+      };
+    });
+  }
+
+  /**
+   * Determine overall budget status
+   */
+  private getBudgetStatus(dailyUsagePercent: number): BudgetStatus {
+    if (dailyUsagePercent >= 100) return "exceeded";
+    if (dailyUsagePercent >= 95) return "at_limit";
+    if (dailyUsagePercent >= 80) return "approaching_limit";
+    return "within_budget";
+  }
+}
diff --git a/apps/orchestrator/src/budget/budget.types.ts b/apps/orchestrator/src/budget/budget.types.ts
new file mode 100644
index 0000000..86a0c57
--- /dev/null
+++ b/apps/orchestrator/src/budget/budget.types.ts
@@ -0,0 +1,69 @@
+/**
+ * Usage Budget Management types
+ *
+ * Defines types for tracking and enforcing agent usage budgets
+ * including token limits, cost caps, and time-based constraints.
+ */
+
+export interface UsageBudget {
+  /** Daily token limit across all agents */
+  dailyTokenLimit: number;
+  /** Per-agent token limit per task */
+  perAgentTokenLimit: number;
+  /** Maximum concurrent agents */
+  maxConcurrentAgents: number;
+  /** Maximum task duration in minutes */
+  maxTaskDurationMinutes: number;
+  /** Whether to hard-stop agents exceeding budget */
+  enforceHardLimits: boolean;
+}
+
+export interface UsageRecord {
+  /** Agent that consumed tokens */
+  agentId: string;
+  /** Task being worked on */
+  taskId: string;
+  /** Number of input tokens used */
+  inputTokens: number;
+  /** Number of output tokens used */
+  outputTokens: number;
+  /** Timestamp of usage */
+  timestamp: Date;
+}
+
+export interface UsageSummary {
+  /** Total tokens used today */
+  dailyTokensUsed: number;
+  /** Daily token limit */
+  dailyTokenLimit: number;
+  /** Percentage of daily budget used */
+  dailyUsagePercent: number;
+  /** Per-agent usage breakdown */
+  agentUsage: AgentUsageSummary[];
+  /** Number of currently active agents */
+  activeAgents: number;
+  /** Maximum concurrent agents allowed */
+  maxConcurrentAgents: number;
+  /** Whether any budget thresholds are approaching */
+  budgetStatus: BudgetStatus;
+}
+
+export interface AgentUsageSummary {
+  agentId: string;
+  taskId: string;
+  inputTokens: number;
+  outputTokens: number;
+  totalTokens: number;
+  /** Percentage of per-agent limit used */
+  usagePercent: number;
+}
+
+export type BudgetStatus = "within_budget" | "approaching_limit" | "at_limit" | "exceeded";
+
+export const DEFAULT_BUDGET: UsageBudget = {
+  dailyTokenLimit: 10_000_000,
+  perAgentTokenLimit: 2_000_000,
+  maxConcurrentAgents: 10,
+  maxTaskDurationMinutes: 120,
+  enforceHardLimits: false,
+};