diff --git a/CHANGELOG.md b/CHANGELOG.md
index c5250884..68cc0f20 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+- added: `EdgeContext.fetchChallenge`, to request an account-creation CAPTCHA.
+- added: Accept a challengeId in `EdgeContext.usernameAvailable`
+
 ## 2.14.0 (2024-09-03)
 
 - added: Log HTTP 409 errors from login server with breadcrumbs.
diff --git a/src/core/context/context-api.ts b/src/core/context/context-api.ts
index 92dcdda7..549b962e 100644
--- a/src/core/context/context-api.ts
+++ b/src/core/context/context-api.ts
@@ -2,6 +2,7 @@ import { bridgifyObject, onMethod, watchMethod } from 'yaob'
 
 import { checkPasswordRules, fixUsername } from '../../client-side'
 import {
+  asChallengeErrorPayload,
   EdgeAccount,
   EdgeAccountOptions,
   EdgeContext,
@@ -17,6 +18,7 @@ import { findAppLogin, makeAccount } from '../account/account-init'
 import { createLogin, usernameAvailable } from '../login/create'
 import { requestEdgeLogin } from '../login/edge'
 import { makeLoginTree, syncLogin } from '../login/login'
+import { loginFetch } from '../login/login-fetch'
 import { fetchLoginMessages } from '../login/login-messages'
 import {
   getEmptyStash,
@@ -70,9 +72,16 @@ export function makeContextApi(ai: ApiInput): EdgeContext {
       await removeStash(ai, loginId)
     },
 
-    async usernameAvailable(username: string): Promise<boolean> {
+    async fetchChallenge() {
+      const response = await loginFetch(ai, 'POST', '/v2/captcha/create', {})
+      const { challengeId, challengeUri } = asChallengeErrorPayload(response)
+      return { challengeId, challengeUri }
+    },
+
+    async usernameAvailable(username: string, opts = {}): Promise<boolean> {
+      const { challengeId } = opts
       username = fixUsername(username)
-      return await usernameAvailable(ai, username)
+      return await usernameAvailable(ai, username, challengeId)
     },
 
     async createAccount(
diff --git a/src/core/login/create.ts b/src/core/login/create.ts
index eb15a728..bf36a32e 100644
--- a/src/core/login/create.ts
+++ b/src/core/login/create.ts
@@ -29,10 +29,12 @@ export interface LoginCreateOpts {
  */
 export async function usernameAvailable(
   ai: ApiInput,
-  username: string
+  username: string,
+  challengeId?: string
 ): Promise<boolean> {
   const userId = await hashUsername(ai, username)
   const request = {
+    challengeId,
     userId
   }
   return await loginFetch(ai, 'POST', '/v2/login', request)
@@ -147,13 +149,13 @@ export async function createLogin(
   accountOpts: EdgeAccountOptions,
   opts: LoginCreateOpts
 ): Promise<LoginTree> {
+  const { challengeId, now = new Date() } = accountOpts
+
   // For crash errors:
   ai.props.log.breadcrumb('createLogin', {})
 
-  const { now = new Date() } = accountOpts
-
   const kit = await makeCreateKit(ai, undefined, '', opts)
-  const request = { data: kit.server }
+  const request = { challengeId, data: kit.server }
   await loginFetch(ai, 'POST', kit.serverPath, request)
 
   kit.stash.lastLogin = now
diff --git a/src/types/server-cleaners.ts b/src/types/server-cleaners.ts
index 46958347..bc8c6403 100644
--- a/src/types/server-cleaners.ts
+++ b/src/types/server-cleaners.ts
@@ -26,6 +26,7 @@ import type {
   ChangeSecretPayload,
   ChangeUsernamePayload,
   ChangeVouchersPayload,
+  CreateChallengePayload,
   CreateKeysPayload,
   CreateLoginPayload,
   EdgeBox,
@@ -257,6 +258,12 @@ export const asChallengeErrorPayload: Cleaner<ChallengeErrorPayload> = asObject(
   }
 )
 
+export const asCreateChallengePayload: Cleaner<CreateChallengePayload> =
+  asObject({
+    challengeId: asString,
+    challengeUri: asOptional(asString)
+  })
+
 export const asLobbyPayload: Cleaner<LobbyPayload> = asObject({
   request: asEdgeLobbyRequest,
   replies: asArray(asEdgeLobbyReply)
@@ -407,6 +414,9 @@ export const wasCreateLoginPayload =
 export const wasChallengeErrorPayload = uncleaner<ChallengeErrorPayload>(
   asChallengeErrorPayload
 )
+export const wasCreateChallengePayload = uncleaner<CreateChallengePayload>(
+  asCreateChallengePayload
+)
 export const wasLobbyPayload = uncleaner<LobbyPayload>(asLobbyPayload)
 export const wasLoginPayload = uncleaner<LoginPayload>(asLoginPayload)
 export const wasMessagesPayload = uncleaner<MessagesPayload>(asMessagesPayload)
diff --git a/src/types/server-types.ts b/src/types/server-types.ts
index 0ccbdc3d..c2b2bf78 100644
--- a/src/types/server-types.ts
+++ b/src/types/server-types.ts
@@ -194,6 +194,14 @@ export interface ChallengeErrorPayload {
   challengeUri: string
 }
 
+/**
+ * Data sent back when preemptively requesting a CAPTCHA.
+ */
+export interface CreateChallengePayload {
+  challengeId: string
+  challengeUri?: string
+}
+
 /**
  * Data sent back when looking up a login barcode.
  */
diff --git a/src/types/types.ts b/src/types/types.ts
index b863bace..d5cbbbbb 100644
--- a/src/types/types.ts
+++ b/src/types/types.ts
@@ -1840,8 +1840,17 @@ export interface EdgeContext {
   readonly forgetAccount: (rootLoginId: string) => Promise<void>
 
   // Account creation:
+  /** Preemptively requests a CAPTCHA for account creation. */
+  readonly fetchChallenge: () => Promise<{
+    challengeId: string
+    /** If this is missing, the challenge is already solved. */
+    challengeUri?: string
+  }>
   readonly fixUsername: (username: string) => string
-  readonly usernameAvailable: (username: string) => Promise<boolean>
+  readonly usernameAvailable: (
+    username: string,
+    opts?: { challengeId?: string }
+  ) => Promise<boolean>
   readonly createAccount: (
     opts: EdgeCreateAccountOptions & EdgeAccountOptions
   ) => Promise<EdgeAccount>