refactor(metering): route free-plan checks through isFreeSubscription (PUT-1830) (#4046)

src/backend/controllers/events/limits.ts

@@ -21,7 +21,7 @@ import type { RouteRateLimit } from '../../core/http/types';
 import {
     DEFAULT_FREE_SUBSCRIPTION,
     DEFAULT_TEMP_SUBSCRIPTION,
-    FREE_SUBSCRIPTION_IDS,
+    isFreeSubscription,
 } from '../../services/metering/consts.js';
 
 // -- Shared event limits ---------------------------------------------
@@ -69,7 +69,7 @@ export const limitFor = (
     if (subscriptionId === null) return tier.limit;
     const own = tier.bySubscription[subscriptionId];
     if (typeof own === 'number') return own;
-    return FREE_SUBSCRIPTION_IDS.has(subscriptionId)
+    return isFreeSubscription(subscriptionId)
         ? (tier.bySubscription[DEFAULT_FREE_SUBSCRIPTION] ?? tier.limit)
         : tier.limit;
 };

src/backend/core/http/middleware/rateLimit.js

@@ -23,7 +23,7 @@ import { withSpan } from '../../../util/span.js';
 import { HttpError } from '../HttpError.js';
 import {
     DEFAULT_FREE_SUBSCRIPTION,
-    FREE_SUBSCRIPTION_IDS,
+    isFreeSubscription,
 } from '../../../services/metering/consts.js';
 
 /**
@@ -873,7 +873,7 @@ export const CONCURRENT_SLOT_TTL_MS = ORPHAN_SAFETY_TTL_MS;
 function overrideFor(bySubscription, subscriptionId) {
     const own = bySubscription[subscriptionId];
     if (typeof own === 'number') return own;
-    return FREE_SUBSCRIPTION_IDS.has(subscriptionId)
+    return isFreeSubscription(subscriptionId)
         ? bySubscription[DEFAULT_FREE_SUBSCRIPTION]
         : undefined;
 }

src/backend/drivers/ai-chat/ChatCompletionDriver.test.ts

@@ -915,6 +915,46 @@ describe('ChatCompletionDriver.complete credit gate and max_tokens cap', () => {
         });
     });
 
+    it('admits a plan outside the free set to subscriber-only models', async () => {
+        vi.spyOn(FakeChatProvider.prototype, 'models').mockResolvedValueOnce([
+            {
+                id: 'subonly-paid',
+                aliases: [],
+                costs_currency: 'usd-cents',
+                costs: { 'input-tokens': 100, 'output-tokens': 100 },
+                max_tokens: 8192,
+                subscriberOnly: true,
+            },
+        ]);
+        const d = await makeDriver();
+        vi.spyOn(server.services.metering, 'getRemainingUsage').mockResolvedValue(
+            1_000_000,
+        );
+        vi.spyOn(
+            server.services.metering,
+            'getActorSubscription',
+        ).mockResolvedValue({ id: 'some-paid-tier' } as never);
+        const completeSpy = vi
+            .spyOn(FakeChatProvider.prototype, 'complete')
+            .mockResolvedValueOnce({
+                message: {
+                    role: 'assistant',
+                    content: [{ type: 'text', text: 'ok' }],
+                },
+                usage: { input_tokens: 1, output_tokens: 1 },
+                finish_reason: 'stop',
+            } as never);
+
+        await withTestActor(() =>
+            d.complete({
+                model: 'subonly-paid',
+                messages: [{ role: 'user', content: 'hi' }],
+            }),
+        );
+
+        expect(completeSpy).toHaveBeenCalledOnce();
+    });
+
     it('rejects subscriber-only models for the default free subscription', async () => {
         vi.spyOn(FakeChatProvider.prototype, 'models').mockResolvedValueOnce([
             {

src/backend/drivers/ai-chat/ChatCompletionDriver.ts

@@ -23,7 +23,7 @@ import { EventMap } from '../../clients/event/types.js';
 import type { Actor } from '../../core/actor.js';
 import { Context } from '../../core/context.js';
 import { HttpError, isHttpError } from '../../core/http/HttpError.js';
-import { FREE_SUBSCRIPTION_IDS } from '../../services/metering/consts.js';
+import { isFreeSubscription } from '../../services/metering/consts.js';
 import type { CreditHold } from '../../services/metering/types.js';
 import { NO_CREDIT_HOLD } from '../../services/metering/types.js';
 import type { DriverStreamResult } from '../meta.js';
@@ -977,8 +977,7 @@ export class ChatCompletionDriver extends PuterDriver {
 
         if (model.subscriberOnly) {
             const subscription = await metering.getActorSubscription(actor);
-            // Every free plan, not two named ones.
-            if (FREE_SUBSCRIPTION_IDS.has(subscription.id)) {
+            if (isFreeSubscription(subscription.id)) {
                 throw new HttpError(
                     403,
                     `The model ${model.id} is only available to subscribers. Please subscribe to access this model.`,

src/backend/services/metering/MeteringService.ts

@@ -26,7 +26,6 @@ import {
     DEFAULT_FREE_SUBSCRIPTION,
     DEFAULT_TEMP_SUBSCRIPTION,
     DETAIL_PATH_COUNTER,
-    FREE_SUBSCRIPTION_IDS,
     GLOBAL_APP_KEY,
     METRICS_PREFIX,
     METRICS_V2_PREFIX,
@@ -37,6 +36,7 @@ import {
     UNLIMITED_SUBSCRIPTION,
     USAGE_DETAIL_SHARD_COUNT,
     V1_CLAIM_THROUGH_MONTH,
+    isFreeSubscription,
 } from './consts';
 import { EGRESS_COSTS } from './costs';
 import type {
@@ -2078,7 +2078,7 @@ export class MeteringService extends PuterService {
         month: string = this.monthYearString(),
     ): Promise<SubscriptionPolicy> {
         if (
-            FREE_SUBSCRIPTION_IDS.has(policy.id) ||
+            isFreeSubscription(policy.id) ||
             policy.id === UNLIMITED_SUBSCRIPTION ||
             !(policy.monthUsageAllowance > 0)
         ) {

src/backend/services/metering/consts.ts

@@ -78,5 +78,9 @@ export const FREE_SUBSCRIPTION_IDS: ReadonlySet<string> = new Set([
     ORG_SEAT_FREE_SUBSCRIPTION,
 ]);
 
+/** Whether a policy id is a free plan. Check free-ness here, not on the set. */
+export const isFreeSubscription = (id: string): boolean =>
+    FREE_SUBSCRIPTION_IDS.has(id);
+
 // WARNING: DO NOT USE THESE IN PROD
 export const UNLIMITED_SUBSCRIPTION = 'unlimited';

src/backend/services/metering/enforcement.test.ts

@@ -21,6 +21,7 @@ import { describe, expect, it, vi } from 'vitest';
 import { SYSTEM_ACTOR, type Actor } from '../../core/actor.js';
 import { HttpError } from '../../core/http/HttpError.js';
 import type { IConfig } from '../../types';
+import { FREE_SUBSCRIPTION_IDS, isFreeSubscription } from './consts.js';
 import {
     actorHasSubscription,
     actorOnPaidPlan,
@@ -260,6 +261,28 @@ describe('subscriptionSatisfies', () => {
     });
 });
 
+describe('isFreeSubscription', () => {
+    it('is true for exactly the free policies', () => {
+        for (const id of FREE_SUBSCRIPTION_IDS) {
+            expect(isFreeSubscription(id)).toBe(true);
+        }
+        for (const id of ['professional', 'unlimited', 'some-paid-tier', '']) {
+            expect(isFreeSubscription(id)).toBe(false);
+        }
+        // Untyped callers can pass an id that never resolved.
+        expect(isFreeSubscription(undefined as never)).toBe(false);
+        expect(isFreeSubscription(null as never)).toBe(false);
+    });
+
+    it('is the complement of a `true` requirement', () => {
+        for (const id of [...FREE_SUBSCRIPTION_IDS, 'professional', '']) {
+            expect(subscriptionSatisfies(id, true)).toBe(
+                !isFreeSubscription(id),
+            );
+        }
+    });
+});
+
 describe('validateSubscriptionRequirement', () => {
     it('passes booleans and non-empty id lists through', () => {
         expect(validateSubscriptionRequirement(true, 'x')).toBe(true);

src/backend/services/metering/enforcement.ts

@@ -21,7 +21,7 @@ import type { Actor } from '../../core/actor';
 import { isSystemActor } from '../../core/actor';
 import { HttpError } from '../../core/http/HttpError.js';
 import type { IConfig } from '../../types';
-import { FREE_SUBSCRIPTION_IDS } from './consts.js';
+import { isFreeSubscription } from './consts.js';
 import type { MeteringService } from './MeteringService';
 
 // -- Credit enforcement ----------------------------------------------
@@ -148,7 +148,7 @@ export const subscriptionSatisfies = (
     if (Array.isArray(requirement)) {
         return requirement.length === 0 || requirement.includes(id);
     }
-    return !FREE_SUBSCRIPTION_IDS.has(id);
+    return !isFreeSubscription(id);
 };
 
 /**