diff --git a/server/providers/payment/plugins/polar.ts b/server/providers/payment/plugins/polar.ts
index 18811df4..38be0b0e 100644
--- a/server/providers/payment/plugins/polar.ts
+++ b/server/providers/payment/plugins/polar.ts
@@ -360,8 +360,17 @@ function createPolarProvider(config: PaymentPluginConfig): PaymentProvider {
       return { productId: targetProductId, alreadyOnList: false }
     },
 
-    async cancelSubscription(subscriptionId: string): Promise<void> {
-      await polar.subscriptions.revoke({ id: subscriptionId })
+    async cancelSubscription(subscriptionId: string): Promise<'canceled' | 'already_ended'> {
+      try {
+        await polar.subscriptions.revoke({ id: subscriptionId })
+        return 'canceled'
+      }
+      catch (err) {
+        // Already ended (an operator refunded it, or an earlier call revoked it) or gone: nothing left to cancel.
+        const kind = (err as { error?: unknown }).error
+        if (kind === 'AlreadyCanceledSubscription' || kind === 'ResourceNotFound') return 'already_ended'
+        throw err
+      }
     },
 
     async ingestUsageEvent(input: UsageEventInput): Promise<void> {
diff --git a/server/providers/payment/plugins/stripe.ts b/server/providers/payment/plugins/stripe.ts
index 4b293105..e790874d 100644
--- a/server/providers/payment/plugins/stripe.ts
+++ b/server/providers/payment/plugins/stripe.ts
@@ -233,8 +233,9 @@ function createStripeProvider(config: PaymentPluginConfig): PaymentProvider {
       throw new Error('The Migrate bundle is Polar-only')
     },
 
-    async cancelSubscription(subscriptionId: string): Promise<void> {
+    async cancelSubscription(subscriptionId: string): Promise<'canceled' | 'already_ended'> {
       await stripe.subscriptions.cancel(subscriptionId)
+      return 'canceled'
     },
 
     async ingestUsageEvent(_input: UsageEventInput): Promise<void> {
diff --git a/server/providers/payment/types.ts b/server/providers/payment/types.ts
index f1ebe262..4feb80e9 100644
--- a/server/providers/payment/types.ts
+++ b/server/providers/payment/types.ts
@@ -170,7 +170,8 @@ export interface PaymentProvider {
   handleWebhook: (payload: string, headers: Record<string, string | undefined>) => Promise<WebhookResult>
 
   /** Cancel a subscription (immediate). */
-  cancelSubscription: (subscriptionId: string) => Promise<void>
+  /** Ends the subscription now. `already_ended` when the provider reports it was already ended or is gone (not an error: the goal is met). */
+  cancelSubscription: (subscriptionId: string) => Promise<'canceled' | 'already_ended'>
 
   /**
    * Open a Migrate bundle checkout (see `BundleCheckoutInput`). Providers
diff --git a/server/utils/migrate-revoke.ts b/server/utils/migrate-revoke.ts
index 3b23f3c5..bbbbf500 100644
--- a/server/utils/migrate-revoke.ts
+++ b/server/utils/migrate-revoke.ts
@@ -29,8 +29,8 @@ export async function revokeMigrateGrant(grant: DatabaseRow, reason: MigrateRevo
       const payment = usePaymentProvider()
       if (!payment) throw createError({ statusCode: 503, message: errorMessage('generic.server_error') })
       try {
-        await payment.cancelSubscription(subscriptionId)
-        canceled = true
+        // An already ended subscription is the goal met, not a failure: the grant is still marked below.
+        canceled = (await payment.cancelSubscription(subscriptionId)) === 'canceled'
       }
       catch (err) {
         // eslint-disable-next-line no-console -- ops visibility: Migrate retries the call
diff --git a/tests/unit/migrate-revoke-route.test.ts b/tests/unit/migrate-revoke-route.test.ts
index f354eca9..462746e7 100644
--- a/tests/unit/migrate-revoke-route.test.ts
+++ b/tests/unit/migrate-revoke-route.test.ts
@@ -44,7 +44,7 @@ describe('POST /api/migrate/grants/revoke', () => {
     vi.resetModules()
     taken.clear()
     config.migrate.claimPublicKey = publicPem
-    payment = { cancelSubscription: vi.fn().mockResolvedValue(undefined) }
+    payment = { cancelSubscription: vi.fn().mockResolvedValue('canceled') }
     db = {
       getMigrateGrantByOrderId: vi.fn().mockResolvedValue(grant()),
       getWorkspaceById: vi.fn().mockResolvedValue({ id: 'ws-1', github_installation_id: null }),
@@ -104,6 +104,14 @@ describe('POST /api/migrate/grants/revoke', () => {
     expect(db.markMigrateGrantRevoked).not.toHaveBeenCalled()
   })
 
+  it('treats a subscription Polar already ended as done: grant revoked, nothing canceled, no 502 loop', async () => {
+    payment!.cancelSubscription.mockResolvedValue('already_ended')
+    await request()
+    expect(await call()).toEqual({ state: 'revoked', installed: false, subscription_canceled: false })
+    expect(db.markMigrateGrantRevoked).toHaveBeenCalledWith('grant-1', 'refund_before_delivery')
+    expect(db.releaseMigrateS2sJti).not.toHaveBeenCalled()
+  })
+
   it('leaves the grant live and gives the token back when Polar fails, so Migrate can retry', async () => {
     payment!.cancelSubscription.mockRejectedValue(new Error('polar down'))
     vi.spyOn(console, 'error').mockImplementation(() => {})
diff --git a/tests/unit/polar-subscription-lifecycle.test.ts b/tests/unit/polar-subscription-lifecycle.test.ts
index 92857fb4..50fd4768 100644
--- a/tests/unit/polar-subscription-lifecycle.test.ts
+++ b/tests/unit/polar-subscription-lifecycle.test.ts
@@ -1,5 +1,11 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
+const revoke = vi.fn()
+vi.mock('@polar-sh/sdk', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('@polar-sh/sdk')>()
+  return { ...actual, Polar: class { subscriptions = { revoke: (...a: unknown[]) => revoke(...a) } } }
+})
+
 // The webhook signature is not under test: hand the plugin the parsed event.
 const validateEvent = vi.fn()
 vi.mock('@polar-sh/sdk/webhooks', () => ({
@@ -104,3 +110,25 @@ describe('polar plugin — cancel and revoke keep what was paid for', () => {
     expect(result).toMatchObject({ event: 'subscription.updated', subscriptionStatus: 'past_due' })
   })
 })
+
+describe('polar plugin — cancelSubscription', () => {
+  const provider = async () => {
+    const { polarPlugin } = await import('../../server/providers/payment/plugins/polar')
+    return polarPlugin.create({ polar: { accessToken: 'tok', webhookSecret: 'sec', proProductId: 'prod_pro' } } as never)
+  }
+
+  it('answers canceled when Polar revokes it', async () => {
+    revoke.mockResolvedValue({})
+    expect(await (await provider()).cancelSubscription('sub_1')).toBe('canceled')
+  })
+
+  it.each(['AlreadyCanceledSubscription', 'ResourceNotFound'])('answers already_ended for Polar\'s %s', async (error) => {
+    revoke.mockRejectedValue(Object.assign(new Error(error), { error }))
+    expect(await (await provider()).cancelSubscription('sub_1')).toBe('already_ended')
+  })
+
+  it('still throws any other provider failure', async () => {
+    revoke.mockRejectedValue(new Error('polar down'))
+    await expect((await provider()).cancelSubscription('sub_1')).rejects.toThrow('polar down')
+  })
+})