diff --git a/src/agents/auth-profiles/oauth-identity.test.ts b/src/agents/auth-profiles/oauth-identity.test.ts
index cbfaff0c7cb..4fef5d5385d 100644
--- a/src/agents/auth-profiles/oauth-identity.test.ts
+++ b/src/agents/auth-profiles/oauth-identity.test.ts
@@ -6,6 +6,7 @@ import {
   normalizeAuthIdentityToken,
   shouldMirrorRefreshedOAuthCredential,
 } from "./oauth-identity.js";
+import { makeSeededRandom, maybe, randomAsciiString as randomString } from "./oauth-test-utils.js";
 import type { AuthProfileCredential } from "./types.js";
 
 // Direct unit + fuzz tests for the cross-agent credential-mirroring identity
@@ -177,30 +178,6 @@ describe("isSameOAuthIdentity", () => {
 // Fuzz tests. Seeded Mulberry32 so the run is reproducible.
 // ---------------------------------------------------------------------------
 
-function makeSeededRandom(seed: number): () => number {
-  let t = seed >>> 0;
-  return () => {
-    t = (t + 0x6d2b79f5) >>> 0;
-    let r = t;
-    r = Math.imul(r ^ (r >>> 15), r | 1);
-    r ^= r + Math.imul(r ^ (r >>> 7), r | 61);
-    return ((r ^ (r >>> 14)) >>> 0) / 4294967296;
-  };
-}
-
-function randomString(rng: () => number, maxLen: number): string {
-  const len = Math.floor(rng() * maxLen);
-  const chars: string[] = [];
-  for (let i = 0; i < len; i += 1) {
-    chars.push(String.fromCodePoint(32 + Math.floor(rng() * 95))); // printable ASCII
-  }
-  return chars.join("");
-}
-
-function maybe<T>(rng: () => number, value: T): T | undefined {
-  return rng() < 0.5 ? value : undefined;
-}
-
 describe("isSafeToCopyOAuthIdentity (unified copy gate, used for mirror and adopt)", () => {
   describe("positive matches", () => {
     it("accepts matching accountIds", () => {
@@ -479,30 +456,6 @@ describe("shouldMirrorRefreshedOAuthCredential", () => {
 });
 
 describe("isSafeToCopyOAuthIdentity fuzz", () => {
-  function makeSeededRandom(seed: number): () => number {
-    let t = seed >>> 0;
-    return () => {
-      t = (t + 0x6d2b79f5) >>> 0;
-      let r = t;
-      r = Math.imul(r ^ (r >>> 15), r | 1);
-      r ^= r + Math.imul(r ^ (r >>> 7), r | 61);
-      return ((r ^ (r >>> 14)) >>> 0) / 4294967296;
-    };
-  }
-
-  function randomString(rng: () => number, maxLen: number): string {
-    const len = Math.floor(rng() * maxLen);
-    const chars: string[] = [];
-    for (let i = 0; i < len; i += 1) {
-      chars.push(String.fromCodePoint(32 + Math.floor(rng() * 95)));
-    }
-    return chars.join("");
-  }
-
-  function maybe<T>(rng: () => number, value: T): T | undefined {
-    return rng() < 0.5 ? value : undefined;
-  }
-
   it("is reflexive: share(a, a) is always true", () => {
     const rng = makeSeededRandom(0x0172_0417);
     for (let i = 0; i < 1000; i += 1) {
diff --git a/src/agents/auth-profiles/oauth-refresh-error.test.ts b/src/agents/auth-profiles/oauth-refresh-error.test.ts
index ed5e939c1ba..fbb968ab494 100644
--- a/src/agents/auth-profiles/oauth-refresh-error.test.ts
+++ b/src/agents/auth-profiles/oauth-refresh-error.test.ts
@@ -1,4 +1,9 @@
 import { describe, expect, it } from "vitest";
+import {
+  makeSeededRandom,
+  randomAsciiString as randomJunk,
+  randomlyCased,
+} from "./oauth-test-utils.js";
 import { isRefreshTokenReusedError } from "./oauth.js";
 
 // Direct tests for the refresh_token_reused classifier. This is the gate that
@@ -94,33 +99,6 @@ describe("isRefreshTokenReusedError", () => {
   });
 
   describe("fuzz: random noisy messages", () => {
-    function makeSeededRandom(seed: number): () => number {
-      let t = seed >>> 0;
-      return () => {
-        t = (t + 0x6d2b79f5) >>> 0;
-        let r = t;
-        r = Math.imul(r ^ (r >>> 15), r | 1);
-        r ^= r + Math.imul(r ^ (r >>> 7), r | 61);
-        return ((r ^ (r >>> 14)) >>> 0) / 4294967296;
-      };
-    }
-
-    function randomJunk(rng: () => number, maxLen: number): string {
-      const len = Math.floor(rng() * maxLen);
-      const chars: string[] = [];
-      for (let i = 0; i < len; i += 1) {
-        chars.push(String.fromCodePoint(32 + Math.floor(rng() * 95)));
-      }
-      return chars.join("");
-    }
-
-    function randomlyCased(s: string, rng: () => number): string {
-      return s
-        .split("")
-        .map((c) => (rng() < 0.5 ? c.toUpperCase() : c.toLowerCase()))
-        .join("");
-    }
-
     it("always detects the marker when embedded at random positions with noise", () => {
       const rng = makeSeededRandom(0xabad1dea);
       const markers = [
diff --git a/src/agents/auth-profiles/oauth-test-utils.ts b/src/agents/auth-profiles/oauth-test-utils.ts
index 55204bb6d99..74b0f8ac44d 100644
--- a/src/agents/auth-profiles/oauth-test-utils.ts
+++ b/src/agents/auth-profiles/oauth-test-utils.ts
@@ -52,3 +52,34 @@ export function createExpiredOauthStore(params: {
     },
   };
 }
+
+export function makeSeededRandom(seed: number): () => number {
+  let state = seed >>> 0;
+  return () => {
+    state = (state + 0x6d2b79f5) >>> 0;
+    let value = state;
+    value = Math.imul(value ^ (value >>> 15), value | 1);
+    value ^= value + Math.imul(value ^ (value >>> 7), value | 61);
+    return ((value ^ (value >>> 14)) >>> 0) / 4294967296;
+  };
+}
+
+export function randomAsciiString(rng: () => number, maxLen: number): string {
+  const len = Math.floor(rng() * maxLen);
+  const chars: string[] = [];
+  for (let index = 0; index < len; index += 1) {
+    chars.push(String.fromCodePoint(32 + Math.floor(rng() * 95)));
+  }
+  return chars.join("");
+}
+
+export function maybe<T>(rng: () => number, value: T): T | undefined {
+  return rng() < 0.5 ? value : undefined;
+}
+
+export function randomlyCased(value: string, rng: () => number): string {
+  return value
+    .split("")
+    .map((char) => (rng() < 0.5 ? char.toUpperCase() : char.toLowerCase()))
+    .join("");
+}