diff --git a/packages/capabilities/src/types.ts b/packages/capabilities/src/types.ts
index 37c6c05e3..9848a42ca 100644
--- a/packages/capabilities/src/types.ts
+++ b/packages/capabilities/src/types.ts
@@ -49,6 +49,15 @@ export type CARLink = Link<unknown, typeof CAR.codec.code>
 export type AccountDID = DID<'mailto'>
 export type SpaceDID = DID<'key'>
 
+/**
+ * Error for cases where an interface implementation needs to return an
+ * error that isn't defined explicitly in the interface.
+ */
+export interface UnexpectedError extends Ucanto.Failure {
+  name: 'UnexpectedError'
+  cause: unknown
+}
+
 /**
  * failure due to a resource not having enough storage capacity.
  */
@@ -628,7 +637,7 @@ export interface PlanNotFound extends Ucanto.Failure {
   name: 'PlanNotFound'
 }
 
-export type PlanGetFailure = PlanNotFound
+export type PlanGetFailure = PlanNotFound | UnexpectedError
 
 export type PlanSet = InferInvokedCapability<typeof PlanCaps.set>
 
@@ -645,7 +654,14 @@ export interface InvalidPlanName extends Ucanto.Failure {
   name: 'InvalidPlanName'
 }
 
-export type PlanSetFailure = CustomerNotFound
+export interface PlanUpdateError extends Ucanto.Failure {
+  name: 'PlanUpdateError'
+}
+
+export type PlanSetFailure =
+  | CustomerNotFound
+  | PlanUpdateError
+  | UnexpectedError
 
 // Top
 export type Top = InferInvokedCapability<typeof top>
diff --git a/packages/upload-api/package.json b/packages/upload-api/package.json
index ef19f62ea..157b171c0 100644
--- a/packages/upload-api/package.json
+++ b/packages/upload-api/package.json
@@ -30,6 +30,9 @@
       "customer": [
         "dist/src/customer.d.ts"
       ],
+      "plan": [
+        "dist/src/plan.d.ts"
+      ],
       "provider": [
         "dist/src/provider.d.ts"
       ],
@@ -81,6 +84,10 @@
       "types": "./dist/src/provider.d.ts",
       "import": "./src/provider.js"
     },
+    "./plan": {
+      "types": "./dist/src/plan.d.ts",
+      "import": "./src/plan.js"
+    },
     "./space": {
       "types": "./dist/src/space.d.ts",
       "import": "./src/space.js"
diff --git a/packages/upload-api/src/types/plans.ts b/packages/upload-api/src/types/plans.ts
index 6bfc06a12..4c82b3847 100644
--- a/packages/upload-api/src/types/plans.ts
+++ b/packages/upload-api/src/types/plans.ts
@@ -1,5 +1,13 @@
 import * as Ucanto from '@ucanto/interface'
-import { AccountDID, DID, PlanGetFailure, PlanGetSuccess, PlanSetFailure, PlanSetSuccess } from '../types.js'
+import {
+  AccountDID,
+  DID,
+  PlanGetFailure,
+  PlanGetSuccess,
+  PlanSetFailure,
+  PlanSetSuccess,
+  UnexpectedError,
+} from '../types.js'
 
 export type PlanID = DID
 
@@ -7,7 +15,7 @@ export interface CustomerExists extends Ucanto.Failure {
   name: 'CustomerExists'
 }
 
-type PlanInitializeFailure = CustomerExists
+type PlanInitializeFailure = CustomerExists | UnexpectedError
 
 /**
  * Stores subscription plan information.
@@ -16,10 +24,10 @@ export interface PlansStorage {
   /**
    * Initialize a customer in our system, tracking the external billing
    * system ID and the plan they have chosen.
-   * 
+   *
    * Designed to be use from, eg, a webhook handler for an account creation event
    * in a third party billing system.
-   * 
+   *
    * @param account account DID
    * @param billingID ID used by billing system to track this account
    * @param plan the ID of the initial plan
diff --git a/packages/upload-api/test/storage/plans-storage-tests.js b/packages/upload-api/test/storage/plans-storage-tests.js
index 00dda9661..ac403102e 100644
--- a/packages/upload-api/test/storage/plans-storage-tests.js
+++ b/packages/upload-api/test/storage/plans-storage-tests.js
@@ -11,7 +11,11 @@ export const test = {
   'can initialize a customer': async (assert, context) => {
     const storage = context.plansStorage
 
-    const initializeResult = await storage.initialize(account, billingID, product)
+    const initializeResult = await storage.initialize(
+      account,
+      billingID,
+      product
+    )
 
     assert.ok(initializeResult.ok)
 
@@ -19,7 +23,10 @@ export const test = {
     assert.equal(getResult.ok?.product, product)
   },
 
-  'should not allow plans to be updated for uninitialized customers': async (assert, context) => {
+  'should not allow plans to be updated for uninitialized customers': async (
+    assert,
+    context
+  ) => {
     const storage = context.plansStorage
 
     const setResult = await storage.set(account, product)
@@ -28,10 +35,17 @@ export const test = {
     assert.equal(setResult.error?.name, 'CustomerNotFound')
   },
 
-  'should allow plans to be updated for initialized customers': async (assert, context) => {
+  'should allow plans to be updated for initialized customers': async (
+    assert,
+    context
+  ) => {
     const storage = context.plansStorage
 
-    const initializeResult = await storage.initialize(account, billingID, product)
+    const initializeResult = await storage.initialize(
+      account,
+      billingID,
+      product
+    )
 
     assert.ok(initializeResult.ok)
 
diff --git a/packages/upload-api/test/storage/plans-storage.js b/packages/upload-api/test/storage/plans-storage.js
index 6a892ef88..a8bd07a20 100644
--- a/packages/upload-api/test/storage/plans-storage.js
+++ b/packages/upload-api/test/storage/plans-storage.js
@@ -13,16 +13,20 @@ export class PlansStorage {
   }
 
   /**
-   * 
-   * @param {Types.AccountDID} account 
-   * @param {string} billingID 
-   * @param {Types.DID} product 
+   *
+   * @param {Types.AccountDID} account
+   * @param {string} billingID
+   * @param {Types.DID} product
    */
   async initialize(account, billingID, product) {
     if (this.plans[account]) {
       return { error: new CustomerExists(account) }
     }
-    this.plans[account] = { product, billingID, updatedAt: new Date().toISOString() }
+    this.plans[account] = {
+      product,
+      billingID,
+      updatedAt: new Date().toISOString(),
+    }
     return { ok: {} }
   }