diff --git a/src/codex/auth-api.ts b/src/codex/auth-api.ts
index 043df28286..7f8524456c 100644
--- a/src/codex/auth-api.ts
+++ b/src/codex/auth-api.ts
@@ -43,7 +43,13 @@ import {
   parseAccountPoolStrategy,
   parseAccountPriority,
 } from "./pool-rotation";
-import { checkAccountIdCollision, getMainChatgptAccountId, readCodexTokens, readCodexTokensResult } from "./auth-collision";
+import {
+  checkAccountIdCollision,
+  checkManualImportCollision,
+  getMainChatgptAccountId,
+  readCodexTokens,
+  readCodexTokensResult,
+} from "./auth-collision";
 export { checkAccountIdCollision, getMainChatgptAccountId } from "./auth-collision";
 export { clearAccountNeedsReauth, isAccountNeedsReauth, markAccountNeedsReauth } from "./account-runtime-state";
 import { clearAccountNeedsReauth, isAccountNeedsReauth, markAccountNeedsReauth } from "./account-runtime-state";
@@ -67,7 +73,7 @@ export {
   setAccountQuotaFromParsed,
   updateAccountQuota,
 } from "./quota";
-import { extractAccountId, decodeJwtPayload } from "../oauth/chatgpt";
+import { extractAccountId, decodeJwtPayload, extractEmail } from "../oauth/chatgpt";
 import { getMainAccountPlan, MAIN_CODEX_ACCOUNT_ID, setMainAccountPlan } from "./main-account";
 import { captureConfigGeneration, registerStateSweepAfterTick } from "../lib/state-store-sweeper";
 import { reconcileLiveStateStores } from "../lib/state-store-registrations";
@@ -1226,9 +1232,13 @@ export async function handleCodexAuthAPI(
     const runtimeConfig = getRuntimeConfig(config);
     const preflightConflict = codexAccountPersistenceConflict(runtimeConfig, body.id, "create");
     if (preflightConflict) return jsonResponse({ error: preflightConflict }, 400);
-    // 1.1: Duplicate check is scoped by personal vs workspace plan bucket.
+    // Manual-import identity must come from the token, not request-controlled metadata.
     const derivedAccountId = extractAccountId(undefined, body.accessToken) ?? body.chatgptAccountId;
-    const collision = checkAccountIdCollision(derivedAccountId, body.email, body.plan);
+    const derivedEmail = extractEmail(undefined, body.accessToken);
+    if (!derivedEmail) {
+      return jsonResponse({ error: "Access token does not contain an email claim" }, 400);
+    }
+    const collision = checkManualImportCollision(derivedAccountId);
     if (collision.collision) {
       return jsonResponse({ error: collision.reason }, 400);
     }
@@ -1249,7 +1259,7 @@ export async function handleCodexAuthAPI(
     markCodexAccountValidated(body.id, warmup.validatedAt);
     clearAccountNeedsReauth(body.id);
     const accounts = latestConfig.codexAccounts ?? [];
-    accounts.push(withCodexAccountLogLabel({ id: body.id, email: body.email, plan: body.plan, isMain: false }, accounts));
+    accounts.push(withCodexAccountLogLabel({ id: body.id, email: derivedEmail, plan: body.plan, isMain: false }, accounts));
     latestConfig.codexAccounts = accounts;
     saveRuntimeConfig(config, latestConfig);
     reconcileLiveStateStores();
diff --git a/src/codex/auth-collision.ts b/src/codex/auth-collision.ts
index a7d10e7c97..93fdf86bbd 100644
--- a/src/codex/auth-collision.ts
+++ b/src/codex/auth-collision.ts
@@ -105,3 +105,18 @@ export function checkAccountIdCollision(
   }
   return { collision: false };
 }
+
+// Manual imports do not have provider-verified email or plan metadata, so they cannot safely use
+// those fields to distinguish members that share an account id.
+export function checkManualImportCollision(
+  chatgptAccountId: string,
+): { collision: true; reason: string } | { collision: false } {
+  for (const account of loadConfig().codexAccounts ?? []) {
+    if (!isSelectableCodexPoolAccount(account)) continue;
+    const cred = getCodexAccountCredential(account.id);
+    if (cred?.chatgptAccountId === chatgptAccountId) {
+      return { collision: true, reason: `Account is already in the pool (${account.id}).` };
+    }
+  }
+  return { collision: false };
+}
diff --git a/tests/codex-auth-api.test.ts b/tests/codex-auth-api.test.ts
index 661309e74d..3ebc2ed302 100644
--- a/tests/codex-auth-api.test.ts
+++ b/tests/codex-auth-api.test.ts
@@ -88,11 +88,22 @@ function enableManualImport(): void {
   process.env[MANUAL_IMPORT_ENV] = "1";
 }
 
+function manualAccessToken(
+  email = "manual-test@example.test",
+  chatgptAccountId = "acct-manual-test",
+): string {
+  const payload = Buffer.from(JSON.stringify({
+    email,
+    chatgpt_account_id: chatgptAccountId,
+  })).toString("base64url");
+  return `header.${payload}.signature`;
+}
+
 function manualImportBody(overrides: Record<string, unknown> = {}): Record<string, unknown> {
   return {
     id: "manual-test",
     email: "manual-test@example.test",
-    accessToken: "access-manual-test",
+    accessToken: manualAccessToken(),
     refreshToken: "refresh-manual-test",
     chatgptAccountId: "acct-manual-test",
     ...overrides,
@@ -2239,7 +2250,7 @@ describe("codex-auth API", () => {
     expect(config.codexAccounts?.map(a => a.id)).toEqual(["manual-enabled"]);
     expect(config.codexAccounts?.[0]?.logLabel).toMatch(CODEX_ACCOUNT_LOG_LABEL_RE);
     expect(getCodexAccountCredential("manual-enabled")).toMatchObject({
-      accessToken: "access-manual-test",
+      accessToken: expect.stringMatching(/^header\./),
       refreshToken: "refresh-manual-test",
       chatgptAccountId: "acct-manual-test",
     });
@@ -2248,6 +2259,38 @@ describe("codex-auth API", () => {
     expect(warmup.calls()).toBe(1);
   });
 
+  test("POST /api/codex-auth/accounts uses token email to reject a changed-email duplicate", async () => {
+    enableManualImport();
+    mockCodexWarmupSuccess();
+    const config = makeConfig();
+    const firstBody = manualImportBody({ id: "manual-original" });
+    const firstRequest = new Request("http://localhost/api/codex-auth/accounts", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(firstBody),
+    });
+    expect((await handleCodexAuthAPI(firstRequest, new URL(firstRequest.url), config))!.status).toBe(200);
+
+    const duplicateRequest = new Request("http://localhost/api/codex-auth/accounts", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(manualImportBody({
+        id: "manual-copy",
+        email: "changed@example.test",
+        plan: "business",
+      })),
+    });
+    const duplicateResponse = await handleCodexAuthAPI(duplicateRequest, new URL(duplicateRequest.url), config);
+
+    expect(duplicateResponse!.status).toBe(400);
+    expect(await duplicateResponse!.json()).toMatchObject({
+      error: "Account is already in the pool (manual-original).",
+    });
+    expect(config.codexAccounts).toHaveLength(1);
+    expect(config.codexAccounts?.[0]?.email).toBe("manual-test@example.test");
+    expect(getCodexAccountCredential("manual-copy")).toBeNull();
+  });
+
   test("POST /api/codex-auth/accounts allows a pool account matching the main login", async () => {
     enableManualImport();
     mockCodexWarmupSuccess();
@@ -2263,6 +2306,7 @@ describe("codex-auth API", () => {
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify(manualImportBody({
         id: "manual-main-match",
+        accessToken: manualAccessToken("manual-test@example.test", "acct-main-login"),
         chatgptAccountId: "acct-main-login",
       })),
     });