diff --git a/packages/capabilities/src/top.js b/packages/capabilities/src/top.js
index 06a075ff9..3134de58f 100644
--- a/packages/capabilities/src/top.js
+++ b/packages/capabilities/src/top.js
@@ -9,7 +9,7 @@
  * @module
  */
 
-import { capability, URI } from '@ucanto/validator'
+import { capability, Schema } from '@ucanto/validator'
 import { equalWith } from './utils.js'
 
 /**
@@ -20,6 +20,6 @@ import { equalWith } from './utils.js'
  */
 export const top = capability({
   can: '*',
-  with: URI.match({ protocol: 'did:' }),
+  with: Schema.or(Schema.did(), Schema.literal('ucan:*')),
   derives: equalWith,
 })
diff --git a/packages/upload-api/test/access-client-agent.js b/packages/upload-api/test/access-client-agent.js
index ad332925a..7f56a589b 100644
--- a/packages/upload-api/test/access-client-agent.js
+++ b/packages/upload-api/test/access-client-agent.js
@@ -2,7 +2,7 @@ import * as API from './types.js'
 import { Absentee } from '@ucanto/principal'
 import * as delegationsResponse from '../src/utils/delegations-response.js'
 import * as DidMailto from '@web3-storage/did-mailto'
-import { Access, Space } from '@web3-storage/capabilities'
+import { Access, Space, Top } from '@web3-storage/capabilities'
 import { AgentData } from '@web3-storage/access'
 import { alice } from './helpers/utils.js'
 import { stringToDelegations } from '@web3-storage/access/encoding'
@@ -24,6 +24,80 @@ import {
 } from '@web3-storage/access/agent'
 import * as Provider from '@web3-storage/access/provider'
 
+/**
+ * Create and return a space, delegated to the device agent and to the account,
+ * and provisioned for the account.
+ *
+ * @param {Agent} device
+ * @param {API.Principal<import('@ucanto/interface').DID<"mailto">>} account
+ * @param {API.Assert} assert
+ */
+const createSpace = async (device, account, assert) => {
+  const space = await device.createSpace(
+    `space-test-${Math.random().toString().slice(2)}`
+  )
+
+  assert.ok(space.did())
+  // provision space with an account so it can store delegations
+  const provisionResult = await Provider.add(device, {
+    account: account.did(),
+    consumer: space.did(),
+  })
+  assert.ok(provisionResult.ok)
+
+  // authorize device
+  const auth = await space.createAuthorization(device, {
+    access: AgentAccess.spaceAccess,
+    expiration: Infinity,
+  })
+  await device.importSpaceFromDelegation(auth)
+
+  // make space current
+  await device.setCurrentSpace(space.did())
+
+  const recovery = await space.createRecovery(account.did())
+  const delegateResult = await AgentAccess.delegate(device, {
+    delegations: [recovery],
+  })
+  assert.ok(delegateResult.ok)
+  return space
+}
+
+/**
+ * Claim (`access/claim`) delegations for the device agent, and add them to the
+ * agent's proofs.
+ *
+ * @param {Agent} device
+ */
+const claimDelegations = async (device) => {
+  await claimAccess(device, device.issuer.did(), {
+    addProofs: true,
+    nonce: Math.random().toString(),
+  })
+}
+
+/**
+ * Assert that the device agent can invoke `space/info` on the given space.
+ *
+ * @param {Agent} device
+ * @param {import('@web3-storage/access/agent').OwnedSpace} space
+ * @param {API.Assert} assert
+ */
+async function assertCanSpaceInfo(device, space, assert) {
+  const spaceInfoResult = await device.invokeAndExecute(Space.info, {
+    with: space.did(),
+  })
+
+  assert.equal(spaceInfoResult.out.error, undefined)
+
+  assert.ok(spaceInfoResult.out.ok)
+  const result =
+    /** @type {import('@web3-storage/access/types').SpaceInfoResult} */ (
+      spaceInfoResult.out.ok
+    )
+  assert.deepEqual(result.did, space.did())
+}
+
 /**
  * @type {API.Tests}
  */
@@ -240,104 +314,107 @@ export const test = {
     const account = Absentee.from({ id: DidMailto.fromEmail(email) })
 
     // first device
-    const deviceAAgentData = await AgentData.create()
-    const deviceA = await Agent.create(deviceAAgentData, {
+    const deviceA = await Agent.create(await AgentData.create(), {
       connection,
     })
+    await requestAccess(deviceA, account, [{ can: '*' }])
+    await confirmConfirmationUrl(deviceA.connection, await mail.take())
+    await claimDelegations(deviceA)
 
-    /**
-     * @param {Agent} device
-     */
-    const createSpace = async (device) => {
-      const space = await device.createSpace(
-        `space-test-${Math.random().toString().slice(2)}`
-      )
-
-      assert.ok(space.did())
-      // provision space with an account so it can store delegations
-      const provisionResult = await Provider.add(device, {
-        account: account.did(),
-        consumer: space.did(),
-      })
-      assert.ok(provisionResult.ok)
-
-      // authorize device
-      const auth = await space.createAuthorization(device, {
-        access: AgentAccess.spaceAccess,
-        expiration: Infinity,
-      })
-      await device.importSpaceFromDelegation(auth)
-
-      // make space current
-      await device.setCurrentSpace(space.did())
+    // deviceA creates a space
+    const space1 = await createSpace(deviceA, account, assert)
 
-      const recovery = await space.createRecovery(account.did())
-      const delegateResult = await AgentAccess.delegate(device, {
-        delegations: [recovery],
-      })
-      assert.ok(delegateResult.ok)
-      return space
-    }
+    // second device
+    const deviceB = await Agent.create(await AgentData.create(), {
+      connection,
+    })
+    await requestAccess(deviceB, account, [{ can: '*' }])
+    await confirmConfirmationUrl(deviceB.connection, await mail.take())
+    await claimDelegations(deviceB)
 
-    /**
-     * @param {Agent} device
-     */
-    const claimDelegations = async (device) => {
-      await claimAccess(device, device.issuer.did(), {
-        addProofs: true,
-        nonce: Math.random().toString(),
-      })
-      }
+    // issuer + account proofs should authorize deviceB to invoke space/info
+    await assertCanSpaceInfo(deviceB, space1, assert)
 
-    /**
-     * @param {import('@web3-storage/access/agent').OwnedSpace} space
-     */
-    async function assertDeviceBCanSpaceInfo(space) {
-      const spaceInfoResult = await deviceB.invokeAndExecute(Space.info, {
-        with: space.did(),
-      })
+    // deviceA creates another space
+    const space2 = await createSpace(deviceA, account, assert)
 
-      assert.equal(spaceInfoResult.out.error, undefined)
+    // deviceB claims delegations again
+    await claimDelegations(deviceB)
 
-      assert.ok(spaceInfoResult.out.ok)
-      const result =
-        /** @type {import('@web3-storage/access/types').SpaceInfoResult} */ (
-          spaceInfoResult.out.ok
-        )
-      assert.deepEqual(result.did, space.did())
-    }
+    // now deviceB should be able to invoke space/info on space2
+    await assertCanSpaceInfo(deviceB, space2, assert)
+  },
+  'cannot gain unattested access': async (assert, context) => {
+    const { connection, mail } = context
+    const email = 'example@dag.house'
+    const account = Absentee.from({ id: DidMailto.fromEmail(email) })
 
-    // deviceA authorization
+    // first device
+    const deviceA = await Agent.create(await AgentData.create(), {
+      connection,
+    })
     await requestAccess(deviceA, account, [{ can: '*' }])
     await confirmConfirmationUrl(deviceA.connection, await mail.take())
     await claimDelegations(deviceA)
 
     // deviceA creates a space
-    const space = await createSpace(deviceA)
+    const space = await createSpace(deviceA, account, assert)
 
-    // second device - deviceB
-    const deviceBData = await AgentData.create()
+    const accountCheater = Absentee.from({
+      id: DidMailto.fromEmail('cheater@example.com'),
+    })
 
-    const deviceB = await Agent.create(deviceBData, {
+    // second device is unrelated
+    const deviceCheater = await Agent.create(await AgentData.create(), {
       connection,
     })
 
-    // authorize deviceB
-    await requestAccess(deviceB, account, [{ can: '*' }])
-    await confirmConfirmationUrl(deviceB.connection, await mail.take())
-    await claimDelegations(deviceB)
+    await requestAccess(deviceCheater, accountCheater, [{ can: '*' }])
+    await confirmConfirmationUrl(deviceCheater.connection, await mail.take())
+    await claimDelegations(deviceCheater)
 
-    // issuer + account proofs should authorize deviceB to invoke space/info
-    await assertDeviceBCanSpaceInfo(space)
+    const spaceCheater = await createSpace(
+      deviceCheater,
+      accountCheater,
+      assert
+    )
 
-    // deviceA creates another space
-    const space2 = await createSpace(deviceA)
+    // deviceCheater shouldn't have access to the space
+    deviceCheater.setCurrentSpace(space.did())
 
-    // deviceB claims delegations again
-    await claimDelegations(deviceB)
+    // deviceCheater tries to craft a delegation to gain access to the account
+    const unattestedDelegation = await Top.top.delegate({
+      issuer: Absentee.from({ id: account.did() }),
+      audience: deviceCheater,
+      with: 'ucan:*',
+      expiration: Infinity,
+      proofs: [],
+    })
 
-    // now deviceB should be able to invoke space/info on space2
-    await assertDeviceBCanSpaceInfo(space2)
+    // Then they store the delegation on the server
+    const delegateResult = await AgentAccess.delegate(deviceCheater, {
+      delegations: [unattestedDelegation],
+      space: spaceCheater.did(),
+    })
+
+    assert.ok(
+      delegateResult.ok,
+      `delegateResult.error: ${delegateResult.error}`
+    )
+
+    // Then they claim their delegations. If their attack is successful, they,
+    // now have access to the account and all its spaces.
+    await claimDelegations(deviceCheater)
+
+    // Assert that they still can't do anything to the space.
+    await assert.rejects(
+      deviceCheater.invokeAndExecute(Space.info, {
+        with: space.did(),
+      }),
+      {
+        message: `no proofs available for resource ${space.did()} and ability space/info`,
+      }
+    )
   },
   'can addSpacesFromDelegations': async (assert, context) => {
     const { agent } = await setup(context)
diff --git a/packages/upload-api/test/types.ts b/packages/upload-api/test/types.ts
index 6544bac7c..83c3eebbf 100644
--- a/packages/upload-api/test/types.ts
+++ b/packages/upload-api/test/types.ts
@@ -1,4 +1,5 @@
 import * as API from '../src/types.js'
+import assert from 'node:assert'
 
 export * from '../src/types.js'
 
@@ -19,13 +20,14 @@ export interface Assert {
     actual: Actual,
     expected: Expected,
     message?: string
-  ) => unknown
+  ) => void
   deepEqual: <Actual, Expected extends Actual>(
     actual: Actual,
     expected: Expected,
     message?: string
-  ) => unknown
-  ok: <Actual>(actual: Actual, message?: string) => unknown
+  ) => void
+  ok: <Actual>(actual: Actual, message?: string) => void
+  rejects: typeof assert.rejects
 }
 
 export type Test = (assert: Assert, context: TestContext) => unknown